Glenohumeral Arthritis: Total Shoulder Arthroplasty With Glenoid Bone Graft

John P. Scanaliato

Gregory P. Nicholson

INDICATIONS AND CONTRAINDICATIONS

Patients undergoing anatomic total shoulder arthroplasty (TSA) for end-stage arthritis will have some degree of glenoid wear, a deformity commonly categorized by the Walch classification¹^,² (Figure 47-1). In addition to providing a common language by which to classify the pattern of wear, this classification has also been found to correlate with clinical outcomes.³^,⁴ In patients who have exhausted conservative treatment and require anatomic total shoulder, the glenoid wear pattern and deformity must be addressed for a successful arthroplasty. This chapter will focus on the technique of utilizing the patient’s native humeral head as the source for posterior glenoid bone grafting (PGBG) to address the glenoid wear deformity. This strategy is attractive as it not only serves to correct pathologic retroversion but also restores bone stock, provides a biological milieu favorable for component incorporation, and can prevent component penetration through the glenoid vault.⁵^, ⁶^, ⁷^, ⁸^, ⁹ ^and ¹⁰ Furthermore, bone grafting helps to restore prepathologic biomechanics, as it avoids glenoid component medialization, serves as a restraint to posterior subluxation, and normalizes the force transmission across the glenohumeral joint.

FIGURE 47-1 A-C, Sawbones model demonstrating a typical posteroinferior glenoid wear pattern. Note the relative well-preserved anterior glenoid surface and the posterior subluxation of the humeral head. D, Axial CT scan of a 60-year-old right-hand dominant patient demonstrating a B2 glenoid with marked posterior wear.

We do not have a hard threshold value for glenoid retroversion beyond which PGBG is always utilized. Rather, if we feel that asymmetrical anterior reaming would result in compromised glenoid bone stock, we plan for PGBG. We have utilized this technique for patients with glenoid version ranging from −20° to −45°. In our experience, we rarely utilize this technique for patients with retroversion less than −15°, a threshold in line with prior anatomic studies.¹¹

Beyond glenoid retroversion, the indications for anatomic shoulder arthroplasty (TSA) with PGBG do not differ from our standard indications for TSA, meaning an intact rotator cuff and glenohumeral arthritis as the underlying diagnosis.

PREOPERATIVE PLANNING

Preoperatively, all patients routinely undergo radiographic evaluation including a true anteroposterior view of the glenohumeral joint, a scapular Y view, and an axillary lateral view. The glenoid version can be calculated on the axillary radiographs per the method of Friedman et al.¹² This view is also utilized to evaluate for humeral head subluxation. It is well accepted that 3D computed tomography (CT) scan is a more accurate and reproducible imaging modality than plain radiographs, and, as a result, we always recommend a CT scan with preplanning software in all cases of significant wear deformity.¹³^,¹⁴ This imaging study also allows the operative surgeon to simulate their proposed surgical plan.¹⁴^,¹⁵ Furthermore, through this modality, wear characteristics and rotator cuff muscle status can be assessed, thus enabling a more thorough preoperative plan. Careful assessment of rotator cuff muscle volume and quality, per the Goutallier or Fuchs classification, is of paramount importance, as higher degrees of fatty infiltration and atrophy have been shown to portend poor clinical outcomes following shoulder arthroplasty.¹⁶^, ¹⁷ ^and ¹⁸

Careful evaluation of the magnitude and location of wear is critical. It is important to recognize that these are not symmetric wear deformities, as they are typically a posteroinferior wear pattern (Figure 47-1). Intraoperatively, the goal is to implant the glenoid component close to native retroversion (between −4° and −10°) and on solid bone. This point requires emphasis; the glenoid should not be corrected to 0° of retroversion. To address the glenoid, there are two general strategies one can utilize: the first is to “lower the front,” typically accomplished through asymmetric anterior glenoid reaming. The other accepted strategy for the management of posterior wear is to “raise the back.” Recently, augmented all-polyethylene glenoid components have become available, the indications and techniques of which fall beyond the scope of this chapter, and is one intraoperative strategy through which one can “raise the back.”¹⁹^,²⁰ The other strategy through which to accomplish this goal is a PGBG, for which our preferred technique follows.

