Cadaveric-Biomechanical study on medial retinaculum: Its stabilising role for the patella against lateral dislocation

BACKGROUND: The aim of this study was to analyse the biomechanical role of medial retinaculum, as a stabilising factor against lateral patellar dislocation. MATERIALS AND METHODS: This cadaveric-biomechanical study included the patellae of 10 cadaveric knees, which were surgically exposed and the medial retinaculum of each one was located. A stable 24.51 N force was applied to the four parts of the quadriceps, and an increasing lateral displacing force was applied to the patella, up to 5 mm dislocation. The study was repeated for 0o, 45o, and 90o of knee flexion, with the medial retinaculum intact and dissected. The Wilcoxon signed rank test was used for data analysis. A p value < 0.05 was considered as statistical significant. RESULTS: After the dissection of medial retinaculum, the lateral displacement force was lower at every angle of knee flexion (p = 0.005, p = 0.007, p = 0.005, respectively). The lateral displacement force increased as the flexion angle increased (p = 0.005), regardless of medial retinaculum integrity. CONCLUSIONS: Medial retinaculum acts as a stabilising factor for the patella, against its lateral dislocation in lower flexion angles. Therefore, methods of surgical reinforcement or repair of medial retinaculum could provide protection against recurrent patellar dislocation.