The effects of medialization and anteromedialization of the tibial tubercle on patellofemoral mechanics and kinematics.

BACKGROUND Medialization and anteromedialization of the tibial tubercle are used to correct patellar subluxation in adults. PURPOSE To compare the effects of the 2 osteotomies on patellofemoral joint contact pressures and kinematics. STUDY DESIGN Controlled laboratory study. METHODS Tibial tubercle osteotomies were performed on 10 cadaveric human knees. The knees were tested between 0 degrees and 90 degrees of flexion while dynamic patellofemoral joint contact pressure and kinematic data were simultaneously obtained. Four conditions were tested: normal knee alignment, simulated increased Q angle, postmedialization of the tibial tubercle, and postanteromedialization of the tubercle. RESULTS An increased Q angle laterally translated the patella, shifted force to the lateral facet, and increased patella contact pressures. Both medialization and anteromedialization partially corrected the abnormal contact pressures. Medialization partially corrected the shift of force to the lateral facet induced by an increased Q angle, whereas the anteromedialization could not. Both medialization and anteromedialization corrected the patella maltracking. CONCLUSION Medialization and anteromedialization are equivalent in their ability to correct abnormal patellar mechanics and kinematics.