Aim: This biomechanical study was performed to evaluate the consequences of removing the central part of the patellar tendon on the kinematics and kinetics of the femoro-patellar joint. The tendonectomy was performed in the same manner as is frequently done during anterior cruciate ligament reconstructions. Of particular interest in this study was to identify potential factors of the patellar tendon resection which could result in anterior knee pain.
Method: A simulated isokinetic knee extension from 120 degrees of flexion to full extension was performed on nine human knee cadaver specimens. Joint kinematics was evaluated with ultrasound sensors, and retropatellar contact pressure was measured using a thin-film resistive ink pressure measuring system. Data were taken before and after resection of the central third of the patellar tendon.
Results: Harvesting of the central third of the patellar tendon resulted in an elongation of the remaining patellar tendon by less then 0.5 mm. Furthermore, increases in patellar flexion lower than 1 degree were observed. Small changes in retropatellar pressure were also observed.
Conclusion: The shortening of the patellar tendon due to tendon removal, as already suggested in several previous studies, is not attributed to the removal of the central portion of the tendon itself, but more likely due to secondary scarring contraction of the tissue. The changes of the patellarkinematics and the retropatellar pressure observed in this study are probably not of any clinical significance.