Porth's Essentials of Pathophysiology, 4e

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Musculoskeletal Function

U N I T 1 2

The scan cannot identify bone activity resulting from malignant lesions. Bone biopsy may be done to differen- tiate the lesion from osteomyelitis or a primary or meta- static bone tumor. The treatment of Paget disease is based on the degree of pain and the extent of the disease. Pain can be reduced with nonsteroidal or other anti-inflammatory agents. Suppressive agents such as the bisphosphonates and calcitonin are used to prevent further progress of the disease. Persons with Paget disease should receive adequate doses of calcium and vitamin D. Orthopedic surgery may be required for the management of pseu- dofractures, pathologic fractures, and spinal stenosis. 32 ■■ Metabolic bone disorders have their origin in the bone remodeling process that involves an orderly sequence of osteoclastic bone reabsorption, the formation of new bone by the osteoblasts, and mineralization of the newly formed osteoid tissue. ■■ Osteopenia is a condition that is common to all metabolic bone diseases. It is characterized by a reduction in bone mineral density greater than expected for age, race, or gender, and it occurs because of a decrease in bone formation, inadequate bone mineralization, or excessive bone deossification. ■■ Osteoporosis represents an increased loss of total bone mass due to an imbalance between bone absorption and bone formation that results in a decrease in bone density and diminished bone strength and is associated with an increase in bone fragility and susceptibility to fractures. Although the disease can occur as the result of a number of disorders, the most common causes are age- related changes in bone metabolism and a relative absence of estrogen in postmenopausal women. ■■ Osteomalacia and rickets represent a softening of bone due to inadequate mineralization of the bone matrix caused by a deficiency of calcium or phosphate. Osteomalacia is a disorder of adults and is caused by insufficient calcium absorption from the intestine because of lack of dietary vitamin D, resistance to the action of the vitamin, or a phosphate deficiency. ■■ Rickets, which affects children, is characterized by failure or delay in calcification of the cartilaginous growth plate, widening and deformation of the metaphyseal regions in long bones, and a delay in mineralization of trabecular, endosteal, and periosteal bone surfaces. SUMMARY CONCEPTS

Headache, tinnitus, vertigo

Thick skull

Prominent cement lines

Deafness

Pain Kyphosis

Osteoblasts

Warm skin due to hypervascularity of pagetic bone

Coxa vera

Mosaic pattern of osteosclerotic bone

Bowed femur, tibia, fibula

Waddling gait

FIGURE 44-4. Clinical manifestations of Paget disease.

nerve compression. Weight bearing may cause anterior bowings of the femur and tibia. Softening of the femo- ral neck can cause coxa vara (i.e., reduced angle of the femoral neck), which in combination with involvement of the pelvis can cause a waddling gait and secondary osteoarthritis. Mild to moderate deep, aching pain char- acteristically begins late in the course of the disease, per- sists throughout the day and at rest, and becomes worse at night. In some persons, the early hypervascularity of the pagetic bone produces warmth of the overlying skin and subcutaneous tissue. In persons with extensive dis- ease, blood flow to the bones and subcutaneous tissue can increase remarkably, leading to high-output heart failure or exacerbation of underlying cardiac disease. 3 A variety of tumor and tumorlike conditions develop in pagetic bone, the most dreaded of which is sarcoma. Osteogenic sarcomas occur in 5% to 10% of persons with extensive disease. 3 The bones most often affected, in order of frequency, are the femur, pelvis, and humerus. 4 Diagnosis and Treatment. Diagnosis of Paget disease is based on characteristic bone deformities and x-ray changes. Elevated levels of serum alkaline phosphatase and urinary hydroxyproline support the diagnosis, and continued surveillance of these levels may be used to monitor the effectiveness of treatment. Bone scans are used to detect the rapid bone turnover indicative of active disease and to monitor the response to treatment.