title: Pinless navigation in total knee arthroplasty: navigation reduced by the maximum?
abstract: OBJECTIVE
  Restoring a neutral mechanical axis in total knee arthroplasty (TKA) (within ±3° of varus/valgus) is associated with superior functional outcome and reduced early implant failure. Using conventional alignment jigs results in malalignment in >20 % of cases. In this study, we investigated the reduction of outliers within the threshold of ±3° of leg alignment using a "pinless" navigation system in comparison with conventional alignment jigs investigated.
  
  
  METHODS
  In this randomised prospective study, 80 patients were randomly assigned/allocated to the pinless or conventional control group. After surgery, the two groups were compared regarding outliers > ±3° by means of hip-knee-ankle angle (HKA), mechanical medial proximal tibia angle (mMPTA), mechanical lateral distal femoral angle (mLDFA) and duration of surgery. Student's unpaired t test was used for quantitative variables, Fisher's exact test compared groups (pinless vs. control) and a two-sided p value of ≤0.05 was considered statistically significant.
  
  
  RESULTS
  In the pinless group, outliers regarding HKA and mLDFA > ±3° was significantly reduced (p = 0.025 and p = 0.002 respectively). In the pinless group, the surgery duration was significantly longer (75.6 vs. 64.5 minutes, p < 0.001).
  
  
  CONCLUSIONS
  Pinless navigation is effective in reducing outliers > ±3° regarding HKA without risking pin-related complications, such as fractures, infections or breaking screws. However, not all tools for conventional navigation in TKA, such as real-time measurements of the tibiofemoral axis and gap balancing, are available.
authors.affiliation: Department of Orthopaedic Surgery, University of Regensburg, Regensburg, Germany, Guenther.Maderbacher@klinik.uni-regensburg.de.
authors.forename: Günther
authors.initials: G
authors.lastname: Maderbacher
authors.forename: Jens
authors.initials: J
authors.lastname: Schaumburger
authors.forename: Armin
authors.initials: A
authors.lastname: Keshmiri
authors.forename: Magdalena
authors.initials: M
authors.lastname: Barthel
authors.forename: Hans-Robert
authors.initials: HR
authors.lastname: Springorum
authors.forename: Benjamin
authors.initials: B
authors.lastname: Craiovan
authors.forename: Joachim
authors.initials: J
authors.lastname: Grifka
authors.forename: Clemens
authors.initials: C
authors.lastname: Baier
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D005269:Femur / Q000601:surgery; D006801:Humans; D007719:Knee Joint / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D025321:Surgery, Computer-Assisted / Q000379:methods*; D013977:Tibia / Q000601:surgery