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

作者：Brihault Jean; Navacchia Alessandro^*; Pianigiani Silvia; Labey Luc; De Corte Ronny; Pascale Valerio; Innocenti Bernardo

来源：Knee Surgery, Sports Traumatology, Arthroscopy, 2016, 24(8): 2550-2559.

DOI：10.1007/s00167-015-3630-8

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

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.
Loads, constraints and geometries during a squat activity at 120A degrees 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).
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.).
The metal-backed design showed better biomechanical performance during a squat activity at 120A degrees 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.

• 出版日期2016-8