Shoulder Hemiarthroplasty

Shoulder hemiarthroplasty is a shoulder replacement in which the damaged humeral head is replaced with a prosthetic humeral head.

Shoulder arthroplasty is a rapidly evolving area of orthopedics focused on treating specific, painful ailments of the glenohumeral articulation. Broadly, shoulder arthroplasty encompasses surgeries using hemiarthroplasty (humeral prosthesis without replacement of the glenoid), total shoulder arthroplasty (TSA; humeral prosthesis with glenoid resurfacing via prosthesis), and reverse total shoulder replacement (humeral cup prosthesis with glenosphere implantation). ^{[1, 2, 3]}

Musculoskeletal disorders account for a high percentage of US healthcare expenditures and are the largest cause of disability. ^[4] Nearly 10% of adults report experiencing shoulder pain, which makes the shoulder the second most common joint for chronic pain. ^[4]  Although much less common than lower-extremity arthroplasties, shoulder arthroplasties have grown at annual rates between 6% and 13%. ^[5] Approximately 53,000 shoulder replacement procedures are performed annually in the United States. ^[6]  Between 2000 and 2010, there was a 1.9-fold increase in the number of hemiarthroplasties performed in the United States. ^[7]  

The first shoulder arthroplasty, performed in 1893, is credited to the French surgeon Jules Emile Péan, who inserted a platinum-and-rubber implant into a patient who had glenohumeral destruction secondary to tuberculosis and refused amputation. ^[8] It is Charles Neer, however, who is credited with pioneering modern shoulder arthroplasty. Dr Neer originally designed the humeral head prosthesis for the treatment of fractures about the humeral head and later went on to describe shoulder arthroplasty in the treatment of glenohumeral arthritis. ^{[9, 10]}

Numerous shoulder prostheses have evolved since their introduction in the early 1950s, with the most current prostheses being modular systems made of cobalt-chrome alloy. Options offered by modern humeral prostheses include varying sizes of head length and diameter to match patient anatomy and facilitate soft-tissue balancing, varying stem lengths, smooth or coated stems, and cemented or cementless humeral component stems. The specific humeral components employed are dependent on the surgical indications, the patient's anatomy, and the surgical history. ^[3]

Subsequent advances by Jon JP Warner, Chief of the Shoulder Service in the Boston Shoulder Institute at the Massachusetts General Hospital (MGH), have helped further improve shoulder arthroplasty by emphasizing innovation and healthcare economics. ^{[4, 11, 12]} Dr Warner is a pioneer in virtual patient-specific planning and value-based care in shoulder surgery.

Broadly, indications for shoulder hemiarthroplasty can be divided into those for acute fractures and those for chronic shoulder disease. Here, general indications will be presented and disease-specific indications will be discussed. With each indication, special attention must be paid to the integrity of each functional unit of the patient's shoulder, along with expected patient goals and outcomes.

Goals of hemiarthroplasty include relief of pain, improvement in overhead motion, and improvement in strength with overhead activities. Unrealistic expectations require additional patient education about possible postoperative limitations and lifestyle modifications, which may represent a contraindication to any type of arthroplasty if they persist.

General indications for shoulder hemiarthroplasty include the following ^{[13, 14, 15]} :

• Pain for glenohumeral osteoarthritis that has failed conservative therapy with sparring of the glenoid articular surface
• Any form of glenohumeral arthritis with inadequate glenoid bone stock when a glenoid component would otherwise be indicated
• Patients at risk for glenoid component loosening (younger patients, patients requiring heavy usage of their shoulder)

In current practice, TSA is increasingly supplanting hemiarthroplasty for the treatment of glenohumeral osteoarthritis. The 2020 guidelines from the American Academy of Orthopaedic Surgeons (AAOS) stated that in this setting, anatomic TSA demonstrates more favorable function and pain relief in short-term to midterm follow-up as compared with hemiarthroplasty. ^[16]

Acute fracture indications for hemiarthroplasty include the following:

• Neer four-part fractures ^{[17, 18]}
• Neer three-part fractures ^{[17, 18]} when open reduction and internal fixation (ORIF) is complicated by poor bone quality
• Neer three- and four-part fractures with concomitant humeral head dislocation ^[19]

