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Identifying serious causes of back pain: Cancer, infection, fracture

Cleveland Clinic Journal of Medicine. 2008 August;75(8):557-566
August 1, 2008|Cleveland Clinic Journal of Medicine
Krzysztof Siemionow, MD;Michael Steinmetz, MD;Gordon Bell, MD;Hakan Ilaslan, MD;Robert F. McLain, MD
Author and Disclosure Information

Krzysztof Siemionow, MD
Department of Orthopaedic Surgery, Cleveland Clinic

Michael Steinmetz, MD
Department of Neurosurgery, and Cleveland Clinic Center for Spine Health, Cleveland Clinic

Gordon Bell, MD
Vice-Chairman, Department of Orthopaedic Surgery, and Associate Director, Cleveland Clinic Center for Spine Health, Cleveland Clinic

Hakan Ilaslan, MD
Department of Radiology, Cleveland Clinic

Robert F. McLain, MD
Professor, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University; Director of Spine Fellowship Program, Department of Orthopaedic Surgery and Cleveland Clinic Center for Spine Health, Cleveland Clinic

Address: Robert F. McLain, MD, Cleveland Clinic Center for Spine Health, Department of Orthopaedic Surgery, A41, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195; e-mail mclainr@ccf.org

ABSTRACTMost patients with back pain have a benign condition, but tumors, infections, and fractures must be considered during an initial evaluation because overlooking them can have serious consequences. This article discusses the presentation and diagnostic strategies of these serious causes of back pain.

KEY POINTS

  • A primary tumor or metastasis to the spine tends to cause unremitting back pain that worsens at night and is accompanied by systemic disease and abnormal laboratory findings.
  • Infection typically causes focal pain, an elevated erythrocyte sedimentation rate (the most sensitive laboratory test) and C-reactive protein level, and sometimes neurologic signs and symptoms.
  • Fractures cause focal pain and should be suspected especially in older white women and patients who take corticosteroids or who have ankylosing spondylitis.
  • Plain radiography can help detect fractures, but magnetic resonance imaging is needed to evaluate spinal tumors, soft tissue infections, and epidural abscesses, and to further evaluate neural compression due to fractures.

Cancer usually elevates the ESR, CRP

If cancer is suspected, initial tests should include a complete blood cell count, erythrocyte sedimentation rate, C-reactive protein level, urinalysis, prostate-specific antigen level, and fecal occult blood testing. Normal results can considerably relieve suspicion of cancer: the erythrocyte sedimentation rate and C-reactive protein level are almost always elevated with systemic neoplasia.

Figure 1. A 43-year-old man with a 2-week history of progressive back pain and an abdominal mass. Sagittal CT scan shows an osteolytic lesion of the L3 vertebral body (arrow). The primary tumor was renal. Fracture of the vertebral end plate (arrowheads) may cause first symptoms of pain.
Other initial tests include a complete blood cell count and chemistry panel. If laboratory studies reveal anemia, hypercalcemia, and elevated levels of alkaline phosphatase, concern should increase. Chest radiography, abdominal computed tomography (CT) (Figure 1), and mammography for women are needed if laboratory results are abnormal. Plain radiographs are the first imaging study of the spine to obtain. Compression fractures, soft tissue calcifications, or focal loss of bone mineralization suggests tumor. Abnormal results on serum and urine protein electrophoresis increase the likelihood of multiple myeloma or plasmacytoma, but normal results do not rule out monoclonal gammopathy of uncertain significance.

Imaging tests

Unfortunately, spinal tumors cannot be well visualized on radiographs until significant destruction has occurred.15

A bone scan can usually detect tumors other than the purely lytic ones such as myeloma and has a sensitivity of 74%, a specificity of 81%, and a positive predictive value of 64% for vertebral metastasis in patients with back pain.16

Figure 2. A 63-year-old woman with history of hepatocellular carcinoma who presented with bilateral leg weakness and debilitating back pain. T2-weighted MRI shows pathologic compression fracture of the L2 vertebral body with retropulsion of fracture fragments into the canal and severe central canal stenosis (arrow).
Magnetic resonance imaging (MRI) is the best imaging study for evaluating spinal tumors because it can show the status of the bone marrow and has excellent contrast resolution in soft tissue (Figure 2).17,18 It can show vertebral bone marrow infiltration by tumor cells as well as soft tissue masses in and around the spinal column. Bone marrow invaded by a neoplasm is characterized by increased cellularity, resulting in a decreased signal on T1-weighted images and a high signal on T2-weighted images. Intravenous gadolinium further increases the contrast between a tumor and normal tissues and is important for characterizing and grading tumors.19

