Outcomes of untreated posterolateral knee injuries: an in vivo canine model

The purpose of our study was to determine if sectioning the canine fibular collateral ligament, popliteus tendon, and popliteofibular ligament would result in residual posterolateral instability and produce measureable evidence of early-onset arthritis on ultra-high field MRI. The fibular collateral ligament, popliteus tendon, and popliteofibular ligament were surgically sectioned in six canines. Six months postoperatively, both limbs were biomechanically tested involving 3.25 Nm varus and 1.25 Nm internal and external rotation torques at 28.5A degrees (mean full extension), 60A degrees, and 90A degrees of flexion. A 7.0-tesla MRI scanner acquired T (1 rho)-weighted images, and relaxation time constants were calculated. Compared to the non-operative knees, varus angulation significantly increased by 2.0A degrees, 8.0A degrees, and 12.4A degrees in the operative knees at full extension, 60A degrees flexion, and 90A degrees flexion, respectively. External rotation was significantly increased by 8.1A degrees at full extension, 12.2A degrees at 60A degrees, and 8.2A degrees at 90A degrees. Internal rotation was significantly increased by 9.1A degrees at full extension and 12.4A degrees at 60A degrees. T (1 rho) MRI mapping revealed a significant increase in relaxation times in the medial compartment of the surgical knees compared to controls. This study validated that grade III surgically created posterolateral knee injuries do not heal and that the canine knee developed early-onset changes of the medial compartment, indicative of early-onset osteoarthritis, developed in the operative knees.