Reverse Total Shoulder Arthroplasty for Rotator Cuff Arthropathy

Peter Silvero, MD

Michael A. Wirth, MD

Dr. Wirth or an immediate family member has received royalties from DePuy; is a member of a speakers’ bureau or has made paid presentations on behalf of DePuy and Tornier; serves as a paid consultant to or is an employee of DePuy and Tornier; has stock or stock options held in Tornier; and serves as a board member, owner, officer, or committee member of the American Shoulder and Elbow Surgeons. Neither Dr. Silvero nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this chapter.

INTRODUCTION

Neer first introduced the term cuff tear arthropathy in 1977. He published a more detailed description of the clinical findings, pathology, and distinguishing features of the condition in 1983.¹ This entity was described as a relatively rare condition that developed in less than 5% of patients with a complete rotator cuff tear in the absence of other known etiologic factors. Cuff tear arthropathy is characterized by superior migration of the humeral head; erosions of the inferior acromion and superior glenoid; and collapse of the soft, atrophic head in advanced stages. Clinically, patients have long-standing pain that is worse at night and exacerbated by activity. Many patients are unable to elevate the affected arm above 90°, and external rotation is typically weak or absent. Neer et al¹ recommended that these patients be treated with an unconstrained total shoulder arthroplasty with soft-tissue reconstruction followed by “limited goals rehabilitation,” noting that results were inferior to patients with an intact rotator cuff.

Introduction of the reverse shoulder prosthesis by Grammont in 1985 provided the first design that restored comfort and function in patients with cuff tear arthropathy. Its unique design featured a lower, more medial center of rotation that lengthened the deltoid lever arm and decreased the shear forces at the implant-glenoid interface. Although a complication rate of 15% was reported in an early midterm study, 96% of patients had no or only minimal pain, with significant improvements in Constant scores and range of motion.²

PATIENT SELECTION

PREOPERATIVE IMAGING

Plain radiographs are an essential first step in the evaluation of cuff tear arthropathy. They should include an AP, a true AP, and an axillary lateral view (Figure 1). Characteristic radiographic findings include (1) an area of collapse of the proximal aspect of the humeral articular surface, (2) a paucity of osteophytes, (3) superior migration and a reduced acromiohumeral distance, (4) rounding of the greater tuberosity (femoralization), and (5) erosion of the undersurface of the acromion (acetabularization).

Many classification systems have been proposed, but we have found the Seebauer classification (Figure 2) to be the most useful because it provides a functional and biomechanical radiographic means of assessing cuff tear arthropathy. It focuses on the position and the stability of the center of rotation. In types IA and IB, the center of rotation is not displaced; the humeral head is centered and stable. Type IA exhibits acetabularization of the coracoacromial arch and femoralization of the humeral head. Type IB shows medial erosion of the glenoid. In type IIA and type IIB, the center of rotation is significantly cranially displaced. Type IIA has limited stability provided by the coracoacromial arch, and type IIB is characterized by complete static or dynamic anterosuperior instability. Sometimes it is difficult to differentiate between type IIA and type IIB on a simple static AP radiograph. In this case, a clinical examination with elevation against resistance will show increased superior displacement in type IIB shoulders.⁴

In most patients with cuff tear arthropathy, plain radiographs make the diagnosis clear and more advanced
imaging studies are not required. However, if plain radiographs reveal glenoid erosion, then a CT scan is recommended to evaluate the glenoid bone stock. Advanced imaging studies are also helpful to evaluate the condition of the rotator cuff. The amount of preoperative rotator cuff atrophy and fatty infiltrate is important in discussions of postoperative outcomes. Simovitch et al⁵ demonstrated that patients with grade 3 or 4 fatty infiltration of the teres minor can actually lose external rotation after reverse shoulder arthroplasty, and clinical outcomes are significantly inferior to those in patients without advanced fatty infiltration.

FIGURE 1 Preoperative AP (A) and axillary lateral (B) radiographs show the typical changes seen in cuff tear arthropathy. Note the rounding of the greater tuberosity, decreased acromiohumeral distance, and thinning of the acromial arch.

FIGURE 2 The Seebauer classification of cuff tear arthropathy. CA = coracoacromial. (Adapted with permission from Visotsky JL, Basamania C, Seebauer L, Rockwood CA, Jensen KL: Cuff tear arthropathy: Pathogenesis, classification, and algorithm for treatment. J Bone Joint Surg Am 2004;86:35-40.)

