Plantar Pressure Displacement after Anesthetic Motor Block and Tibial Nerve Neurotomy in Spastic Equinovarus Foot

INTRODUCTION Spastic equinovarus foot is a common deformity that occurs in spastic hemiparesis. The incidence varies between 18 percent [1] and 56 percent [2] 1 yr after stroke. The first-line treatments are physical modalities and injections of botulinum toxin [3]. If this is unsuccessful, surgery involving selective neurotomy of the motor branches of the tibial nerve can be carried out [4-6], with a good long-lasting effect. Most investigators carry out motor nerve blocks prior to surgery [5,7]. Although the importance of preoperative criteria and the evaluation of the clinical and functional effects of treatment are widely accepted [8-9], simple, quantitative measures, which can be used in the real-world setting, have been little evaluated. The few existing studies are based on case series. Bollens et al. carried out a systematic review of the literature and suggested that quantitative, validated analysis tools based on the principles of the International Classification of Functioning and Disability should be developed to evaluate the effect of treatments for spastic equinovarus foot, particularly surgical interventions, on function [10]. Baropodometry is a quite easy-to-use method to evaluate changes in plantar pressure during gait using an inshoe system containing pressure sensors (F-Scan system, Tekscan Inc; South Boston, Massachusetts). This system has been validated for determining pressure distribution under constant conditions [11-12]. This system has provided an objective method for obtaining dynamic recordings of the foot center of pressure (COP) or pressure distribution during stance in nondisabled subjects [13], but also in diabetic patients [14]. Two studies have used this system in hemiparetic subjects [15-16]. Valentini et al. studied three parameters of the displacements of the COP: anteroposterior (AP) displacement, lateral deviation (LD), and posterior margin (PM) of foot contact [17]. In the paretic limb, AP displacement of the COP is shortened, the PM of foot contact is increased, and the LD is reduced [16-17]. These parameters are reliable over time (AP displacement and PM of foot contact), and their coefficient of variability is low (AP for the paretic side and to a lesser degree PM and LD). Clinically, lengthening of the AP displacement of the COP is correlated with an improvement in foot progression. A reduction in the LD could be correlated with less stability or use of assistive device, and a reduction in the PM is correlated with improved heel strike at the beginning of stance phase [16]. We also suggest that AP displacement and the PM could be useful parameters to evaluate the effectiveness of treatments for spastic equinovarus, particularly surgical interventions [17]. The aim of this pilot study was to analyze changes in pressure measurements following motor nerve block and selective tibial neurotomy in adults with spastic equinovarus foot. METHODS This study was carried out in a Regional Center for Physical Medicine and Rehabilitation specializing in neurology. The patients provided informed consent for their participation in the evaluations, the motor nerve block, and surgical intervention. The study was approved by the local ethics committee. Subjects The inclusion criteria were (1) spasticity causing equinovarus foot, with or without varus, on clinical examination; (2) independent gait for at least 70 m, with or without an assistive device; (3) age between 18 and 75 yr; and (4) failure of first-line treatments such as botulinum toxin injection and physical treatments. The exclusion criteria included (1) previous surgery for lower-limb spasticity, (2) contraindications to the anesthetic used for the nerve block or general anesthetic for neurotomy, and (3) use of a rigid ankle-foot orthosis or orthopedic shoe that would prevent the pressure analysis in commercially available shoes. Method Experimental Setup and Protocol Three baropodometric evaluations were carried out: at baseline, post-block (following motor block of the gastrocnemii nerve) and post-surgery (after selective tibial nerve neurotomy, and additional surgery if necessary). …