Pediatric hand fractures occur primarily in a biphasic age distribution: The toddler and the adolescent. In toddlers, the injury occurs most often secondary to a crush10,57,110,204; for example, a finger caught in a closing door. In teenagers, however, the mechanism is more commonly from a torque, twist, or axial load sustained during contact activities and athletics.29,60,68,121,165,212,220
A higher incidence of pediatric upper extremity fractures is associated with certain youth sports, such as snowboarding, football, basketball, and skateboarding.123 In one study, overweight adolescents were found to have poorer balance, which may explain a propensity for fracture.71 Hand fractures in children peak around age 13, coinciding with active participation in organized contact sports, attempted daredevil maneuvers, as well as the occasional emotional outburst (e.g., punching a wall).15,27,60
The two most common pediatric hand fractures are distal phalanx crush injuries and Salter–Harris (S-H) II fractures of the proximal phalanx.72,86,119,158,217,218 The border digits (thumb and small fingers) are the most vulnerable rays.14,86,119,158,217,218 Dislocations are relatively uncommon in children. Lateral bending forces are more often transmitted through the physis rather than the collateral ligaments in a child’s hand because the growth plate is the path of least resistance.86,110,121,180,217,218 Proximal phalanx S-H II fractures account for nearly 33% of all hand fractures in children. Although rare, the thumb metacarpophalangeal (MCP) joint is the most commonly dislocated joint in the skeletally immature hand.38,67,113 The proximal interphalangeal (PIP) joint is the most commonly injured articular surface, involving volar plate or collateral ligament avulsion fractures.
Fractures and dislocations about the child’s carpus are rare compared to injuries of the adjacent physis of the distal radius.135,218 The scaphoid is the most frequently injured carpal bone in children.11,30,76 Pediatric scaphoid fractures have a peak incidence between the ages of 12 and 15 years.53 Scaphoid fractures are extremely rare during the first decade of life.16,59,76,107,154,165,180,185,203 Only a few reported cases involve children younger than 8 years of age, and the youngest patient reported is 4 years of age.53
Carpal ligament dissociation and tears of the triangular fibrocartilage complex (TFCC) rarely occur in children.198 These tears are usually associated with distal radial fractures, radial growth arrest, ulnar overgrowth, and ulnar carpal impaction. Most often these children present late after acute trauma with activity-related pain. Rotational forces with axial loading cause tearing of the carpal ligaments or TFCC. In children with a positive ulnar variance, the TFCC is thinner and more susceptible to injury. Similarly, hypertrophic unions and nonunions of the ulnar styloid increase the risk of TFCC injuries.
APPLIED ANATOMY OF HAND AND CARPAL BONES
Adults and children have distinct patterns of hand injury because of age-specific patterns of use as well as differences in underlying skeletal and soft tissue composition. Knowledge of the architecture of the physis, the soft tissue origins and insertions, and the surrounding periosteum is essential for recognition and treatment of children’s hand fractures.
Osseous Anatomy of Hand and Carpal Bones
Potential epiphyses exist at both the proximal and distal ends of all the tubular bones. Secondary ossification centers, however, develop only at the distal ends of the metacarpals of the index, long, ring, and small rays, and at the proximal end of the thumb. Conversely, the epiphyses are present only at the proximal ends of the phalanges in all digits.77,121
Secondary Ossification Centers
In boys, the secondary ossification centers within the proximal phalanges appear at 15 to 24 months and fuse by bone age of 16 years (Fig. 10-1).77,196 In girls, the appearance and closure occur earlier, at 10 to 15 months and bone age of 14 years, respectively. The secondary ossification centers of the middle and distal phalanges appear later in both girls and boys, usually by 6 to 8 months. Fusion of the secondary ossification centers, however, occurs first distally then proximally with maturity.
Within the metacarpal, the secondary ossification centers appear at 18 to 27 months in boys and at 12 to 17 months in girls. The proximal thumb metacarpal secondary ossification center appears 6 to 12 months after the fingers. The secondary centers within the metacarpals fuse between 14 to 16 years of age in girls and boys. Carpal bones classically ossify in a pattern moving counterclockwise when looking at the back of your right hand, starting with the capitate and hamate by 1 year of age.
