Hamstring Tendon Autograft Is Associated With Increased Knee Valgus Moment After Anterior Cruciate Ligament Reconstruction: A Biomechanical Analysis

Background: There is limited evidence related to the effects of autograft type on functional performance after anterior cruciate ligament reconstruction (ACLR). Purpose/Hypothesis: This study aimed to compare biomechanical outcomes during a drop vertical jump (DVJ) between patients with a hamstring tendon (HT) autograft, quadriceps tendon (QT) autograft with bone block, QT autograft without bone block, and bone–patellar tendon–bone autograft at 6 months postoperatively in an adolescent population. The authors’ hypothesized there would be differences in DVJ biomechanics between athletes depending on the type of autograft used. Study Design: Controlled laboratory study. Methods: Patients aged 8 to 18 years who underwent primary ACLR were included for analysis. Kinematic and kinetic data collected during a DVJ using a 3-dimensional computerized marker system were assessed at 6 months after ACLR and compared with the uninjured contralateral limb. Results: A total of 155 participants were included. There were no significant differences in terms of age, sex, or affected leg ( P≥ .1973) between groups. The HT group was significantly associated with a larger knee valgus moment at initial contact compared with the QT group (28 × 10 –2 vs −35 × 10 –2 N·m/kg, respectively; P = .0254) and a significantly larger maximum hip adduction moment compared with the QT with bone block group (30 × 10 –2 vs −4 × 10 –2 N·m/kg, respectively; P = .0426). Both the QT with bone block (–12 × 10 –2 vs −3 × 10 –2 N·m/kg, respectively; P = .0265) and QT (–13 × 10 –2 vs −3 × 10 –2 N·m/kg, respectively; P = .0459) groups demonstrated significantly decreased mean knee extension moments compared with the HT group. Conclusion: The findings of this study suggest that utilizing an HT autograft resulted in a significantly increased knee valgus moment at initial contact compared with a QT autograft without bone block at 6 months after ACLR in adolescent patients performing a DVJ. A QT autograft was found to be associated with significantly decreased extensor mechanism function compared with an HT autograft. Clinical Relevance: This study adds unique kinematic and kinetic information regarding various ACLR autograft options and highlights the biomechanical deficits that should be taken into consideration in rehabilitation.