Reverse Shoulder Arthroplasty for Cuff Deficiency: Surgical Technique

Introduction

Rotator cuff arthropathy is a cause of shoulder pain and dysfunction consisting of rotator cuff deficiency, superior humeral head migration, and glenohumeral arthritis. History and physical examination with radiographs are the cornerstone of diagnosis, with magnetic resonance imaging (MRI) in select cases. Nonoperative treatment is first-line, including therapy for scapular and rotator cuff strengthening, activity modification, nonsteroidal antiinflammatories, and subacromial steroid injections. If nonoperative treatment fails, reverse total shoulder arthroplasty (RTSA) is a reliable surgical treatment for rotator cuff deficiency and arthropathy, offering pain relief and improved function. Complications following RTSA are not infrequent, but knowledge of RTSA technique offers a chance to help improve pain and function for patients while minimizing complications.

Procedure

RTSA is performed using a deltopectoral approach with release of the subscapularis from the lesser tuberosity and circumferential release of the glenohumeral capsule and labrum. After humeral head osteotomy, the humeral canal is reamed and broached, the glenoid is exposed, and the center is carefully identified with a central guidewire and then reamed in preparation for the baseplate. The glenoid baseplate and glenosphere are implanted, followed by implantation of the humeral stem and humeral cup, and the shoulder is reduced.

Patient History

Rotator cuff deficiency and arthropathy present with shoulder pain, weakness, and loss of function and even impaired ability to perform activities of daily living.
Women are more commonly afflicted than men, and patients are often advanced in age (70s and 80s).
The dominant shoulder is more commonly affected.
Pain is generally long-standing, worse with activity, and worse at night.
Some patients present with a history of prior known rotator cuff tear or repair, but most do not.
A subset of patients will present with loss of range of motion as a primary complaint. Inability to achieve active shoulder abduction that may be present is referred to as pseudo paralysis.
Mechanical symptoms, including crepitus or loose body sensation of the shoulder, may also be present.

Patient Examination

A careful and complete shoulder examination is indicated, including inspection, palpation, active and passive range of motion, strength testing, distal neurovascular examination, and finally provocative testing.
Inspection and palpation may reveal atrophy of the rotator cuff musculature, particularly the supraspinatus and infraspinatus muscle bellies in their respective fossae of the posterior scapula.
The most critical aspect of the examination is to confirm that the deltoid is intact and active. Deltoid deficiency or deinnervation is a contraindication to RTSA.
The humeral head may be prominent anterosuperiorly in cases of humeral head elevation.
Weakness of the rotator cuff muscles is present, typically consistent with a massive rotator cuff tear.
Supraspinatus strength may be tested using resisted elevation in Jobe position and the drop-arm test.
Infraspinatus testing involves resisted external rotation with the arm at the side and the external rotation lag sign. The external rotation lag sign involves passively externally rotating the shoulder with elbow at 90 degrees. Patients with massive infraspinatus tear will not be able to maintain the passive external rotation.
Teres minor examination consists of resisted external rotation at 90 degrees of shoulder abduction and 90 degrees of external rotation. This is typically evaluated using the Hornblower sign, in which the patient cannot maintain this abducted, externally rotated shoulder position due to teres minor dysfunction.
Subscapularis tear is suggested by internal rotation weakness with the arm in maximal internal rotation so that the pectoralis is mechanically disadvantaged. Special testing includes belly press, liftoff, bear hug, and internal rotation lag sign.
Range of motion is tested actively and passively. Patients with rotator cuff arthropathy will generally be unable to actively elevate their shoulder above 90 degrees.
Pseudo paralysis is defined as patient inability to actively abduct the shoulder due to rotator cuff arthropathy.

Imaging

Patients being evaluated for rotator cuff arthropathy are initially evaluated with a complete shoulder radiographic series including: anteroposterior, Grashey (true anteroposterior), scapular-Y lateral, and axillary lateral ( Figs. 40.1, 40.2 ).
Degenerative changes are present, including glenohumeral joint narrowing, subchondral sclerosis, cystic changes, and osteophyte formation. Superior glenoid wear is often seen in contrast to posterior glenoid wear in primary glenohumeral osteoarthritis.
The humeral head migrates superiorly or is “high-riding.” In other words, the acromiohumeral distance is decreased due to rotator cuff deficiency.
In more advanced cases, the humeral head and acromial undersurface may undergo changes in morphology in which the greater tuberosity becomes round and the acromial undersurface undergoes “acetabulization” due to abnormal contact with the humeral head. As a result, in early rotator cuff tear arthropathy, the glenohumeral articulation may be relatively spared from degeneration.
MRI is not necessary in most cases for the diagnosis of rotator cuff arthropathy, because plain radiographs provide the necessary diagnostic information.
In equivocal cases, MRI would show massive, irreparable rotator cuff tear due to retraction and fatty infiltration.

