Epidemiology, Patient History, and Physical Examination

Chronic neck pain and low back pain are highly prevalent medical conditions that cause considerable pain, disability, and economic burden [Reference Cohen1, Reference Ferguson, Merryweather and Thiese2]. Cervicalgia has an annual prevalence exceeding 30%, with an estimated half of these individuals experiencing some degree of chronicity, making it the fourth leading cause of disability in the United States [Reference Cohen1]. The lifetime prevalence of low back pain is estimated at 60–70%, affecting people of all ages, but the highest likelihood is in the fifth or sixth decade of life. This contributes to the highest number of disability-adjusted life years in the United States in 2010 [Reference Ferguson, Merryweather and Thiese2–Reference Shmagel, Foley and Ibrahim4]. Furthermore, low back pain is the leading cause of disability worldwide, according to a 2010 study of Global Burden of Disease [Reference Hoy, March and Brooks5].

The causes of low back pain can be due to muscular strain, cartilaginous deterioration, spinal cord nerve compression, intervertebral disc herniation, traumatic injury, or many other pathologic conditions. A 2018 meta-analysis demonstrated with level 1 data that obesity is a major risk factor for developing low back pain in men and women [Reference Zhang, Liu, Liu, Zhao, Liu and Tian6]. Other risk factors include age, fitness level, job-related factors, and psychological components [7]. There is loss of bone strength, intervertebral disc volume, and muscle elasticity with age [7, Reference Last and Hulbert8]. A weak back and weak core muscles do not properly support the spine. Jobs requiring heavy lifting can lead to injury; however, desk work can also contribute to pain from poor posture over prolonged periods [Reference Shmagel, Foley and Ibrahim4, 7]. Anxiety and depression can influence one’s perception of pain, whereas chronic pain can also perpetuate negative mood and depression [7].

A thorough pain history is essential in order to generate an accurate diagnosis and treatment plan for each specific patient. Characterization and location of the pain in quality and distribution can differentiate somatic versus neurogenic origin. Somatic pain will be described typically as having a dull, aching quality from nociceptors in tendons, ligaments, and bones. Radicular pain is often described as burning and shooting, with potential paresthesias, and will often radiate along dermatomal distributions. This is caused by irritation of a nerve root by compression or surrounding inflammation. Concerning symptoms, such as weakness, gait or grip disturbances, and bladder or bowel incontinence, are crucial to identify for early surgical decompression. A complete review of systems for back pain can identify referred pain from more malignant retroperitoneal sources such as aortic aneurysms, pelvic organs, gastrointestinal etiology, neoplasms, or infections [7, Reference Last and Hulbert8]. Understanding inciting events and psychosocial factors about the pain is important and can be predictive of chronicity and disability.

Coupling a patient’s history of present illness with a skilled physical examination can help delineate contributing sources, identify “red flags” signifying serious pathology, and direct a cost-effective management plan [Reference Cohen1]. Examining the patient is useful to identify obvious structural abnormalities or asymmetry, as well as attention to gait and possible use of assistive devices. Assessing the range of motion is important. One should also assess palpable focal tenderness, strength of isolated muscle groups, dermatomal sensation, deep tendon reflexes, and signs of upper motor neuron injury [Reference Last and Hulbert8, Reference Teichtahl and McColl9]. Specific diagnostic maneuvers, such as straight leg raise, facet loading, and FABER testing, can provide increased specificity to help the clinician narrow down their differential diagnosis [Reference Last and Hulbert8].

Laboratory Testing, Imaging, and Diagnoses

Further investigation of chronic back pain, whether cervical or lumbar, is often necessary to identify or rule out certain pathologies. Blood tests are not routinely necessary but could be ordered to identify signs of inflammation or arthritis, such as erythrocyte sedimentation rate or C-reactive protein levels. Blood tests can also show signs of infection, such as leukocytosis, or markers of cancer such as smear testing under microscopy. Additionally, metabolic panels are ordered to assess kidney and liver function when prescribing medications for relief of both somatic pain and neuropathic pain. Calcium and alkaline phosphatase levels can be used if suspecting conditions that affect bone metabolism, such as in osteoporosis or Paget’s disease.

