Introduction
In the words of Mercer Rang, “children are not small adults.” Injuries in skeletally immature patients differ from those seen in adults because pediatric and adolescent skeletons are different in size, biomechanics, and physiology. Because of these factors, the clinician will see unique patterns of injury in pediatric and adolescent patients. Consideration of these differences will improve the diagnosis and treatment of injuries in the pediatric patient.
Epidemiology of Youth Sports
The popularity of youth sports continues to grow, and increasing participation of children at younger ages is being seen. Approximately 30 to 44 million preadolescents and adolescents are involved in organized sports, and an estimated 7.6 million students are involved in high school athletics. This participation is beneficial to the overall health of these children but is not without risk. Previous surveys estimated the annual number of injuries resulting from participation in sports and recreational activities to be 4,379,000; of these, 1,363,000 were classified as serious (i.e., requiring hospitalization, surgical treatment, missed school, or a half day or more in bed). A recent analysis of high school athletes demonstrated an estimated 446,715 severe injuries involving the knee (29.0%), ankle (12.3%), and shoulder (10.9%) most commonly. Of these injuries, 36% were fractures. Slightly more than half of the severe sports injuries resulted in medical disqualification for the season, and approximately a quarter of the injuries required surgical intervention.
In a separate study, Swenson and collegues found an incidence of 10% fractures in high school athletes, and an increased proportion of fractures were inversely associated with maturity of the player. Fracture rates were highest in football, ice hockey, and lacrosse, and the hand/finger (32.1%), lower leg (10.1%), and wrist (9.5%) were affected most commonly.
Influence of Gender
Enacted in 1972, Title IX legislation was designed to increase participation of females in sports, which it has done. The increase in female sports participation has brought a disproportionate increase in female injuries, and in gender comparable sports, girls have a higher injury rate than boys. In sports that involve running and cutting, jumping, and landing, females have been shown to sustain higher rates of knee injuries than males. ∗
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Moreover, Frisch and collegues also found an association with sports injury and previous injury between the two genders, but highlighted that girls were more likely to sustain an injury in team sports compared with boys in racquet sports. Although they found no difference in the severity of sports injuries between genders, they did find an increased incidence of foot and ankle injuries in girls. Girls may have a higher risk of injury; thus this gender is often targeted by injury prevention programs to help reduce sports injury risk, although some recent research has questioned the effectiveness of some of these programs.Anatomy of the Skeletally Immature Joint and Ligaments
The physis is specialized cartilaginous tissue interposed between the metaphysis and the epiphysis in the long bones of children. The physis is a multilayered structure that physiologically transcends zones of cartilaginous matrix to complete ossification, resulting in increased length of the bone. Both sides of the physis are active in the process of bone formation: proximally (intramembranous), resulting in both cylinderization and funnelization, and distally, directly beneath the articular cartilage layer (endochondral formation), resulting in hemispherization. The open physes are easily seen on magnetic resonance imaging (MRI), as shown in the sagittal view of the knee ( Fig. 21-1 ). The region of greatest risk for injury is the area between the hypertrophic cells and the region of calcification. The physeal cartilage adds unique biomechanical character to the pediatric skeleton. This tissue is more viscoelastic than bone; thus it is more likely to fail in traumatic situations, particularly in rotation. In many types of pediatric injuries, the physeal cartilage will fail before the surrounding ligaments or osseous tissues.
Pediatric joints have a higher percentage of cartilage than adult joints because of the physis and nonossified regions of the epiphysis, and this may explain the higher incidence of physeal and apophyseal fractures in the skeletally immature joints, such as the knee. ∗
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Although occasionally seen in adults, tibial eminence avulsion injuries are relatively rare compared with midsubstance anterior cruciate ligament (ACL) injuries. Tibial eminence avulsion injuries are commonly seen in skeletally immature patients and may represent the fact that the epiphyseal region of the tibial plateau is composed of a relatively high percentage of cartilage compared with the adult knee ( Fig. 21-2 ). Avulsion injuries of the posterior cruciate ligament (PCL) are also seen in skeletally immature patients. ††
Pediatric bone is more flexible and less brittle than adult bone because of its decreased density. These different mechanical properties are evidenced by the unique fracture types seen in children, including buckle, bowing, and greenstick deformities.
Many studies of pediatric trauma have supported the concept that the physis is weaker than ligaments and that the physeal structure is more likely to fail than ligaments, especially under conditions of high-energy transfer. The weakest area of the physis is thought to be the zone of hypertrophy, although fractures can occur in other regions. Examples of fractures of this type include a medial epicondylar avulsion of the elbow, triplane fractures of the distal tibia, and traumatic displacement of the proximal femoral physis. These fractures are complicated by the susceptibility to growth disturbance after an injury, especially when physeal fractures are involved. Although these fracture patterns are relatively common in skeletally immature athletes, ligamentous injuries similar to those in adults can still occur in the skeletally immature.
Biomechanical studies of the physis and ligaments have shown that failure modes are related to the magnitude and rate of load application. Ligaments are more likely to fail at lower rates of load application, whereas physeal fractures are more likely to occur at higher rates of load application. The cartilaginous physes are approximately one third as strong as their associated ligaments, and this difference becomes more disparate during growth spurts. As the child becomes older, the physis becomes stiffer and may make the incidence of a ligamentous injury more likely than a physeal injury.
Principles of Examination and Treatment of the Pediatric and Adolescent Patient
The principles of examination (for the pediatric patient) are similar to those used for adults. Establishing trust and rapport with the child during the history (taking) will make the examination of a painful injury easier. It is often best to start away from the most painful site and work toward the injured area. Although serious injuries are rare, especially in smaller children, physeal and ligamentous injuries should always be considered. Thus knowledge of physeal anatomy and the specific location of symptoms is needed to accurately diagnose these injuries. Often, the pediatric examination may be easier due to smaller joints and very distinct ligamentous endpoints. Some children naturally have increased laxity; therefore comparison with the contralateral side is important. With knee examinations, Lachman test excursions may be easier to detect and quantify compared with adult patients. Specialized pediatric equipment, such as a KT-1000 Junior (MEDmetric, San Diego, California), may be helpful for these examinations. Historically, a complete examination was not thought to be possible without the use of sedation or anesthesia in some injuries. Because of the availability of current imaging technology, specifically MRI and computed tomography (CT), the need for examination under anesthesia is rarely necessary anymore.
Treating pediatric and adolescent patients is less complicated than treating adults in some respects. Children’s injuries tend to heal more quickly and are less apt to develop arthrofibrosis than adults. Younger patients generally require a shorter period of immobilization because of rapid healing. Adolescents and older patients with serious knee and other joint injuries are usually mobilized early to reduce the risk of arthrofibrosis. When arthrofibrosis does occur, in the authors’ experience, it tends to respond better to nonoperative measures in children than in adults. Thus the treating physician may observe younger patients somewhat longer before considering surgical intervention in a stiff joint. In cases of severely ankylosed knees, Cole and Ehrlich described a successful approach for functional restoration in children. When manipulation is considered, caution is warranted because of the risk of physeal injury.
Diagnostic Imaging
Diagnostic imaging is useful for serious injuries in young patients. Plain radiographs can identify osseous injuries, although they are inadequate for the evaluation of certain acute injuries such as a knee with hemarthrosis. Comparison views can be invaluable aids when physeal irregularities are being assessed. MRI seems to have replaced stress and nonstress radiographs in differentiating a physeal injury from a ligamentous injury.
MRI has been assessed as a mode of evaluation for the sports injury, especially in the knee. Imaging in children younger than 5 to 7 years may be limited because of the small size of the knee. The indications for MRI in children are still being established, although many clinicians rely on MRI for diagnosis. MRI is a very sensitive tool for the evaluation of physeal, osseous, and ligamentous structures. ∗
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One significant limitation of MRI in skeletally immature patients is in the evaluation of meniscal tears: interpretation of meniscal tissue intrasubstance signal variation can be difficult because these younger patients frequently have variations in the meniscal signal, particularly in the posterolateral horn of the meniscus, that can suggest an injury in the setting of normal meniscal tissue. Kocher and colleagues and others have questioned the effectiveness and necessity of MRI for the routine evaluation of knee injuries in children, although imaging studies may help identify occult fracture or ligamentous injuries.With regard to the rate of injuries found with the use of MRI, a recent study on the knee demonstrated that preadolescent patients with an effusion had patellar dislocations (36%), ACL tears (22%), and isolated meniscal tears (15%). Adolescent patients had slightly different rates of injury with knee effusion: ACL tears (40%), patellar dislocations (28%), and isolated meniscal tears (13%).
Sport Injuries to the Upper Extremity
Shoulder Injuries
Shoulder pain is a common complaint among young athletes who perform overhead activities such as pitching, throwing, and swimming. The pain is usually located anteriorly, but lateral and posterior pain is not uncommon. The pain is typically described as a dull ache, which occurs when they are performing their activities.
Examination of the shoulder consists of range-of-motion testing, a thorough neuromuscular assessment (particularly strength of the rotator cuff muscles), and specific diagnostic tests. Limits in range of motion may signal an acute injury, fracture, or dislocation. Occasionally, passive or active motion may help the child localize the pain. Weakness in a specific nerve distribution may indicate a cervical cause as the pain generator (either by radiculopathy or muscle imbalance). Weakness of the rotator cuff muscles will often lead to shoulder pain, especially with background joint laxity, due to excessive motion of the humerus in the glenohumeral joint. A differential diagnosis can usually be formulated after acquiring the history and performing the initial physical examination.
The sensitivity and specificity of clinical tests for superior labrum anterior/posterior (SLAP) lesions may be limited when used individually, but the diagnostic value may improve when several tests are used. More recent studies have questioned the value of these tests. In the assessment of SLAP tears, the O’Brien test, Biceps Load II test, Dynamic Labral Shear test (O’Driscoll test), Speed test, and the Labral Tension test have been recently assessed for predictability with very low yield to identify this injury pattern. Once the physical examination is complete, then confirmatory diagnostic testing may be performed.
