Dynamic interactions between lumbar intervertebral motion segments during forward bending

Authors: Breen, A.

Start date: 4 July 2019

Introduction: Surface marker studies have found greater flexion ranges in the upper than lower lumbar spine in patients with nonspecific low back pain (NSLBP) than controls, however, these do not describe the dynamic interactions between motion segments . Subsequent studies using quantitative fluoroscopy (QF) have found that intersegmental motion is more unequally shared in NSLBP than controls but did not attribute this to individual segments . The purpose of the present research was to describe motion sharing inequality (MSI) in terms of restraint and variability at individual segments (L2-S1) throughout bending in patients and controls to inform multi-segmental dynamic loading models in back pain. Methods: One hundred and one pain free volunteers received QF during controlled lumbar flexion . Dynamic motion sharing of segments from L2-S1 and their MSI were calculated along with correlation coefficients between MSI and IV-RoM for each level. Ten controls were then matched to 10 patients with NSLBP for age and sex, and their MSIs and dynamic motion sharing patterns compared.

Results: The study of controls (n=101) found the share of motion was highest at L2-3 and L3-4 and lowest at L5-S1 throughout the motion . This was exaggerated with higher MSIs. The second study (n=20), found that patients had non-significantly higher MSI’s than controls, (p=0.17) and significantly higher proportional IV-RoMs at L2-3 and L3-4 than at L5-S1 (p<0.01). The proportional sharing of motion was also less variable throughout the sequences at L2-3 and L4-5 in patients (see Fig ). Discussion : Intervertebral motion sharing inequality is a normal feature during lumbar flexion and is characterised by increased motion at L2-3 and L3-4 and decreased motion at L5-S1. However, in patients with CNSLBP, this is more pronounced, and associated with less variation at some levels. These effects may result from changes in muscular contraction or in the mechanical properties of the disc .

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