title: The Impact of Mechanical and Restricted Kinematic Alignment on Knee Anatomy in Total Knee Arthroplasty.
abstract: Total knee arthroplasty (TKA), aiming at neutral mechanical alignment (MA), inevitably modifies the patient's native knee anatomy. Another option is kinematic alignment (KA), which aims to restore the original anatomy of the knee. The aim of this study was to evaluate the variations in lower limb anatomy of a patient population scheduled for TKA, and to assess the use of a restricted KA TKA protocol and compare the resulting anatomic modifications with the standard MA technique.
  
  
  
  A total of 4884 knee computed tomography scans were analyzed from a database of patients undergoing TKA with patient-specific instrumentation. The lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), and hip-knee-ankle angle (HKA) were measured. Bone resections were compared using a standard MA and a restricted KA aiming for independent tibial and femoral cuts of maximum ±5° deviation from the coronal mechanical axis and a resulting overall coronal HKA within ±3° of neutral.
  
  
  
  The mean preoperative MPTA was 2.9° varus, LDFA was 2.7° valgus, and overall HKA was 0.1° varus. Using our protocol, 2475 knees (51%) could have undergone KA without adjustment. To include 4062 cases (83%), mean corrections of 0.5° for MPTA and 0.3° for LDFA were needed, significantly less than with MA (3.3° for MPTA and 3.2° for LDFA; P < .001).
  
  
  
  The range of knee anatomy in patients scheduled for TKA is wide. MA leads to greater modifications of knee joint anatomy. To avoid reproducing extreme anatomy, the proposed restricted KA protocol provides an interesting hybrid option between MA and true KA.
authors.affiliation: Department of Surgery, Hôpital Maisonneuve-Rosemont, Université de Montréal, Montréal, QC, Canada.
authors.forename: Abdulaziz M
authors.initials: AM
authors.lastname: Almaawi
authors.affiliation: Complex Arthroplasty Unit, St George's University Hospitals, NHS Foundation Trust, London.
authors.forename: Jonathan R B
authors.initials: JRB
authors.lastname: Hutt
authors.affiliation: Department of Surgery, Hôpital Maisonneuve-Rosemont, Université de Montréal, Montréal, QC, Canada.
authors.forename: Vincent
authors.initials: V
authors.lastname: Masse
authors.affiliation: Department of Surgery, Hôpital Maisonneuve-Rosemont, Université de Montréal, Montréal, QC, Canada.
authors.forename: Martin
authors.initials: M
authors.lastname: Lavigne
authors.affiliation: Department of Surgery, Hôpital Maisonneuve-Rosemont, Université de Montréal, Montréal, QC, Canada.
authors.forename: Pascal-Andre
authors.initials: PA
authors.lastname: Vendittoli
mesh_terms: D000465:Algorithms; D000843:Ankle Joint / Q000502:physiology; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena; D005260:Female; D005269:Femur / Q000601:surgery; D006801:Humans; D007719:Knee Joint / Q000033:anatomy & histology / Q000601:surgery*; D035002:Lower Extremity / Q000033:anatomy & histology / Q000502:physiology; D008297:Male; D013977:Tibia / Q000601:surgery; D014057:Tomography, X-Ray Computed
keywords: alignment; kinematic; knee anatomy; ligament balance; mechanical; total knee arthroplasty