Diagnostic testing involves plain radiographs of the shoulder that include anteroposterior (AP) and lateral projections. Depending on the differential diagnoses involved this might include an axillary view, Velpeau axillary view, scapular Y view, AP shoulder with humerus internal and external rotation, Grashey view (true glenoid AP), or a serendipity view of the clavicle. After plain radiographs, there may be an indication for obtaining either MRI or CT scans. CT scans would be appropriate if a more detailed reconstruction of the bony architecture is required; however, for soft tissue injuries that cannot be evaluated by either a CT scan or a plain film, MRI is the diagnostic modality of choice.
Shoulder Dislocation and Instability
Shoulder injuries in the pediatric athlete are often due to instability, especially in sports with overhead movements, such as swimming and baseball. Repeated overhead motions can stretch the joint capsule and allow excessive motion of the humeral head. Acute shoulder dislocation may result in stretching of the joint capsule or other glenohumeral joint problems.
Historically, individuals 11 to 20 years old demonstrate approximately the same incidence of glenohumeral joint dislocation as their more mature counterparts 51 to 60 years old. However, this younger cohort may have more than a 90% chance of recurrent dislocation without intervention. Pediatric dislocations are believed to stretch the capsule more than adult dislocations and diminish the capsule’s ability to provide the support needed for proper articulation. Surgical treatment for instability is generally successful and is often recommended, but the rate of recurrence in the adolescent population after surgical repair may be as high as 21%. The results of multidirectional instability surgery may be similar to pure anterior instability, with a recurrence of about 24% after surgical intervention in a young adult population.
Physical examination and diagnostic testing may demonstrate the concomitant injuries of a Bankart lesion (anterior bony or labral tear), SLAP tear, Kim lesions (posterior sublabral pathology), Hill–Sachs (posterolateral humeral head compression fracture) lesions, rotator cuff muscle tears, and subscapularis or lesser tubercle avulsions. Recent evidence in the pediatric population suggests that preoperative evaluation and MRI underestimate the full extent of labral pathology seen at the time of arthroscopy.
Treatment
In the acute care setting, dislocated shoulders should undergo closed reduction as quickly as possible. As previously discussed, children tend not to have favorable outcomes after shoulder dislocation: only 10% have success without surgical intervention.
Surgical treatment for shoulder laxity, in the form of anterior, posterior, or multidirectional instability, may be delayed until a several month period of physical therapy and activity modification has been attempted without significant clinical improvement. Should the child fail conservative management or have secondary laxity to a shoulder dislocation, at least a capsulorraphy may be required to create a stable glenohumeral joint. Other surgical treatments can be added à la carte depending on the specific pathology present in each case. Even with surgical treatment, recurrent dislocation may occur at higher rates in skeletally immature patients. Recognition of osseous abnormality in the humeral head and/or glenoid may be an important factor associated with recurrent instability after surgery.
The trend recently has been to perform these operations as arthroscopic procedures rather than open ones, and this remains an ongoing area of research and controversy. Depending on the work that is required, some authors have reported that open surgery had better outcomes for creating a stable shoulder than arthroscopic surgery in mature patients. With improving surgical experience and improved technology, some recent literature suggests that arthroscopic surgery can have at least equal outcomes, although most studies have been done on older patient populations.
Suture anchors and plication of the redundant capsule appear to have the best outcomes from an arthroscopic approach. An open capsular shift through a standard deltopectoral approach remains the technique with the greatest reproducibility and results in the most postoperative stability. Outcomes for open procedures result in reported recurrent dislocation rates of 2.7% to 3.5% in adults as compared with arthroscopic results that range from 3.4% to 40%, depending on the study. Bottoni and colleagues conducted a randomized clinical trial of 66 patients and found comparable clinical outcomes between open and arthroscopic techniques for treating recurrent anterior shoulder instability. However, Lenters and colleagues published a systematic review and meta-analysis of reports comparing open and arthroscopic repairs for recurrent anterior shoulder dislocation and found that arthroscopic repairs were associated with significantly higher rates of recurrent instability, recurrent dislocation, and reoperation.
If the patient has bony defects in the glenoid or a Hill–Sachs lesion, these defects may be addressed by one of several procedures. These procedures include the Bristow procedure, the Latarjet procedure, and iliac crest bone grafting. To reduce the morbidity associated with autografting, recent techniques have used allograft from the femoral head and the distal tibia. These procedures are typically performed through an anterior open approach to the shoulder. Current techniques for arthroscopic Latarjet procedures have been developed but are technically demanding. Complications associated with the Latarjet procedure may be higher than those for arthroscopic procedures and include infection, neurologic injury, and recurrent dislocation.
Recent research is also studying the impact of humeral head defects, which, in some cases, may be a significant problem. Hill–Sachs deformities can also contribute to significant shoulder instability that cannot be addressed with a more traditional soft tissue and anterior Bankart repair.
Techniques have been developed to prevent this posterior humeral defect from engaging the glenoid, which can cause shoulder disability and recurrent dislocation. These approaches address the humeral head defect by treating the osseous defects with bone supplementation. Techniques include allografting, humeral osteotomy, humeroplasty, and resurfacing arthroplasty. Soft tissue techniques have also been used and may include mobilizing the posterior aspect of the capsule and the infraspinatus tendon to fill the defect. The “Hill–Sachs remplissage” is amenable to an arthroscopic approach. In cases of a traditional Bankart lesion combined with a significant Hill–Sachs deformity, this remplissage procedure may be combined with a Bankart repair. The presence of a significant glenoid defect may be a contraindication for this procedure, and other approaches may be necessary. Treatment of these defects continues to evolve.
Future research comparing the outcomes of different osseous-based procedures will continue, and future arthroscopic techniques may eventually allow for correction of osseous and soft tissues deficits. A higher complication rate associated with these osseous procedures is a concern.
Overuse Injuries
Adams was the first to describe little leaguer’s shoulder in boys 9 to 15 years of age. In the original description, the pathology was believed to be consistent with osteochondrosis of the proximal humeral epiphysis secondary to “an abnormal whip-like action, which places a forceful repetitious traction strain on the shoulder joint.” Since that time, a biomechanical study has demonstrated that 12-year-old baseball pitchers are able to consistently create 215 N of shoulder distraction force (about 50% of body weight) at ball release and 18 Newton-meters of peak external rotation torque at the late arm-cocking phase. These forces, when consistently applied during the pitching motion of a young baseball player, are large enough to create deformation of the proximal physeal cartilage.
Cahill and associates and others jointly presented the concept that the symptomatic changes in the proximal physis of the humerus with repetitive baseball pitching were actually due to a stress fracture through the physeal plate. The first stage of this fracture is demonstrated by osteochondrosis, or epiphysiolysis, followed by widening of the physeal plate, and ultimately callus formation around the perichondral ring of LaCroix secondary to stripping of the periosteum. Advanced imaging techniques are consistent with biomechanical failure of the proximal humeral physis.
Stress fractures may occur along the entire shaft of the humerus, not just at the proximal growth plate. These metaphyseal and diaphyseal stress fractures are more likely to develop in adolescent overhead athletes, who have limited or no growth potential in their proximal humeral growth plate but who continue to have immature bone. The risk of development of this type of injury may also be increased by a concurrent period of rapid growth. An antecedent finding of stress fracture, or possibly a distinct entity, is humeral periostitis.
Little leaguer’s shoulder, humeral periostitis, and humeral stress fractures have overlapping signs and symptoms, and pain of the proximal humerus and shoulder is often aggravated by the specific overhead activity that caused the pain and relieved with activity modification. The most common radiographic finding in little leaguer’s shoulder is widening of the proximal humeral epiphysis. Other findings may be demineralization, sclerosis, or fragmentation of the proximal humeral metaphysis. Stress fractures and periostitis may require a bone scan or MRI for definitive diagnosis, although the authors prefer the use of MRI because it avoids the use of radiation and offers much greater anatomic detail.
Treatment
The treatment for little leaguer’s shoulder and stress fractures of the humerus is activity modification. Most often this involves rest and cessation of the offending activity for at least 4 weeks, followed by gradual resumption of pain-free activities over the next 4 to 8 weeks. Occasionally, physical therapy may be helpful for range of motion (in the form of teaching good throwing mechanics) and strengthening of the shoulder girdle musculature. If the child is not able to return to preinjury activity without pain, then the recommendation should be to stop that specific activity. This may mean cessation of the overhead sport or changing positions (on a baseball team) to one that is less demanding of the young athlete’s shoulder.
Impingement Syndrome and Os Acromiale
Although considered a disease process of the more mature athlete or sedentary adult, impingement syndrome may also occur in the young athlete. A painful shoulder that is aggravated by repetitive overhead activities characterizes this syndrome. The pathology is believed to be secondary to repetitive microtrauma from impingement of the watershed region of the supraspinatus tendon on the undersurface of the anterior edge of the acromion and the coracoacromial ligament.
The impingement sign described by Hawkins and Kennedy reproduces pain when the arm is “forcibly forward flexed (jamming the greater tuberosity against the antero-inferior surface of the acromion).” This can be done with either maximal forward elevation or elevation to 90° with internal rotation of the upper extremity. Often, the long head of the biceps may become involved in the inflammatory process and become symptomatic, although this problem is less common in the skeletally immature athlete.
Occasionally, the radiographs may demonstrate an “extra” bone at the acromion. The discovery of os acromiale may herald a different pathologic process that is similar to impingement syndrome in that the mesoacromion is actively depressed by the pull of the deltoid muscle, which causes impingement on the rotator cuff muscle and possibly the long head of the biceps tendon. Prospective and population studies have found approximately an 8% incidence of os acromiale in the population and in symptomatic patients given diagnoses of impingement syndrome or rotator cuff pathology. Axillary radiographs are the best view for examining the acromion for residual preacromion, mesoacromion, or metaacromion ossification centers. It is important to understand normal growth and fusion of secondary ossification centers in the child athlete before a diagnosis of symptomatic residual os acromiale is made. Contralateral radiographs of the shoulder may aid in the diagnosis. At age 12 years, the metaacromion unites with the basiacromion and the remainder of the scapular spine. Between 15 and 18 years of age, the secondary centers start to ossify and may not coalesce to form the united acromion until age 25 years. Therefore axial MRI may prove beneficial in determining whether the os acromiale is indeed the source of pain because it will demonstrate marrow edema, osteophyte formation, and widening of the physis.
