Clinical risk factor status in patients with vertebral fracture but normal bone mineral density

Normal bone mineral density (BMD) as measured by dual-energy x-ray absorptiometry (DXA) is present in approximately 10% of older adults with fracture. BMD alone does not evaluate bone quality or clinical risk factors, and therefore, may not adequately capture a patient's fracture risk. Thus, despite a normal DXA-measured BMD, the underlying bone may be abnormal, suggesting that further bone health evaluation, and potentially, pharmacologic treatment may be warranted.

To determine the prevalence of normal BMD, clinical fracture risk factors, and quantitative risk of fracture using the Fracture Risk Assessment Tool (FRAX) in vertebral fracture patients with normal BMD enrolled in the Own the Bone registry, thus facilitating identification of those who meet criteria for anti-osteoporosis therapy.

Retrospective, national registry-based cohort.

From July 2016 to July 2021, 1,807 patients age ≥50 who sustained a vertebral fracture and had DXA data available from within 2 years prior to enrollment in the American Orthopaedic Association's Own the Bone (AOA OTB) registry were included.

World Health Organization (WHO) DXA T-score based bone classification criteria; FRAX risk scores of major osteoporotic fracture or hip fracture.

Demographic data, prior fracture site, and clinical fracture risk factors were collected. BMD status was classified by the WHO T-score criteria: ≥ -1.0 normal, -1.1 to -2.4 osteopenia, and ≤ -2.5 osteoporosis, with low bone mass including either osteopenia or osteoporosis. In normal BMD patients, FRAX scores were calculated with and without BMD, with the treatment threshold defined as a major osteoporotic fracture risk ≥20% or hip fracture risk ≥3%.

Mean±SD age was 72.0±9.7, 78.1% were female, and 92.4% were Caucasian. Normal BMD was present in 7.9%. Clinical fracture risk factors including alcohol use ≥3 units/day and history of ≥2 falls in the year prior to enrollment were more common in normal BMD (11.2% and 28%, respectively) compared to low bone mass patients (3.4% and 25.2%, respectively). A prior vertebral fracture had occurred in 49.5% with normal BMD compared to 45.8% with low bone mass, while a prior non-major osteoporotic fracture occurred in 28.9% and 29.3% of normal BMD and low bone mass patients, respectively. In normal BMD patients, either a prior fracture or FRAX risk with BMD meeting treatment thresholds was present in 85%.

Clear indications for receipt of pharmacologic therapy, ie, prior fracture or elevated fracture risk, were present in most patients with vertebral fracture and normal BMD enrolled in the AOA OTB. Prior non-major osteoporotic fractures were common and may be useful indicators of underlying bone disease. Surgeons must recognize that other important risk factors apart from BMD may indicate poor bone health, and thus, help guide further bone health evaluation.