EVALUATION OF A NEW COMPUTER GUIDANCE SYSTEM: NEW SITES

Total knee arthroplasty (TKA) is a common procedure with good success rates. The literature shows resection accuracy plays a crucial role in device longevity 1 . Computer guidance is used by some surgeons to enhance accuracy. This study reports on a continuous series of Optetrak knee prostheses (Exactech Inc., FL, USA) implanted by three senior surgeons between October 2010 and December 2013. 324 TKA were implanted at the Joseph Ducuing Hospital, Toulouse, France (Site 1), the Cleveland Clinic, Cleveland, OH, USA (Site 2) and the Riverview Hospital, Noblesville, IN, USA (Site 3) using Exactech GPS (Blue-Ortho, Grenoble, FR), a new computer-assisted guidance system. Each centre in this study used different surgical profiles defined specifically for their surgeical preferences. Planned tibial and femoral cuts were compared to actual cuts digitised using GPS. Operating time was analyzed and post-operative leg alignment was compared to pre-operative. The mean error between planned and digitised proximal tibial cuts was 0.06°±0.89 of valgus and 0.53°±0.90 of anterior slope for Site 1, 0.18°±0.85 of varus and 0.25°±1.18 of posterior slope for Site 2, and 0.02°±0.51 of valgus and 0.60°±1.15 of anterior slope for Site 3. The mean error between planned and digitised femoral distal cuts was 0.14°±0.85 of valgus and 0.49°±0.93 of flexion for Site 1, 0.15°±0.96 of varus and 0.04°±1.54 of extension for Site 2, and 0.09°±0.54 of varus and 0.48°±1.21 of extension for Site 3. Average operating time was 29 minutes for Site 1, 39 minutes for Site 2, and 33 minutes for Site 3. Post-operative Hip-Knee-Ankle angle (HKA) varied between 172° and 184° with an average of 179° for Site 1, 177° to 183° with an average of 179° for Site 2, and 177° to 185° with an average of 180° for Site 3. Pre-operative HKA ranged from 162 to 189°. Site 1 was already reporting in the series presented at ISTA 2013 2 . Sites 2 and 3 were added later and could therefore benefit from the early feedback the analysis of site 1 cases provided. The use of the computer guidance at the new sites was associated with promising results and it did not take long to the surgeons to reach a reproducibility equivalent to the one of site 1. Average surgical time was similar in all three sites. GPS guidance added an average of 10 minutes to standard surgical times. All surgeons agreed the increased accuracy justified the additional time. Average post-operative HKA was 179°. HKA scores were within 3° of perfect alignment in 96% of the cases of Site 1, 99% of Site 2 and 97% of Site 3. According to the literature 1 , HKA between 177° and 183° is linked with high implant survival. Participating surgeons still associated Exactech GPS with satisfactory immediate post-operative results.