A biomechanical analysis of anterior cruciate ligament reconstruction with the patellar tendon. A two year followup.

Eleven patients, 2 years after ACL reconstruction with a patellar tendon graft, returned for follow-up testing consisting of: 1) subjective assessment and functional analysis, 2) objective examination for residual ligamentous instability, 3) isokinetic quadriceps and hamstrings strength assessment, 4) radiographic assessment, 5) instrumented measurement of anterior shear displacement via a knee arthrometer, and 6) force plate and film analysis while performing cutting maneuvers in a laboratory setting. All 11 patients had been tested preoperatively through all steps except the fifth. The group subjectively rated the postoperative knee as 83% of the preinjury status, an increase from a 53% mean prior to reconstruction. Six of 11 patients were able to return to their full preinjury level of competition, with or without a brace. Four patients had positive drawer tests, five had positive Lachman examinations, and all subjects had negative pivot shifts. Significant quadriceps torque deficits remained (P less than 0.0005), with the postoperative knee extensors approximately 85% of the contralateral limb. The involved limb hamstrings were equal in strength to the nonoperated limb. Radiographic evaluation revealed four, five, and four patients with positive findings of the patellofemoral joint, medial joint space, and lateral joint space, respectively. Only one patient had normal radiographs. Instrumented knee laxity testing revealed the operated knee to be significantly looser only during maximum passive displacement (7.2 mm versus 5.3 mm, P less than 0.01) and not during the other measurements. Biomechanical analysis of the straight cut maneuver revealed no significant differences between the nonoperated and operated limbs at the 2 year postoperative mark.(ABSTRACT TRUNCATED AT 250 WORDS)