Anterior Cruciate Ligament Injuries in Children and Adolescents




Dramatic increases in youth competitive athletic activity, early sport specialization, and year-round training and competition, along with increased awareness of anterior cruciate ligament (ACL) injuries in children, have led to a commensurate increase in the frequency of ACL tears in the skeletally immature. Recent understanding of the risks of nonoperative treatment and surgical delay have supported a trend toward early operative treatment. This article discusses treatment strategies for ACL injuries in children and adolescents, and offers our preferred treatment strategy for skeletally immature youth athletes with ACL tears.


Key points








  • Youth and adolescent athletes comprise the largest demographic of anterior cruciate ligament (ACL) tears, and the incidence is increasing.



  • Growth disturbance is a common concern for those who treat ACL injuries in skeletally immature athletes.



  • Nonoperative management leads to high rates of sport dropout; continued instability can result in progressive meniscal and cartilage damage as well as arthritic changes.



  • Several physeal-respecting ACL reconstruction techniques exist for use in skeletally immature patients to minimize risk of growth disturbance.






Introduction


Tears of the anterior cruciate ligament (ACL) were once considered rare in skeletally immature athletes; however, they are now observed with increasing frequency. A dramatic increase in youth competitive athletic activity, early sport specialization, and year-round training and competition, along with increased awareness of ACL injuries in children, have led to a commensurate increase in the frequency of ACL tears in the skeletally immature. A recent epidemiologic analysis of a New York State administrative database revealed that the rate of ACL reconstruction in children less than 20 years of age had increased nearly 3-fold over a 20-year period from 1990 to 2009, and indicated that adolescents and teenagers represent the largest per capita demographic of ACL reconstructions.


Although, historically, nonoperative management until skeletal maturity followed by traditional ACL reconstruction was a popular treatment strategy, recent understanding of the risks of nonoperative treatment and surgical delay have supported a trend toward early operative treatment. In light of this, along with the increasing frequency and awareness of ACL injuries in children, surgical methods and instrumentation have evolved, in order to accommodate the unique anatomy of skeletally immature patients.


This article discusses the anatomy of the skeletally immature knee, ACL imaging and physical examination that is unique to children, and treatment strategies for ACL injuries in children and adolescents, including both nonoperative and surgical. The authors also offer their preferred treatment strategy for skeletally immature youth athletes with ACL tears.




Introduction


Tears of the anterior cruciate ligament (ACL) were once considered rare in skeletally immature athletes; however, they are now observed with increasing frequency. A dramatic increase in youth competitive athletic activity, early sport specialization, and year-round training and competition, along with increased awareness of ACL injuries in children, have led to a commensurate increase in the frequency of ACL tears in the skeletally immature. A recent epidemiologic analysis of a New York State administrative database revealed that the rate of ACL reconstruction in children less than 20 years of age had increased nearly 3-fold over a 20-year period from 1990 to 2009, and indicated that adolescents and teenagers represent the largest per capita demographic of ACL reconstructions.


Although, historically, nonoperative management until skeletal maturity followed by traditional ACL reconstruction was a popular treatment strategy, recent understanding of the risks of nonoperative treatment and surgical delay have supported a trend toward early operative treatment. In light of this, along with the increasing frequency and awareness of ACL injuries in children, surgical methods and instrumentation have evolved, in order to accommodate the unique anatomy of skeletally immature patients.


This article discusses the anatomy of the skeletally immature knee, ACL imaging and physical examination that is unique to children, and treatment strategies for ACL injuries in children and adolescents, including both nonoperative and surgical. The authors also offer their preferred treatment strategy for skeletally immature youth athletes with ACL tears.




Anatomy


The physes about the knee remain the greatest anatomic concern of surgeons who treat skeletally immature patients with ACL tears. Significant damage to the tibial or femoral physis may lead to growth disturbance and subsequent length or angular deformity of the lower limb. An understanding of this unique anatomy is vital when planning surgery for youth with ACL injuries.


