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CT Navigation Helps Surgeons To Optimize Total Shoulder Arthroplasty

Computers in the surgery suite are hardly revolutionary; they’ve been instrumental in advancing surgery techniques for more than three decades. But with advances in the last 5 years, more orthopaedic surgeons have begun using computer-assisted navigation (CAN) to overcome challenges and complexities associated with total shoulder arthroplasty.

Richard J. Friedman, M.D.Chief of Shoulder and Elbow Surgery in the Department of Orthopaedics and Physical Medicine at MUSC Health, uses computerized tomography (CT) navigation preoperatively to plan all his procedures and intraoperatively for many of his total shoulder replacement surgeries, particularly reverse shoulder arthroplasty.

Friedman says that CT navigation offers important advantages for the surgeon and the patient, specifically enhanced precision in placing the glenoid component and helping to minimize complications. CT navigation can also help optimize screw length and purchase, both of which are important for fixation and stability in reverse total shoulder arthroplasty. 

Computer-assisted navigation has given me more options, particularly for reverse total shoulder arthroplasty,” he says. Total shoulder replacement has unique challenges because the shoulder joint is not a true ball-and-socket joint, but more like a ball against a wall, and the socket is a fairly small structure. If a patient has bone loss or glenoid deformity, that can present even more challenges. Because CT is more precise, it helps us place the component in the most optimal position and minimize complications.”

Using CAN may add a few minutes to the procedure, but the additional time is negligible, Friedman says, especially for increased accuracy during complicated procedures.

“Theres a certain margin of error in glenoid component placement that can be reduced significantly when CAN is used pre- and intraoperatively,” he says.

CT navigation comprises three steps: data acquisition, registration and tracking. The data, or images, are obtained through CT scans and used for registration and tracking. Registration is relating the CT images to the anatomical position of the surgical area by using markers. Tracking is the feedback from the measurement devices regarding the orientation and relative position of tools to bone anatomy.

The patient is placed in a position reminiscent of reclining in a beach chair, and the navigation system is set up near the hip opposite the shoulder set for replacement. 

Three trackers are used: the glenoid, the probe and the tool tracker. After calibrating the probe and the tracker, Friedman makes an incision to expose the coracoid and places the tracker on the bone and oriented toward the camera. Accurate placement is essential because it cannot be moved once it is affixed to the bone.

He uses the probe tracker to identify the anatomical landmarks that correspond to the images on the screen. Under direct, real-time imagery, reaming of the glenoid and drilling for the center cage and peripheral screws (for reverse arthroplasty) are then performed, with the computer guiding the position of the instruments in the surgeon’s hands.  Once the computer-assisted portion of the surgery is complete, Friedman removes the G tracker and coracoid block before inserting the anatomic glenoid component for anatomic shoulder replacement or the glenosphere component for reverse shoulder replacement. 

“A key advantage of CAN is that it tracks in real time, so a surgeon can make adjustments if needed,” he says.

The Division of Shoulder and Elbow Surgery at MUSC Health is one of the busiest centers for total shoulder replacement in South Carolina, drawing challenging primary and revision patients from around the state. Patients range in age from their 20s to their 90s and include the chronically challenged as well as those with arthritis, rotator cuff tears and trauma.

Patients typically remain in the hospital just overnight and begin physical therapy after two weeks to strengthen their muscles and regain range of motion and function.

“Our goal is for our patients to have the replacement as long as possible and function as well as possible,” Friedman says. Computer-assisted navigation allows us to do a better job for an improved outcome so the patient can regain function and mobility and have the prosthesis last as long as possible.”

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