Implant positioning in total knee arthroplasty: an intra- and post-operative comparison between conventional and patient-specific instrumentation

2 The number of total knee arthroplasties (TKAs) continuously increases with good to 3 excellent results. In the last years, new surgical techniques are developing to improve prosthesis 4 positioning. In this context patient-specific instrumentations (PSI) are included. The aim of this 5 study is to compare the perioperative parameters and the spatial positioning of prosthetic 6 components in TKAs performed with a PSI, with respect to traditional TKA. 7 In this prospective comparative randomized study, 15 patients underwent TKA basing upon 8 a three-dimensional (3D) magnetic resonance (MR) imaging preoperative planning (PSI group), 9 while 15 patients underwent traditional TKA (nPSI group). All patients underwent a postoperative 10 computed tomography (CT) examination. For the PSI group, data planned preoperatively, regarding 11 femoral and tibial bone resections, were correlated with intraoperative measurements. Surgical time, 12 hospitalization length, intraoperative and postoperative bleeding were compared between the 2 13 groups. Positioning of implants at postoperative CT was finally assessed for both groups. 14 Data planned on 3D MR imaging, regarding the depth of bone cuts, showed good to 15 excellent correlation with intraoperative measurements. Patients of the PSI group showed a better 16 perioperative outcome and a good correlation between the spatial positioning of prosthetic 17 components planned preoperatively and that observed on postoperative CT. Less variability was 18 found in the PSI group with respect to nPSI as regards the spatial orientation of prosthetic 19 components. 20 Preoperative planning through 3D MR imaging in TKA has a better perioperative outcome 21 with respect to the traditional method. Use of a PSI can also improve the spatial positioning of both 22 prosthetic components.