Several surgical assistance systems for total knee arthroplasty (TKA) have been applied to enhance the surgical precision. The accuracy of these surgical assistance systems has been evaluated with regards to the implant setting posture by 2-dimensional X-ray images. It was found that these systems were effective in enhancing surgical precision as reported in several publications. On the other hand, some authors reported no significant difference between these systems and conventional operation. When using 2-dimensional X-ray images for evaluation, a wrong knee posture during image acquisition introduces an error. Therefore, we evaluated several 3-dimensional evaluation methods using CT scans. In this study, we adopted three evaluation methods for TKA : 1) CT-based preplanning software, 2) 3-dimensional matching using a CAD model, and 3) a surgical navigation system. The error of these evaluation methods was less than 2 mm and 2 degrees. In conclusion, 1) it is important to validate the evaluation tool for each implant geometry and/or each evaluation method, 2) a suitable evaluation method should be selected in accordance with the intended use.

Pediatric minimally invasive surgery requires advanced surgical skills ; however, the small number of pediatric patients limits opportunities for junior pediatric surgeons to learn and practice these skills. Thus, a neonatal thoracic cavity model was developed to simulate thoracoscopic repair of esophageal atresia in neonates. In this study, the ribcage of a 13-day-old patient was produced in rapid prototyping and covered with a 10-mm thick sheet into which three surgical instrument ports were inserted and fixed. An esophagus model, an 8-mm polyvinyl-alcohol tube, was placed inside the ribcage, with the upper end fixed to a force sensor. A position tracking system integrating optical and electromagnetic systems was developed, which achieved a 99.8% tracking ratio. In preliminary experiments, four pediatric surgeons performed suturing on the esophagus model, and the task completion time, tool path, and force applied on the esophagus model were measured. All subjects successfully completed the tasks and thereafter answered to a questionnaire. The result of the questionnaire shows that the model has a potential as a skill assessment and training tool for pediatric surgeons. In the future, pediatric surgeons with different skill levels will be recruited to perform surgical skill assessment, and the model will be validated.