JBMR Plus

Osteoblastic bone metastasis, in which disseminated tumor cells drive net bone formation, is a clinically distinct and mechanistically underexplored form of skeletal disease that is enriched in hormone receptor-positive breast cancers. Preclinical models of bone metastasis from breast cancer predominantly rely on immunodeficient hosts inoculated with osteolytic human breast cancer cell lines, limiting the study of immune-dependent mechanisms of bone remodeling. Here we describe the development and characterization of an immunocompetent, syngeneic osteoblastic bone metastasis model using intratibial injection of PyMT-CK(OB), a luciferase-expressing derivative of the MMTV-PyMT mammary carcinoma cell line, in FVB/N mice. PyMT-CK(OB) cells produced detectable bioluminescent signal after intratibial injection, enabling longitudinal monitoring of tumor progression. Micro-computed tomography (microCT) revealed significant increases in trabecular bone volume fraction and trabecular number at three and four weeks post-injection, consistent with osteoblastic remodeling. Histological analysis confirmed dense bone lesion formation in tumor-bearing bones. Critically, this osteoblastic phenotype was entirely absent in immunodeficient NOD SCID hosts, despite robust tumor growth, supporting a role for immune competence in tumor-induced bone formation. Loss of bioluminescent signal in immunocompetent mice reflected either immune pressure on reporter gene expression or limited space for cancer cell expansion in the bone, rather than tumor regression or hypoxia, as confirmed by hypoxia imaging and histological endpoint analysis. In contrast, a second PyMT cell subline, PyMT-CF, maintained sustained bioluminescent signal and produced predominantly osteolytic lesions, providing a complementary syngeneic model of osteolytic disease from the same parental background. In vitro hydrogel coculture experiments and protein array analysis of conditioned media revealed that the PyMT sublines have differing impact on MC3T3 osteoblast mineralization, identifying candidate mediators of divergent bone remodeling phenotypes. R7 mammary carcinoma cells derived from MMTV-RON transgenic mouse mammary tumors did not induce measurable bone remodeling under equivalent experimental conditions. Together, these models provide a validated, immunologically intact framework for studying the mechanistic basis of osteoblastic bone metastasis and evaluating therapeutic interventions targeting the tumor-bone microenvironment.

Purpose: The Fracture Risk Assessment Tool (FRAX) excludes objective skeletal muscle health and genetic variables. We evaluated the prognostic associations of handgrip-defined probable/possible sarcopenia and genome-wide polygenic scores (GPS) with 10-year fracture risk, and their incremental predictive value beyond FRAX across racial/ethnic groups and GPS strata. Methods: We analyzed 2,051 postmenopausal women from the Women's Health Initiative. Race-specific analyses focused on Black, Hispanic, and White participants (n=2,009), excluding American Indian/Alaska Native and Asian/Pacific Islander individuals due to sparse fracture events. Sarcopenia status was operationalized by low handgrip strength alone via EWGSOP2 (<16.0 kg) and AWGS 2025 (<18.0-20.0 kg) criteria. Fine-Gray models estimated subdistribution hazard ratios (sHR), treating death as a competing risk. Predictive performance at 10 years was assessed using time-dependent AUC, Brier scores, and decision curve analysis (DCA). Results: Handgrip-defined probable or possible sarcopenia prevalence was 4.4% (EWGSOP2) and 6.4% (AWGS 2025). Black women demonstrated lower risk for major osteoporotic fractures (MOF) (adjusted sHR=0.19, 95% CI: 0.08-0.48) and hip fractures (adjusted sHR=0.07, 95% CI: 0.01-0.52) compared to White women. Neither sarcopenia status nor high GPS showed statistically significant independent associations with fractures after FRAX adjustment. Adding sarcopenia status to baseline FRAX (AUC: 0.71 for MOF; 0.69 for hip) yielded near-identical AUCs, Brier scores, and within-sample net benefit. Conclusion: Handgrip-defined probable/possible sarcopenia and current GPS do not provide independent or incremental predictive value beyond the clinical FRAX framework within this genomic sub-sample of older women.

