Muscle density discriminates hip fracture better than computed tomography X-ray absorptiometry hip areal bone mineral density

Postoperative Gait Performance Following Pertrochanteric Fractures Is Influenced by the Preoperative Condition of the Gluteal Muscles

Introduction Amid an increasing number of patients with pertrochanteric fractures, early prediction of postoperative gait potential could reduce unnecessary rehabilitation and hospitalization. The relationship between preoperative gluteal muscle condition and postoperative gait outcomes remains unclear. The gluteal muscles are crucial for mobility, and their cross-sectional area (CSA) and fatty infiltration are indicators of physical function. Preoperative computed tomography (CT) provides quantitative data on muscle CSA and density, measured in Hounsfield Units (HU). This study aimed to identify which preoperative muscle index, CSA, BMI-adjusted CSA, or muscle density, best predicts postoperative gait ability. We hypothesized that a higher adjusted CSA and muscle density in the gluteus muscles would be associated with superior gait performance. Materials and methods Preoperative assessments included radiographs and CT scans. Patients under 75, with less than four weeks of follow-up, prior contralateral hip surgery, prefracture immobility, male patients, high-energy trauma, or conditions impairing physical performance were excluded. Gait performance was evaluated four weeks postoperatively, classifying patients into two groups: the 'parallel bar group,' requiring parallel bars, and the 'walker group,' walking independently. Patients underwent CM nailing. Preoperative CT scans measured the CSA and muscle density of the gluteus maximus and medius. Measurements were taken from the non-injured side to avoid interference from the fracture. Muscle borders were manually traced, and the CSA and muscle density in HU were calculated. Results Out of 81 patients, 49 met the inclusion criteria (mean age: 87). The patients were divided into the 'parallel bar group' (n=19) and the 'walker group' (n=30) based on postoperative gait performance. No significant differences in age, weight, height, or fracture laterality were observed between groups. The mean (and standard deviation (SD)) of CSA for the gluteus maximus in the 'parallel bar group'/in the 'walker group' was 2211.8 ± 469.8 mm²/2440.0 ± 586.2 mm², respectively (p=0.15), and for the gluteus medius, it was 1751.7 ± 415.2mm²/1869.1 ± 448.3mm², respectively (p=0.36). The mean (and SD) muscle density for the gluteus maximus in the 'parallel bar group'/in the 'walker group' was 13.6 ± 12.7 HU / 20.6 ± 13.0 HU (p=0.07), and for the gluteus medius, it was 25.2 ± 8.4 HU/31.8 ± 10.1 HU, respectively (p=0.02). The ROC curve identified a 30.9 HU cut-off for gluteus medius density, with sensitivity and specificity of 60.7% and 78.9%. The mean (and SD) of BMI-adjusted CSA for the gluteus maximus in the 'parallel bar group'/ in the 'walker group' was 116.4 ± 26.8 m²/106 kg/124.3 ± 29.2 m²/106 kg, respectively (p=0.35), and for the gluteus medius, it was 93.3 ± 27.2 m²/106 kg/95.4 ± 21.3m²/106kg, respectively (p=0.78). Conclusion This study analyzed preoperative CT images of women aged 75 and older with pertrochanteric fractures, comparing gluteal muscle CSA and density with postoperative walking ability. The gluteus medius density was significantly higher in the superior gait group, with a cut-off value of 30.9 HU. However, no significant differences were found in the gluteus maximus density, CSA, or BMI-adjusted CSA. These findings partially support the hypothesis, emphasizing the importance of muscle evaluation in predicting postoperative gait performance.

Association between Deltoid Muscle Density and Proximal Humeral Fracture in Elderly Patients

Background

The potential role of deltoid muscle density in the occurrence of proximal humeral fractures remains uncertain. Therefore, the primary objective of this study was to examine the correlation between deltoid muscle density, as measured by CT attenuation value in Hounsfield units (HU), and the incidence of proximal humeral fractures in elderly patients. By investigating this association, we aim to shed light on the possible influence of deltoid muscle density on fracture risk in this specific population.

Methods

A total of 68 patients with computed tomography (CT) images were retrospectively reviewed. Among them, 34 patients presented with fractures following low-energy injuries, while the remaining 34 patients served as controls and underwent CT scans after low-energy injuries without any fractures. The muscle density of the deltoid muscles was assessed at the approximate tubercle of humerus. We compared these parameters between the two groups and conducted analyses considering factors such as age, sex, laterality, and deltoid muscle density of the shoulders.

Results

The demographic factors related to the shoulder did not exhibit any significant association with proximal humeral fracture. However, we observed a noteworthy difference in deltoid muscle density between patients with fractures (40.85 ± 1.35) and the control group (47.08 ± 1.61) (p = 0.0042), indicating a lower muscle density in the fracture group.

Conclusion

Based on the findings of this study, we can conclude that there exists a negative correlation between deltoid muscle density and the incidence of proximal humeral fractures. These results suggest that lower deltoid muscle density may be associated with an increased risk of proximal humeral fractures in the elderly population under investigation.

Age and BMI have different effects on subcutaneous, visceral, liver, bone marrow, and muscle adiposity, as measured by CT and MRI

OBJECTIVE

We analyzed quantitative computed tomography (CT) and chemical shift-encoded magnetic resonance imaging (MRI) data from a Chinese cohort to investigate the effects of BMI and aging on different adipose tissue (AT) depots.

METHODS

In 400 healthy, community-dwelling individuals aged 22 to 83 years, we used MRI to quantify proton density fat fraction (PDFF) of the lumbar spine (L2-L4) bone marrow AT (BMAT), the psoas major and erector spinae (ES) muscles, and the liver. Abdominal total AT, visceral AT (VAT), and subcutaneous AT (SAT) areas were measured at the L2-L3 level using quantitative CT. Partial correlation analysis was used to evaluate the relationship of each AT variable with age and BMI. Multiple linear regression analysis was performed in which each AT variable was evaluated in turn as a function of age and the other five independent AT measurements.

RESULTS

Of the 168 men, 29% had normal BMI (<24.0 kg/m2), 47% had overweight (24.0-27.9 kg/m2), and 24% had obesity (≥ 28.0 kg/m2). In the 232 women, the percentages were 46%, 32%, and 22%, respectively. Strong or very strong correlations with BMI were found for total AT, VAT, and SAT in both sexes. BMAT and ES PDFF was strongly correlated with age in women and moderately correlated in men. In both sexes, BMAT PDFF correlated only with age and not with any of the other AT depots. Psoas PDFF correlated only with ES PDFF and not with age or the other AT depots. Liver PDFF correlated with BMI and VAT and weakly with SAT in men. VAT and SAT correlated with age and each other in both sexes.

CONCLUSIONS

Age and BMI are both associated with adiposity, but their effects differ depending on the type of AT.

Relationship between muscle and subcutaneous adipose tissue size and density and proximal femur bone in elderly women with hip fracture

BACKGROUND

Both osteoporosis and sarcopenia are associated with aging, increasing the likelihood of falls in older adults and consequently raising the risk of hip fractures (HF).

AIMS

To explore the relationship between the size and density of muscle and subcutaneous adipose tissue (SAT) and the bone mineral density (BMD) of the proximal femur in elderly women with HF.

METHODS

Quantitative computed tomography (QCT) was conducted on the hips of 661 female participants who experienced low-energy acute HFs to measure both areal BMD (aBMD) and volume BMD (vBMD). Measurements were taken for the cross-sectional area (CSA) and density of the muscle around the hip and adjacent SAT. Multivariable linear regression models were applied to assess the relationship between these parameters.

RESULTS

Most increases in the density of the gluteus medius and minimus muscle (G.Med/MinM) were correlated with higher BMD in the femoral neck fracture (FNF) group with osteoporosis. In the FNF group, gluteus maximus muscle (G.MaxM) density was negatively associated with the BMD parameters of the proximal femur in individuals with osteoporosis, while they were positively associated with nonosteoporosis. In the intertrochanteric fracture (ITF) group without osteoporosis, both FN aBMD and FN vBMD showed significant correlations with G.Med/MinM density.

DISCUSSION

In women with HFs, bone and muscle are closely related.

CONCLUSIONS

In older women with HFs, density but not CSA of the G.Med/MinM were associated with BMD parameters of the proximal femur. Osteoporosis may influence the relationship between G.MaxM density and proximal femur BMD in elderly women with FNF.

