Thoracic and Lumbar Spine

Lauren M. Post

Angela Hua

CLINICAL CHALLENGE

In the emergency department (ED), low back pain is one of the most common musculoskeletal chief complaints and affects approximately 80% of adults at some point in their lives.¹ The complaint of low back pain was responsible for approximately 4% of ED visits from 2000 to 2016.² “Spinal conditions,” which include neck and back pain, comprise the third largest portion of total national health spending in the United States, behind diabetes and heart disease.³ The majority of patients presenting to the ED will complain of neck or lower back pain rather than thoracic-level pain. Thoracic back pain has been documented less frequently, with < 20% of people reporting symptoms within their lifetime.⁴ Many will have benign etiologies that will resolve with conservative management, but the small percentage that requires immediate intervention must be quickly identified. In addition, patients with nonemergent conditions require a well-thought out strategic plan to manage their condition and maximize function.

A broad differential diagnosis and an evaluation that is systematic without bias is fundamental to managing low back pain; see Table 14.1. In addition to primary spinal pathology, processes that may refer pain to the back must be considered. Failure to address these alternative diagnoses in the face of localized pain is a common oversight in many case reviews.⁵ Because of the lower frequency of thoracic back pain, vascular emergencies and other causes of referred pain must remain high on the differential for patients with this complaint.

PATHOPHYSIOLOGY

Musculoskeletal strain, arthritic degeneration, spinal stenosis, and stable fractures may be painful and contribute to overall morbidity, but are not usually associated with acute neurologic deficits. Many of the more serious causes of back pain can be categorized as being “compressive,” with the inciting pathology filling the limited amount of space within the spinal canal. Figure 14.1 shows the relative location of the potential spaces in and around the spinal column.

The spinal cord tapers to the conus medullaris around the L1 level; the cauda equina is the bundle of nerve roots that continues to innervate the lower extremities, perineum, and bladder. Compressive lesions, including herniated disks, tumors, hematomas, and abscesses, can fill these spaces and exert pressure on the cord and nerve roots. This pressure may reduce blood flow, inducing ischemia of neural tissue and may cause transient, acute dysfunction as well as permanent infarction if not decompressed. Some of the more benign pathologies may develop a compressive component as well and may progress to requiring surgical intervention.

TABLE 14.1 Differential Diagnosis of Adult Patients Presenting with Back Pain

Primary Benign	Primary Serious
Stable fracture Sprains and strains Degeneration Spinal stenosis Posterolateral disk herniation	Unstable fracture Malignancy Epidural metastatic disease Intradural metastatic disease Intramedullary tumor Infection Osteomyelitis Epidural abscess Infectious diskitis Hematoma Epidural Subarachnoid Central disk herniation
Secondary^a
Vascular Aneurysm Dissection Thromboembolism Gastrointestinal Malignancy Pancreatitis Gallbladder disease Peptic ulcer Cardiac ischemia Pulmonary Malignancy Infection Retroperitoneal Malignancy Renal colic Infection Hemorrhage Localized abscess
^aMay still be considered serious.

Radiculopathy, the pain and weakness associated with nerve root impingement, results from one of the compressive mechanisms of injury. Spinal disk disease is usually benign and self-limited, with approximately 80% to 90% of cases getting symptomatic relief with medical management. Lumbar disk disease results from changes in disk alignment and integrity, resulting in abnormal bony movement and pain. Compression of microvasculature feeding the spinal cord and nerve roots produces ischemia within these structures. The resulting inflammation and degradation cause an increase in inflammatory mediators, that is, cytokines, tumor necrosis factor alpha (TNF-α), and macrophages. This process causes loss of disk and foraminal height, the inability to cushion the spinal column, and neuropathic pain. Increased mechanical stress also causes bony distortion at the facets, and osteophyte formation. A combination of these factors leads to the clinical presentation of lumbar radiculopathy, pain, and weakness as a result of nerve root impingement. Epidural compression may occur at the levels of the spinal cord, conus medullaris, or cauda equina. This compression occurs most commonly from disk herniation, followed by tumor and infection, with a small percentage caused by hemorrhage.⁶^,⁷ Conus medullaris syndrome occurs when there is a compressive force from T12 to L2, and cauda equina syndrome from compression of the nerve roots from L3 to L5. Both of these syndromes may present as back pain with neurologic deficits including urinary retention and lower extremity weakness.

