Findings: Image #1 is a single view of the left forearm demonstrating plate and screw fixation of a transverse fracture through the ulna and radius.

Image #2 and 3 are images of the left hand demonstrating marked periarticular osteoporosis.

Diagnosis: Disuse osteoporosis.

Discussion: Disuse osteoporosis is a form of osteoporosis which occurs characteristically in patients with immobilized limbs secondary to fracture or paralysis. The appearance of significant osteoporosis generally occurs after approximately 8 weeks of immobilization, although it may occur somewhat sooner in younger patients. The roentgenographic findings include patchy osteoporosis (most commonly in a periarticular distribution). In addition, there may be a more disuse pattern of osteoporosis in the region of immobilization. The pathogenesis of diffuse osteoporosis is not entirely clear but may represent a reduction in new bone formation versus increased bone resorption. Therefore, disuse osteoporosis is generally considered a high turnover osteoporosis which is self limited and generally reversible. In addition to the periarticular osteoporosis of immobilization, intra-articular complications of disuse may develop. Restricted motion may result in pericapsular contractions, erosion, atrophy, and subchondral bone abnormality such as cysts. Disuse osteoporosis can be confused with aggressive permeative process such as infection or metastatic disease. Recognition of the regional distribution - involvement of multiple bones centered around a joint - is key.

Reference:
Resnick D. Diagnosis of Bone and Joint Disorders, 2nd Edition. W. B. Saunders.
Philadelphia 1988;2034-2037.

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