Original Article

Prevalence of low bone mineral density in robotic-assisted TKA candidates: insights from quantitative CT analysis

¹ Orthopaedics Surgery and Sports Medicine Department, FIFA Medical Center of Excellence, Croix-Rousse Hospital, Lyon University Hospital, 103 Grande Rue de la Croix-Rousse, 69004 Lyon, France
² Univ Lyon, Claude Bernard Lyon 1 University, IFSTTAR, LBMC UMR_T9406, 69622 Lyon, France
³ Department of Orthopedic Surgery and Traumatology, Cantonal Hospital Fribourg, University of Fribourg, Chemin des Pensionnats 2–6, 1708 Fribourg, Switzerland
⁴ Musculoskeletal Lab, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
⁵ Service of Orthopaedics and Traumatology, Department of Surgery, Ente Ospedaliero Cantonale (EOC), Via Tesserete 46, 6900 Lugano, Switzerland

^* Correspoding author: sebastien.lustig@chu-lyon.fr

Received: 20 July 2025
Accepted: 29 July 2025

Abstract

Introduction: Osteoporosis is a prevalent and often underdiagnosed condition that significantly increases the risk of fragility fractures. Dual-energy X-ray absorptiometry (DXA) is the standard diagnostic tool; however, many patients remain unscreened. Preoperative computed tomography (CT) scans obtained for robotic-assisted total knee arthroplasty (TKA) planning present an opportunity for opportunistic osteoporosis screening without additional radiation exposure. Methods: A retrospective observational study was conducted on 637 patients (307 males, 330 females) who underwent robotic-assisted TKA between January 2023 and December 2024. Preoperative CT scans were analyzed using quantitative computed tomography (QCT) software to determine T-scores, Z-scores, and percentage of bone mineral density (BMD) relative to a young-adult reference. Patients were categorized as normal (T-score ≥ −1.0), osteopenic (−2.5 < T-score < −1.0), or osteoporotic (T-score ≤ −2.5). Results: Among 597 patients with available T-score data, 41.0% were classified as normal, 32.3% as osteopenic, and 26.6% as osteoporotic. Notably, 37.0% of female patients were osteoporotic compared to 15.3% of male patients. Bone density parameters declined progressively with age, with females over 80 years exhibiting a mean T-score of −2.53 and BMD at 68.25% of the young-adult reference. Discussion: Opportunistic screening using preoperative CT scans in robotic-assisted TKA patients reveals a high prevalence of undiagnosed low BMD, particularly among elderly women. Integrating QCT analysis into the preoperative workflow may facilitate early identification of at-risk individuals, informing surgical planning and enabling timely interventions to improve bone health.