Updated practice guideline for dual-energy X-ray absorptiometry (DXA)

The introduction of dual-energy X-ray absorptiometry (DXA) technology in the 1980s revolutionized the diagnosis, management and monitoring of osteoporosis, providing a clinical tool which is now available worldwide. However, DXA measurements are influenced by many technical factors, including the quality control procedures for the instrument, positioning of the patient, and approach to analysis. Reporting of DXA results may be confounded by factors such as selection of reference ranges for T-scores and Z-scores, as well as inadequate knowledge of current standards for interpretation. These points are addressed at length in many international guidelines but are not always easily assimilated by practising clinicians and technicians. Our aim in this report is to identify key elements pertaining to the use of DXA in clinical practice, considering both technical and clinical aspects. Here, we discuss technical aspects of DXA procedures, approaches to interpretation and integration into clinical practice, and the use of non-bone mineral density measurements, such as a vertebral fracture assessment, in clinical risk assessment.

Intraoperative physician assessment during total hip arthroplasty correlates with DXA parameters

PURPOSE

Orthopedic surgeons can assess bone status intraoperatively and recommend skeletal health evaluation for patients with poor bone quality. Intraoperative physician assessment (IPA) at the time of total knee arthroplasty correlates with preoperative DXA-measured bone mineral density (BMD). This study evaluated IPA during total hip arthroplasty (THA) as a quantitative measure of bone status based on tactile assessment.

METHODS

This retrospective analysis identified 60 patients (64 hips) undergoing primary THA who had IPA recorded in the operative report and a DXA within 2 years before surgery. Intraoperatively, two surgeons assessed bone quality on a 5-point scale (1 = excellent; 5 = poor). IPA score was compared to DXA BMD and T-score, 3D Shaper measurements, WHO classification, FRAX scores, radiographic Dorr classification, and cortical index.

RESULTS

There was a strong correlation between the IPA score and lowest T-score, WHO classification, and FRAX major and hip fracture scores (r =  ± 0.485-0.622, all p < 0.001). There was a moderate correlation between IPA score and total hip BMD and 3D Shaper measurements, including trabecular volumetric BMD, cortical surface BMD, and cortical thickness (r =  ± 0.326-0.386, all p < 0.01). All patients with below-average IPA scores had osteopenia or osteoporosis by DXA.

CONCLUSION

IPA during THA is a simple, valuable tool for quantifying bone status based on tactile feedback. This information can be used to identify patients with poor bone quality that may benefit from skeletal status evaluation and treatment and provide intraoperative guidance for implant selection. Orthopedic surgeons can assess bone health at the time of surgery. Intraoperative physician assessment (IPA) is a bone quality score based on surgeons' tactile assessment that correlates strongly with the lowest T-score, WHO classification, and FRAX fracture risk. IPA can guide surgical decision-making and future bone health treatment.

Periprosthetic fractures are osteoporotic fractures: missed opportunities for osteoporosis diagnosis

Joint replacement surgery is common in older adults, leading to increasing periprosthetic fracture (PPFx) occurrence. We reviewed all PPFx seen over a 4-year period at an academic hospital. Clinical osteoporosis could be diagnosed based on existing data in 104 (67%) at the time of PPFx. Periprosthetic fractures are generally osteoporosis-related.

PURPOSE

Periprosthetic fractures (PPFx) cause morbidity, mortality, and cost. This study's purpose was to describe osteoporosis-related data available at the time of PPFx.

METHODS

The electronic medical record (EMR) of PPFx patients seen over 4 years in a university orthopedic practice were reviewed. Demographic data and osteoporosis relevant parameters were collected. Prior DXA studies were reviewed, and L1 Hounsfield unit (HU) measurements were performed on CT scans obtained within 2 years before PPFx. Clinical osteoporosis was defined as prior diagnosis, prescribed osteoporosis treatment, T-score ≤  - 2.5, HU ≤ 100, or prior fracture.

RESULTS

Records of 156 PPFx patients (115 F/41 M), mean (SD) age 75.4 (11.9), were reviewed. Almost all 153/156 (98%) of these fractures were femoral. Falls caused 139 (89%); 12 (8%) were spontaneous. Mean time post-arthroplasty was 7.9 (6.3) years. Prior fragility fracture(s) occurred in 72 (46%); 14 were PPFx. Osteoporosis was previously diagnosed in 45 (29%) and medications prescribed in 41 (26%). Prior to PPFx, DXA data were available in 62, mean (SD) lowest T-score was - 1.9 (0.9) and was ≤  - 2.5 in 19. CT data were available in 46; mean (SD) L1 HU was 79.0 (29.4) and was ≤ 100 in 35. Based on existing data, clinical osteoporosis could have been diagnosed in 104 (67%) at the time of PPFx.