Sarcopenia definitions and their association with fracture risk in older Swedish women

The purpose of this study was to investigate the prevalence of three sarcopenia definitions and their associations with fracture risk in older Swedish women when adjusted for fracture risk assessment (FRAX)-based risk factors; 2,883 women with a mean age of 77.8 years were included. Sarcopenia was defined based on the Sarcopenia Definitions and Outcomes Consortium (SDOC; low handgrip strength [kg] and gait speed (m/s)), revised European Working Group on Sarcopenia in Older People (EWGSOP2; low appendicular lean mass index, appendicular lean mass [ALM]/height; kg/m2], and hand grip strength [kg]), and Asian Working Group for Sarcopenia (AWGS; low ALM (kg), and hand grip strength [kg]) definitions. Femoral neck T-score was obtained from dual-energy X-ray absorptiometry. All fractures, confirmed by X-ray or medical record review, were subsequently categorized as major osteoporotic fractures (MOFs) and hip fractures. Deaths were verified through regional registers. The total follow-up time was 6.4 ± 1.3 (mean ± SD) yr. Cox regression (hazard ratios [HR] and 95% CIs) analyses were performed with adjustment for age, FRAX variables, and femoral neck T-score. Sarcopenia prevalence was 4.5% (n = 129) according to SDOC, 12.5% (n = 360) for EWGSOP2, and 10.3% (n = 296) defined by AWGS. Individuals with sarcopenia defined by SDOC had a higher mortality risk than individuals without sarcopenia (HR: 3.41; 95% CI: 2.51, 4.62) after adjusting for age and FRAX variables. Sarcopenia according to EWGSOP2 and AWGS was not associated with an increased fracture risk after adjusting for age and FRAX variables. Individuals with sarcopenia defined by SDOC had a higher risk for any fractures (HR: 1.48; 95% CI: 1.10, 1.99) and MOF (HR: 1.42; 95% CI: 1.03, 1.98) compared with individuals without sarcopenia after adjusting for clinical risk factors used in FRAX. In conclusion, sarcopenia defined by SDOC, incorporating muscle function/strength, was the only sarcopenia definition associated with fracture risk in older women.

Association of Handgrip Strength with Hip Fracture and Falls in Community-dwelling Middle-aged and Older Adults: A 4-Year Longitudinal Study

OBJECTIVE

Hip fracture and falls are significant health concerns. Handgrip strength (HGS) is closely associated with overall muscle strength and physical health. However, the longitudinal relationship between HGS and the risk of hip fractures and falls remains unclear, particularly regarding gender differences. This longitudinal study aimed to investigate the association between HGS and the risk of hip fracture and falls in individuals aged 45 years and above, considering gender-specific differences over a 4-year period.

METHODS

This study included 10,092 participants (4471 men and 5621 women) aged 45 years and above from the China Health and Retirement Longitudinal Study (CHARLS). Incidents of hip fractures and falls were recorded during a 4-year follow-up, along with various demographic and clinical factors. Participants were categorized into five groups based on their HGS quintiles. Logistic regression models were employed to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CIs) to assess the relationship between HGS and hip fracture/fall risk.

RESULTS

During the 4-year follow-up period, 223 cases of hip fracture (2.2%) and 1831 cases of falls (18.1%) were documented. Notably, higher HGS demonstrated a strong inverse association with the risk of hip fracture in both males and females (p < 0.05). In comparison to the lowest HGS quintile, the adjusted odds ratios (ORs) for hip fracture were 0.46 (0.27-0.78) for the total population, 0.4 (0.19-0.81) for males and 0.48 (0.23-0.98) for females in the highest HGS quintile. Furthermore, a profound and statistically significant negative correlation between HGS and falls was detected (p < 0.05). The adjusted ORs for falls in the highest HGS quintile, compared to the lowest quintile, were 0.62 (0.51-0.76) in the overall population, 0.59 (0.44-0.78) in males, and 0.78 (0.62-0.99) in females.

CONCLUSION

Our findings highlight the significant inverse association between HGS and the risk of hip fracture and falls in both males and females aged 45 years and above. Assessing handgrip strength may serve as a valuable tool for predicting fracture and fall risk.

Association of physical activity with fatty infiltration of muscles after total hip arthroplasty

OBJECTIVE

This study aimed to investigate the association between muscle density as an indicator of fatty infiltration of lower extremity muscles and physical activity (PA) after total hip arthroplasty (THA) and identify the patient characteristics with high postoperative PA.

METHODS

This study included 62 female patients who underwent THA for unilateral hip osteoarthritis. Muscle density of the gluteus maximus, gluteus medius, iliopsoas, and quadriceps muscles was measured using computed tomography (CT). PA was assessed using University of California, Los Angeles (UCLA) activity scores. CT and UCLA activity score were obtained before and 1 year after THA. The patients were divided into two groups, sufficient (score ≥ 6) and insufficient (score < 6) activity groups, based on their level of PA as determined by their UCLA activity score 1 year after THA. The association of PA with the amount of changes in muscle density was examined with Spearman's rank correlation coefficient. Logistic regression analysis was performed to identify postoperative factors determining PA at 1 year after THA.

RESULTS

Spearman's rank correlation coefficient showed a significantly positive association between recovery in PA and an increase in muscle density of the gluteus maximus, gluteus medius, iliopsoas, and quadriceps muscles. Additionally, logistic regression analysis confirmed that postoperative muscle densities of the gluteus maximus and quadriceps muscles were variables determining the PA 1 year after THA.

CONCLUSION

The findings of this study indicated that the improvement of fatty infiltration in lower limb muscles, especially in the gluteus maximus and quadriceps, is likely to promote the increase in postoperative PA.

Muscle density, but not size, is independently associated with cognitive health in older adults with hip fractures

Emerging evidence indicates a complex interplay between skeletal muscle and cognitive function. Despite the known differences between muscle quantity and quality, which can be measured via computed tomography (CT), the precise nature of their associations with cognitive performance remain underexplored. To investigate the links between muscle size and density and cognitive impairment (CI) in the older adults with hip fractures, we conducted a post hoc, cross-sectional analysis within a prospective cohort study on 679 patients with hip fractures over 65. Mini-Mental State Examination (MMSE) and routine hip CT imaging were utilized to assess cognition function and muscle characteristics in older adults with hip fractures. The CT scans provided data on cross-sectional area and attenuation for the gluteus maximus (G.MaxM) and the combined gluteus medius and minimus (G.Med/MinM). Participants were categorized into CI and non-CI groups based on education levels and MMSE scores. Multivariate logistic regressions, propensity score (PS) methods, and subgroup analysis were employed to analyze associations and validate findings. This study included 123 participants (81.6 ± 6.8 years, 74% female) with CI and 556 participants (78.5 ± 7.7 years, 72% female) without. Compared to the non-CI group, muscle parameters, especially density, were significantly lower in the CI group. Specifically, G.Med/Min muscle density, but not size was robustly associated with CI (odds ratio (OR) = 0.77, 95% confidence interval = 0.62-0.96, P = 0.02), independent of other medical situations. Sensitivity analysis corroborated that G.Med/Min muscle density was consistently lower in the CI group than the non-CI group, as evidenced in the PS matched (P = 0.024) and weighted cohort (P = 0.033). Enhanced muscle parameters, particularly muscle density in the G.Med/MinM muscle, correlate with a lower risk of CI. Muscle density demonstrates a stronger association with cognitive performance than muscle size, highlighting its potential as a key focus in future cognitive health research.

Deep Learning-Based Fully Automated Segmentation of Regional Muscle Volume and Spatial Intermuscular Fat Using CT

RATIONALE AND OBJECTIVES

We aim to develop a CT-based deep learning (DL) system for fully automatic segmentation of regional muscle volume and measurement of the spatial intermuscular fat distribution of the gluteus maximus muscle.

MATERIALS AND METHODS

A total of 472 subjects were enrolled and randomly assigned to one of three groups: a training set, test set 1, and test set 2. For each subject in the training set and test set 1, we selected six slices of the CT images as the region of interest for manual segmentation by a radiologist. For each subject in test set 2, we selected all slices of the gluteus maximus muscle on the CT images for manual segmentation. The DL system was constructed using Attention U-Net and the Otsu binary thresholding method to segment the muscle and measure the fat fraction of the gluteus maximus muscle. The segmentation results of the DL system were evaluated using the Dice similarity coefficient (DSC), Hausdorff distance (HD), and the average surface distance (ASD) as metrics. Intraclass correlation coefficients (ICCs) and Bland-Altman plots were used to assess agreement in the measurements of fat fraction between the radiologist and the DL system.

RESULTS

The DL system showed good segmentation performance on the two test sets, with DSCs of 0.930 and 0.873, respectively. The fat fraction of the gluteus maximus muscle measured by the DL system was in agreement with the radiologist (ICC=0.748).

CONCLUSION

The proposed DL system showed accurate, fully automated segmentation performance and good agreement with the radiologist at fat fraction evaluation, and can be further used for muscle evaluation.

Effect of psoas and gluteus medius muscles attenuation on hip fracture type

INTRODUCTION

Sarcopenia is defined as a progressive loss of muscle mass and function with increased age. The measurement of muscle mass and attenuation on the axial computed tomography (CT) scan has been reported to be a good indicator for sarcopenia in previous literature. This study aimed to compare muscle mass between the intertrochanteric fracture and femoral neck fracture groups by accurately measuring muscle mass around the hip joint using a CT scan.

METHODS

The cases were matched according to age and gender on a 1-to-1 basis. As a result, a total of 400 patients, 200 patients in each group with the same age and gender characteristics, were included in the study. At the disc of L4-L5 level, the cross-sectional area (CSA) of the psoas muscle was evaluated, and at the disc of L5-S1 level, the CSA of the psoas, iliacus and gluteus medius muscles were evaluated. In addition, attenuation was evaluated using the average Hounsfield Unit (HU) for the specific area.

RESULTS

The mean age of 400 patients (262 females, 138 male) included in the study was 78.49 ± 7.67 years. It was observed that the mean HU values of the patients in the femoral neck fracture group were significantly higher than the intertrochanteric fracture group (p < 0.001, p = 0.008; respectively). At the same time, the mean HU values of the gluteus medius muscle were higher in the femoral neck fracture group (p < 0.001), but in contrast with the psoas muscle, the CSA values of gluteus medius muscle were significantly higher in the intertrochanteric fracture group (p = 0.017).

