Tag Archive | DXA

T-Scores for Diagnosing Osteoporosis: 3 Are Better Than 1

This post comes from Fred Nelson, MD, an orthopaedic surgeon in the Department of Orthopedics at Henry Ford Hospital and a clinical associate professor at Wayne State Medical School. Some of Dr. Nelson’s tips go out weekly to more than 3,000 members of the Orthopaedic Research Society (ORS), and all are distributed to more than 30 orthopaedic residency programs. Those not sent to the ORS are periodically reposted in OrthoBuzz with the permission of Dr. Nelson.

The World Health Organization (WHO) and the International Society for Clinical Densitometry (ISCD) define osteoporosis based on (DXA) measures of bone mineral density that are translated into T-scores. A T-score ≤ -2.5 at any 1 of the 3 commonly measured sites (lumbar vertebrae, femoral neck, and total hip) is considered diagnostic for osteoporosis, and a T-score between -2.5 and -1 is indicative of osteopenia. University of Pennsylvania investigators1 proposed that combining all 3 T-scores in a multivariate analysis would be “potentially more informative” than the common practice of using the single lowest T-score.

The investigators applied multivariate statistical theory to T-scores from a sample of 1,000 65-year-old white women. When both real data and simulation models were analyzed, the researchers found that more patients were diagnosed with osteoporosis using the multivariate version of the WHO/ISCD guidelines than with the current WHO/ISCD guidelines. The diagnoses of osteoporosis using this method were also associated with higher Fracture Risk Assessment Tool (FRAX) probabilities of major osteoporotic fractures (P=0.001) and hip fractures (P=2.2×10−6). The FRAX tool combines a patient’s history of fracture with age, sex, race, height, weight, and social habits such as smoking and drinking to determine the risk of a major facture in the next 10 years.

This study shows that statistically considering all 3 T-scores may reveal more cases of osteoporosis than using the single lowest T-score. The trick will be getting this insight into the hands—and minds—of those making radiologic interpretations of DXA findings.

Reference 

  1. Sebro R, Ashok S. A Statistical Approach regarding the Diagnosis of Osteoporosis and Osteopenia from DXA: Are we underdiagnosing osteoporosis? J. Bone Mineral Res Plus. In press

More Pre-op Bone Health Evaluations Needed

“We believe that bone health screening should be considered in all orthopaedic surgical candidates who are ≥50 years of age.” So proclaim Kadri et al., based on results of their study of 124 patients who were referred by orthopaedic surgeons for preoperative bone health optimization. The study appeared in the April 1, 2020 issue of The Journal of Bone & Joint Surgery.

The importance of identifying poor bone health before reconstructive orthopaedic surgery is well known but poorly implemented. The bone health evaluation in this cohort consisted of a physical examination, structured history-taking focused on prior fracture, and collection of Fracture Risk Assessment Tool (FRAX) data. Most (122 patients) also underwent dual X-ray absorptiometry (DXA), and more than two-thirds were evaluated with a trabecular bone score. Incidental CT scans were available for and evaluated in 43 patients. Based on these data, Kadri et al. found the following:

  • >90% of the cohort met National Osteoporosis Foundation criteria for osteoporosis treatment.
  • A high FRAX risk (major osteoporotic fracture ≥20% or hip ≥3%) was present in 82% of the patients.
  • Osteoporosis, as defined by T scores of ≤─2.5 points, was present in 45% of the women and 20% of the men.
  • Trabecular bone scores identified 34% of patients as having degraded bone microarchitecture.

As a result of these findings, 75% of the cohort were prescribed treatment for osteoporosis; 45% were prescribed anabolic agents and 30% were prescribed antiresorptive therapy.

For patients with clinical risk factors for osteoporosis and high FRAX risk, Kadri et al. recommend bone health optimization strategies for a minimum of 3 months prior to any planned orthopaedic surgery. “It has been our experience that patients are generally satisfied and are grateful to undergo bone health optimization despite a delay in the surgical procedure,” they write.

Although postsurgical outcomes among these patients were not analyzed, the authors intuitively point out that bone health optimization probably reduces the likelihood of postoperative complications and revisions and therefore would lead to improved outcomes and lower costs. Preoperative bone health optimization could also help surgeons select the most effective surgical technique and/or implant, they say.