Comparison of knee extensor strength after anterior cruciate ligament reconstruction using either quadriceps tendon or hamstring tendon autografts

Purpose: The aim was to assess the consequences of quadriceps tendon (QT) harvest on knee extensor strength after anterior cruciate ligament reconstruction (ACL-R) compared to hamstring tendon (HT) autograft. Secondary objectives were to evaluate flexor strength recovery and search for correlation between strength status and functional outcome.

Methods: This a retrospective cohort of 44 patients who underwent ACL-R using either QT (25) or HT (19). Median age was 31.1 years. We assessed thigh muscle strength thanks to concentric iso kinetic evaluation (peak torque) at 60°.s^-1, 180°.s^-1, 240°.s^-1 and eccentric at 30°.s^-1, 7 months on average after surgery. Muscle strength values were compared to the uninjured leg in order to calculate a percentage of deficit as well as unilateral hamstring/quadriceps (H/Q) ratios. KOOS score was obtained at a mean follow-up of 18 months.

Results: Extensor strength deficit (concentric 60°.s^-1) was one average 33.1% in the QT group and 28.2% in the HT group (p = 0.42). Difference of flexor strength deficit (concentric 60°.s^-1) was close to be significant with 5% and 12% of deficit in the QT and HT group, respectively (p = 0.1), and statistically significant for high angular velocity (14% versus 3% at 240°.s^-1, p = 0.04). H/Q ratios were comparable in both groups ranging from 0.62 to 0.78. Quadriceps muscle strength deficit was negatively correlated with the KOOS score (Pearson coefficient = -0.4; p = 0.005).

Conclusion: QT autograft harvest does not yield significant quadriceps muscle weakness after ACL-R, which appear to be a pejorative factor for functional outcome.

Level of evidence: IV, Retrospective study.