CONCLUSIONS

Fatty degeneration of the psoas muscle among the muscles around the hip may affect the type of hip fracture. Elderly patients with strong psoas muscles may experience femoral neck fracture due to contraction and torsion during falling.

Association Between Pelvic Bone Computed Tomography-Derived Body Composition and Patient Outcomes in Older Adults With Proximal Femur Fracture

OBJECTIVE

To investigate the association between pelvic bone computed tomography (CT)-derived body composition and patient outcomes in older adult patients who underwent surgery for proximal femur fractures.

MATERIALS AND METHODS

We retrospectively identified consecutive patients aged ≥ 65 years who underwent pelvic bone CT and subsequent surgery for proximal femur fractures between July 2018 and September 2021. Eight CT metrics were calculated from the cross-sectional area and attenuation of the subcutaneous fat and muscle, including the thigh subcutaneous fat (TSF) index, TSF attenuation, thigh muscle (TM) index, TM attenuation, gluteus maximus (GM) index, GM attenuation, gluteus medius and minimus (Gmm) index, and Gmm attenuation. The patients were dichotomized using the median value of each metric. Multivariable Cox regression and logistic regression models were used to determine the association between CT metrics with overall survival (OS) and postsurgical intensive care unit (ICU) admission, respectively.

RESULTS

A total of 372 patients (median age, 80.5 years; interquartile range, 76.0-85.0 years; 285 females) were included. TSF attenuation above the median (adjusted hazard ratio [HR], 2.39; 95% confidence interval [CI], 1.41-4.05), GM index below the median (adjusted HR, 2.63; 95% CI, 1.33-5.26), and Gmm index below the median (adjusted HR, 2.33; 95% CI, 1.12-4.55) were independently associated with shorter OS. TSF index (adjusted odds ratio [OR], 6.67; 95% CI, 3.13-14.29), GM index (adjusted OR, 3.45; 95% CI, 1.49-7.69), GM attenuation (adjusted OR, 2.33; 95% CI, 1.02-5.56), Gmm index (adjusted OR, 2.70; 95% CI, 1.22-5.88), and Gmm attenuation (adjusted OR, 2.22; 95% CI, 1.01-5.00) below the median were independently associated with ICU admission.

CONCLUSION

In older adult patients who underwent surgery for proximal femur fracture, low muscle indices of the GM and gluteus medius/minimus obtained from their cross-sectional areas on preoperative pelvic bone CT were significant prognostic markers for predicting high mortality and postsurgical ICU admission.

The lumbar spinal endplate lesions grades and association with lumbar disc disorders, and lumbar bone mineral density in a middle-young general Chinese population

BACKGROUND

Lumbar vertebral endplates lesions (LEPLs), one of the etiologies of low back pain (LBP), are one of the most prevalent causes of health-care costs. Despite progressively becoming the focus in recent years, almost all studies have concentrated on symptomatic patients rather than general populations. As a result, our study was designed to determine the prevalence and distribution patterns of LEPLs in a middle-young general population, as well as their associations with lumbar disc herniation (LDH), lumbar disc degeneration (LDD), and lumbar vertebral volumetric bone mineral density (vBMD).

METHODS

Seven hundred fifty-four participants aged 20-60 years were recruited from the subjects enrolled in a 10-year longitudinal study of degeneration of the spine and knee being conducted at the Beijing Jishuitan Hospital and 4 of them were excluded due to the missing of MRIs. In this observational study, a lumbar quantitative computed tomography (QCT) and MRI scan were performed among participants within 48 h. T2-weighted sagittal lumbar MRI images for all included subjects were identified for LEPLs by two independent observers based on morphological and local characteristics. Lumbar vertebral vBMD was measured with QCT. The age, BMI, waistline, hipline, lumbar vBMD, LDD, and LDH were measured to investigate their associations with LEPLs.

RESULTS

The prevalence of LEPLs was higher among the male subjects. 80% of endplates were recognition as no lesions with a substantial disparity between female (75.6%) and male subjects (83.4%) (p < 0.001). The most common lesions were "wavy/irregular" and "notched", and "fracture" is most involved in L3-4 inferior endplate both in two genders. LEPLs were found to be associated with LDH (≥ 2 levels: OR = 6.859, P < 0.001; 1 level: OR = 2.328, P = 0.002 in men. OR = 5.004, P < 0.001; OR = 1.805, P = 0.014 in women) reference for non-LDH, and hipline in men (OR = 1.123, P < 0.001).

CONCLUSIONS

LEPLs are the common findings on lumbar MRIs in general population, particularly in men. The presence of these lesions and advance from slightly to severely could be mainly attributed to LDH and men's higher hipline.

Human skeletal muscle-specific atrophy with aging: a comprehensive review

Age-related skeletal muscle atrophy appears to be a muscle group-specific process, yet only a few specific muscles have been investigated and our understanding in this area is limited. This review provides a comprehensive summary of the available information on age-related skeletal muscle atrophy in a muscle-specific manner, nearly half of which comes from the quadriceps. Decline in muscle-specific size over ∼50 yr of aging was determined from 47 cross-sectional studies of 982 young (∼25 yr) and 1,003 old (∼75 yr) individuals and nine muscle groups: elbow extensors (-20%, -0.39%/yr), elbow flexors (-19%, -0.38%/yr), paraspinals (-24%, -0.47%/yr), psoas (-29%, -0.58%/yr), hip adductors (-13%, -0.27%/yr), hamstrings (-19%, -0.39%/yr), quadriceps (-27%, -0.53%/yr), dorsiflexors (-9%, -0.19%/yr), and triceps surae (-14%, -0.28%/yr). Muscle-specific atrophy rate was also determined for each of the subcomponent muscles in the hamstrings, quadriceps, and triceps surae. Of all the muscles included in this review, there was more than a fivefold difference between the least (-6%, -0.13%/yr, soleus) to the most (-33%, -0.66%/yr, rectus femoris) atrophying muscles. Muscle activity level, muscle fiber type, sex, and timeline of the aging process all appeared to have some influence on muscle-specific atrophy. Given the large range of muscle-specific atrophy and the large number of muscles that have not been investigated, more muscle-specific information could expand our understanding of functional deficits that develop with aging and help guide muscle-specific interventions to improve the quality of life of aging women and men.

Comparative Study of Different Entry Spots on Postoperative Gluteus Medius Muscle Cross-Sectional Area in Patients With Intertrochanteric Fractures Nailing

Introduction In a preliminary study of cephalo-medullary (CM) nailing in patients with femoral intertrochanteric fractures, the authors of this study found a 25% to 30% decrease in muscle strength, especially abduction force, during the postoperative follow-up period. This decline was partially attributed to the entry point for the nail insertion causing damage to the gluteus medius tendon at the junction of the greater trochanter after reaming. Therefore, we assumed that changing the position of nail insertion to a "bald spot (BS)" could mitigate postoperative functional impairment. Automated computed tomography (CT) imaging of skeletal muscle cross-sectional area (CSA) and adipose tissue ratio (ATR) can show pathological changes on the operated side compared with the non-operated side. In this study, the authors quantified the difference in postoperative CSA and ATR of the gluteus medius muscle after bald spot nailing versus nail insertion through the conventional tip of the greater trochanter. It was hypothesized that bald spot nailing could avoid significant injury to the gluteus medius muscle. Materials and methods Patients with femoral intertrochanteric fractures were grouped according to the site of cephalo-medullary nailing: greater trochanteric tip (TIP) in 27 patients (8 men and 19 women, mean age 84.9±5.1 years) and BS in 16 patients (3 men and 13 women, mean age 86.9±6.2 years). The CSA and ATR of the gluteus medius muscles were assessed in three slices (A, B, and C from proximal to distal). Each slice was manually traced and automatically calculated based on its contour. Adipose tissue (-100 to -50 in Hounsfield units) in the designated area was distinguished by a bimodal image histogram resulting from the distribution of CT numbers of adipose tissue and muscle. The body mass index (BMI) was used to correct the CSA in each patient. Results In the TIP group, the mean CSA values (mm²) from the non-operated/operated sides were as follows: slice A, 2180.2 ± 616.5/1976.3 ± 421.2; slice B, 2112.3 ± 535.7/1857.7 ± 386.7; and slice C: 1671.8 ± 460.0/1404.1 ± 404.3 (p<0.01 in slices A, B, and C). In the BS group, slice A was 2044.1 ± 473.0/2016.9 ± 388.4; slice B was 2073.2 ± 540.7/1848.3 ± 411.1; and slice C was 1659.1 ± 477.2/1468.5 ± 341.7 (p=0.34 in slice A, and p<0.05 in slices B and C, respectively). The mean CSA values (mm²) of the non-operated minus operated side between the TIP/BS groups were as follows: slice A, 241.3 ± 424.3/-11.8 ± 285.6; slice B, 290.3 ± 313.0/211.8 ± 333.2; and slice C, 276.4 ± 270.4/162.8 ± 319.3 (p < 0.05 in slice A, 0.45, 0.24 in slices B, C, respectively). The mean adjusted CSA per BMI values (mm²) of the non-operated minus the operated side between the TIP/BS groups were slice A, 10.6 ± 19.7/-0.4 ± 14.8; slice B, 13.3 ± 15.0/10.1 ± 16.3; and slice C, 13.1 ± 13.4/ 8.7 ± 15.3 (p < 0.05 in slice A and 0.54 and 0.36 in slices B and C, respectively). Conclusion Nail insertion at the bald spot resulted in a significantly smaller decrease in the CSA of the gluteus medius muscle compared with the conventional tip entry. In addition, an examination of BMI-adjusted CSA showed that CSA was maintained in some image slices. These results suggest that nailing from the BS of the greater trochanter can reduce damage to the gluteus medius muscle and highlight the importance of imaging beyond the usual assessment of skeletal changes.

