Monday, October 24, 2011

Reverse Total Shoulder for Combined Shoulder Arthritis and Massive Rotator Cuff Tear and for Failed Conventional Total Shoulder Replacement - recent articles

Reverse total shoulder joint replacement is now being used in the treatment of shoulders in which stability cannot otherwise be restored: (1) rotator cuff tear arthropathy, (2) failed total shoulder arthroplasty with cuff deficiency and instability, (3) complex fractures of the shoulder in older individuals, and (4) carefully selected massive rotator tears. The reverse differs from conventional total shoulder arthroplasty in that it provides glenohumeral stability to allow function of the deltoid muscle in the absence of the normal stabilization of the joint by a functional rotator cuff. The reverse accomplishes stability though a spherical glenoid prosthesis screwed to the glenoid of the scapula along with a cup-shaped prosthesis at the upper end of the humerus. This construct creates a fixed center of rotation so that contraction of the deltoid results in elevation of the arm.

A recent article has been published by Cheung et al on the complications associated with the reverse total shoulder. The authors list nerve injury, humeral fracture, hematoma, infection, scapular notching, dislocation, prosthesis failure, and acromial fracture as the more common of these complications. The rate of these complications has approached 70% in some reports.

Nerve injury may result from difficulties during these complex surgeries; but another important cause is excessive lengthening of the arm resulting from the surgeon's attempt to achieve stability by increasing the resting tension on the deltoid. These complications may be less with prosthesis that allow tensioning in the medial-lateral as well as the proximal-distal directions.

Intraoperative fractures result from the complex pathological anatomy encountered in shoulders requiring the reverse prosthesis, especially in revision of prior joint replacement, and from poor bone quality in older individuals. These complications may be avoided by minimizing the reaming of the glenoid and humerus, by avoiding the application of torque to the humerus, and by exerting great care in removing previously placed joint replacement components.

Hematomas can result from the extensive dissection and from the 'dead space' created around the joint. Hematomas can increase the risk of infection. Care in achieving hemostasis and holding off on joint motion for several weeks after the procedure can minimize this risk.

Infections can arise after reverse total shoulder arthroplasty, especially after revision surgery. Propionibacterium acnes is recognized as a cause of infection in reverse as well as conventional shoulder arthroplasty. Infections with this organism may be difficult to recognize due to the subtle presentation and the special methods need to culture it.

Scapular notching results from the unintended contact between the medial aspect of the polyethylene of the humeral component and the lateral border of the scapula. This is particularly a concern with prosthesis designs that medialize the center of rotation of the joint as demonstrated by shoulder fellows Saltzman and Mercer. While some disregard the importance of scapular notching, we are concerned about the fact that notching is associated with polyethylene debris which may lead to osetolysis and component failure and that the unwanted contact may contribute to glenohumeral instability. Notching is best avoided by performing a reconstruction that assures the humerus can be completely adducted without contacting the scapula.

Dislocation is always a concern after reverse total shoulder, because the indication for this prosthesis in the first place is instability. Instability is best avoided by careful soft tissue management, including reconstruction of the subscapularis, avoiding unwanted scapulo-humeral contact, appropriate (but not excessive) tensioning of the soft issues, attention to component positioning, and avoiding range of motion for the first six weeks after the procedure to allow for soft tissue healing.
 Glenoid baseplate failure is a concern because of the increased and non-physiological loads placed on the fixation of the glenoid component to the scapula and because of the often poor quality of the glenoid bone. The risk of this complication can be minimized by avoiding all but minimal glenoid reaming, care in positioning of the component on the securest bone stock, secure fixation, use of supplemental bone grafting, and minimizing the loading of the joint.

Acromial fracture can result from the poor quality of the bone, from prior acromioplasty or acromial erosion and from excessive tension on the deltoid.

In conclusion, reverse total shoulder provides a method for re-establishing glenohumeral instability when other methods are insufficient. It is a technically demanding procedure with the potential for many serious complications. Nevertheless, in experienced hands it can provide a dramatic improvement in function in carefully selected cases.


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