Figure 102

Severe osteoporotic fracture. Lateral X-ray showing that both the superior and inferior endplates have been affected leading to a kyphotic deformity.

disease progression. Over the course of time, patients develop additional fractures that may result in kyphotic deformities leading, in a significant percentage of patients, to chronic persistent back pain and, at times, to neurological complications and pulmonary dysfunction.

When osteoporosis or vertebral fractures are detected, systemic diseases such as hematological malignancies (multiple myeloma or metastatic disease) should be excluded. The work-up should include sedimentation rate, complete blood count, serum calcium, phosphorus, uric acid, serum and urine protein electrophoresis, and liver function tests. Osteoporosis work-up should also include blood levels of 25-hydroxyvitamin D, parathyroid hormone, osteocalcin (a bone formation marker), and 24-hour urine calcium excretion.

Imaging Studies

Bone density studies using dual photon X-ray absorptiometry (DEXA) can confirm the presence of osteoporosis and quantify its severity.

Plain films are not sensitive and remain normal in the early stages of osteoporosis. Up to 50-70% of bone loss can occur before osteoporosis is detectable on plain films. The main features of spinal osteoporosis are cortical bone thinning and resorption of bone trabeculae expressed on plain X-rays as decreased bone density. The bones appear more radiolucent; they look washed out or darker on plain films. Thinning of the cortical bone can be easily identified on CT images, while trabecular bone resorption brings about a lower density due to the changed relation of bone/bone marrow quantities.

The hallmark of osteoporotic vertebral fracture is loss of vertebral body height. This can be best viewed on lateral spine films. When the vertebral body loses 20% or more of its height, a vertebral fracture is present. These fractures occur when the axial load exceeds the osteoporotic vertebral body strength.

Thorough inspection of plain films may increase the diagnostic yield. Special attention should be devoted to the shape of neighboring vertebral bodies. Mild endplate deformities and lack of endplate parallelism may point to a fracture at a rather early stage (Figure 10-1).

A wedge fracture or anterior compression fracture occurs when height is lost at the anterior portion of the vertebral body while the posterior vertebral wall and the neural arch remain intact. These fractures are very common in osteoporotic individuals, are found in the thoracic as well as the lumbar region, and result from axial loading in flexion. Frequently, only the superior endplate is affected. At times, both, the superior and the inferior endplates are involved (Figure 10-2). These fractures have been considered stable and were not addressed appropriately in the past. Recently it has been observed that osteoporotic fractures in which the anterior wall of the vertebra "swells" or "projects" forward have a tendency to collapse due to involvement of both the anterior and the middle vertebral columns. When the anterior as well as the posterior walls of the vertebral body are affected, the fracture is termed a burst fracture. Burst fractures are clinically significant because they may be associated with a ret-ropulsed fragment—a bone fragment that is pushed posteriorly into the spinal canal—leading to neurological compromise (Figures 10-3 and 10-4). When height is lost in the middle of the vertebral body leaving the periphery more or less intact, a biconcave-shaped vertebra is seen (Figure 10-5).

Schmorl's nodes, which represent intravertebral disc herniation through the endplate region, may be misread and erroneously interpreted as vertebral fracture. They can occur at the superior as well as the inferior endplate, and over time may be surrounded by a sclerotic bony rim. Schmorl's nodes are most frequently found in the lower thoracic and upper lumbar vertebrae. Commonly they are an incidental finding with no clinical significance (Figure 10-6).

CT and MRI studies provide invaluable assistance in determining a vertebral fracture's age and in establishing its etiology: osteoporotic or pathological. Establishing the fracture's age is important as it enables the clinician to determine whether the symptoms are related to the fracture or not. Furthermore, it provides some guidelines for treatment, such as vertebroplasty or kyphoplasty. The age of the fracture cannot be accurately determined by radiographs only. MRI is the best available modality to determine the fracture's age. The presence of bone marrow edema around the fracture site is a good indication that the fracture is acute. On T1-weighted images (T1WI) the edematous

Potts Disease Thoracic Spine Image

FIGURE 10-4 Sagittal T1WI MR showing an osteopo-

Sagittal reformatted CT scan showing a rotic spine with three biconcave verte-severely osteoporotic spine with fractures brae (stars). Courtesy Dr. N. Haramati. at T11, L2, and L5. Both the T11 and L2 fractures have a retropulsed segment that narrows the spinal canal.

FIGURE 10-4 Sagittal T1WI MR showing an osteopo-

Sagittal reformatted CT scan showing a rotic spine with three biconcave verte-severely osteoporotic spine with fractures brae (stars). Courtesy Dr. N. Haramati. at T11, L2, and L5. Both the T11 and L2 fractures have a retropulsed segment that narrows the spinal canal.

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