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Session: Poster session 2 (Odd numbers)
Session starts: Friday 27 January, 10:00
Presentation starts: 10:00

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Periklis Tzanetis (University of Twente)
Kevin De Souza (Stryker)
René Fluit (University of Groningen)
Seonaid Robertson (Stryker)
Bart Koopman (University of Twente)
Nico Verdonschot (University of Twente; Radboud University Medical Center)

Abstract:
One of the challenges in robotic-assisted total knee arthroplasty (TKA) is to define the optimal implant position in order to achieve restoration of the premorbid joint state. The aim of this study was first to explore differences in tibiofemoral kinematics and ligament strains between arthritic knees and their premorbid reconstruction, and subsequently, to optimize the position of the femoral component in the implanted knee, thereby reproducing the premorbid kinematics as closely as possible. A template musculoskeletal cadaveric knee model was developed using a previously established methodology [1]. To personalize the model, a computed tomography (CT) image of a single patient with severe knee osteoarthritis was segmented using a CT-based statistical shape model (SSM) trained to identify the arthritic and premorbid femoral and tibial bone surfaces [2]; and a magnetic resonance imaging-based SSM was used to estimate the cartilage thickness from the segmented bones. A cruciate-retaining implant was mechanically aligned to the reconstructed premorbid knee. The femoral component’s position was varied from −6 to 6 mm for medial-lateral, anterior-posterior, and proximal-distal translations, −3° to 3° for flexion-extension, and −6° to 6° for varus-valgus and internal-external rotations, using the covariance matrix adaptation evolution strategy. Compared to the premorbid model, the mechanically implanted model predicted tibiofemoral kinematics with an average root-mean-square-deviation (RMSD) of 2.53±1.24 mm and 2.45±0.98°. We found an average RMSD of 0.95±0.31 mm for translations and 1.35±0.01° for rotations between the premorbid and optimally aligned TKA model. The ligament strains reported deviations less than 1% over the extension range from 60° to 0°, except for the deep medial collateral ligament. We demonstrated the feasibility of closely reproducing premorbid kinematics in robotic-assisted TKA by optimizing the position of the femoral component with respect to mechanical alignment. Different surgical targets for robotic-assisted surgery can be further discussed, such as maximum joint stability in the mid-flexion range, balanced collateral ligaments, or reproducing the premorbid ligament strains. 1. Marra et al, J Biomech Eng, 137:020904, 2015. 2. Bowes et al, Ann Rheum Dis, 80:502-508, 2021.