[CRIGOS: development of a compact robot for image-guided orthopedic surgery]. / CRIGOS--Entwicklung eines Kompaktrobotersystems für die bildgeführte orthopädische Chirurgie.

In this paper, we present a medical robot system dedicated to support the surgeon during challenging tasks within orthopedic interventions. The main goal of this work is to develop a system as technically simple as the surgical requirements allow to keep its cost and complexity to a minimum. Therefore, we primarily focus on calibrated X-ray imaging for image acquisition, an easy registration procedure and robotic execution using a positioning device with simple parallel kinematics. Examples of different orthopedic interventions using the compact robot system for image-guided orthopedic surgery (CRIGOS) are presented, as well as various modes of execution of the device.

Locating femoral graft placement from lateral radiographs in anterior cruciate ligament reconstruction: a comparison of 3 methods of measuring radiographic images.

Graft positioning in anterior cruciate ligament (ACL) reconstruction is usually documented from lateral postoperative radiographs. The purpose of this study was to compare 3 measurement methods for femoral graft placement in 50 patients with ACL reconstruction. Intraoperative radiographic images were obtained and divided into 2 groups. The first group showed suboptimal projections, with out-of-plane rotations causing the femoral condyles to not be perfectly overlapped. The second group showed good projection, with optimal rotation and fully overlapped femoral condyles. In our study, only the measurement technique described by Amis produced data with the least measurement error when multiple observers assessed both groups. It is recommended that Amis' method be used to measure femoral ACL graft position so that reliable data are available for comparison between medical centers.

Sagittal plane imaging parameters for computer-assisted fluoroscopic anterior cruciate ligament reconstruction.

Reproducible graft placement in anterior cruciate ligament (ACL) reconstructions is considered to be a critical factor affecting the successful clinical outcome of the procedure. Many current ACL instrument systems rely on intra-articular landmarks to guide the ACL tunnel placement. However, most of these instrument systems use mobile soft tissues as landmarks. We hypothesize that consistently identifiable radiographic contour landmarks can be established that can be used to improve the reproducibility of graft tunnel placement in fluoroscopically and computer-assisted ACL reconstructions. For the tibia, magnetic resonance imaging (MRI) scans showed the average ACL attachment site to be projected at 46% on a line extending from the anterior to the posterior cortices. Intraoperative fluoroscopic images were checked for the reproducibility of this line and its clinical use. For the femur, lateral radiographs demonstrated a consistent relationship between the intercondylar roof line (Blumensaat's line) and the nearly circular profile of the posterior and inferior contour of the lateral femoral condyle. The middle of this circular profile is consistently projected on Blumensaat's line at 66% of its anterior-to-posterior direction. Intraoperative images were used, which showed the aiming drill at the point of entering the lateral femoral condyle. Instead of determining the femoral attachment site relative to Blumensaat's line, we can thus determine its position relative to the center of the circle. Based on intraoperative x-rays, the proposed femoral ACL attachment site can be projected on a line parallel with the Blumensaat's line from the circle center in the posterior direction. Our results indicate that there are consistently identifiable radiographic features on the tibia and femur contours that can be used for fluoroscopic and computer-assisted guidance of ACL graft placement.

Patellar tendon graft position after anterior cruciate ligament reconstruction. Interobserver variability on lateral radiographs.

We compared the reliability and validity of graft position measurements made by 4 orthopedic surgeons on intraoperative radiographs obtained using fluoroscopic control and postoperative radiographs obtained from the same 17 patients 6 weeks after ACL reconstruction. Measurements from postoperative radiographs varied significantly more than those from intraoperative radiographs. There was little agreement between the postoperative and intraoperative measurements of the tibial and femoral graft position. We conclude that postoperative radiographs are not a sufficient tool for assessing graft placement after ACL reconstruction using patellar tendon autografts. In order to consider graft position in follow-up studies and to compare results from various surgeons, we suggest intraoperative fluoroscopy to produce radiographs for accurate and reliable measurements.

Computer assistance in arthroscopic anterior cruciate ligament reconstruction.

Accurate placement of the graft is considered one of the most important factors in anterior cruciate ligament surgery. However, reconstruction with contemporary guiding systems still can result in unacceptable graft placement variability. To improve the reproducibility of graft placement, intraoperative visual feedback was added to the arthroscopic technique. First, fluoroscopic visualization was added to evaluate guidewire placement before tunnel drilling. Second, computer graphic overlays were added to the fluoroscopic view. Three groups of patients were treated: 29 patients with arthroscopy, 53 patients with fluoroscopy added, and 50 patients with computer overlays added. Graft placement variability was reduced significantly with fluoroscopic visualization. Computer overlays resulted in additional significant reductions in graft placement variability. Simple visual enhancements seem to be useful in improving the accuracy of arthroscopic anterior cruciate ligament reconstruction.