Opportunistic use of dual-energy X-ray absorptiometry to evaluate lumbar scoliosis

Low bone mineral density is associated with spinal deformity. Dual-energy X-ray absorptiometry (DXA), a modality that assesses bone density, portends a theoretical means to also assess spinal deformity. We found that DXA can reliably assess spine alignment. DXA may permit surveillance of spine alignment, i.e., scoliosis in the clinical setting.

PURPOSE

Osteoporosis and scoliosis are interrelated disease processes. Dual-energy X-ray absorptiometry (DXA), used to assess bone density, can also be used to evaluate spinal deformity since it captures a posteroanterior (PA) image of the lumbar spine. We assessed the use of DXA to evaluate lumbar spine alignment.

METHODS

A lumbar spine DXA phantom was used to assess the effects of axial and sagittal plane rotation on lumbar bone mineral content (BMC), density (BMD), and L1-L4 Cobb angle measurements. Using two subject cohorts, intra- and inter-observer reliability and validity of using DXA for L1-L4 Cobb angle measurements in the coronal and sagittal planes were assessed.

RESULTS

Axial and sagittal plane rotation greater than 15° and 10°, respectively, significantly reduced measured BMD and BMC; there was minimal effect on Cobb angle measurement reliability. In human subjects, excellent intra- and inter-observer reliability was observed using lumbar PA DXA images for Cobb angle measurements. Agreement between Cobb angles derived from lumbar PA DXA images and AP lumbar radiographs ranged from good to excellent. The mean difference in Cobb angles between supine lumbar PA DXA images and upright AP lumbar radiographs was 2.8° in all subjects and 5.8° in those with scoliosis.

CONCLUSIONS

Lumbar spine rotation does not significantly affect BMD and BMC within 15° and 10° of axial and sagittal plane rotation, respectively, and minimally affects Cobb angle measurement. Spine alignment in the coronal plane can be reliably assessed using lumbar PA DXA images.

A probable atypical ulnar fracture in a man receiving denosumab

BACKGROUND

Atypical femur fractures are widely recognized and associated with anti-resorptive therapy, most commonly bisphosphonates. These fractures generally occur in the femoral shaft or subtrochanteric region. Cases of atypical fractures at non-femur sites, including the ulna, have been reported.

CASE REPORT

Here we report a probable atypical ulnar fracture in a man receiving denosumab, who had been using his upper extremities for transfers and ambulation. Radiographs demonstrated a non-comminuted, transverse fracture somewhat similar to findings of atypical femur fractures. He was deemed a poor surgical candidate and treated with teriparatide. To our knowledge, this is the first reported probable atypical ulnar fracture potentially associated with denosumab use.

CONCLUSION

We believe it important that clinicians be aware of the association of anti-resorptive therapy with atypical fractures not only of the femur, but also at other skeletal sites. In patients on long-term anti-resorptive therapy, it is appropriate to consider that persistent "prodromal" pain might indicate an impending atypical fracture at an atypical skeletal site.

An Exploratory Study of the Texture Research Investigational Platform (TRIP) to Evaluate Bone Texture Score of Distal Femur DXA Scans - A TBS-Based Approach

Poor bone status is associated with increased complications following orthopedic surgery. Therefore, assessing site-specific skeletal status prior to or after orthopedic surgery to optimize outcomes is appealing. The trabecular bone score (TBS) approach, a surrogate for microarchitecture, was adapted to the Texture Research Investigational Platform (TRIP), which allows assessment of many skeletal sites imaged by various modalities. TRIP generates a bone texture score (TBS ORTHO), which could potentially guide surgical decision-making and offer insight into postsurgical fracture risk. As distal femur bone loss occurs following total knee arthroplasty (TKA), we hypothesized that TBS ORTHO after TKA would identify poorer texture in the operated femur compared to the nonoperated. We evaluated 30 subjects (15 M/15 F) with unilateral TKA 2-5 yr previously, mean age 67.9 yr and body mass index 30 kg/m². Using a Lunar iDXA, lumbar spine and entire femur scans were obtained, the latter using the atypical femur fracture feature. Distal femur bone mineral density (BMD) and TBS ORTHO were obtained using manual regions of interest (ROI) at 15% and 25% of leg length from the intercondylar notch. TBS ORTHO was determined using distal femur DICOM images and TRIP v1.0 (Medimaps, France). Differences in operated vs nonoperated femur were evaluated by paired t test. As previously reported, operated leg BMD was approx 10% lower at 15% and 25% ROIs. Similarly, TBS ORTHO values in the operated leg were approx 5% lower (p < 0.05) at these same ROIs. Distal femur TBS ORTHO and BMD were largely unrelated. TBS ORTHO reproducibility at these ROIs was approx 3.5%. In conclusion, this pilot study documents the feasibility of reproducibly obtaining distal femur TBS ORTHO values. Lower values were observed in the surgical leg, consistent with the bone loss that follows TKA. Further work is indicated to refine TRIP use and evaluate whether such data provides guidance for surgical decision-making and improves periprosthetic fracture prediction.

