- Dislocation of Hip:
- hip dislocation in children w/ myelomeningocele may either teratological or paralytic (which is due to muscle imbalance);
- paralytic dislocation:
- hip dislocation occurs because of paralysis of the hip abductors and extensors w/ unopposed hip flexors and adductors;
- in the past, hip dislocation was thought to be most common at the L3-L4 level,however, some argue that dislocation more common
w/ high level lesions;
- note that w/ an L4 lesion there will be paralysis of the gluteus medius and gluteus maximus w/ preservation of the psoas and the
adductor longus;
- if subluxation is not treated, it eventually causes dislocation of hip;
- dislocated hips do not appear to have any relation to ability to walk and rarely cause pain;
- asymmetry of the pelvis will adversely affect walking ability;
- inability to walk is directly related to:
- level of paralysis;
- presence of syringomyelia;
- Arnold-Chiari malformation
- scoliosis
- function of the upper extremities;
- age of patient;
- Treatment Goals:
- basic premises:
- painless dislocated hip is preferable to stiff, painful, reduced hip;
- dislocated hips in the child unable to walk require no treatment;
- aim of surgery is to maintain ROM & achieve full hip extension;
- containment of hip is a secondary concern;
- thoracic or upper lumbar lesion:
- exam: w/ grade 2 quad function, pt's paralysis level is high lumbar;
- w/ both hips unstable, most agree no treatment is indicated;
- anterior hip release for hip flexion contractures may be necessary;
- attempt to prevent contractures that will interfere w/ walking in a HKAFO during the first ten years of life;
- this can usually be accomplished w/ PT & positioning;
- thereafter, most of these pts use wheelchair full time;
- muscle transfers alone usually are not effective in producing stability of hip in children who have lesion at L1 or L2 should not
be done;
- low lumbar lesion:
- reduction of hips is indicated for prevention of progressive subluxation which will ultimately interfere w/ of walking;
- w/ L4 or lower lesion, reduce hips and perform varus and or Pemberton osteotomy to avoid future leg length discrepancy or pelvic
obliquity;
- hip flexion contracture:
- fixed flexion deformity of the hip may interfere w/ fitting of standing frame, parapodium, or reciprocating gait orthosis;
- Indications for Reduction:
- child who walks;
- unilateral dislocation;
- age: one & three years;
- stable neurological status at L3 or L4;
- children w/ strong quads &, esp, those w/ functional hamstrings may benefit from surgical correction of subluxating or dislocated hips;
- Contra-indications for Reduction:
- bilateral teratological dislocation;
- dislocated hips in the child unable to walk require no treatment;
- Soft-tissue procedures seek to balance muscle forces;
- Sharrard procedure:
- involves transfer of iliopsoas to greater trochanter;
- alternative procedure: transfer of external oblique muscle combined with adductor tenotomy or transfer of adductors to the
ischium;
- indications:
- lower-level lesion;
- no function of abductors & extensors of hip;
- good potential for walking;
- balancing of muscle forces involves a combination of lengthening or transfer of iliopsoas, external oblique, rectus femoris, sartorius, &
tensor fasciae latae muscles;
- tenotomy of iliopsoas & adductor muscles may relieve the muscle balance about the hip, but will severely weaken it;
- this results in decreased walking ability and may require extending brace above the hip;
- Osseous procedures seek to correct deficiency of acetabulum as well as to correct center the femoral head in the acetabulum;
- Shelf procedure, Pemberton osteotomy, or Chiari osteotomy may be used for correction of deficiency of the acetabulum;
- of note, a Salter osteotomy would be a poor choice for a paralytic posterior dislocation, since this type of osteotomy provides
anterior coverage at the expense of posterior coverage;
- femoral osteotomy should be performed to correct rotational & angular deformity, with care being taken to avoid too much varus
angulation;
- although it is possible to carry out open reduction and provide temporary stability to the hip with the varus osteotomy, capsule will
stretch out w/ redislocation of hip unless muscle forces around hip can be balanced
The natural history of hip deformity in myelomeningocele.
Walking ability after transplantation of the iliopsoas: A long term follow-up.
Effectiveness of muscle transfer in myelomeningocele hips measured by radiographic indices.
Ambulation in patients with myelomeningocele: A multivariate statistical analysis.