Predictive risk assessment for major amputation after tibiotalocalcaneal arthrodesis

Abstract

Background: Tibiotalocalcaneal (TTC) arthrodesis using a nail has been shown to be an effective salvage technique; however, there is a risk of major amputation. A better understanding of the relative risk of amputation after TTC fusion and the factors that influence this could help the preoperative consultation and guide discussion on the economics of limb salvage.

Methods: One hundred seventy-nine limbs were treated with TTC fusion with an intramedullary nail. A comprehensive chart and radiographic review was pulled from our intramedullary nail database. Patients were divided into those who went on to eventual amputation and those with successful salvage of their limb. Variables from the database were used to build a statistical model with a biostatistician. Final results were presented, and a formula to determine probability of amputation was created.

Results: There were 21 limbs that were eventually treated with major amputation. This represents an overall salvage rate of 88.2% (158/179 patients). Age was a factor in amputation risk, and the highest risk factor for amputation was diabetes with an odds ratio of 7.01 and 95% confidence, P = .0019. The odds of amputation were 6.2 times and 3 times greater for patients undergoing revisions and those with preoperative ulcers, respectively. The probability of amputation could be found preoperatively by using the derived equation: e(x) /(1 + e(x) ) where x is a factor of age, diabetes, revision, and ulceration.

Conclusion: TTC arthrodesis with a retrograde intramedullary nail has a high rate of limb salvage across a wide range of indications and medical comorbidities. In this patient cohort, diabetes was the most notable risk for amputation, followed by revision surgery, preoperative ulceration, and age. A model has been built to help predict the risk of amputation.

Level of evidence: Level II, prognostic.

Keywords: amputation; economics; limb salvage; statistical model.