Midfoot Charcot Neuro-arthropathy Precipitated by First or Fifth ray Amputation

Abstract

Charcot Neuro-arthropathy (CN) can occur spontaneously in a neuropathic foot but is often precipitated by an insult to the foot, such as trauma. We noted an association between 1st and 5th ray amputations and the development of midfoot CN in our clinics. We therefore set out to analyse our data over a 6-year period to evaluate and improve our practice. Our project encompassed all diabetic adults with peripheral neuropathy undergoing an amputation of the first or fifth ray between January 2013 and January 2019. Patient demographics, stump length, progression to CN, imaging reports, the need for further operative management, length of stay and operating specialty were collected. Cases that developed CN after 1st or 5th ray amputation ("CN group") were compared with a cohort composed of patients that did not ("non-CN group"). We identified 92 patients (98 surgical episodes) who had previous 1st or 5th ray amputations [77 males (83.7%), 15 females (16.3%), mean age 61.5 ± 13.5]. Midfoot CN developed in 16 cases (17.4%; nine following 1st ray and seven following 5th ray amputation). This represented 30.9% of all our new CN cases. CN was diagnosed within six months in six cases and up to three years in the remaining 12. Five of the 1st ray amputations were conducted with a stump length of ≤10 mm from the tarsometatarsal joint and a further one had resorbed down to it before the Charcot process. Three of the 5th ray amputations were carried out leaving a stump length ≤25 mm. Receiver Operator Curve (ROC) analysis showed no obvious diagnostic value of stump length in predicting CN (area under the curve 0.42 (95% CI 0.26 - 0.59)). Following a logistic regression analysis into effect of age, gender and peripheral vascular disease, only age was found to significantly affect the risk of developing CN (Nagelkerke R2 = 0.122, p = 0.013). This is the first report of midfoot CN developing after 1st or 5th ray amputations. The foot could be destabilised following these procedures, leading to increased pressures across the midfoot. Our small sample was unable to demonstrate a significant correlation between stump length and CN risk. However, more work is needed to ascertain this. Meanwhile, we believe this translates clinically into a need for enhanced foot protection following 1st and 5th ray amputations in our practice.