Biomedical subjects

Shunsaku Nishihara

Publications and source records attributed to Shunsaku Nishihara.

6 recordsLinked to original sources

PubMed2006

Comparison between hand rasping and robotic milling for stem implantation in cementless total hip arthroplasty.

We evaluated the effects of conventional hand rasping and robotic milling on the clinical and radiographic results of cementless total hip arthroplasty, with the same computed tomography (CT)-based 3-dimensional preoperative planning using a ROBODOC workstation (Integrated Surgical Systems, Davis, Calif). The robotic milling group consisted of 78 hips, and the hand-rasping group 78 hips. The radiographic findings from the preoperative planning and postoperative CT data were evaluated using the most accurate CT images reconstructed by the ROBODOC workstation. The robotic milling group showed significant superior Merle D'Aubigne hip score at 2 years. In the robotic milling group, there were no intraoperative femoral fractures, and a radiographically superior implant fit was obtained. Hand rasping had the potential to cause intraoperative femoral fractures, undersizing of the stem, unexpectedly higher vertical seating, and unexpected femoral anteversion causing inferior implant fit.

Adult↗

PubMed2004

Clinical accuracy evaluation of femoral canal preparation using the ROBODOC system.

The purpose of this study was to evaluate the clinical accuracy of femoral canal preparation using postoperative reconstructed computed tomography (CT) images of 75 consecutive total hip arthroplasties performed with a two-pin-based ROBODOC system. Intraoperatively, the robot milled the femoral canal according to the preoperative planning performed with preoperative CT data and the ROBODOC workstation. Postoperative CT data was obtained 1 month postoperatively. Anteroposterior and lateral synthetic radiographs and axial images were reconstructed from CT data on the workstation. The mean difference between the preoperative planning and the postoperative CT images was less than 5% in canal fill, less than 1 mm in gap, and less than 1 degrees in the mediolateral and anteroposterior alignment. Clinical femoral canal preparation using the ROBODOC system results in a high degree of accuracy.

Adult↗

PubMed2003

Comparison of the fit and fill between the Anatomic Hip femoral component and the VerSys Taper femoral component using virtual implantation on the ORTHODOC workstation.

The purpose of this study was to evaluate differences in fit and fill between an anatomic femoral component and a straight tapered femoral component, both of which were designed for proximal fit and fill using the preoperative planning workstation of the ROBODOC system (ORTHODOC). Anatomic Hip (Zimmer) and VerSys Taper (Zimmer) femoral components were each virtually implanted into 50 femora (25 dysplastic femora and 25 anatomically normal femora) using the ORTHODOC workstation. The fit and fill of the femoral components were measured on cross-sectional images. The VerSys Taper femoral components showed significantly better fit and fill than the Anatomic Hip femoral components at the lower corner of the femoral neck cut and the middle of the femoral component in both the dysplastic femora and the anatomically normal femora. The Anatomic Hip femoral components showed significantly better fit and fill than the VerSys Taper femoral components 1 cm proximal from the femoral component tip in both dysplastic femora and anatomically normal femora. There was no significant difference in fit and fill between the two types of femoral component at the center of the lesser trochanter or 1 cm distal from the center of the lesser trochanter in either dysplastic femora or anatomically normal femora. Overall, VerSys Taper femoral components appear to provide better proximal fit and fill than Anatomic Hip femoral components in both dysplastic and anatomically normal femora.

Adult↗

PubMed2003

Scintigraphic image patterns in dysplastic coxarthrosis: evaluation with reference to radiographic findings in 210 hips.

Little is known about scintigraphic image patterns in the various stages of coxarthrosis. We assessed bone scintigraphy in 159 patients (210 hips) with dysplastic arthrosis of the hip. Scintigraphic images were divided into 5 types related to the radiographic stages of the disease. The scintigraphic images showed little, if any, uptake in the stage of prearthrosis. In the early stage, we found an increase in uptake in the weight bearing area in 30% of cases. In the advanced stage, more than half of the cases had an increase in uptake in the medial side of the joint and in the weight bearing area. In the terminal stage, a marked increase in uptake in the weight bearing area was commonest. Since the osteoblastic reaction intensified, a marked increase in uptake was seen not only in the weight bearing area, but also throughout the entire joint. These types of scintigraphic patterns, which change with the stage of coxarthrosis, seem to reflect the natural course of the disease. All hips with rapid progression of the disease showed a marked increase in uptake of radionuclide the entire joint at earlier stages.

Adolescent↗

PubMed2003

Measurements of pelvic flexion angle using three-dimensional computed tomography.

The purpose of the current study was to evaluate whether safe acetabular component position depends on differences in pelvic location between the supine, standing, and sitting positions. The subjects of the current study were 101 patients who had total hip arthroplasty. Anteroposterior radiographs of the pelvis with the patients in the supine, standing, and sitting positions were obtained preoperatively and 1 year after total hip arthroplasty. Computed tomography images of the pelvis were obtained preoperatively. Using image matching between the three-dimensional computed tomography model and anteroposterior radiograph, pelvic flexion angles with the patient in the supine, standing, and sitting positions were calculated. The mean preoperative pelvic flexion angle was 5 degrees +/- 9 degrees (range, -37 degrees -30 degrees ) in the supine position, 3 degrees +/- 12 degrees (range, -46 degrees -33 degrees ) in the standing position, and -29 degrees +/- 12 degrees (range, -62 degrees -10 degrees ) in the sitting position. Because there was much intersubject variability in pelvic flexion angle, it is not appropriate to determine orientation of the acetabular component from anatomic landmarks. In 90% of the cases, the difference in pelvic flexion angle between the supine and standing positions preoperatively was 10 degrees or less. In 90% of the cases, there was 20 degrees or greater extension of the pelvis from the supine position to the sitting position preoperatively, and the safe range of flexion of the hip from anterior prosthetic impingement in the sitting position was 20 degrees or greater than that in the supine position. Preoperative pelvic position in each case was almost completely maintained 1 year after total hip arthroplasty. It is reasonable to regard the pelvic position in the supine position as the functional pelvic position and proper pelvic reference frame in determining optimal orientation of the acetabular component in 90% of cases before and 1 year after total hip arthroplasty, although an adjustment of orientation of the acetabular component was needed for the remaining cases.

Acetabulum↗

PubMed2003

Accuracy evaluation of a shape-based registration method for a computer navigation system for total knee arthroplasty.

This study evaluated the effect of computed tomography (CT) slice thickness, reconstruction pitch, intraoperative data sampling area, and data sampling volume on the accuracy of registration and determined a clinically acceptable trade-off between accuracy and surgical invasiveness. One cadaveric femur and one cadaveric tibia were used. Computed tomography of the femur and tibia were obtained using a helical scanner. Three sets of slice thickness and slice pitch were chosen for data acquisition, and two additional sets of reconstructed data were made. Bone contours were extracted by removing surrounding substrate. Surface models of bones were made from the resulting data. Registration of surface models to real objects was performed by measuring the position of various surface points on various areas of each object using an OPTOTRAK pen-probe (Northern Digital Inc, Ontario, Canada). The following trade-off is proposed as clinically optimal: perform CT with 3-mm slice thickness and 1-mm reconstruction pitch, and sample a periarticular area of 30 sampling points. The accuracy of registration in terms of position and angle was 0.8 mm and 0.6 degrees of bias with 0.2 mm and 0.3 degrees of root-mean-square in the femur, and 0.5 mm and 0.4 degrees of bias with 0.2 mm and 0.3 degrees of root-mean-square in the tibia.

Arthroplasty, Replacement, Knee↗