title: [Total and unicompartmental knee replacement. Patient-specific Instrumentation].
abstract: BACKGROUND
  The objective of patient-specific instrumentation (PSI Zimmer®) technology is to optimize positioning and selection of components as well as surgical procedure in uni- and bicompartimental knee replacement. The article contains a description of the planning and surgical technique and evaluates the method based on own results and literature.
  
  
  METHODS
  Using MRI or CT scans a virtual 3D model of the joint is created in order to simulate and plan the implant positioning. According to these data, pin placement and/or cutting guides are produced, which enable the surgeon to transfer the planning to the surgical procedure. In a prospective comparative study 88 patients (44 per each of the two techniques) were operated by one surgeon receiving the same TKA using either MRI-based PSI or a conventional technique. The number of surgical trays, operating time, intraoperative changes and frontal alignment using a full leg x‑ray (70 cases) were compared. In 17 patients the method was applied with unicondylar knee replacement.
  
  
  RESULTS
  Anatomical abnormalities could be detected preoperatively and considered during the operation. With PSI the number of trays could be reduced and predictability of the component size was more precise. Intraoperative changes became necessary only for distal femoral (25 %) and proximal tibial (36 %) resection and tibial rotation (40 %). Alignment was more precise in the PSI cases
  
  
  CONCLUSIONS
  PSI using the applied technique proved to be practicable and reliable. The advantages of precise planning became obvious. Results concerning alignment are inconsistent in the literature. Soft tissue balancing has only been included in the technique to a limited degree so far. PSI is still in an early stage of development and further development opportunities should be exploited before final assessment.
authors.affiliation: Abteilung Orthopädie und Unfallchirurgie, Schön Klinik Lorsch, Wilhelm-Leuschner-Straße 10, 64653, Lorsch, Deutschland. GeKoester@Schoen-Kliniken.de.
authors.forename: G
authors.initials: G
authors.lastname: Köster
authors.affiliation: Abteilung Orthopädie und Unfallchirurgie, Schön Klinik Lorsch, Wilhelm-Leuschner-Straße 10, 64653, Lorsch, Deutschland.
authors.forename: C
authors.initials: C
authors.lastname: Biró
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation* / Q000379:methods; D019544:Equipment Failure Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000295:instrumentation; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery; D007720:Knee Prosthesis; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging / Q000601:surgery*; D018579:Patient Selection; D066230:Patient-Specific Modeling; D057285:Precision Medicine / Q000295:instrumentation / Q000379:methods; D066330:Printing, Three-Dimensional / Q000295:instrumentation; D011474:Prosthesis Design; D017755:Prosthesis Fitting / Q000295:instrumentation* / Q000379:methods; D025321:Surgery, Computer-Assisted / Q000295:instrumentation* / Q000379:methods*; D016896:Treatment Outcome
keywords: Computer-assisted Surgery; Magnetic resonance imaging; Osteoarthritis of knee; Total knee replacement; Unicondylar knee replacement