title: Distal femoral resection at knee replacement - the effect of varying entry point and rotation on prosthesis position.
abstract: Malalignment may contribute to early prosthesis failure through point loading and premature polyethylene wear. Femoral resection requires for distal planar resection contingent upon correct rotation and coronal alignment. Using a standard model, we have examined the influence of differing femoral entry points and rotations upon final femoral component positioning. A graphical method and navigation system independently quantified the individual and combined impact of these variables, in 3 planes. Nine permutations were assessed with reference to neutral rotation and a central entry point. The graphical results were corroborated by the navigation analyses. We found that external rotation and a superolateral entry point introduced the greatest error in final component positioning. We have identified a safe envelope for femoral rod positioning and recommend that the rotational alignment is determined before distal bone resection.
authors.affiliation: Newcastle Upon Tyne Hospitals NHS Trust & Newcastle University, The Freeman Hospital, Newcastle upon Tyne, United Kingdom.
authors.forename: Rajkumar
authors.initials: R
authors.lastname: Gangadharan
authors.forename: David J
authors.initials: DJ
authors.lastname: Deehan
authors.forename: Andrew W
authors.initials: AW
authors.lastname: McCaskie
mesh_terms: D053587:Arthrometry, Articular; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D005269:Femur / Q000601:surgery*; D006801:Humans; D007720:Knee Prosthesis; D008953:Models, Anatomic; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012399:Rotation; D025321:Surgery, Computer-Assisted / Q000379:methods*