title: Total knee arthroplasty with patient-specific instruments improves function and restores limb alignment in patients with extra-articular deformity.
abstract: BACKGROUND
  Restoring function and alignment when treating knee arthritis with a total knee arthroplasty (TKA) in patients who have an extra-articular deformity (EAD) from a malunion or with retained femoral hardware is a challenge. The normal anatomical landmarks are hard to find and difficult to use to obtain correct alignment. The procedure will be further challenged by angular deformity of the femur or tibia. A retrospective study was performed on a case series of patients with EAD or obliteration of the canal treated with patient-specific instruments (PSI).
  
  
  METHODS
  A multicenter retrospective review of 10 patients with multiplanar deformities in which the knee components were aligned with patient-specific instruments was performed. Outcome and alignment were studied.
  
  
  RESULTS
  At a mean follow-up of 3.4years, function improved from preoperative as evidenced by a mean increase in the KS pain score of 53 points, KS function score of 48 points and Oxford Score of 28 points (P<0.05). Flexion improved from 94° +/- 11° to 112° +/- 15° (P<0.05). Limb alignment was restored with a mean Hip-Knee-Ankle angle of 179.3° +/- 1.3° (P<0.05). Maximum outliers were 177° to 181°. An average tourniquet time of 75 +/- 9minutes (range, 62-83min) was observed.
  
  
  CONCLUSIONS
  The use of patient-specific instrumentation systems to perform TKA in patients without access to the intramedullary canal because of EAD or fixation devices, improved function and restored limb alignment. Mechanical alignment can easily be obtained with this technique by intra-articular correction of deformities under 20°.
  
  
  METHODS
  Level IV.
authors.affiliation: Department of Orthopaedic Surgery, Cliniques Universitaires Saint Luc, Brussels, Belgium. Electronic address: emmanuel.thienpont@uclouvain.be.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Thienpont
authors.forename: Frederic
authors.initials: F
authors.lastname: Paternostre
authors.forename: Martin
authors.initials: M
authors.lastname: Pietsch
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Hafez
authors.forename: Stephen
authors.initials: S
authors.lastname: Howell
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000379:methods*; D017760:Bone Malalignment / Q000517:prevention & control*; D005260:Female; D006801:Humans; D016916:Joint Deformities, Acquired / Q000150:complications / Q000000981:diagnostic imaging / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000601:surgery*; D011474:Prosthesis Design; D011859:Radiography; D016059:Range of Motion, Articular / Q000502:physiology; D020127:Recovery of Function; D012189:Retrospective Studies; D018570:Risk Assessment; D012720:Severity of Illness Index; D025321:Surgery, Computer-Assisted / Q000379:methods*; D016896:Treatment Outcome
keywords: Extra-articular deformity; Hardware; Navigation; Patient-specific instruments; Total knee arthroplasty