PROCEDURE

Room Setup/Patient Positioning

The patient is placed in the semi-Fowler position, with the head on a headrest that allows the patient to be positioned at the edge of the table so that the arm can be freely extended (Figure 3). It is best to finalize patient positioning before securing the head to avoid inadvertent
extubation or impingement of the cervical spine and brachial plexus during table and headrest positioning. After the patient is securely positioned, a true AP view of the shoulder is obtained with C-arm imaging. The position and orientation of the image intensifier is recorded to facilitate reacquisition of this view at the time of surgery for optimal screw placement when fixating the glenoid baseplate.

FIGURE 3 Illustrations show patient in the semi-Fowler position. Proper positioning includes placing the patient at the edge of the table so that the arm can be extended over the side of the table. The head is securely supported on a head holder with the neck in neutral alignment.

Surgical Technique

The two primary approaches to the shoulder for a reverse arthroplasty⁶ are the anterior deltopectoral and the superior-lateral approach. The deltopectoral approach as described by Neer is our preferred approach. The skin incision is made in a straight line with the arm in 30° of abduction. It extends from the coracoid process distally along the deltopectoral interval for approximately 8 to 10 cm. Subcutaneous flaps are elevated to expose the fatty strip that marks the deltopectoral interval. Dissection should be medial to the cephalic vein and retracted laterally with the deltoid muscle. The clavipectoral fascia should be incised from the inferior border of the coracoacromial ligament distally to the superior border of the pectoralis tendon. A combination of sharp and blunt dissection is used to free the deep surface of the deltoid from the underlying tissue all the way from its origin to insertion. A key elevator is used to bluntly free any adhesions overlying the subscapularis muscle. At this point, the axillary nerve can be palpated and protected. We typically release the upper 1 cm of the pectoralis insertion with an electrocautery blade to help with exposure.

The anterior humeral circumflex vessels are identified along the inferior subscapularis and cauterized. Next, the subscapularis muscle and underlying capsule are elevated off the lesser tuberosity. The capsule is released along the articular margin down to the anterior inferior neck.

Following capsular release, the humeral head is gently dislocated by externally rotating and extending the humerus. If this proves difficult, then additional release of the inferior capsule may be required.

Next, the starting point for the medullary canal reamer is identified. It should be at the highest point on the humeral head, just posterior to the bicipital groove. We ream sequentially until the reamer begins to bite on the cortical bone of the canal. The appropriate size cutting assembly is placed down the intramedullary canal. We typically set retroversion at 0°. Excessive retroversion can limit internal rotation and has been recently shown to increase the risk of anterior dislocation in a mechanical model.⁷ The cutting handle is rotated to align the orientation pin with the forearm. The cutting plate is slid up or down to adjust the resection level. The normal resection level should be just below the top of the greater tuberosity. A plate is placed over the humeral resection surface to protect it during glenoid exposure. At this point, attention is turned to the glenoid exposure. A moist laparotomy sponge protects the deltoid, and a Darrach or Fukuda retractor is placed along the posterior glenoid and levered down to expose the glenoid.

A 360° release of the subscapularis is then performed. A wide AO elevator is used to release the muscle off the anterior neck of the scapula. The rotator interval is completely released to the base of the coracoid. The inferior capsule should be clearly identified, dissected from the inferior muscle tissue, and excised. A Scofield retractor can be placed inferior to the capsule to protect the axillary nerve. Once the subscapularis muscle has been mobilized, a Bankart retractor is placed over the anterior glenoid. Glenoid exposure continues with removal of any remaining labrum and the biceps stump. The long head of the triceps insertion is released; this allows precise identification of the inferior glenoid rim and removes another
potential source of impingement. Once all the soft tissue has been adequately cleared, a large key elevator can be used to remove any remaining articular cartilage from the glenoid.

FIGURE 4 A, Intraoperative photograph shows the glenoid baseplate positioner in place. Note the key elevator at the inferior aspect of the glenoid and the positioner placed just above it. B, Corresponding diagram of the glenoid baseplate positioner illustrates proper positioning at the inferior glenoid and with the central guide pin in place.

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