title: Peri-implant bone strains and micro-motion following in vivo service: a postmortem retrieval study of 22 tibial components from total knee replacements.
abstract: Biological adaptation following placement of a total knee replacements (TKRs) affects peri-implant bone mineral density (BMD) and implant fixation. We quantified the proximal tibial bone strain and implant-bone micro-motion for functioning postmortem retrieved TKRs and assessed the strain/micro-motion relationships with chronological (donor age and time in service) and patient (body weight and BMD) factors. Twenty-two tibial constructs were functionally loaded to one body weight (60% medial/40% lateral), and the bone strains and tray/bone micro-motions were measured using a digital image correlation system. Donors with more time in service had higher bone strains (p = 0.044), but there was not a significant (p = 0.333) contribution from donor age. Donors with lower peri-implant BMD (p = 0.0039) and higher body weight (p = 0.0286) had higher bone strains. Long term implants (>11 years) had proximal bone strains 900 µϵ that were almost twice as high as short term (<5 years) implants 570 µϵ. Micro-motion was greater for younger donors (p = 0.0161) and longer time in service (p = 0.0008). Increased bone strain with long term in vivo service could contribute to loosening of TKRs by failure of the tibial peri-implant bone.
authors.affiliation: Department of Orthopaedic Surgery, SUNY Upstate Medical University, Syracuse, New York.
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Mann
authors.forename: Mark A
authors.initials: MA
authors.lastname: Miller
authors.forename: Jacklyn R
authors.initials: JR
authors.lastname: Goodheart
authors.forename: Timothy H
authors.initials: TH
authors.lastname: Izant
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Cleary
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation*; D001835:Body Weight; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D009068:Movement; D013314:Stress, Mechanical; D013977:Tibia / Q000502:physiology*; D013997:Time Factors; D016474:Weight-Bearing
keywords: bone strain; knee replacement; loosening; micro-motion; postmortem