The tibial and femoral physes are the greatest contributors to overall lower limb longitudinal growth. The distal femoral physis contributes 70% of the femoral length and 37% of the overall limb length over the course of skeletal development at an average rate of 10 mm/y. The distance of the femoral physeal plate and perichondral ring from the femoral origin of the ACL remains unchanged from gestational age, and is 3 mm from the over-the-top-position. The proximal tibial physis contributes approximately 55% of the tibial length and 25% of the overall limb length over the course of skeletal development at a rate of 6 mm/y, on average. Furthermore, the tibial tubercle apophysis is subject to injury and can result in recurvatum deformity. Although skeletal maturity occurs around age 14 years in girls and age 16 years in boys, negligible (<1 cm in each limb segment) growth remains around the knee after age 12 to 13 years in girls and 14 years in boys. Until these ages, ACL reconstruction strategies must respect the growing physes. To date, only small case series have reported on growth disturbance after ACL reconstruction, so the precise incidence is not known. Experienced surgeons from the Herodicus Society and the ACL Study Group revealed 15 cases of postoperative deformity caused by physeal injury, including distal femoral valgus deformity, tibial recurvatum, genu valgum, and significant leg length discrepancy. More recent case reports and imaging studies show the potential for growth disturbance after transphyseal ACL reconstruction, physeal-sparing all-epiphyseal ACL reconstruction, and partial transphyseal reconstruction.




Patient evaluation and diagnosis


Every evaluation should begin with a thorough history and physical examination, as well as ruling out concurrent injury. In adolescents presenting with acute traumatic hemarthrosis, ACL injuries can be present in up to 65% of cases. Reliable physical examination maneuvers to detect ACL insufficiency are similar to those in adult patients and include the Lachman test, anterior drawer test, and the pivot shift. However, pain and swelling can increase guarding and affect patient compliance and subsequent accuracy of these tests; the pivot shift test has been shown to be 98% positive in anesthetized patients compared with only 35% positive in patients who are awake during the examination. It is important to evaluate baseline clinical limb alignment as well as leg length discrepancy. This discrepancy is typically measured with a tape measure (anterior superior iliac spine to medial malleolus), as well as using blocks under the clinically short leg to correct pelvic obliquity and measure functional limb length discrepancy.


MRI is the principal imaging modality used to evaluate for internal derangement of the knee, and is 95% sensitive and 88% specific in detecting ACL tears in children. MRI also allows further evaluation for common associated injuries, including meniscus tears, chondral lesions, and combined ligamentous injury. Traumatic chondral lesions have been observed in up to half of high school athletes with ACL injuries, so careful examination of all cartilage surfaces is important. Identification of these associated injuries may be important in guiding treatment options.


In addition to the standard radiographic evaluation (anteroposterior [AP], lateral, notch, Merchant), surgeons can consider obtaining 130-cm (51-inch) standing AP hip-to-ankle radiographs to quantify any baseline leg length discrepancy and angular deformity noted during the physical examination. Skeletal age should be determined for children and adolescents with open physes, and is most frequently assessed using a posteroanterior left hand radiograph ; however, alternative methods based on pelvis, elbow, and calcaneal radiographs have also been described. Clinically, timing of peak growth velocity may be estimated from Tanner staging, as well as onset of menses in female patients. A thorough understanding of preexisting length and angular deformities as well as remaining growth allows surgeons to both document preexisting deformity and consider realignment using an osteotomy or implant-mediated guided growth in more extreme cases.




Nonoperative and delayed surgical treatment


Nonoperative or delayed surgical management were historically appealing options given the increased healing potential of children and the risk of physeal damage with surgical reconstruction. However, subsequent reports have indicated that nonoperative management leads to high rates of sport dropout (up to 94% unable to participate at preinjury level of activity and up to 50% unable to participate at all) because of recurrent knee instability. Furthermore, continued instability can result in progressive meniscal and cartilage damage, as well as arthritic changes in 61% of knees. This finding is particularly true in children and adolescents because they are not frequently compliant in modifying their postinjury activity levels. Delaying reconstruction until skeletal maturity also has significant drawbacks; several studies have shown increasing frequency of cartilage and meniscus damage with instability episodes and treatment delay. Moksnes and colleagues performed a large, prospective, MRI-based study that advocated against the routine reconstruction of ACL tears in skeletally immature patients. However, the investigators noted that during the 4 years postinjury, 1 in 3 patients required ACL reconstruction for persistent instability and 1 in 5 sustained a new meniscal disorder requiring treatment. Recent meta-analysis of existing data favored early stabilization to decrease instability, pathologic laxity, and return to activity.