CONCLUSION

Periprosthetic fractures are osteoporosis-related. They occur in older adults, often female, and result from falls; BMD, when assessed, is low. Data available at the time of PPFx often allows osteoporosis diagnosis; this should prompt evaluation and pharmacologic treatment consideration.

Reporting of Full-Length Femur Imaging to Detect Incomplete Atypical Femur Fractures: 2023 Official Positions of the International Society for Clinical Densitometry

Incomplete atypical femur fractures (iAFFs) are associated with the long-term use of anti-resorptive therapies. Although X-rays are typically used to screen for iAFFs, images from dual-energy X-ray absorptiometry (DXA) offer an alternate method for detecting iAFFs. Although a previous 2019 ISCD Official Position on this subject exists, our task force aimed to update the literature review and to propose recommendations on reporting findings related to iAFFs that may be observed on DXA images. The task force recommended that full-length femur imaging (FFI) from DXA can be used as a screening tool for iAFFs. The presence of focal lateral cortical thickening and transverse lucencies should be reported, if identified on the FFI. This task force proposed a classification system to determine the likelihood of an iAFF, based on radiographic features seen on the FFI. Lastly, the task force recommended that the clinical assessment of prodromal symptoms (pain) is not required for the assessment of FFI.

DXA Reporting Updates: 2023 Official Positions of the International Society for Clinical Densitometry

INTRODUCTION

Professional guidance and standards assist radiologic interpreters in generating high quality reports. Initially DXA reporting Official Positions were provided by the ISCD in 2003; however, as the field has progressed, some of the current recommendations require revision and updating. This manuscript details the research approach and provides updated DXA reporting guidance.

METHODS

Key Questions were proposed by ISCD established protocols and approved by the Position Development Conference Steering Committee. Literature related to each question was accumulated by searching PubMed, and existing guidelines from other organizations were extracted from websites. Modifications and additions to the ISCD Official Positions were determined by an expert panel after reviewing the Task Force proposals and position papers.

RESULTS

Since most DXA is now performed in radiology departments, an approach was endorsed that better aligns with standard radiologic reports. To achieve this, reporting elements were divided into required minimum or optional. Collectively, required components comprise a standard diagnostic report and are considered the minimum necessary to generate an acceptable report. Additional elements were retained and categorized as optional. These optional components were considered relevant but tailored to a consultative, clinically oriented report. Although this information is beneficial, not all interpreters have access to sufficient clinical information, or may not have the clinical expertise to expand beyond a diagnostic report. Consequently, these are not required for an acceptable report.

CONCLUSION

These updated ISCD positions conform with the DXA field's evolution over the past 20 years. Specifically, a basic diagnostic report better aligns with radiology standards, and additional elements (which are valued by treating clinicians) remain acceptable but are optional and not required. Additionally, reporting guidance for newer elements such as fracture risk assessment are incorporated. It is our expectation that these updated Official Positions will improve compliance with required standards and generate high quality DXA reports that are valuable to the recipient clinician and contribute to best patient care.

Reporting Fewer Than Four Vertebrae: 2023 Official Positions of the International Society for Clinical Densitometry

The precision for spine bone mineral density (BMD) worsens as vertebrae are excluded, so recommendations are needed for least significant change (LSC) for spine BMDs based on fewer than 4 vertebrae. The task force recommends re-analysis of each facility's L1-L4 in-house precision study to determine the precision in order to calculate the LSC for each combination of 2 or 3 reported vertebrae. The task force recommended not reporting spine BMDs based on single vertebral bodies for either the diagnosis or monitoring of osteoporosis. Specific data for studies assessing the precision of two non-contiguous vertebrae are mixed, but ultimately the task force recommended that spine BMD based on 2 non-contiguous vertebrae can be used for the diagnosis and monitoring of osteoporosis.

Dual-energy X-ray Absorptiometry Trends Among US Medicare Beneficiaries: 2005-2019

INTRODUCTION

Bone density measured using dual-energy X-ray absorptiometry (DXA) volume, performance site and interpreters have changed in the US since 2005. The purpose of this report is to provide updated trends in DXA counts, rates, place of service and interpreter specialty for the Medicare fee-for-service population.

