The Keystone of Muller Weiss Disease: How Does the Compressed Navicular Cause the Cascade of Deformities in the Mid and Hind Foot?

Category: Hindfoot; Midfoot/Forefoot Introduction/Purpose: It is believed that Müller Weiss Disease (MWD) starts with narrowing of the lateral and dorsal side of the navicular, followed by lateral rotation and slight dorsal lifting of the talar head and medial rotation of the navicular, a varus heel, and ultimately additional changes in the hindfoot and midfoot. This study used the technique of distance mapping to measure the space of the “peri-navicular” joints on an averaged 3D foot model for both normal controls and a group of MWD feet, to prove the key pathologic changes of MWD. Methods: Weight bearing Scans of 55 health feet without deformities, trauma and surgical history, and 69 feet with MWD were included in this study. The Bonelogic program (Disior, Paragon28) was used to automatically segment the bones and 3D information of each foot in the same group was pooled to create an average foot model for both the controls and the MWD feet. On the two foot models, distance mapping was applied and compared to compare the space of the perinavicular joints (the talonavicular joint, the three navicular cuneiform joints, and the calcaneocuboid joint). The morphology of the navicular bone and the talonavicular articulation in the two groups were also studied. Results: In the MWD foot model, there was significant narrowing of the lateral pole and the dorsal side of the navicular compared with the average normal foot model. The bone articular surfaces of the two foot models matched well, meaning that the deformity changes occurred predominantly to the shape of the navicular but not the contour of the joint surface. The joint space measured using distance mapping was significantly greater in the talonavicular joint, middle and lateral naviculocuneiform joints, and the calcaneocuboid joint in the MWD feet than in normal controls. There was no difference in the joint space of the medial naviculocuneiform joint between the two foot models. Conclusion: It is the change in the shape of navicular bone but not articular surface contour which causes the development of the cascade of deformities in MWD. The sequalae includes increased joint space on both sides of navicular tail, and in the calcaneocuboid joint, lateral subluxation of the talus head, relative medial subluxation of the navicular, a varus heel with more opening in the sinus tarsi, proximal shift of the calcaneal tuberosity, a flat medial arch with subsidence at the talonavicular joint, decreased adduction of the forefoot, medial translation of the cuboid at the calcaneocuboid articulation, and a shortened 1st metatarsal