Lumbar Facet Arthropathy

Excerpt

The lumbar zygapophysial joint, otherwise known as facet joint, is a common generator of lower back pain. The facet joint is formed via the posterolateral articulation connecting the inferior articular process of a given vertebra with the superior articular process of the below adjacent vertebra. The facet joint is a true synovial joint, containing a synovial membrane, hyaline cartilage surfaces, and surrounded by a fibrous joint capsule. There is a meniscoid structure formed within the intra-articular folds. The facet joint is dually innervated by the medial branches arising from the posterior ramus at the same level and one level above the joint.

The facet joints play an important role in load transmission, assisting in posterior load-bearing, stabilizing the spine in flexion and extension, and restricting excessive axial rotation. Studies before and after facetectomy have shown that the facet joint may support up to 25% of axial compressive forces and 40% to 65% of rotational and shear forces on the lumbar spine.

Facet joint arthrosis is a pathological process involving the failure of the synovial facet joints. Degenerative changes begin with cartilage degradation, leading to the formation of erosions and joint space narrowing, and eventually sclerosis of subchondral bone. Risk factors include advanced age, a sagittal orientation of the facet joint, and concomitant intervertebral disk degeneration.