Relationship between the pelvic incidence and the modified Oxford Hip score: a computed tomographic analysis

There is scant data on the relationship between skeletal maturity and pelvic parameters such as the pelvic incidence (PI). The aim of this study was to report on the relationship between PI and the modified Oxford Hip Score (mOHS) as a measure of skeletal maturity. We hypothesised a significant correlation would be determined between the mOHS and PI.

CT performed for major trauma or abdominal pathology was assessed. The PI and segmental vertebral body angles, L1-L5, were obtained. The mOHS was used to assess maturity with total scores ranging from 16 to 25 (least-most mature). 193 scans were analysed. The mean age 9.7 years (range 4.0 - 15.7); 62 female (32%).

There were significant positive correlations between age and all components of the mOHS: FH (r = 0.765; p < 0.001), GT (r = 0.749; p < 0.001), LT (r = 0.704; p < 0.001), TC (r = 0.775; p < 0.001), IL (r = 0.642; p < 0.001) and mOHS (r = 0.811; p < 0.001). Mean PI for the cohort was 40.8 (s.d. 9.1; range 19.3-69.4). There were significant albeit weak correlations with FH (r = 0.213; p = 0.003), GT (r = 0.209; p = 0.004), LT (r = 0.247; p < 0.001), TC (r = 0.263; p = < 0.001), IL (r = 0.221; p = 0.002) and total mOHS (r = 0.255; p < 0.001). Multivariable linear regression indicated TC and LT the best predictors of PI. Significant correlations noted between L1 segmental lordosis and all components of the mOHS, strongest with triradiate (r=-0.406; p < 0.001).

In this CT-based study, the mOHS correlated weakly with PI and proximal vertebral body lordosis. Of the mOHS components, triradiate and lesser trochanter cartilage status appeared to be best correlated with PI and may be anatomic variables to focus on in future research.