Impact of posture and axial loading on lumbar intervertebral disc dimensions investigated by transabdominal ultrasound

PURPOSE To use transabdominal ultrasound (US) to investigate the impact of posture and axial loading on the lumbar intervertebral disc (IVD) dimensions in healthy adults. METHOD For this single-center, prospective cross-sectional study 54 healthy volunteers (mean age 23.76 ± 3, 26 men) underwent transabdominal US. Lumbar IVD dimensions (height, length, width) at the levels L3/4 and L4/5 were assessed in three test conditions: supine, standing, and standing position with additional axial load of 50 % body weight (standing+50%). Success rates for the longitudinal and transverse US acquisitions and IVD dimension measurements were determined. IVD dimensions were compared across test conditions using two-way repeated measures analysis of variance and post-hoc pairwise t-tests with Bonferroni correction. RESULTS The success rate for longitudinal and transverse US acquisition was 100 %. The overall success rate for IVD dimension measurement was 96.4 %, it was highest for IVD height (99.2 %) and lowest for IVD length (93.3 %). IVD height at L4/5 decreased significantly from the supine to standing position (p < 0.05) and from the supine to standing+50% position (p < 0.01). IVD width at L3/4 increased significantly from the supine to standing+50% position (p < 0.05). No significant differences were found for IVD length. CONCLUSIONS Transabdominal US is a feasible tool to investigate IVD dimensions at L3/4 and L4/5 in different postures and with axial loading. Posture and axial loading significantly influence IVD height and width, but not length.