Abstract
Background
Despite the success of total hip arthroplasty (THA), there are still challenges including restoration of leg length, offset, and femoral version. The Tsolution One combines preoperative planning with an active robotic system to assist in femoral canal preparation during a THA.
Purpose of Study
To demonstrate the use of an active robotic system in femoral implant placement and determine the accuracy of femoral implant position. This was evaluated in a cadaveric study.
Study Design and Methods
Four THA's were performed in fresh frozen cadaveric hips with assistance of the TSolution One System for preparation of the femoral canal. CT scans of the hip were used as input for TPLAN preoperative planning software to position the implants in three-dimensions (3D). The intraoperative process includes exposure of the joint using a posterolateral approach, fixation of the femur relative to the TCAT system, and registration of the femur. TCAT then actively milled the femoral canal in each of the cases after which Depuy Trilock implants were inserted by the surgeon. Only the femoral stem implants were considered in this study. Postoperative CT was used to compare actual implant position with preoperatively planned implant position in 3D. The translations between the centroids of the implant positions were compared.
Findings of Study
All femoral stems were successfully implanted with no complications. Implant position very closely matched the preoperative plan. Compared to the preoperative plan, the mean (± SD) positions of the centroid of the implant were off by 0.6 (±0.6) mm in the medial-lateral direction, 0.8 (±0.3) mm in the anterior-posterior direction, and 2.0 (±1.3) mm in the superior-inferior direction. No intraoperative fractures occurred. A sample of the preoperative planned position (left) and actual postoperative position (right) as seen on TPLAN can be seen in Figure 1. An example of the final 3D implant position in blue as compared to the preoperative implant position in red can be seen in Figure 2.
Conclusions
Overall, the post-operative stems positions were superior compared to the preoperative plan and it is believed that this is likely a result of not impacting the stems enough during the procedure. The medial-lateral and anterior-posterior stem positions were within 1 mm of what was planned. Active robotics can successfully be used to improve accuracy, precision, and reproducibility when considering final implant position in THA. These improvements can reduce unwanted human error and reduce complications. Further in vivo study is planned to demonstrate the clinical benefits of such improved precision.
