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URL: https://pubmed.ncbi.nlm.nih.gov/41928875/

⇱ Artificial intelligence-driven assessment of sarcopenia in orthopedic geriatrics: technical progress and clinical implications - PubMed


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Abstract

Sarcopenia, a progressive skeletal muscle disorder characterized by the loss of muscle mass and function, represents a significant challenge in geriatric orthopedics, with prevalence reaching as high as 48.7% in surgical populations. It is strongly associated with increased risks of falls, secondary fractures, postoperative complications, and mortality. Despite its clinical importance, traditional diagnostic methods like Dual-energy X-ray Absorptiometry (DXA) and Bioelectrical Impedance Analysis (BIA) are often impractical in acute orthopedic settings due to patient immobilization, positioning constraints, and postoperative fluid imbalances. This narrative review aims to summarize how the emergence of artificial intelligence (AI), particularly deep learning, addresses these gaps by enabling automated, high-throughput opportunistic screening from routine clinical imaging. Convolutional neural networks achieve expert-level segmentation of muscle quantity and quality, with Dice similarity coefficients often exceeding 0.94. AI-derived metrics serve as robust independent predictors for adverse surgical outcomes, including prolonged length of stay and infection, as well as functional recovery and one-year mortality. By integrating these metrics into Clinical Decision Support Systems (CDSS) and Electronic Medical Records (EMR), AI facilitates a paradigm shift from reactive fracture management to proactive prevention through automated "zero-click" alerts and multidisciplinary intervention pathways. While significant challenges regarding technical standardization, biological variability, and model interpretability persist, AI-driven assessment is transforming geriatric orthopedic care from subjective evaluation toward precise, objective quantification.

Keywords: artificial intelligence; clinical decision support systems; deep learning; geriatric orthopedics; opportunistic screening; osteosarcopenia; sarcopenia.

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Conflict of interest statement

