Foot Shape and Asymmetry in the Charcot Foot: Assessment Using the Foot Posture Index.

Abstract

Charcot neuroarthropathy (CN), or the Charcot foot, is a complication usually associated with diabetes that frequently results in changes in foot shape and structure that have an effect on function and risk of ulceration. This study aimed to assess foot shape and asymmetry in CN using the Foot Posture Index (FPI-6). Case notes of patients with CN seen in a diabetic orthotic clinic were reviewed, and available FPI-6 data were analyzed. A comparison group of patients with diabetes without CN was also identified. Groups were compared according to published ranges of foot posture and asymmetry using the Fisher exact test. Twenty-seven patients with CN with 28 affected feet and a comparison group of 27 patients with diabetes only were identified. There was large variation in FPI-6 scores in affected (1 to 12) and unaffected (-1 to 10) feet. Mean scores for affected feet (6.82) and unaffected feet (5.05) differed significantly (P = .005). Considering all FPI-6 scores as positive numbers to indicate mean absolute difference between affected and unaffected feet, CN-affected feet differed by a mean of 3.00 points from unaffected feet. Patients in the CN group were less likely to have asymmetry in the normal range than the comparison group (P = .0146). This study provides new data on foot shape after CN. Patients with CN have feet that are significantly asymmetrical, and the affected foot may be more pronated or supinated. Feet affected by CN are characterized by shape, which is more frequently outside the normal range. The FPI-6 may be suitable for more widespread use in assessment and outcome measurement.