Functional assessment and muscle strength before and after reconstruction of chronic anterior cruciate ligament lesions.

PURPOSE: The goal of this study was to evaluate strength and functional capacity before and after anterior cruciate ligament (ACL) reconstruction to determine the influences of preoperative strength deficit, graft type, and gender, as well as their clinical relevance in predicting postsurgical recovery and determining the postoperative rehabilitation program. METHODS: This was a retrospective review of prospectively collected uniform data from a group of 191 patients undergoing ACL reconstruction. We assessed functional capabilities and strength of the quadriceps and hamstring at 60 degrees/s and 180 degrees/s by use of a Cybex II dynamometer (Lumex, Ronkonkoma, NY) before and 6, 9, and 12 months after surgery. RESULTS: There was a preoperative quadriceps strength deficit and a decreased limb symmetry index in patients with an ACL deficiency. This strength deficit increased postoperatively, with the highest measured deficit occurring at 6 months postoperatively and a clear improvement from 6 to 12 months. Functional assessment showed identical development. There was a statistically significant relation between an increased quadriceps strength deficit preoperatively and poor early postoperative functional performance. For the bone-patellar tendon-bone (BPTB) group, there was an increased quadriceps strength deficit compared with the semitendinosus and gracilis tendon (STG) group, and the STG group had an increased hamstring strength deficit on postoperative testing. The postoperative hamstring strength deficit is significantly increased in female patients. CONCLUSIONS: All of these data suggest that quadriceps strength deficit is related to the ACL injury and is increased by ACL reconstruction. Even 1 year after ACL reconstruction, a quadriceps strength deficit of almost 20% persists. Flexion strength is within the normal range before and after surgery. These results are influenced by graft choice, with a higher quadriceps strength deficit for BPTB grafts. STG grafts induce a higher hamstring strength deficit compared with BPTB grafts. Functional assessment is improved at 9 and 12 months postoperatively compared with preoperatively regardless of graft type. However, an increased preoperative quadriceps strength deficit results in a lower limb symmetry index at 6 and 9 months postoperatively. LEVEL OF EVIDENCE: Level IV, therapeutic case series.