The natural history of nonoperative treatment of ACL tears in skeletally immature patients who return to sports is very poor7,10,23,24. There is an increased incidence of meniscal tears and lateral compartment articular cartilage injuries in children with intrasubstance tears of the ACL treated by nonoperative methods for six to twelve weeks after the injury10,23,24.
Growth arrest has been the main concern after ACL reconstruction in skeletally immature patients. Theoretically, extra-articular physeal-sparing ACL reconstruction procedures do not cause growth disturbances because they avoid drilling a tunnel through the growth plate. However, these surgical techniques do not restore the native kinematics of the knee23,25. Nonanatomic extra-articular ACL reconstruction techniques have been abandoned in adults because of residual instability and the subsequent development of osteoarthritic changes in the lateral compartment26.
Many authors recommend drilling through the growth plate and report a minimal risk of growth disturbance when the tunnel is filled with a soft-tissue graft11,19,20. In a survey of the Herodicus Society and the ACL Study Group, Kocher et al.11 reported fifteen cases of growth disturbance following ACL reconstruction in children. Asymmetric growth of the growth plate resulting in angular deformities following ACL reconstruction has been reported in skeletally immature animals27,28 as well as children12,15,19. The pathophysiology of the development of asymmetric growth is unclear. However, it may be secondary to increased growth plate vascularity similar to that noticed following metaphyseal fractures or because of a tether effect of the graft that results in an angular deformity without formation of an osseous growth plate bridge15,28. An all-epiphyseal technique of ACL reconstruction in which the graft or the implant does not cross the growth plate will potentially avoid these complications of osseous bar formation and the tether effect of the graft.
Two and one-half years after our patient underwent all-epiphyseal ACL reconstruction surgery, he had a limp and a leg-length discrepancy of 2.7 cm, which required a screw epiphysiodesis of the ipsilateral distal femoral epiphysis because of a projected 3.5-cm discrepancy at maturity. Growth disturbance resulting in overgrowth following transphyseal ACL reconstruction has rarely been reported. McIntosh et al.29 reported limb-length discrepancy of less than 1 cm in 15 of 16 patients following transphyseal ACL reconstructions in children less than fourteen years of age. In this series, only one patient had a 1.5-cm overgrowth of the operated limb and was treated with an internal shoe lift. Chotel et al.30 described a 1.5-cm overgrowth in a seven-year-old patient who underwent the McIntosh technique of transphyseal ACL reconstruction. In a preliminary report on twelve patients who underwent transepiphyseal ACL reconstruction, Anderson1 reported four patients with growth disturbances: three patients with lengthening of the ipsilateral limb by a mean of 0.7 cm, which he considered to be within normal limits, and one patient with ipsilateral limb shortening of 0.3 cm.
The pathophysiology of overgrowth following physeal-sparing ACL reconstruction may be attributed to reactive hypervascularity that may develop from drilling near the growth plate. This mechanism resembles the hypervascularity following femoral shaft fractures or application of traction pins in the distal part of the femur31,32. To our knowledge, this is the first report of symptomatic limb lengthening following physeal sparing (an all-epiphyseal ACL reconstruction that required a second surgical procedure to correct limb-length inequality). At the latest follow-up, the leg-length discrepancy was 2.5 cm. He was projected to grow for two more years and to achieve near complete correction.
Despite growth arrest being the more common form of growth disturbance following ACL reconstruction in skeletally immature patients, overgrowth is also a possibility. This case report highlights the importance of meticulous preoperative and postoperative clinical evaluation of limb length and alignment in all children undergoing any type of ACL reconstruction. In addition to the better-known complications of limb shortening and angular deformity, this report shows that limb overgrowth that requires surgical correction can complicate an ACL reconstruction in young children.
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