Anterior tibial translation in pediatric ACL-deficient knees under functional orthosis loading: a finite element study.

BACKGROUND

Anterior cruciate ligament (ACL) deficiency increases anterior tibial translation (ATT), predisposing the knee to instability and injury. Functional orthoses are prescribed to limit ATT, yet their biomechanical mechanisms remain poorly quantified.

PURPOSE: To develop ACL-deficient pediatric finite element (FE) knee models that evaluate the effectiveness of ACL orthoses in minimizing ATT and to benchmark braced ACL-deficient predictions against unbraced ACL-intact behaviour.

METHODS

Twenty-two pediatric FE models representing ACL-deficient knees were developed. Simulations replicated Lachman tests (LT) (67 N, 89 N, 134 N anteriorly directed loads) and the pivot shift test (PST). The anterior tibial pad pressures of an ACL knee orthosis (5.05 kPa and 6.75 kPa of 400 mm2 area) were applied to the tibia. ATT of braced ACL-deficient and unbraced ACL-intact simulations were compared.

RESULTS

Orthoses significantly reduce ACL-deficient ATT across all loads (p < 0.001), with mean reductions of 3.1 mm (25.1%) at 67 N, 4.2 mm (26.6%) at 89 N, 4.8 mm (22.6%) at 134 N, and 1.3 mm (18.9%) during the pivot shift test. Compared with unbraced ACL-intact simulations, braced ACL-deficient ATT remained higher, indicating improvement but incomplete restoration (p < 0.001).

CONCLUSION

Orthosis loading significantly decreased ATT in ACL-deficient knees and partially restored sagittal-plane restraint. This validated FE framework provides a reproducible method to assess bracing mechanics and optimize design parameters in pediatric populations where in vivo testing is limited.