title: Computer-assisted stereotaxic navigation improves the accuracy of mechanical alignment and component positioning in total knee arthroplasty.
abstract: BACKGROUND
  This study reports on a novel computer-assisted stereotaxic navigation (CASN) system that attempts to combine the accuracy of computer navigation with familiarity of conventional methods. We hypothesize that CASN would improve mechanical alignment and component positioning when compared to conventional instrumentation.
  
  
  METHODS
  145 patients (192 knees) retrospectively matched for age, BMI, gender and pre-operative scores, underwent total knee arthroplasty (TKA) using CASN (n = 92) or conventional instrumentation (n = 100). Pre- and post-operative radiological alignment [Acceptable ranges: mechanical axis (MA) 0° ± 3°, coronal femoral-component angle (CFA) and coronal tibia-component angle (CTA) 90° ± 3°] and clinical outcomes (Knee Society Scores, Oxford Knee Score and Short Form-36) at 6 months were examined.
  
  
  RESULTS
  The CASN group had significantly improved mean MA (1.9° ± 1.4°, versus 2.8° ± 2.0° in the conventional group, p = 0.001), CFA (1.6° ± 1.3°, versus 2.1° ± 1.5° in the conventional group, p = 0.035) and CTA (1.6° ± 1.2°, versus 2.1° ± 1.5° in the conventional group, p = 0.024). 91.3 % of knees in the CASN group were within 3° of a neutral mechanical axis, versus 74 % in the conventional group (p < 0.001). The duration of surgery was significantly longer in the CASN group (84 ± 22 vs 73 ± 15 min, p = 0.001) and cost an additional USD 850 per operation. There were no significant differences in clinical outcomes or satisfaction rates at 6 months post-operatively (p > 0.05).
  
  
  CONCLUSIONS
  CASN improved TKA mechanical alignment and component positioning, however, resulted in longer and costlier surgery with no benefits in short-term functional outcomes, despite providing familiarity to surgeons accustomed to conventional instrumentation.
  
  
  METHODS
  III.
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, 20 College Road, Academia, Level 4, Singapore, 169865, Singapore. dr.lincoln.liow@gmail.com.|Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, 02114, Massachusetts, USA. dr.lincoln.liow@gmail.com.
authors.forename: Ming Han Lincoln
authors.initials: MH
authors.lastname: Liow
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, 20 College Road, Academia, Level 4, Singapore, 169865, Singapore.
authors.forename: Graham Seow-Hng
authors.initials: GS
authors.lastname: Goh
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, 20 College Road, Academia, Level 4, Singapore, 169865, Singapore.
authors.forename: Hee-Nee
authors.initials: HN
authors.lastname: Pang
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, 20 College Road, Academia, Level 4, Singapore, 169865, Singapore.
authors.forename: Darren Keng Jin
authors.initials: DK
authors.lastname: Tay
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, 20 College Road, Academia, Level 4, Singapore, 169865, Singapore.
authors.forename: Ngai Nung
authors.initials: NN
authors.lastname: Lo
authors.affiliation: Department of Orthopaedic Surgery, Singapore General Hospital, 20 College Road, Academia, Level 4, Singapore, 169865, Singapore.
authors.forename: Seng Jin
authors.initials: SJ
authors.lastname: Yeo
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D061646:Operative Time; D020370:Osteoarthritis, Knee / Q000601:surgery; D017060:Patient Satisfaction; D017755:Prosthesis Fitting / Q000379:methods*; D012189:Retrospective Studies; D013238:Stereotaxic Techniques; D025321:Surgery, Computer-Assisted / Q000379:methods*
keywords: Accelerometer; Computer-assisted; Mechanical axis; Navigation; Stereotaxic; Total knee arthroplasty; iASSIST