A Robotic System for Implant Modification in Single-stage Cranioplasty

Craniomaxillofacial reconstruction with patientspecific customized craniofacial implants (CCIs) is most commonly performed for large-sized skeletal defects. Because the exact size of skull resection may not be known prior to the surgery, in single-stage cranioplasty, an oversized CCI is prefabricated and resized intraoperatively with a manual-cutting process provided by a surgeon. The manual resizing, however, may be inaccurate and significantly add to the operating time. This paper introduces a fast and non-contact approach for intraoperatively determining the exact contour of the skull resection and automatically resizing the implant to fit the resection area. Our approach includes four steps: First, we acquire a patient’s defect information using a handheld 3D scanner. Second, the scanned defect is aligned to the CCI by registering the scanned defect to the preoperative CT model. Third, a cutting toolpath is generated from the scanned defect model by extracting the resection contour. Lastly, a cutting robot resizes the oversized CCI to fit the resection area. To evaluate the resizing performance of our method, we generated six different resection shapes for the cutting experiments. We compared the performance of our method to the performance of surgeon’s manual resizing and an existing technique that collects the defect contour with an optical tracking system. The results show that our proposed method improves the resizing accuracy by 56% compared to the surgeon’s manual modification and 42% compared to the optical tracking method.