It has been suggested that reverse shoulder arthroplasty may be a better choice for proximal humeral fractures than hemiarthroplasty is. ^{[20, 21]}  However, many factors have been found to be capable of affecting treatment of proximal humerus fractures, one of which is surgeon volume. ^[22] For many elderly patients, nonoperative treatment of proximal humerus fractures may be a viable option, decreasing the risk of death and adverse events. ^[23] In addition, operative decisions have been found to be influenced by the surgeon's specialty (shoulder surgeon vs trauma surgeon). ^[24]

The following chronic shoulder diseases may be indications for hemiarthroplasty. ^[19]

Primary osteoarthritis

Patients with primary glenohumeral osteoarthritis typically complain of joint stiffness, crepitus, and pain. Hallmark radiographic findings include a loss of joint space, subchondral cysts, sclerosis, and osteophyte formation. Rotator cuff and deltoid function may be normal or abnormal and must be assessed. Patients with adequate glenoid bone stock and an intact rotator cuff usually benefit from TSA as compared with hemiarthroplasty.

In a large study comparing hemiarthroplasty to total shoulder arthroplasty, Pfahler et al ^[25] found that for 102 shoulders treated with hemiarthroplasty and 418 with TSA, both functional and subjective outcomes were better with TSA than with hemiarthroplasty.

In a prospective randomized trial involving 51 shoulders, Gartsman et al ^[26] determined that TSA resulted in significantly greater pain relief and internal rotation than hemiarthroplasty but was associated with increased cost, operating time, and blood loss.

Similarly, in a meta-analysis of 112 shoulders treated for osteoarthritis, Bryant et al ^[27] found that TSA offered better functional outcomes and decreased pain when compared with hemiarthroplasty at 2-year follow-up.

Furthermore, Eichinger et al found that in patients aged 50 years or younger, TSA offered higher satisfaction than hemiarthroplasty did. ^[28] For TSA and hemiarthroplasty, the satisfaction survival rates at 5 years were 95% and 71.6%, respectively. Additionally, TSA had a higher implant survival rate than hemiarthroplasty did (95% vs 89%).

TSA has increasingly been favored over hemiarthroplasty for treatment of glenohumeral osteoarthritis. ^[16]

Inflammatory arthropathies

The most common inflammatory arthropathy affecting the shoulder is rheumatoid arthritis. Clinical findings at the glenohumeral joint are similar to osteoarthritis. However, patients may present at a younger age and with more advanced joint destruction. Hemiarthroplasty is considered when glenoid bone stock is inadequate for total or reverse total arthroplasty.

Pfahler et al ^[25] determined that functional outcomes for TSA were superior to those for hemiarthroplasty in 49 rheumatoid shoulders treated with hemiarthroplasty and 107 treated with TSA.

Similarly, Sperling et al ^[29] determined that TSA provided significantly greater pain relief and abduction than hemiarthroplasty in the setting of an intact rotator cuff for rheumatoid patients.

Instability arthritis

Patients with primary or recurrent dislocation are at an increased risk for the development of glenohumeral osteoarthritis. Patients treated surgically for instability also demonstrate increased rates of glenohumeral osteoarthritis. Although a less common entity than primary osteoarthritis and rheumatoid arthritis, instability arthritis frequently presents before the age of 50. The choice between hemiarthroplasty and TSA is controversial in these patients.

Pfahler et al ^[25] showed that TSA has superior functional outcomes compared withhemiarthroplasty, but these results did not reach statistical significance.

Avascular necrosis of humeral head

Avascular necrosis (AVN) remains one of the major indications for hemiarthroplasty. Typically associated with alcoholism, corticosteroid use, radiation therapy, and sickle cell anemia, AVN presentation can vary widely, but patients frequently complain of pain in the setting of a functioning rotator cuff on physical examination. Plain film findings vary from normal to subtle lucency to complete osseous collapse. In deciding between hemiarthroplasty and TSA for the treatment of AVN, it appears that resurfacing of the glenoid is typically not necessary, except possibly in the setting of advanced arthritis. ^{[25, 30]}

Rotator cuff tear arthropathy

Patients with an irreparable rotator cuff tear in the presence of glenohumeral osteoarthritis present with pain and markedly decreased elevation. Plain films may show a complete loss of the subacromial space with the humeral head articulating with the undersurface of the acromion. Because hemiarthroplasty is inferior to reverse total arthroplasty for this condition in terms of functional outcome, ^[31] hemiarthroplasty is typically reserved for the case where glenoid bone stock is insufficient for glenosphere implantation. TSA is contraindicated for risk of glenoid component loosening secondary to eccentric loading.

