Jean Brihault1, Alessandro Navacchia2,3, Silvia Pianigiani4, Luc Labey5,6, Ronny De Corte5, Valerio Pascale4, Bernardo Innocenti5,7. 1. Faculté de Médicine, Université F. Rabelais, Tours, France. 2. Department of Industrial Engineering, University of Bologna, Bologna, Italy. alessandro.navacchia@du.edu. 3. Computational Biomechanics Lab, University of Denver, 2390 S. York Street, Denver, CO, 80208, USA. alessandro.navacchia@du.edu. 4. IRCCS, Istituto Ortopedico Galeazzi, Milan, Italy. 5. European Centre for Knee Research, Smith&Nephew, Louvain, Belgium. 6. Mechanical Engineering Technology TC, Campus Geel, KU Leuven, Louvain, Belgium. 7. BEAMS Department, Université Libre de Bruxelles, Avenue Franklin Roosevelt, 50, Bruxelles, 1050, Belgium.
Abstract
PURPOSE: Most total knee arthroplasty tibial components are metal-backed, but an alternative tibial component made entirely of polyethylene (all-polyethylene design) exists. While several clinical studies have shown that all-poly design performs similarly to the metal-backed, the objective of this study is to perform a biomechanical comparison. METHODS: Loads, constraints and geometries during a squat activity at 120° of flexion were obtained from a validated musculoskeletal model and applied to a finite element model. Stresses in the tibia and micromotions at the bone-implant interface were evaluated for several implant configurations: (1) three different thicknesses of the cement penetration under the baseplate (2, 3 and 4 mm), (2) the presence or absence of a cement layer around the stem of the tibial tray and (3) three different bone conditions (physiological, osteopenic and osteoporotic bone). RESULTS: All-polyethylene tibial components resulted in significantly higher (p < 0.001) and more uneven stress distributions in the cancellous bone under the baseplate (peak difference: +128.4 %) and fivefold increased micromotions (p < 0.001). Performance of both implant designs worsened with poorer bone quality with peaks in stress and micromotion variations of +40.8 and +54.0 %, respectively (p < 0.001). Performance improvements when the stem was cemented were not statistically significant (n.s.). CONCLUSION: The metal-backed design showed better biomechanical performance during a squat activity at 120° of flexion compared to the all-polyethylene design. These results should be considered when selecting the appropriate tibial component for a patient, especially in the presence of osteoporotic bone or if intense physical activity is foreseen.
PURPOSE: Most total knee arthroplasty tibial components are metal-backed, but an alternative tibial component made entirely of polyethylene (all-polyethylene design) exists. While several clinical studies have shown that all-poly design performs similarly to the metal-backed, the objective of this study is to perform a biomechanical comparison. METHODS: Loads, constraints and geometries during a squat activity at 120° of flexion were obtained from a validated musculoskeletal model and applied to a finite element model. Stresses in the tibia and micromotions at the bone-implant interface were evaluated for several implant configurations: (1) three different thicknesses of the cement penetration under the baseplate (2, 3 and 4 mm), (2) the presence or absence of a cement layer around the stem of the tibial tray and (3) three different bone conditions (physiological, osteopenic and osteoporotic bone). RESULTS:All-polyethylene tibial components resulted in significantly higher (p < 0.001) and more uneven stress distributions in the cancellous bone under the baseplate (peak difference: +128.4 %) and fivefold increased micromotions (p < 0.001). Performance of both implant designs worsened with poorer bone quality with peaks in stress and micromotion variations of +40.8 and +54.0 %, respectively (p < 0.001). Performance improvements when the stem was cemented were not statistically significant (n.s.). CONCLUSION: The metal-backed design showed better biomechanical performance during a squat activity at 120° of flexion compared to the all-polyethylene design. These results should be considered when selecting the appropriate tibial component for a patient, especially in the presence of osteoporotic bone or if intense physical activity is foreseen.
Authors: Koji Totoribe; Etsuo Chosa; Go Yamako; Hiroaki Hamada; Koki Ouchi; Shutaro Yamashita; Gang Deng Journal: J Orthop Surg Res Date: 2018-05-16 Impact factor: 2.359