title: Does lateral versus medial exposure influence total knee tibial component final external rotation? A CT based study.
abstract: BACKGROUND
  A previous study demonstrated that performing a total knee arthroplasty through a lateral approach including anterior tibial tuberosity (ATT) osteotomy (refixed in its original position) presented numerous advantages: correcting the preoperative patella lateral tilt and improving postoperative patella tracking. We hypothesized that these improvements in patella centering were, at least in part, due to an increased external rotation of the tibial component. Postoperative scannographic studies were, therefore, undertaken to measure tibial component rotation and analyze the results according the medial and lateral exposure used.
  
  
  OBJECTIVE
  Rotational positioning of the tibial component is influenced by the lateral or medial approach selected at surgery.
  
  
  METHODS
  Forty-five CAT scans, performed according to the protocol criteria of the French Hip and Knee Society (SFHG), were studied 3 months postoperatively: 15 knees operated through the lateral approach and 30 knees operated through a standard medial approach. The total knee utilized in all these cases was a posteriorly stabilized, fixed-bearing, design. We measured first the angle formed between the perpendicular to the transverse axis of the tibial component and the axis joining the ATT to the center of the knee; second we also measured the coronal distance between the center of the component and the anterior tibial tuberosity (ATT).
  
  
  RESULTS
  In the group using the medial approach, the lateral position of the ATT was 7 + or - 3mm with a rotation angle of 18 degrees . In the group using the lateral approach these measurements were respectively 1 + or - 4mm and 2 degrees (p<0.0001).
  
  
  CONCLUSIONS
  External rotation of the tibial component is substantially increased by the lateral approach compared to the medial approach. Better exposure of the lateral tibial plateau is probably responsible of this difference. This increased external rotation improves postoperative patella tracking.
  
  
  METHODS
  Prospective; comparative; non-randomized study; level 3.
authors.affiliation: Orthopaedics and Traumatology Department, Versailles Hospital Center, 78150 Le Chesnay, France.
authors.forename: D
authors.initials: D
authors.lastname: Passeron
authors.forename: F
authors.initials: F
authors.lastname: Gaudot
authors.forename: P
authors.initials: P
authors.lastname: Boisrenoult
authors.forename: L
authors.initials: L
authors.lastname: Fallet
authors.forename: P
authors.initials: P
authors.lastname: Beaufils
mesh_terms: D053587:Arthrometry, Articular; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D006801:Humans; D010329:Patella / Q000000981:diagnostic imaging* / Q000601:surgery; D011446:Prospective Studies; D011859:Radiography; D015898:Tomography Scanners, X-Ray Computed