Sagittal Spinopelvic Parameters in Children With Achondroplasia

Study design: Retrospective cross-sectional, longitudinal radiographic analysis.

Objective: To report the natural history of spinopelvic parameters in achondroplasia.

Summary of background data: Sagittal spinal deformity is common in children with achondroplasia. However, few data exist on their normative spinal parameters.

Methods: Lateral standing spine radiographs of children with achondroplasia were reviewed. Measurements included thoracic kyphosis, lumbar lordosis (LL), thoracolumbar kyphosis (TLK), pelvic incidence (PI), T1 pelvic angle (TPA), and sagittal balance (SVA). Comparison between age groups and longitudinal analysis of children with minimum five-year radiographic evaluation was performed; evolution of radiographic measurements was assessed. Children who underwent surgical correction of TLK were studied separately to describe changes of sagittal spinal parameters associated with TLK surgical correction.

Results: In cross-sectional analysis, 745 radiographs (282 children) were measured. During the first three years, TLK decreased and LL and sacral slope increased significantly. After age 3 years, TLK decreased gradually until age 10. Afterwards, TLK decrease became non-significant. PI increased gradually after age 10. In the longitudinal group, 81 children were followed an average of 8.7 (5-19) years between age 4.4 and 13.1 years. TLK decreased; LL and PI increased significantly. TPA and SVA remained within the normal range although changes with growth were statistically significant. In the surgical group, 19 children underwent surgical TLK correction. Apart from TLK correction, no sagittal parameters changed significantly after surgery. These 19 children had higher TLK and lower LL compared with a nonsurgical group at similar average age.

Conclusion: In children with achondroplasia, TLK improvement occurs primarily before age 3 years; hyperlordosis at the lumbosacral level is the compensatory mechanism. Significant changes in the sagittal spinal parameters occur early in life, suggesting the importance of attention to sagittal malalignment to prevent any possible clinical sequelae of severe hyperlordosis.

Level of evidence: Level III, prognostic study.