Musculoskeletal consequences of spasticity

Dr Taral Nagda
    Paediatric Orthopaedic Surgeon
    Institute for Paediatric Orthopaedic Disorders, Mumbai
    Saifee Hospital
    taralnagda@gmail.com  www.taralnagda.com  9820329888
 

Adverse effects of spasticity

Effects on posture and movements
Spasticity causes difficulty in movement, abnormal posture in sitting and standing, contractures leading to deformities, pressure sores and pain. Increase in tone is uncomfortable. Sitting is difficult for the nonambulatory child because of increased adductor and hamstring muscle tone. The child slides out of the wheelchair and cannot be positioned properly. He cannot transfer to and from the bed, wheelchair and bathtub. Perineal hygiene and dressing the child require more effort. The ambulatory child has trouble initiating movement.He cannot wear his braces. Energy cost of movement increases. Losses of function results and parents have difficulty caring for the child.

Effects on Nerves
- Hyperreflexia because of decreased inhibition form cortical spinal tract.
- increased latency & a decreased ability to recruit large number of motor fibers 

Effects on muscle & tendons
- Spasticity affects muscle growth. Muscles need to be stretched while relaxed; failure to do this results in poor growth
-Spasticity initially causes apparent muscle shortening but the passive range of motion is full. This abnormal permanent resistance is dynamic contracture. If uncorrected, fibrosis and eventually bony deformity lock the joint into a fixed contracture. How fast a contracture will develop depends on the severity of spasticity and the muscles involved: contractures progress more quickly in some muscles.
- In addition to a decreased muscle fiber length, there is a decrease in muscle volume. This is accompanied by changes in motor unit size and changes in fiber type and neuromotor junction type
- Muscles in CP-children-very thin in addition to being short, which means these     muscle are also weak
- Spastic muscle has a great passive strength but low active strength
- Normal movement patterns do not develop. Instead, the child shows abnormal or compensatory movement patterns
- Motor units tend to get larger & have slower responses with longer latency periods combined with a large shift to slow twitch type I fibers
- All these changes mean muscle responds slower during contraction, and combined with changes in nerve has a longer latency period.

Effects on bones









 - Caused by spasticity are modulated by muscular changes.
Bone growth is distorted by the abnormal resistance of the
shortened muscles. Growing bone is easily distorted by
sustained pressure. Untreated spasticity puts excessive
stress on bone that produces abnormal rotation or it inhibits
physiological derotation of long bones. If not relieved at an
early stage, bone deformities occur. Prolonged equinovarus caused by triceps surae and tibialis posterior spasticity might rotate the tibia
inwards. Spasticity of hip adductors can rotate the femur inwards. This inhibits the physiological derotation process of infantile femoral anteversion.

Beneficial effects
Increased tone may be useful for the child. It helps maintain to keep the legs straight, thereby supporting the child’s weight against gravity. The child with increased tone in trunk extensors may stand and take a few steps. Spasticity may help preserve muscle bulk and bone density.