toxins Communication Ankle and Foot Spasticity Patterns in Chronic Stroke Survivors with Abnormal Gait Sheng Li 1,2,* 1 Department of Physical Medicine and Rehabilitation, McGovern Medical School, University of Texas Health Science Center, Houston, TX 77030, USA 2 TIRR Memorial Hermann Research Center, TIRR Memorial Hermann Hospital, Houston, TX 77030, USA Received: 9 September 2020; Accepted: 2 October 2020; Published: 7 October 2020 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. Keywords: spasticity; gait; stroke; botulinum toxin; nerve block Key Contribution: The article describes and discusses four common ankle and foot deformities after stroke. Understanding these common presentations 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 [2–4]. 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 Toxins 2020, 12, 646; doi:10.3390/toxins12100646 www.mdpi.com/journal/toxins Toxins 2020, 12, x FOR PEER REVIEW 2 of 9 Toxins 2020, 12, 646 2 of 9 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 surroundingand foot anatomy a joint, contribute various jointdirectly abnormalities to observed can deformities develop.. TheAs shown complex in ankleFigure and 1, four foot groups anatomy of contributemuscles (invertors, directly to evertors, observed dorsiflexors deformities., and As shownplantarflexors) in Figure act1, four on the groups ankle of– musclesfoot complex. (invertors, Any evertors,isolated ankle dorsiflexors, movement and is plantarflexors) a net result of act the on combined the ankle–foot activation complex. of a Anygroup isolated of target ankle muscles, movement e.g., isinversion a net result occurs of the when combined dorsiflexors activation (primarily of a group the oftibialis target anterior muscles, muscle) e.g., inversion and plantarflexors occurs when dorsiflexors(primarily the (primarily tibialis posterior the tibialis muscle) anterior co muscle)-activate. and In plantarflexors the presence (primarilyof spasticity, the stroke tibialis survivors posterior muscle)have less co-activate. control and Inisolated the presence activation; of spasticity,activation strokeis more survivors diffuse and have divergent less control [7,8]. andTherefore, isolated a activation;variety of activationankle–foot is deformities more diffuse could and divergentbe observed, [7,8]. depending Therefore, aon variety the severity of ankle–foot of spasticity deformities and couldweakness be observed, of individual depending muscles. on the severity of spasticity and weakness of individual muscles. Figure 1. The muscles involved in ankle movement. EHL: extensor hallucis longus; EDL: extensor Figure 1. The muscles involved in ankle movement. EHL: extensor hallucis longus; EDL: extensor digitorum longus; FHL: flexor hallucis longus; FDL: flexor digitorum longus; Gastroc: gastrocnemius. digitorum longus; FHL: flexor hallucis longus; FDL: flexor digitorum longus; Gastroc: gastrocnemius. Note: Tendons of the soleus and gastrocnemius merge and form the Achilles tendon. The soleus tendon Note: Tendons of the soleus and gastrocnemius merge and form the Achilles tendon. The soleus is located in the medial portion of the Achilles tendon, thus contributing more to inversion, while the tendon is located in the medial portion of the Achilles tendon, thus contributing more to inversion, gastrocnemius tendon forms the lateral portion and contributes more to eversion. They plantarflex the while the gastrocnemius tendon forms the lateral portion and contributes more to eversion. They ankle joint when acting together [9,10]. plantarflex the ankle joint when acting together. [9,10]. Among the spectrum of treatment options for ankle and foot deformities and gait disorders, interventionsAmong the such spectrum as botulinum of treatment toxin (BoNT) options injection for ankle and and phenol foot neurolysis deformities are and commonly gait disorders, used to manageinterventions spasticity suchof as the botulinum ankle and toxin foot (BoNT) muscles injection [2,4,11,12 and]. Tophenol achieve neurolysis the best are clinical commonly outcomes, used it to is importantmanage spasticity to identify of thethe primaryankle and causes foot ofmuscles the deformity. [2,4,11,1 Based2]. To onachieve the assessment the best clinical from instrumented outcomes, it gaitis important analysis, BoNTto identify treatment the forprimary spasticity causes of target of the muscles deformity. has shown Based to on improve the assessment gait pattern from and walkinginstrumented speed gait [13 –analysis,15]. However, BoNT antreatment instrumented for spasticity gait analysis of target lab muscles is not available has shown inmost to improve clinics andgait itpattern is not and practical walking to perform speed [1 a3 computer–15]. However, assisted an gaitinstrumented analysis for gait every analysis patient. lab Understandingis not available commonin most clinics ankle andand footit is spasticitynot practical patterns to perform is helpful a computer to guide our assisted clinical gait assessment analysis for and every development patient. ofUnderstanding a treatmentplan. common These ankle common and foot ankle spasticity and foot patterns spasticity is helpful patterns to guide are presented our clinical here assessment through sampleand development cases. In all ofcases, a treatment no significant plan. These component common of ankle contracture and foot was spasticity detected. patterns The common are presented ankle andhere footthrough spasticity sample patterns cases. include:In all cases, equinus, no significant varus, equinovarus, component and of contracture striatal toe. was detected. The common ankle and foot spasticity patterns include: equinus, varus, equinovarus, and striatal toe. 2. Common Deformities 2. Common Deformities 2.1. Equinus (Plantar Flexion) 2.1. Equinus (Plantar Flexion) An equinus ankle and foot deformity in stroke survivors with spasticity is a condition where the ankleAn and equinus foot isheld ankle in and the plantarflexedfoot deformity position, in stroke and survivors there is diwithfficultly spasticity with voluntaryis a condition dorsiflexion where the of theankle ankle. and foot This is is held primarily in the causedplantarflexed by spasticity position, of theand ankle there plantarflexors is difficultly with (gastrocnemius voluntary dorsiflexion and soleus muscles)of the ankle. with This or without is primarily toe flexor caused spasticity. by spasticity Figure2 ofshows the ankle a 65-year-old plantarflexors female stroke(gastrocnemius survivor with and asoleus spastic muscles) equinus with ankle or and without foot deformity toe flexoron spasticity the right. Figure side, due 2 shows to a left a basal65-year ganglia-old female hemorrhage stroke fromsurvivor hypertension