METHODS

The 100 % Medicare Physician/Supplier Procedure Summary Limited Data Set between 2005-2019 was used. DXA counts and annual rates per 10,000 Medicare beneficiaries were calculated. Annual distributions of scan performance location, provider type and interpreter specialty were described. Place of service trends (significance assigned at p < 0.05) of the mean annual share of DXA utilization were identified using linear regression.

RESULTS

Annual DXA use per 10,000 beneficiaries peaked in 2008 at 832, declined to 656 in 2015 then increased (p < 0.001) by 38 per year to 807 in 2019. From 2005 to 2019 DXA performance in office settings declined from 70.7 % to 47.2 %. Concurrently, outpatient hospital (OH) DXA increased from 28.6 % to 51.7 %. In 2005, 43.5 % of DXAs were interpreted by radiologists. This increased (p < 0.001) in the office and OH, averaging 0.3 and 2.0 percentage points per year respectively, reaching 73.5 % in 2019. Interpretation by most non-radiologist specialties declined (p < 0.001).

CONCLUSIONS

From 2005-2019, total DXA use among Medicare beneficiaries declined reaching a nadir in 2015 then returned to 2005 levels by 2019. Office DXA declined since 2005 with 51.7 % of all scans now occurring in an OH setting. The proportion of DXAs interpreted by radiologists increased over time, reaching 73.5 % in 2019.

Bilateral hip DXA Reporting: 2023 Official Positions of the International Society for Clinical Densitometry

INTRODUCTION

This position development conference (PDC) Task Force examined the use and reporting of bilateral hip bone mineral density (BMD) measurements. This was deemed appropriate as increased availability of Dual-energy X-ray Absorptiometry (DXA) technology offering bilateral hip measurement resulted in more routine clinical use. The International Society for Clinical Densitometry Official Positions accept bilateral hip BMD measurement for clinical use but currently do not include recommendations for reporting those studies.

METHODS

Four key questions regarding bilateral hip reporting were proposed by the PDC Steering Committee. Relevant literature was identified using PubMed. Questions included whether bilateral hip measurements are appropriate for diagnostic classification or monitoring, as well as which bilateral hip regions of interest should be reported for diagnosis and monitoring. Additionally, the appropriate nomenclature for bilateral hip acquisition was defined.

RESULTS

The literature review demonstrated that bilateral hip measurement is appropriate and diagnostic classification should be based on the lowest T-score at the right or left side femoral neck or total hip; the mean T-score should not be used for diagnostic purposes. Mean bilateral total hip is preferred for BMD monitoring. The terms hip, or total hip were deemed appropriate nomenclature instead of femur or total proximal femur.

CONCLUSION

Bilateral hip acquisition is clinically appropriate and reporting and nomenclature standards are offered herein when a bilateral hip study is acquired. In terms of future research, the impact of discordant hips on diagnosis and monitoring was identified as a significant knowledge gap.

Intraoperative physician assessment of bone: correlation to bone mineral density

This study evaluated the intraoperative physician assessment (IPA) of bone status at time of total knee arthroplasty. IPA was highly correlated with distal femur and overall bone mineral density. When IPA identifies poor bone status, formal bone health assessment is indicated.

PURPOSE

Intuitively, intraoperative physician assessment (IPA) would be an excellent measure of bone status gained through haptic feedback during bone preparation. However, no studies have evaluated the orthopedic surgeon's ability to do so. This study's purpose, in patients undergoing total knee arthroplasty (TKA), was to relate IPA with (1) the lowest bone mineral density (BMD) T-score at routine clinical sites; and (2) with distal femur BMD.

METHODS

Seventy patients undergoing TKA by 3 surgeons received pre-operative DXA. Intraoperatively, bone quality was assessed on a 5-point scale (1 excellent to 5 poor) based on tactile feedback to preparation. Demographic data, DXA results, and IPA score between surgeons were compared by factorial ANOVA. Lowest T-score and distal femur BMD were associated with IPA using Spearman's correlation.

RESULTS

The mean (SD) age and BMI were 65.8 (7.6) years and 31.4 (5.1) kg/m², respectively. Patient demographic data, BMD, and IPA (mean [SD] = 2.74 [1.2]) did not differ between surgeons. IPA correlated with the lowest T-score (R = 0.511) and distal femur BMD (R = 0.603-0.661). Based on the lowest T-score, no osteoporotic patients had an IPA above average, and none with normal BMD was classified as having poor bone.

