Mechanical and Neurophysiological Changes in Spastic Muscles: Serial casting in spastic equinovarus following traumatic brain injury

Abstract

Equinovarus is the most common deformity associated with hypertonicity of the antigravity muscles in traumatic brain injury. Casting is a technique that has been used for several years in the management of spastic equinovarus. This article reviews some of the main theories on the mechanical and neurophysiological changes in muscle structure and function in the presence of spasticity. The mechanical theories reviewed are those of abnormal cross-bridge attachments; increase in sarcomere numbers; and changes in connective tissue. The neurophysiological theories examined are hyperreflexia; loss of presynaptic inhibition and normal sensory input; and reflexes induced by tactile stimulation. As each theory is discussed, hypotheses are made as to why serial casting of equinovarus deformity may have an effect on spasticity. These hypotheses are then related to evidence within literature which might support or refute each hypothesis. This review concludes that evidence indicates that in spastic equinovarus deformity both mechanical and neurophysiological factors may be involved, and that serial casting may influence the spasticity on both a mechanical and a neurophysiological basis. Equinovarus is the most common deformity associated with hypertonicity of the antigravity muscles in traumatic brain injury. Casting is a technique that has been used for several years in the management of spastic equinovarus. This article reviews some of the main theories on the mechanical and neurophysiological changes in muscle structure and function in the presence of spasticity. The mechanical theories reviewed are those of abnormal cross-bridge attachments; increase in sarcomere numbers; and changes in connective tissue. The neurophysiological theories examined are hyperreflexia; loss of presynaptic inhibition and normal sensory input; and reflexes induced by tactile stimulation. As each theory is discussed, hypotheses are made as to why serial casting of equinovarus deformity may have an effect on spasticity. These hypotheses are then related to evidence within literature which might support or refute each hypothesis. This review concludes that evidence indicates that in spastic equinovarus deformity both mechanical and neurophysiological factors may be involved, and that serial casting may influence the spasticity on both a mechanical and a neurophysiological basis.