Figure 14.1: Anatomy of the spinal column.

PREHOSPITAL CONSIDERATIONS

When the emergency medical system is activated, the prehospital provider becomes the first point of triage, with the mechanism of injury determining the initial resources and the transport destination. Traumatic injuries require a rapid primary survey, with an evaluation for the presence of additional injuries and mechanical stabilization of potential fractures. These patients may require
immobilization and log-roll precautions to prevent any further complications. Patients with concomitant head injuries or meeting trauma activation criteria should be transported to a facility with appropriate specialty coverage. Because the etiology of atraumatic back pain is varied, a more comprehensive secondary survey may be needed to determine stability. Abnormal vital signs or motor deficits can provide important information before arrival at the receiving ED, and also guiding further evaluation. It is also critical that the prehospital provider attempt to obtain additional medical history, medications, and alcohol or substance use.

PEDIATRIC ISSUES

The pediatric population adds another level of complexity to the evaluation of back pain. Table 14.2 lists some of the more common causes of back pain in this group. Musculoskeletal causes of thoracic back pain tend to be more frequent in the adolescent population than in other pediatric age groups.⁴ Overuse injuries are frequent, and the rapid growth of adolescence can cause pain as well as potentially worsening scoliosis. Interestingly, the use of school backpacks and their increasing weight has been suggested as contributing to the preponderance of musculoskeletal back pain in older children and adolescents.⁴ Younger patients tend not to have the degenerative changes present in adults, making acute disk herniation a less likely process. The pediatric spine is more flexible than in adulthood, leading to spinal cord injuries without radiographic abnormality (SCIWORA) in cases of trauma.

As in adults, infection and malignancy should be considered in a patient presenting with acute back pain. Primary pediatric malignancies such as lymphomas and leukemias frequently cause back pain. Unlike many adult malignancies, cancers affecting children appear less likely to metastasize to the bony spine. Infectious diskitis and infectious spondylodiskitis are rare but potentially devastating infections of the intervertebral disk and surrounding vertebral bodies. Most cases are due to hematogenous spread of Staphylococcus aureus; however, in endemic areas, Mycobacterium tuberculosis is also a frequent cause. The clinical presentation of these infections is usually nonspecific, with low-grade fever associated with lower back pain and stiffness. Neurologic deficits are not usually present until later stages, when nerve compression occurs or the infection breaks into
the spinal canal. Most cases are mild and treated with rest and symptomatic pain relief, but if left untreated, these infections can lead to permanent deformities, spinal instability, or extension into the spinal canal.

TABLE 14.2 Causes of Back Pain in Children and Adolescents

Mechanical	Fracture Overuse Herniated disk Scoliosis
Tumors	Osteoid osteoma Bone cyst Ewing tumor Osteogenic sarcoma Neuroblastoma Wilms tumor Lymphoma Leukemia
Infection/Inflammation	Diskitis/spondylodiskitis Osteomyelitis Collagen vascular diseases Ankylosing spondylitis
Referred pain	SCFE Hip/knee abnormalities Gait abnormalities causing strain Additional causes of secondary pain as noted in Table 14.1
Slipped capital femoral epiphysis SCFE.

Conditions referring pain into the back are similar to those in adults. In addition, children with genetic conditions affecting the connective tissue such as Marfan and Ehlers-Danlos syndromes may also present with back pain due to spinal instability or mechanical stress.

