title: Errors in knee alignment using fixed femoral resection angles.
abstract: This study describes the variance within a representative population of total knee arthroplasty (TKA) patients to provide guidance in improving coronal alignment. The authors retrospectively reviewed 250 preoperative full-length standing radiographs in a consecutive series of TKAs performed by one surgeon. The distal femoral resection was templated on each radiograph to establish a femoral mechanical anatomical (FMA) angle to guide resection. Mean FMA angle was 5.35°, with a wide variation in FMA angle ranging from 1° to 10°. Slightly more than half (56%) of patients had either a 5° or 6° FMA angle, which is concerning for surgeons using a fixed resection angle. Ninety percent of patients measured within the 5°±2° window. Similarly, 90.7% of patients measured within the 6°±2° window. However, nearly 10% of patients (9.75%) had measurements greater than 7° or less than 3°. This study reports a wide variance in the angle of resection required to establish proper femoral mechanical alignment in TKA. Surgeons should be cognizant of the numerous variables that play a role in TKA and influence overall coronal alignment. Many of these variables can be fully assessed by evaluating full-length standing leg radiographs preoperatively. With experience, templating long-leg films can be reproducible and informative in preparing for each surgical procedure. Routine reliance on a single fixed resection angle could result in malalignment in 10% of patients.
authors.forename: Brian
authors.initials: B
authors.lastname: Curtin
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Fehring
authors.forename: Jessica
authors.initials: J
authors.lastname: Lauber
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D017760:Bone Malalignment / Q000209:etiology*; D005260:Female; D005269:Femur / Q000601:surgery*; D006801:Humans; D007719:Knee Joint / Q000601:surgery*; D008297:Male; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D011859:Radiography; D012189:Retrospective Studies