title: Favourable rotational alignment outcomes in PSI knee arthroplasty: A Level 1 systematic review and meta-analysis.
abstract: BACKGROUND
  Implant malposition in total knee arthroplasty (TKA) often results in unsatisfactory outcomes. Rotational malalignment leads to impaired patellar tracking, stability and joint biomechanics. Patient-specific instrumentation aims to improve three-dimensional implant positioning while reducing overall costs of instrumentation.
  
  
  METHODS
  A PRISMA compliant search of all relevant literature between 2000 and 2014 was performed. The primary outcome of interest was deviation from a neutral femoral and tibial axial alignment of patient-specific instrumentation (PSI) vs conventional instrumentation. Femoral rotation was measured with reference to the transepicondylar axis. Tibial rotation was reported with reference to the anterior tibial tuberosity and a "best fit" with the anterior tibial cortex.
  
  
  RESULTS
  Six randomised studies met the inclusion criteria reporting on a total of 444 knees. Computed tomography (CT) based PSI systems were used exclusively in three studies, and two further studies in association with magnetic resonance imaging (MRI). MRI was used exclusively in one study. Mean femoral rotation in the conventional group was: -1.7 to 1.6° (vs -1.7 to 1° in the PSI group). Meta-analysis demonstrated a significant treatment effect favouring PSI with increased accuracy in "three-degree outliers" with femoral rotation: Z=2.07, P=0.04. A single study reported tibial rotational outcomes with no significant difference demonstrated in conventional instrumentation vs PSI.
  
  
  CONCLUSIONS
  This Level 1 meta-analysis demonstrates favourable femoral rotational alignment outcomes in PSI knee arthroplasty. Only limited data is available for tibial rotational outcomes. Further studies with standardised "gold-standard" measurement criteria are required to clarify tibial rotational outcomes in PSI TKA.
  
  
  METHODS
  1.
authors.affiliation: Bradford Teaching Hospitals NHS Trust, Bradford, UK. Electronic address: ashim_mannan@hotmail.com.
authors.forename: A
authors.initials: A
authors.lastname: Mannan
authors.affiliation: University of East Anglia, Norwich, UK.
authors.forename: T O
authors.initials: TO
authors.lastname: Smith
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005269:Femur / Q000601:surgery; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D007720:Knee Prosthesis; D008279:Magnetic Resonance Imaging; D020370:Osteoarthritis, Knee / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery*; D010329:Patella / Q000601:surgery; D011474:Prosthesis Design; D016059:Range of Motion, Articular / Q000502:physiology*; D025321:Surgery, Computer-Assisted / Q000379:methods; D013977:Tibia / Q000601:surgery; D014057:Tomography, X-Ray Computed
keywords: Patient-specific knee; Randomised controlled trial; Rotation