Treatment Options: Nonoperative and Operative

Initial care of patients with rotator cuff arthropathy involves a trial of nonoperative treatment.
Nonsteroidal antiinflammatories, subacromial steroid injection, activity modification, and physical therapy with scapular and rotator cuff strengthening are used.
Patients who fail to improve with nonoperative modalities are candidates for surgical intervention. Options include arthroscopic debridement, hemiarthroplasty, and RTSA.
Hemiarthroplasty may be considered for younger (<70 years), active patients who have preoperative elevation over 90 degrees and coracoacromial arch intact. This treatment yields pain relief but variable functional improvement.
RTSA is considered in older (>70 years), less active patients or in those with dysfunctional coracoacromial arch. This offers pain relief and functional improvement with potential concerns about long-term outcomes or use in younger, active patients.
RTSA biomechanically relies on medialization of the center of rotation to improve the lever arm of the deltoid muscle for abduction. This allows the deltoid to compensate for rotator cuff deficiency. In addition, the semiconstrained design helps prevent humeral superior migration and glenohumeral instability.

Surgical Anatomy

The rotator cuff muscles are the supraspinatus, infraspinatus, subscapularis, and teres minor. Their normal function is to dynamically stabilize the glenohumeral joint by pulling the convex humeral head concentrically into the concave glenoid and surrounding labrum.
Force-couples in coronal and axial planes from a well-functioning rotator cuff keep the humeral head centered on the glenoid.
The subscapularis inserts on the lesser tuberosity anteriorly, serving as an internal rotator.
The supraspinatus, infraspinatus, and teres minor insert sequentially on the greater tuberosity, serving to abduct and externally rotate the shoulder.
The long head of the biceps tendon (LHBT) is also frequently diseased or torn in patients with rotator cuff arthropathy and undergoes tenodesis at the time of RTSA. The LHBT travels in the intertubercular groove, through the rotator interval, and attaches variably at the supraglenoid tubercle and superior labrum.

Surgical Indications

Patients with rotator cuff arthropathy that has failed conservative management. This is generally advocated for elderly patients (>70 years) with lower activity level, but some have reported that RTSA has been successfully used in younger patients.
Rotator cuff arthropathy with paralysis or superior humeral migration.
Contraindications include axillary nerve or deltoid deficiency, insufficient glenoid bone stock for the baseplate, active infection, and medical comorbidities causing excessive risk for elective surgery.
Other indications for RTSA are evolving, including three- and four-part proximal humerus fracture in elderly patients and failed prior shoulder arthroplasty. RTSA is also being widely used for irreparable, massive rotator cuff tears without articular degeneration, pseudo paralysis, or proximal humeral migration. Although functional results in this setting can be impressive, these patients tend to be younger and to have higher expectations, and thus preoperative counseling and caution are critical.

Surgical Technique Setup

Positioning

We typically perform RTSA with the patient under combined general and regional anesthesia with interscalene block.
The patient is positioned in modified beach chair fashion with the back of the bed elevated about 45 degrees and knees flexed 20 degrees ( Fig. 40.3A ). A headholder is used, and the endotracheal tube is oriented toward the contralateral shoulder. The head must be in neutral alignment, and extension is to be avoided because it can lead to iatrogenic cervical foraminal stenosis and radiculopathic symptoms.
The room is set up and the bed is rotated so that there is room for an assistant to stand posterior to the shoulder and a scrub nurse to stand on the contralateral side of the patient.
The shoulder is draped with typical shoulder draping. We prefer to use a padded Mayo stand for intraoperative positioning of the arm, but pneumatic articular armholders and modified arm boards can also be used, depending on the surgeon’s preference. Regardless, the surgeon must retain the ability to manipulate the shoulder in an unhindered fashion during the procedure.
We prefer use of Ioban (3M Inc., St. Paul, MN) to seal the incision from the surrounding skin, in particular the axilla, where Propionibacterium acnes can be a concern.

Possible Pearls

Leaving the arm free for the procedure instead of use of an articulated armholder often allows improved manipulation during the case, including flexion, extension, rotation, and lateral distraction of the humerus.
A rolled towel under the medial scapula may help stabilize the scapula and glenoid during glenoid preparation and baseplate implantation.
A lateral post is applied, and the patient is situated at the ipsilateral edge of the operating table in order to prevent patient movement when distracting the humerus longitudinally and laterally during the procedure.

Possible Pitfalls

Lack of attention to room setup will make every subsequent step exponentially more difficult, and thus proper setup is critical for the procedure.
An articulated armholder can be used, but it may make manipulation of the arm cumbersome for RTSA.
Be sure to pad all bony prominences and carefully secure the head to avoid positioning-related complications such as nerve palsies.

