What causes deformity in cerebral palsy?
a.The spastic muscles are not able to relax and cuase unequal muscle forces leading to dynamic deformities.
b.The muscles under tension can not grow as well as the normal muscles This causes relative shortening of muscles and fixed contractures (secondary deformity)
c. As the child’s age advances there are secondary contractures in joints and rotational deformities in bones which cause lever arm dysfunction (tertiary deformities)
What is lever arm dysfunction?
Disruption in the moment generation of a muscle joint complex because of an ineffective lever or moment arm despite normal muscle force. Four types of lever arm dysfunction are described by Gage: malrotation, loss of a stable fulcrum, loss of bony rigidity, and lever arm shortening. The result of lever arm dysfunction is functional weakness and decreased power production
How does one assess the extent of the deformities
a. The amount of spasticity and muscle shortening is assessed by tardeau scale
b. The amount of bony and joint deformities is assessed by clinical evaluation, xrays and CT scan
How do we decide appropriate treatment for CP patients
a. Small children where spasticity is an issue and who do not have contractures or muscle shortening. The spasticity is controlled with therapy, splints and botulinum toxin injection
b. Children in age group 4-6 years with spasticity and muscle shortening: We treat them with a combined approach spasticity is treated with botulinum toxin injection and the shortening is treated with PAS (percutaneous aponeurotic slide). PAS is a percutaneous minimally invasive surgery where muscle covering is incised with a special needle to elongate the muscles yet retaining the power. The lower limbs are immobilised in plaster cast for 2 weeks sfter the procedure and then exercises started. The advantage of the procedure is that there are no stitches or scars, the procedure takes a short time of anaesthesia, the muscle healing is faster, The muscle power is retained and the need for repeated injections is avoided.
c. the children with lever arm disorders need single event multilevel surgery with percutaneous bony osteotomies to correct the angulation and rotation along with multilevel aponeurotic releases. the advantage of percutaneous bony osteotomies again is shorter healing time, smaller scars and early recovery.
