Prediction of lumbar vertebral body compressive strength of overweight and obese older adults using morphed subject-specific finite-element models to evaluate the effects of weight loss

Effect of exercise modality and weight loss on changes in muscle and bone quality in older adults with obesity

BACKGROUND

Little is known about the effect of exercise modality during a dietary weight loss program on muscle size and quality, as measured by computed tomography (CT). Even less is known about how CT-derived changes in muscle track with changes in volumetric bone mineral density (vBMD) and bone strength.

METHODS

Older adults (66 ± 5 years, 64 % women) were randomized to 18-months of diet-induced weight loss (WL), WL with aerobic training (WL + AT), or WL with resistance training (WL + RT). CT-derived muscle area, radio-attenuation and intermuscular fat percentage at the trunk and mid-thigh were determined at baseline (n = 55) and 18-month follow-up (n = 22-34), and changes were adjusted for sex, baseline value, and weight lost. Lumbar spine and hip vBMD and finite element-derived bone strength were also measured.

RESULTS

After adjustment for the weight lost, muscle area losses at the trunk were -7.82 cm2 [-12.30, -3.35] for WL, -7.72 cm2 [-11.36, -4.07] for WL + AT, and -5.14 cm2 [-8.65, -1.63] for WL + RT (p < 0.001 for group differences). At the mid-thigh, decreases were -6.20 cm2 [-10.39, -2.02] for WL, -7.84 cm2 [-11.19, -4.48] for WL + AT, and -0.60 cm2 [-4.14, 2.94] for WL + RT; this difference between WL + AT and WL + RT was significant in post-hoc testing (p = 0.01). Change in trunk muscle radio-attenuation was positively associated with change in lumbar bone strength (r = 0.41, p = 0.04).

CONCLUSIONS

WL + RT better preserved muscle area and improved muscle quality more consistently than WL + AT or WL alone. More research is needed to characterize the associations between muscle and bone quality in older adults undertaking weight loss interventions.

Older Women who are Overweight or Obese Have Vertebral Abnormalities, Partially Degraded TBS, and BMD that Worsen with Weight Loss

Obesity is a risk factor for chronic diseases and moderate weight loss is generally recommended. Energy restriction results in the loss of hip bone mineral density (BMD) in older adults, but there is no consistent decline at the lumbar spine (LS), possibly due to vertebral abnormalities although this may also be dependent on the amount of weight loss. In this secondary analysis of weight loss trials investigating BMD and trabecular bone score (TBS) changes over 12-18 months, 92 postmenopausal women (60.8 ± 5.8 years; body mass index 32.7 ± 4.4 kg/m²) without osteoporosis, were divided into two groups: those who lost < 5% body weight (minimal) or ≥ 5% (moderate). Hip and LS-BMD and TBS were measured at baseline, 6 and 12-18 months. Exclusion of vertebral abnormalities (VE) was used to calculate BMD at the spine (LS-BMD-VE) using standard guidelines. Women lost 2.3 ± 2.4% and 8.5 ± 4.7% weight in the minimal and moderate weight loss groups, respectively. Over one third of the women had at least one vertebral abnormality or partially degraded TBS at baseline that worsened after weight loss, increasing to over 50% in this population (p < 0.05). TBS and hip BMD decreased with weight loss (p < 0.05), but LS-BMD did not decrease significantly. However, after excluding vertebral abnormalities, the LS-BMD-VE decreased in the entire population (p < 0.01), and by 1.7 ± 4.3% in the moderate weight loss group. This study suggests that older women without osteoporosis have vertebral abnormalities that obfuscated declines in BMD with weight loss, indicating that bone at the spine is further compromised.

