HSS Presents New Biomechanics Research at 2022 AAOS Annual Meeting
At this year’s American Academy of Orthopaedic Surgeons annual meeting, which is being held March 22 to 26 in Chicago, HSS presented new research related to biomechanics and orthopedic surgery, highlighting the unique relationship surgeons have with the engineers to promote the highest quality in patient care and advancing joint replacement for the future.
Three studies focus on how to optimize total knee arthroplasty (TKA) surgery using biomechanics and computer modeling, while another study discusses how three-dimensional (3-D) modeling can improve total hip arthroplasty (THA).
What follows are some highlights from the meeting:
Undersizing Tibial Baseplates in Cementless TKA Has Negative but Small Impact for Bone–Implant Interaction: A Computational Biomechanical Study
Computational biomechanical modeling is useful for taking a closer look at how making changes to orthopedic surgery techniques affects patient outcomes. A study led by Fernando J. Quevedo-González, PhD, assistant scientist in the Department of Biomechanics at HSS, and HSS hip and knee surgeon Jonathan M. Vigdorchik, MD, used these kinds of models to determine how best to minimize the risk of complications in cementless TKA. The model was developed using preoperative scans from 12 female patients about to undergo robotic TKA and was used to ask questions about how sizing the tibial baseplate (the metal part of the prosthesis that connects to the shin bone) affects outcomes. The investigators found that, in general, decreasing the size of the baseplate increased the amount of bone at risk of failure, but this risk was small compared with normal variability of bone quality among patients and how their individual knee joints were loaded as they used their knee in performing activities of daily living. Based on this result, they concluded that baseplate undersizing can be done to optimize the placement of the tibial component of the TKA without increasing the risk of bone failure.
Posterior Tibial Slope in Total Knee Arthroplasty: The Transmalleolar Sagittal Axis Underestimates Slope Compared to Traditional Intramedullary Axis
The tibial slope, one of multiple angles used to place a TKA, defines how the tibial component meets the knee and impacts the knee’s ability to bend and the strain that’s put on the ligaments throughout range of motion. A study led by HSS hip and knee surgeons Brian P. Chalmers, MD, and Steven B. Haas, MD, looked at how robotics and computer navigation influence the tibial slope in TKA. Historically, knee implants were designed using what is called the intramedullary axis to measure the tibial slope, but technology-assisted knee replacement operations determine the slope in a different way. The investigators retrospectively reviewed preoperative CT scans from 40 TKA procedures and reconstructed the 3-D geometry of the tibia and fibula to determine the slope based on the intramedullary axis. They determined that in many cases, the alternate calculation of the slope used in technology-assisted procedures resulted in a different slope in the newly implanted knee. This difference could have a negative effect on the knee’s movement and mechanics, suggesting that as more procedures are performed using robotic-assisted technology, the need to re-think implant designs to incorporate these changes is likely.
Authors: Brian P. Chalmers, MD, Fernando J. Quevedo-González, PhD, Michael P. Ast, MD, Steven B. Haas, MD.
The Initial Fixation of Cementless TKA Is Associated with the AP Translation During Gait: A Computational Study
The two main goals of TKA surgery are restoring the motion of the knee joint to as close to a native knee as possible, and ensuring that the implant is properly attached to the bone so that it lasts as long as possible and does not loosen. A novel study led by Jonathan Glenday, PhD, a postdoctoral fellow, and Fernando J. Quevedo-González, PhD, assistant scientist, both in the Department of Biomechanics at HSS, looked at the intricate relationship between attachment to the bone and joint motion, and how these two aspects of joint mechanics are related. The investigators used a computational model that included gait mechanics and anatomic information from CT scans to look at whether the anterior-posterior (AP) translation (front-to-back movement) of the femur with respect to the tibia while walking was correlated with bone-implant micromotion after surgery. Based on their models, they determined that the AP translation significantly related to the peak micromotion throughout gait, especially in the lateral portion of the knee; greater AP translation resulted in larger micromotions. This study highlights the connection between joint-level mechanics and fixation-level mechanics in TKA surgery and is the first time researchers at HSS have been able to look at both in tandem.
Authors: Jonathan Glenday, PhD, Peter K. Sculco, MD, Jonathan M. Vigdorchik, MD, Joseph D. Lipman, MS, Cynthia Kahlenberg, MD, David J. Mayman, MD, Timothy M. Wright, PhD, Fernando J. Quevedo-González, PhD.
Three-Dimensional Functional Impingement in Total Hip Arthroplasty: A Biomechanical Analysis
Impingement after THA can lead to pain and, in the worst case, a dislocation of the prosthesis. Offset of components, which is related to the width of the hip, directly affects the impingement of the hip after surgery. Surgeons have multiple ways to alter offset during THA surgery; however, these alterations have only been studied in two dimensions. A team led by HSS hip and knee surgeon Jonathan M. Vigdorchik, MD, and former clinical fellow Eytan Debbi, MD, PhD, used 3-D models created from pre- and postoperative CT scans of 16 patients who underwent the procedure to retrospectively analyze the relationship between offset and impingement. They compared cup/liner (acetabular) offset to head/stem (femoral) offsets and looked at the effects that these configurations had on the patient’s range of motion and incidence of impingement after surgery. The investigators found that in all cases, increasing the offset reduced the amount of impingement, and increased the full range of motion of the hip. Acetabular offsets had greater impact than femoral offsets in the range of motion because they affect the offset of the center-of-rotation.
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