Chapter 11 Anterior Cruciate Ligament Reconstruction in Skeletally Immature Patients
Prior to the mid-1980s, mid-substance anterior cruciate ligament (ACL) injuries in the skeletally immature athlete were believed to be rare.25 More recently, ACL injury has been reported in 10% to 65% of pediatric knees with acute hemarthroses.19,42 Although the true incidence and prevalence of ACL tears in the pediatric population have not been established, these injuries are now being recognized with increasing frequency.42,44 Explanations for this apparent change may include improved ability to diagnose injury by physical examination and magnetic resonance imaging (MRI) as well as changes in the activity patterns of young athletes. The puzzling question facing clinicians centers on whether youngsters of today are training and conditioning to the point that the ACL has become more susceptible to injury.
Controversy exists regarding the initial management, indications for operative treatment, and the effect of age and maturity on management. In addition, there is a large practice variation in operative techniques to treat ACL injuries in these patients.
Previously, the concern for iatrogenic growth disturbance in children prevented the routine use of anatomic ACL reconstruction that has proved successful in adults. Alternative surgical treatment options include primary repair, extra-articular reconstruction, and transepiphyseal intra-articular reconstruction. Even though these injuries are occurring with increasing frequency, no unanimity exists concerning the appropriate and safest treatment. There are no long-term studies to help determine the optimal management approach. The few studies that have followed skeletally immature patients to physeal closure after transphyseal ACL reconstruction have documented growth comparable with that of age-matched controls without surgery.1,27,39
Historical recommendations for nonsurgical management of ACL insufficiency in the skeletally immature patient were based primarily on the concern for complications related to physeal injury. However, the majority of active patients treated nonsurgically were unable to return to sports, developed symptomatic instability, sustained meniscal tears, and suffered from long-term sequelae of articular cartilage damage. Unfortunately, the options for the young patient who develops traumatic osteoarthritis are very limited. Therefore, instability (giving-way) must be controlled. If activity modification is successful in limiting episodes of instability, nonoperative treatment is an option. If instability persists, the permanent sequelae from nonoperative treatment are seemingly more difficult to deal with than growth plate injury. For these reasons, ACL reconstruction should be considered.
Graf and associates11 reported poor results at 15 months after injury, with new meniscal tears and episodes of instability in seven of eight skeletally immature patients who did not undergo reconstruction or activity limitations after ACL injury. Similarly, in a series of 18 skeletally immature patients examined an average of 51 months after complete ACL tear, Mizuta and colleagues35 found that all patients had symptoms, 6 had meniscal tears, and 11 had developed radiographic changes. Janarv and coworkers16 found that 10 of 23 skeletally immature patients treated with rehabilitation eventually needed reconstruction. McCarroll and associates29 reported superior results with surgical management of complete ACL tears in prepubescent and junior high school patients compared with patients receiving conservative treatment. Of 16 prepubescent patients treated nonoperatively, 9 ceased sports participation, 4 sustained at least one reinjury, and only 3 were able to return to sport. In a separate group of 75 junior high school athletes with mid-substance tears, McCarroll and colleagues30 reported that 37 of 38 patients who were initially treated nonoperatively had instability and 27 (71%) developed meniscal tears. Overall, 92% (55 of 60) of those treated with reconstruction returned to play.
Nonoperative treatment is contraindicated in patients with giving-way episodes that produce meniscal tears or articular cartilage damage. If surgical repair is chosen, the patellar tendon autograft should not be harvested in a skeletally immature individual because it violates the proximal tibial apophysis and may result in tibial recurvatum. The placement of bone blocks into tunnels drilled across the femoral or tibial physis reliably causes growth arrest and must be avoided. Similarly, disruption of the periosteum over a growth plate can alter growth.
In the pubescent patient in whom a final growth spurt is anticipated, a soft tissue graft can be used. The exact risk of growth plate injury is unknown but can be extrapolated from the literature on trauma and fractures involving the growth plates around the knee.8 If parents are unwilling to accept the risk of growth plate injury, reconstruction should be delayed until the physes are closed.