Protocol for a pilot randomised controlled trial of zoledronic acid to prevent bone loss following sleeve gastrectomy surgery

INTRODUCTION

Sleeve gastrectomy (SG) is an increasingly used and effective treatment for obesity; however, the rapid weight loss associated with SG adversely affects bone metabolism predisposing patients to skeletal fragility. Bisphosphonate medications have been evaluated for safety and efficacy in combating bone loss in patients with osteoporosis, but their use in SG-induced bone loss is limited. The goal of this study is to investigate how a one-time infusion of zoledronic acid compares to placebo, in its ability to combat SG-associated bone loss.

METHODS AND ANALYSIS

This research protocol is a 9-month, pilot randomized controlled trial (RCT) involving 30 adult SG patients randomised to receive an infusion of either 5 mg of zoledronic acid or placebo, 6 weeks following surgery. To be included participants must be <350 lbs/158.8 kg, free of bone-impacting pathologies or medications, and must have adequate serum calcium and vitamin D levels at baseline. The primary outcome is change in areal bone mineral density (aBMD) at the total hip. Secondary outcomes include change in aBMD of the femoral neck, and lumbar spine, and change in volumetric BMD at the lumbar spine. The primary aim will be tested using a linear mixed model fit with total hip aBMD at 9 months as the outcome. Treatment, participant sex and menopausal status will be considered in analysis. Groups will be compared using contrast statements at 9 months, with change over 9 months being the primary comparison.

ETHICS AND DISSEMINATION

This study was approved by the Institutional Review Board of the University of Nebraska Medical Center (IRB820-19). Written consent will be obtained from participants at enrolment by trained staff. Careful and thorough explanation are used in obtainment of consent and voluntariness is emphasised throughout the trial. The findings of this study will be presented locally, nationally, and published in peer-reviewed journals. Additional details will be reported on ClinicalTrials.gov.

TRIAL REGISTRATION NUMBER

NCT04279392.

Effect of Model Parameters on the Biomechanical Behavior of the Finite Element Cervical Spine Model

Finite element (FE) models have frequently been used to analyze spine biomechanics. Material parameters assigned to FE spine models are generally uncertain, and their effect on the characterization of the spinal components is not clear. In this study, we aimed to analyze the effect of model parameters on the range of motion, stress, and strain responses of a FE cervical spine model. To do so, we created a computed tomography-based FE model that consisted of C2-C3 vertebrae, intervertebral disc, facet joints, and ligaments. A total of 32 FE analyses were carried out for two different elastic modulus equations and four different bone layer numbers under four different loading conditions. We evaluated the effects of elastic modulus equations and layer number on the biomechanical behavior of the FE spine model by taking the range of angular motion, stress, and strain responses into account. We found that the angular motions of the one- and two-layer models had a greater variation than those in the models with four and eight layers. The angular motions obtained for the four- and eight-layer models were almost the same, indicating that the use of a four-layer model would be sufficient to achieve a stress value converging to a certain level as the number of layers increases. We also observed that the equation proposed by Gupta and Dan (2004) agreed well with the experimental angular motion data. The outcomes of this study are expected to contribute to the determination of the model parameters used in FE spine models.

Opportunistic Screening for Osteoporosis Using Computed Tomography: State of the Art and Argument for Paradigm Shift

PURPOSE OF REVIEW

Osteoporosis is disproportionately common in rheumatology patients. For the past three decades, the diagnosis of osteoporosis has benefited from well-established practice guidelines that emphasized the use of dual x-ray absorptiometry (DXA). Despite these guidelines and the wide availability of DXA, approximately two thirds of eligible patients do not undergo testing. One strategy to improve osteoporosis testing is to employ computed tomography (CT) examinations obtained as part of routine patient care to "opportunistically" screen for osteoporosis, without additional cost or radiation exposure to patients. This review examines the role of opportunistic CT in the evaluation of osteoporosis.

RECENT FINDINGS

Recent evidence suggests that opportunistic measurement of bone attenuation (radiodensity) using CT has sensitivity comparable to DXA. More importantly, such an approach has been shown to predict osteoporotic fractures. The paradigm shift of using CTs obtained for other reasons to opportunistically screen for osteoporosis promises to substantially improve patient care.