Contact features of the talonavicular joint of the foot

Seven cadaveric feet were studied to determine the distribution of the contact area of the talonavicular joint. Feet were loaded axially with soft tissue structures intact and after sectioning of static elements that support the arch. Bony displacement was monitored with a magnetic tracking device, and joint contact was determined from proximity calculations of digitized joint surfaces. With physiologic loading of the intact foot, the number of regions in contact increased. In the unstable foot, there was a shift in contact distribution toward more dorsal and central regions of the navicular bone. This is consistent with the clinical observation that fatigue fractures, acute fractures, and nonunion of navicular fractures occur often in the central navicular body. The alteration in contact characteristics in unstable feet is also consistent with the observation that osteoarthrosis of the hindfoot joints occurs commonly with long-standing arch instability or pes planus deformity.