Background: Spinopelvic characteristics influence the hip's biomechanical behavior. However, there is currently little knowledge regarding what "normal" characteristics are. This study aimed to determine how static and dynamic spinopelvic characteristics change with age, sex, and body mass index (BMI) among well-functioning volunteers.Methods: This was a cross-sectional cohort study of 112 asymptomatic volunteers (age, 47.4 ± 17.7 years; 50.0% female; BMI, 27.3 ± 4.9 kg/m 2 ). All participants underwent lateral spinopelvic radiography in the standing and deepseated positions to determine maximum hip and lumbar flexion. Lumbar flexion (change in lumbar lordosis, ΔLL), hip flexion (change in pelvic-femoral angle, ΔPFA), and pelvic movement (change in pelvic tilt, DPT) were determined. The hip user index, which quantifies the relative contribution of the hip to overall sagittal movement, was calculated asResults: There were decreases of 4.5°(9%) per decade of age in lumbar flexion (rho, 20.576; p < 0.001) and 3.6°(4%) per decade in hip flexion (rho, 20.365; p < 0.001). ΔLL could be predicted by younger age, low standing PFA, and high standing LL. Standing spinopelvic characteristics were similar between sexes. There was a trend toward men having less hip flexion (90.3°± 16.4°versus 96.4°± 18.1°; p = 0.065) and a lower hip user index (62.9% ± 8.2% versus 66.7% ± 8.3%; p = 0.015). BMI weakly correlated with ΔLL (rho, 20.307; p = 0.011) and ΔPFA (rho, 20.253; p = 0.039).Conclusions: Spinopelvic characteristics were found to be age, sex, and BMI-dependent. The changes in the lumbar spine during aging (loss of lumbar lordosis and flexion) were greater than the changes in the hip, and as a result, the hip's relative contribution to overall sagittal movement increased. Men had a greater change in posterior pelvic tilt when moving from a standing to a deep-seated position in comparison with women, secondary to less hip flexion. The influence of BMI on spinopelvic parameters was low.T he relationship among the hip, pelvis, and spine has recently received great interest, as patients with spinopelvic pathology have been shown to have higher rates of complications, including dislocation, following total hip arthroplasty (THA) [1][2][3][4] . The position of the lumbar spine affects the pelvic position, which in turn influences acetabular orientation 5,6 , an important determinant of hip biomechanics in native 4,7,8 and replaced hips 9,10 . In patients with hip osteoarthritis, femoroacetabular flexion is reduced, which is associated with an increased posterior pelvic tilt (PT) in the seated position and corresponding compensation in the lumbar spine (reduction in lordosis angle) 11 . This compensatory mechanism is reversed after THA in individuals without a history of spinal fusion 12 .Changes in spinopelvic parameters during aging might be different between asymptomatic and symptomatic individuals, because the latter may have developed altered motion due to the underlying pathology 13 . In order to better understand the role of ...

Background: A lumbosacral transitional vertebra (LSTV) has been reported to be prevalent among patients with hip dysplasia. The aims of this study were to determine the (1) prevalence of an LSTV in young patients presenting with hip pain and a group of asymptomatic volunteers, (2) effect of an LSTV on spinopelvic characteristics, and (3) presence of low back pain among patients with an LSTV.Methods: This cross-sectional study included 102 patients with hip pathology and 51 asymptomatic volunteers (mean age, 33.9 ± 7.3 years; mean body mass index, 26.0 ± 5.0 kg/m 2 ; 57.5% female). Participants underwent radiographic assessment of the lumbar spine and pelvis in standing and deep-seated positions. LSTV occurrence was classified according to the Castellvi system. Spinopelvic characteristics included lumbar lordosis (including segmental lumbar angles), pelvic tilt, and hip flexion (pelvic-femoral angle). Differences between standing and deep-seated values were calculated. Low back pain was assessed using the Oswestry Disability Index. Results:The prevalence of LSTV type ‡II was 8.5%, with no difference between patients and volunteers (p = 0.386).Individuals with an LSTV had a greater standing L1-L5 angle (mean, 51.6°± 11.7°versus 38.9°± 9.3°; p < 0.001). The overall spinal flexion (change in L1-S1 angle between the standing and deep-seated positions) in individuals with an LSTV was similar to that in individuals without an LSTV; restricted L5-S1 mobility was compensated for at L1-L2 (10.2°± 5.8°in those with versus 8.4°± 4.1°in those without an LSTV; p = 0.070). No significant difference in the presence of low back pain was found (p = 0.250).Conclusions: An LSTV was found in 8.5% of young adults, with no difference between patients with hip pathology and controls. Individuals with an LSTV have greater standing lumbar lordosis, with altered mechanics at the cephalad adjacent level, which may predispose these individuals to degenerative changes at this level.