"Effect of very dense artifacts on Hologic and general electric bone densitometry results"

Very dense artifacts confound bone density measurement. Hologic and GE densitometers exclude artifact density and GE also excludes associated area. Consequently, BMD is decreased with Hologic software. Despite different manufacturers' approaches, when dense artifacts overlay the spine, the affected vertebral body should be excluded from the reported BMD.

PURPOSE

Very dense objects, such as lead bullets are described as "black hole" artifacts on Hologic densitometers. Whether similar results occur on GE scanners is not reported. We hypothesized that dense artifacts confound both brands of densitometers.

METHODS

Three lead bullets of varying size were placed overlying or adjacent to L3 on anthropomorphic and encapsulated aluminum spine phantoms. Three scans were acquired with and without projectiles on a Hologic Discovery W, GE iDXA, and Prodigy densitometer.

RESULTS

Lead bullets are measured as having high bone mineral content (BMC); they appear black in dual-energy mode on Hologic scanners and are colored blue on GE scanners. On Hologic scanners, BMC of a dense artifact over bone is excluded, but the bone area is not altered. Consequently, bone mineral density (BMD) of the affected vertebra, and of L1-4, is decreased. For example, a .45 caliber bullet over L3 decreased BMD (p < 0.05) by 48.3% and L1-4 by 9.1%. GE scanners excluded associated BMC and area covered by the artifact, thereby minimizing impact on BMD. Dense artifacts over soft tissue on a phantom do not substantially affect BMD on either manufacturer's densitometer when scanned.

CONCLUSION

Densitometer manufacturers handle very dense artifacts differently. GE software removes artifact BMC and area with resultant minimal impact on BMD, Hologic removes only BMC, not area, thereby decreasing BMD. Regardless of this difference, when dense artifacts overlay the spine, it is best to exclude the affected vertebral body. Finally, the BMD stability observed with artifacts over soft tissue may not be replicated in humans.

Do patients that fracture with normal DXA-measured BMD have normal bone?

Patients that sustain "osteoporosis-related" fractures may have normal BMD at the hips and spine, but rarely have normal bone when other clinically available studies are considered. Such data often exist and can inform clinical decisions regarding osteoporosis therapy.

PURPOSE

Dual-energy X-ray absorptiometry (DXA) measured bone mineral density (BMD) at the hip and spine is widely used to diagnose osteoporosis. However, patients that sustain "osteoporosis-related" fractures often have normal BMD at these sites. The aim of this study was to explore whether older adults with fracture, but normal reported hip and spine BMD, also have normal bone using additional clinically available assessments.

METHODS

This retrospective electronic medical record study included 387 patients evaluated by a university-based fracture liaison service with spine and hip DXA; 32 (8.3%) had normal spine/hip BMD reported. In this cohort, clinically available bone data including 0.3 and ultradistal radius T-scores, trochanteric T-scores, lumbar spine trabecular bone score (TBS), L1 opportunistic CT Hounsfield units (HU), and femoral cortical index (FCI) were assessed.

RESULTS

One or more of the above noted studies were available in 30/32 patients. UD and 0.3 radius results were available in 21 patients, and 18 (85.7%) had T-scores < - 1.0. Trochanteric values were available in 16; T-scores were < - 1.0 in 18.8%. TBS data were available in 24; partially degraded or degraded values were present in 41.7%. L1 opportunistic CT was available in 25 patients, 80% were below normal, and < 150 HU. Finally, femoral cortical index (FCI) was measurable in 9 subjects; 66.7% were below < 0.4. When including all additional available data in the skeletal assessment, only 5/387 (1.3%) were identified with normal bone.

CONCLUSION

Patients with normal spine/hip BMD who sustain fracture rarely have normal bone when all available data are considered.

Determination of D-Malic Acid in Apple Juice by Liquid Chromatography: Collaborative Study

Eleven laboratories collaboratively studied a liquid chromatographic (LC) method for determination of D-malic acid in apple juice. The mobile phase consisted of 16 mM L-valine and 8 mM copper acetate adjusted to pH 5.5 with NaOH. The UV detector was set at 330 nm, and a single reversed-phase LC column was used. Seven paired samples containing various amounts of D-malic acid ranging from 0 to 188 mg/100 mL of 12 Brix pasteurized apple juice were tested by each collaborator. Repeatability and reproducibility coefficients of variation ranged from 1.0 to 3.5% and 7.7 to 11.7%, respectively, within the range of 26 to 188 mg D-malic acid/100 mL of 12 Brix apple juice. The collabora tive study results demonstrated that the method could quantitate the economic adulteration of ap ple juice with DL-malic acid at lower levels than those reported with previous methods. The LC method for determination of D-malic acid in apple juice has been adopted first action by AOAC INTERNATIONAL.

