Subtalar fusion with previous Ipsilateral Ankle Arthrodesis: an entity to look for

Y. Elhassan, A. Jamjoom, A. Lomax, N. Tellisi

Introduction: Isolated subtalar arthrodesis is a commonly performed procedure that produces a high fusion rate. It is suggested that the fusion rate of subtalar arthrodesis is negatively affected by the presence of pre-existing ipsilateral ankle (tibiotalar) arthrodesis, though the mechanism by which this occurs remains unclear.The aim of this study is to assess subtalar arthrodesis fusion rate in the presence of pre-existing ipsilateral ankle arthrodesis and to suggest alternative operative techniques to improve fusion rates.

Methods: We retrospectively studied electronic patient records and images who underwent primary isolated subtalar arthrodesis were identified between (2009-2019). Two groups, those with and without previous ipsilateral ankle arthrodesis were compared. Factors affecting fusion rate including body mass index (BMI), smoking status, and co-morbidities such as diabetes and rheumatoid arthritis were studied.

Results: A total of one hundred and thirty-three (n=133) primary isolated subtalar arthrodesis were identified between (2009-2019), amongst which twenty-one (n=21) had pre-existing ipsilateral ankle arthrodesis. Ten (n=10) recorded subtalar non-unions occurred in the pre-existing ankle arthrodesis group representing a non-union rate of 47.6%, as opposed to sixteen(n=16)  in the isolated subtalar fusion group without pre-existing ipsilateral ankle arthrodesis group representing a non-union rate of only 13.1% (P = .001). Age, Body mass index (BMI), smoking status, diabetes, and rheumatoid arthritis were found not to have a significant effect on these results.

Conclusion: Our results show a significantly higher non-union rate of isolated subtalar arthrodesis in the presence of pre-existing ipsilateral ankle arthrodesis. Further research is required to help in clarifying the mechanism by which this effect occurs and to study alternative operative techniques that might be required.