title: Does Maximal External Tibial Component Rotation Influence Tibiofemoral Load Distribution in the Primary Knee Arthroplasty Setting: A Comparison of Neutral vs Maximal Anatomical External Rotatory States.
abstract: Tibial component rotation at time of knee arthroplasty can influence conformity, load transmission across the polyethylene surface, and perhaps ultimately determined survivorship. Optimal tibial component rotation on the cut surface is reliant on standard per operative manual stressing. This subjective assessment aims to balance constraint and stability of the articulation through a full arc of movement.
  
  
  
  Using a cadaveric model, computer navigation and under defined, previously validated loaded conditions mimicking the in vivo setting, the influence of maximal tibial component external rotation compared with the neutral state was examined for changes in laxity and tibiofemoral continuous load using 3D displacement measurement and an orthosensor continuous load sensor implanted within the polyethylene spacer in a simulated single radius total knee arthroplasty.
  
  
  
  No significant difference was found throughout arc of motion (0-115 degrees of flexion) for maximal varus and/or valgus or rotatory laxity between the 2 states. The neutral state achieved equivalence for mediolateral load distribution at each point of flexion. We have found that external rotation of the tibial component increased medial compartment load in comparison with the neutral position. Compared with the neutral state, external rotation consistently effected a marginal, but not significant reduction in lateral load under similar loading conditions. The effects were most pronounced in midflexion.
  
  
  
  On the basis of these findings, we would advocate for the midtibial tubercle point to determine tibial component rotation and caution against component external rotation.
authors.affiliation: Newcastle Surgical Training Centre Research Unit 1, Freeman Hospital, Newcastle upon Tyne, England, United Kingdom.
authors.forename: William A
authors.initials: WA
authors.lastname: Manning
authors.affiliation: Newcastle Surgical Training Centre Research Unit 1, Freeman Hospital, Newcastle upon Tyne, England, United Kingdom.
authors.forename: Kanishka M
authors.initials: KM
authors.lastname: Ghosh
authors.affiliation: School of Biology, University of Newcastle upon Tyne, England, United Kingdom.
authors.forename: Alasdair P
authors.initials: AP
authors.lastname: Blain
authors.affiliation: Department of Orthopaedic Surgery, University Hospital of North Durham, England, United Kingdom.
authors.forename: Lee M
authors.initials: LM
authors.lastname: Longstaff
authors.affiliation: School of Biology, University of Newcastle upon Tyne, England, United Kingdom.
authors.forename: Steven P
authors.initials: SP
authors.lastname: Rushton
authors.affiliation: Newcastle Surgical Training Centre Research Unit 1, Freeman Hospital, Newcastle upon Tyne, England, United Kingdom.
authors.forename: David J
authors.initials: DJ
authors.lastname: Deehan
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000379:methods*; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D020959:Polyethylene; D016059:Range of Motion, Articular; D012399:Rotation; D013977:Tibia / Q000601:surgery*
chemical_list: D020959:Polyethylene
keywords: contact force; kinematics; knee replacement; laxity; malrotation