The pattern of carpal bone ossification and appearance of secondary ossification sites in the metacarpals and phalanges is often used to predict the skeletal bone age and years of remaining growth in children (Fig. 10-2).77,196 The fetal wrist begins as a single cartilaginous mass. By the 10th week of gestation, the carpus transforms into eight distinct entities with definable intercarpal separations. Although these precursors display minor differences in contour, the anatomical elements greatly resemble the individual carpal bones in their mature form.111
The capitate is the first bone to ossify, usually within the first few months of life. The pattern of ossification proceeds stepwise from the distal row to the proximal row in a circular fashion. The hamate appears next, usually at about 4 months of age. The triquetrum appears during the second year, and the lunate begins ossification around the fourth year. The scaphoid begins to ossify in the fifth year, usually slightly predating the appearance of the trapezium.107 Scaphoid ossification begins at the distal aspect and progresses in a proximal direction.145 The trapezium and trapezoid ossify in the fifth year, with the trapezoid lagging slightly behind. The ossification pattern usually concludes with the pisiform in the ninth or tenth year. The scaphoid, trapezoid, lunate, trapezium, and pisiform may demonstrate multiple centers of ossification.116,145 Although these variations are well recognized, they may be confused with acute trauma by the inexperienced observer.
The ossific nucleus of each carpal bone is cloaked in a cartilaginous cover during development, which is thought to provide a unique shelter from injury.11,72 This observation is supported by epidemiologic studies of scaphoid fractures that highlight the infrequent incidence in children younger than 7 years of age and the marked increase in teenagers.76,107 The detection of injuries to the immature carpus is problematic because of the difficulties in examining an injured child and the limited ability of radiographs to detail the immature skeleton; therefore, the incidence may be underappreciated.11,140,167
Physeal Anatomy of Hand and Carpal Bones
The physis (growth plate) of the long bones of the hand provides longitudinal digital growth. Pediatric hand fracture geometry is the direct result of the histologic anatomy of the physis.137 The physis is divided into four distinct zones: Germinal, proliferative, hypertrophic, and provisional calcifications (zones I, II, III, and IV, respectively). The zone of chondrocyte hypertrophy (zone III) is the least resistant to mechanical stresses. This zone is devoid of the collagen that provides inherent stabilizing properties. Collagen is present in zones I and II, and the calcium present in zone IV provides similar structural strength.72,202 Therefore, the fracture often propagates through zone III as the path of least resistance. High-energy injuries, however, may undulate through all four zones of the physis.137,184
The irregularity of the physeal zones in the phalanges and metacarpals increases near skeletal maturity.21 Thus, a fracture line may more often be transmitted through several zones in adolescents. This variable path through irregular topography may contribute to increased risk of partial growth arrest following adolescent fractures that involve the physis.184 Physeal irregularity also explains the differing patterns of physeal injuries dependent on age: S-H I and II fractures tend to occur in younger patients compared to the rarer S-H III or IV fractures that are more prevalent in children close to skeletal maturity.
Pseudoepiphyses, Double Epiphyses, and Periphyseal Notching of Hand and Carpal Bones
A persistent expression of the distal epiphysis of the thumb metacarpal is called a pseudoepiphysis.80 The pseudoepiphysis appears earlier than the proximal epiphysis and fuses rapidly. By the sixth or seventh year, the pseudoepiphysis is incorporated within the metacarpal and is inconspicuous. Pseudoepiphyses also have been noted at the proximal ends of the finger metacarpals, usually of the index ray. The only clinical significance is radiologic differentiation from an acute fracture in the setting of incidental injury (Fig. 10-3).
Double epiphyses can be present in any bone of the hand, but these anomalies are more common in the metacarpals of the index finger and thumb. There are variable expressions of double epiphyses, but the true entity is considered only when a fully developed growth mechanism is present on both ends of a tubular bone. Double epiphyses are usually seen in children with other congenital anomalies, but their presence does not appear to influence overall bone growth. When fractures occur in bones with double epiphyses, growth of the involved bone appears to be accelerated.216
Periphyseal “notching” should not be confused with double epiphyses, pseudoepiphyses, or fracture.46,80,206,216 The location of the notches can coincide with the physis or may be slightly more distant from the epiphysis. Notching is a benign condition that does not influence the structural properties of the bone.216
Clinical examination and x-rays of the contralateral noninjured hand are often critical to clarify what is unique individual osseous anatomy versus an acute injury.