Determination of Vitamins A (Retinol) and E (alpha-Tocopherol) in Foods by Liquid Chromatography: Collaborative Study

A collaborative study was conducted for the determination of vitamins A and E. Existing AOAC liquid chromatographic (LC) methods are suited for specific vitamins A and E analytical applications. This method differs from existing methods in that it can be used to assay samples in all 9 sectors of the food matrix. Standards and test samples are saponified in basic ethanol–water solution, neutralized, and diluted, converting fats to fatty acids and retinol esters and tocopherol esters to retinol and tocopherol, respectively. Retinol and alpha-tocopherol are quantitated on separate LC systems, using UV detection at 313 or 328 nm for retinol, and fluorescence detection (excitation 290 nm, emission 330 nm) for alpha-tocopherol. Vitamin concentrations are calculated by comparison of the peak heights or peak areas of vitamins in test samples with those of standards.

Determination of Naringin and Neohesperidin in Orange Juice by Liquid Chromatography with UV Detection to Detect the Presence of Grapefruit Juice: Collaborative Study

Fifteen collaborating laboratories were sent 9 samples of citrus juice mixtures as blind duplicates for determination of naringin and neohesperidin by liquid chromatography. Two sample pairs were 100% orange juice and did not contain any naringin or neohesperidin. The remaining 7 sample pairs contained naringin at levels ranging from 3.9 to 46.5 ppm and neohesperidin at levels ranging from 0.14 to 35.6 ppm. Five sample pairs consisted of orange juice mixtures containing 1, 3, and 5% grapefruit juice; 5% sour orange; and 5% K-Early citrus variety. Two sample pairs were orange juice spiked with naringin, neohesperidin, sodium benzoate, and potassium sorbate. Data were received from 13 laboratories. Data from 1 collaborator were eliminated because the method protocol was not followed. Neohesperidin values from another laboratory were also not used because of problems with a coeluting component. Repeatability relative standard deviations ranged from 2.95 to 15.23% for naringin and from 3.00 to 11.74% for neohesperidin. Reproducibility relative standard deviations ranged from 11.34 to 31.94% for naringin and from 10.45 to 26.17% for neohesperidin. The method is reliable for detecting the presence of grapefruit juice in orange juice as indicated by a finding of ≥10 ppm naringin and ≤2 ppm neohesperidin. The method was adopted First Action by AOAC INTERNATIONAL.

Semi-Recumbent Vibration Exercise in Older Adults: A Pilot Study of Methodology, Feasibility, and Safety

Objectives:

Older adults with impaired physical function are at risk for further functional decline in part due to limited ability to engage in regular exercise. Effective approaches to exercise in this vulnerable population are needed to improve functional capacity and optimize independence.

Methods:

Thirty-two residential care apartment complex (RCAC) residents, age ≥70, with low short physical performance battery (SPPB) scores were recruited and randomly assigned to a crossover-design study exploring feasibility and safety of semi-recumbent vibration exercise in older adults living in one RCAC. The primary outcomes were retention and adherence rates and adverse events.

Results:

The retention rate was 78%. Adherence rate was 79.7% and 78.6% during the vibration and control training sessions, respectively. Thirty-eight adverse events (AEs) occurred. Mild muscle soreness and knee pain were the only AEs related to vibration exercise. No serious adverse events (SAEs) were study-related. Participants were able to increase training intensity and load and rated the training enjoyable.

Conclusion:

Semi-recumbent vibration exercise was feasible, well tolerated, and safe in RCAC residents with reduced physical function. Future studies need to examine the effect of this type of exercise on physical function, mobility, falls, and quality of life.

