Sunday, August 12, 2018

Reverse total shoulder failure from baseplate loosening

Incidence and risk factors for aseptic baseplate loosening of reverse total shoulder arthroplasty

These authors analyzed 202 shoulders that underwent primary or revision RTSA using 1 implant system and evaluated baseplate loosening at a minimum 2-year follow-up. They found that baseplate loosening occurred in 6 shoulders (3.0%). 

Four of the cases of baseplate failure occurred in the 39 revision RTSAs (10%) while only 2 occurred in the 163 primary arthroplasties (1.2%). 

Five of the cases of baseplate failure were among the 25 patients receiving structural bone graft.

Two of the cases of baseplate failure were among the 11 patients who did not have fixation with all locking screws. 

Comment: These data suggest that in this individual surgeon, individual prosthesis design series, baseplate failure was associated with inferior quality of glenoid bone (resulting from prior failure or necessitating bone graft or non-locking screws.

In the two examples from the article shown above, it is evident that the failure results from an upwards directed force applied to the laterally offset glenosphere by the humeral component. As emphasized in this article, Factors affecting fixation of the glenoid component of a reverse total shoulder prothesis, this force is best resisted by secure screw fixation and by solid contact between the upper aspect of the baseplate and the carefully prepared native glenoid bone.

The rates of complications after an arthroplasty are related to the patient, the prosthesis, and the physician performing the surgery. Here we have an analysis of 202 of 256 shoulders treated between 2008 to 2014 by an individual surgeon using an individual reverse total shoulder design. We can anticipate that the rate of complications, such as baseplate failure, in these experienced hands would be less than in the hands of less experienced surgeons. In fact a recent article Analysis of 4063 complications of shoulder arthroplasty reported to the US Food and Drug  Administration from 2012 to 2016, found that baseplate failure was the fourth most common cause of failure among 2390 revised reverse total shoulders:

The difference is that the data in the table above represent cases from occasional as well as from frequent shoulder arthroplasty surgeons.

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