Despite this, routine ACL reconstruction may not be necessary for every ACL injury. In one series, 1 in 3 children (mean age, 13.7 years) with partial ACL tears treated nonoperatively with a hinged knee brace, partial weight bearing for 6 to 8 weeks, and a progressive ACL rehabilitation protocol ultimately required surgical reconstruction for persistent instability. Nonoperative management of ACL injury had greater success in children and adolescents of that cohort who sustained tears less than half of the thickness of the ACL, tears of the anteromedial bundle only, less than a grade B pivot shift examination, and those with a skeletal age younger than 14 years. It may be reasonable to consider a trial of nonoperative treatment in patients who meet those criteria, with the understanding that recurrent instability may inevitably persist.




Operative treatment and techniques


Given the perils of nonoperative treatment of complete ACL tears in children outlined earlier, and the understanding of respecting the physis during skeletal growth and development, contemporary surgical instrumentation and techniques allow a variety of reconstruction options. These options may be broadly classified into 3 categories: physeal sparing, partial transphyseal, and transphyseal.


In prepubescent children (Tanner stage 1–2; skeletal age ≤11 years in girls, ≤12 years in boys), a Modified MacIntosh combined intra-articular and extra-articular iliotibial (IT) band reconstruction described by Micheli and Kocher may be performed. During this reconstruction, the central portion of the IT band is harvested proximally and left attached to Gerdy’s tubercle distally. The graft is brought through the knee in an over-the-top-position posteriorly and passed under the intermeniscal ligament anteriorly within an epiphyseal groove on the tibia. The graft is fixed with suture to the intermuscular septum and periosteum on the femur and periosteum on the tibia. This technique has the advantages of avoiding the physes, improving the ease of revision surgery (no previous tunnels and all other autograft sources remain intact), and providing an additional extra-articular limb similar to anterolateral ligament reconstruction. Although some opponents of this technique cite its nonanatomic configuration, biomechanics studies have shown restoration of kinematic constraint and good clinical outcomes with low revision rates at a mean of 5.3 years postoperatively. More recently, techniques using hamstring autograft and all-epiphyseal tunnels with epiphyseal fixation have been described, but midterm to long-term outcomes data for this technique in large clinical series are lacking. In small series, graft rupture rates of 11% to 17% have been reported, and MRI investigation has noted physeal compromise in 10 of 15 tibiae (67%) and 1 of 23 femora (4%), with no clinical growth disturbances at 1 year.


In older children and adolescents with some growth remaining (Tanner stage ≥3; skeletal age ≥12 years in girls, ≥13 years in boys), several physeal-respecting reconstruction options are available that either attempt to avoid the physes or remove an acceptable amount of physeal tissue and use soft tissue grafts without transphyseal fixation hardware. Although the precise amount of acceptable physeal violation in humans is unknown, animal studies indicate that removing greater than 7% of the area of the physeal plate is associated with an increased risk of growth disturbance. These include all-epiphyseal reconstructions, partial transphyseal reconstructions (all-epiphyseal femoral tunnel or over-the-top femoral positioning and transphyseal tibial tunnel), and complete transphyseal reconstructions with more vertical tunnels to minimize cross-sectional area of physeal damage and subsequent risk of growth arrest. Because no technique has shown universal superiority, multiple instrumentation sets and fixation options are available depending on surgeon preference. Biomechanical studies have indicated restoration of many knee kinematic parameters, but long-term comparative outcomes studies are lacking. Lack of careful attention during tunnel drilling may lead to physeal damage and resultant limb length or angular deformity. Furthermore, revision surgery may only use allograft or remaining autograft tissue and must take previously created tunnels into consideration.


In older adolescents nearing skeletal maturity, adult reconstruction techniques may be used. In the absence of collagen abnormalities, many clinicians advocate the use of autograft tissue for primary ACL reconstruction in youth, because large, multicenter studies have shown significantly higher rates of failure with allograft tissue in young athletes.