Extensive and Differential Deterioration of Hip Muscles May Preexist in Older Adults with Hip Fractures: Evidence from a Cross-Sectional Study

Hip muscles play an increasingly important role in lower limb function with aging. Investigating the deterioration of hip muscles and its relationship with hip fracture (HF) may help identify older adults prone to fall. In this study, patients with fall-related HF within 48 h and non-fracture controls aged ≥ 60 years were enrolled. The cross-sectional area (size) and attenuation (density) of the hip flexors, extensors, adductors, and abductors were calculated after segmentation on computed tomography images. The correlation of muscle parameters with HF and age were evaluated using logistic and multiple regression, respectively. Discrimination of HF was analyzed by receiver-operating characteristic analyses. A total of 220 patients and 91 controls were included. The size of the flexors, extensors, and abductors, and the density of the flexors, adductors, and abductors were lower in patients with HF after adjustment for sex, age, and body mass index (BMI). However, decreased muscle size was only observed in hip extensors in patients aged 60-74 years. Decreased muscle size was associated with HF independent of sex, age, BMI, and hip trabecular bone mineral density. Abductor size exhibited a significantly larger negative correlation with age in patients compared to controls. Including abductor size or all muscle size was effective for discrimination of HF in patients aged ≥ 75 years. In conclusion, older adults with HF may have sustained extensive and differential hip muscle deterioration before the injury; extensor atrophy in younger-old age and consideration of a closer relationship between abductor size and age deserve attention.

Opportunistic Screening Techniques for Analysis of CT Scans

PURPOSE OF REVIEW

Opportunistic screening is a combination of techniques to identify subjects of high risk for osteoporotic fracture using routine clinical CT scans prescribed for diagnoses unrelated to osteoporosis. The two main components are automated detection of vertebral fractures and measurement of bone mineral density (BMD) in CT scans, in which a phantom for calibration of CT to BMD values is not used. This review describes the particular challenges of opportunistic screening and provides an overview and comparison of current techniques used for opportunistic screening. The review further outlines the performance of opportunistic screening.

RECENT FINDINGS

A wide range of technologies for the automatic detection of vertebral fractures have been developed and successfully validated. Most of them are based on artificial intelligence algorithms. The automated differentiation of osteoporotic from traumatic fractures and vertebral deformities unrelated to osteoporosis, the grading of vertebral fracture severity, and the detection of mild vertebral fractures is still problematic. The accuracy of automated fracture detection compared to classical radiological semi-quantitative Genant scoring is about 80%. Accuracy errors of alternative BMD calibration methods compared to simultaneous phantom-based calibration used in standard quantitative CT (QCT) range from below 5% to about 10%. The impact of contrast agents, frequently administered in clinical CT on the determination of BMD and on fracture risk determination is still controversial. Opportunistic screening, the identification of vertebral fracture and the measurement of BMD using clinical routine CT scans, is feasible but corresponding techniques still need to be integrated into the clinical workflow and further validated with respect to the prediction of fracture risk.

High prevalence of sarcopenia and myosteatosis in patients undergoing hemodialysis

BACKGROUND AND PURPOSE

Sarcopenia is highly prevalent (28.5-40.3%) in patients undergoing hemodialysis and leads to poor clinical outcomes. However, the association between muscle quality and sarcopenia in patients receiving hemodialysis remains unclear. Therefore, we aimed to explore the association between muscle cross-sectional area (CSA) and proton-density fat-fraction (PDFF) in patients with sarcopenia undergoing hemodialysis.

METHODS

Seventy-six patients undergoing hemodialysis for > 3 months were enrolled. Their handgrip strength (HGS), short physical performance battery (SPPB) performance, and appendicular skeletal muscle mass index (ASMI) were measured. Sarcopenia was defined using the Asian Working Group for Sarcopenia 2019 consensus update. All patients underwent quantitative magnetic resonance imaging. CSA and PDFF were measured for the thigh, trunk, and gluteus muscles.

RESULTS

The prevalence of probable, confirmed, and severe sarcopenia in this study was 73.7%, 51.3%, and 22.4%, respectively. Older age (OR: 1.061, P < 0.003); lower body mass index (BMI) (OR: 0.837, P = 0.008), albumin (OR: 0.765, P = 0.004), prealbumin (OR: 0.987, P = 0.001), predialysis blood urea nitrogen (BUN) (OR: 0.842, P < 0.001), predialysis creatinine (OR: 0.993, P < 0.001), phosphorus (OR: 0.396, P = 0.047); lower CSA of the thigh (OR: 0.58, P = 0.035), third lumbar (L3) trunk (OR: 0.37, P = 0.004), gluteus minimus and medius (OR: 0.28, P = 0.001), and gluteus maximus (OR: 0.28, P= 0.001); and higher PDFF of the thigh (OR: 1.89, P = 0.036) and L3 trunk (OR: 1.71, P = 0.040) were identified as sarcopenia risk factors. The gluteus minimus and medius CSA was lower in patients with sarcopenia than in those without after adjusting for age and BMI (OR: 0.37, P = 0.017). Higher thigh (P = 0.031) and L3 trunk (P = 0.006) muscle PDFF were significantly associated with lower HGS. Furthermore, higher thigh (P = 0.011) and L3 trunk (P = 0.010) muscle PDFF were also inversely correlated with lower ASMI.

CONCLUSION

Our findings demonstrate the high prevalence of sarcopenia and myosteatosis in patients undergoing hemodialysis and might trigger a paradigm shift in intervention strategies for patients receiving hemodialysis.

Fatty infiltration of hip muscles and trochanteric soft tissue thickness are associated with hip fractures in the elderly

PURPOSE

Apart from bone conditions, muscle and soft tissue parameters might also influence hip fractures. We aimed to evaluate the association between hip muscle and trochanteric soft tissue parameters and hip fractures.

METHODS

We retrospectively reviewed 60 patients with hip fractures and 114 controls without hip fractures. Cases and controls were matched for age, sex, and body mass index using propensity score matching. Muscle cross-sectional area (CSA), mean attenuation, and fatty infiltration rate (FIR) (proportion of intramuscular fat content) were measured on CT images for the gluteus maximus, the gluteus medius/minimus, and the anterior and medial compartments of the upper thigh. Trochanteric soft tissue thickness (TSTT) and femoral neck attenuation were also measured. Univariate and multivariate analyses were conducted to identify potential risk factors of hip fractures.

RESULTS

Patients with hip fractures had significantly lower femoral neck attenuation, TSTT, and CSA of the gluteus maximus and anterior compartment than controls. FIR of all hip muscle groups were significantly higher in hip fracture patients than controls. Multivariate analysis revealed that every 1% increase in FIR of medial compartment independently increased the odds of hip fractures by 23.7% (OR = 1.237, 95% CI = 1.093-1.401) and every 1 cm longer TSTT independently decreased the odds by 32.8% (OR = 0.672, 95% CI = 0.477-0.946).

CONCLUSION

Fatty infiltration of hip muscles can better discriminate hip fractures than muscle area. Increased TSTT is independently associated with low fracture risk.

Determinants of muscle density and clinical outcomes: Findings from the Hertfordshire Cohort Study

PURPOSE

The age-related loss of skeletal muscle mass and strength is associated with adverse health outcomes. However, to date, peripheral quantitative computed tomography (pQCT)-derived muscle density has been little studied. We used a well characterised cohort of older adults to identify lifestyle and anthropometric determinants of pQCT-derived muscle density measured 11 years later, and to report relationships between pQCT-derived muscle density with history of falls and prevalent fractures.

METHODS

A lifestyle questionnaire was administered to 197 men and 178 women, aged 59-70 at baseline. After a median of 11.5 (IQR 10.9, 12.3) years, pQCT (Stratec XCT2000) of the radius and tibia was performed to measure forearm muscle density (FMD) and calf muscle density (CMD). Presence of falls and fractures since the age of 45 were determined through participant recall; vertebral fractures were also ascertained through vertebral fracture assessment using iDXA. Total hip BMD (TH aBMD) was assessed using DXA. Baseline characteristics in relation to muscle density at follow-up were examined using linear regression; associations between muscle density and prior falls and fractures were investigated using logistic regression. All analyses were adjusted for sex and age.

RESULTS

Mean (SD) age at muscle density measurement was 76.3 (2.6) years. Mean (SD) FMD was 79.9 (3.1) and 77.2 (3.2) among males and females, respectively; CMD was 80.7 (2.6) and 78.5 (2.6) among males and females, respectively. Significant sex-differences in muscle density were observed at each site (p < 0.001). Female sex, lower weight, and lower body mass index were associated (p < 0.05) with both lower FMD and CMD. Additional correlates of lower CMD included older age and shorter stature. Lifestyle measures were not associated with muscle density in this cohort. Lower FMD was related to increased risk of previous fracture (odds ratio (95 % CI) per SD lower FMD: 1.42 (1.07, 1.89), p = 0.015) but not after adjustment for TH aBMD (p > 0.08). No significant relationships were seen between muscle density and falls.