Treatment
Impingement syndrome is treated with physical therapy that focuses on range of motion, strengthening, and activity-specific training that is integral to treatment and later prevention of reinjury. Initial management should include activity modification in the form of rest, plus cryotherapeutic modalities and nonsteroidal antiinflammatory agents. If conservative management fails, then surgical treatment may be considered. The surgical treatment options for impingement continue to evolve in the adult patient population, and arthroscopic techniques for decompression are changing rapidly in this field. Impingement syndrome is quite rare in young athletes, and in the authors’ experience, surgical management is rarely indicated in these younger patients.
If symptomatic os acromiale is discovered, then nonsurgical management should be attempted initially and for at least 6 months. Again, this consists of activity modification and other therapeutic modalities including nonsteroidal antiinflammatory medicines. Successful surgical treatment may consist of arthroscopic excision of the anterior preacromion or mesoacromion fragment or open reduction and internal fixation with cannulated screw, Herbert screw, or tension band techniques.
Elbow Injuries
The young overhead athlete is vulnerable not only to shoulder injuries but also to traumatic and overuse elbow injuries. Injuries to the elbow are not limited to the overhead athlete, such as those engaged in throwing and swimming, but also include gymnasts, whose elbows, being weight-bearing joints during the sport, are also at risk. The elbow joint comprises three major articulations: radiocapitellar, ulnohumeral, and proximal radioulnar. Before understanding pathologic changes in the elbow, it is important to understand the normal ossification of the elbow, through the six secondary centers. All of the ossification centers except the medial and lateral epicondyles are intraarticular. Injuries of the immature elbow have a predilection for involving the weaker growth plates, as compared with the bony or ligamentous structures.
The physical examination of the young elbow is most often lead by the location of pain. Many of the structures involved in youth injuries are nearly subcutaneous, and the examination should include palpation of the medial epicondyle, olecranon, lateral epicondyle, and the radial head. Passive and active range of motion (i.e., flexion, extension, supination, and pronation) should be assessed, as well as varus and valgus stressing. Loss of motion, especially mild flexion contractures, occurs frequently. The elbow averages a clinical carrying angle of 7° of valgus alignment. Muscle strength and any neurologic deficits should be recorded.
Radiographic findings are based on the standard AP, lateral, and oblique films of the elbow and often require contralateral elbow films for comparison. From AP radiographs, one can measure the Baumann angle (the angle created at the bisection of the capitellar physeal line and a line perpendicular to the humeral shaft), which should be within 8° of the contralateral elbow. The lateral films should demonstrate a normal humerocapitellar angle of 30° to 40° of flexion. More importantly, a line drawn along the anterior humeral shaft should bisect the center of the capitellum. Any view should be evaluated for fractures or dislocations, especially widening of the growth plates.
MRI studies of asymptomatic high school baseball players have demonstrated asymmetric anterior band ulnar collateral ligament thickening, mild sublime tubercle/anteromedial facet edema, and posteromedial subchondral sclerosis of the ulnotrochlear articulation, including posteromedial ulnotrochlear osteophytes and ulnotrochlear chondromalacia.
Fleisig and colleagues estimated that valgus forces at the elbow reach 64 Newton-meters during late cocking and early acceleration phases of throwing, based on their biomechanic testing. Simultaneously, the compressive forces at the lateral radiocapitellar articulation, as the elbow arcs from 110° to 20° of flexion at velocities of 3000°/sec, may reach 500 N. The combination of these forces across the elbow joint may create a valgus extension overload that may become pathologic with repetitive throwing events. Valgus extension overload can result in most overhead sport–related injuries of the elbow because of the way the significant valgus loads, coupled with rapid elbow extension, produce tensile stress of the medial restraints, compression stress of the lateral compartment, and shear stress in the posterior compartment.
Medial elbow pain may represent an injury to the ulnar collateral ligament, flexor–pronator mass, medial epicondylar apophysis, or the ulnar nerve. In many cases of overuse elbow injuries, several of these injuries may coexist. Lateral elbow pain more likely represents an injury to the radial head or neck, lateral epicondylar apophysis, or capitellum. Posterior elbow pain usually represents an injury to the posteromedial tip of the olecranon or the trochlear and olecranon fossa.
Traumatic Elbow Injuries
Elbow Dislocations and Medial Epicondylar Fractures
Fractures of the medial epicondyle are more common than dislocations and account for approximately 10% of elbow fractures in children. Because of the physeal anatomy of the skeletally immature elbow, the ulnar collateral ligament and flexor muscles frequently avulse a fragment from the medial epicondyle. Elbow dislocations and fractures of the medial epicondyle are usually the result of falling with the forearm supinated and the elbow in full or partial extension Nearly 50% of medial epicondylar fractures are associated with dislocation of the elbow, and often the displaced fragment becomes trapped in the joint, interfering with closed reduction of the dislocated elbow ( Fig. 21-3 ).
Medial epicondylar fractures and dislocations of the elbow are frequently seen in young gymnasts. Isolated medial epicondylar fractures are occasionally seen in adolescent pitchers. These injuries typically occur during pitching and may be preceded by symptoms of medial epicondylitis. Both dislocations and overuse injuries can result in an ulnar collateral ligament injury.
Treatment
Evaluation and treatment of medial epicondylar elbow fractures continue to evolve. Radiographic analysis of fracture displacement has limitations, and more advanced imaging modalities may assist clinical decision making. Treatment of medial epicondylar fractures is controversial, especially for minimally displaced fractures. Nondisplaced fractures are typically treated with casting, but displaced fractures may require surgery. In athletes who put high demand on their elbows (e.g., throwers, gymnasts, and wrestlers), anatomic reduction of medial epicondylar fractures may be important for future athletic performance; however, current literature suggests no difference in outcomes between surgical and nonsurgical cohorts.
Evidence has shown that ulnar collateral ligament reconstructions do well in the adolescent population, but a recent study suggests that good results may be achieved with a direct repair in this younger population.
Overuse Elbow Injures
Overuse injuries of the immature elbow all fall under one name, Little Leaguer’s elbow. This term is used to represent almost any injury incurred during the play of any overhead activity, but most often it represents an injury to the medial aspect of the elbow. Klingele and Kocher described the various injuries that may be called Little Leaguer’s elbow, on the basis of the common etiology of repetitive microtrauma of the immature elbow.
Pain at the medial side of the elbow may be medial epicondyle apophysitis or an avulsion fracture. Radiographs will usually demonstrate physeal widening but may also demonstrate fragmentation of the ossification center. The elbow may appear to have a growth disturbance, represented by delayed ossification, or, contrarily, accelerated growth, marked by premature physeal closure. Occasionally, the physis is not the location of the pathology; instead, the injury may be to the ulnar collateral ligament or common flexor origin (golfer’s elbow in adults) or may be ulnar neuritis.
The lateral aspect of the elbow appears to demonstrate injuries involving the radiocapitellar joint rather than the lateral epicondyle (the source of tennis elbow). The capitellum may be the source of pain from osteochondrosis (Panner disease) or osteochondritis dissecans (OCD). It is important to differentiate between these two pathologic processes. The former occurs in younger children (<10 years) and is self-limited, and complete resolution is the norm after activity modification. The latter most often represents an osteochondral fracture in the older child or adolescent and often requires surgical intervention to achieve healing of the OCD and return to play.
If the capitellum is not the source of pain of the lateral elbow, then the radial head may be the cause. The radial head may also be subject to OCD lesions, which may be difficult to assess radiographically. The radial neck may be subject to deformation that can lead to poor elbow mechanics and pain.
Posterior elbow pain most often represents an injury to the olecranon apophysis, an avulsion fracture, or delay of apophyseal fusion. Comparison of contralateral films may be helpful. Other imaging options that can confirm the diagnosis include a bone scan or MRI, but the authors’ more recent experience with MRI has been positive. With valgus extension overload, the compression stress on the posteromedial olecranon can create osteophytes. The osteophytes may then lead to bony extension contracture; it is important to realize that the osteophytes are a by-product of the pathology.
On occasion, Little Leaguer’s elbow may include anterior elbow pain and pathology that is secondary to the valgus extension overload. This usually comes in the form of anterior-based capsular contractures that cause a flexion contracture of the elbow.
Treatment
Initial management of Little Leaguer’s elbow is conservative and nonsurgical, unless the diagnosis is that of a fracture. Activity restrictions, therapy, and change to another position that requires less throwing are all options that help with healing. Medial epicondylar fractures or olecranon stress fractures, for example, may require open reduction and internal fixation for predictable outcomes in some athletes. The other scenario that calls for initial management to be operative is the finding of loose bodies within the joint because the pain is unlikely to resolve without excision.
The initial nonoperative management, whether started for medial epicondyle apophysitis, an ulnar collateral ligament injury, or any of the other manifestations of valgus extension overload syndrome, is the same regimen independent of the diagnosis. The first step in management is cessation of provocative activities for at least 4 to 6 weeks, with concurrent cryotherapeutic and antiinflammatory modalities. Cessation of all throwing until the elbow is asymptomatic with reassessment of throwing mechanics and number of pitches thrown is essential. During the rest from throwing activities, a transition into physical therapy that begins with regaining motion and strengthening the shoulder girdle, scapular stabilizers, and rotator cuff musculature should be started. Poor mechanics of the shoulder may increase the pathologic stresses across the elbow during the throwing motion. Once the symptoms of pain begin to wane with this physical therapy program, strengthening of the medial flexor–pronator muscles may commence. Finally, with complete resolution of pain, a controlled regimen of activity-specific exercises, plyometrics, and an interval throwing program is undertaken before return to competitive activities.
It is important to realize that nonoperative treatment of ulnar collateral ligament injuries is generally indicated in nonthrowing athletes, after which, they often have good outcomes; in contrast, patients who are involved in high-demand throwing sports do not respond as well to nonoperative management. Therefore differentiating between a true ligament tear and incompetency versus medial epicondyle apophysitis or avulsion is important. If, indeed, the child is given a diagnosis of a tear in the ulnar collateral ligament and still wishes to continue competitive pitching, then the treatment of choice after failed conservative management may be ulnar collateral ligament reconstruction.