Soft Tissue Anatomy of Hand and Carpal Bones
The tensile strength of a younger child’s soft tissues usually exceeds that of the adjacent physis and epiphysis.18,137 For this reason, tendon or collateral ligament avulsions are less common compared to physeal or epiphyseal fractures in the skeletally immature hand.18,84
The terminal tendon of the digital extensor mechanism and the extensor pollicis longus insert on the epiphyses of the distal phalanx. The central slip of the extensor mechanism inserts onto the epiphysis of the middle phalanx. The extensor pollicis brevis inserts onto the epiphysis of the proximal phalanx of the thumb. The abductor pollicis longus has a broad-based insertion onto both the epiphysis and metaphysis of the thumb metacarpal. The extensor digitorum communis for index through small finger connects into the sagittal band at the MCP joint, which in turn lifts the proximal phalanx into extension by its insertion along the volar plate. These extensor tendinous insertions are broad to the thick periosteum, which predisposes bony avulsion injuries.
The long digital flexor tendons (the flexor digitorum profundus [FDP] and the flexor pollicis longus [FPL]) insert along the metadiaphyseal, not epiphyseal, region of their respective terminal phalanges of the fingers and thumb.84 The flexor digitorum superficialis (FDS) inserts onto the central three-fifths of the middle phalanx.
The collateral ligaments at the interphalangeal joint originate from the collateral recesses of the phalangeal head, span the physis, and insert onto both the metaphysis and epiphysis of the middle and distal phalanges (Fig. 10-4). The collaterals also insert onto the volar plate to create a three-sided box that protects the physes and epiphyses of the interphalangeal joints from laterally directed forces.38,84 This configuration explains the rarity of S-H III injuries at the interphalangeal joints. In flexion, the collateral ligaments are stretched because of the shape of the proximal phalanx head. Condyle fractures of the proximal phalanx are therefore at increased risk for displacement with finger motion.
In contrast, the collateral ligaments about the MCP joints originate from the metacarpal epiphysis and insert almost exclusively onto the epiphysis of the proximal phalanx (Fig. 10-5). This anatomic arrangement accounts for the frequency of S-H III injuries at the MCP joint level. The ligamentous anatomy about the thumb MCP joint more closely resembles that of the PIP joints, which mirrors the arrangement of the adjacent physes.
The volar plate is a stout stabilizer of the interphalangeal joint and MCP joints and resists hyperextension forces. The volar plate originates from the metaphysis of the respective proximal digital segment and inserts onto the epiphysis of the distal segment (Fig. 10-4B). The plate receives insertional fibers from the accessory collateral ligaments to create a three-sided box that protects the joint. Hyperextension of the finger joints often results in avulsion injuries of the epiphysis or S-H III at the volar plate insertion site.
The periosteum is robust in a child’s hand and can act as a considerable asset or liability in fracture management. On the positive side, the periosteal sleeve can minimize fracture displacement and aid in fracture reduction. On the negative side, the periosteum can shear off, become interposed between displaced fracture fragments, and prevent reduction.
The skin, nail elements, soft tissues, and bone of the distal digit are closely related (Fig. 10-6). The dorsal periosteum of the distal phalanx is the underlying nutritional and structural support for the sterile matrix and nail bed. The germinal matrix is responsible for generating the nail plate. The volar aspect of the distal phalanx anchors the pulp through tough, fibrous septae that stabilize the skin against shear forces.
