Shoulder arthroplasty dates to 1893, when the French surgeon Jules-Émile Péan implanted a platinum-and-rubber prosthesis to replace a glenohumeral joint that had been destroyed by tuberculosis. Little advances were made until 1951, when Charles Neer, whom many consider the ‘Godfather’ of modern shoulder surgery, developed a prosthesis for the treatment of proximal humeral fractures.
The success of total hip replacement encouraged Neer to develop a prosthesis for the treatment of arthritic conditions of the shoulder, but it was not until 1974 that the Neer II prosthesis was launched, and with it a new era in the management of shoulder disease had begun.
Indications for shoulder arthroplasty include severe proximal humerus fractures, primary osteoarthritis, post-traumatic arthritis, cuff tear arthropathy, inflammatory arthritis, shoulder girdle tumors, osteonecrosis, and pseudoparesis caused by severe rotator cuff deficiency.
Hemiarthroplasty, total shoulder arthroplasty (TSA), and reverse total shoulder arthroplasty (RTSA) are the three main types of shoulder reconstruction that require prosthetic components.
In hemiarthroplasty, the humeral articular surface is replaced with a stemmed humeral component coupled with a head, or with a resurfacing humeral component.
TSA involves replacement of the humeral articular surface with either a stemmed humeral component or a resurfacing humeral component as well as replacement of the glenoid articular surface with either a polyethylene glenoid component, or biologic material (eg. autograft or allograft soft tissue).
RTSA involves replacement of the humeral articular surface with a stemmed humeral component containing a polyethylene humerosocket and replacement of the glenoid with a highly polished metal ball known as a glenosphere.
Current indications for hemiarthroplasty include severe proximal humerus fracture, primary arthritis, arthritic conditions in which the glenoid bone stock is inadequate to support a glenoid prosthesis, cuff tear arthropathy, and early-stage osteonecrosis without glenoid involvement.
The effectiveness of hemiarthroplasty as a treatment for unreconstructible proximal humerus fracture is well documented, with good results in terms of pain relief, but poor results in terms of restoration of range of motion. Controversy exists regarding whether hemiarthroplasty or TSA is superior for the management of glenohumeral OA.
The most recent evidence would suggest that TSA provides significantly greater pain relief, forward elevation, gain in external rotation, and patient satisfaction compared with hemiarthroplasty. In addition, the rate of revision surgery is significantly lower with TSA than with hemiarthroplasty.
In 1983, Neer coined the term “cuff tear arthropathy” to describe severe rotator cuff tearing and end-stage arthritic disease. In the patient with cuff tear arthropathy, TSA can be complicated by glenoid loosening or, in the patient with inadequate glenoid bone stock, may be impossible to perform.
These glenoid complications can be avoided with hemiarthroplasty, which has been reported to provide reasonable results in the treatment of glenohumeral arthritis and severe rotator cuff deficiency.
These results are clearly inferior to those in patients with an intact rotator cuff; however, hemiarthroplasty offers better outcomes than do resection arthroplasty, arthrodesis, and benign neglect.
Osteonecrosis of the humeral head commonly occurs as the result of severe proximal humeral fracture. However, it also may be caused by corticosteroid use, radiation therapy, alcohol abuse, endocrine disorders, sickle cell disease, and caisson disease.
Advanced cases are characterised by collapse of the humeral articular surface and painful arthritic changes, which can lead to degeneration of the glenoid articular surface.
Hemiarthroplasty is an effective treatment when the humeral head is involved but the glenoid is preserved. When the glenoid is involved, TSA has been shown to be a better solution.
Resurfacing humeral hemiarthroplasty alone has been shown to be effective for managing a variety of arthritic conditions of the shoulder. Preservation of the humeral head allows the surgeon to maintain the native head-shaft angle, offset, inclination, and version.
This technique also may facilitate later conversion to a conventional TSA.
Resurfacing humeral hemiarthroplasty is an attractive option for the young, active, or athletic patient in whom loosening or wear of a polyethylene glenoid component is a concern.
In the patient with cuff tear arthropathy, the rotator cuff can no longer maintain the humeral head in a centered position. This leads to proximal migration of the humerus, with eventual articulation of the humerus and acromion.
Femoralization of the humeral head (ie. rounding of the tuberosities) and acetabularization (ie. concave erosive change of the undersurface) of the glenoid and acromion may lead to continued bone-on-bone contact between the greater tuberosity and the acromion, with pain developing despite implantation of a standard humeral head prosthesis.
This outcome led to the development of the CTA head, which has an extended humeral articular surface. The increased surface area for articulation results in decreased greater tuberosity impingement against the acromion. Hemiarthroplasty with an Extended-coverage Head
TSA most commonly involves implantation of a stemmed humeral component and a polyethylene glenoid component. The primary indication for TSA is a painful shoulder caused by glenohumeral OA that is not successfully managed nonsurgically, in conjunction with loss of articular cartilage, incongruent osseous surfaces, and an intact rotator cuff.
Other indications for TSA include inflammatory arthritis, advanced osteonecrosis with glenoid involvement, and posttraumatic degenerative joint disease with proximal humerus malunion.
Compared with hemiarthroplasty, TSA with glenoid resurfacing results in less pain, a better fulcrum for active motion, better strength, and better patient satisfaction.
In the individual with inflammatory arthritis, the glenoid is often eroded, and wear of the glenoid surface may result in a decrease in glenoid bone stock, which may require bone grafting to ensure adequate support of the glenoid component.
TSA provides reliable pain relief and improved function in most arthritic shoulders with an intact or reparable rotator cuff. However, results of TSA are less satisfactory in patients with cuff tear arthropathy.
In these situations, the normal kinematics are altered, and the humerus tends to migrate superiorly because the deltoid contraction is relatively unopposed. Loss of the glenohumeral fulcrum and deltoid mechanical disadvantage can lead to pseudoparesis (ie. active forward elevation <90°).
The individual with such compromised function may be unable to lift the arm away from the side, let alone over the head. Constrained fixed-fulcrum reverse ball-and-socket prostheses that were developed in the 1970s to compensate for rotator cuff deficiency were quickly abandoned because of high early mechanical failure rates.
Efforts to address these shortcomings led to the development of the modern RTSA. This construct results in decreased forces on the glenoid fixation and, consequently, increased implant survivorship. Reverse Total Shoulder Arthroplasty Treatment of complex fractures of the proximal humerus in elderly patients can be challenging.
Results of fracture fixation may be compromised by osteonecrosis, loss of fixation, and hardware problems, whereas results following hemiarthroplasty may be compromised by displacement or resorption of the tuberosities and consequent rotator cuff dysfunction.
Hemiarthroplasty provides reliable pain relief but inconsistent return of function. These inconsistent results have prompted the use of primary RTSA for acute three- and four-part fractures in the elderly. Compared with conventional hemiarthroplasty, superior mobility is obtained with RTSA.