Use of Bone Health Evaluation in Orthopedic Surgery: 2019 ISCD Official Position

This position development conference (PDC) Task Force examined the assessment of bone status in orthopedic surgery patients. Key questions included which orthopedic surgery patients should be evaluated for poor bone health prior to surgery and which subsets of patients are at high risk for poor bone health and adverse outcomes. Second, the reliability and validity of using bone densitometry techniques and measurement of specific geometries around the hip and knee before and after arthroplasty was determined. Finally, the use of computed tomography (CT) attenuation coefficients (Hounsfield units) to estimate bone quality at anatomic locations where orthopedic surgery is performed including femur, tibia, shoulder, wrist, and ankle were reviewed. The literature review identified 665 articles of which 198 met inclusion exclusion criteria and were selected based on reporting of methodology, reliability, or validity results. We recommend that the orthopedic surgeon be aware of established ISCD guidelines for determining who should have additional screening for osteoporosis. Patients with inflammatory arthritis, chronic corticosteroid use, chronic renal disease, and those with history of fracture after age 50 are at high risk of osteoporosis and adverse events from surgery and should have dual energy X-ray absorptiometry (DXA) screening before surgery. In addition to standard DXA, bone mineral density (BMD) measurement along the femur and proximal tibia is reliable and valid around implants and can provide valuable information regarding bone remodeling and identification of loosening. Attention to positioning, selection of regions of interest, and use of special techniques and software is required. Plain radiographs and CT provide simple, reliable methods to classify the shape of the proximal femur and to predict osteoporosis; these include the Dorr Classification, Cortical Index, and critical thickness. Correlation of these indices to central BMD is moderate to good. Many patients undergoing orthopedic surgery have had preoperative CT which can be utilized to assess regional quality of bone. The simplest method available on most picture archiving and communications systems is to simply measure a regions of interest and determine the mean Hounsfield units. This method has excellent reliability throughout the skeleton and has moderate correlation to DXA based on BMD. The prediction of outcome and correlation to mechanical strength of fixation of a screw or implant is unknown.

Dual-Energy X-Ray Absorptiometry Body Composition in NCAA Division I Athletes: Exploration of Mass Distribution

BACKGROUND

Body composition assessment is frequently used in sports medicine and athletic performance environments to assess change in response to strength training and nutrition programs. However, to effectively do so requires knowledge regarding expected body composition values relative to sport and sex. Dual-energy x-ray absorptiometry (DXA) is widely used to evaluate body composition, although its utility in relationship to specific sports, performance, or rehabilitation is not clearly defined.

HYPOTHESIS

Body composition metrics and distribution of National Collegiate Athletic Association Division I collegiate athletes will vary based on sport and sex.

LEVEL OF EVIDENCE

Level 4.

STUDY DESIGN

Cross-sectional study.

METHODS

A convenience sample of 337 athletes (229 men and 108 women) participating in football, wrestling, soccer, hockey, basketball, golf, softball, or volleyball was evaluated. DXA-measured total body composition, including bone mineral density (BMD), % lean mass, % fat, and regional distribution, were compared by sex, sport, and with an age-matched National Health and Nutrition Examination Survey (NHANES) population.

RESULTS

Men had higher BMD, lower % fat (16.4% vs 25.2%) and higher % lean mass (79.2% vs 70.6%) (P < 0.001). Regional composition varied by sport and sex, with women having a greater proportion of lean mass at the trunk and men in their arms (P < 0.0001). Leg lean mass was distributed similarly between sexes (35%). Overall, the normative group (NHANES) had lower BMD and higher percentage fat.

CONCLUSION

DXA-measured body composition and lean mass distribution varies by sport and sex in Division I athletes. The observed difference to the NHANES population emphasizes challenges in identifying appropriate comparison populations, reinforcing the need to compare athletes with their own baseline.

CLINICAL RELEVANCE

These findings establish a framework to investigate the relevance of these variances and determine the utility of body composition analysis in elite athletes.

DXA evaluation of femoral bone mineral density and cortical width in patients with prior total knee arthroplasty

Periprosthetic fractures after total knee arthroplasty (TKA) have devastating consequences. Osteoporosis increases periprosthetic fracture risk, but distal femur bone mineral density (BMD) is not measured post-TKA. This study measured distal femur BMD and cortical width; both were lower in the TKA compared to the non-operated leg. BMD measurement reproducibility was good. Standardized DXA regions of interest are proposed.

INTRODUCTION

Periprosthetic fractures following total knee arthroplasty (TKA) are not rare. We hypothesized that TKA is associated with low BMD, potentially increasing periprosthetic fracture risk. However, distal femur dual energy x-ray (DXA) measurement is virtually never performed after TKA due to lack of standardized approaches. Thus, this study's aims were to develop standard DXA femur regions of interest (ROIs), assess cortical width, and determine measurement reproducibility in TKA patients.

METHODS

Thirty adults (15 M/15 F) age 59-80 years with unilateral, primary TKA within 2-5 years had femoral DXA scans performed in duplicate using a Lunar iDXA densitometer. In prior work, we established that femur BMD was lowest in the distal metaphysis and highest in mid-shaft. Thus, BMD and cortical width were measured at 15%, 25%, and 60% of the femur length measured from the distal notch. Femur BMD and cortical width were compared between limbs (TKA vs. non-operated side) by paired t test.

RESULTS

BMD was 3.2-9.9% lower (p < 0.001) in the operated femur at all custom ROIs; substantial between individual differences existed with some up to 30% lower. Cortical width was lower (p < 0.05) at the 25% ROI on the TKA side. BMD reproducibility was excellent; CV 0.85-1.33%.

