title: The accuracy of component alignment in custom cutting blocks compared with conventional total knee arthroplasty instrumentation: prospective control trial.
abstract: BACKGROUND
  The purpose of this study was to assess whether custom cutting blocks improve accuracy of component alignment compared to conventional TKA instrumentation.
  
  
  METHODS
  Eighty primary TKA patients were enrolled in an open-label randomized prospective clinical trial and were divided into two groups, 40 custom cutting blocks and 40 conventional TKA instrumentations. The primary outcome was prosthetic alignment with respect to mechanical axis and epicondylar axis. Secondary outcomes included operative time, 24-hour postoperative blood loss and hemoglobin at discharged.
  
  
  RESULTS
  There were no statistical significant differences in the postoperative mechanical axis between the custom cutting blocks group and conventional TKA group, (95% vs. 87.5% within 3° of neutral mechanical alignment, p=0.192). The average rotational alignment was statistically significantly different in the custom cutting blocks group (1.0°±0.6° vs. 1.6°±1.8° external rotation from epicondylar axis, p<0.001). There were statistical significant differences in operation time between custom cutting blocks group and conventional group, skin to skin [57.5±2.3 min vs. 62.1±1.5, p<0.001]. We found an improvement in group 1 compared with group 2 regarding the proportion of patients with postoperative blood loss within 24 h.
  
  
  CONCLUSIONS
  Custom cutting blocks technique was a surgical procedure which provided better accuracy in rotational alignment but no statistical differences in mechanical axis, less operative time and reduced blood loss than the conventional TKA instrumentation in the majority of patients.
authors.affiliation: Department of Orthopedic Surgery, Phramongkutklao Hospital and College of Medicine, Bangkok, Thailand. Electronic address: tanainit@hotmail.com.
authors.forename: Thanainit
authors.initials: T
authors.lastname: Chotanaphuti
authors.affiliation: Department of Orthopedic Surgery, Phramongkutklao Hospital and College of Medicine, Bangkok, Thailand.
authors.forename: Visit
authors.initials: V
authors.lastname: Wangwittayakul
authors.affiliation: Department of Orthopedic Surgery, Phramongkutklao Hospital and College of Medicine, Bangkok, Thailand.
authors.forename: Saradej
authors.initials: S
authors.lastname: Khuangsirikul
authors.affiliation: Department of Orthopedic Surgery, Phramongkutklao Hospital and College of Medicine, Bangkok, Thailand.
authors.forename: Trakul
authors.initials: T
authors.lastname: Foojareonyos
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation*; D016063:Blood Loss, Surgical; D006801:Humans; D021621:Imaging, Three-Dimensional; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery; D007720:Knee Prosthesis; D008875:Middle Aged; D061646:Operative Time; D011446:Prospective Studies; D017755:Prosthesis Fitting / Q000295:instrumentation*; D012399:Rotation; D025321:Surgery, Computer-Assisted; D014057:Tomography, X-Ray Computed
keywords: Accuracy; Custom cutting blocks; Mechanical axis; Rotational axis; Total knee arthroplasty