Augmented Glenoid Components

As discussed in the section on glenoid augmentation for the anatomic shoulder arthroplasty, glenoid bone loss presents a difficult problem for anatomic and reverse shoulder arthroplasty. With existing bone loss, many prefer to perform an RSA. This is thought to be a better option due to the decreased humeral migration and ultimately asymmetric poly wear with the more constrained RSA component as compared to the TSA. Even with the advantage of RSA glenoid implants, there are still minimum requirements for baseplate placement. The implant goals are typically cited as version within 5–10 degrees of neutral, neutral to mildly inferior inclination, a minimum of 50% baseplate contact with possibly more with augmented baseplates [97,98].

Glenoid augments assist in achieving these goals by increasing the baseplate support with less glenoid reaming. This also has the added benefit of preserving more native bone stock and increasing glenoid lateralization. When evaluating glenoid bone loss, cases are typically broken down into primary cases with bone loss or erosion and revision cases.

For primary cases, the bone loss is usually angular deformities—either version or inclination. Version abnormalities are associated with primary osteoarthritis, post-traumatic arthritis and post-capsulorrhaphy arthritis. Version change of >20 degrees requires either an augmen<sup>t</sup> or bone graft to avoid excessive reaming and to achieve the ideal baseplate position. Inclination deformities are associated with cuff tear arthropathy. Hamada 4 and 5 changes are usually associated with superior erosion but can occasionally be central erosion. Again, an augmented baseplate can improve the seating with less glenoid reaming, and inclination of >10–15◦ requires augmen<sup>t</sup> or bone graft rather than asymmetric reaming.

For revision cases, augments are more frequently used as opposed to autograft due to the lack of excess bone graft (e.g., humeral head) available. Bone loss in revision cases can be complex and variable including peripheral bone loss, cavitary ventral bone loss, angular erosive deformities and, most complex, combined defects.

Several augmen<sup>t</sup> options exist to address these bone loss patterns. First, there are noncustom implants. These require some glenoid reaming and are angled metallic augments that can be either a full or half wedge ranging from 10–30 degrees. These augments increase the baseplate thickness, so lateralized glenospheres may not be required. Second, there are custom implants. These are designed pre-operatively off a CT scan platform and are based on an individual patient's deformity. They typically do not require glenoid reaming. Custom implants are best used in the setting of complex, combined glenoid bone loss patterns (e.g., peripheral and cavitary), severe peripheral defects severely compromising the glenoid vault walls and severe angular deformity with central bone loss. This is more often indicated in the revision setting.

The senior author's preference in cases without glenoid bone loss is to use a standard lateralized baseplate. In cases of glenoid bone loss, he will use an off-the-shelf augmen<sup>t</sup> for <5 mm bone loss (Figure 6), BIORSA for 5–10 mm of bone loss, structural allograft or autograft on the glenoid for 10–20 mm of bone loss, and a custom baseplate (Figure 7) or 2-stage iliac crest bone graft (ICBG) reconstruction for >20 mm of bone loss.

**Figure 6.** RSA with augmented baseplate. Axillary X-ray of augmented glenoid baseplate.

**Figure 7.** Case of severe glenoid bone loss treated with RSA with custom glenoid component. (**Left**) Axial CT scan of right shoulder status post antibiotic hemiarthroplasty spacer for prior prosthetic joint infection. (**Middle**) AP X-ray of RSA with custom glenoid component. (**Right**) Axillary X-ray of RSA with custom glenoid component.

#### **4. New Perspectives and Innovations in Revision Shoulder Arthroplasty and Complications**