CONCLUSIONS

Distal femur BMD can be reproducibly measured using DXA and is ~ 10% lower on the TKA leg. Similarly, medial and lateral cortices are thinner at the 25% ROI. These bone changes likely increase periprosthetic fracture risk. Further work to define and mitigate periprosthetic fracture risk after TKA is needed.

DXA Measured Distal Femur Bone Mineral Density in Patients After Total Knee Arthroplasty: Method Development and Reproducibility

INTRODUCTION

Total knee arthroplasty (TKA) is increasingly being performed. Distal femur periprosthetic fracture is a potentially catastrophic complication following TKA and existing data document substantial distal femur bone mineral density (BMD) loss following TKA. However, distal femur BMD is virtually never measured clinically as no consensus approach exists. This pilot study's purpose was to define regional BMD variation throughout the femur, suggest standard dual-energy X-ray absorptiometry (DXA) regions of interest (ROIs) and evaluate BMD reproducibility at these ROIs.

METHODS

Thirty volunteers 2-5 yr post TKA had both entire femurs imaged twice using a Lunar iDXA with subject repositioning between scans; the atypical femur fracture feature of enCORE software was utilized. To define femoral BMD distribution, custom 1 cm ROIs were stacked one atop the other starting at the intercondylar notch and continuing to the base of the lesser trochanter. Femur length was measured with the ruler tool to calculate distance at 5% increments. ROIs encompassing each 5% increment were utilized to measure BMD at each location. Descriptive statistics were used to determine mean BMD at each ROI and reproducibility at the 15%, 25%, 45%, 60%, and 80% ROIs.

RESULTS

The 5 and 10% ROIs included prosthetic and/or patella, causing high BMD values. Distal femur BMD was lowest at the 15% ROI and was higher (p < 0.05) at each more proximal ROI to 45%, then plateaued from 45% to 75%. BMD reproducibility at these regions was excellent; coefficient of variation (CV) from ∼1% to 3.5%. As periprosthetic fractures generally occur in the distal femur, we propose measuring femur BMD using ROIs placed at 15% and 25%. A 60% region could also be used as a highly cortical site.

CONCLUSION

Existing DXA capabilities allow distal femur BMD measurement with good reproducibility. Further research using standardized ROIs to assess distal femur BMD loss after TKA, and interventions to mitigate this loss, is indicated.

DXA Errors Are Common and Reduced by Use of a Reporting Template

OBJECTIVE

High quality dual energy X-ray absorptiometry (DXA) acquisition, analysis, and reporting demands technical and interpretive excellence. We hypothesized that DXA errors are common and of such magnitude that incorrect clinical decisions might result. In this 2-phase study, we evaluated DXA technical and interpretation error rates in a clinical population and subsequently assessed if implementing an interpretation template reduced errors.

METHODS

In phase 1, DXA scans of 345 osteoporosis clinic referrals were reviewed by International Society for Clinical Densitometry-certified technologists (n = 3) and physicians (n = 3). Technologists applied International Society for Clinical Densitometry performance standards to assess technical quality. Physicians assessed reporting compliance with published guidance, relevance of technical errors and determined overall and major error prevalence. Major errors were defined as "provision of inaccurate information that could potentially lead to incorrect patient care decisions." In phase 2, a DXA reporting template was implemented at 2 clinical DXA sites after which the 3 physicians reviewed 200 images and reports as above. The error prevalence was compared with the 298 patients in phase 1 from these sites.

RESULTS

In phase 1, technical errors were identified in 90% of patients and affected interpretation in 13%. Interpretation errors were present in 80% of patients; 42% were major. The most common major errors were reporting incorrect information on bone mineral density change (70%) and incorrect diagnosis (22%). In phase 2, at these 2 clinical sites, major errors were present in 37% before and 17% after template implementation. Template usage reduced the odds of major error by 66% (odds ratio 0.34, 95% confidence interval 0.21, 0.53, and p < 0.0001).

CONCLUSION

DXA technical and interpretation errors are extremely common and likely adversely affect patient care. Implementing a DXA reporting template reduces major errors and should become common practice. Additional interventions, such as requiring initial and ongoing training and/or certification for technologists and interpreters, are suggested.

Effect of vertebral exclusion on TBS and FRAX calculations

Degenerative changes falsely elevate BMD; however, their impact on TBS is unclear. This study examined how spinal degenerative changes affect TBS-adjusted fracture risk (FRAX). In a majority, but not all patients in this sample, TBS decreased after exclusion of vertebrae with degenerative change. Therefore, vertebral exclusion for TBS is suggested.

