title: Varus tibial joint line obliquity: a potential cause of femoral component malrotation.
abstract: In 60 consecutive total knee arthroplasties done in 52 patients with primary osteoarthritis and varus or neutral tibiofemoral alignment, the posterior condylar angle was calculated intraoperatively and averaged 3.98 degrees (range, 0 degrees-9 degrees). Eighteen knees had a posterior condylar angle value less than 3 degrees whereas 27 knees had a posterior condylar angle value of 5 degrees or greater. Final rotational alignment of the femoral component was set parallel to the transepicondylar axis. Only one of these 60 knees required a lateral retinacular release for proper patellar tracking during the knee arthroplasty. When compared with three previously defined angles measured on the radiographs taken preoperatively, only the tibial plateau-tibial shaft angle values were correlated significantly with the value of the posterior condylar angle. As the tibial varus joint line obliquity increased, there was a distinct tendency for the transepicondylar axis to be rotated more externally relative to the posterior condylar axis. This variance suggests that the use of the posterior condylar axis as a rotational reference is inappropriate in many knees with arthritis with varus or neutral tibiofemoral alignment. In particular, varus tibial joint line obliquity of more than 4 degrees increases the likelihood of femoral component malrotation when the posterior femoral condyles are used to reference femoral component rotation.
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic and Mayo Foundation, Rochester, MN 55905, USA.
authors.forename: M W
authors.initials: MW
authors.lastname: Pagnano
authors.forename: A D
authors.initials: AD
authors.lastname: Hanssen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee; D005260:Female; D005269:Femur / Q000502:physiology; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000503:physiopathology* / Q000601:surgery*; D011475:Prosthesis Failure; D012399:Rotation; D013977:Tibia / Q000502:physiology