Shoulder Arthroplasty

Andrew Green, MD

Daniel DeBottis, MD

David Pezzullo, MS, PT, SCS, ATC

Dr. Green or an immediate family member has received royalties from Tornier and Wright Medical Technology; is a member of a speakers’ bureau or has made paid presentations on behalf of DJ Orthopaedics; serves as a paid consultant to Tornier and Wright Medical Technology; has stock or stock options held in IlluminOss Medical and Pfizer; has received research or institutional support from DJ Orthopaedics and Tornier; has received nonincome support (such as equipment or services), commercially derived honoraria, or other non-research–related funding (such as paid travel) from Arthrex, Journal of Bone and Joint Surgery–American, and Smith & Nephew; and serves as a board member, owner, officer, or committee member of the American Academy of Orthopaedic Surgeons, the American Shoulder and Elbow Surgeons, the Journal of Bone and Joint Surgery–American, and Techniques in Shoulder and Elbow Surgery.

Introduction

The modern era of shoulder arthroplasty was championed by Dr. Charles Neer, who pioneered the use of an anatomically conceived implant for treatment of proximal humerus fractures and later developed a polyethylene glenoid component to perform total shoulder arthroplasty to treat glenohumeral arthritis. After only a slight increase in the incidence of shoulder arthroplasty between 1990 and 2000, there has been a subsequent rapid increase in the number of shoulder arthroplasties performed in the United States. The introduction of reverse shoulder arthroplasty to the United States in 2004 was accompanied by an even greater increase in shoulder arthroplasty, with a projection of greater than 80,000 procedures by 2015.

The evolution of anatomic shoulder prosthesis design led to humeral implants that have modular humeral heads with various sizes and offsets to facilitate accurate anatomic reconstruction of the articular segment. In addition, variable neck-shaft angles further provide the surgeon the ability to closely recreate the anatomy of the patient. More recently, humeral head resurfacing and stemless humeral implants have been introduced. The importance of recreating the native anatomy has been demonstrated by multiple studies (Figure 9.1).

The modern reverse shoulder arthroplasty was initially developed by Grammont in France to treat rotator cuff–deficient shoulders. The major design features that allow this are the inverted constrained ball-and-socket orientation with a scapula-based glenosphere and a humeral-based socket that provide a stable fulcrum. The relative lengthening and tensioning of the deltoid muscle provide dynamic stability, as well as the strength and power for shoulder function (Figure 9.2).

Beyond specific design characteristics and surgical technique, numerous authors have emphasized the importance of postoperative rehabilitation in achieving successful outcomes. Although rehabilitation is considered a critically important factor in the outcome of shoulder arthroplasty, there has been little reported investigation of specific rehabilitation protocols. Most references to postoperative rehabilitation are sections on the postoperative management included in reports on the technique and outcome of shoulder arthroplasty. Nevertheless, there are principles of implant design and surgical technique that must be considered in order to ensure a successful outcome.

Surgical Indications and Contraindications

The primary indications for prosthetic shoulder arthroplasty are shoulder pain and dysfunction in the presence of advanced glenohumeral arthritis that cannot be managed with appropriate nonoperative treatments and modalities. Anatomic total shoulder arthroplasty requires an intact and functioning rotator cuff as well as sufficient glenoid bone for implant fixation, and is most commonly performed for primary glenohumeral osteoarthritis. A number of other less common conditions—including inflammatory arthropathy, posttraumatic arthritis, osteonecrosis, and capsulorraphy arthropathy—can also be treated with anatomic arthroplasty. Humeral head replacement with or without biologic glenoid preparation (soft-tissue resurfacing and “ream and run”) is indicated for some younger patients and patients who desire a very active and physical lifestyle.

In contrast, reverse total shoulder replacement was specifically developed for the treatment of shoulders with rotator cuff
deficiency. In a rotator cuff–deficient shoulder, deltoid contraction causes the proximal humerus to migrate superiorly and the glenohumeral joint does not provide a stable fulcrum for the deltoid. Mechanical advantage is thus lost, which can lead to the inability to elevate the arm above 90°, often referred to as pseudoparalysis. The results of anatomic total shoulder surgery in patients with combined glenohumeral arthritis and rotator cuff deficiency are usually poor. The indications for reverse total shoulder arthroplasty are expanding and generally apply to patients with rotator cuff deficiency, including patients with rotator cuff tear arthropathy, irreparable rotator cuff tears, posttraumatic arthropathy, and failed primary arthroplasty. More recently, reverse shoulder arthroplasty has been used in cases of primary glenohumeral osteoarthritis with glenoid deficiency or soft-tissue severe contracture.

Figure 9.1 A, True anterior posterior plain radiograph of a normal proximal humerus. B, Anterior posterior plain radiograph of a shoulder with advanced osteoarthritis. C, True anterior posterior plain radiograph of an anatomic total shoulder arthroplasty. The humeral head implant conforms to the anatomy of the native proximal humerus.

