The ArthroNav Project

Computer Assisted Navigation in Orthopedic Surgery using Endoscopic Images

ArthroNav aims the development of a navigation system for the reconstruction of the Anterior Cruciate Ligament (ACL) by minimally invasive surgery (MIS). The ACL is located in the center of the knee joint and runs from the femur to the tibia. The steps of the arthroscopic reconstruction can be summarized as follows: (i) harvest a tendon graft from the patellar or hamstring; (ii) remove the torn ligament; (iii) open drill holes in the tibia plate and femur notch at the attachment site of the original ligament, (iv) pull the replacement graft through the open tunnel and into the knee joint; and (v) held the tendon graft in place with screws.

This procedure must be performed by well trained surgeons with a lot of experience. The accurate positioning of the drill holes from the outside is the most critical and difficult step. Small errors in the graft placement can lead to abnormal tensions during motion, cause pain and new injuries, and ultimately force to a correction surgery.

Anterior Cruciate Ligament (ACL) scheme

A surgical navigator is a visualization system for assisting the medical practitioner. It provides real-time positional information about instruments and tools with respect to a target organ (bones). This is typically achieved using opto-tracking technology, with a stereo head detecting a set of LED markers rigidly attached to instruments and organs.

Aquisition system

Saint Operation scheme

Unfortunately, opto-tracking can not be directly applied to MIS because the organs are not visible from the outside. We propose to solve the problem by reconstructing the knee joint from the arthroscopic video stream and register the result with a pre-operative volumetric images (typically CT scan). This enables to estimate the 3D pose of the femur/tibia with respect to the arthroscopic camera, that is optically tracked in the world coordinate system where the surgical tools are referenced.

Endoscopic image/p>

Pre-operative bone model

Despite of the recent developments in computer vision, working with arthroscopic images remains a challenging problem. There are several difficulties that must be overcome, from correctly modeling and calibrating the endoscope to recovering the scene structure, passing by establishing point matches, and accurately computing the camera motion. This website shows the progresses in these different research fronts.