Monday, June 1, 2015

Shoulder joint replacement - considerations

Under optimal circumstances, glenohumeral arthroplasty can be a powerful tool for reconstruction of an arthritic shoulder. In considering the advisability of a shoulder arthroplasty and the selection of a specific procedure, it is important to consider the “4Ps”.

(1) Is the problem (diagnosis and associated aspects of the shoulder) one that can be well managed with arthroplasty? Are the essential bone, deltoid, cuff, nerve, and skin tissues in sufficient condition for a safe and effective arthroplasty? Is the problem of a severity typical of patients presenting for shoulder arthroplasty. The chart below shows the distribution of SST scores among patients coming for elective shoulder arthroplasty.

(2) Is the patient informed and in sufficiently good physical, social and emotional health to succeed with the procedure and its post-surgical rehabilitation? Comorbidities, level of education, type of insurance, age, sex, and the patient’s overall well-being have all been shown to influence the outcome of the arthroplasty.

(3) Is the physician sufficiently experienced shoulder reconstruction to optimize the chance of a good outcome? Many shoulder arthroplasties are performed by surgeons doing a small number of these cases each year, yet surgeon case volume has a strong influence on the outcome of the surgery. As we say, ‘the surgeon is the method’ and ‘experience is the great teacher’. 328

(4) Is the procedure appropriate for the problem, patient and physician? Among the variations of shoulder arthroplasty available, which is the best fit for the shoulder, the patient and the surgeon?

There are four basic types of shoulder arthroplasty: the humeral hemiarthroplasty, the ream and run (humeral hemiarthroplasty with a non-prosthetic glenoid arthroplasty), the total shoulder (humeral hemiarthroplasty with a prosthetic glenoid arthroplasty) and the reverse total shoulder.

Prosthetic humeral hemiarthroplasty is considered (a) when the glenoid articular surface is intact (as in avascular necrosis before collapse of the humeral head and before secondary destruction of the glenoid surface), (b) when there is insufficient joint volume or glenoid bone stock to allow for secure placement of a glenoid component, (c ) in cases of rotator cuff tear arthropathy when the humeral head is stabilized by an intact coracoacromial arch and active elevation exceeds 90 degrees, and (d) in cases where there is concern about infection that discourages the use of a glenoid component. In glenohumeral arthritis – i.e. when both the humeral and glenoid articular surfaces are involved – a hemiarthroplasty alone may be insufficient treatment. There are two types of humeral hemiarthroplasty implants: a humeral head prosthesis fixed with a stem inserted down the medullary canal of the humerus and partial or complete resurfacing prosthesis that is mounted on the retained biological humeral head.

The ream and run (humeral hemiarthroplasty with a non-prosthetic glenoid arthroplasty) is considered for the treatment of glenohumeral arthritis when the informed patient wishes to avoid the potential risks and activity restrictions associated with a prosthetic glenoid component. Initially there was interest in ‘biological’ resurfacing of the glenoid with capsule or cadaveric meniscus as a way to avoid the risks of prosthetic glenoid component failure; recent experience with this approach has not been encouraging, however. The ream and run procedure is a glenohumeral arthroplasty in which a humeral hemiarthroplasty is combined with conservative reaming of the glenoid to a single concentric concavity without substantially modifying glenoid version and without the use of biological interposition. Because the ream and run modifies both the humeral and glenoid articular surfaces, it is a glenohumeral arthroplasty – it is not to be confused with a hemiarthroplasty in which only the humeral side of the joint is addressed. We refer to it as a “radically conservative” procedure because it involves the removal of less glenoid bone than that required for the insertion of a glenoid component.

In the anatomic total shoulder arthroplasty, a humeral hemiarthroplasty is combined with a prosthetic glenoid component. The total shoulder is the most commonly used approach to glenohumeral arthritis when the rotator cuff is intact and when sufficient glenoid bone is available for fixation of the glenoid prosthesis.

In the reverse total shoulder, the positions of the ball and socket are reversed from the anatomical arrangement. This type of prosthesis is used when the arthritic shoulder demonstrates instability that cannot be managed with an anatomic prosthesis or when the shoulder is ‘pseudoparalytic’, meaning that the shoulder cannot be actively elevated to 90 degrees in spite of a good range of passive motion and intact deltoid function. Reverse total shoulder arthroplasty is used to manage rotator cuff tear arthropathy and anterosuperior escape after a failed attempt at rotator cuff repair. The reverse arthroplasty is also used to manage comminuted proximal humeral fractures in the osteopenic bone of older individuals, massive cuff tears without arthritis and failed anatomic arthroplasty with instability or pseudoparalysis.

Be sure to click on this link to the Shoulder Arthritis Book.
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