Remodeling of Hand and Carpal Bones
A young child’s ability to remodel displaced fractures in the hand and carpus must be incorporated into injury management decision making. Factors that influence remodeling potential include the patient’s age, the proximity of the fracture to the physis, the plane of motion of the adjacent joint, and the presence of malrotation.17 The remodeling capacity is greater in younger children, fractures that are closer to the physis, and deformity in the plane of motion.72,73,134,159 Several clinicians have observed remodeling between 20 to 30 degrees in the sagittal plane in children under 10 years of age and up to 10 to 20 degrees in older children.36,134 Remodeling potential in the coronal or adduction–abduction plane is rarely quantified but is likely greater than or equal to 50% of the remodeling potential in the sagittal plane. Rotational deformity remodeling never occurs and is an absolute indication for fracture management.
The speed of healing in children is remarkable. In the skeletally immature hand, most fractures become clinically stable within 2 weeks. Although this rapid healing potential may allow earlier range of motion and decreased stiffness, delay in treatment of 7 to 10 days may limit a surgeon’s ability to perform a successful reduction without osteoclasis.
ASSESSMENT OF HAND AND CARPAL BONE FRACTURES
Hand and Carpal Bone Fracture Injury Mechanisms
Pediatric hand and carpal bone fracture patterns correlate with mechanism of injury. Assessment of each child with a hand fracture should include detailed description of the injury itself (if witnessed), timing of the injury, treatment prior to presentation, history of previous injuries to the same hand, and identification of potential penetrating or embedded materials such as glass, metal, or teeth.
Axial load injuries nearly always occur through the metacarpals or carpometacarpal (CMC) joints. Digital torsion or lateral bending forces most often propagate through the physis of the phalanx into an S-H II injury or may result in avulsion fractures. Crush injuries can occur in any hand or carpal bone and may involve the nail matrix or articular surface.
Injuries Associated with Hand and Carpal Bone Fractures
Pediatric hand and carpal bone fractures and dislocations overwhelmingly occur in isolation. Children involved in motor vehicle accidents, contact sports, and falls from a height can sustain hand trauma in the setting of head, cervical spine, wrist, elbow, or shoulder girdle injuries, such as clavicular fractures. In these polytrauma cases, treatment decision making may be driven by a need for earlier stabilization to allow the child the ability to use crutches or prevent fracture displacement during rehabilitation of other injuries.
Children who have sustained hand and carpal bone fractures and dislocations from crush injuries, penetrating trauma, mechanical equipment entrapment, or motor vehicle accidents may also have injuries to the soft tissue envelope of the fingers and hand. Nerve, artery, and tendon repair as well as flap or skin graft coverage may dictate the need for hand fracture stabilization in trauma with associated injuries.
Signs and Symptoms of Hand and Carpal Bone Fractures
The evaluation of a child’s hand, especially traumatized infants and toddlers, can be more challenging than that of an adult. The child frequently is noncompliant, unable to understand instructions, and fearful of the physician. The examiner must be patient, engage the child, and often employ the parents to comfort the child as needed. Observation, bribery, and play are the tricks of the trade. The child’s hand use, posture, and movements provide clues about the location and severity of the injury as the child interacts with toys, parents, and the environment in the examining area. A hurried examination or a frightened child can lead to an erroneous or missed diagnosis.
Fracture is diagnosed by swelling, ecchymosis, deformity, or limited movement of the fingers or hand. Fracture malrotation is noted by digital scissoring during active grasp or passive tenodesis. Tendon integrity is observed by digital posture at rest and during active grasp around objects of varying size. Passive wrist examination with finger flexion tenodesis is a critical part of the evaluation to accurately diagnose fracture malrotation.
The history, physical examination, and clinical suspicion are the essential elements to diagnosis of a scaphoid or carpus fracture.153 Although the findings are similar in adults and children, they are more difficult to elicit in children. The relative infrequency of this injury and the difficulty in interpreting radiographs of the immature wrist increase the likelihood of missing a pediatric scaphoid fracture. A distal pole fracture presents with swelling or tenderness over the scaphoid tuberosity. A scaphoid waist fracture presents with pain to palpation within the anatomic snuffbox, scaphoid tubercle, and/or with axial compression of the thumb ray.
