Clinical diagnosis
Case 191
【Progress】
They were given injection of local anesthesia, xylocaine to the pain-responsible facet joint. Thereafter, they got training of athletics, releasing strain of intervertebral facet.
【Discussion】
The main role of lumbar spine is to support our weight. The lumbar disc in front and bilateral two facet (apophyseal or zygapophyseal) joints in back function together to hold a weight of human walking with two legs. Facet joint is formed at an attached site between inferior articular process and superior articular process. In general, a main interest in back pain does face towards hernia protrusion compressing neural roots or cauda equina but not toward facet joint. Recently, the new orthopedic book is published (1), saying that back pains found in community orthopedic clinic do not always relate to disk hernia and spinal canal stenosis but mostly relate to facet joints, disk itself and/or fascia system including muscle, tendon and ligament. The abnormality of these sites is susceptible to be overlooked on CT and MRI.
Facet joint owns four parts; (fibrous) cartilage, (fibro-adipose) meniscus, fat pad including vessels and articular capsule (fibrous rim). This structure is not surprising but common in various typical joints such as knee joint, jaw joint and pharyngeal joints. Meniscus in the facet joint can be called meniscoid since it consists histologically of fibro-adipose tissue rather than fibro-cartilagenous tissue in knee meniscus (1,2).
The inferior articular process of one lumbar vertebra rests into the superior process of the vertebra just below, forming the facet joint. The faces of right and left facet joints are more closer to the sagittal face in the upper lumbar vertebra than in the lower one. It indicates the lower lumbar facet joints receive more rotation stress than the upper one. Further, although the lower lumbar facet joints are not as mobile as the lower one, they do play role of load bearing and mobiles in forward and backward bending. Meniscus and fat pad are thought to be the play room to adjust for mobile stress (1, 2). In short, each time of flexion and extension of lumbar spine, facet joint receives stress and returns to normal position. Meniscus and fat pad endure the stress and help to return to normal position. When flexion, the upper pole (fat pad and meniscus) of facet joint receives stress most, while when extension, the lower pole of facet joint receives most. It is believed that sudden onset back pain is caused by entrapment of meniscus in facet joint (1-3). Excessive flexion and extension for lifting weighty load causes entrapment of meniscus inducing tensile tension of facet capsule. Entrapment of meniscus takes place in two occasions; the almost whole meniscus enters into joint space: the whole meniscus extrude outside the facet joint. In each case, facet capsule deforms with tensile stress inducing severe pain since facet capsule is innervated by nerve endings of medial branches of posterior primary rami.
Facet capsule connects to yellow ligament and plays a role of origin of multifidus muscle lumborum. The inflamed facet capsule causes thickness of yellow ligament and damage multifidus muscle. Multifidus muscle is the longest muscle from sacrum to axis. Its role is to work to stabilize the physiologic anterior curve (4, 5). Superficial lumbar multifidus muscle arises from mamillary process near superior articular process of one vertebra and spans to spinous process of three to five vertebras above the origin vertebra. Meanwhile, deep multifidus muscle arises from facet join and spans to spinous process of one vertebra above the origin vertebra. The responsible multifidus muscles to pain are ones arising from L5/S1 and L4/5 level.
Management of facet joint pain is local injection of saline or xylocaine which is called hydro-release to the painful area including facet joint, facet capsule, multifidus muscle attachment to facet capsule and yellow ligament (1, 6). Physical exercises to release multifidus muscle are also effective to abate facet joint pain (1, 6).
【Summary】
We present three cases with intervertebral facet joint injury. Lumbar MRI with fat suppression T2WI and with true SSFP shows facet joint with bright signal intensity in Case 2 and 3. It is borne in mind that facet joint composes of four parts: cartilage, meniscus, fat pad and facet capsule. Lumbar disk and bilateral facets work to support the weight for rising up in human. Facet joints at lower vertebrae of L4 and L5 work to not only support load bearing but also receive rotation stress and mobile stress of flexion and extension. Acute back pain is caused by entrapment of meniscus in facet joint. Facet capsule connects to yellow ligament and play a role of origin of deep multifidus muscle which works to stabilize physiologic anterior curve of the spine. Hydro-release to the painful area and physical exercises to release multifidus muscle are effective to abate facet joint pain.
【References】
1.Murakami E. How to manage persistent lumbago, how to identify the cause of lumbago appearing from pain of patients. (in Japanese). 2020 Nihonijisinpo, Tokyo, Japan
2.Bogduk N, et al. The menisci of the lumbar zygapophyseal joints. A review of their anatomy and clinical significance. Spine (Phila Pa 1976). 1984 Jul-Aug;9(5):454-60
3.Cohen SP, et al. Pathogenesis, diagnosis and treatment of lumbar facet joint pain. Anesthesiology. 2007;106;591-614. (Level of evidence 2C)
4.Lilius G, et al. Lumbar facet joint syndrome. A randomised clinical trial. Journal of Bone and Joint Surgery. 1989;4;681-684.
5.Freeman, et al. "The role of the lumbar multifidus in chronic low back pain: a review" (PDF). PM&R. 2010;2 : 142–6.
6.Woodham, M, et al. Long-term lumbar multifidus muscle atrophy changes documented with magnetic resonance imaging: a case series. Journal of Radiology Case Reports. 2014; 8: 27–34
2020.5.27