APPROACH/THE FOCUSED EXAMINATION

The history in patients with back pain should include a review of systems, prior medical problems, time course, modifying factors, associated symptoms, and prior episodes. Specifically asking about neurologic changes, reviewing medications, and previous records will help narrow the differential diagnosis. Figure 14.2 provides a framework for evaluating the patient presenting with acute back pain. The use of “red flags” to suggest serious underlying pathology in back pain is a useful tool (Table 14.3). These factors help identify patients at risk for more serious etiologies of back pain, including malignancy, infection, and hemorrhage.

A comprehensive physical examination including, but not limited to, neurologic and musculoskeletal systems is required. General observation of patients complaining of back pain can contribute to a differential diagnosis and subsequent workup. Watching during common movements such as walking, sitting, and standing can provide insight into the degree of discomfort and limitation of function. Many patients with mechanical low back pain will find certain positions or postures more comfortable. Observing for guarding or avoidance of specific movements may also be helpful, because this may suggest a referred or intra-abdominal cause of the pain. In addition, looking for general changes in physical appearance such as muscle wasting or the stigmata of substance abuse can aid in stratifying these patients.

Vital signs are a critical component of the evaluation of back pain, and may provide important clues to the cause of pain that may otherwise be overlooked. Elevated temperature or recent history of fevers highly suggests an infectious process. In combination with the complaint of back pain, a fever may be the only other evidence of infection, especially within the deeper structures. Although uncommon, some patients may report a recent fever but present as afebrile. The measurement of blood pressure helps in screening for intra-abdominal catastrophes that can present as back pain. Hypertension is a risk factor for both aortic dissection and abdominal aortic aneurysm, and blood pressure control may precipitate or worsen a developing process. In the initial stages of these conditions, a patient may present with an elevated blood pressure, but as the dissection extends or the aneurysm ruptures, hypotension will likely be found. Although these conditions often are associated with changes in blood pressure, a normal reading does not eliminate the need for a high level of suspicion.

Abdominal pain is often difficult for patients to describe completely, and when back pain accompanies it or is more prominent, the back pain may become the focus of the complaint. In addition, some intrathoracic and intra-abdominal processes, such as myocardial infarctions and aortic dissections, may not present with their classic symptoms, but rather referring pain into the back. Uncovering upper quadrant tenderness may suggest gall bladder or peptic ulcer disease, pancreatitis, or bowel obstruction. A pulsatile abdominal mass would necessitate an investigation for abdominal aneurysm. Lower quadrant tenderness may suggest appendicitis or diverticulitis with pain referred to the back. In addition, suprapubic tenderness or the presence of a palpable bladder could suggest urinary retention, increasing concern for spinal cord compression or cauda equina syndrome. Patients with urinary retention should be examined for rectal tone and perineal numbness.

An examination of the back should include inspection of the skin, palpation of bony areas, palpation of paraspinal musculature, and an assessment of the patient’s range of motion. Skin examination should look for changes or erythema that would suggest herpes zoster or other infectious processes as well as ecchymosis that would indicate trauma. Bony point tenderness, misalignment or step offs may localize traumatic injuries or infection. The spine should also be examined for abnormal curvature because scoliosis and subsequent degenerative changes produce pain. This is especially relevant in the pediatric population where back pain may be the earliest indication of scoliosis. Palpation of the paraspinal musculature may reveal muscle spasm.

Figure 14.2: Clinical pathway for the evaluation of acute back pain. CBC, complete blood count; CC, chief complaint; CT, computed tomography; ESR, erythrocyte sedimentation rate; LFT, liver function test; MRI, magnetic resonance imaging; NSAIDs, nonsteroidal anti-inflammatory drugs; PT/PTT/INR, prothrombin time/partial prothrombin time/international normalized ratio; ROS, review of systems; UA, urine analysis; US, ultrasound; VS, vital signs.

