Using CT Data to Diagnose Osteoporosis
Osteoporosis is a “silent” disease, often becoming apparent only after a patient older than 50 sustains a low-energy fracture of the wrist, proximal humerus, or hip. Monitoring serum vitamin D levels and DEXA testing represent ideal screening methods to prevent these sentinel fragility fractures. In addition, through programs such as the AOA’s “Own the Bone” initiative, the orthopaedic community has taken a leadership role in diagnosing and treating osteoporosis after the disease presents as a fragility fracture. Own the Bone is active in all 50 states and, through local physician leadership, is identifying individuals who present with a fragility fracture so they can receive follow-up care that helps mitigate bone loss and prevent secondary fractures.
We still have a long way to go, however. Recent analyses show that only 30% of candidate patients (albeit up from 20%) are receiving this type of evidence-based care. The best-case scenario would be to identify at-risk men and women (osteoporosis does not affect women exclusively) before a potentially serious injury.
In the December 5, 2018 issue of The Journal, Anderson et al. present strong evidence that computed tomography (CT) can provide accurate data for diagnosing osteoporosis. CT is increasingly used (perhaps overused in some settings) across a spectrum of diagnostic investigations. The osseous-related data from these scans can be used to glean accurate information regarding a patient’s bone quality by analyzing the Hounsfield unit (HU) values of bone captured opportunistically by CT. HU data are routinely ignored, but the values correlate strongly with bone mineral density, and they could help us recommend preventive care to our patients before a fragility fracture occurs. (For example, a threshold of <135 HU for the L1 vertebral body indicates a risk for osteoporosis.)
Orthopaedists should discuss the possibility of asking their radiologist colleagues who read CT scans of older patients to routinely share that data. When indicated, we could promptly refer patients back to their primary care provider for discussion of pharmacological treatment and lifestyle changes proven to help prevent primary fragility fractures. There is little doubt that our patients are getting older. Reviewing CT data could help us dramatically improve preventive care and decrease the risk of first-time fragility fractures.
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Marc Swiontkowski, MD