Changes in talocrural joint contact stress characteristics after simulated rotationplasty

In order to assess the changes in talocrural joint contact stress after rotationplasty, 10 lower-leg cadaver specimens were axially loaded with 600 N and investigated in two loading situations: (1) Normal loading with a plantigrade foot; (2) in an equinus position of a simulated rotationplasty. Joint contact stress in the talar facet of the talocrural joint was determined with Fuji Prescale film cut to size and analyzed with digital image analysis for joint contact area, mean and peak pressure, contact force, and location of the load application on the trochlea tali. The results demonstrate a significant transfer on the loading zone to the posterior part of the talus (p=0.005), a significant reduction of the contact area (p=0.005) and force (p=0.005), and a significant increase of the mean (p=0.022) and maximum pressures (p=0.013). These results indicate that the rotationplasty causes pronounced changes in joint loading characteristics.