Sagittal Alignment of the Spine and Pelvis During Growth

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• a - Medtronic Sofamor Danek, Strategic Training Grant (Canadian Institute of Health Research), Fondation de Recherche et d’Education en Orthopedie de Montreal

Purpose: The purpose of this study was to document sagittal alignment of the spine and pelvis as well as changes in these parameters during growth in the normal pediatric population.

Methods: Standing lateral radiographs of 180 children with negative clinical and radiographic examinations were studied prospectively. There were 68 males and 112 females, with mean age 12, range 3-18 years old: Custom computer software was used to assess thoracic kyphosis (TK), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT) and pelvic incidence (PI). Statistical analysis was performed using two-tailed Student t tests and Pearson’s coefficients (level of significance = 0.01). Mean TK, LL, SS, PT and PI values were 43.0°, 48.5°, 41.2°, 7.2° and 48.4°, respectively. Smaller values for all parameters were observed in children younger than 10 years old when compared to subjects aged 10 years or older (Table 1). TK, LL, PI and PT correlated weakly with age, while SS remained stable with growth. There was no significant difference between males and females.

Summary:This study documents sagittal alignment of the spine and pelvis in normal pediatric subjects. Pelvic incidence, pelvic tilt, thoracic kyphosis and lumbar lordosis tend to increase during growth while sacral slope is not influenced by age. These changes may arise in order to maintain adequate sagittal balance with growth.

Discussion: Sagittal alignment of the spine and pelvis in the pediatric population are poorly defined in the literature. Pelvic morphology, as measured by the pelvic incidence angle, tends to increase during childhood and adolescence before stabilizing into adulthood, most likely to maintain adequate sagittal balance to accommodate physiological and morphological changes occurring during growth. Pelvic tilt and lumbar lordosis, two position-dependent parameters, also react by increasing with age, most likely to avoid inadequate anterior displacement of the body center of gravity. Sacral slope is achieved with the standing posture and is not further significantly influenced by age. This study establishes baseline values for these measurements in the pediatric population. These results are important for assessing the relationship between pelvic morphology and the development of various spinal disorders such as spondylolisthesis and scoliosis.

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