Accuracy of Implant Placement Based on Three-Dimensional Preoperative Planning in Total Elbow Arthroplasty

<b>Background:</b> Accurate implant placement in the optimal position is important to obtain favourable clinical outcomes and prevent complications in total joint arthroplasty. We aimed to assess the accuracy of implant placement based on three-dimensional (3D) preoperative planning for unlinked total elbow arthroplasty (TEA) and to clarify the effect of implant placement on clinical outcomes. <b>Methods:</b> This study included 20 patients (22 elbows, 17 with rheumatoid arthritis and 5 with osteoarthritis, with a mean follow-up period of 47 months) who underwent TEA with an unlinked-type implant after computed tomography (CT)-based 3D preoperative planning. Implant placement was planned preoperatively and several parameters were set to reflect it intraoperatively. TEA was performed based on the plan, and postoperative CT was conducted to evaluate differences in implant placement by comparing the preoperative plan and postoperative implant placement. Furthermore, we evaluated the relationship between implant placement differences and postoperative clinical outcomes, including range of motion, Visual Analogue Scale, Mayo Elbow Performance Score 1 year after surgery and complications at the last follow-up. <b>Results:</b> The mean absolute translation was within 2 mm, the mean absolute tilt was within 4°, the mean absolute rotation of the humeral component was within 4° and the mean absolute rotation of the ulnar component was 10.2° ± 6.8°. In the ulnar components, 15/22 (68%) cases were externally rotated, and the mean external rotation was 7.1° ± 10.2°. We defined the absolute ulnar component's rotational difference of more than 10° as a 'malrotation' group (<i>n</i> = 8) and 10° or less as a 'control' group (<i>n</i> = 14). We compared the clinical outcomes between both groups, however, no significant differences were observed in clinical outcomes and complications. <b>Conclusions:</b> We observed notable malrotation in the postoperative positioning of the ulnar component. Intraoperative support devices may be necessary to accurately reproduce the preoperative plan in the surgical field. <b>Level of Evidence:</b> Level IV (Therapeutic).