Clinical and radiological outcomes after arthrodesis of the first metatarsophalangeal joint

Purpose The main aim of this study was to investigate the correlation between radiographic findings and clinical outcomes following the first metatarsophalangeal (MTP) joint arthrodesis. Methods In a comparative retrospective study, on 46 patients (48 ft), the correlation between post-operative radiographic findings including hallux valgus angle (HVA) and first MTP dorsiflexion angle (MTPDA) and clinical outcomes including VAS pain, modified AOFAS hallux score, and FFI questionnaire were evaluated. Moreover, clinical outcomes were compared between cases with pre-operative diagnosis of first MTP inflammatory arthritis, hallux valgus, hallux varus, and grade 3 and 4 of hallux rigidus. The effect of first MTP arthrodesis on Meary's angle and intermetatarsal angle (IMA) were found out. Results The mean age of the patients was 56.3 +/- 9.1 (range, 29-69) years, including 42 (91.3%) females and 4 (8.7%) males. We had fusion rate of 97.9%, one asymptomatic nonunion case (2.1%). Totally, mean scores of modified AOFAS hallux score, FFI percentage, and VAS pain were 88.9 +/- 12.6, 9.4 +/- 16.5, and 1.23 +/- 2.24, respectively. Hallux varus was associated with the most favourable outcomes; whereas, patients with first MTP arthritis got the worst outcome. Regression analysis test between clinical outcomes and HVA > 15 degrees and first MTPDA >15 degrees showed correlation coefficient of almost zero. No statistically significant differences were found between the clinical outcomes of grade 3 and 4 of hallux rigidus (pvalue of modified AOFAS hallux score, FFI percentage, and VAS pain: 0.879, 0.906, and 0.298, respectively). Mean of HVA and IMA reduction in 15 hallux valgus underwent first MTP fusion were 34.4 degrees and 8.4 degrees, respectively. Meary's angle increased about 4 degrees with statistically significant difference (pvalue 0.001). Conclusion Patients with first MTP fusion > 15 degrees in coronal and transverse plans could have acceptable clinical outcomes. The clinical outcome of first MTP arthrodesis for grade 3 hallux rigidus is comparable with grade 4. First MTP fusion would have positive effect on IMA and Meary's angle.