RADIOGRAPHIC MEASUREMENTS OF THE 1ST TARSOMETATARSAL (TMT) JOINT FOLLOWING 1ST METATARSOPHALANGEAL (MTP) JOINT ARTHRODESIS
Background: Instability of the 1st tarsometarsal (TMT) joint has been proposed as a cause of hallux valgus. While there is literature demonstrating how fusion of the TMT joint effects hallux valgus, there is little published on how correction of the hallux valgus impacts the 1st TMT joint alignment.
Purpose: The purpose of this study was to determine if correction of hallux valgus impacts the 1st TMT alignment. Improvement in alignment would provide evidence that hallux valgus contributes to 1st TMT instability, not vice-a-versa. Our hypothesis was that correcting hallux valgus angle (HVA) would have no effect on the 1st TMT alignment.
Methods: Radiographs of patients who underwent 1st MTP joint arthrodesis for hallux valgus performed by the senior surgeon were retrospectively reviewed. The HVA, 1-2 intermetatarsal angle (IMA), medial cuneiform-1st metatarsal angle (MCMA), distal medial cuneiform angle (DMCA), relative cuneiform slope (RCS), and 1st metatarsal-medial cuneiform angle (MMCA) were measured and recorded for all patients preoperatively and postoperatively.
Results: Of the 37 patients that met inclusion criteria, statistically significant radiographic improvements were noted in HVA (mean difference 25.3 degrees, p<0.0001), IMA (mean difference 5.98 degrees, p<0.0001), MCMA (mean difference 5.70 degrees, p<0.0001), RCS (mean difference 3.25 degrees, p=0.04), and MMCA (mean difference 7.17 degrees, p<0.0001) comparing preoperative and postoperative radiographs.
Conclusions: Our findings suggest that the radiographic subluxation of the 1st TMT joint will reduce with isolated treatment of the 1st MTP joint. This provides evidence that change in the HVA causes changes in the first TMT joint, not vice-a-versa.