For TFCC and carpal ligamentous injuries, pain is localized to the distal ulna and ulnar carpal region. Forearm rotation may be limited and usually reproduces the pain, particularly at the extremes of supination and/or pronation. Compression and ulnar deviation of the carpus against the ulna may reproduce the pain with crepitus. The stability of the distal radioulnar joint should be compared to the contralateral side.141,198
After the child is relaxed, the physician may palpate areas of tenderness and move injured joints to assess their integrity. Stress testing should be gentle, and joint stability should be recorded in the anteroposterior (AP) and lateral directions. Neurologic injuries are especially difficult to detect in a young child. The proper digital artery is dorsal to the proper digital nerve within the finger. Therefore, pulsatile bleeding indicative of a digital artery injury and laceration usually indicates a concomitant digital nerve laceration.
Sensory function is particularly difficult to determine in a young child. Normal discriminatory sensibility does not occur until 5 to 7 years of age. Therefore, meaningful objective data are difficult to obtain in the very young. A clinical clue to sensory impairment is that children often bypass a painful or anesthetic digit during grasp and pinch. A helpful examination maneuver is the wrinkle test. Immersion of an innervated digit in warm water for 5 minutes usually results in corrugation or wrinkling of the volar skin of the pulp. Wrinkling is often absent in a denervated digit. If there is doubt about the integrity of the nerve, operative exploration is imperative.
Comparison to the uninjured hand is invaluable in all aspects of pediatric hand and carpal bone fracture assessment. A thorough upper extremity and whole child examination driven by history and mechanism of injury should be completed for associated injuries. A workup for suspected child abuse or benign neglect may be indicated if the history places a child in a high-risk environment or home alone.
Radiographic Examination of Hand and Carpal Bone Fractures
A careful clinical evaluation is a prerequisite for conducting a proper radiographic examination. Localization of areas of tenderness or deformity directs a focused radiographic assessment. Several pediatric imaging factors complicate interpretation of plain radiographs, including not yet ossified segments and normal variations. Lack of understanding of normal ossification pattern of the immature hand creates problems with the detection of fractures and also promotes false interpretation of ligamentous injuries. Accurate interpretation may require comparison to the uninjured hand or consultation with a pediatric atlas of child development and normal radiographic variants.77,196
Complete evaluation of the injured hand or digit requires AP, lateral, and oblique views. The phalangeal line test is useful in recognizing displaced fractures and joint malalignment. A line drawn from the center of the phalangeal neck through the center of the phalangeal metaphysis at the level of the physis, should pass through the exact center of the metacarpal or phalangeal head in a normal finger, regardless of joint flexion (Fig. 10-7).26 Oblique views are particularly useful for assessing displacement and intra-articular extension. A common radiographic pitfall is failure to obtain a true lateral radiograph of the injured digit. Isolation of the affected digit on the film or splaying of the fingers projects a true lateral view. Stress views are rarely used for fracture evaluation. If the injury can be clinically isolated to a single digit, individual finger x-rays will demonstrate more detail than a zoomed out image of the entire hand.
To radiographically assess the pediatric carpus, AP, lateral, and scaphoid views in ulnar deviation of the wrist are routine. Middle third scaphoid fractures may or may not be evident on initial radiographs. Distal pole fractures are best seen on the lateral view. A pronated oblique view further highlights the CMC joint and distal pole fracture pattern. A scaphoid view places the scaphoid parallel to the film and reveals the scaphoid in its full size. One must be aware of the pseudo-Terry Thomas sign.109 The scaphoid ossifies from distal to proximal, so the distance between the ossified lunate and scaphoid decreases as the child develops and approaches adolescence. Thus, the distance between the scaphoid and lunate ranges from the relatively larger 9 mm in a 7-year-old child to 3 mm in a 15-year-old child.98,109 Failure to appreciate these normal radiographic variants may lead to an erroneous diagnosis of scapholunate dissociation when the apparent gap is filled with normal cartilage and unossified bone. Comparison to contralateral wrist radiographs is extremely useful in distinguishing abnormal from normal patterns; however, one must keep in mind that carpal ossification is not always symmetric. Magnetic resonance imaging (MRI) or computed tomography (CT) scans are usually diagnostic.
