title: Primary stability of unicompartmental knee arthroplasty under dynamic compression-shear loading in human tibiae.
abstract: BACKGROUND
  The objective of our study was to evaluate the impact of a single- ("implant only") versus a double-layer ("implant & bone") cementing technique on the primary stability of unicompartmental tibial plateaus under dynamic compression-shear loading conditions in human tibiae.
  
  
  METHODS
  Twelve fresh-frozen human knees of a mean donor age of 72.3 years were used to perform medial UKA under a less invasive parapatellar surgical approach. The tibiae were divided into two groups of matched pairs based on comparable trabecular bone mineral density. To assess the primary stability, a new method based on a combination of dynamic compression-shear testing, kinematic analysis of the tibial plateau migration relative to the bone and evaluation of the cement layer by CT-scans and fragments cut through the implant-cement-bone interface in the frontal plane was introduced.
  
  
  RESULTS
  For the "implant only" cementation technique the mean load to failure was 2600 (SD 675) N and for "implant & bone" it was 2820 (SD 915) N. Between the final load level at failure and the bone mineral density a significant correlation was found for the groups "implant only" (r(s) = 0.875) and "implant & bone" (r(s) = 0.907).
  
  
  CONCLUSIONS
  From our observations, we conclude that there is no significant difference between a single- ("implant only") and double-layer ("implant & bone") cementing technique in the effect on the primary stability of unicompartmental tibia plateaus, in terms of failure load, correlation between final load at failure and bone mineral density, migration characteristics, cement layer thickness and penetration depth.
authors.affiliation: Aesculap AG Research & Development,Tuttlingen, Germany; Ludwig Maximilians University Clinic for Orthopaedic Surgery, Campus Grosshadern, Munich, Germany. Electronic address: thomas.grupp@aesculap.de.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Grupp
authors.forename: Matthias F
authors.initials: MF
authors.lastname: Pietschmann
authors.forename: Melanie
authors.initials: M
authors.lastname: Holderied
authors.forename: Christian
authors.initials: C
authors.lastname: Scheele
authors.forename: Christian
authors.initials: C
authors.lastname: Schröder
authors.forename: Volkmar
authors.initials: V
authors.lastname: Jansson
authors.forename: Peter E
authors.initials: PE
authors.lastname: Müller
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena; D001843:Bone Cements; D015519:Bone Density; D002484:Cementation / Q000379:methods*; D019245:Compressive Strength / Q000502:physiology; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000601:surgery; D008297:Male; D008875:Middle Aged; D011859:Radiography; D033081:Shear Strength / Q000502:physiology; D013977:Tibia / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery*; D016474:Weight-Bearing / Q000502:physiology
chemical_list: D001843:Bone Cements
keywords: Cementing technique; Dynamic compression-shear testing; Primary stability; Tibial plateau; Unicompartmental knee arthroplasty