The Fate of the Neuromuscular Hip After Spinal Fusion

The goals of treatment of neuromuscular scoliosis are to achieve a balanced spine and level pelvis with most constructs including pelvic fixation. However, the pelvis can become a stiff "end vertebra" that prevents compensatory mechanisms to adjust to hip deformities in this patient population. The purpose of this study is to determine the frequency of hip pathology and surgery after spinal fusion in this patient population.

We performed a retrospective chart and radiographic review of cerebral palsy patients who underwent posterior spinal fusion (PSF) at our institution from 2005 to 2011. We collected radiographic data of preoperative and postoperative pelvic obliquity and hip reduction status and position (up, level, down). We further evaluated patients requiring hip surgery (containment or salvage).

Of 47 patients with an average follow-up of 3.5 years after spinal fusion, 21 (45%) underwent a hip procedure. Thirty-eight patients (81%) demonstrated or developed hip subluxation/dislocation. Hip pathology occurred more often in the up hip, but the pathologic down hip more often underwent a hip surgery. Eight new hip subluxation/dislocations occurred after spine surgery. Three (38%) of the new postoperative subluxation/dislocations required hip surgery; all had pelvic obliquity <6 degrees. Eleven patients underwent hip surgery before PSF, 7 were varus femoral osteotomies for subluxation, whereas 5 hips required salvage. In follow-up after PSF, none of these had a new dislocation. Ten patients required hip surgery after PSF at a mean of 1.6 years after PSF. Eight patients had a salvage procedure for painful hip and 2 varus femoral osteotomies for subluxations.

In our cerebral palsy patients who underwent PSF, 45% of these patients required a hip procedure. In the patients who had containment before PSF, the hips maintained reduction after spinal fixation. After correction of pelvic obliquity, 17% of patients had new-onset hip subluxation/dislocation after PSF. Postoperative subluxation/dislocation was not dependent on whether the hip was up or down preoperatively.

IV, Retrospective.