51.1 Goals of Procedure

The goals of the procedure are to achieve predictable stable fixation of the glenoid component, restore glenoid version and bone stock, and obtain predictable clinical outcomes while limiting complications and failure.

Posterior glenoid bone loss (PGBL) can present a difficult challenge when considering shoulder replacement for the treatment of primary glenohumeral osteoarthritis. As described by Neer and Friedman, and later classified by Walch, glenoid morphology can change with the progression of the arthritic process. Advanced osteoarthritis can result in glenoid bone loss, retroversion of the glenoid, loss of normal glenoid vault anatomy, and posterior subluxation of the humeral head. When altered glenoid morphology corresponding with Walch’s classification of B2, B3 or C is present, results with anatomic shoulder replacement surgery can be unpredictable and have been associated with high complication profile. ^{1 – 3} The use of eccentric reaming, glenoid bone grafting, augmented glenoids, and reverse shoulder arthroplasty (RSA) has been described. When correction of glenoid version and recentralization of the humeral head are achieved, satisfactory results can be obtained. However, this can prove to be a surgical challenge. Compared to total shoulder arthroplasty (TSA) in patients without significant PGBL, decreased functional results, increased pain levels, and higher rates of glenoid loosening and complications have been reported. ^{4 – 13}

When PGBL and retroversion exceed the boundaries of safe eccentric reaming or there is insufficient bone for glenoid fixation, structural support using bone graft or other material has been attempted with TSA. The use of bone grafting is generally associated with a high percentage of radiolucency, glenoid component failure, graft failures, and instability. ^{2 , 3} The senior author reported on 17 patients who underwent bone grafting. ⁵ Despite average correction of retroversion to 4 degrees, 29% required revision surgery for fixation failure and 47% unsatisfactory results. This experience led to the development and use of RSA with a shaped humeral head autograft to the glenoid in these difficult patients.

51.2 Advantages

Grafting the glenoid with a shaped humeral head autograft allows restoration of glenoid bone stock and version. RSA allows for stable graft fixation with the baseplate and avoids recurrent posterior instability associated with anatomic shoulder arthroplasty.

51.3 Indications

This technique is considered for patients with glenohumeral arthritis associated with significant glenoid bone loss. Though described for PGBL, this technique can also be predictably used in patients with anterior, superior, or central glenoid bone loss as well.

51.4 Contraindications

Contraindications to shoulder arthroplasty include active infection, significant medical comorbidity, Charcot’s arthropathy, and severe neurologic pathologies. Contraindications for RSA also include axillary nerve palsy and deltoid dysfunction. Finally, if glenoid bone stock is severely limited and/or the bone quality is inadequate for stable baseplate fixation, we would recommend against this procedure.

51.5 Preoperative Preparation/Positioning

Preoperative evaluation should always emphasize the patient’s history of disease, any prior treatment, and medical comorbidities. Physical examination should assess motion, strength, deformity, cervical disease, and neurologic function. Preoperative radiographs should include internal and external rotation Grashey, scapular Y, and axillary views. Advanced imaging should include at minimum a 2D CT scan. We recommend obtaining a 3D reconstruction CT scan with minimum 1-mm thin cuts. An MRI is not felt to be necessary. The surgeon should assess the glenoid morphology, bone loss, retroversion, inclination, and subluxation of the humeral head in relation to the glenoid. The use of imaging software capable of appropriately setting the axis of rotation along the scapular line can help enable better understanding of glenoid morphology. This information will be used to help plan the appropriate starting point and trajectory for guide pin placement. Recently, 3D planning software and patient specific guides have become more available and can be utilized to improve guide pin placement if desired.

The patient is positioned in the beach-chair position. We prefer the head of bed to be at roughly 35 degrees. A towel or small bump is placed just medial to the medial border of the scapular in order to rotate the scapula anteriorly. This helps deliver the glenoid anterior, providing better exposure to the posterior glenoid neck. We prefer using an arm holder; however, use of a padded Mayo stand is also an option. We prefer utilizing both a regional interscalene nerve block and general anesthesia.

51.6 Operative Technique

The surgical techniques for RSA have been well described. ^{14 , 15} The majority of this procedure follow these techniques, with variations in the harvesting of the humeral head autograft, glenoid preparation, and shaping of the humeral head autograft. We prefer to use a long post baseplate (Tornier, Edina, MN), two peripheral compression screws, and two peripheral locking screws; however, other baseplate designs can also be used.

Using a standard deltopectoral approach, the proximal humerus is exposed and prepared using the standard technique. The long head of the biceps tendon is tenodesed to the superior border of the pectoralis major insertion. The subscapularis tendon is released using the surgeon’s preferred technique, and the humeral head is dislocated and delivered through the deltopectoral interval. A 2.5-mm guide wire is placed in the center of the humeral head perpendicular to the planned humeral head cut and driven through the lateral humeral cortex for stabilization. Using a cannulated system, the glenoid reamer is used to flatten the humeral head just beyond the articular surface. A 29-mm hole saw with a central 8-mm cannulated drill ( Fig. 51.1a) is then passed along the wire to obtain a deep cylinder graft and a central hole ( Fig. 51.1b). The guide wire is removed and the humeral head cut is made to the desired depth of the graft. We prefer starting with at least a 15-mm graft. The donut-shaped graft is removed ( Fig. 51.1c) placed in a saline-soaked sponge and saved on the back table. The remaining humeral preparations can be completed now or after the glenoid has been addressed.

51.6.1 Glenoid Preparation

The glenoid is exposed and cleared of all remaining cartilage and soft tissue. A complete capsular release is performed and the subscapularis is elevated off the anterior glenoid neck ( Fig. 51.2 ). The glenoid centering point is palpated anteriorly and used to determine the correct orientation and version of the central guidewire. ¹⁶ The guide wire is placed in this version, 0 to 10 degrees of inferior tilt, and approximately 14 mm superior to the inferior border of the glenoid. When a significantly altered glenoid morphology is present, these measurements may be difficult to achieve. Imaging software and patient-specific guides can also be used to achieve appropriate placement of the guide wire. Once the guide wire is placed, the glenoid is reamed using a cannulated glenoid reamer until the anterior glenoid is flat to the level of the guide wire. This results in a flat anterior surface with the neoglenoid extending beyond the guide wire posteriorly ( Fig. 51.2b). The neoglenoid is trephinated and decorticated to promote bleeding and autograft incorporation. The center hole is then drilled using a cannulated drill per implant technique.

Related posts:

45 Posterior Glenoid Wear in Total Shoulder Replacement: Eccentric Reaming 46 Posterior Glenoid Wear in Anatomic Total Shoulder Replacement: Augmented Polyethylene Glenoid Component 48 Convertible Components in Shoulder Arthroplasty 43 Stemless Anatomic Shoulder Replacement 47 Bone Grafting for B2/B3 Glenoid 39 Deltopectoral Approach for Shoulder Arthroplasty

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