Physicians should order imaging for patients with chronic persistent pain or new weakness in order to better assess pathology. Initially, imaging has limited utility in chronic low back pain because most patients harbor nonspecific findings [Reference Don and Carragee11]. There is lack of evidence supporting improvement from early imaging in patients with nonspecific pain without “red flags,” so imaging should be delayed at least 1–2 months while implementing conservative treatment modalities [Reference Last and Hulbert8]. These “red flags” are patients who are older than 50 years with new symptoms, constitutional symptoms, or a history of malignancy, infectious concerns, or new neurologic findings on examination [Reference Teichtahl and McColl9]. Initial conservative modalities consist of either physical therapy, massage therapy, acupuncture, or chiropractic maneuvers, or over-the-counter analgesics, such as acetaminophen and ibuprofen. Imaging should begin with plain radiographs; however, these lack specificity without correlating exam findings because degenerative changes in cervical and lumbar spine are common in people over 30 years old [Reference Teichtahl and McColl9]. CT or MRI are indicated where there are concerns of malignancy, infection, cord compression, or disc herniations. CT better identifies bony pathology; MRI is superior at evaluating soft tissues. After chronic pain patients have failed conservative therapy, physicians normally order an MRI scan without contrast, as it can provide additional information and images of the intervertebral discs and spinal canal that plain X-rays and CT cannot. An MRI scan with contrast is generally ordered for patients with a history of neurosurgery with hardware in their spine or for patients with infection or malignancy high on their differential.

A skilled interventional pain physician needs to synthesize the information provided by these various imaging modalities with the patient’s history, as well as with a thorough physical examination, in order to properly diagnose the root cause of the patient’s chronic pain. The most common pain diagnoses include degenerative disc disease, intervertebral disc herniation, spinal stenosis, facet joint arthropathy, and sacroiliac (SI) joint arthropathy.

The vertebral bodies are interconnected by intervertebral discs and supported by longitudinal ligaments anteriorly and posteriorly. Intervertebral discs comprise a central gelatinous nucleus pulposus, ringed by a fibrosis annulus. Discogenic pain develops by two mechanisms. The first is due to loss of disc height as the nucleus pulposus degenerates with advancing age or trauma resulting in reactive formation of osteophytes. This diagnosis is called degenerative disc disease. The second cause is due to protrusion of the nucleus pulposus posteriorly, causing direct compression of nerve roots, which is called intervertebral disc herniation. This most often occurs in the lumbar spine due to the posterior longitudinal ligament being thinnest at L2–5 [Reference Mcguirk, Bogduk, Ballantyne, Fishman and Rathmell12].

Spinal stenosis occurs with advancing age, resultant of cumulative spinal changes that lead to progressive narrowing of the spinal canal. This pain is characteristically worsened with exercise or standing, and relieved with rest or sitting in anterior flexion. This pain often radiates from the low back into the buttocks and thighs, unilaterally or bilaterally, and can also present as neurogenic claudication. Stenosis of the neural foramen, resulting in unilateral radicular pain in a dermatomal distribution along the shoulder, arm, thigh, or leg, is classically referred to as neural foraminal stenosis. Diagnosis for both of these conditions can be confirmed by MRI, CT, or myelography [Reference Mcguirk, Bogduk, Ballantyne, Fishman and Rathmell12].

Degenerative forces lead to pain at the zygapophysial joints, also known as facet joints, exhibiting a pain prevalence of 15–45% of chronic low back pain [Reference Mcguirk, Bogduk, Ballantyne, Fishman and Rathmell12]. This pain is often near the midline, radiating into the shoulder in the cervical region and the buttock or thigh in the lumbar region. Facet loading, which is a physical examination maneuver involving hyperextension and lateral rotation of the facet joints, will reproduce the pain and provide insight to the physician that facet arthropathy is the most likely cause of the patient’s pain. Facet joint pain can be treated with a local anesthetic injection surrounding the medial branch of the posterior spinal ramus or by an intraarticular injection into the facet joints [Reference Mcguirk, Bogduk, Ballantyne, Fishman and Rathmell12].

The SI joint is the largest axial joint in the human body, linking the spine and pelvis, and can be influenced by pathologies in both the hip and the spine. SI joint arthropathy often affects the iliac side first where cartilage is the thinnest, then progresses to the sacral side [Reference Mcguirk, Bogduk, Ballantyne, Fishman and Rathmell12]. This pain will be situated over the joint line and radiates to the buttocks or low back, provoked by prolonged standing or stair climbing. On physical examination, the affected SI joint is generally tender to palpation. Multiple provocative tests are used to elicit SI joint pain, including the FABER or Patrick’s test, thigh thrust test, SI joint compression test, and Gaenslen’s test.

Basic Pain Procedures

Epidural steroid injections (ESIs) are the most common procedure in pain medicine. They provide symptomatic relief for radicular pain associated with nerve root compression or discogenic etiology, and pain relief for claudication from mild to moderate spinal stenosis. Clinical improvement is thought to be due to resolution of inflammatory edema. Under fluoroscopic guidance and sterile conditions for the interlaminar approach, a needle is advanced into the epidural space using a loss of resistance technique targeted to the location of the patient’s pain or pathology. Once the needle is engaged into the ligamentum flavum, the lateral view or contralateral oblique view is obtained, taking care to prevent insertion of the needle into the subdural or intrathecal space. Once loss of resistance is obtained, contrast is injected to ensure that the needle is not intravascular or intrathecal and indeed in the epidural space covering the expected pathology. The greatest benefit of pain relief is often achieved when medication is deposited as close as possible to the irritated nerve [Reference Bogduk, Ballantyne, Fishman and Rathmell13]. Cervical epidural steroid injections are higher risk than lumbar epidural steroid injections because the cervical region has increased vasculature, smaller epidural space, and closer proximity to the spinal cord. When cervical epidural steroid injections are done, often C7–T1 is targeted because, in general, it has the largest epidural space-to-cord ratio in the cervical region.

