New visualization tools: computer vision and ultrasound for MIS navigation

A versatile image acquisition method called echo surgetics has been developed for minimally invasive computer-assisted orthopaedic procedures. The principle of echo surgetics is to use freehand three-dimensional (3D) ultrasound to acquire relevant 3D bone surface and point data transcutaneously, eliminating access problems associated with conventional digitizers. The concept has been implemented in three technologies: Echo Point, Echo Matching and Echo Morphing.

Cadaver experiments were carried out to evaluate the accuracy of (a) Echo Point for digitization of the anterior pelvic plane (APP) in total hip arthroplasty, and (b) Echo Morphing for reconstructing the distal femur in minimally invasive knee surgery.

Echo Point provided significantly improved results (p < 0.001) over conventional digitization where mean tilt errors exceeded 20 degrees . The Echo Morphing experiments demonstrated that with a reasonable number of points (ca. 1000) and initial attitude (IA) error (ca. 5-10 mm and 5-10 degrees ) we can obtain an average accuracy of approximately 1 mm that is sufficient for most of clinical applications.