TECHNIQUE

All procedures are performed in a modified beach chair position. We prefer a combined anesthesia technique utilizing an interscalene regional block, but we also use general anesthesia to provide maximum muscle relaxation. In over 90% of cases, we utilize an indwelling interscalene catheter (On-Q Pain Relief System, Avanos, Georgia, USA) that will provide 3 days of continuous analgesia.

We do not routinely use a commercially available arm holder, as we feel it interferes with surgical assistant positioning. The operative arm is supported under the drapes by a 9-by-9 inch well-padded arm board, which easily slides up and down the rail on the operative table to allow for dislocating the operative limb. A three-towel roll is also placed at the medial border of the scapula to hold the scapula forward and prevent rotation around the chest wall with retraction, ultimately facilitating glenoid exposure. The surgeon must have a “straight on” exposure to the posterior glenoid, and small arm position movements can facilitate this exposure. With the limb free of an articulating arm holder, small rotational and elevation movements can provide the exposure needed. Also, this allows retractors to be manipulated for optimal exposure without overtensioning the soft tissues.

Exposure

A standard deltopectoral approach is utilized. The deltopectoral interval is developed, and the cephalic vein is taken laterally. The clavipectoral fascia is released lateral to the conjoint tendon, and the subdeltoid adhesions are released with a small Cobb elevator to free up the subdeltoid gliding plane. The rotator interval is opened with Mayo scissors to the base of the coracoid. These maneuvers will typically improve external rotation.

The subscapularis can be managed by the surgeon’s preference. We prefer a tenotomy technique, but numerous studies have shown no clinical difference between a tenotomy, a peel, or a lesser tuberosity osteotomy technique.²¹^,²² The subscapularis tendon is tagged with three 0-braided nylon sutures (one superior, one middle, and one inferior), and all are attached to a single hemostat. A 360° subscapularis release is performed, facilitated by traction on the muscle-tendon unit using the tag sutures. Mayo scissors are used to divide between the upper rolled border down to the base of the coracoid, and the underlying capsule is released off the glenoid rim. This release is carried down around the 6-o’clock position and up into the posteroinferior capsule to almost the 8- to 9-o’clock position. The inferior capsule is then released at the inferior border of the subscapularis muscle by finding the interval between this muscle and the capsule. This is carried directly to the glenoid behind (posterior to) the muscle layer of the inferior subscapularis down to the rim of the glenoid at approximately the 4-o’clock position in a right shoulder. This releases the subscapularis in a circumferential fashion and facilitates exposure. Thus, the anterior, inferior, and posteroinferior capsule have been released off the glenoid with Mayo scissors. This is a critical step to facilitate exposure to the posterior aspect of the glenoid. Also, the inferior capsule is released off the humeral neck with blunt dissection, to gain motion and exposure.

Humeral Head Osteotomy

At this point, the humeral head can typically be easily dislocated. Two Darrach retractors are placed, one anteriorly between the humerus and medial glenoid and another behind the humerus, over the top of the rotator cuff, to “shoehorn” it forward. Any remaining osteophytes are removed at this stage, as is any residual capsular tissue. A small Hohmann retractor is placed between the supraspinatus and the top of the humeral head to protect this critical structure during the humeral head cut. We prefer an anatomic neck cut, but the osteotomy may be based on the implant system utilized. We like to mark the anatomic neck circumferentially with a needle-tip cautery. This gives the surgeon a visual guide to follow. As we are trying to utilize the humeral head without damage to the joint surface, we do not recommend an intramedullary guide as it creates a defect or hole in the convex surface. The osteotomy is performed with an oscillating saw, and it is critical that the head fragment is not ejected by the saw action and falls to the floor. An assistant has control of the humeral head and typically the last 10% of the osteotomy is completed with an osteotome, and the head is handed off carefully and saved, as it is the source of the bone graft.

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