title: How precise is the determination of rotational alignment of the femoral prosthesis in total knee arthroplasty: an in vivo study.
abstract: Correct rotation of the femoral component is critical in avoiding patellar instability in total knee arthroplasty. This study attempted to compare the precision of 4 commonly used methods (transepicondylar axis [TEA], 3 degrees external rotation [ER] from posterior condylar line [PCL], perpendicular cut to Leo Whiteside line [WSL], and balanced flexion gap [GAP]) in determining the rotational alignment of the femoral prosthesis in an in vivo setting. The ranges of error were as follows: (1) TEA, 28 degrees (17 degrees internal rotation [IR] to 11 degrees ER); (2) PCL, 27 degrees (13 degrees IR to 14 degrees ER); (3) WSL, 32 degrees (17 degrees IR to 15 degrees ER); (4) GAP, 26 degrees (14 degrees IR to 12 degrees ER). If an error of more than 5 degrees from neutral alignment is defined as an outlier, 56% in TEA, 72% in PCL, 60% in WSL, and 20% in GAP methods would fall in the outlier zone.
authors.affiliation: Department of Orthopaedics and Traumatology, Queen Mary Hospital, University of Hong Kong, Pokfulam, Hong Kong, China.
authors.forename: W P
authors.initials: WP
authors.lastname: Yau
authors.forename: K Y
authors.initials: KY
authors.lastname: Chiu
authors.forename: W M
authors.initials: WM
authors.lastname: Tang
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena; D005260:Female; D005269:Femur / Q000033:anatomy & histology* / Q000502:physiology / Q000601:surgery; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D007593:Joint Instability / Q000517:prevention & control; D007719:Knee Joint / Q000033:anatomy & histology* / Q000502:physiology / Q000601:surgery; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D017755:Prosthesis Fitting; D016059:Range of Motion, Articular / Q000502:physiology; D025321:Surgery, Computer-Assisted / Q000379:methods*