Multiple myeloma, the most common primary malignant bone tumor in adults, may be associated with profound generalized axial and appendicular osteopenia. Myeloma cells produce potent osteoclast-activating factors that stimulate bone resorption. A particularly lytic form of multiple myeloma is associated with secretion of Dkk-1, an inhibitor of Wnt signaling. Multiple myeloma should be suspected in any person older than age 50 who has symptomatic osteopenia, anemia, proteinuria, and a sedimentation rate greater than 100 mm/hr. Serum protein electrophoresis helps establish the diagnosis, but if the results are inconclusive, urinary immunoelectrophoresis should be performed. Approximately 1% of myelomas are nonsecretory, and bone marrow biopsy is required in all patients. Leukemia, lymphoma, and systemic mastocytosis may also be associated with osteoporosis.

CLINICAL MANIFESTATIONS AND PROGRESSIVE SPINAL DEFORMITY

A long latent period often precedes the clinical symptoms or complications of osteoporosis (see Plates 3-28 and 3-29). Skeletal resources are depleted, often for decades, before the bone mass is so compromised that the skeletal framework can no longer withstand everyday mechanical stresses.

The entire skeleton is susceptible to age-related and postmenopausal bone loss, but trabecular bone remodeling is greater in regions such as the thoracic and lumbar vertebral bodies, ribs, proximal femur and humerus, and distal radius. The most prevalent complications are vertebral compression fractures.

VERTEBRAL COMPRESSION FRACTURES

Approximately two thirds of all vertebral fractures are asymptomatic. An important clue to occult vertebral fractures is height loss. A loss of height from peak height of more than 1.5 inches is associated with an increased risk of vertebral fractures. One third of patients with vertebral compression fracture have acute back pain, which is often precipitated by routine activities—standing, bending, lifting—that under normal circumstances would not be stressful enough to cause a fracture.

The onset of pain is sudden. Spinal movement is severely restricted. The pain intensifies with sitting or standing and is exacerbated by coughing, sneezing, and straining to move the bowels. Bed rest in the fully recumbent position provides relief.

Radiculopathies may occur with thoracic or upper lumbar compression fractures and cause pain that radiates anteriorly along the costal margin of the affected nerve root.

Approximately 30% of patients continue to be plagued with chronic, dull, aching, postural pain in the midthoracic and upper lumbar regions. As each episode of segmental vertebral collapse causes progressive kyphosis, the patient’s height may decrease. Both kyphosis and decreased height are reliable clinical signs of the late stage of the disease. With severe osteoporosis and multiple compression fractures, the lower ribs may rest on the iliac crest (see Plate 3-29).

Progressive vertebral compression fractures cause a decreased size of the thoracic and abdominal cavities and result in hypoventilation. Early satiety as well as abdominal protrusion secondary to severe lumbar vertebral collapse may occur.