Assessing hip fracture risk in type-2 diabetic patients using CT-based autonomous finite element methods

Aims Type 2 diabetes mellitus (T2DM) impairs bone strength and is a significant risk factor for hip fracture, yet currently there is no reliable tool to assess this risk. Most risk stratification methods rely on bone mineral density, which is not impaired by diabetes, rendering current tests ineffective. CT-based finite element analysis (CTFEA) calculates the mechanical response of bone to load and uses the yield strain, which is reduced in T2DM patients, to measure bone strength. The purpose of this feasibility study was to examine whether CTFEA could be used to assess the hip fracture risk for T2DM patients. Methods A retrospective cohort study was undertaken using autonomous CTFEA performed on existing abdominal or pelvic CT data comparing two groups of T2DM patients: a study group of 27 patients who had sustained a hip fracture within the year following the CT scan and a control group of 24 patients who did not have a hip fracture within one year. The main outcome of the CTFEA is a novel measure of hip bone strength termed the Hip Strength Score (HSS). Results The HSS was significantly lower in the study group (1.76 (SD 0.46)) than in the control group (2.31 (SD 0.74); p = 0.002). A multivariate model showed the odds of having a hip fracture were 17 times greater in patients who had an HSS ≤ 2.2. The CTFEA has a sensitivity of 89%, a specificity of 76%, and an area under the curve of 0.90. Conclusion This preliminary study demonstrates the feasibility of using a CTFEA-based bone strength parameter to assess hip fracture risk in a population of T2DM patients. Cite this article: Bone Joint J 2021;103-B(9):1497–1504.

Association between Anti-Psychotic Drugs Use and Hip Fractures in Patients with Dementia: A Nationwide Population-Based Study

Background: People with dementia are a high-risk group for hip fractures. Although the increased risk of hip fractures associated with antipsychotic drugs (APD) is found in older populations, little is known about the risk for people with dementia living in Asia. We aimed to investigate the association between hip fractures and the characteristics of APD use in patients with dementia. Methods: A nested case-control analysis was conducted on a nationwide cohort in Taiwan. People with diagnoses of dementia during 2003–2012 were identified. Conditional logistic regression analysis was performed, and adjusted odds ratios (aORs) were calculated with a 95% confidence interval (CI) to estimate the risk of hip fractures. Results: APD use was associated with an increased risk of hip fractures in patients with dementia; current use or combined use of first and second generations of APDs had even higher risks. Regarding the duration of APD use, a U-shape curve of hip fracture risk was noted, and the risk peaked during 0–15 days and >215 days of exposure (aOR = 1.46, 95% CI 1.37–1.57; aOR = 1.47, 95% CI 1.37–1.58; respectively). Considering the doses of APDs, the hip fracture risk was significantly increased with all four levels of the cumulative doses and average daily doses and peaked in the group with the highest average daily dose. Conclusions: The findings suggest that caution must be taken when initiating APD use in patients with dementia, even in a small dose, and mixed types of APD prescriptions should be administered with care. Furthermore, frequent evaluation of the possibility of tapering or withdrawal of the medication is necessary, as the risk does not attenuate after long-term use.

Biomechanical Computed Tomography Captures Older Men at High Risk of Hip Fracture Despite Low Fracture Risk Calculation by FRAX

Background: Biomechanical computed tomography (BCT) can be applied to hip-containing CT scans to estimate femoral bone strength using finite-element analysis and to measure DXA-equivalent femoral neck (FN) BMD. Current guidelines recommend osteoporosis pharmacotherapy initiation in men with BMD T-score ≤ -2.5 or T-score between -1.0 and -2.5 with 10-year hip fracture risk ≥ 3% by FRAX.1 Estimated femoral strength by BCT is associated with incident hip fractures in men, independent of BMD,2 and can be used in conjunction with clinical risk factors for consideration of therapy initiation per the International Society of Clinical Dosimetry.3 Aim: To determine how many men are at increased risk of fractures with fragile bone strength (≤ 3500N) despite normal-to-low BMD (T-score > -2.5) and low 10-year hip fracture risk (< 3%). Methods: 625 men age ≥ 65 with hip-containing CT scans were randomly selected for BCT analysis out of 4209 scans performed from 2017 to 2019 at a single academic hospital. Scans were excluded if an intact femur was not imaged. BCT was performed for 557 men after accounting for un-processable scans. Electronic health records were retrospectively reviewed by investigators blinded to BCT results. 10-year hip fracture risks were calculated by FRAX based on available clinical data and FN BMD T-score from BCT. Chi-squared and t-test were used to investigate differences in clinical parameters between men with and without fragile bone strength. Results: The mean age was 77 (± 7.6 years), and 69% of men were white. Out of 102 men (18.3%) who met criteria for fragile bone strength by BCT, 42 (7.5%) had low FN BMD (T-score between -1.0 and -2.5) and 2 (0.4%) had normal FN BMD (T-score ≥ -1.0). The percentage of men with fragile bone strength and discrepant BMD increased with age (5.4% in age 65–74; 8.2% in age 75–84; 13.0% in age ≥ 85). The average 10-year hip fracture risk by FRAX of men with fragile bone strength was 6.5% (± 4.0%). However, 13 out of 44 men with normal-to-low BMD had 10-year hip fracture risks < 3% despite fragile bone strength presence and did not meet recommendation for osteoporosis pharmacotherapy. Examining men with normal-to-low BMD (n=493), those with fragile bone strength tended to be older, have lower BMI, and of Hispanic ethnicity compared to those with normal-to-low bone strength (p<0.05). Conclusions: Our study showed that fragile bone strength is present in older men with normal-to-low BMD, and that inclusion of 10-year hip fracture risk by FRAX may capture some, but not all, men at increased risk of hip fractures. Skeletal fragility measured by BCT may serve as additional data to assist with clinical decision making for men with osteoporosis, though further prospective research is needed. Reference: 1. Watts et al, J Clin Endocrinol Metab. 2012 Jun;97(6):1802–22. 2. Adams et al, J Bone Miner Res 2018 Jul;33(7):1291–1301. 3. Shuhart et al, J Clin Densitom. 2019 Oct-Dec;22(4):453–471.