Spinal cord injury (SCI) causes rapid and severe bone loss in the paralysed lower limbs, particularly at the distal femur and proximal tibia, where fragility fracture risk is high. In vitro nanoscale vibration at 1 kHz has been shown to promote osteogenic differentiation and inhibit osteoclastogenesis, suggesting potential as a targeted mechanical intervention. This study aimed to develop and evaluate a wearable device for delivering and monitoring localised nanovibration at the distal femur in individuals with SCI. The device delivered continuous sinusoidal nanoscale stimulation at 1 kHz via a bone-conduction transducer, with an opposing accelerometer used to monitor transmitted vibration in real time. Design and target-site selection were refined through two healthy-volunteer investigations comparing the distal femur, proximal tibia, and distal tibia. Bovine femur experiments characterised vibration transmission under controlled benchtop conditions. Preliminary repeated-use feasibility was assessed in one individual with motor-complete SCI. Healthy volunteer testing showed that although the ankle initially produced the highest transmitted amplitudes, these were highly variable, and positioning was inconsistent. Within the knee region, the distal femur provided the most practical and repeatable site for a wearable application. In bovine femur experiments, scanning laser vibrometry demonstrated measurable vibration on the condylar surface opposite the transducer, and depth-resolved measurements confirmed that nanoscale vibration remained detectable within bone. A gel interface layer reduced the transmitted amplitude. In the feasibility evaluation, 61 sessions were completed over 14 weeks, with logged accelerometry confirming repeated nanoscale vibration transmission. These findings establish feasibility and support further device optimisation and translational studies.

This protocol describes a standardized and reproducible minimally invasive approach for establishing mouse models of bisphosphonate-related osteonecrosis of the jaw (BRONJ) and osteoradionecrosis of the jaw (ORNJ). The method combines a unified low-trauma oral surgical procedure with disease-specific injury induction strategies to generate robust and clinically relevant models of jaw osteonecrosis. For BRONJ, systemic zoledronic acid administration is coupled with mandibular first molar extraction using tape-assisted mouth opening and customized bent micro-forceps, minimizing soft tissue damage and reducing procedural variability. For ORNJ, a customized lead-shielding platform enables precise, noninvasive mandible-targeted irradiation, producing reproducible bone injury while limiting off-target radiation exposure. Together, these complementary models provide a consistent and minimally invasive framework for investigating jaw osteonecrosis arising from distinct etiologies. The protocol supports comprehensive downstream analyses, including micro-computed tomography, histology, and immunofluorescence, and facilitates mechanistic studies of disease pathogenesis, bone regeneration, and therapeutic intervention.

PurposeEstrogen deficiency drives bone loss through interacting endocrine, oxidative, inflammatory and bone-remodeling disturbances. Ergothioneine (EGT) is a diet-derived thiol/thione antioxidant whose effects on the estrogen-deficient skeleton are unknown. We evaluated whether EGT, alone or combined with vitamin K2, vitamin D3 and magnesium L-threonate, attenuates the skeletal and systemic consequences of ovariectomy (OVX) in mice. MethodsForty-eight female C57BL/6J mice underwent sham surgery or OVX and received daily oral gavage for 12 weeks of vehicle, alendronate (1.53 mg/kg), EGT (30 mg/kg/day), EGT with vitamin K2 (40 {micro}g/kg/day) and vitamin D3 (500 IU/kg/day), or EGT with vitamin K2, magnesium L-threonate (350 mg/kg/day) and vitamin D3 (n = 5-6 analysed per group). Outcomes included the uterine index, tibial micro-computed tomography, distal-femoral histology, and serum bone turnover markers (CTX-I, PINP, osteocalcin), sex hormones, TNF-, IL-6, SOD and MDA. OVX lowered the uterine index and induced tibial trabecular deterioration, with increased CTX-I, decreased PINP and osteocalcin, elevated TNF- and IL-6, reduced SOD and increased MDA (all P < 0.01 vs sham). Alendronate restored tibial micro-CT bone-volume fraction (BV/TV) and trabecular number (P < 0.01 vs OVX). The EGT-based regimens did not significantly restore tibial micro-CT BV/TV, trabecular thickness or trabecular number (all P > 0.05 vs OVX), but significantly increased trabecular area on distal-femoral histology (OVX 7.6% vs 14.2-15.0% across regimens; P < 0.05 vs OVX) and lowered CTX-I, TNF-, IL-6 and MDA while raising SOD and partially restoring PINP and osteocalcin (P < 0.05-0.01 vs OVX). Because the histological and micro-CT endpoints were assessed at different skeletal sites, structural interpretation is cautious. Apparent increases in serum estradiol were assay-dependent and are regarded as exploratory. Ergothioneine-based nutritional regimens improved the systemic oxidative, inflammatory and bone-turnover environment of estrogen-deficient bone loss and preserved distal-femoral trabecular area on histology, although tibial three-dimensional microarchitecture by micro-CT was not restored. Because the histological and micro-CT endpoints were assessed at different skeletal sites, the structural interpretation is necessarily cautious. These findings support further evaluation of EGT as a dietary adjunct, with mechanistic and dose-optimization studies warranted.

