title: Can CT-based patient-matched instrumentation achieve consistent rotational alignment in knee arthroplasty?
abstract: OBJECTIVE
  Long-term success of contemporary total knee replacements relies to a large extent on proper implant alignment. This study was undertaken to test whether specimen-matched cutting blocks based on computed axial tomography (CT) scans could provide accurate rotational alignment of the femoral component.
  
  
  METHODS
  CT scans of five fresh frozen full leg cadaver specimens, equipped with infrared reflective markers, were used to produce a specimen-matched femoral cutting block. Using those blocks, the bone cuts were made to implant a bi-compartmental femoral component. Rotational alignment of the components in the horizontal plane was determined using an optical measurement system and compared with all relevant rotational reference axes identified on the CT scans.
  
  
  RESULTS
  Average rotational alignment for the bi-compartmental component in the horizontal plane was 1.9° (range 0°-6.3°; standard deviation 2.6°). One specimen that showed the highest deviation from the planned alignment also featured a completely degraded medial articular surface.
  
  
  CONCLUSIONS
  The CT-based specimen-matched cutting blocks achieved good rotational alignment accuracy except for one specimen with badly damaged cartilage. In such cases, imaging techniques that visualize the cartilage layer might be more suitable to design cutting blocks, as they will provide a better fit and increased surface support.
authors: sporthopaedicum straubing, Bahnhofplatz 27, 94315 Straubing, Germany.
authors: C O
authors: CO
authors: Tibesku
authors: B
authors: B
authors: Innocenti
authors: P
authors: P
authors: Wong
authors: A
authors: A
authors: Salehi
authors: L
authors: L
authors: Labey
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation* / Q000379:methods*; D002102:Cadaver; D006801:Humans; D014057:Tomography, X-Ray Computed