Changes in hip geometry after selective dorsal rhizotomy in children with cerebral palsy

Hip development in children with spastic cerebral palsy (CP) may be different in comparison to that of typical developing children due to impaired motor function and altered lever arms. Selective dorsal rhizotomy (SDR) is known to reduce spasticity. It is postulated that it also improves mobility. Its influence on hip development is unclear. The aim of this study is to evaluate changes in hip geometry before and after selective dorsal rhizotomy.

Conventional radiographs (Rippstein I and II) of 33 ambulatory children aged 2.67 to 11.75 years who underwent SDR were analysed pre- and postoperatively at a mean of 18 months (range 12-29 months). Migration percentage, acetabular index, and anteversion were evaluated. The reduction of spasticity was measured with the modified Ashworth scale. A priori power analysis was performed. As data was normally distributed statistical analysis was performed applying the t-test for paired variables.

Radiographic parameters concerning hip geometry improved significantly after SDR. The spasticity of adductors and hamstrings was significantly reduced through SDR from on average 1.7 to 0.8 on the modified Ashworth scale (p<0.001). The acetabular index decreased from 19° to 17° (p = 0.001), the migration percentage improved from 24% to 21% (p<0.001). Anteversion was also significantly reduced from 41° to 38° (p<0.001). Function improved significantly from 80% to 85% when measured with the GMFM-88 (p<0.001).

The results confirm that SDR improves hip geometry as well as function in ambulatory CP children. Long-term studies need to show whether this radiographic improvement has clinical relevance with regard to pain and function.