Abstract
Lumbar facet arthropathy is a common cause of low back pain. The most common cause of lumbar facet arthropathy is osteoarthritis. History and physical exam are nonspecific in delineating lumbar facet arthropathy from other potential causes of low back pain. Imaging is often nonspecific as well. Initial conservative treatment for suspected lumbar facet pain includes the use of oral medication and physical therapy. In refractory cases, diagnostic medial branch blocks are used to establish the diagnosis. When medial branch blocks are positive, they are predictive of good treatment response to radiofrequency ablation of the lumbar facet joints. Both disease and treatment complications related to lumbar facet arthropathy are extremely rare.
Keywords
Low back pain, Facet Joint, Zygapophyseal Joint, Medial Branch Block, Radiofrequency Neurotomy, Radiofrequency Ablation
| Synonyms | |
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| ICD-10 Codes | |
| M47.817 | Spondylosis without myelopathy or radiculopathy, lumbosacral region |
| M47.899 | Other spondylosis, site unspecified |
| M54.5 | Low back pain |
Definition
Lumbar facet joints (zygapophyseal joints, z-joints) are formed by the articulation of the inferior and superior articular facets of adjacent vertebrae. The synovial capsule of facet joints receives nociceptive innervation via the medial branches of the dorsal rami ( Fig. 46.1 ). The point prevalence of low back pain in the United States is 8.1%, with lumbar facet pain as the cause between 10% and 40% of the time. Facet arthropathy refers to any acquired, traumatic, or degenerative process that changes the normal function or anatomy of a lumbar facet joint. The most common cause of lumbar facet arthropathy is osteoarthritis, which is most common at L4-L5 and associated with advancing age and intervertebral disc degeneration at L5. These findings are independent of race and sex. Segmental degenerative changes including facet arthropathy are very common after lumbar disc surgery. These are accompanied by facet joint pain in 8% of patients after lumbar disc surgery. Other causes of lumbar arthropathy include rheumatologic conditions such as ankylosing spondylitis and biomechanical abnormalities such as asymmetric alignment of the joints (facet tropism). In patients with low back pain, lumbar facet joints may be a primary source of pain, but may also be painful concomitantly with other lumbar spine pathology.
Symptoms
In general, facet arthropathy can result in low back pain. However, specific clinical features have not been found to reliably differentiate facet joint pain from other causes of low back pain. Patients may complain of generalized or paramidline spinal pain. Pain may be well localized; however, localization of pain to the low back, buttocks, and leg is a nonspecific finding in patients with low back pain. Surprisingly, pain referred below the knee is neither less nor more prevalent in patients with facet joint pain.
Physical Examination
A detailed examination of the lumbar spine and a lower extremity neurologic examination are considered standard procedure for any patient presenting with low back pain. The physical examination can be helpful in elevating the clinician’s level of suspicion for the diagnosis of lumbar facet pain. The examination starts with simple observation of the patient’s gait, posture, movement patterns, and range of motion. Generalized and segmental spinal palpation is followed by a detailed neurologic examination for sensation, reflexes, tone, and strength. In the absence of coexisting pathologic processes, such as lumbar radiculopathy, strength, sensation, and deep tendon reflexes should be normal.
Provocation maneuvers should also be performed. Facet pain may be reproduced with extension and rotation (facet loading maneuver). Pain with lumbar extension may also be present. Other physical exam maneuvers may be performed to assess for alternate pain generators that refer pain to the low back, for example, performing Flexion Abduction External Rotation test to evaluate for sacroiliac joint pain. Neural tension tests such as the straight leg raise can be performed to rule out superimposed lumbar radicular pain that might accompany a facet disorder. Typically, in isolated cases of lumbar facet disorders, this maneuver does not provoke radiating symptoms into the lower extremity, but may cause low back pain. That said, no single exam or combination of exam maneuvers has been shown to be a valid diagnostic tool for diagnosing lumbar facet pain.
Functional Limitations
Because of the location of lumbar facet joints in the posterior column of the spine axis, symptoms are aggravated by extension-based activities. Patients may describe this as pain worse with standing or lying prone and alleviated by sitting. Functionally, this may also be experienced as difficulties with prolonged standing or walking during work or recreation activities, twisting motions during sports, and lying in bed.
Diagnostic Studies
Abnormalities seen in the facet joints on routine imaging such as x-ray or computed tomography do not correlate with symptomatically painful joints. Limited evidence exists that abnormalities seen on single photon emission computed tomography (SPECT) may predict painful z-joints that respond to intra-articular steroid injections. More recently, abnormalities seen in lumbar facet joints on short tau inversion recovery magnetic resonance imaging (MRI) sequences and fat-saturated MRI sequences have been correlated with symptomatic facet arthropathy. Facet inflammation on MRI has also been correlated with serum inflammatory markers in patients with ankylosing spondylitis.
