Facet joint tropism
Low back pain.
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Abnormal orientation of L5-S1 right facet joint with the joint has a more sagittal orientation (almost parallel) if compared to the left one. Right facet joint grade II facet arthropathy is also noted.
Annotated image with the reference plane at the posterior edge of the vertebral body. The sagittal plane along the spinous process, right angle to the reference plane. Right facet orientation is defined by the brown line and left facet joint orientation is defined by the pink line.
Facet orientation is the angle that lies between both transverse and sagittal planes. Facet joint tropism may easily predispose to facet joint arthropathy.
Grading of facet joint arthropathy:
- grade I (normal): normal joint space
- grade II (mild): narrowed joint space 1–2 mm, small osteophytes, no sclerosis, subchondral erosions or subchondral cysts, no air within the joint space
- grade III (moderate): narrow joint space (≤1 mm), moderate osteophytes, mild subchondral erosion with subchondral cystic changes, moderate air within the joint space
- grade IV (severe): joint space is no longer seen, marked osteophytes with severe subchondral erosions and cystic changes