Contraindications to anatomic and reverse shoulder arthroplasty include infection, deltoid paralysis, deficient deltoid musculature, unreconstructable bone loss, as well as patient comorbidities and noncompliance.

Surgical Procedure

The preoperative evaluation includes assessment of active range of motion (AROM) and passive range of motion (PROM) as well as shoulder strength. The postoperative range of motion (ROM)
achieved after shoulder arthroplasty is related to the preoperative motion, as patients with more severe contracture may not regain as much motion. Shoulder strength is related to the integrity and function of the rotator cuff and deltoid muscles. External rotation (ER) and internal rotation (IR) weakness due to rotator cuff tearing or dysfunction is not restored with anatomic shoulder arthroplasty. Consequently, patients with substantial rotator cuff weakness and dysfunction are preferentially treated with reverse shoulder arthroplasty.

Figure 9.2 A, Preoperative true anterior posterior plain radiograph of a patient with rotator cuff tear arthropathy demonstrating elevation of the humeral head, narrowing of the acromial humeral space, and glenohumeral arthritis. B, Postoperative anterior posterior plain radiograph after reverse shoulder arthroplasty demonstrating inferior/distal positioning of the humerus with lengthening of the deltoid muscle.

Shoulder arthroplasty surgery can be performed with interscalene nerve block, with or without general anesthesia. Nerve block provides the advantage of better perioperative pain, control with reduced narcotic and general anesthetic requirement.

Anatomic Shoulder Arthroplasty

Anatomic shoulder arthroplasty is performed through a deltopectoral approach, which is an extensile approach that takes advantage of the internervous plane between the deltoid (axillary nerve) and pectoralis major (lateral and medial pectoral nerves) muscles (Figure 9.3). The skin incision is made on the anterior shoulder over the deltopectoral interval. Shorter incisions can be used in smaller and thinner patients. The subcutaneous tissue overlying the deltopectoral interval is incised and the cephalic vein is identified between the deltoid laterally and pectoralis major medially. The cephalic vein is retracted either medially or laterally. Lateral retraction preserves the often numerous branches from the deltoid muscle.

After developing the deltopectoral interval, the clavipectoral fascia is incised, exposing the underlying subscapularis muscle and tendon, lesser tuberosity, biceps tendon and groove, and the anterior circumflex humeral artery and its venae comitantes (see Figure 9.3). These vessels can be suture ligated or coagulated. The pectoralis major insertion on the humerus is identified and the superior 1 cm can be released to allow better exposure. The axillary nerve is palpated under the conjoined tendon by sweeping a finger from superior to inferior along the anterior aspect of the subscapularis muscle. Identification of the axillary nerve is essential in order to protect it from injury. The subacromial and subdeltoid planes are freed of any scarring to improve deeper exposure and postoperative shoulder motion. The long head of the biceps tendon is identified within the bicipital groove, routinely tenodesed to the pectoralis major insertion, and released proximally.

The glenohumeral joint can be entered via subscapularis tenotomy, subscapularis peel, or lesser tuberosity osteotomy. Subscapularis management in shoulder arthroplasty is an extremely important and somewhat controversial issue. Regardless of the technique, a strong anatomic repair is required to avoid subscapularis failure. The subscapularis originates on the anterior aspect of the scapula, is innervated by the upper and lower subscapular nerves, and is the largest of the rotator cuff muscles. The major function of this muscle is to internally rotate the shoulder and counterbalance the posterior aspect of the rotator cuff. At the least, subscapularis failure can result in internal rotation weakness. At the worst, it can result in glenohumeral instability and pseudoparalysis.

Subscapularis tenotomy is performed by vertically incising the tendon, leaving a cuff of tendon laterally to allow for secure repair (Figure 9.4, A). The technique relies on tendon-to-tendon healing. The subscapularis peel involves elevating the subscapularis insertion and underlying capsuloligamentous structures off of the lesser tuberosity and proximal humerus metaphysis, and relies on tendon-to-bone
healing (Figure 9.4, B and C). Lesser tuberosity osteotomy was developed in response to the observation that some patients have IR weakness after subscapularis tenotomy. The thought is that bone-to-bone healing is more predictable than tendon-to-tendon healing, and that lesser tuberosity osteotomy reduces the rate of subscapularis failure. The osteotomy is performed using either an osteotome or oscillating saw. A wafer of bone from the lesser tuberosity is elevated in continuity with the subscapularis tendon and muscle (Figure 9.4, D and E). Recent studies comparing lesser tuberosity osteotomy to the subscapularis peel technique demonstrate equivalent outcomes both with regard to healing and functional outcome. Regardless of the subscapularis technique, a complete release of the capsular contracture is carried out to mobilize the tendon and muscle, and restore soft-tissue balance.

