Does a shorter residual first metatarsal length after first ray amputation in diabetic patients leads to poorer outcomes - A risk factor study.

Background: The first ray plays a vital role in the normal function of the foot and the gait cycle where in its absence can lead to abnormal changes in weight distribution to the residual first metatarsal stump and lesser metatarsals with predisposition to developing lesser toe deformities reulcerations and reamputations particularly in diabetic patients. This study aims to characterise the outcomes after first ray amputation and its associated risk factors with focus on the impact of residual first metatarsal length.

Methods: All diabetic patients with first ray amputations from January 2012 to December 2016 were reviewed. Residual first metatarsal length was measured using postoperative radiographs. Risk factors for outcomes such as readmission, reulceration and/or reamputation, transfer ulceration and/or amputation of lesser toes, proximal amputations, ulcer-free duration (UFD) and mortality were analysed using bivariate logistic/linear regression followed by multiple logistic/linear regression models adjusting for confounding factors.

Results: Among 89 patients with first ray amputations, 65.3 % needed readmission for further treatment. Although only 10.1 % had reulceration at the first ray which all led to reamputation, there were 56.2 % with transfer ulceration and 40.4 % with transfer amputation of the lesser toes in this cohort. The prevalence of transmetatarsal amputation was 18 % and proximal amputations at 12.4 % while the average UFD was 27 months. Mortality rate was 31.5 % with an average of 3-year survival. Preservation of the first metatarsal length via metatarsophalangeal joint disarticulation independently reduced likelihood of readmissions and residual metatarsal length of > one third when compared to < one third after first ray amputations had lower likelihood of transfer amputation of lesser toes.

Conclusion: First ray amputation in diabetic patients leads to significant morbidities and mortality. Preservation of the residual first metatarsal length independently reduced the likelihood of readmissions and transfer amputation to the lesser toes.