Risk factors for conversion of forefoot or midfoot amputations to below knee amputation

Abstract

Background

This study aims to identify risk factors as well as proper indications for forefoot or midfoot amputations at the transmetatarsal, Lisfranc or Chopart level as a potential avenue for distal limb salvage and avoid below knee amputation (BKA).

Methods

This study utilized the PearlDiver national database encompassing 91 million unique patients from 2010 to 3/31/2020 to identify patients who underwent foot amputation (CPT-28800, CPT-28805). The primary endpoint is conversion to BKA within 6 months. Propensity matched cohorts were created using age, gender and common comorbidities. Logistic regression utilizing the matched cohorts determined odds ratios for conversion to BKA based on indication. Indications included abscess, gangrene, osteomyelitis, and diabetic wounds. Analysis was repeated at 1, 2 and five years. Chi-square analysis was used to assess the impact of comorbid peripheral vascular disease (PVD) in a subgroup of patients with osteomyelitis. Time to conversion to BKA was tabulated.

Results

The database identified 17,875 patients who underwent forefoot or midfoot amputation . Conversion to BKA occurred in 2400 patients with median time of 71 days. Logistic regression of the matched cohorts revealed that gangrene was a significant risk factor for conversion to BKA, while osteomyelitis was protective. Subgroup analysis of the osteomyelitis cohort revealed a higher rate of conversion to BKA for patients with concomitant PVD (OR 1.44; P = 0.01).

Conclusion

Based on our data, forefoot or midfoot amputation should be cautiously considered in patients with gangrene or osteomyelitis with concomitant PVD because of a significantly higher rate of conversion to BKA.

Level of evidence

IV.