title: Individual valgus correction angle improves accuracy of postoperative limb alignment restoration after total knee arthroplasty.
abstract: OBJECTIVE
  The purpose of the current study was to compare and investigate the effect of fixed and individual valgus correction angle (VCA) on postoperative alignment restoration. It is hypothesized that individual VCA would be more accurate than fixed VCA in postoperative limb alignment restoration.
  
  
  METHODS
  Four hundred and fifty-two patients with 546 consecutive uncomplicated primary total knee arthroplasties performed by a single surgeon, with 302 knees that had individual VCA (group A) and 244 knees that had fixed 5° VCA (group B), were enroled in this study. Preoperative and postoperative full-length standing hip-to-ankle radiographs were used to assess limb alignment. Postoperative hip-knee-ankle angle (θ), femoral component angle (α) and tibial component angle (β) were measured and compared between the two groups.
  
  
  RESULTS
  Mean postoperative θ angle and α angle were 178.9° (SD 1.3°) and 89.1° (SD 1.1°) in the group A, whereas they were 177.8° (SD 1.9°) and 87.9° (SD 1.5°) in the group B. There were significant differences in both parameters between the two groups (p = 0.021 and 0.016, respectively). Mean postoperative β was 89.8° (SD 1.2°) in the group A and 89.7° (SD 1.3°) in the group B, and no significant difference was detected. There were 114 (37.7 %), 221 (73.2 %) and 265 (87.7 %) knees that had restoration of mechanical axis to ±1°, ±2°, ±3° of neutral, respectively, and 37 (12.3 %) outliers (>±3°) in the group A, whereas there were 48 (19.7 %), 122 (50.0 %) and 170 (69.7 %) knees that had restoration of mechanical axis to ±1°, ±2°, ±3° of neutral, respectively, and 74 (30.3 %) outliers in the group B. Group A had a higher percentage of restoration of limb alignment and fewer outliers than those in the group B, and this difference was statistically significant (p < 0.001).
  
  
  CONCLUSIONS
  The results from the present study demonstrated that individual VCA for distal femoral resection could enhance the accuracy of postoperative limb alignment restoration compared with fixed VCA. For clinical relevance, individual VCA should be recommended for routine use in all patients in order to achieve the expected postoperative neutral limb alignment and reduce the risk of postoperative malalignment due to the planning error of a fixed VCA.
  
  
  METHODS
  Prospective comparative study, Level II.
authors.affiliation: The Orthopedic Department, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Shi
authors.affiliation: The Orthopedic Department, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Hai
authors.initials: H
authors.lastname: Li
authors.affiliation: The Orthopedic Department, West China Hospital, Sichuan University, Chengdu, China. zongke@126.com.
authors.forename: Zongke
authors.initials: Z
authors.lastname: Zhou
authors.affiliation: The Orthopedic Department, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Shen
authors.affiliation: The Orthopedic Department, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Yang
authors.affiliation: The Orthopedic Department, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Pengde
authors.initials: P
authors.lastname: Kang
authors.affiliation: The Orthopedic Department, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Fuxing
authors.initials: F
authors.lastname: Pei
mesh_terms: D000368:Aged; D000843:Ankle Joint / Q000000981:diagnostic imaging; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D017760:Bone Malalignment / Q000000981:diagnostic imaging / Q000517:prevention & control*; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery; D056304:Genu Valgum / Q000150:complications / Q000000981:diagnostic imaging / Q000601:surgery*; D056305:Genu Varum / Q000150:complications; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000150:complications / Q000601:surgery*; D011184:Postoperative Period; D011446:Prospective Studies; D011859:Radiography; D066231:Surgeons; D013977:Tibia / Q000000981:diagnostic imaging / Q000601:surgery
keywords: Alignment; Total knee arthroplasty; Valgus correction angle