Conversion Arthrodesis for Failed First Metatarsophalangeal Joint Hemiarthroplasty

Background: Arthrodesis is currently the most commonly performed surgical procedure for the treatment of arthritis of the first metatarsophalangeal (MTP) joint. Hemiarthroplasty of the first MTP joint has been shown to have inferior clinical results and higher revision rates. The objective of this study was to assess the clinical outcome of the salvage of failed hallux phalangeal hemiarthroplasty with conversion to arthrodesis. Methods: A retrospective review of patients who underwent salvage of the first MTP joint hemiarthroplasty with conversion to arthrodesis was performed. Preoperative assessment included the visual analog pain (VAP) scale and AOFAS Hallux Metatarsophalangeal Interphalangeal scoring system (AOFAS-HMI). Postoperative outcomes were graded via AOFAS-HMI, VAP, and Foot and Ankle Ability Measure (FAAM). Results: Twenty-one hemiarthroplasties were converted to arthrodesis in 21 patients, with 18 available for follow-up included in the study. There were 13 women and 5 men. Local autologous bone graft was used in 12 cases, while 6 patients required tricortical iliac crest bone graft for the treatment of extensive bone loss. At final follow-up, at a mean of 4.3 years, the average VAS pain score had diminished to 0.75 from 7.8 preoperatively out of 10, while the mean AOFAS-HMI improved from 36.2 out of 100 preoperatively to 85.3 out of 90 (modified to exclude first MTP motion). The mean FAAM ADL/sports were 97.3/91.3, respectively. All patients achieved fusion although at a longer interval than primary fusions. Conclusions: Conversion from a failed hallux phalangeal hemiarthroplasty to arthrodesis showed similar success to primary arthrodesis which was achieved in the majority of cases with the use of regional bone graft for small defects. However, the time to fusion was longer than that of primary arthrodesis, and it sometimes required structural bone graft for augmentation. Level of Evidence: Level IV, retrospective case series.