CONCLUSIONS

IPA is highly correlated with local (distal femur) and overall BMD. This study supports the International Society for Clinical Densitometry position that surgeon concern regarding bone quality should lead to bone health assessment. As IPA is comparable between surgeons, it is logical this can be widely applied by experienced orthopedic surgeons. Future studies evaluating IPA at other anatomic sites are indicated.

Proposed bone health screening protocol to identify total knee arthroplasty patients for preoperative DXA

This study evaluates a novel, simple bone health screening protocol composed of patient sex, age, fracture history, and FRAX risk to identify total knee arthroplasty patients for preoperative DXA. Findings supported effectiveness, with sensitivity of 1.00 (CI 0.92-1.00) and specificity of 0.54 (CI 0.41-0.68) when evaluating for clinical osteoporosis.

PURPOSE

Bone health optimization is a process where osteoporotic patients are identified, evaluated via modalities such as dual-energy X-ray absorptiometry (DXA), and treated when indicated. There are currently no established guidelines to determine who needs presurgical DXA. This study evaluates the effectiveness of a simple screening protocol to identify TKA patients for preoperative DXA.

METHODS

This prospective cohort study began on September 1, 2019, and included 100 elective TKA patients. Inclusion criteria were ≥ 50 years and primary TKA. All patients obtained routine clinical DXA. The screening protocol defining who should obtain DXA included meeting any of the following: female ≥ 65, male ≥ 70, fracture history after age 50, or FRAX major osteoporotic fracture risk without bone mineral density (BMD) adjustments ≥ 8.4%. Osteoporosis was defined by the World Health Organization (WHO) criteria (T-score ≤  - 2.5) or clinically (T-score ≤  - 2.5, elevated BMD-adjusted FRAX risk, or prior hip/spine fracture). Sensitivity and specificity were calculated.

RESULTS

The study included 68 females and 32 males, mean age 67.2 ± 7.7. T-score osteoporosis was observed in 16 patients while 43 had clinical osteoporosis. Screening criteria recommending DXA was met by 69 patients. Screening sensitivity was 1.00 (CI 0.79-1.00) and specificity was 0.37 (CI 0.27-0.48) for identifying patients with T-score osteoporosis. Similar sensitivity of 1.00 (CI 0.92-1.00) and specificity of 0.54 (CI 0.41-0.68) were found for clinical osteoporosis.

CONCLUSIONS

A simple screening protocol identifies TKA patients with T-score and clinical osteoporosis for preoperative DXA with high sensitivity in this prospective cohort study.

Humeral BMD can be Measured With DXA and Is Lower in the Surgical Arm After Total Shoulder Arthroplasty

BACKGROUND

As arthroplasty leads to bone loss, we hypothesized that humeral bone mineral density (BMD) is lower after total shoulder arthroplasty (TSA) in the operative versus non-operative arm. However, there is no clinical approach to measure humeral BMD with dual-energy x-ray absorptiometry (DXA). The purposes of this pilot study were to develop DXA methodology to measure humerus BMD, propose humerus regions of interest (ROIs), compare TSA BMD to the non-operative arm, correlate humeral BMD with standard sites, and evaluate measurement reproducibility.

METHODOLOGY

Thirty-eight adults 1-5 years post-TSA had standard clinical DXA scans plus full humerus scans using the atypical femur fracture feature; precision was assessed in a subset (n = 32). Six custom ROIs were used to measure BMD throughout the humerus. Radius and humeral BMD were compared between arms by paired t-test and correlated ipsilaterally using Pearson's Correlation. Custom ROI BMD precision was assessed using the International Society for Clinical Densitometry (ISCD) advanced precision calculator.

RESULTS

Study included 38 subjects (24M/14F), with mean (SD) age and time post-surgery of 69.6 (7.7) years and 2.5 (1.3) years respectively. BMD was lower (p &lt; 0.01) at all custom humerus sites (3.8% to 8.2%) on the surgical side but not different at radius sites. Humeral BMD correlated positively with ipsilateral ultra-distal and 1/3 radius (r = 0.54 to 0.86; p &lt; 0.05). Custom BMD precision (%CV) ranged from 6.0-16.0%.

CONCLUSIONS

Humerus BMD can be measured using DXA and is lower in the TSA arm. Radius BMD correlated with humeral BMD but was not lower in the surgical arm. BMD precision was worse than usual clinical sites; use of software optimized for the femur is a notable limitation and likely contributes to suboptimal precision. Further study to assess the clinical utility of humeral BMD is needed. Automation and optimization of these measurements should improve precision.