A tear of the ACL can result from an impact to the knee or, more commonly, a noncontact twisting or landing injury. The timing of injury, either acute or chronic, should be noted. Knee effusion, pain, and ability to bear weight are important factors in diagnosing an ACL tear. An audible pop heard at the time of injury may be reported. An acute hemarthrosis, particularly in the first 6 to 12 hours after injury, should raise concern for ACL injury. Stanitski and coworkers42 found that 47% of preadolescents with a knee effusion had an ACL injury.
Children with congenital limb deficiencies, such as tibial and fibular hemimelia, congenital short femur, or proximal femoral focal deficiencies are other subsets of patients with ACL insufficiency. These children may develop instability at a much younger age and without any history of trauma to the knee. These cases are more complex and must be evaluated on an individual basis.
The most important component in diagnosing pediatric knee injuries is the physical examination.41 The presence of an effusion should be noted. Palpation of the joint line and physeal plates should be performed. Active and passive motion should be documented. Varus and valgus laxity should be checked in full extension and at 30° of flexion. Lachman testing should be assessed for magnitude. Pivot shifting may be quite uncomfortable in the acute setting and is not recommended. If the Lachman examination is positive acutely, the pivot shift test can be deferred until the examination under anesthesia if surgical intervention is chosen. Findings should always be compared with those in the contralateral knee. The patient should be assessed for generalized laxity with the degree of knee hyperextension noted.
A routine four-view radiographic series should be obtained. The formation of the tibial spine and femoral notch should be assessed. Children with congenital limb deficiencies often have a deficient tibial spine and lateral femoral condyle. Comparison views and stress views may be selectively needed if physeal injury is suspected. Magnetic resonance imaging (MRI) can assist in detecting ACL tears as well as associated meniscal pathology and chondral injury in those individuals who are difficult to examine. However, physical examination has been found to be more sensitive and specific than MRI in the evaluation of these patients. In reality, MRI can localize areas of injury but cannot determine degrees of laxity. MRI may be helpful in assessing other causes of anterior knee instability in the young patient, including tibial eminence fractures, periarticular (physeal) fractures, and congenital absence of the ACL. As in adults, arthrometric measurements can be done to support the diagnosis.
The patient’s level of skeletal maturity should be defined preoperatively. It is generally assumed that girls grow until age 14 ± 1 years and boys until age 16 ± 1 years2; however, age may not be the best indicator of potential growth. Peak growth velocity occurs between the ages of 10 to 11 years for girls and 13 to 14 years for boys. Closure of the triradiate cartilage, which can be seen on a standard radiograph of the pelvis, typically marks the end of peak growth velocity.26 The patient can be assessed physiologically for signs of development, as noted by Tanner and Davies.43 Age at onset of menses can be useful in females. After menarche, girls enter a deceleration phase of growth and typically reach skeletal maturity 18 months later. Family height can be used as an approximate estimate of growth potential as well. The patient can be assessed radiographically to determine skeletal maturity using the Risser sign on the pelvis.37 The Risser sign is a radiographic measurement based on ossification of the iliac apophysis, beginning on the lateral aspect and progressing medially. Divided into four quadrants, the Risser sign proceeds from 0 (no ossification) to Risser 4, in which all four quadrants show ossification of the apophysis. Patients with Risser 0 or 1 have a significant amount of growth remaining, and the Risser 4 patient is skeletally mature. Bone age is another method to determine skeletal maturity by obtaining a radiograph of the hand and wrist and comparing it with the standards in the Gruelich and Pyle atlas.12 The “rule of thirds” suggests that the distal femur and proximal tibia grow an average of 0.9 cm and 0.6 cm, respectively, per year of growth remaining.32 Limb lengths and bilateral lower extremity alignment should be measured and any differences noted.
Previous studies have shown that 20% to 100% of pediatric patients who sustain ACL injuries have a concomitant meniscal injury.11,34 Millett and associates34 found that the incidence of medial meniscus tears increases significantly with chronic ACL insufficiency. Of the 22 patients who underwent surgery more than 6 weeks after injury, 72% had associated meniscal tears. If unstable meniscus tears exist, aggressive management is indicated. Every attempt should be made to salvage the meniscus in children and adolescents. Meniscectomy in this age group carries an even more ominous prognosis.18 Manzione and colleagues28 evaluated the results of partial and total meniscectomy in 20 patients with a mean age of 15 years (range, 5–15 yr). At 6-year follow-up, 16 knees had grade I osteoarthritis and 4 had grade II or III changes. Osteochondral injuries may require débridement, drilling, and/or stabilization at the time of ACL reconstruction.
