DXA and anthropometric measures were collected using an adaptation of the protocol described by Ng et al. (26 (link)). In the current study, each participant underwent 2 whole-body DXA scans with repositioning on either a Hologic Horizon/A system at UCSF or a Hologic Discovery/A system at PBRC and at UHCC (Hologic Inc.). Results of the 2 whole-body DXA scans were averaged. Participants were scanned according to the manufacturer's guidelines. All DXA scans were centrally analyzed at UHCC by a single certified technologist using Hologic Apex 5.5 software. Output from DXA included regional and whole-body percentage fat mass, lean soft tissue mass, and mean VAT and SAT for L1–L5. DXA cross-calibration phantoms were circulated between all sites, and calibration equations were derived to remove systematic bias in all bone and soft tissue results.
Discovery a system
Manufactured by Hologic
Sourced in United States
The Discovery A System is a laboratory equipment designed for automated sample processing and analysis. It is capable of performing various diagnostic tests and assays within a controlled laboratory environment.
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19 protocols using discovery a system
1
Dual-Energy X-Ray Absorptiometry and Anthropometry
2
Comprehensive Anthropometric Assessments
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Research staff measured height, weight, waist circumference, and hip circumference for each LOS participant. Height and weight were measured using a Health-O-Meter Professional height and weight scale, in centimeters and kilograms, respectively. Waist and hip circumferences were measured at maximal circumferences in centimeters. Whole body composition, including lean mass in both arms and legs, was measured using a DXA machine (Hologic Discovery A system, Hologic Inc., Bedford, MA, USA). Subjects self-reported as African-American/Black, Asian, Caucasian/White, and Hispanic/Latino. Participants who didn’t fit one of these categories were designated “other” for ethnicity. Personal annual income and education were optionally self-reported with categorized selections in the LOS medical questionnaire.
3
Evaluating Porcine Lumbar Spine BMD and TBS
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Porcine lumbar spines were evaluated with a Hologic Discovery A system (Hologic Inc, Marlborough, Massachusetts, USA) installed at the Bone Metabolic Unit of the Nuclear Medicine of the Fondazione IRCCS Ca' Granda-Ospedale Maggiore Policlinico, Milan, Italy. To assess BMD, we used APEX software installed on the same machine, whereas TBS has been calculated automatically by software provided by Medimaps Group, Wilmington, US, and installed on the same machine. DXA image resolution was set to 0.5 mm, and each spine was placed in accordance to the correct anatomical planes. For each spine, after manually removing the residual ribs left from the butcher, we performed a lumbar scan, manually selecting the region of interest, to calculate TBS for each vertebra. We performed the DXA scanning of each full spine, after removal from the animal, before the sample preparation, to make sure that the clinical parameters of the porcine spines were similar to those of adult human vertebrae, according to the International Society of Clinical Densitometry (https://www.iscd.org/ (April 2016)) and to the National Health and Nutrition Examination Survey (NHANES) [59 (link)]. Being the segmentation method in DXA scanning a manual procedure, we tested each vertebra three times to calculate the segmentation effect on our results.
4
Comprehensive Anthropometric Assessments
5
Whole-Body DXA Scanning for Body Composition
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Whole-body DXA scan was performed once on a Hologic Discovery/A system (Hologic Inc.). Per manufacturer protocol, participants were centered on the scan table with arms at their sides, hands pronated, and feet in a plantar flexed position [39 (link)]. Full scans took ∼3 min and provided total body mass, total and regional (trunk, arms, and legs) FM, bone mineral content, and FFM. DXA cross-calibration phantoms were circulated between all sites, and calibration equations were derived to remove systematic bias in all bone and soft tissue results. DXA scans were analyzed centrally at the University of Hawaii Cancer Center by a trained technologist using Hologic Apex version 5.6 with the NHANES Body Composition Analysis calibration option disabled. Body composition was estimated as follows: fat mass index (FMI) and FFMI were calculated by dividing FM and FFM by height squared. Percent body fat (PBF) by 3DO was FM/scale weight. ALM by both methods was calculated as (arm + leg FFM) ∗ 2. ALMI was calculated as ALM/(height squared) or ALM/BMI where indicated.
