Quantitative evaluation of knee instability and muscle strength after anterior cruciate ligament reconstruction using patellar and quadriceps tendon.

Anterior cruciate ligament reconstruction using an autologous graft harvested from the central one-third of the patellar and quadriceps tendon was performed in 65 knees of 65 patients who were followed from 3 to 7 years. Mean anterior laxity of both knees was measured before and after surgery in each patient using the Styker Knee Laxity Tester. At 30 degrees of knee flexion, 58 patients (89%) had differences of less than 2.5 mm between the operated and unoperated knees. Quadriceps strength was measured with the Cybex II and was less than 50% of the uninjured knee at 3 months after surgery. In men, quadriceps strength returned to 78% of normal at 1 year and 85% at final followup. These values were equal to the preoperative level. In women, the quadriceps strength at final followup was 70%, significantly lower than preoperative strength. Hamstring strength recovered to equal the normal strength. Although anterior cruciate ligament reconstruction using one-third of the patellar and quadriceps tendon achieves stability, postoperative quadriceps weakness is a disadvantage. This weakness may be caused by impairment of the knee extensor mechanism resulting from harvesting the graft. We do not currently recommend this technique for anterior cruciate ligament reconstruction.