Patellar tendon length change after anterior cruciate ligament reconstruction using the midthird patellar tendon.

The purpose of this study was to determine if use of the midthird patellar tendon autograft contributes to or causes patellar tendon shortening or patella baja in anterior cruciate ligament reconstruction. Thirty-six patients undergoing arthroscopically assisted midthird patellar tendon autograft anterior cruciate ligament reconstruction were studied prospectively. Intraoperative patellar tendon length changes were measured. Half of the patients had the tendon defect closed and half had it left open (closing peritenon only). Radiographic tendon length changes and patella baja were assessed using Insall-Salvati and Blackburne-Peel ratios measured on 45 degrees lateral knee radiographs using an adjustable polypropylene jig. Bilateral films were obtained preoperatively and at 2 weeks, 3 months, and 6 months postoperatively. No patients demonstrated evidence of patellar tendon shortening greater than the 5.5% measurement error. Tendon defect closure resulted in negligible tendon shortening intraoperatively, averaging 2.28% (1.11 mm). Of the 18 patients whose defects were closed, 5 showed no shortening. The remaining 13 patients had measurable tendon shortening less than 4% (2 mm). No patients developed patella baja.