Evaluation of active knee flexion and hamstring strength after anterior cruciate ligament reconstruction using hamstring tendons.

PURPOSE: The purpose of this study was to evaluate active knee flexion range of motion and hamstring strength following hamstring anterior cruciate ligament (ACL) reconstruction. TYPE OF STUDY: Case control study, consecutive sample.
METHODS: Seventy-four consecutive patients who had undergone hamstring ACL reconstruction underwent isokinetic muscle strength testing at 2 years post surgery. Measurements of the maximum standing active knee flexion angle with the hip extended were also taken. During isokinetic testing, we evaluated flexion torque at 90 degrees of knee flexion, in addition to the peak flexion torque. We further compared these parameters of muscle strength around the knee for the patients in whom only semitendinosus tendon was harvested as a graft source (ST group), and those from whom the semitendinosus tendon and the gracilis tendon were harvested (ST/G group).
RESULTS: Isokinetic testing showed that, in both the ST and ST/G groups, the knee flexor strength of the involved leg was less effectively restored at 90 degrees of knee flexion than at the angle at which the peak torque was generated. Conversely, no significant difference was seen in the side-to-side ratio in either the peak flexion torque or the 90 degrees flexion torque between the groups. The side-to-side ratio in mean maximum standing knee flexion angle was significantly lower in the ST/G group than in the ST group.
CONCLUSIONS: This study suggests that the loss of knee flexor strength following the harvest of the hamstring tendons may be more significant than has been previously estimated. Furthermore, multiple tendon harvest may affect the range of active knee flexion.