The best treatment for many of these injuries may be prevention. This means teaching children good mechanics and, in throwing sports, limiting the number of pitches. Current recommendations for the number of pitches per game differ with the age of the child: 7- to 8-year-old athletes are limited to 50 pitches, 9- to 10-year-old athletes are limited to 75 pitches, 11- to 12-year-old athletes are limited to 85 pitches, 13- to 16-year-old athletes are limited to 95 pitches, and 17- to 18-year-old athletes are limited to 105 pitches.
Lateral elbow pain is treated in the same manner as medial and posterior elbow pain. Nonoperative management with activity modifications and physical therapy directed in a similar fashion to the medial elbow should be attempted first, and the focus should initially be on the shoulder, followed, instead, by the lateral forearm extensor mass. Failure of this regimen may require arthroscopic débridement, chondroplasty, microfracture, or removal of loose bodies, as needed, especially if an OCD lesion with a loose fragment is the cause.
Wrist Injuries
Wrist pain in an overhead-throwing athlete is not as common as that of pain in the elbow or shoulder. In contrast to throwers, gymnasts have a much higher incidence of wrist pathology. Chronic wrist pain is estimated to affect nearly 80% of all child gymnasts at one time or another because of the way that the wrist becomes a weight-bearing joint. The younger the child begins training for gymnastics, the more likely that the growth plates surrounding the wrist are potential sites of injury.
Other children at risk of developing wrist pain are those using bats, rackets, or their hands to strike a ball. Most often, these injuries are considered acute and may involve fractures of the carpal bones, especially the scaphoid and hook of the hamate. Repetitive striking of the volleyball has been implicated as a potential cause of Keinböck avascular necrosis of the lunate.
Examination of the wrist should involve a thorough neuromuscular assessment, evaluation of range of motion, and location of the pain. Pain in the anatomic snuff box may indicate a scaphoid fracture, pain over the radial styloid is more consistent with distal radial pathology, and pain near the ulnar styloid may represent a tear of the triangular fibrocartilage complex (TFCC).
Radiographs should consist of AP and lateral wrist or hand views, as well as specialized views depending on the differential diagnosis; these may include a carpal tunnel view to evaluate the hook of the hamate and contralateral wrist views to help assess growth plate injuries. Depending on the differential diagnosis, MRI may be performed to exclude nondisplaced fractures or osteonecrosis of the carpals. Furthermore, MRI or a CT scan, depending on the information desired, may be obtained to better evaluate wrist pathology. Often, TFCC tears and chondral lesions may be missed even on MRI.
Gymnast Wrist
Gymnast wrist has been defined as chronic radial pain with the following radiographic findings: growth plate widening with “haziness” or ill-defined borders, metaphyseal cyst formation, and epiphyseal beaking. Some evidence has shown that these changes may result in premature physeal closure of the distal radius. Albanese and colleagues further postulated through a summary of previous studies that some repetitive compression loading of a physis may result in increased growth, whereas too much repetitive compression loading will inhibit growth and possibly result in physeal arrest.
A recent MRI study demonstrated that not all gymnasts sustain classic gymnast wrist. Dwek and colleagues did find chronic physeal changes consistent with gymnast wrist, but more importantly, they discovered focal lunate osteochondral defects, TFCC tears, scapholunate ligament tears, and metacarpal head flattening and necrosis in the group of adolescent teenagers they studied.
Scaphoid fractures have also been reported to occur in gymnasts, and surgical treatment may be necessary in some cases.
Treatment
The mainstay of treatment of gymnast wrist is activity modification, specifically cessation of wrist weight-bearing activities. Physical therapy with cryotherapy and antiinflammatory management may be undertaken during this period of rest, in an effort to accelerate recovery time and ensure prevention of reinjury. Children should not be allowed to return to competitive activities unless they are pain-free and are able to remain that way during activity.
If nonoperative management fails, then a few operative choices may be considered. Depending on the preoperative findings, an ulnar shortening osteotomy may be performed if positive ulnar variance is found; a chondroplasty or arthroscopic débridement of loose bodies or synovitis may also be done to alleviate symptoms. The results of operative management are good in terms of pain relief, but oftentimes the symptoms will return with competitive activities.
Triangular Fibrocartilage Complex Injuries and Ulnar-Sided Wrist Pain
Gymnasts and other athletes are also prone to ligamentous injuries and injuries to the TFCC due to repetitive weight-bearing on the wrist. Other young athletes (such as those participating in basketball, lacrosse, or baseball) may also be susceptible to these soft tissue injuries. Tears of the TFCC may result in further damage to the adjacent articular cartilage if the offending activity is not stopped. Chondromalacia has been found to involve the ulnolunate, ulnotriquetral, and radiocarpal joints.
A recent study on ulnar-sided wrist pain demonstrated many possible causes in the athletic population. Fractures of the ulnar styloid, hamate, pisiform, and base of the fifth metacarpal may be present; in addition, soft tissue injuries consistent with ulnar impaction syndrome, extensor carpi ulnaris disorder, or even flexor carpi ulnaris disorders may be causes.
Treatment
Initial management of this condition is activity modification, antiinflammatory medications, cryotherapy, and physical therapy. If this initial effort fails to produce significant improvement of the symptoms after 4 to 6 weeks, then immobilization may be used. The wrist is casted or braced depending on the child, and complete cessation of gymnastic activities is ordered for another 6 weeks. If pain continues, then the next step is to obtain an MRI to better prepare for surgical treatment. Operative treatment consists of arthroscopic débridement and possible repair of the TFCC tear. Surgical treatment in the athletic population appears to be predictably good, but perhaps not excellent, in that return to activities occurs at approximately 3 months.
Pelvic and Hip Injuries
Apophyseal Avulsions of the Pelvis
Among the acute injuries of the pelvic region, apophyseal avulsions are the most common. An apophysis is the point on the bone at which a muscle attaches, and occasionally the muscle wholly or partially dislodges a fragment of bone. Apophyseal avulsions are usually caused by a sudden or violent muscle contraction. Common sites for apophyseal avulsions in pediatric and adolescent athletes include the ischial tuberosity (hamstrings), pubis (adductors), lesser trochanter (iliopsoas), anterior superior iliac spine (tensor fascia lata), anterior inferior iliac spine (rectus femoris), and the iliac crest (gluteus medius) ( Fig. 21-4 ). Although certain apophyseal avulsions have traditionally been uncommon in the pediatric population, rates of this injury have been increasing in recent years, presumably because of the increase in competitive sports involvement and improvements in imaging techniques. Sudden or violent muscle activity is typically seen in sports such as gymnastics, tackle football, sprinting, field events in track and field, soccer, and any activity involving quick or powerful muscle contractions.
The athlete typically reports having felt a sudden “pop” or “letting go” near the site of the injury, followed immediately by considerable pain and loss of function. In many respects, these injuries mimic muscle strains and are often initially misdiagnosed as such. Careful physical examination differentiates muscle strains from apophyseal avulsions. The initial evaluation should include a history of the activity immediately preceding the injury and palpation of the painful area. Functional testing should include manual muscle testing of the suspected muscle group, and attention should be paid to increases in pain or significant weakness. Point tenderness is demonstrated, and pain may also be referred to another region of the hip. Walking with a limp indicates a more severe injury.
Initial treatment for apophyseal avulsions includes rest, ice, compression, and elevation (RICE). The athlete should be fitted with crutches to limit weight-bearing and then referred to a physician for a more complete medical evaluation. Radiographic evaluation confirms the diagnosis; however, this injury can be difficult to visualize because of its size and location. Definitive treatment is usually nonoperative and includes rest, ice, and pain management, followed by a gradual return to activity concomitant with a general strength and flexibility program. Surgical intervention is rarely required because most injuries involve minimal displacement of the avulsed fragment. However, recent literature suggests that surgery may be necessary to ensure the best outcomes for some of these injuries, especially for large displaced fragments.
Knee Injuries
Physeal Fractures of the Knee
Physeal fractures of the knee are commonly associated with youth sports and involve either the distal femoral or proximal tibial physeal plate. The injury usually results from a valgus stress, similar to the mechanisms commonly associated with tears of the ACL and medial collateral ligament (MCL) in adults. Fractures of the distal femoral physis occur 10 times more frequently than proximal tibial physeal fractures and are most common in boys ages 10 to 14 years. Pain at the physis is a sign of a femoral physeal injury. A physeal fracture of the knee may also present with apparent ligament laxity. When this injury is suspected, one should be careful not to apply excessive force when performing a drawer test or a valgus or varus stress test because this may cause displacement through a physeal fracture. The evaluation should be restricted to a gradually applied force testing for relative laxity compared with the uninjured knee.
Although less likely, injuries of the proximal tibial physis do occur. The mechanism typically is direct trauma, such as a blow to the anterior aspect of the knee. With proximal tibial physeal fractures, symptoms include pain on weight-bearing and point tenderness in the region of the joint line and just distal to it, directly over the region of the proximal tibial physis.
Radiographic evidence is necessary to confirm a diagnosis of physeal fracture; however, the diagnosis may be elusive because some of these injuries spontaneously reduce, and specialized imaging techniques may be required. Historically, stress or oblique radiographs have been used, but MRI is a better diagnostic tool. Increasingly, MRI may be the imaging tool of choice if the radiographic results are normal and the clinical suspicion of a physeal injury is high. Treatment for physeal injuries ranges from closed reduction with casting, to percutaneous pinning, to open reduction and internal fixation. More information on treatment of these injuries is in the chapters on distal femoral and proximal tibial injuries.
Ligamentous Injuries of the Knee
As recently as 40 years ago, some suggested that ligamentous injuries about the knee did not occur in the skeletally immature or were exceptionally rare. Historically, injuries about the knee in children were thought to consistent mainly of fractures and physeal injuries, ∗
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although a growing body of literature supports the concept of serious ligamentous knee injuries in pediatric and adolescent patients and athletes. ∗∗
The increase in knee injuries in skeletally immature patients may reflect several phenomena. The increased use of MRI and its ability to detect soft tissue injuries may play a role, in addition to increased participation in sports.In addition to athletic injuries, trauma studies have also demonstrated ligamentous injuries in skeletally immature subjects, and it is recommended that patients be screened for ligamentous injuries of the knee when fractures or effusion are present about the knee.