Bone Texture Assessment on Lateral VFAs Using the Texture Research Investigational Platform (TRIP) and its Fracture Discrimination Ability

Texture Research Imaging Platform applies trabecular bone score (TBS) measurement principles to images acquired with multiple modalities to assess bone texture at various skeletal sites. This study aimed to assess the bone texture score in dual-energy X-ray absorptiometry-acquired lateral vertebral fracture assessment (VFA) images (BTS_VFA), evaluate its reproducibility, and vertebral fracture discrimination ability. Subjects included 178 VF cases and 178 non-VF controls, 136 women and 42 men in each group, age 55-92 years, from two research centers. Cases and controls were matched for age (±5 years), body mass index (±5 kg/m²) and TBS. All participants underwent dual-energy X-ray absorptiometry TBS assessment from standard posterior-anterior lumbar spine scans and BTS_VFA assessment. VF presence was determined using VFA images applying the Genant's method. BTS_VFA was lower among fractured women compared to non-fractured (0.626 ± 0.109 vs 0.675 ± 0.099, p < 0.01), but not among men. In a binary logistic regression adjusted for study center and sex, for each SD lower BTS_VFA, there was a 40% increase (OR 1.40, 95% CI (1.13-1.74)) in the risk of having a prevalent VF; area under the curve (95% CI) 0.616 (0.557-0.675). Inter-assessor and inter-centers ICCs for BTS_VFA measurements were very good; 0.96 (0.64-0.99) and 0.98 (0.95-0.99), respectively. The BTS_VFA precision (coefficient of variation) was 2.42%. This feasibility study demonstrates the potential to assess trabecular bone texture in lateral VFA images with good reproducibility. BTS_VFA can discriminate between fractured and non-fractured women independent of their age, body mass index and TBS. In conclusion, BTS_VFA, a potential trabecular texture assessment that excludes the posterior elements, may have value in fracture prediction or as a novel approach to be further investigated in spine surgery planning.

A Novel Osteoporosis Screening Protocol to Identify Orthopedic Surgery Patients for Preoperative Bone Health Optimization

Introduction

Osteoporosis is highly prevalent in elective orthopedic surgery. While preoperative bone health optimization decreases osteoporosis-related complications, there is an unmet need to establish who may benefit from preoperative dual-energy x-ray absorptiometry (DXA). This study assesses a novel, simple screening protocol to identify orthopedic surgical patients for preoperative DXA.

Materials/Methods

This retrospective cohort study included 628 patients undergoing total knee, hip, or shoulder arthroplasty or thoracolumbar spine fusion. Inclusion criteria were ≥40 years undergoing primary elective surgery. Screening criteria defining who should obtain DXA due to high osteoporosis risk included: female ≥65, male ≥70, fracture history when ≥50 years, or FRAX major osteoporotic fracture risk (without bone mineral density [BMD]-adjustments) ≥8.4%. Osteoporosis was defined by World Health Organization criteria [T-score ≤ -2.5], clinical National Osteoporosis Foundation (NOF) criteria [T-score ≤ -2.5, elevated BMD-adjusted FRAX risk, or prior hip/spine fracture], and modified clinical criteria [NOF criteria simplified to include any non-traumatic prior fracture and FRAX without BMD].

Results

The study included 100 TKAs, 100 THAs, 251 TSAs, and 177 spine fusions, average age 65.6 ± 9.8. DXA was available for 209 patients. Screening criteria recommending DXA was met by 362 patients. For those with DXA, screening sensitivity was .96 (CI: .78 to .99) and specificity was .19 (CI: .14 to .25) for identifying T-score osteoporosis. Similar sensitivity of .99 (CI: .91 to .99) and specificity of .61 (CI: .56 to .66) were found for modified clinical osteoporosis. For modified clinical osteoporosis, 192 patients with osteoporosis met criteria (true pos.), 1 patient with osteoporosis did not meet criteria (false neg.), 170 patients without osteoporosis met criteria (false pos.), and 265 patients without osteoporosis did not meet criteria (true neg.).

Discussion/Conclusion

A simple screening protocol identifies orthopedic surgical candidates at risk of T-score or clinical osteoporosis for preoperative DXA with high sensitivity.

Effect of degeneration on bone mineral density, trabecular bone score and CT Hounsfield unit measurements in a spine surgery patient population

This study investigated the impact of spinal degeneration on bone mineral density (BMD), trabecular bone score (TBS), and CT Hounsfield units in an at-risk population. We found that BMD was increased by degeneration, whereas TBS and HU were unaffected. These findings support that TBS is not adversely affected by spinal degeneration.