A complete physical examination of the affected knee should be repeated under anesthesia for laxity, including Lachman and pivot shift tests, and again compared with the contralateral side. Prior to ligament reconstruction, arthroscopic visualization of the knee may be needed to assess for the partial or complete nature of the ACL tear if the examination under anesthesia is inconclusive. Partial-tear decisions should be based on the function of the remaining intact ligament and the degree of instability.
Conventional surgical ACL reconstruction techniques used in adults risk potential iatrogenic growth disturbances in children owing to physeal injury. The spectrum of surgical techniques used in skeletally immature patients has included primary repair, extra-articular tenodesis, physeal sparing, and partial or complete transphyseal reconstruction. Skeletal age, activity level, associated injuries, reported success, and expected graft longevity are among the factors to consider when selecting a technique.
DeLee and Curtis7 reported on three patients who underwent primary ACL repair through sutures tied across the physis. At 21 months follow-up, all had clinical laxity and two of the three had episodes of giving-way. Engebretsen and coworkers10 reviewed eight patients 3 to 8 years after primary repair and found that all experienced a decrease in activity level and five of the eight demonstrated instability on clinical examination. Grontvedt and associates13 also noted that primary repair of the ACL in the skeletally immature patient had poor results, similar to those found in adults.
Early reports of physeal-sparing intra-articular reconstruction describe using a hamstring autograft left attached distally, passed into the knee under the anterior portion of the medial meniscus, and fixed to the lateral femoral condyle with staples in the over- the-top position on the femur6 (Fig. 11-1). This technique is nonanatomic and does not reproduce the normal knee ligament kinematics. In a report of nine patients at 36.5 years follow-up, all had a 1+ Lachman and 1+ anterior drawer test. Six of nine patients returned to sports, but with bracing and precautions. No growth disturbances were reported.6
(Modified from Brief, L. P.: Anterior cruciate ligament reconstruction without drill holes. Arthroscopy 7:350–357, 1991. Used with permission from Elsevier.)
More recently, Kocher and colleagues21 described Micheli and coworkers’ technique,33 which uses a combined intra- and extra-articular reconstruction and an autogenous iliotibial band (ITB) without violation of the physes. An incision is made obliquely from the lateral joint line to the superior border of the ITB. The ITB graft is harvested free proximally and left attached to Gerdy’s tubercle distally and tubularized with a whipstitch. Arthroscopy of the knee is then performed through standard portals. The free end of the graft is brought into the knee in the over-the-top position posteriorly. A second incision is made over the proximal medial tibia. Dissection is carried down to the periosteum, and a curved clamp is passed from this incision into the joint under the intermeniscal ligament. The graft is then brought through the knee, under the intermeniscal ligament anteriorly, and out through the tibial incision. The graft is fixed to the femur with the use of sutures to the lateral femoral condyle at the insertion of the lateral intermuscular septum with the knee in 90° of flexion and external rotation. On the tibial side, the graft is sutured to the periosteum of the proximal tibia just distal to the physis with the knee flexed 20°, and tension is applied to the graft (Fig. 11-2).
FIGURE 11-2 Physeal-sparing combined intra-articular and extra-articular reconstruction using an autogenous iliotibial band for prepubescent patients. A, The iliotibial band graft is harvested free proximally and left attached to Gerdy’s tubercle distally. B, The graft is brought through the knee in the over-the-top position posteriorly. C, The graft is brought through the knee and under the intermeniscal ligament anteriorly. D, The graft is fixed to the intermuscular septum on the femoral side and to the periosteum of the proximal part of the tibia on the tibial side.
(A–D, Modified from Kocher, M. S.; Garg, S.; Micheli, L. J.: Physeal sparing reconstruction of the anterior cruciate ligament in skeletally immature prepubescent children and adolescents. Surgical technique. J Bone Joint Surg Am 88[suppl 1 pt 2]:283-293, 2006. Used with permission from the Journal of Bone and Joint Surgery.)