Historically, an ACL intrasubstance injury was thought to be less common than tibial spine or tibial eminence fractures. More recent research suggests that ACL tears are becoming more common in pediatric and adolescent patients. A recent epidemiologic study of knee injuries in high school athletes indicated a rate of 0.56 ACL injuries per 10,000 athletic exposures (AEs). An ACL injury was the third most common knee injury in high school athletes, behind an MCL ligament injury (0.80 injuries per 10,000 AEs) and a patella/patellar tendon injury (0.65 injuries per 10,000 AEs). The ACL pulls a fragment of bone from its tibial insertion, the tibial eminence (also referred to as the intercondylar eminence ). Although tibial eminence avulsions are more frequent, evidence suggests that ACL tears without tibial eminence involvement seem to be increasingly common. Interestingly, females, especially those of high school age, are at higher risk of ACL injuries relative to males.
Most of the ligaments and capsular structures of the knee attach to the epiphysis. This anatomic configuration is probably the underlying biomechanical explanation for the higher risk of a physeal injury versus a ligamentous injury about the knee. With the exception of the distal MCL, the ligaments of the knee are contained within the epiphyseal/physeal envelope, which has been described by Stanitski ( Fig. 21-5 ).
Anterior Cruciate Ligament Injury
The ACL originates from the epiphyseal portion of the lateral femoral condyle below the femoral physis and inserts on the epiphyseal portion of the tibia. During torsional force application to the knee, the ligamentous and capsular tissues transfer the forces to the epiphysis, contributing to a physeal injury.
The mechanisms of injury that produce ACL tears in the pediatric and adolescent athlete population are probably similar to those of adults. Two general categories of mechanisms exist: contact and noncontact. Noncontact injuries typically involve landing from a jump with a hyperextended knee or with the knee out of position relative to the body’s center of mass; this produces a valgus stress on the knee combined with axial rotation. Noncontact ACL injuries can also be caused by rapid deceleration or when running. Despite extensive research, a consensus group concluded that the precise mechanism of injury for noncontact ACL injuries is still to be determined.
A child reporting a pop or snap within the joint at the time of injury raises the level of suspicion for a major ligamentous injury. Increased laxity of the major ligaments is normal in females of this age group. As such, it is critical to compare all examinations with the uninjured, contralateral knee. The knee should be evaluated for all the major ligamentous restraints with use of standard functional tests. When significant laxity is found, imaging studies are necessary to determine the specific nature of the injury (i.e., true ligamentous rupture vs. avulsion of the tibial eminence because tibial eminence fractures are readily identified on radiographs). MRI may be helpful for evaluating knee injuries because of its unique ability to visualize soft tissues such as the ACL and the menisci ( Fig. 21-6 ).
The decision regarding conservative treatment versus surgical repair of a complete ACL tear in a child is complex because both surgical and nonsurgical treatments have potential complications. Long-term absence of the ACL subsequent to the injury can result in meniscal damage, osteoarthritis, and poor outcomes. Moreover, several recent studies have shown that delayed reconstruction can lead to chondral and meniscal injuries. Because of concerns that transphyseal drilling during traditional ACL reconstruction would result in growth disturbance or axis deviations, several authors have reported successful physeal-sparing techniques. Recent reports have also shown good results with transphyseal reconstructions in skeletally immature patients, as they approach skeletal maturity.
A limited number of published studies support surgical (intraarticular) reconstruction of the ACL in pediatric and adolescent athletes who intend to return to their preinjury activity level. Most concerns related to surgical reconstruction focus on avoiding intrusion into the distal femoral or proximal tibial physes, which can lead to physeal arrest and result in leg-length discrepancies or angular deformities. Despite these concerns, it appears that reconstructions can be successful when the placement of hardware and transphyseal tunnels is taken into account. Nonetheless, ACL reconstruction remains a controversial topic among pediatric orthopaedists, and growth plate complications from this procedure have been reported. Different surgical techniques may be considered, based on the age of the patient, amount of growth remaining, and presence of other injuries.
Recently, a systematic review and meta-analysis by Frosch and colleagues of 55 articles and a total of 935 patients evaluated the outcomes of ACL reconstructions in children and adolescents. The meta-analysis found overall low rates of complications and also found that physeal-sparing techniques were associated with more leg-length differences and axis deviations, whereas transphyseal techniques had a higher risk of rerupture.
Tibial Eminence Avulsion
Tibial eminence avulsions, usually seen only in children, are the result of mechanisms that would lead to an ACL tear in an adult. Tibial eminence avulsion fractures are classified based on relative radiographic displacement. Type I fractures are nondisplaced and are treated conservatively with immobilization in a long leg cast for 4 to 6 weeks. Type II fractures are minimally displaced, and type III are completely displaced. Type II and type III tibial eminence avulsions may be secured with internal fixation placed either arthroscopically or with open reduction. Reports of meniscal entrapment with more displaced fractures are concerning, and these patients may be best treated with arthroscopic evaluation. The meniscus and transverse meniscal ligament can be impediments to reduction of these fractures. Recent reports have also shown a significant incidence of meniscal tears with these fractures. Treatment of tibial spine fractures depends on the degree of displacement. Nondisplaced fractures can be treated with casting. Fractures with significant displacement may require surgery. Numerous recent investigators have demonstrated excellent outcomes with arthroscopic repair of these fractures. Different techniques have been published for repair of these injuries, including the use of suture-based techniques, buttons, and screw fixation ; in addition, biomechanical studies have also been conducted to analyze these repair techniques. Arthroscopic repair also allows for evaluation of meniscal pathology, such as entrapment or a tear. One significant complication of these injuries is postoperative arthrofibrosis; early motion may help reduce the risk of this complication.
Medial Collateral Ligament
Anatomy and Biomechanics of the Medial Collateral Ligament
The medial aspect of the knee has been described as three distinct layers. The second layer includes the superficial MCL, originating from the medial femoral epicondyle, anterior to the adductor tubercle and below the distal femoral physis. The insertion of the MCL is located distal to the tibial physis. In the third and deepest layer of the medial aspect of the knee, the MCL is a continuation of the joint capsule. This structure is intimately associated with the medial meniscus; thus injuries to this layer of the MCL are often associated with medial meniscal injuries.
These structures act as a complex sleeve of tissues that is both a dynamic and a static stabilizer of the knee ( Fig. 21-7 , A,B ). The static stabilizers include the superficial MCL, the posterior oblique ligament, and the deep MCL. In concert with the MCL, the ACL also plays a role in resisting valgus forces about the knee. The dynamic stabilizers include the vastus medialis and the semimembranosus muscles. The MCL is the primary static knee stabilizer with respect to valgus stress, and both the deep and superficial MCLs contribute resistance. The posterior oblique ligament works in concert with the superficial MCL as a medial stabilizer. The MCL and posterior oblique ligament also resist external rotation of the tibia. The posterior fibers of the MCL–posterior oblique complex tighten as the knee extends ( Fig. 21-8 ). The MCL fibers extend well below the tibial physis in the skeletally immature knee ( Fig. 21-9 ).
Evaluation and Treatment of a Medial Collateral Ligament Injury
There have been relatively few descriptions of MCL injuries in skeletally immature athletes. These injuries are rare in young athletes with completely open growth plates, but they do occur ( Fig. 21-10 ). An MCL injury is probably more common in adolescents as they approach skeletal maturity. The possibility of a physeal fracture always needs to be considered in these pediatric and adolescent patients, especially those with open physes. Fractures can occur through the distal femoral physeal scar and may mimic an MCL injury. In addition, MCL injuries can also occur with epiphyseal fractures or with an avulsion type injury. Bradley and colleagues described a series of pediatric patients with serious knee injuries and reported a small number of MCL injuries. In 40 pediatric patients 16 years or younger with hemarthrosis, Eiskjaer and colleagues identified two isolated ruptures of the MCL.
The history of the event is an important factor for evaluation of MCL injuries. An injury to the MCL most often occurs as a result of a valgus stress but may also be seen with excessive external rotation of the knee. In many sports-related cases, these injuries involve contact with another athlete. This mechanism of injury is very common in American football and soccer, although it can be seen with any contact sport. As a general rule, younger and more skeletally immature patients have a higher risk of sustaining physeal fractures, whereas older more skeletally mature adolescents have a higher probability of soft tissue MCL injuries.
The physical examination is important for distinguishing an MCL injury from a physeal fracture. For most isolated MCL injuries, an effusion, if present, is likely to be small. Palpation of the medial aspect of the knee is important for localizing the area of injury and for determining whether the physis is involved. Tenderness may be localized to the region of the MCL, including the femoral, joint-line, or tibial regions. If an MCL injury is suspected, the knee should be subjected to valgus stress testing at full extension and at 30° of flexion. In cases of an isolated MCL injury, the knee will be stable to stress at full extension because of the integrity of the posteromedial capsular structures and the cruciate ligaments. If laxity is demonstrated in full extension, a more serious soft tissue injury or physeal fracture needs to be considered. In these cases, the patient can be evaluated under anesthesia or by MRI. In flexion, the posteromedial capsular structures are relaxed, which will allow isolated evaluation of the MCL. The degree of laxity should be quantified and compared with the uninjured knee.
Because the literature on MCL injuries in pediatric and adolescent athletes is limited, the adult literature and treatment recommendations, which have evolved over the last 30 years, provide guidance for management of these injuries in young athletes. Kennedy described a surgical procedure for MCL reconstruction in young athletes in the late 1970s, although limited clinical information was available for follow-up evaluation. Bradley and colleagues gathered data over 15 years and described 6 children, ages 6 to 11 years, who underwent operative repair of the MCL after traumatic rupture. Patients were treated with open suture repair of the torn MCL, and 5 to 6 weeks of immobilization. Subjective and clinical results were excellent to good for five patients and fair for one, who also had an associated ACL tear. An isolated MCL injury from an automobile accident has been reported in a 4-year-old child. In this case, primary repair with sutures and 4 weeks of immobilization produced an excellent result.
