title: A comparison of conventional and patient-specific instruments in total knee arthroplasty.
abstract: OBJECTIVE
  Several authors have observed that standard instrumentation (SI) may be insufficient for addressing component malalignment. Patient-matched cutting blocks (PMCB) technology was introduced to improve surgeons' ability to achieve a neutral postoperative mechanical axis following total knee arthroplasty (TKA). The current retrospective study was designed to compare the ability of SI and PMCB to achieve a hip-knee-ankle angle (HKA) within ±3° of the ideal alignment of 180°.
  
  
  METHODS
  Between October 2009 and December 2012, 170 TKAs in 166 patients (four bilateral) using VISIONAIRE (Smith & Nephew) PMCB technology were performed. Additionally, 160 TKAs in 160 consecutive patients that had received a total knee arthroplasty using SI during the same time period were used as a control group, All surgeries were performed by the same surgeon. Standardized pre- and postoperative long-leg standing x-rays were retrospectively evaluated to compare the two patient cohorts.
  
  
  RESULTS
  X-rays were available for analysis for 156 knees in the SI group and 150 in the PMCB group. The average post-surgical HKA was 178.7 ± 2.5 in the SI group and 178.4 ± 1.5 in the PMCB group. However, the rate of ± 3° outliers was 21.2 % in the SI group and 9.3 % in the PMCB group. There were no intraoperative complications with the use of PMCB technology or SI.
  
  
  CONCLUSIONS
  PMCB technology proved superior to conventional instrumentation in achieving a neutral mechanical axis following TKA. Further follow-up will be needed to ascertain the long-term impact of these findings.
authors.affiliation: Department of Orthopaedic Surgery, Annastift Hannover (Medical School Hannover; MHH), Hannover, Germany.
authors.forename: Kiriakos
authors.initials: K
authors.lastname: Daniilidis
authors.forename: Carsten O
authors.initials: CO
authors.lastname: Tibesku
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000843:Ankle Joint / Q000000981:diagnostic imaging; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation* / Q000379:methods; D017760:Bone Malalignment / Q000000981:diagnostic imaging / Q000453:epidemiology; D016022:Case-Control Studies; D015331:Cohort Studies; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging; D006801:Humans; D015994:Incidence; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D017755:Prosthesis Fitting; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
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