Dynamic lumbar intervertebral motion sharing in back pain patients and controls

Authors: Breen, A.

Start date: 28 October 2018

Introduction The mechanisms of chronic, non-specific low back pain (CNSLBP) have eluded objective assessment; however, motion sharing inequality (MSI) between vertebral segments during flexion seems to be a biomarker representing a form of movement impairment. Consistent with this, independent studies using surface markers have found regional upper lumbar motion to be greater and lower lumbar motion smaller in such patients. Purpose In order to better understand this phenomenon and its possible links to pain generation, this research aimed to investigate these interactions dynamically and at individual segmental levels.

Materials and Methods One hundred and one healthy, pain free volunteers received quantitative fluoroscopy (QF) examinations during lumbar flexion and the dynamic motion sharing of segments from L2-S1 and their MSI were calculated. Correlation coefficients were calculated between MSI and IV-RoM for each level. Finally, 10 controls were matched to 10 patients with CNSLBP for age and sex, and their MSIs and dynamic motion sharing patterns compared.

Results The first study in healthy controls (n=101) showed that the share of motion was highest at L2-3 and L3-4 and lowest at L5-S1 throughout the entire motion. This was exaggerated with higher MSIs. The second study (n=20), comparing patients and controls, found that patients had non-significantly higher MSI’s, (p=0.17) and significantly higher proportional IV-RoMs at L2-3 and L3-4 than at L5-S1 (p<0.01). Furthermore, the proportional sharing of motion was less variable throughout the sequences in patients.

Conclusions 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 appears to be more pronounced, and is also associated with less individual level variation during the motion. Whether these effects result from changes in muscular contraction or in the mechanical properties of the disc remains to be determined.

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