Although surgical treatment of MCL injuries has been advocated in adults, recent trends have been toward more conservative, nonoperative treatment even for high-grade isolated MCL injuries. ∗
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Although some have suggested that nonoperative treatment of a grade III MCL injury will result in a poor outcome, the current literature supports conservative treatment for most isolated grade III injuries.Some rehabilitation protocols include immobilization, either in full extension or 90° of flexion, whereas others have advocated early motion (without a period of casting or immobilization). In patients treated with early mobilization and weight-bearing as tolerated, a low profile knee brace with a medial and lateral hinge will provide some support to the MCL while healing. A brief period of immobilization may be necessary in patients with significant discomfort. In a study of 51 athletes managed with an active rehabilitation program involving full or partial mobilization, athletes with grade I sprains returned to full participation after an average of 10.6 days and those with grade II sprains returned after 19.5 days.
MCL injuries and ACL injuries may occur simultaneously in young athletes. Recent studies have shown that early bracing of grades II and III MCL injuries, followed by ACL reconstruction in young athletes, results in excellent clinical outcomes.
The Lateral Collateral Ligament and the Posterolateral Corner
Anatomy and Biomechanics of the Lateral Collateral Ligament and Posterolateral Corner
The lateral and posterolateral aspects of the knee have been described by Andrew and associates as the “dark side of the knee” because less was known about this region compared with other areas. Recent studies have defined the anatomy and biomechanics of this region. ∗
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Seebacher and colleagues have described the posterolateral aspect of the knee using a three-layer model in which the lateral collateral ligament (LCL) is within layer III, the deepest layer ( Fig. 21-11 ). The LCL originates from a ridge on the lateral femoral epicondyle, between the origins of the lateral head of the gastrocnemius and the tendon of the popliteus. The pear-shaped insertion of the LCL is on the V-shaped epiphyseal portion of the superolateral aspect of the fibula, proximal to the physis. Anatomic variability of the posterolateral corner is high: absence of the arcuate or fabellofibular ligament occurs in 20% and 13% of the population, respectively. Although anatomic variability is seen in the posterolateral corner, the popliteus complex (popliteus muscle and popliteofibular ligament) and LCL are consistent anatomic findings. ††
Numerous dynamic and static stabilizing structures, in addition to the LCL and the PCL, contribute to the stability of the posterolateral corner. The static structures of the posterolateral corner include the LCL, the popliteofibular ligament, posterolateral joint capsule, arcuate ligament complex, and the fabellofibular ligament. Several dynamic structures exist, including the popliteus, iliotibial band, lateral head of the gastrocnemius, and biceps femoris tendon. ‡
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The LCL and the popliteus complex are likely the most important structures with respect to posterolateral knee stability.The posterolateral structures of the knee are normally subjected to greater forces and are generally stronger than those of the medial aspect of the knee. The role of the posterolateral ligament complex in determining knee stability continues to be investigated. Several studies have concluded that the LCL and popliteus complex are two of the major structures that resist lateral opening and varus stress. ∗
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In addition, recent studies by Pasque and colleagues and Ullrich and colleagues and others have documented the importance of both the popliteus complex and LCL in providing tibial rotational stability.Incidence and Mechanism of Lateral Collateral Ligament and Posterolateral Corner Injuries
LCL and posterolateral corner injuries are rare in skeletally immature patients, and the literature contains little research on this age group. Thus treatment principles for these injuries must partially rely on insight from adult studies. For adult patients, an injury to the lateral and posterolateral structures of the knee is much less common than MCL or ACL injuries. Even though the incidence of an isolated posterolateral corner injury is probably less than 2% to 3% of all knee injuries, a growing number of studies in adult patients have focused on these injuries. An isolated injury to the LCL is extremely uncommon, and an injury to the posterolateral structures is usually seen with other injuries such as strains of the lateral fascia and iliotibial tract, biceps femoris tendon, or PCL. The orthopaedic literature contains limited information concerning the frequency of these injuries in pediatric or adolescent populations. LCL or posterolateral corner injuries are rarely found in studies of knee injuries in children. Swenson and colleagues reported the epidemiology of knee injuries among high school athletes. This study identified LCL and PCL injury rates of 0.17 and 0.05 per 10,000 AEs, respectively. Kovack and colleagues recently described an avulsion injury of the posterolateral corner of the knee in the skeletally immature.
An injury to the posterolateral corner or LCL may occur from athletic competition, motor vehicle accidents, or knee dislocations. When an injury to the LCL and posterolateral corner occurs, it is usually due to a medial blow to the extended knee and may involve external rotation. LCL and posterolateral injuries may also occur from noncontact hyperextension and external rotation or from forceful deceleration with the lower leg planted. With injuries to the proximal fibular physis, laxity resembling LCL or posterolateral injuries may also be present. In cases of a displaced fracture through the fibular physis, surgery may be necessary.
Clinical Examination of the Patient with Suspected Lateral Collateral Ligament or Posterolateral Corner Injuries
Evaluation of the patient’s gait and lower extremity alignment is important for both adults and skeletally immature patients. Adult patients may exhibit gait deviations, which include varus thrust and hyperextension of the knee. The overall alignment of the lower extremity should be evaluated because genu varum may increase the likelihood of a poor outcome. A newly injured knee may exhibit ecchymosis and pain over the posterolateral aspect or in the popliteal fossa region ( Fig. 21-12 ). A careful evaluation of neurovascular status is important because LCL and posterolateral corner injuries may be associated with peroneal nerve injuries. The possibility of a spontaneously reduced knee dislocation should always be considered, and a thorough neurovascular examination is essential.
Numerous tests have been described for assessing laxity of the posterolateral knee complex. These tests evaluate the integrity of the LCL, the posterolateral corner, and the PCL and include the evaluation of translation, varus position, laxity, and external rotation. Each test should be compared with the contralateral knee in all patients. This is especially important because pediatric and adolescent patients often have physiologic laxity. A posterolateral corner injury will demonstrate increased varus laxity, external tibial rotation, and posterior translation. In cases of an isolated posterolateral injury with an intact PCL, posterior translation will be most obvious at 20° to 30° of flexion but will decrease significantly when the knee is flexed to 90°. With combined posterolateral corner and PCL injuries, significant posterior subluxation will occur at 90° of flexion. Varus stress testing at 0° and 30° will demonstrate laxity with LCL and posterolateral corner injuries. A significant amount of varus laxity should raise suspicion of other injuries, including injuries to the PCL and ACL.
In the posterolateral drawer test, the knee is placed in 80° to 90° of flexion, with the foot in fixed position of 15° of external rotation. A force is exerted over the proximal anterolateral tibia, so that posterior movement and outward tibial rotation can be assessed. The sensitivity and specificity of this test are limited, and other tests as well as imaging may be necessary to fully assess the knee.
Another examination, the external rotation recurvatum test, is performed with the patient in a supine position. The great toe of each leg is elevated by the examiner, and the posture of the knee is evaluated. The knee will demonstrate varus, hyperextension, and external rotation of the tibia if a significant injury to the posterolateral corner is present. Other injuries may also be present, including injuries to the ACL, PCL, or both.
The tibial external rotation test is performed with the patient in a supine or prone position. An outward rotation moment is applied to both feet at 30° and 90°. A difference of outward rotation of more than 10° is significant. A positive test at 30° is considered more specific for a posterolateral corner injury, whereas a positive test at 90° suggests a combined posterolateral corner and PCL injury.
The reverse pivot shift test can also be used to evaluate the posterolateral corner, although comparison with the other extremity is important. This test may also be positive in a significant number of patients without injuries, so the results of this test should be interpreted with caution. Several descriptions of this test exist. With the foot held in external rotation and the knee flexed to 90°, the knee is extended. A palpable shift or jerk near full extension may occur, as the posteriorly subluxated tibial plateau shifts anteriorly.
Treatment of Lateral Collateral Ligament and Posterolateral Corner Injuries
An LCL injury is often associated with other ligamentous injuries, such as posterolateral corner injuries or ACL and PCL tears. An injury to the posterolateral corner or PCL is extremely rare in children; thus few reports of treatment exist for this injury. The natural history of LCL and posterolateral corner injuries has not been well-defined in skeletally immature patients. In pediatric patients, cast immobilization is probably a reasonable treatment option until studies support operative intervention. A report of a 4-year-old child with an LCL tear and a femoral fracture treated with a spica cast indicated a good outcome.
Treatment for the adolescent patient with this injury should follow the protocols established for adult patients. Some patients with low-grade injuries may return to activities with little or no disability. Low-grade injuries with minimal laxity may be treated with immobilization for 2 to 4 weeks, followed by a rehabilitation program. In adults, Kannus demonstrated good outcomes for conservative treatment of grade II injuries but poor outcomes for nonsurgically treated grade III injuries.
For grade III injuries, nonoperative treatment may yield poor outcomes, and recent research has focused on early surgical reconstruction in these cases. Several authors have suggested that early reconstruction or primary repair of a posterolateral corner injury yields better results than reconstructions that have been delayed. Numerous techniques have focused on reconstruction of the LCL and popliteus complex, but no technique has emerged as the gold standard. In recent studies of adults, an emphasis has been placed on anatomic reconstruction, and the focus has been on re-creating the natural anatomy and biomechanics of the posterolateral corner, LCL, or both.
Primary repair of injured structures or reduction of avulsed fragments should be the first objective of surgical repair ; although this may not be possible in the chronically injured knee, it may be a reasonable option in a skeletally immature patient. Early repair of a periosteal avulsion has been described. Early intervention after the injury may allow for anatomic repair of injured and avulsed structures. In older or chronic injuries, these structures may not be readily identified, and soft tissue reconstruction procedures may be more appropriate. Tibial avulsions of the popliteus can be reduced by simple screws or suturing, whereas avulsions of the femoral origins of the LCL and popliteus may require sutures through transosseous drill holes. Fibular disruption of the LCL or popliteofibular ligament can be addressed with sutures and reinforcement with the fabellofibular ligament, if present.
More complex procedures to address posterolateral corner and LCL injuries have been described. These include augmentation of a severely torn popliteus tendon with use of a portion of the iliotibial tract, fixed to the tibia via sutures passed through a drill hole. Reconstruction of the popliteofibular ligament can be accomplished with the use of a portion of the biceps femoris tendon fixed to the lateral femoral condyle.
