The Ratio of Lumbar to Hip Motion during the Trunk Flexion in Patients with Mechanical Chronic Low Back Pain According to O’Sullivan Classification System: A Cross-sectional Study

Background: Static and dynamic postures of lumbopelvic in low back pain (LBP) are considered as two importantaspects of clinical assessment and management of LBP. Thus, the focus of the current study was to compare theposture and compensatory strategy of hip and lumbar region during trunk flexion between LBP subgroupsand healthsubjects. LBP cases are subdivided into active extension pattern (AEP) and flexion pattern (FP) based on O’Sullivan’sclassification system (OCS).Methods: This work was a cross-sectional study involving 72 men, 21 low back pain patients with FP and 31 low backpain patients with AEP and 20 healthy groups. Lumbar and hip angles during trunk flexion were measured by a 3Dmotion analysis system in neutral standing posture and end-range of trunk flexion. The participants were asked to fullbend without any flexion of the knees. The bending speed was preferential. Hip and lumbar ranges of motion weredivided into four quartiles (Q). The quartiles were compared between groups. Data analysis was performed using onewayanalysis of variance (ANOVA) and independent t-test.Results: There was no statistically significant difference in lumbar lordosis in standing and full trunk flexion positionsbetween the healthy groups and heterogeneous LBP groups. In addition, there was not any statistically significantdifference between the healthy group and the homogenous LBP group (FP and AEP). Moreover, no statistically significantdifference was observed in hip angles during standing between the healthy group and the heterogeneous LBP group,and between the healthy group and the homogenous LBP group (FP and AEP). In full trunk flexion position, there wasstatistically significant difference in hip angles between the healthy group and the heterogeneous LBP group (P=0.026).In this position, the difference in hip angles between the healthy group and FP group was statistically significant(P<0.05). In the second Q, there was no significant difference between the healthy group and the heterogeneous LBPgroup (P=0.062), however, there was a significant difference between FP group and the healthy group in the fourthQ of the total hip range of motion. There was no statistically significant difference between the healthy group and theheterogeneous LBP group (P=0.054) but there was a difference between FP group and the healthy group. Lumbar/hipmotion ratio (L/H ratio) was different between and within the subgroups in the second Q.Conclusion: This study supported the subgrouping of LBP and showed that the difference between subgroups couldbe determined effectively through subdividing the total range of lumbar and hip motions into smaller portions. It ispossible that the neuromuscular system selects different strategies to compensate and prevent further injury of thechain components (muscle, joint, nerve and etc.).Level of evidence: IV

Keywords:

classification , Forward flexion , Kinematics , Low back pain , lumbar spine , Posture