Isokinetic evaluation of internal/external tibial rotation strength after the use of hamstring tendons for anterior cruciate ligament reconstruction

Background: Evaluation of the knee after an anterior cruciate ligament reconstruction with the use of the semitendinosus and gracilis (hamstring) autografts has primarily focused on flexion and extension strength. The semitendinosus and gracilis muscles contribute to internal tibial rotation, and it has been suggested that harvest of these tendons for the purpose of an anterior cruciate ligament reconstruction contributes to internal tibial rotation weakness. Hypothesis: Internal tibial rotation strength may be affected by the semitendinosus and gracilis harvest after anterior cruciate ligament reconstruction. Study Design: Prospective evaluation of internal and external tibial rotation strength. Methods: Inclusion criteria for subjects (N = 30): unilateral anterior cruciate ligament reconstruction at least 2 years previously, a stable anterior cruciate ligament (<5-mm side-to-side difference) at time of testing confirmed by surgeon and KT-1000 arthrometer, no history of knee problems after initial knee reconstruction, a normal contralateral knee, and the ability to comply with the testing protocol. In an attempt to minimize unwanted subtalar joint motion, subjects were immobilized using an ankle brace and tested at angular velocities of 60degrees/s, 120degrees/s, and 180degrees/s at a knee flexion angle of 90degrees. Results: The mean peak torque measurements for internal rotation strength of the operative limb (60degrees/s, 17.4 +/- 4.5 ft-lb; 120degrees/s, 13.9 +/- 3.3 ft-lb; 180degrees/s, 11.6 +/- 3.0 ft-lb) were statistically different compared to the nonoperated limb (60degrees/s, 20.5 +/- 4.7 ft-lb; 120degrees/s, 15.9 3.8 ft-lb; 180degrees/s, 13.4 +/- 3.8 ft-lb) at 60degrees/s (P =.012), 120degrees/s (P =.036), and 180degrees/s (P =.045). The nonoperative limb demonstrated greater strength at all speeds. The mean torque measurements for external rotation were statistically similar when compared to the nonoperated limb at all angular velocities. Conclusions: We have shown through our study that patients who undergo surgical intervention to repair a torn anterior cruciate ligament with the use of autogenous hamstring tendons demonstrate with weaker internal tibial rotation postoperatively at 2 years when compared to the contralateral limb.