HIP REPLACEMENT IN CHILDREN: WHAT HAPPENS TO THE HIP JOINT?

Abstract

Between 1982 and 1997, twenty-six children between the age of 2 and 15 (mean age 10. 6 years) underwent proximal femoral replacement. Twenty have survived and all but three have reached skeletal maturity.

Sequential radiographs have been reviewed with particular reference to acetabular development and fixation of the prostheses. Initially a cemented acetabular component was inserted, but recently uncemented implants and unipolar femoral heads that exactly fit the acetabulum have been used.

In older children the acetabulum develops normally and the components remain well fixed. One of nine children over thirteen years with a cemented acetabulum needed revision for loosening and one suffered recurrent dislocations.

In younger children the acetabulum continues to develop at the triradiate cartilage, so a cemented acetabulum grows away from the ischiopubic bar. As the component is fixed proximally, it becomes increasingly vertical and will almost inevitably loosen. In our study six of eight children under 13 years of age with a cemented acetabulum needed revision for loosening.

Unipolar replacements in younger children tend to erode the superior acetabular margin. Femoral head cover is difficult to maintain, and of four unipolar implants in children under thirteen, two required acetabular augmentation.

Cemented cups may be unsuitable for children under thirteen years but our results are not statistically significant. In this age group, unipolar implants may be more appropriate but they have serious potential complications. In children over thirteen, cemented implants survive longer. The number of uncemented implants in our study is too small to comment on long-term survival.