PRESS-FIT TOTAL KNEE ARTHROPLASTY WITH A ROBOTIC-CUTTING GUIDE: PROOF OF CONCEPT AND INITIAL CLINICAL EXPERIENCE

Abstract

Introduction Intimate bone-implant contact is a requirement for achieving stable component fixation and osseo-integration of porous-coated implants in TKA. However, consistently attaining a press-fit and a tight-fitting femoral component can be problematic when using conventional instrumentation. We present a new robotic cutting-guide system that permits intra-operative adjustment of the femoral resections such that a specified amount of press-fit can be consistently attained. System Description: A.R.T. (Apex Robotic Technology) employs a miniature bone-mounted robotic cutting-guide and flexible software that permits the surgeon to adjust the anterior and posterior femoral resections in increments of 0.25 mm per resection, allowing a maximum of 1.5mm of total added press in the AP dimension. Methods The accuracy of guide-positioning and bone-cutting with A.R.T. was assessed in bench testing on synthetic bones (SAWBONES®) using an optical comparator. The individual guide locations for 16 femoral cut positioning sequences (80 guide positions in total) were measured. Femoral resections were performed with A.R.T. on eight sawbones (two per fit-adjustment setting) and the anterior-posterior dimensions of the final cut surfaces were also measured. Eight sawbones were prepared using conventional instrumentation (jigs) as controls: four with a 0 mm press-fit block and four with a +0.5 mm specially manufactured press-fit block. Results The robotic guide-positioning error in the AP dimension was −0.04 ± 0.14mm (mean ± standard deviation, SD). The standard deviation in guide positioning for the distal, anterior chamfer and posterior chamfer resections was 0.03° and 0.17mm. The average error in the AP dimension between the targeted and measured cuts was −0.14±0.13mm with A.R.T. and 0.7±0.52mm with conventional blocks (p=0.021). Conclusions A.R.T. guide positioning precision was found to be sub-degree and sub-millimetric, allowing for significantly more accurate and repeatable bone resections than conventional instrumentation.