Equipment

Basic orthopedic instruments should be available, including scalpel, Chandler retractors, Hohmann retractors, Army-Navy retractors, Gelpi self-retaining retractors, Cobb elevators, osteotomes, Metzenbaum scissors, Mayo scissors, electrocautery, suction, forceps, hemostat, needle driver, and suture scissors.
Kolbel self-retaining retractors with various blade lengths are helpful for the deltopectoral approach.
Other specialized shoulder retractors, including Fukuda ring retractor, Bankart retractors, and Darrach retractors
High-tensile-strength nonabsorbable suture. We prefer to use No. 5 FiberWire (Arthrex Inc., Naples, FL) for biceps tenodesis and subscapularis repair.
Oscillating saws
RTSA system of choice for the remainder of the equipment, such as reamers, trials, and other specialized instrumentation. The senior author’s preference is to use the Arthrex Univers Revers shoulder prosthesis (Arthrex Inc., Naples, FL).

Surgical Exposure/Portals

A standard deltopectoral approach is used for exposure ( Fig. 40.3B ).
Subscapularis takedown is performed using a peel method, and the tendon is tagged for later repair ( Fig. 40.4 ).
Subscapularis repair may improve active internal rotation and stability following RTSA.

Short Description of the Surgical Exposure

The deltopectoral groove may often be identified by rolling a pen oriented in line with the groove from lateral to medial, aiming to feel the pen fall into the groove. The coracoid process, which is almost always palpable, is also a crucial landmark for the proximal aspect of the incision. The deltopectoral incision is made with a No. 10 blade in line with the deltopectoral groove, typically starting at the medial border of the coracoid and extending distally and laterally toward the deltoid insertion. A longer incision may be needed in obese patients or for complex cases. If distal extension is needed, the deltopectoral approach can be extended to the anterolateral approach to the humerus, and thus the distal aspect of the incision should be made with this approach in mind. Dissection is then continued bluntly with Metzenbaum scissors, aiming to identify the cephalic vein in the deltopectoral groove. The proximal aspect of the deltopectoral interval can usually be identified by a preserved triangle of fat at its proximal aspect. Gelpi retractors are used for the skin and subcutaneous fat. The deltopectoral interval is identified for the entire length of the incision. The cephalic vein is typically taken laterally with the deltoid using blunt dissection because there are fewer branches medially than laterally, although it may be taken medially in cases with variant anatomy.

Once the deltoid and pectoralis muscles are separated, taking care to protect the cephalic vein, a blunt Hohmann retractor is placed over the coracoacromial ligament, and an Army-Navy retractor is used to retract the deltoid. Care must be taken during dissection and retractor placement to prevent delamination of the deltoid. This allows visualization of the conjoint tendon medially, and the clavipectoral fascia lateral to the strap muscles is divided longitudinally with electrocautery. Blunt dissection can then be used to free the plane between the strap muscles and the subscapularis, which also offers the opportunity to palpate the axillary nerve as it runs inferiorly and laterally along the anterior aspect of the subscapularis. The Kolbel/Buxton self-retaining retractor is then placed with the two blades deep to the deltoid and the conjoint tendon, respectively. Although this self-retaining retractor is useful, care should be taken during placement and use because this retractor can stretch the axillary nerve or brachial plexus if improperly placed or used. The superior aspect of the pectoralis major insertion (∼1 cm) is released to improve visualization if needed.

Next, the bicipital groove and the LHBT are identified running in the groove. This is incised, and tenodesis is performed using No. 2 FiberWire into the superior pectoralis major tendon. The bicipital groove is then opened, proceeding proximally up to the rotator interval. The anterior circumflex (“three sisters”) vessels at the inferior subscapularis are identified and suture ligated using No. 1 Vicryl (Ethicon, Somerville, NJ). These vessels mark the distal aspect of the subscapularis.

The subscapularis is then released using a peel method off the lesser tuberosity, starting at the bicipital groove and continuing medially and then inferiorly, with the arm externally rotated to put the subscapularis on stretch. A Bovie needle tip is used starting at the superolateral subscapularis insertion, peeling tendon directly off tuberosity ( Fig. 40.4A ). This is continued down to the inferior border of the subscapularis. The anterior capsule is taken with the subscapularis in a single layer. The subscapularis is tagged with two No. 2 FiberWires in figure-of-eight fashion for later repair ( Fig. 40.4B ). The anteroinferior capsule is then released from its insertion on the humeral neck to the 6 o’clock position with the use of a Fukuda retractor. Care is taken to protect the axillary nerve, which courses posteroinferiorly 1 cm from the inferior capsule. Adduction, external rotation, and flexion protect the axillary nerve. The shoulder is progressively externally rotated during the capsular release until it is dislocated. In cases with a residual remnant of supraspinatus, this can be excised at this time or left in place, depending on the preference of the surgeon.

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