HINDFOOT JOINT PRESERVATION VERSUS FUSION IN PATIENTS WITH IPSILATERAL HINDFOOT AND ANKLE ARTHRITIS (COFAS TYPE 4) UNDERGOING TOTAL ANKLE ARTHROPLASTY: A COMPARISON OF PROSPECTIVELY COLLECTED OUTCOMES

Adjacent subtalar (STJ) or talonavicular (TNJ) joint arthritis poses a dilemma in end stage ankle arthritis. The Canadian Orthopaedic Foot & Ankle Society (COFAS) Classification defines such cases as Type 4. In these cases, undergoing total ankle arthroplasty (TAA), fusion of the STJ and/or TNJ or preservation of these joints are both options. Joint preservation may reduce operative time and potential complications but has potential for ongoing hindfoot pain reflected in outcome scores. Hindfoot fusion may offer the potential of greater pain relief, but at the risk of increased OR time and complications. The purpose of this study was to compare the outcomes of patients undergoing TAA with or without STJ and/or TNJ fusion in COFAS type 4 cases. We retrospectively reviewed prospectively-collected multi-center data on 148 ankles with COFAS Type 4 arthritis that underwent TAA by 7 different surgeons and analyzed the trend of their Ankle Osteoarthritis Scale (AOS) and SF36 Physical Component Summary (PCS) scores pre-operatively and at 1, 2 and 3–5 years post-operatively. Scores were compared between those who underwent fusion of the STJ and/or TNJ (Fusion Group [FG], n=89) and those who did not (Preservation Group [PG], n=59). Multivariant analyses were also performed to account for potential demographic differences within the patient cohorts. The primary outcome measure was the AOS score at latest follow-up (LFU). Secondary outcomes included the SF36 PCS score, COFAS Reoperation Coding System (CRoCS) rates and survivorship. Mean follow up was 6.9 years. Mean pre-operative AOS scores for FG and PG were similar (55.9 and 57.5, respectively, p=0.56). Mean AOS scores at LFU for both groups were not significantly different (FG – 24.6; PG – 25.2; p=0.89). SF36 PCS scores improved from 32.9 pre-operatively to 42.2 at LFU for FG and from 33.9 to 40.0 for PG; differences pre-operatively and at LFU were not significant (p=0.51, p=0.26, respectively). Both groups achieved their best mean scores across all measurement scales at 2 years post-operatively. Results from multivariant analyses controlling for demographics, comorbidities, surgeon, TAA implant type, and pre-operative score showed no significant difference in mean AOS scores at LFU between the two Groups. Reoperations in PG included 2 Code 3 procedures (hindfoot fusion) and 2 Code 9 procedures (revision of metal components). FG had no Code 3 procedures and no Code 9 procedures. In COFAS Type 4 ankle arthritis cases with adjacent hindfoot arthritis undergoing TAA, our data suggests preservation of hindfoot joints yields similar outcomes to fusion of the hindfoot while potentially avoiding greater operative time, immobilization period, and additional wound/hardware risks associated with concomitant hindfoot fusion. However, preservation carries the risk of requiring future reoperation for hindfoot fusion, as seen in 3% of our cases, though this may be countered by the risk of nonunion requiring reoperation when hindfoot fusion is performed primarily. Our results suggest that deferral of hindfoot fusion is a reasonable option in COFAS Type 4 ankles undergoing TAA.