Standing Frames And The Factors Contributing To The Risk Of Hip Dislocation

Children at greatest risk of hip dislocation are

  • those who are in persistent postures with a high degree of hip adduction and little voluntary movement
  • those who were delayed in functional weight bearing – 25-30% of children who cannot sit independently
  • those who cannot ambulate – Vidal (1985) showed that the mean increase in MP per year was 4% in those children with potential for walking whereas it was 7% for those with no potential for walking.
  • Those who do not weight bear – less than 2% of children who can pull to stand before the age of three years have hip subluxation or dislocation (Scrutton 1993). Those that never pull to stand have a much higher rate of dislocation (18.5 per cent compared to 5.4). (Scrutton 1989)

Pelvic obliquity develops because of abnormalities in the position of the hip and imbalances in muscle pull on the pelvis. Creep occurs due to constant loading over a prolonged period of time. Ligaments and muscles shorten and thicken on the concave side and stretch and relax on the convex side. Cartilage on the concave side degenerates because of heavy compression and atrophies on the convex side because of stress reduction. Intervertebral disks lose their ability to maintain normal vertebral dynamics. The consequences of these changes include reduced range of motion, pain, functional limitation.

Migration percentage:

Migration percentage (MP) is the most commonly used measurement of hip status in children with CP. MP indicates the amount of ossified femoral head uncovered by the ossified acetabular roof and indicates hip stability.



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