Recall that the lumbar facet joints are innervated by the medial branches of the dorsal rami above and below the joint space ( Fig. 46.2 ). Accurately anesthetizing these nerves via fluoroscopy has been experimentally proven to block pain arising from the facet joints. Accordingly, fluoroscopy-guided medial branch blocks (MBBs) are considered the “gold standard” for the diagnosis of a painful lumbar facet joint. A single MBB has an unacceptably high false positive rate, however, so to ensure accuracy, dual MBBs are recommended. In this paradigm, an MBB is performed twice, each time with an anesthetic of different duration of action. If a patient fails to achieve relief in either case, ideally for a time consistent with the local anesthetic used, the result of the test is considered negative. In general, the patient must be experiencing his or her typical pain prior to the procedure. Careful documentation of the patient’s pre- and post-procedure pain level is then required to determine what degree of pain relief was achieved after this injection and for how long this lasted.
Lumbar discogenic pain
Spondylolysis
Mobile spondylolisthesis
Proximal lumbar radicular pain
Sacroiliac joint dysfunction
Somatic referred hip pain
Fibromyalgia
Treatment
Initial
Initial treatment for low back pain commonly involves medication. For noninvasive treatment options, such as medication or physical therapy, most literature does not specify between specific causes of low back pain and only evaluates these treatment options as they pertain to “nonspecific low back pain.” Such studies must also be considered within the context of an already favorable natural history of most cases of low back pain. Given these limitations, it is often difficult to properly interpret the outcomes of these studies.
Medication choices include acetaminophen, muscle relaxants, nonsteroidal anti-inflammatory drugs (NSAIDs), and opioids. Oral acetaminophen has been shown to have no effect on recovery time from an acute episode of low back pain compared to placebo. Evidence in support of topical NSAIDs is also limited. Oral NSAIDs have been found to be both superior to placebo, but equal to acetaminophen in treating low back pain. In the acute setting, the addition of cyclobenzaprine or oxycodone with acetaminophen to prescribing naproxen (an NSAID) did not result in differences in pain or function at 1 week. The heterogeneity in outcomes seen in these studies is likely at least in part due to the nonspecific design of studies that includes many heterogeneous etiologies of low back pain. Accordingly, often medications with more favorable side-effect profiles are preferentially used. Opioids should be used with great caution due to the high risk of addiction and overdose. Recent Centers for Disease Control and Prevention (CDC) guidelines state that, in cases of non-cancer or non-palliative care such as low back pain, non-opioid pharmacologic therapy is preferred. Moreover, if opioids are to be used, three days or less is often sufficient, with use beyond seven days rarely indicated.
Rehabilitation
In addition to oral medication, initial treatment for low back pain also frequently incorporates physical therapy. Physical therapy entails a variety of modalities including pain control (e.g., ice, heat), traction, instruction in body mechanics, flexibility training (including hamstring stretching), articular mobilization techniques, core strengthening, generalized conditioning, and restoration of normal movement patterns. It may be helpful to assess the biomechanics of specific activities (e.g., sitting at a desk, carpentry work, driving, running, cycling). In theory, this may result in decreased severity or frequency of recurrent episodes of pain by optimizing the underlying forces at the affected joint. Outcome literature on physical therapy for the treatment of low back pain is variable. This again is likely due to heterogeneous patient groups being included in nonspecific studies. That said, some of the best supporting evidence is for early outpatient physical therapy for the treatment of acute low back pain. There is no evidence suggesting benefit for inpatient rehabilitation in the treatment of isolated facet joint-mediated low back pain.
Procedures
Fluoroscopic-guided facet targeted injections are a potential treatment option for lumbar facet pain, usually after oral medications and therapy have been attempted and failed to provide adequate relief. The evidence in support of intra-articular lumbar facet steroid injections is very limited. The best evidence that exists in support of intra-articular lumbar facet steroid injections utilizes SPECT imaging to identify patients with lumbar facet pain. One comparative study also suggests that intra-articular steroid injections may be as effective as radiofrequency neurotomy (RFN) targeting the lumbar facet joints. Ultrasound guidance for intra-articular facet injections is also an emerging option, though additional evidence is still needed.
The best available evidence on the treatment of lumbar facet pain supports the use of RFN. RFN uses radiofrequency to transmit heat energy at the tip of an electrode. When applied to a nerve, this results in neurolysis via protein denaturing and cellular membrane disruption. RFN requires technical precision in order to generate lesions that capture the target nerve. For example, electrodes must be placed parallelly to the target as opposed to perpendicularly ( Fig. 46.3 ); procedure details are published elsewhere. RFN is not necessarily curative, as intact cell bodies remain capable of axonal regeneration. However, average relief is greater than 1 year. If symptoms return, repeat RFN will often re-institute relief obtained from the initial treatment.
