Weight-Bearing Intensity Produces Charcot Deformity in Injured Neuropathic Feet in Diabetes

Abstract

The purpose of the study was to investigate the relationship between the intensity of unrestrained weight bearing after a non-fracture injury (e.g. sprain), and the development of osteoarthropathic deformities of the foot (Charcot foot) in patients with diabetic neuropathy. 34 diabetic patients (14 Type 1, 20 Type 2) with foot bone injuries were studied in retrospect. At onset of injury symptoms (e.g. foot swelling), 32 of 34 feet displayed unremarkable X-ray, but pathologic MR imaging (e.g. bone marrow edema along the Lisfranc and/or the Chopart joint). Cumulative load forces after the onset of symptoms until treatment by total contact cast (TCC) were estimated using the product of body weight and number of weeks of ambulation (kg x week) as a surrogate. Feet were classified in 3 groups according to the degree of foot deformities found at the start of treatment with TCC: Feet without deformities (group A, n=16), feet with minor deformities (partially reduced plantar arch (group B, n=6) and feet with major deformities (collapsed plantar arch, group C, n=12) Feet in group A had been exposed to 262 (95% CI 135-390) kg x week, compared to 974 (95% CI 342-1606) in group B, and to 2348 (95% CI 1265-3430) kg x week in group C (p<0.05 between groups), indicative of a dose-response relationship between weight-bearing and progressive foot deformities. Destruction along the Lisfranc joint was observed in 2/16 feet in group A, versus 18/18 feet in group B and C combined (p<0.001). In group A, the undeformed feet were healed without major deformities (except for 2 non-compliant patients), whereas in group B and C feet remained as deformed as they were at TCC application. Unrestrained weight-bearing of injured foot bones and joints of more than 400 kg x week (equivalent to 8 weeks of normal walking by a person of 50 kg body weight) prompts Charcot deformities, with disintegration of the Lisfranc joint. Early off-loading by TCC treatment allows healing without deformities.