Age- and sex-related variations in sagittal sacropelvic morphology and balance in asymptomatic adults

Abstract

Many studies suggest the importance of the sagittal sacropelvic balance and morphology in spinal and hip disorders. This study describes the normal age- and sex-related changes in sacropelvic morphology and balance in a prospective cohort of asymptomatic adults without spinal disorder. A prospective cohort of 709 asymptomatic adults without spinal pathology was recruited. There were 354 males and 355 females aged 37.9 ± 14.7 and 35.7 ± 13.9 years, respectively. For each subjects, pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS) were measured from standing lateral radiographs. Ratios of SS to PI (SS/PI), PT to PI (PT/PI), and PT to SS (PT/SS) were also calculated. There was no significant difference in PI (pelvic incidence), SS (sacral slope), PT (pelvic tilt), PT/PI, SS/PI, or PT/SS between males and females. The mean ± 2 standard deviations (SD) range was 32°-74°, 0°-27°, and 24°-55° for PI, PT and SS, respectively. The mean ± 2 SD range was greater than 0.5 for SS/PI and less than 0.5 for PT/PI. PI was not related to age in either sex group. PT, SS, PT/PI, SS/PI, and PT/SS presented only weak correlation coefficients (r ≤ 0.21) with respect to age. The current study presents the largest cohort of asymptomatic adults in the literature dedicated to the evaluation of sagittal sacropelvic morphology and balance. The range of values corresponding to the mean ± 2 SD can provide invaluable information to clinicians about the normal range of values expected in 95% of the normal population.