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

👁 Figure 1
Figure 1
Pathophysiological mechanisms of bone-muscle “crosstalk” and the development of osteosarcopenia. This schematic illustrates the bidirectional biochemical signaling and shared systemic risk factors governing musculoskeletal homeostasis. Muscle tissue acts as an endocrine organ, releasing myokines such as irisin and fibroblast growth factor-2 (FGF-2) to promote bone formation, while bone-derived osteocalcin supports muscle anabolism. The disruption of this crosstalk, driven by chronic inflammation and oxidative stress, leads to a vicious “falls-fracture-disability” cycle.
👁 Figure 2
Figure 2
Workflow of the “zero-cost” AI screening strategy (target: individuals without existing imaging). This schematic illustrates the first-line screening approach detailed in Section 1.4. (A) Input: Readily available anthropometrics (Calf Circumference, Weight/BMI) and grip strength serve as zero-cost input variables. (B) Processing: Validated ML algorithms (e.g., Katano et al. and Buccheri et al. equations) integrate these inputs to predict muscle metrics. (C) Output: The model estimates Appendicular Skeletal Muscle Mass (ASM) with high accuracy relative to DXA. (D) Triage: Based on the estimate, “Low Risk” patients undergo routine monitoring, while “High Risk” patients are referred for advanced opportunistic CT assessment (see Figure 3), optimizing resource allocation.
👁 Figure 3
Figure 3
Technical panorama of the AI-based automated muscle assessment framework. The workflow illustrates a deep learning pipeline divided into three main stages: Input End: Medical imaging data, consisting of CT or MRI slices at varying vertebral levels (e.g., L3, L1, T12), serve as the input for the model. Processing End: A U-Net Convolutional Neural Network (CNN) architecture performs semantic segmentation. Through pathways of feature extraction, downsampling, upsampling, and localization, the network automatically isolates key muscle groups. The example shows the segmentation of Psoas (red), Erector Spinae (green), and Paraspinal (blue) muscles. Output End: The segmented data is transformed into multi-dimensional quantitative metrics. Quantity is assessed via Cross-Sectional Area (CSA) and Skeletal Muscle Index (SMI), calculated as CSA normalized by height squared (cm2/m2). Quality is evaluated through Hounsfield Unit (HU) value distribution analysis (distinguishing normal muscle from myosteatosis) and muscle fat content assessment. Note: While this framework achieves high-precision analysis for confirming sarcopenia, it is resource-intensive. Therefore, within the proposed stepwise diagnostic strategy, this comprehensive assessment is primarily indicated for opportunistic use (leveraging existing scans) or for “High-Risk” patients identified during first-line screening (as detailed in Figure 2), ensuring efficient healthcare resource allocation.
👁 Figure 4
Figure 4
Multi-scenario applications of AI-based opportunistic screening in geriatric orthopedics. This schematic illustrates the clinical utility of automated muscle analysis across three major orthopedic subspecialties using existing diagnostic imaging. Scenario A (Trauma & Hip Fracture): In the emergency setting, AI automatically assesses psoas muscle density from routine pelvic or abdominal CT scans. This quantitative data serves as a biomarker for frailty to predict risks of prolonged hospitalization and post-operative complications. Scenario B (Spine Surgery): AI-driven MRI analysis quantifies fatty infiltration (myosteatosis) within the multifidus muscles. This assessment is used to evaluate the risk of Failed Back Surgery Syndrome (FBSS) and guide surgical decision-making. Scenario C (Joint Replacement): Pre-operative thigh CT scans are utilized by AI to evaluate muscle quality and mass. These metrics provide a basis for personalized rehabilitation protocols and perioperative risk stratification for patients undergoing total hip or knee arthroplasty. These “opportunistic” workflows leverage existing imaging data to provide high-precision, automated risk assessment without requiring additional radiation exposure or clinical costs.
👁 Figure 5
Figure 5
Integrative mechanism of AI-based muscle assessment for clinical prognostic stratification. AI-Derived Muscle Profile (Input): Automated extraction of muscle quantity (SMI) and quality metrics (SMD, NAMA) serves as the foundational data. Core Mechanism: Predictive Modeling & Risk Stratification: Muscle biomarkers are integrated with clinical covariates through feature fusion. A risk scoring engine then stratifies patients into High (Red), Medium (Yellow), and Low (Green) risk tiers. Multi-dimensional Clinical Outcomes (Validation): The risk stratification predicts outcomes across three tiered endpoints: Tier 1 (Acute Surgical Impact), Tier 2 (Functional Trajectory), and Tier 3 (Survival), enabling personalized perioperative management.
👁 Figure 6
Figure 6
Current challenges and limitations in AI-driven sarcopenia assessment for geriatric orthopedics. Technical Bottlenecks: Large inter-scanner variability in HU values (7–56 HU, with shifts up to 79 HU) and differences in tube voltage, contrast timing, and reconstruction algorithms hinder unified diagnostic thresholds across vendors. Biological Variability: Muscle quantity, distribution, and fat infiltration differ by ethnicity, sex, and age, meaning population-specific calibration is required to avoid bias and misclassification. Implementation Hurdles: Integration of AI tools into routine PACS/EMR workflows remains difficult, and the “black-box” nature of deep learning limits interpretability, clinical trust, and informed consent. Ethical and Legal Concerns: Opportunistic screening introduces challenges regarding incidental findings, liability, and malpractice responsibility when AI contributes to diagnostic errors.
👁 Figure 7
Figure 7
Future directions in AI-driven sarcopenia assessment. Multi-modal Fusion: Integration of imaging, clinical, and biochemical data for a holistic “Sarcopenia Index.” Longitudinal Monitoring: Tracking post-operative muscle changes and predicting rehabilitation trajectories via serial AI analysis. Point-of-Care AI: Rapid, bedside muscle screening and real-time monitoring using AI-enhanced portable ultrasound. Core Goal: Transitioning from reactive treatment to proactive, personalized musculoskeletal health management.

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