TABLE 14.3 Red Flag History and Physical Examination Findings

Finding	Increased Concern
Age < 20 yr	Infection, malignancy
Age > 50 yr	Malignancy, vascular disease
Sudden severe pain, especially thoracic	Vascular catastrophe, infection
Unexplained weight loss	Infection, malignancy
Night sweats or unexplained fever	Infection, malignancy
Immunocompromised state (HIV, steroids, immunosuppressing drugs)	Infection
Prior medical history (malignancy, IV drug abuse, infection, AAA)	Metastatic disease, infection/abscess, retroperitoneal hemorrhage
Urinary retention, incontinence, saddle anesthesia	Cauda equina
Motor deficit	Cord or nerve root compression
Pain at rest or at night	Infection, malignancy
Osteoporosis, trauma, steroid use	Fracture
Anticoagulant/antiplatelet use (especially with recent spinal injection)	Hemorrhage, hematoma
AAA, abdominal aortic aneurysm; HIV, human immunodeficiency virus; IV, intravenous.

The neurologic examination should always include an evaluation of sensation, strength, and reflexes in the lower extremities. This allows the examiner to document neurologic deficits, to localize the lesion, and provides a baseline for repeated evaluations. Examination techniques, including the straight leg raise, may suggest increased dural tension as a cause of radiculopathy. The musculoskeletal evaluation should include an assessment of the lower extremity joints. Primary pathology or altered mechanics of the hip, knee, or ankle joints may cause secondary back pain. The pain of lumbar radiculopathy is often described as sharp or burning and follows the area of sensory innervation. Nerve dysfunction can present as motor weakness, sensory loss, or a combination of both. Pairing examination findings with known levels of innervation will lead the physician to a possible location of the lesion (Table 14.4).

Physical examination findings may vary depending on the degree of compression over one or more spinal levels. Owing to the overlap in anatomy, the clinical presentation of cauda equina and conus medullaris syndromes can be similar. Both syndromes are due to compression of the spinal cord and nerves exiting at the L1 to L5 levels. Symptoms of conus medullaris compression may include upper motor neuron signs, producing increased tone and reflexes in the lower extremities.
Compression of the cauda produces lower motor neuron signs in the lower limbs and can cause neurogenic bladder, loss of rectal tone, and saddle anesthesia. The most common finding is that of urinary retention with or without overflow incontinence.⁸^,⁹ Other clinical features seen may include back pain, sensory loss, incontinence, or bilateral sciatica.⁶^,⁸^,⁹ Table 14.5 summarizes the differences in these two syndromes. If a compression syndrome is suspected, urinary retention should be evaluated by bladder scan, postvoid residual, or Foley catheter placement. Emergent computed tomography (CT) myelogram, or magnetic resonance imaging (MRI) is indicated to confirm the diagnosis. Owing to the incidence of metastatic disease and skip lesions, imaging of the entire spinal column is preferred, if possible, especially in the pediatric population.¹⁰

TABLE 14.4 Localizing the Lesion

Disk Level	Location of Pain	Motor Deficit
T12-L1	Inguinal region, medial thigh	Usually none
L1-2	Anterior and medial thigh	Mild quadricep weakness Mildly diminished patellar reflex
L2-3	Anterolateral thigh	Quadricep weakness Diminished patellar reflex
L3-4	Posterolateral thigh Anterior tibia	Quadricep weakness Diminished patellar reflex
L4-5	Dorsal foot	Extensor weakness of ankle and great toe
L5-S1	Lateral foot	Diminished Achilles reflex

LABORATORY AND DIAGNOSTIC STUDIES

Laboratory testing, in cases of low back pain, is usually not helpful in most patients. Urine pregnancy testing should be considered in all appropriate patients both to facilitate any imaging and to evaluate for an intra-abdominal cause of the pain. Urinalysis can be used to support a clinical decision of renal colic or pyelonephritis as a source of referred pain. If infection or malignancy is suspected, a complete blood count (CBC), erythrocyte sedimentation rate (ESR), and blood cultures may be indicated. Anticoagulated patients and those in whom intervention may be necessary should have a coagulation profile and blood bank typing performed. See the Evidence section for further discussion of the utility of laboratory tests.

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