title: The orientation of the surgical epicondylar axis varies in varus and non-varus knees in the coronal plane.
abstract: OBJECTIVE
  To investigate the orientations of the surgical epicondylar axis (SEA) of varus and non-varus knees in the coronal plane.
  
  
  METHODS
  One-hundred and sixty-two knees from 81 Chinese patients undergoing total knee arthroplasty (TKA) were retrospectively investigated. The angle between the medial side of the femoral mechanical axis and the SEA (MA-SEA), as well as the physiological valgus angle, was measured in the coronal plane using three-dimensional reconstruction. The joint line angle (JLA) and hip-knee-ankle angle (HKAA) were measured in long-leg weight-bearing radiographs. The mean of each parameter was compared between the varus (HKAA < 177.0°) and the non-varus knees (HKAA ≥ 177.0°) using an independent t test. Linear regression was used to assess the correlation between MA-SEA with JLA and HKAA.
  
  
  RESULTS
  A total of 42 non-varus knees (6 valgus and 36 neutral knees) and 98 varus knees were measured, as 22 knees were abandoned due to unrecognizable bony landmarks. The mean MA-SEA and JLA were significantly larger in non-varus knees (both, p < 0.01). The mean physiological valgus angle was 5.9 ± 1.0° for Chinese TKA patients and was significantly larger in varus knees (p < 0.01). There was a strong positive correlation between the MA-SEA and JLA (R2= 0.35, p < 0.05).
  
  
  CONCLUSIONS
  There were significant differences in the orientation of the SEA between varus and non-varus knees, which was strongly correlated with the orientation of the femoral joint line. These findings will enhance the current knowledge of knee anatomy and should prove useful for coronal alignment in TKA.
  
  
  METHODS
  III.
authors.affiliation: Department of Orthopedic, Zhongshan Hospital, Fudan University, No. 180, Rd. Fenglin, Shanghai, China.
authors.forename: Yunjie
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Orthopedic, Zhongshan Hospital, Fudan University, No. 180, Rd. Fenglin, Shanghai, China.
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Orthopedic, Zhongshan Hospital, Fudan University, No. 180, Rd. Fenglin, Shanghai, China. sycjoint70@163.com.
authors.forename: Yunchao
authors.initials: Y
authors.lastname: Shao
authors.affiliation: Department of Orthopedic, Zhongshan Hospital, Fudan University, No. 180, Rd. Fenglin, Shanghai, China. qing_xia1964@163.com.
authors.forename: Qing
authors.identifier: http://orcid.org/0000-0003-4505-8823
authors.initials: Q
authors.lastname: Xia
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D059925:Anatomic Landmarks / Q000000981:diagnostic imaging*; D000843:Ankle Joint / Q000000981:diagnostic imaging; D019645:Arthroplasty, Replacement, Knee; D044466:Asian People; D060905:Coxa Vara / Q000000981:diagnostic imaging; D005260:Female; D005269:Femur / Q000033:anatomy & histology / Q000000981:diagnostic imaging* / Q000601:surgery; D006615:Hip / Q000000981:diagnostic imaging; D006801:Humans; D007717:Knee / Q000601:surgery; D007719:Knee Joint / Q000033:anatomy & histology / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery; D011859:Radiography; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D016474:Weight-Bearing
keywords: Femoral varus angle; Hip-knee-ankle angle; Kinematical alignment; Surgical epicondylar axis; Total knee arthroplasty