Jordan Broberg^1,2,3, Matthew Koff⁴, James Howard⁵, Brent Lanting⁵, Hollis Potter⁴, and Matthew Teeter^1,2,3,5
1Medical Biophysics, Western University, London, ON, Canada, ²Robarts Research Institute, London, ON, Canada, ³Lawson Health Research Institute, London, ON, Canada, ⁴Radiology and Imaging, Hospital for Special Surgery, New York, NY, United States, ⁵Surgery, Western University, London, ON, Canada

This prospective evaluation of cementless total knee replacement tibial baseplate fixation using RSA and MRI at paired time points identified a stabilization of migration and mostly normal integration of the bone-implant interface by 3 months post-operation. A potential relationship between RSA migration magnitude and the evaluated bone-implant interface supports the use of MRI as a tool for evaluating implant fixation.

Douglas L Handley¹, Joseph Y Tang¹, Andrea M Spiker², and Donna G Blankenbaker^1
1Radiology, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States, ²Orthopedic Surgery, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States

After acetabular labrum repair an intact repair, labrum re-tear, adhesions, and capsular disruption can have variable appearance on MRI. Some signs have been described as evidence of labral re-tear and adhesions. We retrospectively evaluated 25 hip MRIs in patients who later underwent revision arthroscopy utilizing these signs. Results were compared to arthroscopic findings. Fluid signal within the labrum demonstrated a high specificity for re-tear. Signs of adhesion were often identified accurately but could be imitated by synovitis. Capsular disruption was also identified with high sensitivity.  

Matthew F. Koff¹, Elexis Padgett², David Landy², Peter Sculco³, Thomas Sculco³, Timothy Wright², and Hollis G. Potter^1
1Department of Radiology and Imaging, Hospital for Special Surgery, New York, NY, United States, ²Department of Biomechanics, Hospital for Special Surgery, New York, NY, United States, ³Department of Orthopaedic Surgery, Hospital for Special Surgery, New York, NY, United States

Many patients are satisfied following total knee arthroplasty (TKA) surgery, but post-operative challenges occur. This study evaluated synovial reactions in patients with TKA and related pre-operative MRI findings to direct evaluation of retrieved tibial polyethylene liners from revision surgery. Patients with synovial response of 'arthrofibrosis' had less damage to the tibial insert than patients with a synovial response of 'polymeric'. MRI was able to distinguish specific synovial responses directly to clinically confirmed arthrofibrosis and aseptic loosening.

Kevin Koch¹, Robin Ausman¹, John Neri², Hollis Potter², and Matthew Koff^2
1Radiology, Medical College of Wisconsin, Milwaukee, WI, United States, ²Radiology and Imaging, Hospital for Special Surgery, New York City, NY, United States

In this exploratory study, radiomic measures were computed across radiologist-segmented image patches within 3D-MSI STIR images collected on symptomatic total hip replacements (THR).  Utilizing radiologist classifications of normal, infection, polymeric wear, or metallosis debris for each image patch, principle-component based cluster analysis was deployed to visualize and estimate radiomic distinctions between different soft-tissue pathology classifications.   The study results offer insights to future studies seeking to utilize quantitative MR to characterize and classify soft-tissue complications near THR. 

Sara E. Sacher¹, John P. Neri¹, Madeleine A. Gao¹, Hollis G. Potter¹, and Matthew F. Koff^1
1Department of Radiology, Hospital for Special Surgery, New York, NY, United States

The infrapatellar fat pad (IPFP) has been implicated as a source of pain after total knee arthroplasty (TKA), but regions close to metallic implants are susceptible to metal artifacts in MRI. Multi-acquisition variable-resonance image combination (MAVRIC) based T2 mapping technique can mitigate these artifacts. The goal of this study was to evaluate how T2 values of the IPFP vary with the degree of IPFP scarring. T2 values were shorter and displayed a wider range for individuals with more severe scarring. MAVRIC T2 mapping may be used as a quantitative biomarker of IPFP scarring.

Edward J Peake^1,2, Stefan Kluzek^3,4, Dorothee Auer^1,2, and Maja Radojčić^3,5
1NIHR Nottingham Biomedical Research Centre, University of Nottingham, Nottingham, United Kingdom, ²Radiological Sciences, University of Nottingham, Nottingham, United Kingdom, ³Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, United Kingdom, ⁴Department of Sports Medicine, University of Nottingham, Nottingham, United Kingdom, ⁵Centre for Sport, Exercise and Osteoarthritis Research Versus Arthritis, University of Oxford, Oxford, United Kingdom

Pain is a hallmark of knee osteoarthritis, a chronic condition with considerable health and socio-economic burden. Phenotyping this heterogeneous disease is a step towards improved and personalised treatment, and long-term pain phenotypes based on latent class trajectory analysis and knee MRI may facilitate it. In this study, we aimed to examine the correlation between baseline knee cartilage MRI features with established 9-year pain trajectories. Using data from the Osteoarthritis Initiative (n = 9385, 9-year follow-up), we demonstrated a weak correlation between knee cartilage, pain scores and pain trajectories and significant differences in cartilage radiomics between the knee pain trajectories.     

Jia Ying¹, Keyan Yu², Tianyun Zhao¹, Xiaodong Zhang², and Chuan Huang^1,3
1Biomedical Engineering, Stony Brook University, Stony Brook, NY, United States, ²Medical Imaging, The Third Affiliated Hospital of Southern Medical University – Guangdong Academy of Orthopedics, Guangzhou, Guangdong, China, ³Radiology, Stony Brook Medicine, Stony Brook, NY, United States

The infrapatellar fat pad (IPFP) plays an important role in the incidence of knee osteoarthritis (OA). However, whether the IPFP can serve as an independent biomarker for OA development is yet unknown. Radiomics is a powerful tool that can extract high-dimensional quantitative features for clinical outcomes. In this work, we proposed a prediction model for incident radiographic knee OA (iROA), using radiomic features of the IPFP, one year prior to diagnosis. The prediction performance was assessed, and our results from 604 knees demonstrated that MR-based radiomic features from the IPFP are predictive of iROA.

Janelle Baker¹, James MacKay², Feliks Kogan³, and Lauren Watkins^3,4
1Biomechanical Engineering, Stanford University, Stanford, CA, United States, ²Radiology, Cambridge University, Cambridge, United Kingdom, ³Radiology, Stanford University, Stanford, CA, United States, ⁴Steadman Philippon Research Institute, Vail, CO, United States

Hybrid [¹⁸F]sodium fluoride PET-MRI was used to evaluate the relationship between the bone metabolic response to exercise and joint changes over two years in osteoarthritic (OA) knees, including changes in cartilage T2 relaxation times as well as structural changes in bone and cartilage. Regions in OA knees that experienced structural changes over two years had increased PET metabolic bone response to exercise compared to regions that did not. Bone response to exercise may be a useful metric to predict joint changes in OA.