Weightbearing CT Evaluation of Contact and Distance Mapping of the First Tarsometatarsal and Metatarsophalangeal Joints Following MIS Hallux Valgus Correction.

BackgroundThree-dimensional distance and coverage mapping (DM and CM) generated through weightbearing CT (WBCT) can aid in understanding the complex articular relationship in hallux valgus (HV). Minimally invasive (MIS) hallux valgus correction has become popular in correcting this deformity. Prior biomechanical studies have demonstrated that alterations occur at the first metatarsophalangeal (MTP) and tarsometatarsal (TMT) articulations following correction. The purpose of this study is to evaluate DM and CM characteristics at the first MTP and TMT joint as well as the medial metatarsosesamoid joint in a cohort of hallux valgus patients following MIS hallux valgus correction.MethodsTwelve patients (10 female, 2 male; mean age 56.42 ± 13.15 years) were enrolled, undergoing preoperative and 6-month postoperative WBCT scans following MIS hallux valgus correction. Foot Ankle Ability Measure (FAAM) scores were also collected at both visits. Automated segmentation was performed using a deep learning-based approach to generate accurate bone masks from volumetric imaging data. Coverage (contact) and distance maps were created based on established protocols for the medial metatarsosesamoid, first MTP, and first TMT joints. Statistical analysis was conducted using paired t-tests and Wilcoxon signed-rank test as appropriate.ResultsRegarding distance maps, at the metatarsosesamoid articulation, there was a significant increase in distance between the metatarsal and medial sesamoid along all quadrants of the joint postoperatively when compared with preoperative (P < .05). At the MTP and TMT joints, there was no significant change in joint distance postoperatively. Regarding coverage maps, at the MTP joint, increases in joint contact for dorsomedial (17.9 ± 11.1% vs 38.5 ± 15.1%, P < .001) and plantarmedial (21.7 ± 16.0% vs 54.1 ± 24.7%, P < .001) quadrants when compared with pre-op were observed. There was no significant change along its dorsolateral (80.3 ± 10.1% vs 68.7 ± 16.2%, P = .05) or plantarlateral (87.5 ± 6.5% vs 86.8 ± 10.6% P = .85) aspects. At the TMT joint, there was a significant increase at the dorsolateral (83.5 ± 11.8% vs 89.7 ± 10.2%, P = .02) and plantarlateral (57.6 ± 4.7% vs 65.4 ± 5.6%, P < .001) quadrants when compared with pre-op. There was a significant decrease in contact along the dorsomedial (89.2 ± 13.1% vs 71.1 ± 20.6%, P = .002) and plantarmedial (86.7 ± 10.6% vs 70.2 ± 14.3%, P < .001) quadrants. There was no difference between pre-op and post-op FAAM scores.DiscussionNotable differences were observed with respect to contact maps at the MTP and TMT joints indicating improved coverage of the MTP joint postoperatively. Relative decrease in coverage was observed at the medial TMT joint, reflecting medial displacement of the proximal metatarsal segment. Distance mapping at the medial metatarsosesamoid articulation demonstrated improved sesamoid alignment postoperatively.Levels of EvidenceLevel 2.