Transforaminal epidural steroid injections are also a good treatment for chronic radicular pain along a particular dermatomal pattern. They are thought to provide a more concentrated local distribution for radicular symptoms caused by the exiting nerve root irritation but can require multiple levels for optimal outcome. Considered relatively safe in the lumbar region, cervical transforaminal ESIs present higher vascular risks, most notably to the vertebral artery.

Caudal ESIs are commonly used to treat patients with lumbar radicular pain who have had previous lumbar neurosurgery, since the pain physician is unable to access the epidural space by the traditional lumbar approach. For this procedure, the epidural space is entered through the sacral hiatus with either a spinal or an epidural needle. The needle should not be advanced higher than the level of S3 in order to decrease the risk of dural puncture. Generally, higher volumes of injectate are used for this procedure and some physicians target the affected nerve root by advancing a catheter through the epidural needle to ensure the medication is deposited in the correct location. There is no agreed-upon volume or composition of injectate used for ESIs. However, in general, total volumes typically are 2–10 mL, depending on the specific location (cervical, lumbar, or caudal), and vary in composition with corticosteroid alone or a mixture of local anesthetic or saline [Reference Bogduk, Ballantyne, Fishman and Rathmell13]. Many will choose to use a nonparticulate corticosteroid (such as dexamethasone) to minimize the risk of spinal cord infarction or stroke [Reference Bogduk, Ballantyne, Fishman and Rathmell13].

The zygapophysial (facet) joints are innervated by the medial branches of the posterior rami of that level and the superior-level dorsal spinal nerve. Intraarticular facet joint injections can be done under fluoroscopy by injecting corticosteroid, with or without local anesthetic, into the joint. According to Bonica’s Management of Pain (4th ed.), intraarticular facet injections have never been validated or shown to have therapeutic validity, yet they are still commonly used for patients by physicians in many chronic pain practices [Reference Curatolo, Bogduk, Ballantyne, Fishman and Rathmell14].

Medial branch blocks are diagnostic for facetogenic pain. If these blocks are positive for pain relief in a series of injections, patients are then typically treated with medial branch radiofrequency ablation to provide longer relief. Cervical medial branch blocks are normally performed unilaterally to mitigate the risk of vertigo, a potential side effect of the procedure. Medial branch blocks are typically provided at multiple levels during diagnosis, as a single block would provide minimal benefit. For medial branch blocks, the needle trajectory is perpendicular to the nerve, while maximal radiofrequency or neurolysis is achieved with parallel needle-to-nerve orientation. During medial branch blocks, contrast can be used to rule out venous uptake of anesthetic, minimizing a false negative diagnosis and giving a high confidence of concordant response.

Historically, chemical neurotomy with phenol or alcohol provided nonselective neuronal destruction via Wallerian degeneration. Cryoneurotomy has also been performed, utilizing compressed carbon dioxide through an electrode to freeze sections of the medial branch nerves [Reference Govind, Bogduk, Ballantyne, Fishman and Rathmell15]. Thermal lesions by radiofrequency ablation are most common today due to their safety and efficacy profile [Reference Govind, Bogduk, Ballantyne, Fishman and Rathmell15]. High-frequency alternating current administered through an insulated needle causes oscillation of intracellular ions, resulting in coagulation of the nerve at multiple sites, which provides a mean of 6- to 18-month relief [Reference Govind, Bogduk, Ballantyne, Fishman and Rathmell15].

SI joint pain contributes to a substantial proportion of patients with chronic low back pain. SI joint injections are both diagnostic and therapeutic for this type of pain. SI joint injections introduce a corticosteroid, plus or minus local anesthetic, into the joint to quell inflammation in the joint capsule or surrounding ligamental insertions. A needle is advanced from a medial point towards the inferior SI joint, under fluoroscopy, aiming for 1–2 cm superior to the inferior aspect. While SI joint injection with local anesthetic or steroid can provide reasonable short-term relief, the systematic evaluation of this duration of pain relief is heterogenous [Reference Hansen, Manchikanti and Simopoulos16]. There is a limited, but growing, amount of evidence suggesting platelet-rich plasma injections may also provide durable relief for this type of pain [Reference Singla, Batra, Bharti, Goni and Marwaha17].