BackgroundPalliative radiation therapy (RT) for metastatic spine disease significantly increases the risk of vertebral fractures. However, the temporal mechanisms underlying radiation-induced vertebral bone fragility remain poorly understood. ObjectiveTo evaluate the longitudinal effects of a single high-dose irradiation, simulating palliative RT, on vertebral bone mechanical, architectural, and compositional properties in a healthy, skeletally mature rat model. MethodsThirty-one male Sprague Dawley rats received a single 15 Gy lumbar spine irradiation (IR). L4 vertebrae were assessed across all groups (irradiation: 7, 14, and 28 days post-IR, controls: at 0 and 28 days post-IR) for compressive strength and stiffness, micro-CT-derived bone composition and trabecular indices, serum bone turnover markers (NTX and BAP) and advanced glycation endproducts (AGEs). ResultsIrradiation induced progressive deterioration of vertebral bone mechanical properties, with strength decreasing up to 44% and stiffness up to 38% by 28 days post-IR, compared to 0- day controls. Trabecular bone exhibited reduced BMD, BV/TV, and Tb.N with increased Tb.Sp, a shift toward a more rod-like structure. Early post-IR changes suggested disrupted bone remodeling, characterized by elevated NTX and AGEs, but decreased BAP. Multivariable regression demonstrated that Tb.Th and AGEs were independent predictors of stiffness, collectively explaining 61% of its variance. DiscussionHigh-dose irradiation induces sustained temporal degradation of vertebral mechanical properties driven by both trabecular architectural deterioration and alterations in bone matrix quality. Measures of bone composition and non-enzymatic bone turnover suggest this early damage was driven by disruption of bone cellular homeostasis, favoring increased resorption over formation. These findings support that radiation impairs both structural integrity and pre-yield mechanical behavior, providing mechanistic insight into the elevated fracture risk observed clinically after irradiation for metastatic spine disease. Lay summaryThis study used a rat model to mimic palliative radiation therapy for cancer that has spread to the spine and evaluated the changes in bone quality up to 28 days post-therapy. We found that irradiation progressively weakened the structural integrity and composition of the bones in the spine and disrupted the normal balance of bone breakdown and repair, leading to greater bone loss and fragility. Our findings provide insight into the increased risk of fractures observed in patients receiving radiation therapy to the spine and may support efforts to better protect bone health during treatment.

Low-intensity vibration (LIV) is a non-invasive mechanical stimulus capable of regulating skeletal adaptation and cellular signaling pathways involved in bone remodeling. Despite growing interest in LIV, substantial methodological heterogeneity persists in the selection of experimental vibration parameters such as frequency, expressed in Hertz (Hz) and intensity, defined as earth's gravitational field (g) (9.81 m/s2). Focusing on micro-computed tomography (CT) derived trabecular bone volume fraction (BV/TV) as the main outcome measure, this study sought to synthesize the effects of different LIV frequency and intensity on BV/TV in small rodents (mice and rats) as they remain as the most studied pre-clinical model. To accomplish this, we performed a systematic review searching for publications in English on PubMed, Web of Science, CINAHL, and Embase databases. Two independent investigators followed inclusion criteria to select only peer-reviewed studies with mature mice, using whole-body vibration experiments without other co-variables. We further restricted to include studies that analyzed non-fractured bones and compared pre- and post-intervention or control values. In addition to these core criteria, a detailed hierarchical screening framework was applied during full-text review. The two independent investigators extracted data independently and considered the characteristics of the study, animals' characteristics, intervention characteristics, and results. For this study we considered load-bearing hindlimbs, femur and tibia, separately but did not include vertebrae in the analysis. A Bayesian network meta-analysis and a revised SYRCLE risk of bias (RoB) tool were used to evaluate the risk of bias across included studies. Seven studies met the inclusion criteria. Results showed that an LIV regime applied at 45Hz at 2g presented higher chances to increase trabecular BV/TV of the mouse tibia (estimated effect 3.22 [CrI 1.98, 4.45]), while LIV regimes applied to the femur at 90Hz and 1.4g (estimated effect 3.08 [CrI -1.99, 7.97]) present better chances to increase trabecular BV/TV results compared to other interventions but with no significant differences. Finally, we applied 45Hz at 0.2g LIV to 5 month old male C57BL/6 for 5 weeks (n=10/group) which showed significantly increased Trabecular Thickness (Tb.Th) for both the tibia (10%, p<0.01) and femur (17%, p<0.001), with the femur showing further increases in trabecular BV/TV (32%, p<0.05) compared to non-LIV controls. We conclude that changes in the microarchitectures of the tibia and femur respond differently to the same application of LIV (45Hz, 0.2g) in mice and rats.