CONCLUSION

Female sex, older age, and lower BMI were associated with subsequent lower muscle density in older community-dwelling adults. Lower FMD was related to increased risk of previous fracture. Changes in muscle density over time might precede adverse outcomes such as falls and fractures and may be a long-term predictor of frailty. It could be also suggested that muscle density could be a more clinically meaningful surrogate of functional decline and disability than muscle size or mass, but more studies are needed to support this notion.

Internal calibration for opportunistic computed tomography muscle density analysis

INTRODUCTION

Muscle weakness can lead to reduced physical function and quality of life. Computed tomography (CT) can be used to assess muscle health through measures of muscle cross-sectional area and density loss associated with fat infiltration. However, there are limited opportunities to measure muscle density in clinically acquired CT scans because a density calibration phantom, allowing for the conversion of CT Hounsfield units into density, is typically not included within the field-of-view. For bone density analysis, internal density calibration methods use regions of interest within the scan field-of-view to derive the relationship between Hounsfield units and bone density, but these methods have yet to be adapted for muscle density analysis. The objective of this study was to design and validate a CT internal calibration method for muscle density analysis.

METHODOLOGY

We CT scanned 10 bovine muscle samples using two scan protocols and five scan positions within the scanner bore. The scans were calibrated using internal calibration and a reference phantom. We tested combinations of internal calibration regions of interest (e.g., air, blood, bone, muscle, adipose).

RESULTS

We found that the internal calibration method using two regions of interest, air and adipose or blood, yielded accurate muscle density values (< 1% error) when compared with the reference phantom. The muscle density values derived from the internal and reference phantom calibration methods were highly correlated (R2 > 0.99). The coefficient of variation for muscle density across two scan protocols and five scan positions was significantly lower for internal calibration (mean = 0.33%) than for Hounsfield units (mean = 6.52%). There was no difference between coefficient of variation for the internal calibration and reference phantom methods.

CONCLUSIONS

We have developed an internal calibration method to produce accurate and reliable muscle density measures from opportunistic computed tomography images without the need for calibration phantoms.

Compartment-specific effects of muscle strength on bone microarchitecture in women at high risk of osteoporosis

BACKGROUND

It is well known that skeletal integrity is influenced by the musculature. Poor muscle strength (i.e. sarcopenia) is considered a major predictor of fragility fractures. While this observation appears particularly relevant for older women with increased risk of osteoporosis, there has been no comprehensive investigation to determine the influence of muscle performance on compartment-specific bone microarchitecture in multiple body regions.

METHODS

We retrospectively analysed data from different muscle performance and bone microarchitecture assessments in 230 women (aged 21 to 87 years) at high risk of osteoporosis. Muscle performance tests included grip strength and chair rising test (CRT) combined with mechanography. Balance was determined by Romberg posturography. Areal bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA) at the hip and lumbar spine. Compartment-specific volumetric BMD, microarchitecture, and geometry were assessed by second-generation high-resolution peripheral quantitative computed tomography (HR-pQCT) at multiple skeletal sites (distal radius, tibia, and fibula). Regression models were applied to test for interactions between muscle and bone parameters. Subgroups were defined to compare women with osteoporosis and osteosarcopenia regarding BMD and microarchitecture.

RESULTS

While osteoporosis was diagnosed in 115/230 (50.0%) women, sarcopenia was detected in 38/230 (16.5%). Positive associations of both grip strength and CRT maximum force with cortical geometric and microarchitectural parameters were detected at all measured sites, with the strongest effect applying to CRT maximum force and tibial parameters (e.g. tibial cortical area R2  = 0.36, P < 0.0001, and tibial cortical thickness R2  = 0.26, P < 0.0001). Balance parameters showed much weaker or no associations with HR-pQCT parameters. Major associations between muscle strength and trabecular parameters could not be confirmed. Age and body mass index were confirmed as negative and positive predictors for several microarchitectural parameters, respectively. An independent predictive value of grip strength on radial, tibial, and fibular (all P < 0.01) cortical area and of CRT maximum relative force on cortical thickness (all P < 0.05) was revealed. Women with osteosarcopenia showed significantly reduced cortical HR-pQCT parameters but no differences in DXA values compared with women with osteoporosis but no sarcopenia. Stratification by fracture and treatment status revealed that vertebral fractures and denosumab treatment altered the muscle-bone interaction.

CONCLUSIONS

A systemic interaction between muscle strength and bone microarchitecture was demonstrated, and this interaction appears to be primarily with the cortical bone compartment. The value of muscle assessments in fracture risk evaluation may be partly mediated by their effects on bone microarchitecture.

Computed tomography-based paravertebral muscle density predicts subsequent vertebral fracture risks independently of bone mineral density in postmenopausal women following percutaneous vertebral augmentation

BACKGROUND

The risk of subsequent vertebral fractures (SVF) after the primary vertebral fracture cannot be explained by lower bone mineral density (BMD) alone. Computed tomography (CT) measurements of paravertebral muscle density (PMD) are recognized radiographic markers used to predict physical function, fragile fractures.

AIMS

This study aims to investigate the relationship between PMD and the risk of SVF in cohorts of postmenopausal women, and to determine if combining both PMD and BMD measures derived from CT can improve the accuracy of predicting SVF.

METHODS

This study enrolled 305 postmenopausal women between the ages of 50 and 88 for 3 years of follow-up studies. Trabecular attenuation (Hounsfield units, HU) was measured at L1 level and muscle attenuation of paravertebral muscle at L3 level on preoperative lumbar CT scans to determine the L1 BMD and L3 PMD. Kaplan-Meier analysis was applied to evaluate SVF-free survival. The hazard ratios (HRs) of PMD for SVF events were estimated with the Cox proportional hazards model. The predictive values of L1 BMD and L3 PMD for SVF were quantified using the Receiver-Operating Characteristic (ROC) curve.

RESULT

During the 3 years of follow-up studies, 88 patients (28.9%) suffered an SVF. ROC curve analysis demonstrated that an L3 PMD threshold of 32 HU had a sensitivity of 89.8% and a specificity of 62% for the prediction of SVF. Kaplan-Meier analysis showed that L3 PMD ≤ 32 HU was significantly associated with lower SVF-free survival (p < 0.001; log-rank test). After adjusting for age, BMI, diabetes, postoperative osteoporosis treatment, handgrip strength, L1 BMD, multivariate analyses also indicated a persistent modest effect of L3 PMD on SVF-free survival. The area under the ROC curve of L3 PMD and L1 BMD, combined to predict the risk of SVF, was 0.790, which was significantly higher than the value for L1 BMD alone (0.735). L3 PMD and L1 BMD significantly improved the accuracy of SVF risk prediction compared with L1 BMD alone, which was confirmed by reclassification improvement measures. The inclusion of handgrip strength and postoperative osteoporosis treatment in the model further improved SVF prediction accuracy, and PMD remained significant in the model.

CONCLUSION

Decreased L3 PMD is an independent risk predictor of SVF. Combined CT-based L1 BMD and L3 PMD can significantly improve the accuracy of predicting the risk of SVF in postmenopausal women who have suffered prior osteoporotic vertebral fractures.

Peptic Ulcer Disease and Risk of Hip Fracture: A General Population-based Cohort Study

AIMS

Previous studies reported proton pump inhibitor (PPI) use may increase the risk of fracture; however, the findings may be susceptible to indication bias because peptic ulcer disease (PUD), 1 major indication for PPIs, may affect skeletal health. Determining whether PUD would increase hip fracture risk may help identify high-risk populations and explore risk factors.

METHODS

We conducted a cohort study using data from The Health Improvement Network (THIN) in the United Kingdom. THIN contains patient information such as disease diagnosis and medicine prescriptions. Up to 5 non-PUD individuals (n = 138 265) were matched to each case of incident PUD (n = 27 653) by age, sex, and body mass index. We examined the association between PUD and hip fracture by a multivariable Cox proportional hazard model. We repeated the same analysis among individuals with incident PUD and gastroesophageal reflux disease (GERD) (n = 27 160), another disease with similar indication for PPIs, as a positive control exposure.

RESULTS

Over a mean of 5.6 years of follow-up, hip fracture occurred in 589 individuals with PUD and 2015 individuals without PUD (3.8 vs 2.6/1000 person-years), with a multivariable-adjusted hazard ratio (HR) being 1.44 (95% confidence interval [CI], 1.31-1.58). The association persisted among subgroups stratified by sex and age. In positive control exposure analysis, the hip fracture risk was also higher in PUD than GERD (3.8 vs 2.4/1000 person-years; multivariable-adjusted HR = 1.65; 95% CI, 1.45-1.7).

CONCLUSIONS

This general population-based cohort study suggests, after controlling for acid-lowering medication and other potential risk factors, PUD is independently associated with an increased risk of hip fracture.

Greater bone marrow fat and myosteatosis are associated with lower vBMD but not asymptomatic vertebral fracture

OBJECTIVES

Organ fat may affect bone metabolism and be associated with vertebral fracture (VF). This study aimed to explore relationships between VF, adiposity indexes measured by MRI, and volumetric BMD (vBMD) measured by quantitative CT (QCT).

