This registry-based cohort study assessed the percentage of women with prior or incident fracture who had normal bone defined as a normal bone mineral density T-score and normal trabecular bone score (TBS). Inclusion of TBS reduced the percentage with normal bone. Normal bone measurement is rare in women with fracture.
Some fractures occur in women with normal BMD. We hypothesized that adding trabecular bone score (TBS) to DXA would (1) demonstrate that few women with fracture have normal bone, i.e., normal BMD T-score and TBS and (2) increase the percentage of women with fracture that have abnormal bone defined as a BMD T-score ≤ - 2.5 or low TBS.
The public healthcare system in Manitoba, Canada, makes it possible to link clinical DXA data to population databases. This study included all women age 50+ with a first DXA from February 1999 to March 2018 with valid BMD, TBS, and fracture data. Bone status was defined as Normal = BMD T-score of the spine, femoral neck, and total femur ≥ - 1.0 AND TBS > 1.31; Abnormal = BMD T-score ≤ - 2.5 OR TBS < 1.23; and borderline = all others. Analyses were stratified by age decade.
Among women with prior (n = 4649) or incident (n = 2547) fracture, bone status assessed by both BMD and TBS was normal in only 6% and 4%, respectively. In women with prior or incident hip fracture, normal bone was present in < 1%. The prevalence of normal bone declined (p trend < 0.001) with age as expected. BMD T-score osteoporosis was present in 40% with any prior and 46% with any incident fracture. BMD T-score osteoporosis was present in 65% and 60% with prior and incident hip fracture, respectively. Including TBS with BMD increased the percentage of women with abnormal bone to 61% and 68% for any prior or incident fracture and to 80% and 81% for prior or incident hip fracture, respectively (all p < 0.001).
Including TBS with BMD increases identification of abnormal bone in women with fracture compared with BMD alone. Normal bone is present in < 6% of women with any fracture and < 1% of those with hip fracture. What is thought to be normal bone in women with fracture is rarely normal.