Topography and Morphometrics of the Cartilage Surfaces in the Peritalar Joints

Abstract

Category: Hindfoot; Ankle Introduction/Purpose: Recent studies have highlighted the important role of peritalar joint congruence in maintaining the alignment of the hindfoot. Peritalar subluxation is associated with a variety of pathological deformities including flatfoot, cavovarus foot, clubfoot, as well as foot and ankle stress fractures. To date, studies of peritalar joint congruence have all been performed using either XR, WBCT based direct measurements, or 3D segmentation and analysis. However, none of these techniques can demonstrate the cartilage location nor disruption, nor the exact location of the articulation on the bone surface. Data bias caused by the limitations of these study methodologies is therefore inevitable. This study used 3D surface mapping to assess morphometrics of the cartilage surfaces of the peritalar joints. Methods: 11 fresh-frozen cadaveric feet without trauma nor surgery or significant deformities were dissected to expose the calcaneus, cuboid, talus, and navicular bones, and the articular surfaces. Surface mapping of the articular surfaces and the two bones was completed using an Artec Space Spider 3D scanner and Mmics. Further digital analysis was completed using GeoMagic Studio 10. T-test was used for statistical comparisons, with p< 0.05 as statistically significantly different. Results: Detailed information of the articular surfaces is summarized in Table 1. The average articular area on both sides of the joint matched each other well in the posterior facet of the subtalar joint (4% difference), and calcaneocuboid joint (3% difference) without significant statistical difference, but not in the anterior & middle facets of the subtalar joint, nor the talonavicular joint. In the anterior & middle facets of the subtalar joint, the cartilage articular area on the talar side was 124% of that on the calcaneus (p < 0.05), and in the talonavicular joint the cartilage articular area on the navicular was 138% of that on the talus (p < 0.05). Conclusion: The cartilage articular surfaces in certain peritalar joints do not match its opposing surface in size. In the talonavicular joint, it is easy to understand since area of the socket must be much smaller than that of the ball in order for the joint to glide and rotate. There must be functional reasons for this phenomenon to happen in the anterior and middle facets of the subtalar joint, which need further investigation. This study shows that the extent of subluxation of the peritalar joints may be physiological and should not necessarily be considered as pathological.