METHODS

Four hundred volunteers, ranging in age from 22 to 83 years, were recruited and underwent same-day abdominal QCT and chemical shift-encoded (CSE) MRI. We used MRI to quantify the fat content of bone marrow (BMF), psoas major and paraspinal muscles, and the liver. Abdominal fat, VF, and vBMD of the lumbar spine were measured by QCT. For VF discrimination analysis, we examined both the whole cohort (60 VF cases in 30 men and 30 women) and a restricted subgroup of those aged over 50 years (50 VF cases in 23 men and 27 women).

RESULTS

Amongst the men, a 1 SD increase in BMF was associated with a 27.67 (95% CI, -32.71 to -22.62) mg/cm³ decrease in vBMD after adjusting for age and BMI. Amongst women, all adiposity indexes except for liver fat were significantly associated with vBMD, with BMF having the strongest association (β, -24.00; 95% CI, -28.54 to -19.46 mg/cm³). Similar findings were also observed in participants aged over 50 years. The associations of adiposity indexes with vertebral fracture were not significant after adjusting for age in both sexes aged over 50 years.

CONCLUSIONS

In both sexes, higher bone marrow fat was associated with lower vBMD at the spine. However, marrow fat and other adipose tissues were not associated with radiographic-based prevalent vertebral fractures.

KEY POINTS

• In both sexes, higher bone marrow fat was associated with lower vBMD at the spine. • Among women, all adiposity indexes except for liver fat content were significantly associated with vBMD, with bone marrow fat having the strongest association. • Marrow fat and other adipose tissues were not associated with radiographic-based asymptomatic vertebral fractures.

Muscle density is an independent risk factor of second hip fracture: a prospective cohort study

BACKGROUND

Patients with a first hip fracture are at high risk of fracturing their other hip. Despite this, preventive therapy is often not given. Because little is known about specific risk factors of a second hip fracture, we investigated the association with areal bone mineral density (aBMD), muscle size, and density. We also investigated whether muscle parameters predict the risk of a contralateral fracture independently of aBMD.

METHODS

Three groups were included, one without hip fracture (a subcohort of the China Action on Spine and Hip Status study), one with a first, and one with a second hip fracture. Subjects with fractures were recruited from the longitudinal Chinese Second Hip Fracture Evaluation (CSHFE). Computed tomography scans of CSHFE patients, which were obtained immediately following their first fracture, were used to measure cross-sectional area and density of the gluteus maximus (G.MaxM) and gluteus medius and minimus (G.Med/MinM) muscles. Computed tomography X-ray absorptiometry was used to measure aBMD of the contralateral femur. Median follow-up time to second fracture was 4.5 years. Cox proportional hazards models were used to compute hazard ratios (HR) of second hip fracture risk in subjects with a first hip fracture. Multivariate logistic regressions were used to compare odds ratios (OR) for the risk of a first and second hip fracture.

RESULTS

Three hundred and one participants (68.4 ± 6.1 years, 64% female) without and 302 participants (74.6 ± 9.9 years, 71% female) with a first hip fracture were included in the analysis. Among the latter, 45 (79.2 ± 7.1 years) sustained a second hip fracture. ORs for first hip fracture were significant for aBMD and muscle size and density. ORs for a second fracture were smaller by a factor of 3 to 4 and no longer significant for femoral neck (FN) aBMD. HRs for predicting second hip fracture confirmed the results. G.Med/MinM density (HR, 1.68; CI, 1.20-2.35) and intertrochanter aBMD (HR, 1.62; CI, 1.13-2.31) were the most significant. FN aBMD was not significant. G.Med/MinM density remained significant for predicting second hip fracture after adjustment for FN (HR, 1.66; Cl, 1.18-2.30) or total hip aBMD (HR, 1.50; 95% Cl, 1.04-2.15).

CONCLUSIONS

Density of the G.Med/MinM muscle is an aBMD independent predictor of the risk of second hip fracture. Intertrochanteric aBMD is a better predictor of second hip fracture than FN and total hip aBMD. These results may trigger a paradigm shift in the assessment of second hip fracture risk and prevention strategies.

A deep learning-based approach to automatic proximal femur segmentation in quantitative CT images

Automatic CT segmentation of proximal femur has a great potential for use in orthopedic diseases, especially in the imaging-based assessments of hip fracture risk. In this study, we proposed an approach based on deep learning for the fast and automatic extraction of the periosteal and endosteal contours of proximal femur in order to differentiate cortical and trabecular bone compartments. A three-dimensional (3D) end-to-end fully convolutional neural network (CNN), which can better combine the information among neighbor slices and get more accurate segmentation results by 3D CNN, was developed for our segmentation task. The separation of cortical and trabecular bones derived from the QCT software MIAF-Femur was used as the segmentation reference. Two models with the same network structures were trained, and they achieved a dice similarity coefficient (DSC) of 97.82% and 96.53% for the periosteal and endosteal contours, respectively. Compared with MIAF-Femur, it takes half an hour to segment a case, and our CNN model takes a few minutes. To verify the excellent performance of our model for proximal femoral segmentation, we measured the volumes of different parts of the proximal femur and compared it with the ground truth, and the relative errors of femur volume between predicted result and ground truth are all less than 5%. This approach will be expected helpful to measure the bone mineral densities of cortical and trabecular bones, and to evaluate the bone strength based on FEA.

Serum levels of C-terminal telopeptide (CTX) are associated with muscle function in community-dwelling older adults

BACKGROUND

Markers of bone metabolism have been associated with muscle mass and function. Whether serum cross-linked C-terminal telopeptides of type I collagen (CTX) is also associated with these measures in older adults remains unknown.

METHODS

In community-dwelling older adults at high risk of falls and fractures, serum CTX (biochemical immunoassays) was used as the exposure, while appendicular lean mass (dual-energy x-ray absorptiometry) and muscle function (grip strength [hydraulic dynamometer], short physical performance battery [SPPB], gait speed, sit to stand, balance, Timed Up and Go [TUG]) were used as outcomes. Potential covariates including demographic, lifestyle and clinical factors were considered in statistical models. Areas under the ROC curves were calculated for significant outcomes.

RESULTS

299 older adults (median age: 79 years, IQR: 73, 84; 75.6% women) were included. In multivariable models, CTX was negatively associated with SPPB (β = 0.95, 95% CI: 0.92, 0.98) and balance (β = 0.92, 0.86, 0.99) scores, and positively associated with sit to stand (β = 1.02, 95% CI: 1.00, 1.05) and TUG (β = 1.03, 95% CI: 1.00, 1.05). Trend line for gait speed (β = 0.99, 95% CI: 0.98, 1.01) was in the hypothesized direction but did not reach significance. AUC curves showed low diagnostic power (<0.7) of CTX in identifying poor muscle function (SPPB: 0.63; sit to stand: 0.64; TUG: 0.61).

CONCLUSION

In older adults, higher CTX levels were associated with poorer lower-limb muscle function (but showed poor diagnostic power for these measures). These clinical data build on the biomedical link between bone and muscle.

Calf Circumference and All-Cause Mortality: A Systematic Review and Meta-Analysis Based on Trend Estimation Approaches

OBJECTIVES

To perform a systematic review and meta-analysis and quantify the associations of total mortality with calf circumference (CC) in adults 18 years and older via combining various analyses based on empirical dichotomic CC, continuous CC, and dose-response CC.

METHODS

We conducted a systematic search of relevant studies in PubMed, EMBASE, Cochrane Library, and Web of Science published through April 12, 2022. This systematic review includes longitudinal observational studies reporting the relationships of total mortality with CC. We calculated the pooled relative risk (RR) and 95% confidence interval (CI) of total mortality with CC per 1 cm for each study and combined the values using standard meta-analysis approaches. Newcastle-Ottawa scale (NOS), Grading of Recommendations, Assessment, Development and Evaluations approach (GRADE), and the Instrument for assessing the Credibility of Effect Modification Analyses (ICEMAN) were assessed for meta-analyses.

RESULTS

Our analysis included a total of 37 cohort studies involving 62,736 participants, across which moderate heterogeneity was observed (I2=75.7%, P<0.001), but no publication bias was found. Study quality scores ranged from 6 to 9 (mean 7.7), with only three studies awarded a score of 6 (fair quality). We observed an inverse trend between total death risk and CC per 1 cm increase (RR, 0.95, 95% CI, 0.94-0.96; P<0.001; GRADE quality=high). Only a very slight difference was found among residents of nursing homes (6.9% mortality risk reduction per one cm CC increase), community-dwellers (5.4%), and those living in hospitals (4.8%), respectively (P for meta-regression=0.617). Low credible subgroup difference was found based on the ICEMAN tool.

CONCLUSIONS

Calf circumference is a valid anthropometric measure for mortality risk prediction in a community, nursing home, or hospital.

