All-polyethylene tibial components generate higher stress and micromotions than metal-backed tibial components in total knee arthroplasty

Jean Brihault, Alessandro Navacchia, Silvia Pianigiani, Luc Labey, Ronny de Corte, Valerio Pascale, Bernardo Innocenti

Research output: Contribution to journalArticle

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.

Original languageEnglish
JournalKnee Surgery, Sports Traumatology, Arthroscopy
DOIs
Publication statusAccepted/In press - May 10 2015

Keywords

  • All-polyethylene
  • Implant micromotions
  • Metal-backed
  • Tibial stresses
  • TKA

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Surgery

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