Why is Subchondral Bone Density Higher in People with Low Back Pain

A very recent study from September 2019, 1 published in the journal Skeletal Radiology, brought forward an interesting conclusion related to Low Back Pain or LBP. The results showed that the subchondral bone density was higher in people with LBP.

What was the Context?

According to years of data, LBP happens to be the second most common adult-disability around the world, with the lifetime prevalence being 54-80%. It leads to sociological, economic, and psychological stress. The causes behind LBP include facet joint osteoarthritis (OA), disc degeneration, soft tissue sprain, nerve impingement, instability, infection, and neoplasm. Being more specific, OA of the facet joints (the load-bearing joints of the posterior spine), is considered as the reason of LBP in 15–45% of patients.

Take note; long-term changes in the bone’s mechanical loading alters its microstructure. An increase in the mineral density of the subchondral bone has been observed due to loading on the joint’s subchondral surface. Such a change has been seen in joints of the upper and lower extremities as well as in the joints of the spine.

What Did the Current Study Do?

Apparently, not a lot of research has been conducted for analyzing such changes with a focus on the loading patterns of facet joint and its relation to LBP as well as how the subchondral bone is involved.

The current study had two objectives. It aimed to test the hypothesis that LBP is associated with the density of the lumbar facet subchondral bone. Other than that, it was to use computed tomography osteo absorptiometry to analyze the distribution of the subchondral bone density in the facet joint. The study wanted to better understand the loading pattern of the lumbar spine’s facet joints.

facet joint

The Design

The current research involved 89 volunteers. From them, a total of 33 were recruited as subjects that also had LBP, and a total of 56 were subjects with no LBP. The males were 47, with the females being 42. The mean age came in at 36.5 years.

All of the subjects went through lumber computed tomography (CT) scans. 3D joint surface models were created of each facet joint as well as the subchondral bone density underneath every facet joint surface.

This study used linear interpolation of the HU (Hounsfield units) at four adjacent pixels in each of the CT slice. Furthermore, ANOVA with post hoc Fisher pairwise comparisons was used for testing the association of subchondral bone density with lumbar levels, facet zones, subject gender, and patient age.

What Did the Results Show?

The results presented that subchondral bone density was observed to be the greatest in subjects with LBP as well as female and younger subjects. It was also highest in the superior facets, the center zone of the facets as well as the upper lumbar levels.

Also, it was lowest in subjects that didn’t have LBP, the male subjects, and older subjects. It was also lowest in the caudal zone of the facets, the lower lumbar levels, and the inferior facets.

What Was Concluded?

According to the present study, the data showed the differences present in the subchondral bone density when analyzing subjects with or without LBP. Furthermore, one can see how a higher density in subjects with LBP might be related to an increase in load-bearing because of the degeneration of the lumbar discs or perhaps due to the load’s abnormal distribution in the joint because of the joint’s articular cartilage being degenerated.

The current data hopes it can help others better understand the loading patterns of joints and the associated biomechanical properties.

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