INTRODUCTION

Spinal degenerative changes elevate DXA-measured BMD, but reports find trabecular bone score (TBS) relatively unaffected. However, we observed patients where degenerative changes elevated both. Consequently, this study explored whether vertebral exclusion impacts TBS and subsequently TBS-adjusted FRAX risk.

METHODS

Clinical DXA interpretations of one physician were reviewed; those with vertebrae excluded per ISCD guidance were included in this study. BMD and TBS at L1-4 and from post-exclusion vertebrae were collected and used to adjust fracture risk (FRAX).

RESULTS

Of the patients, 102 had vertebrae excluded; their mean (SD) age, BMI, and lowest T-score were 71.6 (9.5) years, 25.4 (4.5) kg/m², and - 2.8 (1.0), respectively. Compared to L1-4, vertebral exclusion lowered (p < 0.0001) mean spine BMD and TBS by 9.5 and 3.1%, respectively. Vertebral exclusion decreased TBS by 0.040, being lower in 83%. In those with lower TBS, the mean adjusted 10-year fracture risk increased (p < 0.0001) by 0.94 and 0.32% for major osteoporotic (MOF) and hip fracture, respectively, in some risk increased by up to 4%. In those with higher TBS, adjusted risk was reduced, MOF - 0.49% and hip - 0.1%.

CONCLUSION

Vertebral exclusion following ISCD recommendations generally, but not always, lowers TBS. Consequently, the impact on TBS adjusted FRAX risk is variable. In most patients, vertebral exclusion lowers TBS; in some, this could result in a relevant change in calculated fracture risk. It seems reasonable to use TBS values from evaluable vertebrae to adjust FRAX. Further research to determine if vertebral exclusion improves fracture risk prediction is needed.

bis-(p-hydroxyphenyl)-pyridyl-2-methane (BHPM)-the active metabolite of the laxatives bisacodyl and sodium picosulfate-enhances contractility and secretion in human intestine in vitro

BACKGROUND

Stimulant laxatives are widely used to treat constipation. We investigated in human small and large intestinal preparations the effects of bis-(p-hydroxyphenyl)-pyridyl-2-methane (BHPM), the active metabolite of the laxatives bisacodyl and sodium picosulfate on smooth muscle tone and epithelial secretion.

METHODS

Circular and longitudinal muscle tone of small or large intestinal preparations were recorded with isometric force transducers. Epithelial ion flux (I_SC ) and tissue resistance was measured with Ussing chamber technique after apical and basolateral BHPM application to large intestinal mucosa/submucosa preparations. Studies were performed in macroscopically normal specimens from 79 patients.

KEY RESULTS

BHPM concentration-dependently (0.5-5 μM) increased the tone of circular and longitudinal muscle from small to large intestine. The effect was strongest in large intestinal longitudinal muscle and smallest in small intestinal circular muscle. Increase in muscle tone was prevented by the L-type Ca⁺⁺ channel blocker nifedipine but insensitive to the nerve blocker tetrodotoxin. Apical or basolateral BHPM concentration-dependently decreased or increased I_SC, respectively. The K_Ca 1.1 (BK) channel blocker iberiotoxin reversed apical I_SC decrease whereas tetrodotoxin reversed basolateral I_SC increase. BHPM had no effect on tissue resistance or nerve-mediated secretory or muscle response with one exception: at the highest concentration basolateral BHPM reduced nerve-mediated secretion.

CONCLUSIONS AND INTERFERENCES

BHPM enhanced mucosal secretion and muscle contractility. Results suggested that the laxative effect of BHPM was a consequence of the increase in muscle tone as well as an increased K⁺ secretion when acting luminally and a nerve-driven Cl^- and HCO₃^- secretion once acting basolaterally after absorption.

Could bioelectric impedance spectroscopy (BIS) measured appendicular intracellular water serve as a lean mass measurement in sarcopenia definitions? A pilot study

DXA lean mass measurement for sarcopenia diagnosis is not always possible. Bioelectric impedance spectroscopy (BIS), a portable technology, is a potential alternative to DXA-measured lean mass. This pilot study explores the possibility and proposes an arbitrarily chosen potential cut-point for appendicular intracellular water corrected by height (aICW/ht²).

INTRODUCTION

Sarcopenia definitions often include DXA lean mass measurement. However, DXA is not always available. We explored the potential of a less-expensive mobile method, bioelectric impedance spectroscopy (BIS), to assess lean mass for sarcopenia determination. We hypothesized that BIS-measured appendicular intracellular water (aICW/ht²) would correlate with DXA-measured appendicular lean mass (ALM)/ht² and with functional parameters. If so, establishing an aICW/ht² cut-point in sarcopenia definitions may be feasible.

