300 Section - Knee muscle strength and endurance after reconstruction of the anterior cruciate ligament (ACL) with patellar or hamstring autografts.

Objectives : ACL injuries are frequent in sports. ACL reconstruction (ACL-R) is done with patellar (P) or hamstring (H) tendon autograft. We compared muscle function and limb symmetry after ACL-R in patients with either P or H autograft.

Design: A retrospective study of athletes after ACL-R. Demographic and clinical data were acquired from testing reports. Isokinetic strength and total work (endurance) of the knee extensors and flexors was measured at 180 deg/s. The primary outcome was the limb symmetry index (LSI) calculated as the highest torque (or total work) of the ACL-R limb divided by the highest torque of the uninjured limb. The data was analyzed with a paired-sample t-tests.

Results: 133 athletes participated (P = 76 (57%) and H = 57 (43%)). Mean age at time of injury: 17.7 ± 4.8 years, with no difference between groups. Knee extensors strength was lower (p < 0.005) in ACL-R limb in both groups (P: 121.5 ± 30.3 vs. 96.9 ± 30.3 Nm; H: 127.7 ± 37.3 vs. 110.5 ± 33.8 Nm). Knee extensors LSI was lower in P (79.7 ± 15.2%) compared to H (86.9 ± 13.5%), p < 0.005. Knee flexors LSI was acceptable in both groups (P = 98.4 ± 15.5; H = 91.5 ± 14.4%, p < 0.05).
Knee extensors total work was lower (p < 0.005) in ACL-R limb in both groups (P: 2037.7 ± 56.1 vs. 1601.1 ± 543.0 Nm; H: 2106.6 ± 694.3 vs. 1823 ± 608.0 Nm) and LSI was lower in P (78.4 ± 15.7%) compared to H (87.3 ± 15.0%), p < 0.005.

Conclusion: ACL-R is associated with strength and endurance asymmetry regardless of graft. Strengthening during rehabilitation may result in better functional outcomes.