3D Morphology of the 1-5 TMT Joints: A Surface Mapping Based Cadaveric Study

Category: Midfoot/Forefoot; Hindfoot Introduction/Purpose: The tarsometatarsal (TMT) joints play a crucial role in maintaining the stability of the midfoot and medial column. Disorders of these joints are associated with hallux valgus, hallux rigidus, flatfoot, Lisfranc injury and arthritis. It has been demonstrated that there is a high variability in the morphology of the joint which may influence joint stability thereby leading to or aggravating certain deformities. Understanding the morphology of the articular surfaces comprising the joint is necessary. While prior studies have used XR and CT to analyze the joint, we present our work using 3D surface mapping to evaluate the cartilaginous articulation of the TMT and their related intraarticular joints. Methods: 19 fresh-frozen cadaveric feet with no history of trauma, surgery or deformities were dissected to expose the cuneiforms, cuboid, metatarsal (MT) bones, and related articular surfaces. Surface mapping of the bones and articular surfaces was completed using an Artec Spider 3D Scanner (Figure 1). Further digital analysis was completed using GeoMagic Studio 10. Descriptive and correlation analyses were performed using SAS software. Pearson’s correlation coefficient was used for correlation analysis and statistical significance level was set to P < .05. Results: Means and SDs of the articular surface and the bone length are summarized for the TMT joints (Table 1) and the related intraarticular joints (Table 2). There were statistically significant correlations between the articular-area and the length of the bone in each TMT joint, except for the cuboid (Figure 2). 1 mm bone length increase was correlated with 11.48 mm 2 articular-area increase on MeC; and 10.33 mm 2 articular-area increase on 1st MT. There were three types of morphologies of the 1st TMT joint (Type 1, with 2 facets linked to each other; Type 2, with 2 facets separated; Type 3, 1 large dorsal facet and two separate smaller facets inferiorly). The facet pattern is more obvious on the 1st MT than the MeC side. Conclusion: Previous studies of the TMT morphology were done using either direct manual measurements with descriptive reporting which does not reflect the exact contour of the joint, or XR/WBCT which cannot demonstrate the cartilaginous articulation. This study used a novel technique of surface mapping which overcame the above issues. The remodeled cartilaginous articular surfaces provide foundations for further comparison study, as well as integration of 3D surface mapping with weight-bearing CT analysis, which is currently under investigation by our research group. This will provide important information for diagnosis, surgical planning, and follow-up treatment for relevant disorders.