Goal of the Study?
In this primary research article1, the authors had two goals: (a) Determine and quantify the relationship between biomechanical and neurophysiology measurements in lower back pain patients and (b) examine if the correlations differ when considered regionally (lumbar back) or segmentally.
Why are they doing this study?
To improve our understanding of Lower Back Pain etiology, better non-invasive measurement tools and techniques must be established and quantified.
What was done?
A sample of 132 patients of the Spine Centre of Southern Denmark who had persistent non-specific Lower Back Pain was measured for three different sensitivities: (a) global spinal stiffness (GS) using a VerteTrack Device which applied a rolling weight across the S1 and T12 spine; (b) deep mechanical pressure pain sensitivity threshold (PPT) using pressure algometer which applied bilateral pressure at each lumbar segment and (c) superficial heat pain sensitivity threshold (HPT) using a handheld thermode at the midline of each lumbar segment.
A series of statistical tests were performed to determine if there were any correlations between these three quantitative sensory metrics: Global Stiffness (GS), Pressure Pain Threshold (PPT) and Heat Pain Threshold (HPT).
What did they find?
The correlation coefficients (R) for each pair of these three quantitative sensory metrics; GS, PPT and HPT were calculated and tested for statistical significance.
- Correlation between GS and HPT were found to be poor and statistically insignificant (R = 0.23)
- Correlation between GS and PPT were moderate (R = 0.38) and statistically significant
- Correlation between HPT and PPT were good (R= 0.53) and statistically significant
Unexpectedly, the correlation between GS and PPT was positive, meaning participants with higher global stiffness had a higher pressure pain threshold. The authors expected the reverse. They based their explanation of this unexpected relationship on the body’s adaptive mechanical protection system. Pain is considered a protective response and a stiffer spine is more resilient to applied forces and therefore can tolerate a higher pain threshold.
The other’s unexpected anomaly was that for the three QST’s measured, no differences were found between the individual lumbar segments. This indicates that patients with persistent LBP are probably less able to perceive lumbar stiffness reliably, perhaps due to “Cortical Smudging”, an overlapping of the cortical homunculus.
Why do these findings matter?
Around four out of five people have lower back pain at some point in their lives. It’s one of the most common reasons people visit healthcare providers. To successfully evaluate both the extent of LBP and the effectiveness of any treatment plan, a reliable metric must first be established. This study is an attempt to use stiffness (GS), heat (HPT) and pressure (PPT) as this critical metric.
At Dynamic Disc Designs, we have developed models with varying lumbar stiffness to help in the education of the possible sources of back pain. This new research is important in establishing greater understanding of the causes and solutions of low back pain.