Association of Paraspinal Muscle CSA and PDFF Measurements With Lumbar Intervertebral Disk Degeneration in Patients With Chronic Low Back Pain

There is an interaction between the lumbar spine and paraspinal muscles, which may play a role in the development of intervertebral disc (IVD) degeneration and may affect CLBP. The study aims to assess the relationship between IVD degeneration and paraspinal muscle fat infiltration in CLBP patients by quantitative MR imaging, and to evaluate the influence of sex and age on CLBP muscle fat infiltration. Sixty CLBP patients (46.3 years ±17.0) and thirty-two healthy subjects (44.9 years ±17.6) were recruited for this study. 3.0 T MRI was used to perform the sagittal and axial T1, T2 of the lumbar spine, and axial paraspinal muscle IDEAL imaging at the L4/5 and L5/S1 levels. Proton density fat fraction (PDFF) of the multifidus and erector spinae at two IVD levels were measured. The Pfirrmann grades of IVD degeneration, Oswestry Disability Index (ODI), and Visual Analog Scale (VAS) were also evaluated. Compare the cross-sectional area (CSA) and PDFF of the paraspinal muscles between CLBP patients and healthy subjects, and analyze the relationship between the muscle PDFF and Pfirrmann grades, gender, and age of CLBP patients. Compared with healthy subjects, the CSA of the multifidus muscle in CLBP patients decreased (1320.2±188.1mm²vs. 1228.7±191.0 mm², p<0.05) at the L4/5 level, the average PDFF increased, (7.7±2.6% vs. 14.79±5.3%, 8.8±4.2% vs. 16.03±5.3%, all p<0.05) at both L4/5 and L5/S1 levels. The PDFF of paraspinal muscles were correlated with adjacent IVD degeneration, ODI and VSA in CLBP patients (all p<0.05). After using age and body mass index (BMI) as control variables, significance was retained (all p<0.05). Multiple regression analysis revealed sex and age also were significantly associated with multifidus PDFF (all p < 0.05). This study confirmed that the CSA decreased and the PDFF increased of the paraspinal muscles in CLBP patients. It reveals a significant correlation between the PDFF of CLBP paraspinal muscles and the grade of IVD degeneration. Sex and age are also important factors influencing CLBP paraspinal muscle infiltration.

Differences in Muscle Quantity and Quality by HIV Serostatus and Sex

OBJECTIVE

People with HIV (PWH) experience greater declines in both muscle function and muscle mass with aging. Whether changes in muscle quality and quantity with aging differ between men and women with HIV and the implications on muscle function are not established.

DESIGN

In coordinated substudies of the Multicenter AIDS Cohort Study and Women's Interagency HIV Study, participants completed physical function and falls assessments; total trunk/thigh density, inversely related to fatty infiltration, and area were quantified from computed tomography (CT) scans.

METHODS

Generalized linear models were used to explore variables affecting density/area, and associations between area/density and physical function and falls.

RESULTS

CT scans were available on 387 men (198 PWH) and 184 women (118 PWH). HIV serostatus was associated with greater lateralis, paraspinal, and hamstring area, but lower psoas area and density. Older age and female sex were associated with smaller trunk muscle area and lower density. Both lower muscle area and muscle density were associated with several measures of impaired physical function. The odds of falling were lower with greater hamstring density, but not associated with other measurers of muscle area or density.

CONCLUSIONS

In summary, older adults with HIV appear to have smaller and less dense (fattier) psoas, a key component in truncal stability and hip flexion that could have implications on physical function. The longitudinal associations of muscle area and density with physical function require careful investigation, with a particular focus on characteristics and interventions that can preserve muscle area, density, and function over time.

Associations of muscle size and fatty infiltration with bone mineral density of the proximal femur bone

PURPOSE

To investigate the relationship of muscle atrophy and fat infiltration around the hip joint with areal bone mineral density (aBMD) in each subregion of the proximal femur.

MATERIALS AND METHODS

In total, 144 participants (66 women and 78 men) were examined by quantitative computed tomography (QCT), and areal bone mineral density (aBMD) of the femoral neck (FN), trochanter (TR), and intertrochanter (IT) of the proximal femur were obtained. The cross-sectional area (CSA) and proton density fat fraction (PDFF) of the gluteus maximus (G.MaxM), gluteus medius (G.MedM), gluteus minimus (G.MinM), and iliopsoas (IliopM) were obtained via magnetic resonance imaging (MRI) using the mDIXON-Quant sequence. A multivariate generalized linear model was used to evaluate the correlation of the CSA and PDFF of muscles with aBMD in all subregions of the proximal femur.

RESULTS

The FN integral (Int) aBMD was significantly associated with the G.MaxM CSA (men: P = 0.002; women: P = 0.008) and PDFF (men: P < 0.001; women: P = 0.047). Some muscle indexes were related to the FN aBMD in males or females, including the CSA of G.MedM, G.MinM, and IliopM as well as the PDFF of IliopM and G.MinM. Associations of hip muscle parameters with the TR Int aBMD in both males and females were observed, including G.MaxM CSA (men: P < 0.001; women: P = 0.028) and G.MaxM PDFF (men: P = 0.031; women: P = 0.038). Other muscle indexes, including G.MedM and IliopM, were related to the TR aBMD, mainly affecting the aBMD of TR cortical (Cort) and TR Int. The IT Int aBMD and IT Cort aBMD showed significant correlation with the muscle indexes of G. MaxM, IliopM, and G.MedM, including the PDFF and CSA in males and females. Further, more indicators of the G.MedM and IliopM correlated with the TR and IT aBMD compared to the FN aBMD.

CONCLUSIONS

The CSA of gluteus muscles and iliopsoas had a positive association with the aBMD in the proximal femur, and the PDFF of gluteus muscles and iliopsoas had a negative correlation with the aBMD in the proximal femur. In addition, there was an interaction of the proximal femur aBMD with the muscle size and fatty infiltration of hip muscles.

Accelerated loss of trunk muscle density and size at L1 vertebral level in male patients with COPD

BACKGROUND AND PURPOSE

Weight loss and muscle mass loss are common in patients with chronic obstructive pulmonary disease (COPD). Muscle density and fat infiltration based on CT images may be more sensitive than muscle mass by DXA in the assessment of sarcopenia for COPD patients. However, the age-related changes of cross-sectional trunk muscle compositions based on lung CT scans are still unknown. Thus, we aimed to investigate over time the change in muscle density, size, and fat deposition of L1-level trunk muscles in patients with COPD.

MATERIALS AND METHODS

129 male COPD patients with a second chest CT scan (from 2013-2019 to 2014-2020) were enrolled. The CT images at first and second CT scans are analyzed by OsiriX software. Trunk muscles at the level of the 1st lumbar vertebrae were selected for analysis. Attenuation of lumbar vertebrae 1 was also measured from chest CT images. The pulmonary function values were calculated based on forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC).

RESULTS

The mean age of the 129 patients with COPD was 69.7 years. The durations of COPD of this cohort were from 8-17 years. The mean area and density of L1 trunk muscles were 85.5 cm² and 36.4 HU. At baseline, muscle area and density and vertebral density were negatively associated with age (p<0.0001), while the intermuscular fat area and the fat infiltration ratio were not significantly associated with age (p>0.05). The per-year loss of trunk muscle area was 2.83 cm² (p<0.0001) which accounts for 3.3% decrease per year, and the per-year decrease of trunk muscle density was 2.41 HU (p<0.0001) which accounts for 6.6% decrease per year. The per-year increase of intermuscular fat in trunk muscles was 0.57 cm² (p=0.006) which accounts for 11.1% increase per year. The bone density loss was 5.63 HU/per year (p<0.0001).

CONCLUSION

Men with COPD had accelerated muscle loss as well as increased fat infiltration. Compared to muscle quantity loss, the decline in muscle quality is much larger, indicating the importance of relevant interventions focusing on improving muscle quality.

Quantification of lumbar vertebral fat deposition: Correlation with menopausal status, non-alcoholic fatty liver disease and subcutaneous adipose tissue

PURPOSE

To assess abdominal fat deposition and lumbar vertebra with iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL-IQ) and investigate their correlation with menopausal status.

MATERIALS AND METHODS

Two hundred forty women who underwent routine abdominal MRI and IDEAL-IQ between January 2016 and April 2021 were divided into two cohorts (first cohort: 120 pre- or postmenopausal women with severe fatty livers or without fatty livers; second cohort: 120 pre- or postmenopausal women who were obese or normal weight). The fat fraction (FF) values of the liver (FF_liver) and lumbar vertebra (FF_lumbar) in the first group and the FF values of subcutaneous adipose tissue (SAT) (FF_SAT) and FF_lumbar in the second group were measured and compared using IDEAL-IQ.

RESULTS

Two hundred forty women were evaluated. FF_lumbar was significantly higher in both pre- and postmenopausal women with severe fatty liver than in patients without fatty livers (premenopausal women: p < 0.001, postmenopausal women: p < 0.001). No significant difference in the FF_lumbar was observed between obese patients and normal-weight patients among pre- and postmenopausal women (premenopausal women: p = 0.113, postmenopausal women: p = 0.092). Significantly greater lumbar fat deposition was observed in postmenopausal women than in premenopausal women with or without fatty liver and obesity (p < 0.001 for each group). A high correlation was detected between FF_liver and FF_lumbar in women with severe fatty liver (premenopausal women: r=0.76, p<0.01; postmenopausal women: r=0.82, p<0.01).

CONCLUSION

Fat deposition in the vertebral marrow was significantly associated with liver fat deposition in postmenopausal women.

Association Between the Growth Hormone/Insulin-Like Growth Factor-1 Axis and Muscle Density in Children and Adolescents of Short Stature

OBJECTIVE

To evaluate the association between the growth hormone (GH)/insulin-like growth factor-1 (IGF-1) axis and muscle density in children and adolescents of short stature.