Advancement of the arcuate complex, if intact, has been used by some authors with fair to good results. ∗
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With this technique, the structures of the lateral aspect of the knee, including the lateral head of the gastrocnemius, the popliteus tendon, the arcuate ligament, and the LCL are advanced proximally on the femur in line with the LCL so that tension is restored. The disadvantage of this procedure is that it may produce nonanatomic changes in the ligament biomechanics, which may lead to stretching and failure over time.Combination repairs of the LCL and popliteus have been described by Veltri and Warren. In this technique, reconstruction of the popliteus uses a single drill hole in the lateral femoral condyle and a split patellar tendon graft. The proximal aspect of the graft is secured in the femoral hole and fixed distally in two locations: on the posterior tibia and lateral fibula. This creates a reconstruction that approximates the anatomic course of the popliteus. For reconstruction of the LCL, a portion of the biceps femoris tendon is released proximally, rerouted to the lateral femoral condyle, and attached at the approximate isometric point on the lateral femoral condyle. This method is advantageous because it approximates normal anatomy and biomechanics.
Isolated LCL rupture has been addressed by numerous authors, and techniques have been described to reconstruct this ligament with the use of the biceps femoris tendon, bone–tendon–bone autografts, Achilles allografts, semitendinosus autografts, and quadriceps tendon autografts. With the exception of procedures using the biceps femoris tendon, these techniques use a cephalocaudal-oriented drill hole in the fibular head and a transverse drill hole on the femur. Fixation is achieved with interference screws, sutures, or both. These studies of reconstruction of the LCL have had good results in adults but are limited by their lack of pediatric and adolescent subjects.
Injuries to the posterolateral corner or PCL are likely to occur at or near skeletal maturity, and the concern about physeal arrest may not be a significant clinical problem. In adolescent cases, the use of standard adult techniques, which may use drill holes at or near the physeal region, are probably appropriate because the risk of physeal arrest is less in these older patient groups. Although the authors do not have significant personal experience with these rare injuries in the skeletally immature, primary repair and reduction of avulsions of the LCL or popliteal complex could likely be performed in skeletally immature patients if care is taken to avoid placement of hardware or drill holes across the physis. For LCL reconstruction, techniques that use the attachment of the biceps femoris tendon have an advantage in that they do not require a drill hole in the proximal fibula. Anderson and Anderson reported a case of intraarticular PCL and extraarticular posterolateral corner reconstruction in an adolescent with good outcomes. Knowledge of the anatomy of the ligaments to be reconstructed along with their relation to the physes is helpful in avoiding iatrogenic growth disturbance. The reconstructive drill holes used for LCL and posterolateral corner reconstruction should be relatively small, thus reducing the risk of producing a significant physeal injury. Drill hole positioning should take into account the location of the femoral, tibial, and fibular physeal regions. If drill hole placement avoids the physis, surgical reconstructive techniques for addressing LCL and posterolateral corner injuries may be successful, but this has yet to be demonstrated in clinical or animal studies. Adolescents at or close to skeletal maturity can be safely treated as adults with minimal risk of growth complications. Recent studies of ACL reconstruction have demonstrated the potential for growth plate complications, and these issues will need to be discussed thoroughly with the patient and family before any reconstructive procedure for the ACL, PCL, or other ligaments of the knee. ∗
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The Posterior Cruciate Ligament
Anatomy of the Posterior Cruciate Ligament
The PCL originates from the anteromedial region of the intercondylar notch of the femur and courses posterolaterally to the posterior tibia. Anatomic studies have shown that the PCL has a large oblong femoral insertion, spanning nearly 3 cm in the adult ( Fig. 21-13 ). The PCL attaches posteriorly to the tibial eminence, approximately 10 mm to 15 mm inferior to the posterior tibial plateau and extends distally toward the proximal tibial physis. The PCL is 20% to 50% larger in cross section than the ACL and fans out at its origin and insertion—so much so that the area of attachment is five times the size of the midsubstance cross-sectional area. The midsubstance of the PCL is asymmetric in that larger diameters are on the femoral end of the ligament.
The PCL has been described as having two functional units: the posteromedial bundle and the anterolateral bundle ( Fig. 21-14 ). ∗
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These two nonisometric parts of the PCL have slightly different roles in providing knee stability. From studies in adults, it was found that the anterolateral bundle is twice as large in cross section and is stiffer and stronger than the posteromedial bundle.
Incidence and Natural History of Posterior Cruciate Ligament Injuries
PCL disruption is less common than ACL injuries, and studies in adults have identified PCL injuries in 3% to 20% of patients with knee injuries. Reports of isolated PCL injuries are rare in children. Because of the limited number of PCL injuries in skeletally immature patients, the natural history of this injury in pediatric populations is not well defined. There have been limited case reports in the literature of various PCL injuries, including isolated PCL injuries, PCL tears in combination with other injuries, or avulsions of the tibial or femoral attachments. An incomplete avulsion of the origin of the PCL has also been reported in an adolescent.
Studies of the natural history of isolated PCL injuries in adult patients are conflicting because some have reported good outcomes while others have demonstrated poor long-term knee function. Shelbourne and colleagues found that in athletically active patients with PCL injuries at an average of 5.4 years after injury, half were able to return to the same or higher level of sports, one third returned to a lower level of competition, and one sixth did not return to the same sport. Parolie and Bergfeld, in a study with an average patient follow-up time of 6.2 years, reported on 25 patients who had sustained isolated PCL injuries and were treated nonoperatively. They found that 80% were satisfied with their knees and that 84% had returned to their previous sport (68% at the same level of performance and 16% at a decreased level of performance). Interestingly, they found that patients who were unable to regain 100% of preinjury quadriceps strength were more likely to have a poor outcome and fail to return to preinjury levels of activity. Complications due to chronic PCL deficiency are not clearly defined but are understood to possibly include functional limitations, pain and articular degeneration, and articular cartilage defects.
Reports of the natural history of PCL injuries in children are rare and consist of limited case reports and small series ( Fig. 21-15 ). One case report of nonoperative treatment in a 6-year-old boy showed an excellent functional outcome, despite clinical PCL laxity, which suggests that at least short-term conservative management in children may be appropriate. Another case report of PCL deficiency in a 6-year-old patient reported chronic instability after an initial asymptomatic period lasting more than 4 years. At a follow-up examination 5 years after the injury, the boy reported acute anterior knee pain as well as occasional instability. A tear of the medial meniscus was found on MRI. These two case reports suggest that short-term conservative treatment may be appropriate, but that complications may eventually develop. Kocher and colleagues reported a recent series of 25 skeletally immature patients with PCL injuries. Partial tears or nondisplaced avulsion injuries had good outcomes. Surgical repairs also produced good outcomes with minimal complications in those in whom nonoperative treatment failed.
Evaluation and Management of Posterior Cruciate Ligament Injuries
Examination of the knee for PCL deficiency includes tests described for posterolateral corner and LCL injuries. If the PCL is torn, varus laxity, external tibial rotation, and posterior translation will be present at 90° of flexion. The posterior drawer test at 90° of flexion is very useful for evaluation of the PCL. Laxity or subluxation should be graded and compared with the contralateral knee because pediatric patients often have physiologic laxity. With PCL examination, identification of starting points and endpoints is important because an unsuspected PCL injury can produce a false-positive anterior drawer result if the tibia is sagging posteriorly. The endpoint quality of the ligamentous structures should be graded in addition to the overall laxity or displacement. In the normal knee, the tibial condyle is usually 10 mm anterior to the femoral condyle with the knee at 90° of flexion.
Treatment of Posterior Cruciate Ligament Injuries in Children
Because of the limed data available concerning treatment of pediatric PCL injuries, the adult literature serves as a useful guide. Veltri and Warren have developed algorithms for the approach to PCL injuries in adults. Isolated acute PCL tears with less than 10 mm of posterior laxity at 90° of flexion should be treated with aggressive physical therapy and rehabilitation. Reconstruction should be done for severe tears with more than 10 to 15 mm of laxity or PCL injuries in the knee with multiple other injuries. In adults, chronic PCL injuries initially should be treated with aggressive physical therapy and rehabilitation. Most authors advocate repair of all PCL avulsions in children, although casting for nondisplaced fractures has shown good results.
Treatment of midsubstance tears of the PCL may present problems unique to the immature skeleton. Standard adult procedures may result in iatrogenic damage to the physis, leading to premature growth arrest. However, Lobenhoffer and colleagues performed a repair of an avulsion of the femoral attachment of the PCL in a child with use of transphyseal tunnels and sutures, and no complications were reported. In pediatric and adolescent patients, the risks of causing growth disturbances must be weighed against known complications of chronic PCL deficiency. From the few published case reports and case series, it is advisable to treat PCL tears in children conservatively until skeletal maturity is approached, although intervention may be warranted if symptoms and instability persist.
The unique biomechanical properties of the PCL pose a challenge to reconstruction because a single graft is unlikely to mimic natural anatomy. Evidence exists that single bundle grafts result in increased laxity, presumably because of their inability to approximate the natural PCL. Some authors have advocated a single graft placed in the approximate position of the anterolateral bundle only. With single graft techniques, precise placement of the femoral tunnel is closely tied to functional outcome, more so than location of the tibial tunnel. Single-graft reconstructions are frequently performed with allografts, but bone–tendon–bone and hamstring grafts are also used. Because of concerns about physeal damage to the tibial tubercle, bone–tendon–bone autografts are probably not a desirable choice for the skeletally immature.
Double-tunnel techniques, with a single tibial tunnel and two femoral tunnels, have been described. This style of graft is thought to better approximate the natural biomechanics of the PCL, and there is evidence that these may be superior to single grafts. Paulos advocates the outside-in technique so that the tunnels for the anterolateral and posteromedial bundles can be oriented to be collinear with their maximum tension vectors. Graft choices for the double bundle are numerous: semitendinosus, gracilis autograft, hamstring allograft, anterior tibialis allograft, or quadriceps tendon. Regardless of the technique, in a double tunnel reconstruction, each graft must be tensioned separately. Despite its biomechanical advantages, there are limits to the double tunnel procedure, including a steep learning curve, a more prolonged surgical procedure, and the need for precise placement of each grafted bundle. The double tunnel technique is more complex, but its superiority has been suggested in the literature. The use of single- versus double-bundle grafts for PCL injuries continues to be an active area of research, and many questions remain unanswered. Double-bundle ACL reconstruction techniques have been shown to increase the volume of growth plate damage for the distal femur, and a similar phenomenon may also occur with pediatric double-bundle PCL surgery.
