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Hip in Myelomeningocele

- 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 
    - 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 
                  - 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 
             - 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.

The effect of hip reduction on function in patients with myelomenigocele: Potential gains and hazards of surgical treatment.