A New Navigation System for Minimally Invasive Total Knee Arthroplasty

A computer-assisted navigation system to be used for total knee arthroplasties (TKAs) was reported to improve the accuracy of bone resection and result in precise implant placement, but the concomitant surgical invasion and time consumption are clinical problems. We developed a computed tomography (CT)-based navigation system (NNS) to be used for minimally invasive TKA. It requires only the reference points from a small limited area of the medial femoral condyle and proximal tibia through a skin incision to obtain optical images. Here we evaluated the usefulness and accuracy of the NNS in comparison with the commercially available BrainLAB image-free navigation system (BLS). In a clinical experiment, the registration times obtained with the NNS tended to be shorter than those obtained with the BLS, but not significantly so. The NNS group tended to be in the extended position in the sagittal plane of the distal femur within 3 degrees, and the BLS group showed rather flexed deviation in the sagittal plane of the anterior femur

Machining of biocompatible materials: Recent advances

Machining of biocompatible materials is facing the fundamental challenges due to the specific material properties as well as the application requirements. Firstly, this paper presents a review of various materials which the medical industry needs to machine, then comments on the advances in the understanding of their specific cutting mechanisms. Finally it reviews the machining processes that the industry employs for different applications. This highlights the specific functional requirements that need to be considered when machining biocompatible materials and the associated machines and tooling. An analysis of the scientific and engineering challenges and opportunities related to this topic are presented

An Analysis of the Characteristics and Improved Use of Newly Developed CT-based Navigation System in Total Hip Arthroplasty

We developed a surface matching-type computed tomography (CT)-based navigation system for total hip arthroplasty (the N-navi; TEIJIN NAKASHIMA MEDICAL, Okayama, Japan). In the registration step, surface matching was performed with digitizing points on the pelvic bone surface after coarse paired matching. In the present study, we made model bones from the CT data of patients whose acetabular shapes had various deformities. We measured the distances and angles after surface matching from the fiducial points and evaluated the ability to correct surface-matching registration on each pelvic form, using several areas and numbers of points. When the surface-matching points were taken on the superior area of the acetabulum, the correction was easy for the external direction, but it was difficult to correct for the anterior and proximal directions. The correction was difficult for external and proximal directions on the posterior area. Each area of surface-matching points has particular directions that are easily corrected and other directions that are difficult to correct. The shape of the pelvis also affected the correction ability. Our present findings suggest that checking the position after coarse paired matching and choosing the surface-matching area and points that are optimal to correct will improve the accuracy of total hip arthroplasty and reduce surgical times

人工関節置換術時の骨切削挙動に関する研究

University of Tokyo (東京大学

Autonomous penetration detection for bone cutting tool using demonstration-based learning

In orthopedic surgery, bone-cutting procedures are frequently performed. However, bone-cutting procedures are very risky in cases where vital organs or nerves exist beneath the target bones. In such cases, surgeons are required to determine the depth of the penetration into the bone by using only their haptic senses. Thus, we developed a handheld bone-cutting-tool system that detects the penetration of the cutting material. The developed system autonomously detects the penetration before total penetration and stops the actuation of the cutting tool, leaving a very thin remnant of work material. The developed system estimates the cutting resistance by using its motor's current and rotational speed. On the basis of data collected preoperatively, the system estimates the cutting state by using a support vector machine (SVM). According to the SVM outputs, the system detects the penetration of the work material and autonomously stops the actuation of the cutting tool. The proposed method was verified through experiments, and the results showed that the developed system successfully detected the penetrations of work materials and stopped autonomously immediately before total penetration. This study showed that the autonomous detection of bone penetration with a hand-held bone-cutting tool is feasible by using the proposed scheme