INFECTION CAN BE INDOLENT OR ACUTE

Spinal infection is a serious condition that can take an indolent, smoldering course or, alternatively, can erupt into sepsis or rapidly progressive vertebral destruction. Although the latter conditions are hard to miss, early diskitis and osteomyelitis can be difficult to differentiate from idiopathic back pain. In a series of 101 patients with vertebral osteomyelitis, misdiagnosis occurred in 33.7%, and the average delay from the onset of clinical manifestations to diagnosis was 2.6 months.20 Tuberculosis can be even more elusive: in a series of 78 patients diagnosed with definite or probable tuberculous vertebral osteomyelitis, the mean delay to diagnosis was about 6 months.21

Acute spinal infections are most often pyogenic; chronic infections may be pyogenic, fungal, or granulomatous.

Vertebral osteomyelitis accounts for 2% to 7% of all cases of osteomyelitis and is an uncommon cause of back pain.22 Any source of infection (eg, dental abscess, pneumonia) can seed the spine; urinary tract infection is the most common. Patients with immunocompromise or diabetes are most at risk.23 The onset is usually insidious with focal back pain at the level of involvement.

History and physical examination reveal localized pain

Spinal infections typically cause pain that is worsened with weight-bearing and activity and is relieved only when lying down. Chronic infection is usually associated with weight loss, fatigue, fevers, and night sweats.

Pain is usually well localized and reproduced by palpation or percussion over the involved level. Severe pain can sometimes be elicited by sitting the patient up or by changing the patient’s position. Focal kyphosis may be detectable if the vertebra has collapsed.

In a series of 41 patients with pyogenic infectious spondylitis, 90% had localized back pain aggravated by percussion, 59% had radicular signs and symptoms, and 29% had neurologic signs of spinal cord compression, including hyperreflexia, clonus, the Babinski sign (extension of the toes upward when the sole of the foot is stroked upwards), or the Hoffmann sign (flexion of the thumb elicited by flicking the end of a middle finger).24

LABORATORY RESULTS TYPICALLY INDICATE INFECTION

The erythrocyte sedimentation rate is the most sensitive test for infection, and an elevated rate may be the only abnormal laboratory finding: Digby and Kersley25 found that the rate was increased in all of 30 patients with nontuberculous pyogenic osteomyelitis of the spine. The C-reactive protein level is also usually elevated, but 40% of patients have a normal white blood cell count.25 Results of other laboratory tests are typically in the normal range. Tuberculin skin testing should be done for patients at high risk of the disease (eg, immigrants from areas of endemic disease, non-Hispanic blacks, immunocompromised patients, and those with known exposure to tuberculosis). Patients with high fever, chills, or rigors should have cultures taken of blood, urine, and sputum and from any intravenous lines.

Imaging changes may not appear for months

Figure 3. A 32-year-old woman with systemic lupus erythematosus who is on chronic steroid therapy and who has a 6-week history of back pain. T2-weighted sagittal MRI shows a disk space infection at L2–L3, with ventral paraspinal soft tissue enhancement consistent with early abscess formation (arrows).
Radiographic findings characteristic of osteomyelitis are not apparent for at least 4 to 8 weeks after the onset of infection.26 Narrowing of the disk space is the earliest and most consistent finding but is nonspecific.27 Pyogenic infection is often heralded by rapid disk destruction and disk space narrowing. MRI is as accurate and sensitive as nuclear medicine scanning (sensitivity 96%, specificity 93%, accuracy 94%).28 MRI can help differentiate degenerative and neoplastic disease from vertebral osteomyelitis29 and provides better imaging than CT for soft-tissue infections (Figure 3).

CT, on the other hand, may be better for showing the extent of bone involvement. In cases of vertebral osteomyelitis and intervertebral disk space infection, simultaneous involvement of the adjacent vertebral end plates and the intervertebral disk are the major findings.30

Signs of infection using T1-weighted MRI include low-signal marrow or disk spaces within the vertebral body, loss of definition of end plates (which appear hypointense compared with the bone marrow), and destruction of the cortical margins of the involved vertebral bodies. T2-weighted MRI typically discloses high signals of the affected areas of the vertebral body and disk. Contrast should be used to increase specificity; enhancement may be the first sign of an acute inflammatory process.31

CT and MRI can help identify sequestra, perilesional sclerosis, and epidural or soft tissue abscesses. Guided biopsy may be needed to differentiate between abscess, hematoma, tumor, and inflammation.

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