MEDIAL SOFT-TISSUE RESTRAINTS IN LATERAL PATELLAR INSTABILITY AND REPAIR

This study was undertaken to evaluate the medial ligamentous stabilize rs of the patella in restraining lateral displacement and to assess th eir relative contribution after individual repair. Seventeen fresh fro zen human anatomic specimen knee joints were studied. The specimens we re loaded onto a testing instrument that was designed to measure the c ompliance of the medial and lateral patellar restraints in the coronal plane. Two different cutting and repair sequences were used to test t he individual contributions of the patellar ligaments. The medial pate llofemoral ligament was found to be the major medial ligamentous stabi lizer of the patella. Isolated release resulted in a 50% increase in l ateral displacement, and isolated repair restored balance to the patel la, In addition, the patellotibial and patellomeniscal ligament comple x played an important secondary role in restraining lateral patellar d isplacement. Isolated repair of these ligaments restored balance to ne ar normal levels. The medial patellofemoral retinaculum played only a minor role in patellofemoral instability, Proximal realignment or medi al ligament repair for patellofemoral instability specifically should address repair of the deep layers that contain the restraints to later al patellar displacement. Failure to include these structures in repai r, especially of the medial patellofemoral ligament, may lead to persi stent or recurrent instability.