Anterior cruciate ligament reconstruction and rehabilitation in skeletally immature athletes is more complex than in adults and those with closed physes. Trauma or orthopedic interventions may disrupt the physes and create bony bridges resulting in a reduction of bone length or angulation.26
The long bones of the knee account for approximately 65% of potential lower extremity growth as the distal femur accounts for 37% and the proximal tibia for 28%.27,28
The threat of injury to the growth plates of the femur and tibia resulting from the reconstructive procedure and subsequent life‐long limb length discrepancy is particularly important in decision making for pediatric patients. For those sustaining injuries prior to the interval of maximum growth in early adolescence, the potential effect may be of even greater magnitude.
Among the factors considered by orthopedic surgeons in selecting the best reconstructive procedure for the pediatric or adolescent patient is the physiologic age and potential for growth. For the patient in this case report, radiographs were completed to establish his bone age (). At the time of the completion of this radiograph, a bone age of eight years (96 months) was determined. His chronological age was actually eight years and seven months (103 months) or 1.4 standard deviations below the mean, but within normal limits (<2.0 standard deviations). This methodology of determining bone age was established by Greulich and Pyle and considers the pattern of epiphyses and bone development of the hand and wrist.29
The actual radiographs of the individual are compared in an atlas to those of established standards of bone development. Once established for the individual patient, the actual bone age must be a consideration in the choice of operative procedures to minimize the risk of growth disruption. The use of Tanner staging based on sexual ‐characteristics has also been employed by surgeons in order to classify their patients' physiologic age for consideration prior to undergoing knee reconstruction procedures.30
A posterior‐anterior radiograph of the hand to establish the bone age of the patient.
The available surgical procedures for the skeletally immature patient who has sustained and ACL tear are generally categorized as physeal sparing, transphyseal, and partial transphyseal reconstructions.5
Conventional transphyseal tunnels for the graft anchors (as used in those with closed growth plates) have been described, but presumably contain the greatest risk of physis injury and growth disturbance. The extent of this risk, however, is not precisely known. Variations on these techniques in which only one physis is affected with the stabilization have also been reported.31
Theoretically, extra‐articular reconstruction, sparing the physis, provides a method to restore joint stability and maximally avoid risk of growth disturbance. Extra‐articular reconstructions, however, have a history of variable outcomes.5
The technique used in the young athlete in this report is a physeal sparing technique in which the bone tunnels for the hamstring graft were placed only through the femoral and tibial epiphyses.32
Some surgeons recommend the type of technique based on the child's or adolescent's physiologic or bone age. Chicorell et al5
recommend physeal‐sparing combined intra/extra‐articular reconstruction with ITB for the pre‐pubescent patient at Tanner Stage 1 or 2 (Males: ≤12 years, Females: ≤11 years). For adolescents with growth remaining at Tanner Stage 2 or 3 (Males 13‐16 years, Females 12‐14 years), a transphyseal reconstruction using a hamstrings graft and metaphyseal fixation is recommended. For Tanner stage 5 (Males >16 years, Females >14 years), an adult‐type reconstruction with interference screw is recommended. This strategy is advocated to minimize threat of disruption of epiphysis and subsequent interference with growth potential. Similarly, other surgeons suggest the lower limit to perform an adult type ACL reconstruction in which the physes would likely be closed is over 14 years for females and over 16 years for males.33
In an anatomical study based upon 31 patients 10 to 15 years of age, Kercher et al34
determined that less than 3% injury occurs when drilling an 8‐millimeter tunnel across the physis. They further proposed that a vertical tunnel has minimal effect, but the tunnel diameter is critical to minimize the magnitude of physis violation. Interference screws can be placed safely in order to avoid the physis, but require careful planning. Their work was similar in nature to that of other investigators who proposed that less than 7% in the frontal plane and 1% in the transverse plane of the femoral physes were affected as a result of a femoral only transphyseal procedure, presumably offering little risk for growth disturbance.31
Kennedy et al35
recently tested three simulated pediatric ACL reconstructions using six cadaveric specimens, evaluating for the magnitude of anterior tibial translation and the pivot shift. The all epiphyseal technique improved stability, but did not restore the knee to pre‐injury ACL laxity as compared to the extraphyseal iliotibial band (ITB) technique. Greater residual laxity compared to the pre‐injury state was present in the all epiphyseal and transtibial over‐the‐top techniques. The ITB technique, however, actually excessively constrained the rotational component of the knee motion compared to the intact status. Interpretation of these findings must be with caution because of the limited scope of the study.
In a meta‐analysis derived from 55 published reports, Frosch et al36
determined the overall rate of significant limb length discrepancies or malalignment complications to be 1.8%. Transphyseal reconstruction was associated with a significantly lower risk of leg‐length differences or varus‐valgus deviations (1.9%) compared with physeal‐sparing techniques (5.8%), but had a higher risk of re‐rupture (4.2% vs. 1.4%). The authors of the meta‐analysis offered the explanation of the technical challenges of the surgery and the fragility of the growth plate for the apparently counter‐intuitive findings of the physeal sparing techniques having higher risk of leg length discrepancies. One must also consider the selection of physeal sparing procedures in younger patients with inherently greater risk of growth disturbance because of their age. The collective data also suggested bone–patellar tendon–bone grafts are less likely to fail, but had higher risks of leg‐length differences and varus‐valgus deviations than the hamstrings grafts (3.6% vs. 2.0%). A critical analysis must also include acknowledgment that direct comparisons of techniques in clinical trials have not yet occurred. Thus, no single technique has been determined to be clinically superior, in part because all reported data are in small case series with only short‐term follow‐up.37
Direct comparison studies of the techniques with long‐term outcomes will be required to determine if one technique yields best results.