title: Patient-specific instrumentation improved mechanical alignment, while early clinical outcome was comparable to conventional instrumentation in TKA.
abstract: OBJECTIVE
  The aim of this prospective study was to compare early clinical outcome, radiological limb alignment, and three-dimensional (3D)-component positioning between conventional and computed tomography (CT)-based patient-specific instrumentation (PSI) in primary mobile-bearing total knee arthroplasty (TKA).
  
  
  METHODS
  Two hundred ninety consecutive patients (300 knees) with severe, debilitating osteoarthritis scheduled for TKA were included in this study using either conventional instrumentation (CVI, n = 150) or PSI (n = 150). Patients were clinically assessed before and 2 years after surgery according to the Knee-Society-Score (KSS) and the visual-analog-scale for pain (VAS). Additionally, the Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) and the Oxford-Knee-Score (OKS) were collected at follow-up. To evaluate accuracy of CVI and PSI, hip-knee-ankle angle (HKA) and 3D-component positioning were assessed on postoperative radiographs and CT.
  
  
  RESULTS
  Data of 222 knees (CVI: n = 108, PSI: n = 114) were available for analysis after a mean follow-up of 28.6 ± 5.2 months. At the early follow-up, clinical outcome (KSS, VAS, WOMAC, OKS) was comparable between the two groups. Mean HKA-deviation from the targeted neutral mechanical axis (CVI: 2.2° ± 1.7°; PSI: 1.5° ± 1.4°; p < 0.001), rates of outliers (CVI: 22.2%; PSI: 9.6%; p = 0.016), and 3D-component positioning outliers were significantly lower in the PSI group. Non-outliers (HKA: 180° ± 3°) showed better clinical results than outliers at the 2-year follow-up.
  
  
  CONCLUSIONS
  CT-based PSI compared with CVI improves accuracy of mechanical alignment restoration and 3D-component positioning in primary TKA. While clinical outcome was comparable between the two instrumentation groups at early follow-up, significantly inferior outcome was detected in the subgroup of HKA-outliers.
  
  
  METHODS
  Prospective comparative study, Level II.
authors.affiliation: Department of Orthopedics, St. Vincent Hospital, Stumpergasse 13, 1060, Vienna, Austria. werner.anderl@bhs.at.
authors.forename: Werner
authors.initials: W
authors.lastname: Anderl
authors.affiliation: Department of Orthopedics, St. Vincent Hospital, Stumpergasse 13, 1060, Vienna, Austria.
authors.forename: Leo
authors.initials: L
authors.lastname: Pauzenberger
authors.affiliation: Department of Orthopedics, St. Vincent Hospital, Stumpergasse 13, 1060, Vienna, Austria.
authors.forename: Roman
authors.initials: R
authors.lastname: Kölblinger
authors.affiliation: Department of Orthopedics, St. Vincent Hospital, Stumpergasse 13, 1060, Vienna, Austria.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Kiesselbach
authors.affiliation: Department of Orthopedics, St. Vincent Hospital, Stumpergasse 13, 1060, Vienna, Austria.
authors.forename: Georg
authors.initials: G
authors.lastname: Brandl
authors.affiliation: Department of Orthopedics, St. Vincent Hospital, Stumpergasse 13, 1060, Vienna, Austria.
authors.forename: Brenda
authors.initials: B
authors.lastname: Laky
authors.affiliation: Department of Orthopedics, St. Vincent Hospital, Stumpergasse 13, 1060, Vienna, Austria.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Kriegleder
authors.affiliation: Department of Orthopedics, St. Vincent Hospital, Stumpergasse 13, 1060, Vienna, Austria.
authors.forename: Philipp
authors.initials: P
authors.lastname: Heuberer
authors.affiliation: Department of Orthopedics, St. Vincent Hospital, Stumpergasse 13, 1060, Vienna, Austria.
authors.forename: Eva
authors.initials: E
authors.lastname: Schwameis
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation*; D017760:Bone Malalignment / Q000000981:diagnostic imaging / Q000209:etiology / Q000517:prevention & control*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery*; D011446:Prospective Studies; D025321:Surgery, Computer-Assisted / Q000295:instrumentation*; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
keywords: 3D-component positioning; CT-based cutting block; Clinical and radiological outcome; MyKnee; Patient-specific instrumentation; Total knee arthroplasty