INTRODUCTION

This study evaluated the impact of spinal degeneration on BMD and TBS measured by dual-energy x-ray absorptiometry (DXA) and on CT HU in a spine surgery patient population.

METHODS

A retrospective study of 63 patients referred for consideration of spine surgery or with history of spine surgery was performed. Patients were included if a DXA scan and a CT containing the lumbar spine were obtained within 18 months of each other. DXA data were collected and analyzed by vertebral level. Individual vertebrae were assessed for degenerative changes by qualitative evaluation of the anterior and posterior elements using CT. Degeneration scores were compared to BMD T-scores, TBS and CT HU at individual vertebral levels L1-4, and after applying International Society for Clinical Densitometry (ISCD) criteria for excluding vertebrae from diagnostic consideration.

RESULTS

Mean patient age and BMI were 67.2 years and 27.8 kg/m², respectively; 79.4% were female. Mean (SD) lowest T-scores of the hip, spine, and lowest overall T-score were - 1.3 (1.4), - 1.7 (0.9), and - 1.9 (1.0), respectively. Osteoporosis was present by T-score in 38% and osteopenia in 52%; 10% had a history of osteoporotic fracture. The mean degeneration score of individual vertebrae was 4.1 on a 0-6 scale. T-score correlated moderately with degeneration score (Spearman's rho 0.484, p < 0.001), whereas TBS and HU were unrelated. ISCD excluded vertebrae had a higher degeneration score than included vertebrae (p =  < 0.001).

CONCLUSIONS

In a spine surgery population, TBS and CT HU values are unrelated to degeneration score and thus appear unaffected by lumbar vertebral degenerative changes. Additionally, these data support the ISCD criteria for vertebral exclusion.

Femur and Tibia BMD Measurement in Elective Total Knee Arthroplasty Candidates

Distal femur BMD declines ∼20% following total knee arthroplasty (TKA) potentially leading to adverse outcomes. BMD knowledge before and following TKA might allow interventions to optimize outcomes. We hypothesized that distal femur and proximal tibial BMD could be reproducibly measured with existing DXA technology. Elective TKA candidates were enrolled and standard clinical DXA plus bilateral PA and lateral knee scans acquired. Manual regions of interest (ROIs) were placed at distal femur and proximal tibia sites based on required TKA machining and periprosthetic fracture location. Intra- and inter-rater BMD reliability was assessed by intra-class correlation (ICC). Custom and standard proximal femur BMD were correlated by linear regression and paired t test evaluated BMD differences between planned surgical and contralateral side. One hundred subjects (68F/32M), mean (SD) age and BMI of 67.2 (7.7) yr and 30.8 (4.8) kg/m² were enrolled. Lowest clinical BMD T-score was < -1.0 in 65% and ≤ -2.5 in 16%; 34 had prior fracture. BMD reproducibility at all custom ROIs was excellent; ICC > 0.96. Mean BMD at custom ROIs ranged from 0.903 to 1.346 g/cm² in the PA projection and 0.891 to 1.429 g/cm² in the lateral. Lower BMD values were observed at the proximal tibia, while the higher measurements were at the femur condyle. Custom knee ROI BMD was highly correlated (p < 0.0001) with total and femur neck with better correlation at ROIs adjacent to the joint (R² = 0.62-0.67, 0.49-0.55 respectively). In those without prior TKA (n = 76), mean BMD was lower (2.8%-6.6%; p < 0.05) in the planned surgical leg at all custom ROIs except the PA tibial regions. Individual variability was present with 82% having a custom ROI with lower BMD (up to 53%) in the planned operative leg. Distal femur and proximal tibial BMD can be measured using custom ROIs with good reproducibility. Suboptimal bone status is common in TKA candidates and distal femur/proximal tibia BMD is often lower on the planned operative side. Routine distal femur/proximal tibial BMD measurement might assist pre-operative interventions, surgical decision-making, subsequent care and outcomes. Studies to evaluate these possibilities are indicated.

Effect of semi-recumbent vibration exercise on muscle outcomes in older adults: a pilot randomized controlled clinical trial

Background

Many older adults with physical limitations living in residential care apartments are unable to exercise in a standing position and are at risk for declining in muscle function leading to falls and injury. Novel approaches to achieve exercise benefits are needed. The purpose of this study was to test the effect of semi-recumbent vibration exercise on muscle outcomes in older adults living in residential care apartment complexes (RCACs).

