Orientation and Osteoarthritis of Lumbar Facet Joints: Association with Degenerative Disk Disease

Abstract

Introduction

Several studies have shown relationship between sagittal orientation of lumbar facet joint and degenerative spondylolisthesis^1,2,3; however, there is no current information on how much the facet orientation and osteoarthritis associate with different grades and morphologies of lumbar disk degeneration on MRI. We hypothesize that sagittally oriented facet joints promote a degenerated intervertebral disk (IVD) to develop spondylolisthesis rather than a collapsed disk. Aim of this study is to evaluate the association between lumbar facet joint orientation, facet osteoarthritis, IVD herniation, and different grades of disk degeneration.

Materials and Methods

A total of 550 patients who underwent lumbar spine MRI for low back pain or radicular leg pain were reviewed. Patients with previous back surgery, congenital anomalies, spondylolysis, infection, tumor, or fracture were excluded. Total 153 patients were included and assessed for IVD degeneration according to Modified Pfirrmann (MP) grading⁴ at L3-S1 lumbar segments. Facet joint angles on axial scan and Fujiwara osteoarthritic grading⁵ were assessed at spinal segments of the following six groups: “Bright disk” (MP grade 1 or 2), “Black disk” (MP grade 4 or 5), “Collapse disk” (MP grade 6 to 8), “Herniated disk” (bulging or prolpase), spondylolisthesis and “nonslip level” of spondylolisthesis. The mean facet angles and the percentages of the mild (Fujiwara grade 1 or 2) and advanced (Fujiwara grade 3 or 4) facet osteoarthritis were compared between six groups using independent sample t test and Pearson Chi Square test, respectively. The association of facet joint orientation and osteoarthritis was also examined by linear regression analysis.

Results

The mean facet angles relative to the coronal plane in patients who had “Black disk” (right L3/4: 55.7⁰, L4/5: 47.5⁰, L5/S1: 39.7⁰), “Collapse disk” (right L3/4: 54.1⁰, L4/5: 47⁰, L5/S1: 38⁰) and “Herniated disk” (right L3/4: 56⁰, L4/5: 46.1⁰, L5/S1: 38.1⁰) were significantly more sagittal at all levels (p0, L4/5: 41.1⁰, L5/S1: 35.8⁰). There was no statistical difference of mean facet angles at all levels between “Black disk”, “Collapse disk,” and “Herniated disk” (Table 1). Facet joint osteoarthritis were more advanced in “Black disk”, “Collapse disk”, “Herniated disk” than “Bright disk”, but there was no difference in percentage of mild and advanced facet osteoarthritis among three groups. Degenerative spondylolisthesis segments demonstrated significantly more sagittal mean facet angle (right L3/4: 72.6⁰, L4/5: 67.2⁰, L5/S1: 49⁰, p0, L4/5: 54⁰, L5/S1: 42⁰, p0, which is the mean facet angle of patient without spondylolisthesis + SD, was 25 times more likely to have degenerative spondylolisthesis. Advanced degenerative “Collapse disk” had no significant difference in mean facet angle from that of early degenerative “Black disk.” A positive association between sagittal orientation and osteoarthritis of facet joints was demonstrated. Only degenerative spondylolisthesis demonstrated the significant correlation between facet joint osteoarthritis and disk degeneration (Fig. 1).

Conclusion

Sagittal facet orientation relates to facet joint osteoarthritis and IVD degeneration. Degenerative spondylolisthesis had more advanced facet osteoarthrosis and disk degeneration. The increase in facet angles at “nonslip” levels other than that of the spondylolisthesis suggests that increased facet angles represent variations in developmental anatomy and contribute to instability of a functional spine unit when degenerative disk loses its anterior vertebral column support.

I confirm having declared any potential conflict of interest for all authors listed on this abstract

No

Disclosure of Interest

None declared

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