Trochlear contact pressures after straight anteriorization of the tibial tuberosity.

BACKGROUND Anteromedialization of the tibial tuberosity has been shown to decrease mean total contact pressures of the lateral trochlea and to shift contact pressures to the medial trochlea. HYPOTHESIS Modifying the anteromedialization osteotomy to a straight anteriorization osteotomy of the tibial tuberosity can decrease trochlear contact pressures without a resultant medial shift of forces to the medial trochlear contact area. STUDY DESIGN Controlled laboratory study. METHODS Ten cadavers were tested before and after straight anteriorization tibial tuberosity osteotomy by loading the extensor mechanism with 89.1 and 178.2 N at 0 degrees , 30 degrees , 60 degrees , and 90 degrees of flexion following a validated patellofemoral joint loading protocol. Contact pressures were measured with electroresistive pressure sensors placed directly on the trochlea. RESULTS The mean trochlear contact pressures after osteotomy decreased significantly (P < .05) for loads of 89.1 and 178.2 N at both 30 degrees (23% and 20%, respectively) and 60 degrees (18.7% and 31.9%, respectively) of knee flexion. The peak contact pressures decreased significantly (P < .05) for loads of 89.1 and 178.2 N at 30 degrees (24.3% and 27.0%, respectively) and 60 degrees (31.9% and 24.5%, respectively) and for loads of 89.1 N at 90 degrees (13.4%) of knee flexion. CONCLUSION The authors demonstrated significantly decreased trochlear contact forces after straight anteriorization osteotomy of the tibial tuberosity, without a significant resultant medial shift of the center of force. CLINICAL RELEVANCE Straight anteriorization of the tibial tuberosity may be a useful adjunct for patients with medial articular defects of the patellar or trochlea in whom anteromedialization would be otherwise contraindicated.