If the clinical picture is consistent with a scaphoid fracture but the radiographs are negative, the patient should be immobilized. The child should either be instructed to return in 2 weeks for repeat examination and radiographs, or advanced image studies may be ordered. The use of MRI can help to detect scaphoid fractures that are not visualized on the initial radiographs.22,35,49,96,118 Johnson et al.96 evaluated 56 children (57 injuries) with MRI within 10 days of injury. All children had a suspected scaphoid injury but negative radiographs. In 33 (58%) of the 57 injuries, the MRI was normal, and the patients were discharged from care. In 16 cases (28%), a fractured scaphoid was diagnosed, and treatment was initiated. Sedation is required for a young child having MRI, and the modality may be overly sensitive in identifying bone edema that never develops into a fracture.22,120
Other advanced imaging studies, such as bone scan, CT, and ultrasound have also been shown to be effective in detecting occult fracture (Fig. 10-8).53 The role of bone scan has been nearly supplanted by MRI. In the assessment of fracture displacement for operative indications and in the determination of union CT scans are most valuable. For viewing the carpus, CT images must be made along the longitudinal axis of the scaphoid, which is different from CT imaging of the wrist.169
If plain radiographs reveal an ulnar styloid fracture, a TFCC tear may be suspected. An acute displaced fracture at the base of the styloid suggests the likelihood of a TFCC tear. Arthrograms and MRI scans will help in the diagnosis.28,79
Minifluoroscopy portable units are invaluable and allow a real-time assessment of articular congruity and joint stability. These units have considerable advantages, including the ability to obtain multiple angles, live images, and stress views with low-radiation exposure for the patient and physician. We utilize minifluoroscopy in the child that requires dynamic imaging for accurate diagnosis or when the x-ray technician is having difficulty obtaining orthogonal x-rays.
Differential Diagnosis of Hand and Carpal Bone Fractures
The differential diagnosis in a child who presents with hand trauma includes nontraumatic entities that may be interpreted as acute injuries. These diagnoses are uncommon but may cause swelling, deformity, or decreased motion.
A Kirner deformity is a palmar and radial curving of the terminal phalanx of the small digit. This deformity occurs spontaneously between the ages of 8 and 14 years and may be confused with an acute fracture or epiphyseal separation (Fig. 10-9).103 A Kirner deformity, however, is usually bilateral and not associated with trauma.50 A trigger thumb in a young child is sometimes mistaken for an interphalangeal joint dislocation. This is caused by the fixed flexion posture, near equivalent clinical feel of “joint reduction” with manipulative digital extension, and triggering of the nodule in the FPL through the A1 pulley. The key diagnostic feature or sine qua non of a trigger thumb is the palpable nodule in the FPL over the A1 pulley. Familial camptodactyly or clinodactyly presents predominantly in adolescents when they bump the fifth finger in sports or just notice it is crooked. X-rays consistent with irregular trapezoidal or delta phalanges (a.k.a. longitudinal epiphyseal bracket) and hypoplastic middle phalanx condyles may be hard to distinguish from old or new trauma. Examination of the contralateral side as well as the parents’ hands often guides the clinician toward a congenital etiology of the finger deformity.
Thermal injury to the growing hand (e.g., frostbite, burns from flame or radiation) may cause unusual deformities from altered appositional and interstitial bone growth. Ischemic necrosis of the physes and epiphyses may occur (Fig. 10-10). The clinical result may yield altered bone width, length, or angulation secondary to the unpredictable thermal effect on the growing elements that make interpretation of subsequent trauma difficult.81,142
Osteochondrosis (Thiemann Disease)
Osteochondrosis of the phalangeal epiphyses may cause epiphyseal narrowing and fragmentation, which are characteristic of Thiemann disease. This hereditary entity usually involves the middle and distal phalanges and typically resolves without treatment, though some permanent joint deformity has been reported.40,173
A tumor may be discovered after fracture of the weakened bone or confused with fracture secondary to swelling and pain. An enchondroma of the proximal phalanx is the classic benign tumor that may fracture after trivial trauma (Fig. 10-11). Malignant bone, cartilage, or muscle tumors are rare. Radiographs reveal intrinsic destructive bony changes in an osteogenic sarcoma or extrinsic compression with adjacent periosteal reaction secondary to an adjacent rhabdomyosarcoma.