Can we predict outcome of surgical reconstruction of Charcot neuroarthropathy by dynamic plantar pressure assessment?--A proof of concept study.

The joint deformity that arises as a result of Charcot neuroarthropathy, leads to gait modification. Ulceration risk associated with the deformity is generally assessed by measuring plantar pressure magnitude (PPM). However, as PPM is partially dependent on gait speed and treatment interventions may impact speed, the use of PPM to validate treatment is not ideal. This study suggests a novel assessment protocol, which is speed independent and can objectively (1) characterize abnormality in dynamic plantar loading in patients with foot Charcot neuroarthropathy and (2) screen improvement in dynamic plantar loading after foot reconstruction surgery. To examine whether the plantar pressure distribution (PPD) measured using EMED platform, was normal, a customized normal distribution curve was created for each trial. Then the original PPD was fitted to the customized normal distribution curve. This technique yields a regression factor (RF), which represents the similarity of the actual pressure distribution with a normal distribution. RF values may range from negative 1 to positive 1 and as the value increases positively so does the similarity between the actual and normalized pressure distributions. We tested this novel score on the plantar pressure pattern of healthy subjects (N=15), Charcot patients pre-operation (N=4) and a Charcot patient post-foot reconstruction (N=1). In healthy subjects, the RF was 0.46+/-0.1. When subjects increased their gait speed by 29%, PPM was increased by 8% (p<10(-5)), while RF was not changed (p=0.55), suggesting that RF value is independent of gait speed. In preoperative Charcot patients, the RF<0, however, RF increased post-surgery (RF=0.42), indicating a transition to normal plantar distribution after Charcot reconstruction.