Achieving high union rates after first metatarsophalangeal joint arthrodesis: Radiographic outcomes and technical pitfalls

BACKGROUND: Fusion of the first metatarsophalangeal (MTP1) joint is a common surgery performed to correct hallux rigidus, hallux rigidus et valgus and other painful degenerative diseases of the MTP1. AIM: To assess outcomes of our surgical technique including non-union rates, accuracy and aims of correction. METHODS: Between September 2011 and November 2020 a total 72 of MTP1 fusions were performed using a low profile, pre-contoured dorsal locking plate and a plantar compression screw. Union and revision rates were analyzed with a minimum clinical and radiological follow up of at least 3 mo (range 3-18 mo). The following parameters were evaluated on pre- and postoperative conventional radiographs: Intermetatarsal angle, Hallux-valgus angle, dorsal extension of the proximal phalanx (P1) in relation to the floor and the angle between the Metatarsal 1 and the P1 (MT1-P1 angle). Descriptive statistical analysis was performed. Pearson analysis was used to assess for correlations between radiographic parameters and achievement of fusion. RESULTS: An overall union rate of 98.6% (71/72) was achieved. Two out of 72 patients did not primarily fuse with one patient suffering from a non-union, whilst the other demonstrating a radiological delayed union without clinical symptoms, with eventually complete fusion after 18 mo. There was no correlation between the measured radiographic parameters and the achievement of fusion. We believe the reason for the non-union was mainly attributed to the patient’s incompliance without wearing the therapeutic shoe leading to a fracture of the P1. Furthermore, we didn`t find any correlation between fusion and the degree of correction. CONCLUSION: With our surgical technique, high union rates (98%) can be achieved using a compression screw and a dorsal variable-angle locking plate to treat degenerative diseases of the MTP1.