Fracture nonunion remains a major cause of morbidity, yet patient-specific factors associated with impaired healing remain incompletely characterized. Anemia has been associated with adverse orthopaedic outcomes, but its relationship with fracture nonunion is poorly understood. We examined whether pre-fracture anemia, anemia burden, and clinically relevant anemia subtypes were associated with nonunion following tibial or femoral fractures. Using commercial and Medicare fee-for-service claims from 2016 through 2023, we identified adults aged 19 years or older with a tibial or femoral fracture, continuous enrollment during the preceding year and for at least six months after fracture, and no baseline cancer. Pre-fracture anemia was evaluated as any anemia, the number of distinct anemia diagnoses, and nutritional, hemolytic, aplastic, and other anemia subgroups. Nonunion occurring six to eighteen months after fracture was assessed using incidence rates and multivariable-adjusted hazard models. Among 326,673 adults, 149,704 had pre-fracture anemia and 176,969 did not. The crude incidence of nonunion was 42% higher among individuals with anemia than among those without anemia (incidence rate ratio, 1.42; 95% confidence interval, 1.32 to 1.53) and increased with greater anemia burden. After adjustment for demographic and clinical characteristics, including prior fractures at other anatomical sites, pre-fracture anemia remained associated with nonunion following tibial and femoral fractures, with hazard ratios of 1.83 (95% confidence interval, 1.54 to 2.18) and 1.38 (95% confidence interval, 1.26 to 1.50), respectively. Associations were also observed for nutritional and other anemias, whereas estimates for hemolytic and aplastic anemias were limited by few nonunion events. Within the femur, the association was strongest for distal fractures. These findings demonstrate that pre-fracture anemia is independently associated with nonunion. The increase in risk with greater anemia burden and findings across evaluable subgroups suggest that pre-fracture anemia may help identify patients at increased risk of impaired fracture healing.

Abstract Introduction: Proximal humerus fractures account for approximately 5-6% of all adult fractures and are primarily managed nonoperatively. Healing is conventionally monitored with radiographs, with radiopaque callus formation indicating healing. Visible radiographic callus appears weeks after biological union begins. Ultrasound provides a dynamic, radiation-free, and cost-effective method that can detect early callus formation before x-ray visibility. Although ultrasound has demonstrated utility for fracture healing in the clavicle and humeral shaft, its role in proximal humerus fractures remains unclear. Methods: This single-centre prospective study will be conducted in two phases. The pilot phase will measure inter-rater reliability for ultrasound detection of early callus formation at 2 and 4 weeks post-injury. Ten patients with proximal humerus fractures treated nonoperatively will undergo standardized anterior and lateral scans. Each patient will generate four saved images (short- and long-axis views), producing forty anonymized images independently reviewed by two raters. The prospective cohort phase will recruit approximately thirty additional patients. Results: Reliability will be quantified using Cohens kappa. A power calculation will be performed after pilot analysis. Results from the prospective cohort phase will help determine the association and predictive value of early ultrasound-detected bridging callus for radiographic and clinical union at three and six months. Patient reported outcome measures will be assessed using the Quick Disabilities of Arm, Shoulder and Hand (QuickDASH) questionnaire. Discussion: This study will develop and validate a standardized ultrasound protocol for assessing early fracture healing in proximal humerus fractures. By establishing both inter-rater reliability and predictive value, the findings may support ultrasound as a reproducible, radiation-free adjunct to conventional imaging and enable earlier identification of union status.

Distal radius fractures (DRFs) can delay return to activities of daily living and social participation because of postoperative pain, temporary joint immobilization, and limited wrist and forearm range of motion. The Ghost System developed at Saitama Prefectural University, Japan, combines visual action observation with tendon vibration stimulation and has shown potential as an adjunct to conventional rehabilitation. This Study Protocol describes a modified Ghost system intended to improve clinical implementation by replacing the head-mounted virtual reality display with iPad-based action observation and by using a wristband-type vibrator. This single-center, single-arm, open-label feasibility trial will enroll 10 adults after palmar locking plate fixation for DRF. The intervention will be delivered twice weekly during outpatient rehabilitation follow-up sessions from the early postoperative period (postoperative days 2-10 after enrollment) through the approved early postoperative rehabilitation period (generally up to postoperative week 8), in parallel with standard rehabilitation practices. Primary feasibility and preliminary clinical outcomes include device fit and acceptability, pain assessed using a 100-mm Visual Analog Scale, and wrist/forearm range of motion. Secondary implementation and safety outcomes include Disabilities of the Arm, Shoulder and Hand (DASH), Patient-Rated Wrist Evaluation (PRWE), Hand20 Questionnaire (HANDS-20), EuroQol 5 Dimensions 5 Levels (EQ-5D-5L), body ownership and hand-illusion questionnaires, setup time, setup errors, adherence, adverse events, and device incidents. We hypothesize that the modified Ghost system will be feasible and acceptable for early postoperative outpatient rehabilitation and will be delivered without serious device-related adverse events. Clinical outcomes will be summarized descriptively to inform a future controlled study rather than to establish efficacy.

