420 - Anatomical Versus Reverse Shoulder Arthroplasty

will need to take a rongeur and remove the cancellous bone from the humeral head in case a bone graft is needed later in the case. After the removal of the two pins and the cutting guide, broaching will begin. The surgical technologist will hand the surgeon a broach that is 2 or 3 mm smaller than the reamer that was left in the humeral canal and the surgeon will broach it up until they get to the corresponding size. Once this is complete, the broach will remain in the humer- us while work on the glenoid begins. The surgeon may ask for a round metal plate to place on top of the broach to protect the bone. To prep the glenoid, a sizer that also will act as a pin guide, will be placed on a handle. The general rule of thumb is to start with a medium sizer. A guide pin on power will be placed through the sizer and into the center of the glenoid. This will be followed by the reamer that corresponds to the sizer that was chosen, which is placed over the guide pin and removes any remaining cartilage and cortical bone left on the glenoid. For an anatomic total shoulder, a central drill bit will be placed over the guide pin and drilled into the glenoid. This will be followed by a peripheral peg drill guide. As holes are drilled, anti-rotation pegs will be placed to keep the guide from moving. A glenoid trial then can be handed to the sur- geon for a trial reduction. The glenoid component comes in a number of variations. It can have a porous-coated larger center post with a number of smaller polyethylene pegs. The implant might contain all polyethylene pegs, or it may have a keel in place of the peg-post construct. When it is time to insert the glenoid component, the cement from the Toomey syringe will be placed in any holes that were created in the glenoid that will house polyethylene. The humeral head trial may not immediately sit perfectly, therefore, the surgeon will adjust it in order to maximize the coverage over the resected bone. The trial head will have marks with letters on the underside, which the surgical tech- nologist needs to take note of so they can replicate the offset when putting together the implant. For a reverse shoulder arthroplasty, after using the cor- rect size glenoid reamer (different from the one used for an anatomical shoulder), the surgeon is ready for the baseplate implant. Once it is placed in the patient’s shoulder socket, a center hole guide and drill are handed to the doctor, fol- lowed by a depth gauge. The appropriate length screw is then inserted. This is followed by the drilling of outer holes using a peripheral guide with a bushing insert and a drill bit small- er than the one used for the center hole. Once all the screws are inserted, a trial head (called a gle- nosphere) can be placed on the base- plate. The glenoid now becomes the head of the ball- and-socket joint in a reverse shoulder. The glenosphere comes in different sizes to help ensure that the patient’s new shoulder is stable and does not dislocate. The surgeon will determine if any offset is needed for the glenosphere, just like with the head on an anatomic total shoulder. If any offset is needed, it must match the trial when putting together the actual implant. The socket on a reverse shoulder then will be attached to the stem. It is comprised of a metal tray and a polyethyl- ene bearing that also comes in an assortment of sizes that help match the diameter of the glenosphere, and provide a buildup of polyethylene if the shoulder joint is still unstable. These two implants will snap together. C O M P L I C A T I O N S A N D P O S T - O P Complications from shoulder replacement surgery can include injury to the nerves and blood vessels, a peripros- thetic fracture, dislocation of the shoulder joint, and loos- ening of the prosthesis. A sling is placed post-operatively, and the patient is usually discharged one to two days fol- lowing the procedure. Physical therapy will be prescribed and patients will continue to wear the sling for six weeks after surgery with limitations on lifting. It may take at least six months for patients to be able to resume certain vigorous activities, such as golfing or swimming. In a reverse shoulder arthroplasty, the humerus houses the socket while the glenoid becomes the site of attachment for theball of the shoulder joint. | The Surgical Technologist | DECEMBER 2018 550