A radiological severity scale to measure the impact of Charcot's Neuroarthropathy: an observational study

Background Charcot's Neuroarthropathy (Charcot foot) is a debilitating and destructive disorder resulting from neurological changes in the foot. Whilst the majority of cases are painless, as a result of disruption to sensory function, a common outcome is severe deformity that impacts considerably on foot function. The purpose of this study was to develop and validate a radiological severity scale to quantify resultant damage from acute mid foot Charcot's. This in turn can be used to evaluate clinical outcomes related to different degrees of offloading. Methods A four round Delphi process was used to develop five tool items. Level of consensus and agreement was set at 80%. Inter-rater and intra-rater reliability was evaluated using 3 raters and 24 plain x-rays of chronic mid-foot Charcot's. Strength of agreement of individual items and overall scores was calculated using weighted Kappa coefficients (S.E). Cronbach's alpha was used to determine internal consistency. Floor (> 15% score 0) and ceiling (> 15% score 11) effects were examined at each time point. Spearman's correlation coefficient was used to assess construct validity using Mobility and Usual Activity scores taken from the EQ-5D-5 L. Results Twenty two patients participated. The five item severity scale demonstrated a Cronbach's alpha of 0.91. Intra-rater Kappa coefficients (SE) for total scores ranged from 0.84 (0.20) to 0.86 (0.20). Inter rater coefficients (SE) ranged from 0.72 (0.14) to 0.83 (0.14). Distribution was normal and no floor or ceiling effects were identified. Conclusion/interpretation This study suggests it may be possible to quantify resultant damage from mid foot Charcot's. Given the physical and emotional impacts from long periods of complete immobilisation defining a minimum standard would be an important development in the management of Charcot foot.