Abstract
Chronic stroke survivors with spastic hemiplegia have various clinical presentations of ankle and foot muscle spasticity patterns. They are mechanical consequences of interactions between spasticity and weakness of surrounding muscles during walking. Four common ankle and foot spasticity patterns are described and discussed through sample cases. The patterns discussed are equinus, varus, equinovarus, and striatal toe deformities. Spasticity of the primary muscle(s) for each deformity is identified. However, it is emphasized that clinical presentation depends on the severity of spasticity and weakness of these muscles and their interactions. Careful and thorough clinical assessment of the ankle and foot deformities is needed to determine the primary cause of each deformity. An understanding of common ankle and foot spasticity patterns can help guide clinical assessment and selection of target spastic muscles for botulinum toxin injection or nerve block.
1. Introduction
About 80% of chronic stroke survivors have varying degrees of abnormal gait and impaired locomotion capability [1]. Spasticity in the ankle and foot muscles is very common, and often results in various ankle and foot deformities, including equinus, varus, equinovarus, and striatal toe deformities. The spastic equinovarus deformity is the most common deformity seen [2,3,4]. An ankle and foot joint abnormality could have subsequent effects on the knee, hip, and trunk position and control in post-stroke hemiplegic gait through a kinetic chain effect. For example, an equinovarus deformity shifts the ground reaction force anterior to the knee joint, and thus facilitates knee (hyper)extension during the stance phase. Stroke survivors are often forced to increase hip extension to compensate for knee (hyper)extension to keep the center of gravity within the forefoot. During the swing phase, increased knee and hip flexion is required to clear the equinovarus foot from the floor. However, they are often unable to do so due to weak hip and knee flexors, and, instead, present with hip hiking and leg circumduction. Additionally, stroke survivors have a smaller base of support due to the equinovarus deformity. The stance phase is shortened to minimize the risk of fall. Therefore, the ankle and foot deformity is often associated with kinetic and kinematic gait abnormalities, such as gait asymmetry, slow speed, genu recurvatum, etc [3,5].Joint abnormalities in the hip, knee, ankle, and foot joints observed in post-stroke hemiplegic gait are mechanical consequences of the interactions among muscle spasticity, weakness, and disordered motor control during locomotion [6]. Depending on the severity of spasticity and weakness of muscles surrounding a joint, various joint abnormalities can develop. The complex ankle and foot anatomy contribute directly to observed deformities. As shown in Figure 1, four groups of muscles (invertors, evertors, dorsiflexors, and plantarflexors) act on the ankle–foot complex. Any isolated ankle movement is a net result of the combined activation of a group of target muscles, e.g., inversion occurs when dorsiflexors (primarily the tibialis anterior muscle) and plantarflexors (primarily the tibialis posterior muscle) co-activate. In the presence of spasticity, stroke survivors have less control and isolated activation; activation is more diffuse and divergent [7,8]. Therefore, a variety of ankle–foot deformities could be observed, depending on the severity of spasticity and weakness of individual muscles.
Among the spectrum of treatment options for ankle and foot deformities and gait disorders, interventions such as botulinum toxin (BoNT) injection and phenol neurolysis are commonly used to manage spasticity of the ankle and foot muscles [2,4,11,12]. To achieve the best clinical outcomes, it is important to identify the primary causes of the deformity. Based on the assessment from instrumented gait analysis, BoNT treatment for spasticity of target muscles has shown to improve gait pattern and walking speed [13,14,15]. However, an instrumented gait analysis lab is not available in most clinics and it is not practical to perform a computer assisted gait analysis for every patient. Understanding common ankle and foot spasticity patterns is helpful to guide our clinical assessment and development of a treatment plan. These common ankle and foot spasticity patterns are presented here through sample cases. In all cases, no significant component of contracture was detected. The common ankle and foot spasticity patterns include: equinus, varus, equinovarus, and striatal toe.[…]
TBI Rehabilitation 