Author’s preferred treatment


In the senior author’s practice, youth athletes are evaluated for ACL tears as outlined above. In the event a tear is diagnosed, operative management is frequently recommended. However, if the athlete has a skeletal age younger than 14 years, the injury is a partial tear less than half of the thickness of the ACL (particularly of the anteromedial bundle only), and the examination shows less than a grade B pivot shift examination, a patient-centered dialogue with the athlete and family is conducted as to the expectations of a trial of nonoperative management. If nonoperative management is elected, we treat the athlete with a hinged knee brace, partial weight bearing for 6 to 8 weeks, a progressive ACL rehabilitation protocol, activity restriction from pivoting or contact sports, and close follow-up to assess for knee instability or subsequent chondral or meniscal injury.


For operative candidates, a course of prereconstruction physical therapy is prescribed focusing on reducing pain, swelling, and effusion; regaining normal gait mechanics; and maximizing quadriceps and hamstring strength preoperatively. This delay of approximately 4 weeks helps to minimize postoperative arthrofibrosis. In the event of an urgent meniscal (eg, locked bucket-handle tear) or osteochondral injury, the reconstructive surgery can either be staged or performed earlier after appropriate counseling of the risks, benefits, and requirements involved in either approach. Our treatment algorithm is outlined in Fig. 1 .




Fig. 1


Authors’ preferred treatment algorithm for ACL tears in youth athletes.


Prepubescent Patients with Significant Growth Remaining (Tanner Stage 1–2; Skeletal Age ≤11 Years [Girls] or ≤12 Years [Boys])


In prepubescent patients with significant growth remaining (Tanner stage 1–2; skeletal age ≤11 years in girls or ≤12 years in boys), we perform a physeal-sparing ACL reconstruction with IT band autograft ( Fig. 2 ). After an examination under anesthesia, surgery begins with IT band harvest through a longitudinal-oblique 4.5-cm incision from the lateral joint line (a point equidistant from Gerdy’s tubercle and the lateral epicondyle) to the superior border of the IT band. A Cobb elevator is used to elevate the subcutaneous tissue off the superficial surface of the IT band 15 cm or more up the thigh. The anterior and posterior borders of the IT band are identified. Anteriorly, the IT band is confluent with the fascia of the vastus lateralis. The transition point is noted where the dense and opaque IT band tissue transitions to a more transparent vastus fascia. Posteriorly, the IT band blends into the posterior intermuscular septum. Once these borders are identified, the IT band is incised near either border leaving a few millimeters of intact IT band on either side. The cuts are continued proximally with curved meniscotomes for a distance of at least 15 cm. The graft is truncated proximally with a curved meniscotome or an open-ended tendon harvester with cutting mechanism. After harvest, the free end is tubularized with a nonabsorbable suture. The graft is further freed distally from the lateral joint capsule but leaving it attached to the Gerdy tubercle ( Fig. 3 ). The graft is then placed back in the wound to prevent desiccation during arthroscopy.




Fig. 2


Modified MacIntosh IT band ACL reconstruction.



Fig. 3


IT band graft harvest. Isolation of the midportion of the IT band ( A ) is followed by proximal detachment and dissection distally to the Gerdy tubercle ( B ). The graft is then tubularized proximally with sutures that are used to pass the graft.

( From Kocher MS, Garg S, Micheli LJ. Physeal sparing reconstruction of the anterior cruciate ligament in skeletally immature prepubescent children and adolescents. J Bone Joint Surg Am 2005;87(11):2373; with permission.)


Diagnostic arthroscopy is performed through standard anterolateral and anteromedial portals and any meniscal or chondral work is performed at this point. The medial portal is widened and a large curved clamp is introduced into the over-the-top position. The clamp is placed through the soft tissue remnants at the posterior aspect of the over-the-top position to allow for a sling, pushed through the posterolateral capsule of the knee and into the IT band defect on the lateral knee. The suture attached to the free end of the graft is placed in the clamps and brought back into the knee ( Fig. 4 ).




Fig. 4


IT band graft passage is performed by using a curved clamp in the over-the-top position ( A ). The sutures are then passed intra-articularly ( B ).

( From Kocher MS, Garg S, Micheli LJ. Physeal sparing reconstruction of the anterior cruciate ligament in skeletally immature prepubescent children and adolescents. J Bone Joint Surg Am 2005;87(11):2374; with permission.)

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Oct 6, 2017 | Posted by in ORTHOPEDIC | Comments Off on Anterior Cruciate Ligament Injuries in Children and Adolescents
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