METHODS

Sixty-one community-dwelling women, mean age 79.9, had BIS and DXA lean mass, grip strength, gait speed, and jumping mechanography assessments. BIS aICW was calculated using limb length and intracellular water resistance. aICW/ht² was compared to DXA-measured ALM/ht² by linear regression. The European Working Group ALM/ht² and an exploratory aICW/ht² cut-point were utilized.

RESULTS

In this cohort, ALM/ht² and aICW/ht² were moderately correlated, R² = 0.55, p < 0.0001. Lean mass was low in 7 and normal in 44 by BIS and DXA. Those with low aICW/ht² had lower grip strength (p = 0.04) and jump power (p = 0.0002) than those with normal aICW/ht² and ALM/ht². Subjects with low ALM/ht² had lower jump power (p = 0.0006) but were not different in gait speed or grip strength.

CONCLUSIONS

BIS aICW is correlated with DXA-measured ALM directly, and when height adjusted. An aICW/ht² cut-point of 6.5 L/m² identified 70% of women with low ALM/ht². Women with low lean mass by DXA and BIS had poorer function measured by jump power. These pilot data support further evaluation of BIS measurement inclusion into sarcopenia definitions.

Multiple vertebral fractures following osteoporosis treatment discontinuation: a case-report after long-term Odanacatib

INTRODUCTION

Case reports of women sustaining multiple vertebral fractures (VF) soon afterdenosumab discontinuation are accumulating.

METHODS

We report a woman with five new vertebral fractures in ~8 months following discontinuation of long-term odanacatib (ODN), an experimental cathepsin K inhibitor.

RESULTS

DXA examination demonstrated an ~12% decline in bone mineral density (BMD) and ~9% decline in trabecular bone score (TBS) since ODN discontinuation. Laboratory evaluation did not reveal a secondary cause of bone loss.

CONCLUSIONS

This case mimics observations following denosumab discontinuation, but, to our knowledge, is the first reported with ODN and the first documenting substantial decline in TBS. While not directly clinically relevant as ODN is no longer being developed, this case raises the possibility that a syndrome of multiple vertebral fractures could follow discontinuation of various potent osteoporosis therapies that produce major BMD increases but do not have persisting bone effects (i.e., all non-bisphosphonates). Use of antiresorptive therapies to prevent rapid bone loss following discontinuation of potent bone active agents seems appropriate. Identification of those patients who could be at risk for the multiple VF syndrome is needed.

Do Textiles Impact DXA Bone Density or Body Composition Results?

External artifacts can confound dual-energy X-ray absorptiometry (DXA) measurements. It is often accepted that garments free of metal do not affect DXA results; however, little data exist in this regard. It is plausible that some textiles absorb radiation and thereby alter DXA results. We hypothesized that some dense or synthetic textiles, for example, reflective materials, might alter DXA-measured bone and soft tissue mass. Hologic and GE Lunar spine phantoms and a Bioclinica prototype total body phantom were imaged on a GE Lunar iDXA and Prodigy densitometer. Each phantom was scanned 10 times to establish mean values. Subsequently, 2 layers of various fabrics were placed over the entire top surface of the phantom, and 10 scans were performed without repositioning. Samples of natural, synthetic, or embellished fabric (including those with reflective material) and of varying thickness were used. Wilcoxon signed rank tests were used to compare the means between bare phantom and textile-covered phantom. Significant differences were demonstrated often, depending on the scanner, phantom, and textile used. A polyester fabric with reflective strip consistently altered measurements. For example, this fabric increased measured mean lumbar spine bone mineral density and total body bone mineral content by 0.008 g/cm² and 3.6 g, respectively (p < 0.01). Similarly, mean total body fat decreased (-173 g) and lean mass increased (+213 g; p < 0.01). Fat and lean mass were also affected by metallic thread, wool, blend denim, and shiny polyester (p < 0.05), and lean mass was affected by cotton denim and sweatshirt material (p < 0.0003). In conclusion, textiles can affect DXA-measured bone mineral density and body composition results. Even small amounts of reflective material could alter mass measurements by ~25% of the least significant change. Clothing made of dense textiles (e.g., wool and denim) or those with reflective material and metallic thread should be avoided during DXA scanning.

Comparison of muscle/lean mass measurement methods: correlation with functional and biochemical testing

DXA-measured lean mass is often used to assess muscle mass but has limitations. Thus, we compared DXA lean mass with two novel methods-bioelectric impedance spectroscopy and creatine (methyl-d3) dilution. The examined methodologies did not measure lean mass similarly and the correlation with muscle biomarkers/function varied.

INTRODUCTION

Muscle function tests predict adverse health outcomes better than lean mass measurement. This may reflect limitations of current mass measurement methods. Newer approaches, e.g., bioelectric impedance spectroscopy (BIS) and creatine (methyl-d3) dilution (D3-C), may more accurately assess muscle mass. We hypothesized that BIS and D3-C measured muscle mass would better correlate with function and bone/muscle biomarkers than DXA measured lean mass.

