Richard S. LaBarca

Surgical navigation for total hip replacement with the use of hipnav

HipNav, an image-guided surgical navigation system, is presented. The system was developed to measure and guide the placement of prosthetic components in total hip replacement surgery (THR), it incorporates a 3-dimensional preoperative planner with a simulator and an intraoperative surgical navigator. Coupling optimized preoperative planning with accurate surgical navigation will assist the surgeon in properly orienting the components, minimizing the risk of impingement and dislocation. Intraoperatively, the system uses image-guided tools to assist in accurate placement of the acetabular cup. The acetabular implant is placed in the planned position with the aid of a simple “aim-and-shoot” interface. The actual measurements of version and abduction are also provided. The use of this new class of operative sensors has been incorporated into a regular surgical routine. There are few additional steps necessary, therefore, for the image-guided procedure, which does not add significantly to the total time of surgery. We expect that these tools will lead to less invasive and more accurate THR surgery and directly relate patient outcomes to measured surgical practice.

A Classification Proposal for Computer-Assisted Knee Systems

Computer-Assisted Surgery (CAS) combines various enabling technologies to help surgeons meet and exceed quality requirements in performing knee surgery. Emerging CAS systems for the knee already include applications for TKR, ACL reconstruction and tibial osteotomies. In this paper we propose a general scheme to classify computer-assisted knee systems currently in use and under development, with an emphasis on surgical navigation systems. A literature review and available commercialized product analyses allowed us to sort the different computer-assisted systems in several categories. We proposed a classification scheme relies upon medical criteria instead of solely technical criteria (such as localizer properties and computer specifics). New concepts in computer-assisted surgery can easily fit into this classification framework.

Calibration Method for Determining the Physical Location of the Ultrasound Image Plane

This paper describes a calibration method for determining the physical location of the ultrasound (US) image plane relative to a rigidly attached 3D position sensor. A calibrated US probe can measure the 3D spatial location of anatomic structures relative to a global coordinate system. The calibration is performed by aiming the US probe at a calibration target containing a known point (1 mm diameter sphere) in physical space. This point is repeatedly collected at various locations in the US image plane to produce the calibration dataset. An idealized model of the collection process is used to eliminate outliers from the calibration dataset and also to examine the theoretical accuracy limits of this method. The results demonstrate accurate and robust calibration of the 3D spatial relationship between the US image plane and the 3D position sensor.

CupAlign: Computer-Assisted Postoperative Radiographic Measurement of Acetabular Components Following Total Hip Arthroplasty

Clinical problems following total hip replacement surgery, such as dislocation and implant wear, remain as significant clinical problems with many contributing factors. Although it is intuitive to surgeons that acetabular component alignment is one important factor, large clinical series have produced conflicting results with respect to cup alignment as a risk factor in predisposing to dislocation. One reason is that postoperative measurements of alignment are limited to single or biplanar radiographic measurements. However, the radiographic measurements are limited only to radiographic alignment and may not accurately detail true anatomic orientation of the cup. In this paper, software designed to accurately measure radiographic alignment is described. Postoperative measurements using this system are compared to the actual intraoperative measurements of cup orientation determined by the HipNavTM image-guided surgical system to assess the accuracy of radiographic evaluation of cup orientation.

A Computer-Assisted ACL Reconstruction System Assessment of Two Techniques of Graft Positioning in ACL Reconstruction

KneeNavTMACL, a CT-based surgical navigation system, is used to demonstrate two fundamental requirements for a practical computer-assisted surgical device: 1) it can guide the surgeon with the accuracy required for successful graft placement, and 2) this guidance can be achieved through a simple and intuitive interface. A series of ACL reconstruction preparation procedures were performed on foambone models using traditional arthroscopic techniques. Half of the procedures were done using conventional techniques, the other half were performed with KneeNavTMACL guidance. Resulting tunnel and femoral graft site locations were measured via radiographic and computer means, and the two techniques are compared. Ease of system use is also assessed.

A Framework for Determining Component and Overall Accuracy for Computer Assisted Surgery Systems

Computer assisted surgery (CAS) systems have generated a great deal of interest in the research and medical communities due to their promise of improved results with less invasive access to the surgical site. While some systems have been checked against a minimum acceptable standard set by the system’s developers, no overall methodology is in place to insure that a system is thoroughly characterized. A framework to assess the accuracy of CAS systems will provide developers and researchers with a common starting point with which to test their systems, and will provide surgeons with a consistent basis for comparing different systems. We describe this framework and its application to the HipNav system.