Longitudinal Change of Medial and Lateral Patellar Stiffness After Reconstruction of the Medial Patellofemoral Ligament for Patients with Recurrent Patellar Dislocation.
BACKGROUND Longitudinal changes in patellar stiffness following reconstruction of the medial patellofemoral ligament for recurrent patellar dislocation at full extension are unknown. METHODS Fifteen consecutive patients (three men and twelve women, with a mean age of twenty two years) with seventeen knees were matched by sex and age to thirty two reference subjects in this prospective study. The follow up period was a minimum of twenty four months. The medial patellofemoral ligament reconstruction used an autograft semitendinosus tendon and an interference screw system with or without lateral release under 10 N of laterally directed force. The medial patellar stiffness and lateral patellar stiffness were measured in 0deg of knee extension using the Patella Stability Tester preoperatively; postoperatively at three, six, twelve, and eighteen months; and at the time of the latest follow up. Before and after the surgical procedure, patients were evaluated for apprehension and Kujala and Lysholm scores; radiographic examinations were performed to evaluate changes, including osteoarthritic changes. RESULTS The medial stiffness of the affected side before the surgical procedure was significantly lower than the lateral stiffness (p 0.004) and the stiffness for healthy reference knees (p 0.004) Medial stiffness three months after the surgical procedure was significantly elevated compared with lateral values (p 0.027) preoperative values (p 0.001) and reference group values (p 0.002) reached the reference level by six months; and was maintained for up to two years. Furthermore, medial stiffness and lateral stiffness were well balanced after six months and this balance was sustained for up to two years postoperatively. No recurrent dislocation occurred during the follow up period; one patient experienced apprehension. Postoperative radiographic findings and clinical scores were significantly improved at the time of the latest follow up (p 0.05) One knee progressed to patellofemoral osteoarthritis. CONCLUSIONS The value for medial stiffness was significantly improved three months after medial patellofemoral ligament reconstruction compared with the preoperative and lateral values and returned to the reference level by six months. Medial stiffness and lateral stiffness of the patella were well balanced by six months and retained that balance for up to two years, with good clinical results. LEVEL OF EVIDENCE Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.
The Journal of bone and joint surgery. American volume