METHODS

Evaluations of muscle/lean mass, function, and serum biomarkers were obtained in older community-dwelling adults. Mass was assessed by DXA, BIS, and orally administered D3-C. Grip strength, timed up and go, and jump power were examined. Potential muscle/bone serum biomarkers were measured. Mass measurements were compared with functional and serum data using regression analyses; differences between techniques were determined by paired t tests.

RESULTS

Mean (SD) age of the 112 (89F/23M) participants was 80.6 (6.0) years. The lean/muscle mass assessments were correlated (.57-.88) but differed (p < 0.0001) from one another with DXA total body less head being highest at 37.8 (7.3) kg, D3-C muscle mass at 21.1 (4.6) kg, and BIS total body intracellular water at 17.4 (3.5) kg. All mass assessment methods correlated with grip strength and jump power (R = 0.35-0.63, p < 0.0002), but not with gait speed or repeat chair rise. Lean mass measures were unrelated to the serum biomarkers measured.

CONCLUSIONS

These three methodologies do not similarly measure muscle/lean mass and should not be viewed as being equivalent. Functional tests assessing maximal muscle strength/power (grip strength and jump power) correlated with all mass measures whereas gait speed was not. None of the selected serum measures correlated with mass. Efforts to optimize muscle mass assessment and identify their relationships with health outcomes are needed.

A focused evaluation of lumbar spine trabecular bone score in the first year post-menarche

Trabecular bone score, an index of lumbar spine trabecular texture, has not been explored fully in adolescent girls. Our cross-sectional analysis supported the hypothesis that "adult normal" trabecular bone score has been achieved by the end of the first year post-menarche, providing a potential screening tool, independent from bone density.

INTRODUCTION

Trabecular bone score (TBS) evaluates lumbar spine (LS) trabecular texture from DXA images. Limited evidence suggests low TBS in pre-pubertal girls. TBS has not been assessed in the context of the key peri-menarcheal bone accrual phase. Thus, we evaluated (1) whether "normal" adult TBS (≥ 1.35) is reached in the first year post-menarche and (2) the role of maturational timing (menarcheal age) and status (gynecological age) in TBS variation.

METHODS

For 44 healthy girls aged 11 to 13 years, whole body and LS DXA scans were obtained within 1 year post-menarche. As TBS is optimized for adults and can be affected by body thickness, custom software provided unadjusted "rawTBS" and adjusted for tissue thickness "corrTBS" (TBS iNsight, Medimaps, France). Correlations evaluated menarcheal age and gynecological age as factors in LS bone mineral content (BMC), areal bone mineral density (BMD), and TBS.

RESULTS

Lowest observed TBS exceeded 1.35 (rawTBS = 1.362; corrTBS = 1.352). Menarcheal age correlated negatively with rawTBS (r = - 0.34, p = 0.02), with a similar trend for corrTBS (r = - 0.29, p < 0.06). Gynecological age did not correlate with TBS but was positively correlated with LSBMD (r = + 0.37, p = 0.01). Correlations with body composition variables differed between rawTBS and corrTBS.

CONCLUSIONS

In this healthy cohort, "normal" adult TBS is present by 1 year post-menarche, 2 years before projected LS peak bone mass. Thus, TBS may be a useful bone architectural screen during the first post-menarcheal year, enabling intervention to improve structure prior to "peak bone mass". Longitudinal studies are needed to elucidate TBS development and intervention response.

Electrical Properties Assessed by Bioelectrical Impedance Spectroscopy as Biomarkers of Age-related Loss of Skeletal Muscle Quantity and Quality

Skeletal muscle, in addition to being comprised of a heterogeneous muscle fiber population, also includes extracellular components that do not contribute to positive tensional force production. Here we test segmental bioelectrical impedance spectroscopy (S-BIS) to assess muscle intracellular mass and composition. S-BIS can evaluate electrical properties that may be related to muscle force production. Muscle fiber membranes separate the intracellular components from the extracellular environment and consist of lipid bilayers which act as an electrical capacitor. We found that S-BIS measures accounted for ~85% of the age-related decrease in appendicular muscle power compared with only ~49% for dual-energy x-ray absorptiometry (DXA) measures. Indices of extracellular (noncontractile) and cellular (contractile) compartments in skeletal muscle tissues were determined using the Cole-Cole plot from S-BIS measures. Characteristic frequency, membrane capacitance, and phase angle determined by Cole-Cole analysis together presented a S-BIS complex model that explained ~79% of interindividual variance of leg muscle power. This finding underscores the value of S-BIS to measure muscle composition rather than lean mass as measured by DXA and suggests that S-BIS should be highly informative in skeletal muscle physiology.