Osteoporosis is a prevalent skeletal disorder characterized by deterioration of bone microarchitecture and loss of bone mineral density, leading to increased fracture risk and substantial health and economic burdens, particularly among older adults. Bone remodeling is orchestrated by a complex interplay of systemic and local regulators, among which vitamin D plays a central role in maintaining skeletal homeostasis. Although numerous studies have examined the effects of vitamin D on bone metabolism, outcomes have been inconsistent across populations, dosing regimens, and experimental models. To clarify the net skeletal impact of vitamin D, we investigated its effects in postmenopausal osteoporosis (PMO). Vitamin D (1,25-dihydroxyvitamin D3- active form of vitamin D) supplementation effectively prevented bone loss in ovariectomized mice, at both lower and higher concentrations. Mechanistically, vitamin D promoted osteoclast differentiation in vitro, consistent with its RANKL-dependent pro-osteoclastogenic activity, yet paradoxically conferred bone protection in vivo. This discrepancy was explained by vitamin Ds profound immunomodulatory effects, which reshaped both innate and adaptive immune responses to suppress osteoclast formation and function. Concurrently, vitamin D improved intestinal barrier integrity and restored gut microbial composition, thereby stabilizing the gut-immune-bone axis and reducing pro-resorptive inflammatory signaling. Together, these findings demonstrate that vitamin D prevents bone loss through the coordinated regulation of immune and gut homeostasis, reconciling its apparent pro-resorptive effects in vitro with its overall anti-resorptive outcomes in vivo. This integrated mechanism highlights immune-gut microbial modulation as a key mediator of vitamin D-induced bone preservation and supports the development of vitamin D as an immunotherapeutic adjunct for the prevention and management of PMO. Altogether, our findings for the first time dissect the paradox surrounding the osteoprotective property of vitamin D supplementation.

Skeletal muscle is a living, perfused soft tissue whose viscoelastic behavior is shaped by both voluntary contraction and hemodynamic state. However, the independent and superimposed contributions of contractile loading and blood flow restriction (BFR) have not been quantified simultaneously in real time. Twenty-six healthy adults underwent multi-frequency ultrasound time-harmonic elastography (THE, 60-80 Hz) of the vastus lateralis under six conditions: rest, 15% and 30% maximal voluntary contraction (MVC) before BFR, passive BFR after 4 min of cuff inflation, and 15% and 30% MVC shortly after cuff release. Shear wave speed (SWS), reflecting elasticity, and penetration rate (PR), reflecting inverse viscous damping, were extracted using the k-MDEV inversion algorithm. BFR significantly elevated SWS at all three contraction levels relative to the corresponding pre-BFR measurements (Holm-corrected p [&le;] 0.011; dz = 0.54-2.13). PR decreased during resting BFR (dz = 1.34, p < 0.001) and at 15% MVC after cuff release (dz = 0.94, p < 0.001), but not at 30% MVC (dz = 0.21, p = 0.294). BFR-related changes reduced the SWS-force slope by 14.5% and the PR-force slope by 40.7%. Men exhibited a greater BFR-induced increase in resting SWS than women. These findings show that THE can distinguish contractile and hemodynamic contributions to skeletal-muscle viscoelasticity and provide complementary information on elastic and dissipative tissue behavior in vivo.

Advanced footwear technology (AFT) has transformed competitive running, yet individual and sex-specific responses to different AFT models remain unclear, particularly near race pace. This study examined running economy (RE) and gait biomechanics in response to three top-tier AFT models (Shoe A: adidas Pro Evo 2; Shoe B: Nike Alphafly 3; Shoe C: On CloudBoom Strike 2) in 14 male and 12 female well-trained runners at sex-specific submaximal speeds (16 and 14 km{middle dot}h-{superscript 1}). RE, spatiotemporal, and joint kinematic/kinetic data were collected via indirect calorimetry, accelerometry, and three-dimensional motion capture with force platforms. RE was significantly lower in Shoe C than Shoe A (males: 2.1%; females: 1.4%) and Shoe B (males: 1.9%; females: 0.9%), with 73% of runners responding favourably to Shoe C, a more consistent response than previously reported. Despite being lightest, Shoe A produced the poorest RE, challenging conventional mass-economy assumptions. Biomechanically, Shoe C elicited greater impact magnitude, lower ankle quasi-stiffness, and greater ankle angular velocity during early stance. Female runners showed smaller RE improvements, potentially related to lower running velocity and body mass limiting midsole engagement. The most efficient AFT enabled these well-trained runners to be more spring-like through tolerating higher forces and faster angular velocities without greater demand on metabolic cost.

