Biokinetic insights into the hip-spine relationship: no correlation between hip strength or flexibility and altered pelvic motion in patients with low back pain.

purposeThe spine and hips are biomechanically interconnected, and disorders affecting both are often categorized under hip-spine syndrome. This study explores the link between pelvic motion impairments and hip functional characteristics, specifically hip strength and flexibility, in low back pain patients with increased contralateral pelvic drop and anterior tilt during gait. The hypothesis was that hip strength and flexibility would correlate with pelvic gait kinematics.

methodsThis cross-sectional retrospective study analyzed previously collected data from a clinical motion analysis laboratory biomechanical database. Participants aged 18-65 years with acute or chronic low back pain and the ability to ambulate independently were included. Participants had been previously categorized into distinct gait profiles (P1: Flexed trunk; P2: Lumbar rectification; P3: Pelvic impairment; P4: Trunk extension and rotation; P5: Tight axial control) based on three-dimensional gait kinematics using machine learning algorithms. The current analysis examined intra-profile correlations between pelvic motion during gait (pelvic drop and anteversion) and clinical measures of hip function (hip abductor strength and hip flexor/extensor flexibility). Spearman's rho was used to assess linear correlations and normalized mutual information was computed to explore non-linear associations. Statistical significance was set at p < 0.05.

resultsNo statistically significant correlations were found for profiles 3, 4, and 5 (p > 0.05). Although significant correlations emerged within profiles 1 and 2, as well as when considering profiles 1-5 as a single group (p < 0.05), these lacked clinical relevance due to low biomechanical plausibility.

conclusionThis study builds on previous literature on biokinetic profiles in low back pain and provides new insights into the associations related to hip-spine kinematics. There was no association between hip strength or flexibility and altered pelvic kinematics during gait in the Pelvic Impairment profile. These findings raise the possibility that the observed pelvic motion impairments may reflect associations other than primary deficits in the hip musculature, such as compensatory or neuromotor strategies, which warrant investigation in longitudinal studies.