Treatment of an isolated PCL injury is still evolving in adults. Recent descriptions of techniques to treat pediatric PCL injuries have been described, although nonoperative treatment may offer excellent outcomes in patients with isolated injuries. All-epiphyseal PCL reconstruction has been described. A recent series of skeletally immature patients with isolated PCL injuries demonstrated good outcomes at short-term follow-up with nonoperative treatment.
Patellar Dislocations
Epidemiology
Patellar dislocation is a common injury in the skeletally immature and is one of the most common causes of acute hemarthrosis in young athletes. Studies have demonstrated an annual incidence of this injury at 5.8/100,000, and studies in pediatric patients have shown a higher incidence of 43/100, 000. Some studies have suggested that males and females have equal rates of dislocation, whereas others have demonstrated the highest rate of dislocation to be in females younger than 18 years. Although seen in association with underlying diseases, these injuries are very common in the young athlete. These injuries are frequently seen with sports that involve rapid directional changes or cutting.
Anatomy
Most dislocations occur in a lateral direction and are associated with an injury to the medial retinacular tissues and the medial patellofemoral ligament (MPFL). Medial and superior dislocation can also occur, and rare cases of intraarticular dislocation have also been reported. The patellofemoral joint is complex, and the path of the patella during knee motion is a complex combination of motion in multiple planes. At full extension, the patella assumes a slightly lateral relationship to the femoral groove, and in this position, the patella may assume the most lateral displacement. During the first 30° of flexion, the patella begins to engage the femoral sulcus. In patients with patella alta, the patella may not engage the trochlear groove until additional flexion occurs, which may contribute to an increased risk of patellar instability.
Anatomic Risk Factors
Although these injuries may be seen in association with anatomic conditions, increased genu valgum, patella alta, lower extremity torsion abnormalities, trochlear dysplasia, ∗
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increased quadriceps angle, foot pronation, and patellar tilt, among others, the relationship between these physical findings and patellar instability is not clearly defined. Recent studies have increasingly focused on the tibial tubercle and trochlear groove relationship, which may have a significant impact on patellar instability. Patellar dislocations occur in otherwise healthy individuals, although soft tissue laxity may be a significant risk factor. Recent studies of trochlear dysplasia have attempted to define the relationship between trochlear morphology and patellar dislocation. Some of these studies have suggested that trochlear dysplasia may have a genetic basis, and other studies have suggested that the risk of dislocation may be higher in some families.Mechanism of Injury
Several different mechanisms of injury have been proposed, including direct and indirect mechanisms. The indirect mechanism involves a position of internal rotation of the femur, knee valgus, and a planted foot in combination with a quadriceps contraction. The direct mechanism involves a laterally directed force to the medial aspect of the patella. Combinations of these mechanisms can occur.
Medial Patellofemoral Ligament
Although the medial retinacular tissues limit the lateral displacement of the patella, the MPFL is one of the primary restraints preventing patellar dislocation ( Figs. 21-16 and 21-17 ). Injury to this ligament is common during patellar dislocation. This structure originates from the adductor tubercle region of the femoral condyle, travels transversely, and attaches to the upper two thirds of the medial patellar border. Biomechanical studies have shown this to be one of the main soft tissue structures preventing lateral patellar dislocations. ∗
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Other structures contribute to the stability of the patella with respect to lateral subluxation, including the meniscopatellar and tibiopatellar ligaments, and dynamic contribution is produced by the vastus medialis obliquus muscle.
The location of the injury to the MPFL can be clearly seen on MRI. Recent research demonstrates that the location of the injury can be at the MPFL origin, insertion, or mid-substance. The majority of these injuries may occur at the MPFL origin on the adductor tubercle region of the femur.
In the skeletally immature, controversy surrounds the location of the femoral origin of the MPFL and its relationship to the distal femoral physis. Shea and colleagues used a technique to approximate the origin’s location on radiographs and found the center of the origin at a location several millimeters proximal to the physis based on analysis of the lateral radiographs. On the basis of the height of the MPFL, this study suggests that the MPFL origin extends slightly above and below the physis. Nelitz and colleagues used a combination of two previously described techniques to approximate the origin’s location on radiographic images but found the MPFL origin distal to the physis. Kepler and colleagues reviewed MRI scans of children and adolescents with confirmed MPFL tears. They identified the MPFL origin’s mean location to be 5 mm distal to the physis, but the range was from 7.5 mm proximal to 16 mm distal to the physis. Given these discrepant results, further research should be done to clarify the location of the MPFL origin in children and adolescents.
Osteochondral Injuries
In addition to disruption of the medial restraints and the MPFL, which occurs during acute lateral patellar dislocation, osteochondral fractures and contusions are seen in 40% to 76% of patients. ∗
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During the dislocation, the osteochondral fragments may originate from the lateral femoral condyle or the medial patella facet. Many of these injuries can be significant and may not be recognized on plain radiographs. These injuries may result from a shearing force during the patellar dislocation. In some cases, the osteochondral injury of the lateral femoral condyle may be in a more posterior region, in areas of significant weight-bearing during full extension.Natural History
Several studies have attempted to define the natural history of this injury in adult and skeletally immature athletes. Additional long-term studies will be necessary to assess the incidence of osteoarthritis, define subgroups that have a higher risk of secondary dislocations, and determine the effectiveness of nonoperative and operative treatment regimens. Additional studies in younger athletes will also help better clarify the natural history of this injury. †
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Studies have demonstrated redislocation rates of 13% to 52% for nonsurgical treatment. ‡‡
Significant knee dysfunction may persist, even in patients who do not have secondary dislocation episodes.Previous studies on patellar dislocation demonstrate a small number of prospective designs. These study designs may best identify the natural history of this condition and determine which patients need operative or nonoperative treatment regimens. A limited number of prospective studies have evaluated the natural history of patellar dislocations, with a specific focus on secondary dislocation and other dysfunction.
In a well-designed prospective cohort study, Fithian and colleagues followed up 189 patients for 2 to 5 years. The group with the highest risk of dislocations was females 10 to 17 years of age. Approximately 61% of dislocations occurred during sports, and 9% occurred during dancing. The risk of recurrent patellar instability/dislocation appeared to be significantly higher in females. Young age at the time of the first dislocation was also a significant risk factor for future dislocation/subluxation events.
Evaluation
Clinical Evaluation
Patients with a first-time patellar dislocation may recall a specific dislocation event, which may have spontaneously reduced or may have required a reduction at the scene of the injury or in the emergency department. In other cases, patients may describe a significant “pop” or other major mechanical sensation or event, although they may not realize that a dislocation occurred. The dislocation–relocation sequence may occur very quickly. The history, examination, and image evaluation will determine whether patellar dislocation occurred.
Athletes with a first-time patellar dislocation usually are seen with significant effusion. Many patients have been evaluated in the emergency department and have been placed in a knee immobilizer and have been advised to use crutches. Patients may be quite uncomfortable and apprehensive, and the examiner should work to help the patient relax as much as possible. This will facilitate a more complete examination. The examination should include a thorough evaluation and a search for other injuries, including ligamentous injuries such as those to the ACL or MCL, osteochondral injuries, and meniscal tears. Injuries to the medial retinacular restraints and the MPFL may produce tenderness in the region of the MCL. Gentle valgus stress maneuvers with the knee near full extension, and in 30° to 45° of flexion, should help determine if an MCL injury has occurred.
Observation of the patient’s gait and rotational profiles of the lower extremity are important elements in the evaluation. This may be limited in the acute injury setting, especially the review of the gait. Review of the torsional profile of the femur and tibia are important physical examination findings because these may contribute to recurrent instability episodes. For patients with significant rotational abnormalities of the femur and tibia, CT will allow for appropriate estimation of both tibial and femoral torsion.
With regard to the examination of the patellofemoral joint, the examiner should palpate the medial retinacular structures, looking for evidence of disruption of these tissues. Significant ecchymosis or palpable defects could be evidence of major structural damage to these tissues. This palpation should be done very gently because it will not require much pressure to produce discomfort at the site of the traumatized structures. Palpation should also include the entire medial and superomedial border of the patella and the vastus medialis. These areas may be tender because of medial retinacular avulsion, avulsion injury of the vastus medialis, and/or the presence of an osteochondral injury from the medial aspect of the patella. The lateral femoral condyle should also be palpated: areas of tenderness suggest an underlying chondral injury.
The evaluation of patellar stability, especially with regard to significant lateral laxity because of traumatized medial restraints, may be challenging in the first 1 to 15 days after the dislocation. Patellar mobilization after the initial injury may be quite uncomfortable for the patient, and more information may be obtained after the knee has had several weeks of recovery and therapy. Comparison of the injured knee to the uninjured knee can provide very useful information when the degree of laxity of the patellofemoral joint is determined.
Many patients, especially female patients, may have other signs of soft tissue laxity or other anatomic issues that predispose them to primary and secondary dislocations. Stanitski has emphasized the importance of evaluating patients for signs of soft tissue laxity. Evaluating the patients for genu recurvatum, hyperextension of the elbows, and soft tissue laxity of the wrist, thumbs, and fingers may also be helpful during the evaluation and subsequent treatment.
Imaging Evaluation
AP, lateral, and Merchant view radiographs can evaluate patella alta, patella baja, or osteochondral fractures of the patella or the intercondylar groove or lateral femoral condyle. Avulsion injuries of the medial aspect of the patella may be best seen on Merchant view radiographs. Radiographs have limited utility in identifying osteochondral injuries. In addition to radiographic evaluation for the presence of osteochondral injuries, radiographic studies have also been used to assess patellofemoral malalignment. Numerous radiographic and CT measures of patellofemoral dysplasia have been described in the literature, including measures of congruence, sulcus angles, patellar tilt, dysplasia, subluxation, and hyperlaxity, among others. Future studies that use dynamic measurement methods may provide more insight into normal patellofemoral mechanics.
In the authors’ own practice, plain radiographs are routinely evaluated for the presence of patellofemoral alignment, other anomalies, or the presence of significant osteochondral injuries. Most patients come from the emergency department with films available for review. For skeletally immature subjects, the patellar height can be evaluated with the method described by Koshino and Sugimoto ( Fig. 21-18 ).
