Metabolic Diseases

Jeffrey J. Peterson

Thomas H. Berquist

▪ OSTEOPOROSIS: BASIC CONCEPTS

KEY FACTS

Osteoporosis is a reduction in bone mass. It is the most common clinical bone disease.
Osteoporosis affects 75 million people in the United States, Europe, and Japan, accounting for 1.5 million fractures per year.
Osteoporosis is categorized as generalized, regional, or local. Table 13-1 summarizes the causes of osteoporosis.
Radiographic and imaging features vary with the type of osteoporosis and site.

Table 13-1 CAUSES OF OSTEOPOROSIS

Generalized		Regional/Localized
Senile, postmenopausal		Disuse atrophy
Endocrine disorders		Reflex sympathetic dystrophy
	Thyroid dysfunction	Transient regional osteoporosis
	Parathyroid dysfunction	Migratory osteoporosis
	Cushing disease
	Hypogonadism
Medications
	Steroids
	Heparin
Chronic liver disease Anemias Multiple myeloma Environmental factors
	Smoking Alcohol abuse Nutritional deficiency Low calcium intake
Idiopathic

SUGGESTED READING

Eastell R. Treatment of postmenopausal osteoporosis. N Engl J Med. 1998;338:736-746.

Golob AL, Laya MB. Osteoporosis: screening, prevention, and management. Med Clin North Am. 2015;99(3):587-606.

Guglielmi G, Muscarella S, Bazzocchi A. Integrated imaging approach to osteoporosis: state-of-the-art review and update. Radiographics. 2011;31(5):1343-1364.

▪ OSTEOPOROSIS: GENERALIZED

KEY FACTS

Generalized osteoporosis may be the result of a long list of disorders (Table 13-1).
Senile or postmenopausal osteoporosis usually develops in women aged more than 50 years. Fracture risk approaches 60% in females aged more than 50 years.
Endocrine disorders (Table 13-1) are the most common cause of secondary osteoporosis. The five most common endocrine disorders are hypogonadism, insulinopenia, hyperparathyroidism (HPT), hyperthyroidism, and hypercortisolemia.
Imaging of osteoporosis is typically accomplished with routine radiographs and bone mineral density measurements (dual-energy X-ray absorptiometry [DXA]). Computed tomography and ultrasound have also been used. However, management decisions and patient monitoring are most often accomplished with DXA.
Combining DXA data with clinical factors (age, prevalent fractures, family history of fractures, low body mass index, increased risk of falls, and steroids) allows estimation of fracture probabilities over 5- and 10-year periods.
- Radiographic features: Spine and proximal extremities are primarily involved. Thin cortical bone, vertebral contour abnormalities (endplate compression, compression fractures). Coarsened trabecular pattern in the pelvis and trabecular resorption in the proximal femurs.
- DXA: Lumbar spine, femoral neck, and wrists are typically studied. Bone density is compared with density in healthy 30-year-old persons (T score) and the patient’s age group (Z score).
  - Normal: > -1
  - Osteopenia: < -1 to -2.5
  - Osteoporosis: < -2.5
Treatment may include ralozifene (mean increase in spine density 2.6% over 4 years), bisphosphonates (mean increase 10% to 15% after 7 to 10 years), teriparatide (13% density increase after 18 months), or strontium ranelate (14.5% density increase after 3 years). Treatments may reduce fracture risk by 30% to 50%. DXA studies are used to monitor therapy at 1- to 2-year intervals.

FIGURE 13-1. Osteoporosis. (A) Normal right hip with trabecular pattern well demonstrated. (B) Osteoporotic right hip with poorly defined trabeculae (arrows).

FIGURE 13-2. (A) Lateral thoracic spine with osteoporosis and compression fractures. (B) Lateral lumbar space shows endplate compression (fish vertebra) with biconcave appearance.

FIGURE 13-3. Dual-energy X-ray absorptiometry (DXA) examination in a 76-year-old man with lumbar (A) and hip (B) T scores of -1.5 and -3.1 for the lumbar spine and right hip, respectively. Findings indicate osteopenia in the spine and osteoporosis for the hip.

FIGURE 13-3. (continued)

FIGURE 13-4. Dual-energy X-ray absorptiometry (DXA) study of the spine in a patient with chronic renal failure and renal osteodystrophy. The endplates are dense (arrows) and bone density increased with T scores of up to 5.8 in L1.

SUGGESTED READING

Alston SH. Bone densitometry and bone biopsy. Best Pract Res Clin Rheumatol. 2005;19:487-501.

Briot K, Roux C. What is the role of DXA, QUS, and bone markers in fracture prediction, treatment allocation, and monitoring? Best Pract Res Clin Rheumatol. 2005;19:951-964.

Guglielmi G, Muscarella S, Bazzocchi A. Integrated imaging approach to osteoporosis: state-of-the-art review and update. Radiographics. 2011;31(5):1343-1364.

▪ OSTEOPOROSIS: REGIONAL OSTEOPOROSIS

KEY FACTS

Osteoporosis may be more localized, affecting single or multiple osseous structures or periarticular regions.
Changes are most common in the extremities.
Several disease categories are included in regional osteoporosis.
- Disuse osteoporosis: Disuse or immobilization osteoporosis is common after trauma with reduced use. Other painful conditions or paralysis may also result in disuse osteoporosis. Radiographic features include generalized osteopenia, subchondral osteopenia, or foci of cortical or medullary lucency.
- Transient regional osteoporosis: Transient regional osteoporosis has in common focal involvement, rapid onset, and pain, and conditions are self-limited. One of the most common is transient osteoporosis of the hip (see Chapter 3). Radiographic features include rapid-onset osteopenia of the femoral head and neck without acetabular involvement.
- Complex regional pain syndrome (CRPS) or reflex sympathetic dystrophy: usually follows trauma but may also follow myocardial infarction or hemiplegia. Patients with neoplasms (lung, ovary, breast, and pancreas) may also present with CRPS. Patients present with pain, swelling, and reduced motion.
- Radiographic features include swelling and prominent juxta-articular osteopenia. Radionuclide scans show increased tracer in the involved osseous structures.

FIGURE 13-5. Disuse osteoporosis. Coronal (A) and sagittal (B) reformatted computed tomography (CT) images in a patient with a healing distal tibial fracture. The lower extremity shows diffuse loss of bone mineral density related to disuse.

FIGURE 13-6. Transient osteoporosis of the hip: (A) Anteroposterior (AP) radiograph of the pelvis shows osteopenia in the left proximal femur (arrow). (B) Coronal fluid-sensitive magnetic resonance image shows diffuse abnormal signal intensity in the femoral head and neck with a joint effusion. No abnormal signal is seen in the acetabulum, although a small joint effusion is present. (C) Radionuclide bone scan shows diffuse increased scintigraphic activity in the femoral head and neck.

FIGURE 13-7. Chronic regional pain syndrome. Blood pool (A) and 3 hours delay (B) images from a radionuclide bone scan show hyperemia and increased scintigraphic activity in the left ankle, hind, and midfoot. Anteroposterior (AP) (C) radiograph shows advanced osteopenia thoughout the left foot.