Hallux Interphalangeal Arthrodesis Following First Metatarsophalangeal Arthrodesis

Category: Midfoot/ForefootIntroduction/Purpose: 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 and decrease local blood supply. These may result in diminished potential for bone healing. This investigation seeks to assess the outcomes of hallux IP arthrodesis after first MTP arthrodesis.Methods: Charts were retrospectively reviewed for patients who underwent interphalangeal arthrodesis between 1/1/2007 and 4/3/2017 and who had a minimum of 12-weeks of follow-up. We compared patients with and without prior ipsilateral first MTP arthrodesis. Charts were reviewed for clinical and radiographic union. Outcomes of interest were nonunion, complications, time to union and speed of union. Statistical data were analyzed by multivariable regression.Results: There were 42 patients whose median follow-up was nine (range, 3-135) months. 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 two 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 statistically significant, 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. The numbers needed to harm was two patients for nonunion and three patients for any complication.