Editorials

Reconstruction of dislocated hips in children with cerebral palsy

Is difficultand in many cases could be prevented by regular monitoring 

Children who suffer from cerebral palsy and do not walk before the age of 5 have a 58% incidence of hip dislocation (44% bilateral, 14% unilateral).¹ Other factors involved in the causation of hip dislocation include four limb cerebral palsy² and tightness of the adductor and iliopsoas muscles with concomitant weakness in the abductor muscles at the hip.³ Whatever the cause, reconstructing the hip in these children involves complex surgery, and parents and their doctors need to be aware that management is not straightforward.

Investigations used to detect dislocation include x rays of the pelvis and whole spine; from the former the physician or surgeon can document any progressive tendency of the hip to dislocate by measuring the migration percentage.⁴ Such monitoring is important. Associated radiological features of hip dislocation are femoral neck anteversion, valgus femoral neck shaft angles, and acetabular dysplasia.

If a child over the age of 5 has a migration percentage of the hip greater than 40% the time for soft tissue surgery alone has almost certainly passed.⁵ Hip reconstruction after dislocation is in effect a salvage procedure. It involves anatomical correction of bony abnormalities in the femur and acetabulum, with shortening of the femur to allow the femoral head to be relocated in the acetabulum. Tethers to the femur, with the inevitably tight pubofemoral ligament and the adductor and psoas muscles, will have to be cut to allow relocation of the femoral head. The acetabulum itself must be cleared of all fibrous, fatty, and ligamentous tissue, and during the operation a decision will need to be made regarding pelvic osteotomy or acetabuloplasty. Chronic damage to the femoral head may be noted during operation and this includes either flattening of the whole head or grooving or pitting of the articular cartilage.

Just as important as the surgery itself is the preoperative and postoperative preparation of the child and parents. A team consisting of an orthopaedic surgeon, a paediatric neurologist, a senior physiotherapist, and a skilled orthotist needs to be involved, and it helps families to meet a member of the ward staff, the play leader, and the clinic coordinator before surgery. The final preoperative assessment, which takes place in a preadmission setting, must ensure that any feeding difficulties, muscle spasm, recurrent respiratory infections, and epilepsy are all sufficiently well controlled to allow major surgery to go ahead. It is at this stage that all aspects of discharge arrangements into the community should be addressed.

If there is one issue that perhaps dominates all others for the parents, however, it is worry about how their child will cope with postoperative pain. The effective use of a paediatric pain relief team is absolutely vital. Postoperative muscle spasm can only add to a child's discomfort when he or she is being nursed in, for example, a hip spica, and starting baclofen preoperatively will help. Parents need to be aware, before the operation, of the difficulties associated with managing their child in a plaster spica, the care of a urinary catheter, and the use of suitable incontinence pads.

We know that a painful dislocated hip in young adults is practically untreatable.⁶ We also know that, apart from premature degenerative change in the femoral head, scoliosis and pelvic obliquity may occur with a longstanding hip dislocation. Hip reconstruction has, however, a complication rate, with 5% of hips redislocating²; the reported incidence of avascular necrosis of bone varies from 0%⁷ to 23%⁸ of cases. After a successful hip reconstruction quality of life will improve, and patients can sit with greater stability or walk greater distances after a period of rehabilitation. A substantial improvement in hip pain can be expected in most cases. It is now apparent that some children have for years been suffering pain in the hip, unknown to their parents and carers because of communication difficulties.

Hip reconstructive surgery for children with cerebral palsy is a major undertakingfor the children themselves, their parents, and the few centres that offer this operation in the United Kingdom. Monitoring cannot prevent all cases of hip dislocation, but the prime objective of all concerned in managing these children must be to try to prevent progressive asymmetry of the hips and spine.

J D Spencer, Reader. 

Department of Trauma and Orthopaedics, Guy's and St Thomas's Hospital Trust, London SE1 9RT

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