Methods

A randomized, crossover design was used to examine the effect of semi-recumbent vibration exercise on muscle function and mass among 32 RCAC residents (mean age 87.5 years) with physical limitations. Participants received a randomized sequence of two study conditions: sham or vibration for 8 weeks each separated by a 4-week washout. Before and after the 8 weeks of vibration treatment and sham treatment, muscle mechanography was used to assess muscle function including jump power, weight-corrected jump power, and jump height. Short physical performance battery (SPPB) and handgrip strength were also used to measure muscle function. Bioelectrical impedance spectroscopy was used to estimate skeletal muscle mass. The effect of the vibration treatment on muscle outcomes was analyzed through mixed effects linear regression models.

Results

Vibration exercise leads to better jump height (p < .05) compared to sham exercise but also poorer chair rise performance (p = 0.012). Other muscle functions tests and muscle mass parameters showed non-significant changes.

Conclusion

This small pilot study showed no conclusive results on the effect of semi-recumbent vibration exercise on muscle function and mass in older adults living in RCAC. However, the promising signals of improved jump performance could be used to power larger studies of longer duration with various vibration doses to determine the benefit of vibration exercise in this physically impaired, high-risk population with few exercise capabilities.

Trial registration

The study is registered at clinicaltrials.gov (NCT02533063; date of first registration 26/08/2015).

Proceedings of the 2021 Santa Fe Bone Symposium: Advances in the Management of Osteoporosis and Metabolic Bone Diseases

The 2021 Virtual Santa Fe Bone Symposium was held August 5-8, with over 300 registered attendees from throughout the USA, and at least 18 other countries. This annual meeting focuses on applying advances in basic science and clinical research to the care of patients with osteoporosis and those with inherited and acquired disorders of bone metabolism. Participants represented a broad range of medical disciplines with an interest in skeletal diseases. These included physicians of many specialties and practice settings, fellows, advanced practice providers, fracture liaison service (FLS) coordinators, clinical researchers, and bone density technologists. There were lectures, case presentations, and panel discussions, all followed by interactive discussions. Breakout sessions included an FLS workshop, Bone Health TeleECHO workshop, special interest groups, meet-and-greet the faculty, and satellite symposia. The agenda covered topics of interest such as strategies for the use of osteoanabolic therapy, prevention of periprosthetic fractures, management of atypical femur fractures, what we know and don't know about vitamin D, advances in the use of dual-energy X-ray absorptiometry in the assessment of skeletal health, controversies and conundrums in osteoporosis care, skeletal health in transgender patients, management of patients with hypophosphatasia and hypophosphatemia, and treat-to-target approaches for managing patients with osteoporosis. The Proceedings of the 2021 Virtual Santa Fe Bone Symposium consists of highlights of each presentation with current strategies for optimizing the care of patients with skeletal disorders.

Combination of DXA and BIS Predicts Jump Power Better Than Traditional Measures of Sarcopenia

Traditional diagnostic criteria for sarcopenia use dual-energy X-ray absorptiometry (DXA)-measured appendicular lean mass (ALM), normalized to height (ALM/ht²) or body mass index (ALM/BMI) to define low muscle mass. However, muscle function declines with aging before the loss of muscle mass is detected by ALM. This is likely due, in part, to qualitative muscle changes such as extracellular and intracellular fluid compartment shifts uncaptured by DXA. We propose combining bioimpedance spectroscopy (BIS), which estimates extracellular and intracellular compartment volume, with DXA to more accurately predict muscle function. This combination may help incorporate muscle quality, thereby improving sarcopenia diagnosis. We cross-sectionally analyzed data from 248 Black and White participants aged 25 to 75 years from the Midlife in the United States Refresher Cohort. We proposed two novel muscle measures: ALM corrected by the BIS-derived whole-body extracellular to intracellular fluid ratio (E/I) and leg lean mass (LLM) corrected by leg-specific E/I, creating (ALM/(E/I)_W) and (LLM/(E/I)_L), respectively. We compared the associations of traditional muscle measures, ALM/(E/I)_W, and LLM/(E/I)_L, with grip strength and lower limb power using jumping mechanography. LLM/(E/I)_L explained jump power best at R ² = 0.803 compared with ALM/(E/I)_W (p < 0.0001) and all other measures. ALM/(E/I)_W explained jump power second best (R ² = 0.759) but not significantly better than traditional muscle measures. No muscle measure performed better than covariates when predicting handgrip strength. LLM/(E/I)_L outperformed ALM/ht² and ALM/BMI when predicting jump power. We propose LLM/(E/I)_L is a powerful and clinically relevant method that accounts for muscle quality. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

