Hallux Interphalangeal Arthrodesis Following First Metatarsophalangeal Arthrodesis

BACKGROUND: Hallux interphalangeal (IP) arthritis can occur after first metatarsophalangeal (MTP) arthrodesis. IP arthrodesis is a standard treatment, but in the setting of prior MTP surgery there will be increased stress on the IP joint. This may result in diminished potential for bone healing. This investigation assessed the outcomes of hallux IP arthrodesis after first MTP arthrodesis. METHODS: Charts were retrospectively reviewed for patients who underwent interphalangeal arthrodesis between January 1, 2007, and April 3, 2017, and who had a minimum of 12 weeks of follow-up. We compared patients with and without prior ipsilateral first MTP arthrodesis. There were 42 patients whose median follow-up was 9 (range, 3-135) months. RESULTS: Median time from previous first MTP arthrodesis until IP arthrodesis was 54 months. Six nonunions (35.3%) occurred in 17 patients with prior first MTP arthrodesis. Only 2 nonunions (8.0%) occurred in 25 patients with isolated IP arthrodesis. The multivariable risk difference of nonunion was 53.3% ( P = .001). Prior first MTP arthrodesis also was more likely to have complications (52.9% vs 24.0%, respectively). The multivariable risk difference of complications was 35.7% ( P = .082). The speed of bone healing was significantly different, with a multivariable rate ratio of 0.21 ( P = .012). Conclusion Prior first MTP arthrodesis resulted in 4.8 times slower bone healing for IP arthrodesis. It increased the risks of nonunion and any other complications. LEVEL OF EVIDENCE: Level III, retrospective comparative study.