title: Favorable femoral component rotation achieved in severe varus deformity by using the gap-balancing technique.
abstract: BACKGROUND
  In a group of patients with severe varus deformity, this study used the gap-balancing technique and evaluated component rotation by using postoperative CT scans in order to determine whether a favorable axis could be achieved.
  
  
  METHODS
  Thirty-one patients (34 knees) with varus deformity of >15°, and 31 age-matched and sex-matched patients (36 knees) with varus deformity of ≤15° were enrolled. The transepicondylar axis and three degrees of external rotation off the posterior femoral condylar axis were lined out intraoperatively to compare measurements relative to the gap-balancing axis. Joint line elevations were determined, and the femoral component rotation was evaluated on postoperative CT scans.
  
  
  RESULTS
  Most of the study patients required stripping the capsule off the posteromedial distal femur and release of the medial collateral ligament. The difference in tibial joint line elevation was not significantly different (P=0.134). The two groups did not differ significantly in terms of the transepicondylar axis relative to the gap-balancing axis (P=0.166), the three degrees of external rotation off the posterior femoral condylar axis relative to the gap-balancing axis (P=0.913), the posterior condylar angles (P=0.218), and the prevalence of cases with a variation of ≤±3° in all alignment measurements. Comparable clinical outcomes were determined.
  
  
  CONCLUSIONS
  When the gap-balancing technique was used in the patients with severe varus deformity of >15°, over-release of the medial collateral ligament was avoided when tight posteromedial structures had been corrected first, and favorable femoral component rotations were achieved.
authors.affiliation: Department of Orthopaedic Surgery, The First Hospital of Jilin University, Jilin University, Changchun, China.
authors.forename: Yu-Hang
authors.initials: YH
authors.lastname: Gao
authors.affiliation: Department of Orthopaedic Surgery, The First Hospital of Jilin University, Jilin University, Changchun, China.
authors.forename: Shu-Qiang
authors.initials: SQ
authors.lastname: Li
authors.affiliation: Department of Orthopaedic Surgery, The First Hospital of Jilin University, Jilin University, Changchun, China.
authors.forename: Chen
authors.initials: C
authors.lastname: Yang
authors.affiliation: Department of Orthopaedic Surgery, The First Hospital of Jilin University, Jilin University, Changchun, China.
authors.forename: Jian-Guo
authors.initials: JG
authors.lastname: Liu
authors.affiliation: Department of Orthopaedic Surgery, The First Hospital of Jilin University, Jilin University, Changchun, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Dong
authors.affiliation: Department of Orthopaedic Surgery, The First Hospital of Jilin University, Jilin University, Changchun, China. Electronic address: dr.qixin@jlu.edu.cn.
authors.forename: Xin
authors.initials: X
authors.lastname: Qi
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D016022:Case-Control Studies; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery*; D056305:Genu Varum / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000601:surgery*; D011446:Prospective Studies; D012399:Rotation; D014057:Tomography, X-Ray Computed
keywords: Computed tomography; Femoral component rotation; Gap-balancing technique; Severe varus deformity; Stepwise release