Sagittal spinopelvic parameters in children with achondroplasia: identification of 2 distinct groups

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Spinopelvic parameters in children with achondroplasia have not been described. Because they observed a unique sagittal spinopelvic phenotype in some achondroplastic children with very horizontal sacrums, the authors sought to quantify the spinopelvic parameters in a pediatric patient population.


A retrospective review was performed to identify all children (age range 1 month–10 years) with a diagnosis of achondroplasia between 2004 and 2009. Clinical and radiographic data were analyzed for age, sex, lumbar lordosis (LL), thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), sacral slope (SS), pelvic tilt (PT), and pelvic incidence (PI). Differences among these variables were analyzed using a 2-tailed, unpaired Student t-test.


Forty children, 23 males and 17 females, with achondroplasia were identified during the study period. The mean age was 2.6 years. Two groups of patients were identified based on PT (that is, negative or positive tilt and horizontal or not horizontal sacrum). A negative PT was identified in all children with an extremely horizontal sacrum. Seventeen children had a negative PT (mean −16.6°), and the mean parameters in this group were 65.4° for LL, 31.7° for TLK, 18.5° for TK, 43.3° for SS, and 26.4° for PI. Twenty-three children had a positive PT (mean 17.9°), and the mean parameters in this group were 53.4° for LL, 41.5° for TLK, 9.6° for TK, 30.8° for SS, and 43.8° for PI. A statistically significant difference was observed for LL (p = 0.01), TLK (p = 0.05), SS (p = 0.006), PT (p = 0.006), and PI (0.0002).


Spinopelvic parameters in achondroplasia are potentially dichotomous. The future implications of this observation are not known and will need to be explored in future long-term studies that follow pediatric patients with achondroplasia through adulthood.

Abbreviations used in this paper:LL = lumbar lordosis; PI = pelvic incidence; PT = pelvic tilt; SS = sacral slope; TK = thoracic kyphosis; TLK = thoracolumbar kyphosis.

Article Information

Address correspondence to: Oren N. Gottfried, M.D., Division of Neurosurgery, Duke University Medical Center, Box 3807, Durham, North Carolina 27710. email:

Please include this information when citing this paper: published online April 27, 2012; DOI: 10.3171/2012.3.SPINE11735.

© AANS, except where prohibited by US copyright law.



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    Left: Standing lateral radiograph obtained in a representative patient, showing a negative PT and corresponding spinopelvic parameters: SS = 45.89°, PT = 15.19°, and PI = 29.89°. Right: Standing lateral radiograph obtained in a representative patient, showing a positive PT and corresponding spinopelvic parameters: SS = 33.6°, PT = 14.9°, and PI = 49.1°.



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