46.1 Goals of Procedure

The presence of posterior bone loss in advanced glenohumeral osteoarthritis (OA) results in increased retroversion and often a biconcave (B2) glenoid. This presents a particularly difficult problem when treating glenohumeral OA with anatomic total shoulder arthroplasty (TSA). Treatment goals of advanced glenohumeral OA with asymmetric bone loss using anatomic TSA include (1) correction of glenoid bony deformity to restore the patient’s native version and inclination, (2) restoration of the location of the native joint line, (3) balancing of the soft tissues, and (4) centering of the humeral head. This chapter will focus on use of the augmented glenoid component and its ability to restore native glenohumeral anatomy (version, inclination, and location of the joint line) in anatomic TSA when posterior bone loss is present.

46.2 Advantages

The correction of pathologic version and posterior glenoid bone loss in shoulder arthroplasty has been shown to improve outcomes by balancing forces across the shoulder joint and re-creating an anatomic alignment of the humeral head and glenoid. Correction of increased glenoid retroversion has been proposed by reaming the high side, bone grafting, or using an augmented glenoid component.

Reaming the high side in cases with moderate to severe posterior glenoid bone loss to match native version can cause significant joint line medialization with increased risk of peg perforation, loss of the stronger cortical bone, and decreased tensioning of the soft tissues. Alternatively, reaming the glenoid in its pathologic plane will result in excessive retroversion of the glenoid component, which can lead to increased rates of osteolysis, and potential component loosening when placed in greater than 15 degrees of retroversion. ^{1 – 6} In contrast, use of bone graft with a standard glenoid component allows correction of version and maintenance of joint line when addressing advanced posterior glenoid bone loss. However, this procedure is technically more difficult to obtain stability of the bone graft and the implant, as stability of the polyethylene component requires bone incorporation. A few level IV clinical studies have demonstrated good clinical success, but a high incidence of radiolucency and complications associated with graft preparation, fixation, and incorporation have been reported. ^{7 – 11}

A recent alternative to correcting severe pathologic glenoid deformity during anatomic TSA has been the use of an augmented polyethylene glenoid component. A variety of augmented polyethylene glenoid designs have been evaluated biomechanically in the recent literature and three are currently commercially available ( Fig. 46.1 ). Biomechanical, computational, and now clinical data have demonstrated the benefits of the use of augmented polyethylene glenoids when addressing significant posterior glenoid wear and deformity. These studies have shown improved clinical function and outcome scores, and the ability to restore native glenoid anatomy (version, joint line, and humeral head centering). ^{1 – 14}

46.3 Indications

The primary indication for an augmented glenoid component is glenohumeral OA with an intact rotator cuff and posterior glenoid bone loss not correctable with a standard component. This is primarily determined through preoperative 3D planning using a thin-cut CT scan and associated Food and Drug Administration (FDA) approved planning software. Prior literature has shown a high (16%) revision rate in B2 glenoids treated with standard glenoid components at an average of 77 months (14–180 months) of follow-up. ¹⁵ We believe an augmented glenoid component is a reliable option for joint line restoration, version correction, and centering of the humeral head for B2 glenoids, and there is early literature supporting this claim. ^{13 , 14} Currently, the B2 glenoid is the most common pattern of moderate to severe bone loss in which we utilize an augmented glenoid component.

46.4 Contraindications

Contraindications to use of an augmented glenoid component include rotator cuff deficiency and very severe bone loss. With the advances in preoperative planning and implant designs, we have identified potential limitations to the use of augmented glenoids when bone loss or retroversion is very severe (e.g., B3- or C-type glenoids). In these cases of advanced bone loss or pathology, reverse TSA with or without bone grafting may be a more reliable option for implant stability and longevity.

46.5 Preoperative Preparation/Positioning

46.5.1 Preoperative Planning

Currently, we use 3D CT imaging for preoperative planning in cases of moderate or severe posterior glenoid bone loss, as this allows more precise determination of the optimal implant choice based on the degree of pathologic correction and joint line restoration that is possible with augmented or standard glenoid components ( Figs. 46.2, 46.3 ). Prior studies have shown that using 3D CT preoperative planning can help predict the amount of correction achievable using standard and augmented glenoids and improves glenoid implant positioning postoperatively. ^{16 – 18}

Related posts:

45 Posterior Glenoid Wear in Total Shoulder Replacement: Eccentric Reaming 48 Convertible Components in Shoulder Arthroplasty 53 Internal Latissimus Transfer for Reverse Shoulder Arthroplasty 43 Stemless Anatomic Shoulder Replacement 47 Bone Grafting for B2/B3 Glenoid 39 Deltopectoral Approach for Shoulder Arthroplasty

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