The Influence of Seated Weight-Bearing on Rotational Positional Alterations of Lumbar Facet Joints.

Abstract

This study aimed to quantify the effect of seated weight-bearing on the rotational motion characteristics of lumbar facet joints (LFJs) using the dual fluoroscopic image system (DFIS), providing kinematic evidence for the prevention and clinical management of lumbar degenerative disorders. Sixteen healthy volunteers (8 males, 8 females; age: 25-39 years, mean: 32 ± 4.29 years) were enrolled. Thin-layer computed tomography (CT) scans of the L3-S1 segment (64 vertebrae total) were acquired to reconstruct 3D lumbar spine models via Mimics 21.0. DFIS was used to simulate seated rotational motion (left rotation, neutral position, right rotation) under 0 kg (non-weight-bearing, NWB) and 10 kg weight-bearing (WB) conditions. Translational displacements (X: coronal axis, Y: sagittal axis, Z: vertical axis) of L3/4, L4/5, and L5/S1 LFJs were measured and compared using Rhinoceros 5.0. Statistical analysis was performed via SPSS 26.0 with paired t-tests; P < 0.05 was considered statistically significant. At L4/5, WB significantly reduced translational displacements: left side (X-axis:0.01 ± 0.80 mm [NWB] vs1.00 ± 1.01 mm [WB], P = 0.014; Y-axis: 0.90 ± 1.76 vs 0.55 ± 0.55 mm, P = 0.014) and right side (X-axis: 0.04 ± 0.79 vs 1.05 ± 0.94 mm, P = 0.023; Z-axis: 1.25 ± 0.98 vs 0.92 ± 1.22 mm, P = 0.001). At L5/S1, WB induced significant displacement reductions: left side (Y-axis: 2.42 ± 1.16 vs 0.15 ± 1.82 mm, P < 0.001; Z-axis: 3.43 ± 3.30 vs 3.03 ± 0.76 mm, P = 0.002) and right side (Z-axis: 1.57 ± 2.01 vs 0.64 ± 1.53 mm, P = 0.002). Seated weight-bearing alters the rotational kinematics of LFJs, particularly at L5/S1, with significant reductions in translational displacements. This finding provides a biomechanical basis that may inform our understanding of load-related adaptations in the lumbar spine.