Tuesday, September 9, 2014

Failure of a bone ingrowth total shoulder + cuff repair: revision to reverse total shoulder

A 60 year old patient had a simultaneous total shoulder and rotator cuff repair at an outside institution one year ago. A bone ingrowth prosthesis and a large humeral head were used as shown in the x-rays taken immediately after the procedure as shown below.

After surgery she presented to our service because of inability to raise her arm and pain. Her physical examination demonstrated pseudoparalysis (the inability to raise the arm away from the side in spite of a good passive range of motion). Our x-rays are shown below. The AP view shows upwards displacement of the humeral head relative to the glenoid and excessive lateralization of the tuberosity with respect to the glenoid and lateral acromion.

 The axillary view suggests loosening of the metal+polyethylene glenoid component.

At the time of our revision surgery the superior rotator cuff was deficient and the subscapularis was absent. Cultures were taken before antibiotics were administered. The loose glenoid component was removed. An attempt was made to convert to a reverse total shoulder without removing the extant bone ingrowth stem. However, the components could not be made to fit properly. 

It was, therefore, necessary to osteotomize the proximal humeral metaphysis to extract the bone ingrowth stem. With the stem removed, a reverse total shoulder could be accomplished.  Bone graft was required around the central screw to compensate for the bone lost from the prior glenoid implantation. Excellent fixation of the glenoid component was achieved.

Comment: This case illustrates a number of important considerations. First, the combination of cuff deficiency and shoulder arthritis can be difficult to manage with a cuff repair and anatomic total shoulder - the cuff repair is at risk for failure as occurred here. A large humeral head component places additional load on the repaired cuff. Second, glenoid components consisting of both metal and polyethylene may be at higher risk of failure due to the dissimilar material properties as explained here. All polyethlene glenoid components have a lower revision rate. Third, bone ingrowth components complicate revision and in our practice are not used because impaction grafting provides excellent fixation without complicating the possible need for subsequent component removal. Fourth, while it seems attractive to 'simply' convert an anatomic stem to a reverse, this is often not possible because of the need to place the stem of the reverse more distally to accommodate the position of the glenosphere.

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