6
BMD and Trabecular Bone Score Evaluation
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We collected bone mineral density (BMD) data by reviewing the patients' medical records. The BMD at the lumbar spine (LS; L2–L4), femoral neck (FN), and total hip (TH) were obtained by dual-energy X-ray absorptiometry using the Discovery A system (Hologic, Waltham, MA, US) based on the Osteoporosis Diagnostic Criteria of the Japanese Society for Bone and Mineral Research.30 (link) The coefficients of variation (CV) were 0.93% (LS), 1.74% (FN), and 1.31% (TH), respectively. The trabecular bone score (TBS) was retrospectively analyzed in a blinded manner from the BMD at the LS using TBS iNsight software (version 3.0.3.0, Medimaps, France), as previously described,31 with a CV of 1.12%. A detailed description of the evaluation of bone status is available in the Supplementary methods .
7
Biomechanical Evaluation of Proximal Arm Fixation
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Ten matched pairs of fresh-frozen cadaveric proximal arms (n = 20; 7 male, 3 female, age = 56.5 ± 6.7 years old) were procured and stored at –20°C. Bone mineral density (BMD) of each specimen was measured at the surgical neck via dual-energy X-ray absorptiometry (Discovery-A System; Hologic Mississauga, Ontario, Canada). Specimens were thawed 12 hours before being dissected free of all soft tissue except for the pectoralis tendon. The biceps tendon was freed completely from the bicipital groove and wrapped in normal saline solution-soaked gauze and refrigerated prior to fixation. The bones were transected 14 cm proximal to the elbow joint. Specimens were then marked 50 mm below the palpable distal entrance of the bicipital groove, approximately at the midpoint of the pectoralis major insertion, to mark the device insertion point. This study was conducted following approval by the Walter Reed National Military Medical Center Institutional Review Board under protocol number WRNMMC-EDO-2020-0453 “Biomechanical Comparison of Fixation Techniques in the Upper Extremity.”
8
Standardized Whole-Body DXA Scans
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All DXA scans were acquired on Hologic (Hologic Inc., MA, USA) scanners of similar models. The Health ABC whole-body scans utilized were collected using Hologic QDR 4500 systems and attempts were made to collect DXA scans on eight occasions throughout the study. Hologic QDR4500, Delphi, and Discovery models were used to acquire whole-body DXA scans for the BMDCS and scans were acquired yearly for 6 years. Participants of the Shape Up! Adults study received whole-body DXA scans with a Hologic Discovery/A system. Some participants also received duplicate precision scans within the same visit. To estimate test–retest precision, Shape Up participants were scanned twice with repositioning between the scans. Height and weight measures were available for all participants. Manufacturer-defined acquisition protocols were used to ensure reproducibility and standardization of patient positioning37 (link),38 (link). For each participant, the raw dual-energy attenuation images with their respective calibration images were represented at a bit depth of 16-bit.
9
Detailed Body Composition Measurement
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All participants had their height measured using the same portable stadiometer (Seca version 216, Seca, Chino, CA, USA) with precision 0.1 cm and body weight with the same electronic scale (Seca Clara 803, Seca, Chino, CA, USA) with a precision of 0.1 kg, with the participant barefoot and in minimum clothing. BMI was calculated by dividing the individual's weight by height squared (kg/m2).
Body composition assessment was done using the Discovery A System (Hologic, Waltham, MA, USA), in accordance with published guidelines by the International Society for Clinical Densitometry [27 (link)]. Participants were placed centered on the scanning field in a supine position, with palms down and arms at sides, slightly separated from the trunk. Regions of interest (ROIs) were defined by the analytical program and included total body, trunk, head, pelvis, upper limbs, and lower limbs. For each region, DXA scanned weight of total, fat, and lean body mass. For the actual study, three lean mass measures were used: appendicular lean mass (ALM), calculated by the addition of the four limbs lean mass; ALM index (ALMI), computed as the ratio of ALM over height squared; and ALM divided by body mass index (ALM/BMI).
Body composition assessment was done using the Discovery A System (Hologic, Waltham, MA, USA), in accordance with published guidelines by the International Society for Clinical Densitometry [27 (link)]. Participants were placed centered on the scanning field in a supine position, with palms down and arms at sides, slightly separated from the trunk. Regions of interest (ROIs) were defined by the analytical program and included total body, trunk, head, pelvis, upper limbs, and lower limbs. For each region, DXA scanned weight of total, fat, and lean body mass. For the actual study, three lean mass measures were used: appendicular lean mass (ALM), calculated by the addition of the four limbs lean mass; ALM index (ALMI), computed as the ratio of ALM over height squared; and ALM divided by body mass index (ALM/BMI).
10
Anthropometry and Hip DXA Measurements
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Weight, height, and body mass index (BMI) were measured by the study nurse during the baseline visit. Femoral neck BMD and total hip BMD were assessed from the hip DXA scans performed using Discovery A System (Hologic, 123 Waltham, MA, USA) at the baseline visit.
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