Reverse total shoulder complication - fracture of central baseplate screw

Baseplate failure is a serious complication of reverse total shoulder arthroplasty. See Reverse total shoulder, the complication of baseplate failure.

Here's an example case. An active man had multiple prior attempts at rotator cuff repair, but eventually developed cuff tear arthropathy. 

This was treated with a reverse total shoulder arthroplasty (RSA).

Of note, the baseplate is not in contact with the genoid bone superiorly (see gap at arrow)

The patient returned to physical activity including pushups. A year after the RSA, the shoulder became painful on use. X-rays showed superior tilting of the glenosphere and bending of the central screw.

Eventually the central screw fractured and the glenosphere fixation failed.

Here is an example of fatigue fracture of the central screw.

This case exemplifies the points made by the authors of 

Factors affecting fixation of the glenoid component of a reverse total shoulder prothesis, specifically that the security of baseplate fixation depends in large part on (1) supporting contact between the upper aspect of the baseplate and glenoid bone and (2) strong fixation of the inferior screw in good glenoid bone.

When such support is lacking, there is a risk of fatigue fracture of fixation screws and baseplate loosening.

Loss of superior support for the baseplate can occur when the glenosphere is inferiorly inclined. In other words, inferior inclination requires substantial glenoid reaming to achieve support for the superior baseplate.

Some related articles are referenced below.

How to avoid baseplate failure: the effect of compression and reverse shoulder arthroplasty baseplate design on implant stability

Avoiding Glenoid Baseplate Fixation Failure by Altering Surgical Technique for Varying Bone Densities

Reverse shoulder glenoid loosening: an evaluation of the initial fixation associated with six different reverse shoulder designs

Comment: We invited a very experienced RSA surgeon to give us his perspective. He kindly responded "I too have this failure mode but i think it relates to imperfect seating.  

If there is no bony contact of the baseplate inferiorly that leads to lack of ingrowth. There is a small gap inferiorly too of the baseplate. 

The lack of ingrowth is why the screws failed at the interface to the screw/baseplate junction. I have not had failures with lack of superior contact 

if there is inferior  contact."

Comments welcome at shoulderarthritis@uw.edu

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Here are some videos that are of shoulder interest
Shoulder arthritis - what you need to know (see this link).
How to x-ray the shoulder (see this link).
The ream and run procedure (see this link).
The total shoulder arthroplasty (see this link).
The cuff tear arthropathy arthroplasty (see this link).
The reverse total shoulder arthroplasty (see this link).
The smooth and move procedure for irreparable rotator cuff tears (see this link).

Shoulder rehabilitation exercises (see this link).