Computed tomography assessment of pelvic bone density: Associations with age and pelvic fracture in motor vehicle crashes.

Motor vehicle crash (MVC) occupants routinely get a computed tomography (CT) scan to screen for internal injury, and this CT can be leveraged to opportunistically derive bone mineral density (BMD). This study aimed to develop and validate a method to measure pelvic BMD in CT scans without a phantom, and examine associations of pelvic BMD with age and pelvic fracture incidence in seriously injured MVC occupants from the Crash Injury Research and Engineering Network (CIREN) study. A phantom-less muscle-fat calibration technique to measure pelvic BMD was validated using 45 quantitative CT scans with a bone calibration phantom. The technique was then used to measure pelvic BMD from CT scans of 252 CIREN occupants (ages 16+) in frontal MVCs who had sustained either abdominal or pelvic injury. Pelvic BMD was analyzed in relation to age and pelvic fracture incidence. In the validation set, phantom-based calibration vs. phantom-less muscle-fat calibration yielded similar BMD values at the anterior superior iliac spine (ASIS; R2 = 0.95, p < 0.001) and iliac crest (R2 = 0.90, p < 0.001). Pelvic BMD was measured in 150 female and 102 male CIREN occupants aged 16-89, and 25% of these occupants sustained pelvic fracture. BMD at the ASIS and iliac crest declined with age (p < 0.001). For instance, iliac crest BMD decreased an average of 25 mg/cm3 per decade of age. The rate of iliac crest BMD decline was 7.6 mg/cm3 more per decade of age in occupants with pelvic fracture compared to those not sustaining pelvic fracture. Findings suggest pelvic BMD may be a contributing risk factor for pelvic fracture in MVCs.

Assessment of finite element human body and ATD models in estimating injury risk in far-side impacts using field-based injury risk.

The objective of this study was to assess the ability of finite element human body models (FEHBMs) and Anthropometric Test Device (ATD) models to estimate occupant injury risk by comparing it with field-based injury risk in far-side impacts. The study used the Global Human Body Models Consortium midsize male (M50-OS+B) and small female (F05-OS+B) simplified occupant models with a modular detailed brain, and the ES-2Re and SID-IIs ATD models in the simulated far-side crashes. A design of experiments (DOE) with a total of 252 simulations was conducted by varying lateral ΔV (10-50kph; 5kph increments), the principal direction of force (PDOF 50°, 60°, 65°, 70°, 75°, 80°, 90°), and occupant models. Models were gravity-settled and belted into a simplified vehicle model (SVM) modified for far-side impact simulations. Acceleration pulses and vehicle intrusion profiles used for the DOE were generated by impacting a 2012 Camry vehicle model with a mobile deformable barrier model across the 7 PDOFs and 9 lateral ΔV's in the DOE for a total of 63 additional simulations. Injury risks were estimated for the head, chest, lower extremity, pelvis (AIS 2+; AIS 3+), and abdomen (AIS 3+) using logistic regression models. Combined AIS 3+ injury risk for each occupant was calculated using AIS 3+ injury risk estimations for the head, chest, abdomen, and lower extremities. The injury risk calculated using computational models was compared with field-based injury risk derived from NASS-CDS by calculating their correlation coefficient. The field-based injury risk was calculated using risk curves that were created based on real-world crash data in a previous study (Hostetler et al., 2020). Occupant age (40 years), seatbelt use (belted occupant), collision deformation classification, lateral ΔV, and PDOF of the crash event were used in these curves to estimate field injury risk. Large differences in the kinematics were observed between HBM and ATD models. ATD models tended to overestimate risk in almost every case whereas HBMs yielded better risk estimates overall. Chest and lower extremity risks were the least correlated with field injury risk estimates. The overall risk of AIS 3+ injury risk was the strongest comparison to the field data-based risk curves. The HBMs were still not able to capture all the variance but future studies can be carried out that are focused on investigating their shortfalls and improving them to estimate injury risk closer to field injury risk in far-side crashes.

Application of the D3 -creatine muscle mass assessment tool to a geriatric weight loss trial: A pilot study.

BACKGROUND: Traditionally, weight loss (WL) trials utilize dual energy X-ray absorptiometry (DXA) to measure lean mass. This method assumes lean mass, as the sum of all non-bone and non-fat tissue, is a reasonable proxy for muscle mass. In contrast, the D3 -creatine (D3 Cr) dilution method directly measures whole body skeletal muscle mass, although this method has yet to be applied in the context of a geriatric WL trial. The purpose of this project was to (1) describe estimates of change and variability in D3 Cr muscle mass in older adults participating in an intentional WL intervention and (2) relate its change to other measures of body composition as well as muscle function and strength. METHODS: The INVEST in Bone Health trial (NCT04076618), used as a scaffold for this ancillary pilot project, is a three-armed, 12-month randomized, controlled trial designed to determine the effects of resistance training or weighted vest use during intentional WL on a battery of musculoskeletal health outcomes among 150 older adults living with obesity. A convenience sample of 24 participants (n = 8/arm) are included in this analysis. At baseline and 6 months, participants were weighed, ingested a 30 mg D3 Cr tracer dose, provided a fasted urine sample 3-6 days post-dosage, underwent DXA (total body fat and lean masses, appendicular lean mass) and computed tomography (mid-thigh and trunk muscle/intermuscular fat areas) scans, and performed 400-m walk, stair climb, knee extensor strength, and grip strength tests. RESULTS: Participants were older (68.0 ± 4.4 years), mostly White (75.0%), predominantly female (66.7%), and living with obesity (body mass index: 33.8 ± 2.7 kg/m2 ). Six month total body WL was -10.3 (95% confidence interval, CI: -12.7, -7.9) kg. All DXA and computed tomography-derived body composition measures were significantly decreased from baseline, yet D3 Cr muscle mass did not change [+0.5 (95% CI: -2.0, 3.0) kg]. Of muscle function and strength measures, only grip strength significantly changed [+2.5 (95% CI: 1.0, 4.0) kg] from baseline. CONCLUSIONS: Among 24 older adults, significant WL with or without weighted vest use or resistance training over a 6-month period was associated with significant declines in all bioimaging metrics, while D3 Cr muscle mass and muscle function and strength were preserved. Treatment assignment for the trial remains blinded; therefore, full interpretation of these findings is limited. Future work in this area will assess change in D3 Cr muscle mass by parent trial treatment group assignment in all study participants.