What can cause a markedly elevated DEXA scan result in an elderly patient?

Causes of Significantly Elevated DEXA Scan Readings in Elderly Patients

In elderly patients, markedly elevated DEXA scan results are most commonly caused by degenerative spine osteoarthritis, which affects approximately 85% of those over age 75, followed by vertebral fractures, aortic calcifications, and various implanted devices or surgical hardware. 1

Primary Causes of Falsely Elevated BMD

Degenerative Spine Changes (Most Common)

Spine osteoarthritis is the leading cause of spuriously elevated DEXA readings in the elderly. The condition causes osteophytes, facet joint hypertrophy, and sclerosis that artificially increase bone mineral density measurements 1. This is particularly problematic because:

• 40% of women aged 55 have spine osteoarthritis
• 85% of those over age 75 are affected 1
• Any vertebra differing by more than 1.0 T-score from adjacent vertebrae should be excluded from analysis 1

Vertebral Fractures

Paradoxically, fractured vertebrae demonstrate increased BMD values due to trabecular impaction and condensation, with a mean BMD increase of 0.070 g/cm² 1. These fractures:

• Typically occur at T12-L2 region
• Show reduced height and low area values on imaging
• Display linearly increased sclerosis
• Require confirmation with plain radiographs, CT, or MRI when uncertain 1

Vascular Calcifications

Aortic calcifications overlying the spine are extremely common in elderly patients and spuriously elevate lumbar spine BMD readings 1.

Implanted Devices and Hardware

The past 30 years have seen substantial increases in various implants that falsely elevate BMD 2:

• Surgical hardware (metal clips, wires, spine fusion material, scoliosis rods)
• Implantable devices (pain pumps, neurostimulators)
• Vascular grafts and stents
• Osteosynthesis materials
• Hip prostheses or screws 1

Other Pathological Causes

Additional conditions causing elevated readings include:

• Diffuse idiopathic skeletal hyperostosis (DISH) 1
• Ankylosing spondylitis 1
• Bone metastases 1
• Paget's disease 1
• Splenomegaly from glycogen storage disease 1

Extraneous Artifacts

• Radio-opaque contrast material from recent GI/GU studies
• Undissolved calcium tablets (though these typically cause <2.2% increase in L1-4 BMD, they can cause up to 12.6% increase in single vertebral BMD) 3
• Thick or reflecting clothing materials 1

Critical Clinical Approach

When encountering unexpectedly high DEXA readings in elderly patients:

1. Review the actual DEXA images - don't rely solely on the numerical report
2. Look for T-score differences ≥1.0 between adjacent vertebrae - this signals artifact 1
3. Exclude affected vertebrae from analysis when structural changes are present 1
4. Obtain additional imaging (plain radiographs, CT, or MRI) when diagnosis is uncertain 1
5. Consider using hip BMD instead - hip measurements are far less susceptible to degenerative artifacts than spine 1
6. Consult with a musculoskeletal radiologist when interpretation remains unclear 2

Common Pitfalls to Avoid

• Do not accept spine BMD at face value in elderly patients - the lumbar spine is the site most frequently affected by artifacts that spuriously increase BMD 1
• Do not assume high BMD means no osteoporosis - degenerative changes can mask underlying bone loss
• Do not use hip measurements if prostheses or hardware are present - use the contralateral side instead 1
• Incorrect vertebral counting can lead to misinterpretation 1

The key principle: artifacts in the lumbar spine almost always cause spurious increases in BMD values, while spurious decreases are uncommon 1. This means unexpectedly high readings should trigger careful image review rather than reassurance about bone health.