Down to the boneOsteoporosis is characterized by a reduction in the bone matrixand in remineralization, resulting in soft bones that fracture easily.Bone mass is lost because of an imbalance between bone resorp-tion and formation.Cancellous bone, the inner layer of spongy bone, is composedof trabeculae, sharp, needlelike structures forming a meshwork ofinterconnecting spaces. Trabeculae have a larger surface volumethan compact bone (the outer layer of dense bone) and thereforeare lost more rapidly as bone mass decreases. This loss leads tofractures.What to look forBone fractures are the major complication of osteoporosis. Frac-tures occur mostly in the vertebrae, femur, and distal radius. Signsof redness, warmth, and new sites of pain may indicate new frac-tures.Patient profileThe patient is typically postmenopausal or has one of the condi-tions that cause secondary osteoporosis. She may report that sheheard a snapping sound and felt a sudden pain in her lower backwhen she bent down to lift something. Alternatively, she may saythat the pain developed slowly over several years. If the patienthas vertebral collapse, she may describe a backache and pain radi-ating around the trunk. Movement or jarring aggravates the pain.Don’t get bent out of shapeThe patient may have a humped back (dowager’s hump); the cur-vature worsens as repeated vertebral fractures increase spinalcurvature. The abdomen eventually protrudes to compensate forthe changed center of gravity. The patient commonly reports agradual loss of height, decreased exercise tolerance, and troublebreathing. Palpation may reveal muscle spasm. The patient mayalso have decreased spinal movement, with flexion more limitedthan extension. (See Height loss in osteoporosis and Treatingosteoporosis, page 238.)236MUSCULOSKELETAL SYSTEM
What tests tell youA diagnosis excludes other causes of bone disease, especiallythose that affect the spine, such as cancer or tumors. These testshelp confirm a diagnosis of osteoporosis:•X-ray studies show characteristic degeneration in the lower ver-tebrae. Loss of bone mineral appears in later disease.•Serum calcium, phosphorus, and alkaline phosphatase levels re-main within normal limits; parathyroid hormone levels may be ele-vated.•Bone biopsy allows direct examination of changes in bone cells.•Computed tomography scan allows accurate assessment ofspinal bone loss.237MUSCULOSKELETAL DISORDERSHeight loss in osteoporosisUsually, a patient with osteoporosis loses height gradually, as shown below. Height may be reduced as much as 7 .5 65 35 0HeightAge406070Dowager’s humpdevelops whenrepeated vertebralfractures increase thespinal curvature.The abdomenbegins to protrude tocompensate for thecenter of gravity.
•Radionuclide bone scans display injured or diseased areas asdarker portions.
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