METHODS

Participants were children and adolescents of short stature hospitalized in the Affiliated Hospital of Jining Medical University between January 2020 and June 2021. All participants had CT scan images available. We performed an analysis of the images to calculate the muscle density or skeletal muscle attenuation (SMA), skeletal muscle index (SMI), and fat mass index (FMI). Bioelectrical impedance analysis (BIA) was used to ensure that chest CT is a credible way of evaluating body composition.

RESULTS

A total of 297 subjects were included with the mean age of 10.00 ± 3.42 years, mean height standard deviation score (SDS) of -2.51 ± 0.53, and mean IGF-1 SDS of -0.60 ± 1.07. The areas of muscle and fat tissues at the fourth thoracic vertebra level in the CT images showed strong correlation with the total weights of the participants (R²  = 0.884 and 0.897, respectively). The peak of GH was negatively associated with FMI (r = - 0.323, P <.01) and IGF-1 SDS was positively associated with SMI (r = 0.303, P <.01). Both the peak GH and IGF-1 SDS were positively associated with SMA (r = 0.244, P <.01 and r = 0.165, P <.05, respectively). Multiple stepwise linear regression analysis demonstrated that the GH peak was the predictor of FMI (β = - 0.210, P < .01), the IGF-1 SDS was the predictor of SMI (β = 0.224, P < .01), and both the peak GH and IGF-1 SDS were predictors of SMA (β = 0.180, P < .01 and β = 0.222, P < .01).

CONCLUSIONS

A chest CT scan is a credible method of evaluating body composition in children and adolescents of short stature. In these patients, peak GH and IGF-1 SDS are independent predictors of muscle density and the GF/IGF-1 axis may regulate body composition through complex mechanisms.

Differences in Hip Geometry Between Female Subjects With and Without Acute Hip Fracture: A Cross-Sectional Case-Control Study

BACKGROUND AND PURPOSE

Although it is widely recognized that hip BMD is reduced in patients with hip fracture, the differences in geometrical parameters such as cortical volume and thickness between subjects with and without hip fracture are less well known.

MATERIALS AND METHODS

Five hundred and sixty two community-dwelling elderly women with hip CT scans were included in this cross-sectional study, of whom 236 had an acute hip fracture. 326 age matched women without hip fracture served as controls. MIAF-Femur software was used for the measurement of the intact contralateral femur in patients with hip fracture and the left femur of the controls. Integral and cortical volumes (Vols) of the total hip (TH), femoral head (FH), femoral neck (FN), trochanter (TR) and intertrochanter (IT) were analyzed. In the FH and FN the volumes were further subdivided into superior anterior (SA) and posterior (SP) as well as inferior anterior (IA) and posterior (IP) quadrants. Cortical thickness (CortThick) was determined for all sub volumes of interest (VOIs) listed above.

RESULTS

The average age of the control and fracture groups was 71.7 and 72.0 years, respectively. The fracture patients had significantly lower CortThick and Vol of all VOIs except for TRVol. In the fracture patients, cortical thickness and volume at the FN were significantly lower in all quadrants except for cortical volume of quadrant SA (p= 0.635). Hip fracture patients had smaller integral FN volume and cross-sectional area (CSA) before and after adjustment of age, height and weight. With respect to hip fracture discrimination, cortical volume performed poorer than cortical thickness across the whole proximal femur. The ratio of Cort/TrabMass (RCTM), a measure of the internal distribution of bone, performed better than cortical thickness in discriminating hip fracture risk. The highest area under curve (AUC) value of 0.805 was obtained for the model that included THCortThick, FHVol, THRCTM and FNCSA.

CONCLUSION

There were substantial differences in total and cortical volume as well as cortical thickness between fractured and unfractured women across the proximal femur. A combination of geometric variables resulted in similar discrimination power for hip fracture risk as aBMD.

CT muscle density, D3Cr muscle mass and body fat associations with physical performance, mobility outcomes and mortality risk in older men

BACKGROUND

Muscle mass declines with age, while body adiposity increases. Sarcopenic obesity has been proposed to be particularly deleterious. However, previous methods for estimating muscle mass have been inadequate, and the relative contributions of total body fat vs. muscle fat to adverse outcomes have been unclear.

METHODS

In a large cohort of older men (N= 1017), we measured muscle mass (D3 creatine dilution), muscle density (high resolution peripheral computed tomography in the diaphyseal tibia) as a proxy of muscle fat, and total body fat (dual energy x-ray absorptiometry). We examined their associations with physical performance (walking speed, grip strength, chair stand time), the risk of mobility outcomes (mobility limitations, mobility disability), and the risk of death over ~5 years.

RESULTS

In combined models, lower muscle mass and muscle density were independently associated with worse physical performance and the risk of adverse outcomes, while total body fat was minimally related to physical performance and not related to mobility outcomes or mortality. For example, the relative risks for mortality per 1 standardized unit increase in muscle density, muscle mass, and total body fat were 0.84 (95% CI: 0.74, 0.70), 0.70 (0.57, 0.86), and 0.90 (0.64, 1.25), respectively.

CONCLUSIONS

Muscle mass and muscle density were associated with physical performance and adverse outcomes, and had independent, additive effects. There was little additional contribution of total body fat.

Comparison of Muscle Density in Middle-Aged and Older Chinese Adults Between a High-Altitude Area (Kunming) and a Low-Altitude Area (Beijing)

BACKGROUND AND PURPOSE

A high-altitude environment was known to have a negative effect on bone and lead to a higher incidence of hip fracture. However, the dependence of muscle composition on altitude is unclear. Thus, we aimed to compare muscle density and area in plateau and low altitude area and to determine the effect of the altitude on these outcomes.

METHODS

Community dwelling adults over 60 years old living in Beijing (elevation 50 m; 300 subjects,107 men and 193 women) or Kunming (elevation 2000 m; 218 subjects,83 men and 135 women) for more than 10 years were enrolled. Quantitative CT was performed in all subjects and cross-sectional area and attenuation measured in Hounsfield units (HU) were determined for the trunk, gluteus, and mid-thigh muscles.

RESULTS

Compared to Beijing, Kunming adults were slimmer (Beijing men vs Kunming men: 25.08 ± 2.62 vs 23.94 ± 3.10kg/m², P=0.013; Beijing women vs Kunming women: 25.31 ± 3.1 vs 23.98 ± 3.54 kg/m², P= 0.001) and had higher muscle density in the L2-trunk and gluteus maximus muscles after adjustment for age and BMI (L2-trunk muscles: Beijing men 29.99 ± 4.17 HU vs Kunming men 37.35 ± 4.25 HU, P< 0.0001; Beijing women 27.37 ± 3.76 HU vs Kunming women 31.51 ± 5.12 HU, P< 0.0001; Gluteus maximus muscle: Beijing men 35.11 ± 6.54 HU vs Kunming men 39.36 ± 4.39 HU, P= 0.0009; Beijing women 31.47 ± 6.26 HU vs Kunming women 34.20 ± 5.87 HU P=0.0375). Age was similar in both cohorts and no differences were observed in the gluteus medius and minimus muscle or the mid-thigh muscle, either in the area or density.

CONCLUSIONS

Compared with Beijing, the adults in Kunming had higher muscle density of the gluteus maximus and L2 trunk muscles, showing that living at a higher altitude might be beneficial to muscle quality.

Muscle density discriminates hip fracture better than computed tomography X-ray absorptiometry hip areal bone mineral density

BACKGROUND

Muscle weakness is a key factor in the increase risk of falls and might also play a significant role in the increase of risk of hip fracture. Computed tomography-measured muscle size and muscle density are well-established imaging biomarkers used in studies of physical function, frailty or cancer, but limited to hip fracture. In particular, it is warranted to have a better understanding of the performance of muscle size and density in the discrimination of acute hip fractures. We also aim to determine age-related differences of muscle size and density in healthy controls and hip fracture patients.

METHODS

Four hundred thirty-eight low-energy acute hip fracture cases and 316 healthy controls from the China Action on Spine and Hip Status study were included in the study. Muscle cross-sectional area and density were measured for the gluteus maximus and gluteus medius and minimus. Areal bone mineral density (aBMD) of the femoral neck and total hip was measured. Using propensity score matching, we generated three samples with cases and controls matched for age, body mass index, and gender: femoral neck fracture (FNF), intertrochanteric fracture (ITF), and any hip fracture vs. controls, respectively.

RESULTS

Handgrip strength, gluteus muscle area and density, and bone parameters of the matched hip fracture groups were lower than those of the correspondence control groups, respectively (P < 0.05). The univariate analysis showed that associations of aBMD with FNF and with ITF were significantly weaker than associations between fracture and muscle parameters. Gluteus medius and minimus muscle density showed the highest areas under the curve (AUC) with FNF (0.88, 95% confidence interval, 0.85-0.92) and trochanteric fracture (0.95, 95% confidence interval, 0.92-0.97). The model including all muscle and bone parameters provided the highest AUC (FNF: AUC 0.912; ITF: AUC 0.958), and AUC results of another selected model without muscle density showed that association with fracture significantly dropped (FNF: AUC 0.755; ITF: AUC 0.858). Separate results for the two age groups younger and older than 70 years showed no age-related significant differences in discriminate models.

CONCLUSIONS

Muscle density performs better than aBMD from hip computed tomography X-ray absorptiometry and muscle size in discrimination of hip fracture. Combination of aBMD and muscle density provided the best discrimination. The integration of muscle assessments may trigger a paradigm shift in hip fracture prediction. Gluteus muscle density should also be evaluated as treatment outcome.