Figure 9.3 A, Illustration of the deltopectoral interval (white arrow = deltoid muscle; black arrow = pectoralis major muscle). B, Intraoperative photograph of the deltopectoral exposure. (A reproduced with permission from Browner BD, Jupiter JB, Levine AM, Trafton PG, Krettek C, eds: Skeletal Trauma: Basic Science, Management, and Reconstruction, ed. 4. Philadelphia, PA, Elsevier, 2009.)

The humeral head is dislocated to expose the articular segment of the humerus as well as the posterior insertion of the rotator cuff. After humeral osteophytes are removed, the humeral head articular segment is removed by cutting along the anatomic neck with a saw, and the medullary canal is prepared (Figure 9.5). The anatomic neck cut determines the retroversion of the humeral component. In anatomic arthroplasty, the patient’s natural version is usually followed.

Soft-tissue releases are performed to adequately mobilize the subscapularis, as well as to release the anterior, inferior, and posterior capsular contractures and facilitate exposure of the glenoid as well as to restore glenohumeral motion. The glenoid is prepared with concentric reaming in order to optimize the seating of the glenoid component (Figure 9.6). Once the glenoid implant is placed, attention is returned to the humerus.

The humeral head component is then sized, and a trial reduction is done in order to assess glenohumeral stability, ROM, and soft-tissue balance (Figure 9.7). Different implant systems have different humeral head size options. In general, there are two philosophies in approaching this surgery; anatomic humeral head replacement and soft-tissue balancing replacement. The goal of both is to restore the center of rotation of the humerus to an anatomic position as well as to restore appropriate soft-tissue balance to achieve ROM, stability, and strength. The final humeral component is implanted with or without cement depending on the specific implant design and surgeon preference, and the glenohumeral joint is reduced.

Regardless of the technique used for subscapularis management, the repair must be strong in order to allow early shoulder motion. Subscapularis tenotomy is repaired by suturing the subscapularis tendon to the cuff of tissue remaining on the lesser tuberosity with heavy, nonabsorbable sutures. In addition, the repair can be reinforced by incorporating transosseous sutures. Subscapularis tendon peel is repaired anatomically to the lesser tuberosity using transosseous, heavy, nonabsorbable sutures. The suture limb passing through the medullary canal is passed through the tendon in Mason-Allen locking fashion and tied to the limb exiting the lateral bone tunnel. Several techniques for repair of the lesser tuberosity osteotomy are described. The authors prefer a transosseous repair with heavy nonabsorbable sutures that are passed into
the intramedullary canal and around the humeral implant. The bone is then reduced anatomically, and the sutures are tied over top, allowing for bone-to-bone contact.

Figure 9.4 Illustrations of surgical management of the subscapularis tendon and muscle. A, Subscapularis tenotomy with tendon-to-tendon suture repair. B, C, Axial view of subscapularis peel with tendon-to-bone transosseous suture repair (solid arrows indicate subscapularis peel and repair). D, E, Lesser tuberosity osteotomy with bone-to-bone suture repair. (A reproduced with permission from Gartsman GM, Edwards TB, eds: Shoulder Arthroplasty. Philadelphia, PA, Elsevier, 2008; D, E reproduced with permission from DeFranco MJ, Higgins LD, Warner JJP: Subscapularis management in open shoulder surgery. J Am Acad Orthop Surg 2010;18(12):707–717.)

Once the subscapularis is securely repaired, ROM and stability are assessed. In most cases, near full shoulder motion is possible. Glenohumeral translation should permit the humeral head to easily move to the posterior glenoid rim. If there is a question about stability, this should be addressed surgically. Shoulders with posterior instability can be treated with posterior capsular plication. ROM and the effect on the subscapularis repair and shoulder stability are noted to guide the early rehabilitation. Communication with the physical therapist regarding the integrity of the subscapularis will assist in the education of the patient and progression of the rehabilitation. The remainder of the wound is then closed, and the arm is placed in a sling.

Reverse Shoulder Arthroplasty

Reverse total shoulder arthroplasty is performed through either a standard deltopectoral or a superior deltoid splitting
approach. The deltopectoral approach is the same as it is for an anatomic shoulder arthroplasty. Management of the subscapularis is somewhat controversial. Although absence of the subscapularis has been associated with instability, there is no strong evidence to support this concern. The reality of the situation is that, in many cases, the subscapularis is either deficient or very degenerative and not likely to be functional even if it is repaired. Additionally, if repairing the subscapularis would limit ER, then it can be left unrepaired. The inherent stability of the constrained reverse ball and socket likely obviates the need for intact anterior soft tissues. The decision to repair the subscapularis should consider these factors.

Figure 9.5 Intraoperative photograph of exposure of a left shoulder with saw blade used to perform anatomic neck osteotomy to remove the arthritic articular segment.

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