High-resolution 3D imaging is an important strategy for visualizing and analysing complex skeletal tissue architecture and the bone marrow microenvironment. However, multicolor immunolabeling and imaging of intact skeletal tissues are technologically challenging. The current immunolabeling and clearing methods for intact skeletal elements are very limited, time-consuming and generate low-resolution data or depend on the use of reporter mice. Here, we describe a protocol for efficient clearing and immunolabeling of intact calcified tissues that enables superfast, single-cell resolution, and quantitative 3D light-sheet imaging of intact skeletal elements and teeth. A key aspect of our protocol is the addition of a collagenase digestion step after fixation and decalcification. This step enhances antibody penetration, resulting in deep, comprehensive staining throughout immunostained bones and other calcified tissues. The protocol includes soft tissue removal, fixation, decalcification, bone dehydration, and bleaching, followed by antigen retrieval and permeabilization before the collagenase digestion step. This procedure is performed to prepare the samples for the tissue clearing process that improves bone tissue transparency prior to light-sheet imaging. The entire protocol, from bone collection to image analysis and quantification, takes about 4 days to complete, thus offering significant improvements over previous methods. This protocol is broadly applicable to the visualization of bone microstructure, bone marrow analysis, vascular and neural network mapping, and the study of signaling molecules in bone development and growth. The protocol requires experience with standard tissue processing and immunostaining techniques, and prior experience in tissue clearing and light-sheet imaging is beneficial but not essential. Key pointsO_LIA protocol for efficient clearing and immunolabeling of intact calcified tissues that enables superfast, high-resolution, and quantitative 3D imaging of various intact bones and teeth. C_LIO_LIThe entire protocol takes only 4 days to complete the comprehensive staining and perfect transparency throughout the intact bones, offering significant improvements over previous methods. C_LI Key referencesBiswas, L. et al. Cell 186, 382-397.e24 (2023): https://doi.org/10.1016/j.cell.2022.12.031

Purpose The application of machine learning (ML) to osteoporosis prediction has expanded rapidly, yet no comprehensive meta-analysis has synthesized the discriminative performance of these models across all ML categories, data types, and validation strategies. This systematic review and meta-analysis aimed to evaluate the diagnostic and predictive accuracy of ML and deep learning models for osteoporosis prediction in adult populations. Methods Systematic searches of PubMed, Embase, Web of Science, and IEEE Xplore were conducted for studies published between January 2020 and February 2026. Studies developing, validating, or applying ML models for predicting osteoporosis, low bone mineral density, or osteoporotic fractures in adults were included. Methodological quality was assessed using the Prediction Model Risk of Bias Assessment Tool (PROBAST). Area under the receiver operating characteristic curve (AUC) values were pooled using random-effects meta-analysis with logit transformation. Subgroup analyses were performed by data type, ML category, external validation status, and population type. The review followed PRISMA 2020 guidelines. Results Thirty-three studies were included in the qualitative synthesis and 27 in the meta-analysis. The pooled AUC was 0.879 (95% CI: 0.853 0.901), with substantial heterogeneity (I = 99.5%). Imaging-based models outperformed clinical data models (AUC = 0.905 vs. 0.872). Deep learning achieved the highest pooled AUC (0.909), followed by ensemble methods (0.874) and traditional ML (0.840). Externally validated models showed lower performance than internally validated ones (AUC = 0.868 vs. 0.897). PROBAST assessment rated 32 of 33 studies (97.0%) as low risk of bias, though this proportion should be interpreted cautiously given that PROBAST was designed for traditional prediction models and may not fully capture ML-specific sources of bias. Egger's test indicated significant publication bias (p < 0.001). Explainable AI methods were employed in 60.6% of studies, identifying age, body weight, and alkaline phosphatase as the most frequent top predictive features. Conclusions Machine learning models demonstrate overall good discriminative performance for osteoporosis prediction, albeit with substantial heterogeneity across studies (I = 99.5%), and show potential as complementary screening tools, particularly in settings with limited DXA access. Deep learning models applied to imaging data and ensemble methods using clinical variables achieved the strongest subgroup estimates. However, extreme heterogeneity, evidence of publication bias, and limited prospective validation warrant cautious interpretation of the pooled estimate. Future research should prioritise multi-centre external validation, standardised reporting following TRIPOD+AI guidelines, and prospective clinical trials to establish real-world clinical impact.