Glenohumeral chondrolysis

Chondrolysis is rare condition sometimes seen following previous shoulder intervention and presents with pain and stiffness. Muscle strength testing is typically normal and, with the exception of loss of joint space, radiographic findings of osteoarthritis are absent. Because of the frequently younger age of presentation in many of these patients, some surgeons may opt for biologic resurfacing of the glenoid with hemiarthroplasty. ^{[19, 32]} Other indications for biologic resurfacing include primary osteoarthritis, posttraumatic osteoarthritis, or postreconstructive osteoarthritis in young, active patients. Previously used biologic surfaces include anterior capsule, fascia lata autograft, and Achilles tendon allograft. ^{[33, 34]}

Tumor

Although an exceptionally rare indication, tumors requiring resection of the humeral head may be amenable to hemiarthroplasty. When rotator cuff function is severely affected by the resection, however, reverse total arthroplasty may be preferred. ^[19]

Contraindications for hemiarthroplasty can be divided into relative and absolute contraindications. Absolute contraindications include the following:

• Active infection
• Neuropathic shoulder
• Ankylosed shoulder
• Previous glenohumeral arthrodesis
• Incongruent glenoid and humeral surfaces
• Severe loss of glenoid articular cartilage
• Fracture treatable with ORIF
• Nondisplaced fractures treatable nonoperatively
• Unmotivated patient

Relative contraindications include the following:

• Poor surgical candidate due to general medical health
• Deltoid paralysis
• Unrealistic patient expectations

Procedural planning

The glenohumeral joint is a ball-and-socket articulation between the glenoid fossa of the scapula and the humeral head. Lacking any inherent stability, it is the most mobile joint in the human body. As such, the glenohumeral joint relies on both static and dynamic stabilizers for proper function. Dynamic stabilization and proper function is largely dependent on a functional, intact rotator cuff and its interaction with the deltoid. Reconstruction of the humeral head using good anatomic approximation is critical for optimization of shoulder biomechanics, particularly with respect to rotator cuff function, deltoid function, and soft-tissue balance.

Iannotti et al defined many of the crucial anatomic measurements used to construct modular prostheses for optimal reconstruction of normal anatomy. ^[35] They found the average radius of curvature of the humeral head in the coronal plane to be 24 ± 2.1 mm (range, 19-28 mm). Average humeral head thickness was 19 ± 2.1 mm (range, 15-24 mm). Lateral humeral offset, or the distance from the base of the coracoid process to the most lateral part of the greater tuberosity, averaged 56 ± 5.7 mm (range, 43-67 mm).

Boileau and Walch used a three-dimensional digitizer to obtain detailed measurements on humeral head version, inclination, and offset. Their studies showed average retroversion to be 21.5º ± 15.1º (range, –10.3º to 56.5º). The average neck-shaft angle measured 129.6º (range, 123.2º to 135.8º). Medial and posterior offsets averaged 2.6 ± 1.8 mm (range, –0.8 to 6.1 mm) and 6.9 ± 2.0 mm (range, 2.9-10.8 mm), respectively. ^[36]

Clavert et al described a technique that employed the pectoralis major tendon insertion as a point of reference to assist in establishing the ideal height for the hemiarthroplasty prosthesis in the case of a proximal humerus fracture. ^[37] It is imperative to use radiographs of both shoulders in order to determine the length, diameter, and size of the patient’s humerus.

Complication prevention

Assessment of outcomes, including complications, should be considered an important aspect of any surgeon’s clinical practice. This allows surgeons to critically analyze their own strengths and weaknesses and, ideally, find ways to improve their performance, ultimately providing the best care and value for patients. 

Preoperative administration of antibiotics (cephalosporins, vancomycin, or clindamycin) can minimize the risk of bacterial infection.

Proper head positioning to avoid hyperextension of the neck can minimize risk of cervical root compression during surgery.

Accounting for up to 20% of intraoperative complications, fractures can frequently be prevented with refined surgical technique. Etiologies include excessive reaming of the humerus, overzealous impaction of the humeral canal, or placing excessive torque on the humerus to expose the glenoid. ^[38] Caution must be exercised, especially with osteoporotic patients and those with rheumatoid arthritis. ^[39]

Iatrogenic neurologic injury can be prevented by the surgeon's familiarity with the normal shoulder anatomy, meticulous surgical technique, and an acute awareness of potential anatomic variants. The majority of neurologic injuries represent neurapraxias that resolve spontaneously over time. ^[38]