We perform prospective study to evaluate the isokinetic performance of quadriceps before and 1 year after medial patella-femoral ligament (MPFL) reconstruction with the adductor magnus tendon in the case of recurrent patellar dislocation. The present study is the first to describe the isokinetic function of the quadriceps of the involved and uninvolved extremity, in such a wide range. The MPFL is a crucial passive stabilizer of patella and, along with the conditions of the anatomical shape of the femoral-patellar joint and the function of quadriceps, influences the overall patellar stability. However, only a few studies have examined indirectly or directly the function of quadriceps. A total of 27 patients (average age at surgery was 15.8 years) with recurrent monolateral patellar dislocation were treated with MPFL reconstruction using the adductor magnus tendon. In the study group, healthy and operated quadriceps were evaluated for the following parameters at the velocities of 60 and 180 deg/s before surgery and in the follow-up examination: peak torque, peak torque to body weight, time to peak torque, peak torque angle, torque in 30 degree of the knee flexion (TQ 30 degree), and the torque in the first 180 milliseconds (TQ 180). Preoperative patellar instability and its normalization after MPFL reconstruction have no impact on the isokinetic quadriceps index value which depends on the time and degree of inactivity as well as implementation of appropriate physiotherapy. The increase in the quadriceps muscle strength of a healthy limb is responsible for the persistence of muscle isokinetic imbalance after MPFL reconstruction in pediatric patients. This is a level 2b study.
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