A Newly Recognized DXA Confounder: The Potassium-Binding Medication Sodium Zirconium Cyclosilicate

OBJECTIVE

Radio-dense artifacts, including contrast material, alter dual-energy X-ray absorptiometry (DXA) results. An apparent diffuse artifact was identified during spine DXA acquisition in a patient without recent radiographic procedures. The patient reported taking sodium zirconium cyclosilicate (SZC; Lokelma®) 10 g 1 h before scanning. SZC is a potassium-binding agent recently marketed to treat hyperkalemia. Given the chemical composition, we hypothesized that SZC may alter DXA results. This study evaluated if SZC affects DXA results using an encapsulated spine and a total body phantom.

METHODOLOGY

An encapsulated spine and total body phantom were scanned using a Lunar iDXA. Each phantom was scanned 5 times serially without repositioning in 5 configurations: (1) Bare, (2) 45 mL tap water, (3) 90 mL water, (4) 10 g SZC in 45 mL of water, and (5) 30 g SZC in 90 mL of water. Water and SZC was contained in plastic quart bags, folded, and placed over L2-3 on the spine phantom and flat over the pelvis/torso of the total body phantom.

RESULTS

Tap water did not change spine phantom measurements, but did increase (p < 0.05) total body phantom lean mass 46 g and 89 g with 45 mL and 90 mL, respectively. SZC 10 g or 30 g increased (p < 0.001) L2 and L3 bone mineral density (BMD) 18%-110%, mean 0.295 and 0.924 g/cm², respectively, while L1 and L4 BMD was statistically, but not clinically, altered by <0.010 g/cm². A dose-dependent change (p < 0.001) in total body phantom trunk measurements was demonstrated. The 10 g dose increased lean mass 16.8% and BMC 1%; fat mass was reduced 16.6%, while 30 g increased lean 41.9%, BMC 3.2%, and decreased fat 42.9%.

CONCLUSION

SZC confounds BMD and body composition phantom measurements. It is likely that SZC alters DXA results in humans. DXA technologists and interpreters should be aware of this confounder.

Defining an international cut-off of two-legged countermovement jump power for sarcopenia and dysmobility syndrome

We aimed to establish jump power cut-offs for the composite outcome of either sarcopenia (EWGSOP2) or dysmobility syndrome using Asian and Caucasian cohorts. Estimated cut-offs were sex specific (women: < 19.0 W/kg; men: < 23.8 W/kg) but not ethnicity specific. Jump power has potential to be used in definitions of poor musculoskeletal health.

PURPOSE

Weight-corrected jump power measured during a countermovement jump may be a useful tool to identify individuals with poor musculoskeletal health, but no cut-off values exist. We aimed to establish jump power cut-offs for detecting individuals with either sarcopenia or dysmobility syndrome.

METHODS

Age- and sex-matched community-dwelling older adults from two cohorts (University of Wisconsin-Madison [UW], Korean Urban Rural Elderly cohort [KURE], 1:2) were analyzed. Jump power cut-offs for the composite outcome of either sarcopenia defined by EWGSOP2 or dysmobility syndrome were determined.

RESULTS

The UW (n = 95) and KURE (n = 190) cohorts were similar in age (mean 75 years) and sex distribution (68% women). Jump power was similar between KURE and UW women (19.7 vs. 18.6 W/kg, p = 0.096) and slightly higher in KURE than UW in men (26.9 vs. 24.8 W/kg, p = 0.050). In UW and KURE, the prevalence of sarcopenia (7.4% in both), dysmobility syndrome (31.6% and 27.9%), or composite of either sarcopenia or dysmobility syndrome (32.6% and 28.4%) were comparable. Low jump power cut-offs for the composite outcome differed by sex but not by ethnicity (< 19.0 W/kg in women; < 23.8 W/kg in men). Low jump power was associated with elevated odds of sarcopenia (adjusted odds ratio [aOR] 4.07), dysmobility syndrome (aOR 4.32), or the composite of sarcopenia or dysmobility syndrome (aOR 4.67, p < 0.01 for all) independent of age, sex, height, and ethnicity.

CONCLUSION

Sex-specific jump power cut-offs were found to detect the presence of either sarcopenia or dysmobility syndrome in older adults independent of Asian or Caucasian ethnicity.