Correction of Lumbosacral Hyperlordosis in Achondroplasia

Abstract

Anterior bulging of the abdomen and posterior protrusion of the buttocks are externally visible deformities reflecting lumbosacral hyperlordosis. Imbalance in pelvic femoral muscles may account for this posture. Despite the clinical significance of hyperlordosis, its surgical treatment has not been well-described. In the current preliminary study, the authors compare two techniques used at the authors' institution for lower limb lengthening, one of which affects the correction of lumbosacral hyperlordosis. Ten patients had bilateral lower extremity lengthening procedures. Seven patients had bilateral tibial lengthening and three patients had combined femoral and tibial lengthening. Ring external fixators were used. Correction of hyperlordosis was assessed by comparing four radiographs with measurements in the sagittal plane obtained preoperatively with those at the latest followup. In the femoral lengthening group, the average preoperative lumbar lordosis angle was 18 degrees, the lumbosacral joint angle was 12 degrees, the sacral inclination angle was 58.3 degrees, and the sacrohorizontal angle was 31 degrees. The mean changes at the latest followup were: lumbar lordosis angle (+1 degree), lumbosacral joint angle (+0.3 degrees), sacral inclination angle (-19 degrees), and sacrohorizontal angle (-15 degrees). In the tibia lengthening group, all parameters were relatively unaltered at the last followup compared with their preoperative levels. Tibial lengthening had no effect on lumbosacral hyperlordosis. However, femoral lengthening resulted in an improved apparent lumbosacral hyperlordosis, although the lumbar lordosis angle was not changed significantly. The change in sacrum tilting provides a likely explanation for the improvement in cosmetic hyperlordosis observed in patients who have had femoral lengthening.