Monday, February 17, 2014

Uncemented metal backed glenoids - high revision rate

Effect of glenoid cementation on total shoulder arthroplasty for degenerative arthritis of the shoulder: a review of the New Zealand National Joint Registry.

The first sentence of this article is worthy of our attention, "Despite the lack of literature showing improved results compared with cemented designs, uncemented glenoid components are still commonly used in total shoulder arthroplasty".

These authors used the New Zealand National Joint Registry data to compare the outcomes of uncemented and cemented glenoids in total shoulder arthroplasty for degenerative arthritis.

They retrieved data on 1596 patients, with a mean follow-up 3.5 years (range 2-10.7 years). 1065 had a cemented glenoid and 531 an uncemented component. The median follow-up time was 3.5 years (range, 2-10.7 years).There were no significant differences in any preoperative factors between the patients receiving cemented and uncemented glenoids. The revision rate for uncemented glenoids was 4.4 times higher than for cemented glenoids (1.92 vs 0.44 revisions per 100 component-years, P < .001).

Age <55 years was an independent risk factor for revision (P < .001). 

The uncemented prosthesis used in most of these cases has now been taken off the market. All of the cementless revisions were in shoulders receiving this component.

The most common reasons for revision are shown below.

These data are very interesting, in that (1) polyethylene failure and liner dissociation was the most common reason for revision in the uncemented metal backed glenoids, (2) rotator cuff failure was a common mode of failure, and (3) a high percentage of failures were related to posterior instability. It would be of great interest to know the glenoid pathology in these cases of posterior instability. 

The glenoid component remains the weakest link in total shoulder arthroplasty.
To learn more about shoulder arthritis and what can be done about it, see the Shoulder Arthritis Book.

To learn more about the rotator cuff, see the Rotator Cuff Book

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