Multiple myeloma causes devastating osteolytic bone disease. Current antiresorptive therapies slow bone loss but fail to rebuild the skeleton. Consequently, patients continue to fracture and suffer the associated morbidity and mortality. Targeting the Wnt inhibitor sclerostin, with romosozumab, increases bone mass in osteoporosis but has not been leveraged in cancer. We hypothesised that romosozumab would safely restore bone mass in multiple myeloma. In a murine model of myeloma, romosozumab was safe, demonstrating no impact on tumour progression while significantly increasing bone density. We subsequently conducted a Phase IIa proof-of-concept study in 12 multiple myeloma patients refractory to bisphosphonate therapy. Romosozumab was safe, it was well-tolerated and did not promote clinical or clonal myeloma progression. Treatment induced an early, significant rise in serum bone formation markers whilst resorption remained unchanged. This was coupled with significant gains in bone mineral density throughout the skeleton. Additionally, we observed radiological evidence of repair to pre-existing osteolytic lesions and, critically, a reduction in the skeletal morbidity rate from 2.5 to 0.11 events per patient-year. Longitudinal single-cell transcriptomics revealed that romosozumab transiently reprograms the osteoblast lineage to upregulate matrix synthesis and mineralisation programmes. These findings demonstrate that sclerostin inhibition safely rebuilds bone, providing clinical and mechanistic rationale for further randomised studies to restore bone health in myeloma patients.

Background Alveolar bone assessment in periodontal practice relies on radiography and clinical probing, both of which have well-documented limitations in precision. Intraoral high-frequency ultrasonography (US) offers a radiation-free alternative with potential for sub-millimeter resolution, the validity and precision for detecting minute osseous changes have not been established. The purpose of this study was to evaluate the concurrent validity and measurement precision of intraoral US for detecting alveolar bone-level changes in patients undergoing crown lengthening and osseous surgery, thereby enabling its translation to monitor osseous changes in patients with periodontitis. Methods Ten patients (28 tooth sites) undergoing crown lengthening or osseous surgery at a USC Advanced Grad Perio clinic were enrolled in this prospective observational study. Distance from the cementoenamel junction (CEJ) to the Alveolar bone crest (ABC) was measured at pre- and post-operative time points using a 40 MHz handheld intraoral US transducer and, intraoperatively, by standardized clinical photography. Agreement was assessed by Pearson correlation and Bland-Altman analysis. Measurement precision was quantified using the standard error of measurement (SEM) and minimum detectable change (MDC). Results Preoperative agreement between methods was excellent (r = 0.977; Bland-Altman bias = -0.009 mm; 95% limits of agreement [LoA]: +-0.40 mm). Post-operative correlation remained strong (r = 0.912; bias = 0.123 mm; LoA: -0.85 to +1.10 mm). Both methods detected statistically significant post-surgical increases in the ABC-to-CEJ distance (p < 0.001), as anticipated. US demonstrated substantially superior precision: preoperative SEM 0.058 mm with US versus 0.128 mm clinically, yielding MDC values of 0.160 mm (US) versus 0.354 mm (clinical), providing a 2.2-fold precision advantage. Conclusions Intraoral US demonstrated strong concurrent validity with clinical photography and a reproducible precision advantage in detecting alveolar bone-level changes in patients with periodontitis. These findings support its clinical utility as a radiation-free, high-sensitivity bone monitoring tool. Larger longitudinal studies with CBCT validation are warranted.

