The sagittal balance of the spine in children and adolescents with osteogenesis imperfecta.

In severe forms of osteogenesis imperfecta, multiple compression fractures of the spine, as well as vertebral height shortening could be responsible for an increased thoracic kyphosis or a diminished lumbar lordosis. Theses progressive changes in sagittal shapes of the trunk could be responsible for a global sagittal trunk imbalance. We compare the parameters of sagittal spinopelvic balance in young patients with OI to those parameters in a control group of healthy volunteers. Eighteen patients with osteogenesis imperfecta were compared to a cohort of 300 healthy volunteers. A standing lateral radiograph of the spine was obtained in a standardized fashion. The sacral slope, pelvic tilt, pelvic incidence, lumbar lordosis, thoracic kyphosis, T1 and T9 sagittal offset were measured using a computer-assisted method. The variations and reciprocal correlations of all parameters in both groups according to each other were studied. Comparison of angular parameters between OI patients and control group showed an increased T1T12 kyphosis in OI patients. T1 and T9 sagittal offset was positive in OI patients and negative in control group. This statistically significant difference among sagittal offsets in both groups indicated that OI patients had a global sagittal balance of the trunk displaced anteriorly when compared to the normal population. Reciprocal correlations between angular parameters in OI patients showed a strong correlation between lumbar lordosis (L1L5 and L1S1) and sacral slope. The T9 sagittal offset was also strongly correlated with pelvic tilt. Pelvic incidence was correlated with L1S1 lordosis, T1 sagittal offset and pelvic tilt. In OI patients, the T1T12 thoracic kyphosis was statistically higher than in control group and was not correlated with other shape (LL) or pelvic (SS, PT or PI) parameters. Because isolated T1T12 kyphosis increase without T4T12 significant modification, we suggest that vertebral deformations worsen in OI patients at the upper part of thoracic spine. Further studies are needed to precise the exact location of most frequent vertebral deformities.