Introduction Adolescent idiopathic scoliosis (AIS) requires frequent x-rays for management, exposing young patients to cumulative radiation risks. While radiation-sparing imaging modalities exist, access across the National Health Service (NHS) remains uneven and information given to patients is variable. This qualitative study investigated the systemic, geographic, and interpersonal dynamics of AIS imaging in England. Design This qualitative study employed in-depth semi-structured interviews with healthcare professionals (HCPs) from NHS paediatric spinal centres, patients aged 13 to 25 years old with AIS and parents/carers of young people with AIS. Setting England. Participants A total of 22 HCPs from 13/24 NHS paediatric spinal centres in England, 19 10-25 years with AIS and 11 parents/carers. Results Conventional x-ray remains the main imaging modality. Significant geographic inequality exists. The most commonly available radiation-sparing imaging modality available is the EOS system, which uses slot-scanning technology, is available at 7 centres in England, primarily in London imaging networks. Acquisition of EOS systems is currently driven by local charitable funding rather than a centralised strategy, with high capital and installation costs cited as primary barriers. Inconsistent knowledge of imaging within primary care and a lack of specialist expertise in local secondary care services led to diagnostic redundancy, gatekeeping, and low value inconsistent imaging. These systemic delays frequently closed the window for conservative treatments like bracing. A professional balancing act exists between the duty to inform and the desire to minimise patient anxiety. HCPs often use selective communication regarding radiation risks. Conversely, families demonstrate high relational trust with HCPs and low baseline knowledge of cumulative exposure, often viewing frequent imaging as a reassuring marker of clinical progress. In centres with EOS systems, clinicians felt empowered to lead proactive, transparent risk discussions. In standard X-ray settings, dialogue remains reactive and infrequent, leading to a reliance on implied rather than truly informed consent. Conclusions AIS imaging in England is variable. Geographic location dictates access to low-dose radiation technology and the quality of informed consent. Systemic inefficiencies and fragmented referral pathways contribute to diagnostic redundancy and delayed specialist care. National standardisation of clinical pathways, information provision and a centralised strategy for low-dose technology procurement are essential to eliminate structural inequalities and ensure equitable, transparent care for all patients.

Sutures are the primary sites of cranial bone growth, allowing the skull to accommodate the growing brain. External mechanical stimulus has been shown to delay suture fusion and induce tissue remodelling. Recent studies suggest that in vivo cyclic bone loading increased proliferation of mesenchymal stem cells (MSC) in the coronal suture. The overall aim of this study was to understand how many loading sessions (exposure-response) and how long after loading (time-course) did MSC proliferation increase in the coronal suture. In the exposure-response analysis, mice underwent 1, 3, or 5 loading sessions between Postnatal day 7 (P7) and P11, and in the time-course analysis, treated mice underwent 10 loading sessions between P7 and P21. Loading sessions were 10 minutes at a frequency of 1 Hz and a force of 10 g (0.1 N). The loading tip was positioned on the posterior aspect of the left frontal bone, dorsal to the coronal suture. The EdU marker shows a statistically significant increase in proliferation after one loading session and a decrease after three loading sessions. The PCNA marker shows a statistically significant increase after three and five loading sessions. The exposure-response analysis showed that when the results of both markers are combined, levels of proliferation cannot be interpreted until at least five loading sessions have been completed, after which a clear increase in proliferation was observed. In the time-course analysis, proliferation was highest immediately after the final treatment session and 24 hours after the final loading session the effects of mechanical bone loading gradually returned to baseline.

The clinical utility of monitoring longitudinal changes in musculoskeletal trajectories, including bone mineral density (BMD), muscle strength, height, and weight for fracture prediction, remains underutilized, as current gold-standard tools such as the Fracture Risk Assessment Tool (FRAX) rely solely on cross-sectional baseline data. This study aimed to determine whether a deep learning model integrating individualized musculoskeletal trajectories improves fracture prediction accuracy compared to established static benchmarks. We developed the Hybrid Trajectory-Based model (HyTrax), a Transformer-based deep learning model that encodes sequential measurements of hip and spine BMD, grip strength, height, and weight as temporal tokens, incorporating subject-specific slopes derived from linear mixed-effects models. The model was trained and internally validated in 27,512 postmenopausal women from the Women's Health Initiative (WHI) and externally evaluated in 1,193 participants from the Framingham Heart Study (FHS). In the WHI validation set, the HyTrax + FRAX (BMD) ensemble model achieved a time-dependent Area Under the Curve (AUC) of 0.85 for Major Osteoporotic Fracture, outperforming both the longitudinal Transformer alone (AUC = 0.80) and the standard FRAX-BMD model (AUC = 0.82). The HyTrax + FRAX (BMD) ensemble model demonstrated favorable discrimination and improved risk stratification (Net Reclassification Improvement +26.5%) in WHI. Evaluation in the FHS cohort demonstrated the transportability of the longitudinal embeddings, with the HyTrax + Baseline 2 ensemble model (integrating longitudinal embeddings with clinical risk factors, BMD, and grip strength) achieving an AUC of 0.74. Explainability analyses identified early longitudinal weight fluctuations and overall height loss trajectories as important predictors of future fracture risk, alongside static factors such as age and genetic predisposition. By leveraging individualized trajectories through deep sequential modeling with baseline FRAX probability, the HyTrax + FRAX (BMD) ensemble model improved fracture discrimination over static assessments, offering a framework for incorporating repeated clinical measures into fracture prediction.