Reverse total shoulder arthroplasty - does the design matter?

A lot of time and money has been spent on developing and marketing different designs of reverse total shoulder implant systems. A few of the more commonly sold systems are shown below (figures from Orthopaedic Network News). From these illustrations one can see wide variability in baseplate fixation, glenosphere design, polyethylene configuration, neck shaft angle, inlay/onlay, humeral stem design, and humeral component fixation.

 

Because of the common, widespread, and increasing use of reverse total shoulder, companies are competing to demonstrate the superiority of their product.

The question is, "are there data to support the use of a given system?". A recent article 

What is the best design for reverse total shoulder arthroplasty in 2022? attempted to address this question.

This comprehensive article deserves a careful read by all shoulder arthroplasty surgeons. The authors' bottom line is "To this date, no implant design and no specific design modification have proven to be better than another in clinical in vivo studies."

With respect to the glenoid component, the authors suggest that all systems on the market provide equally

strong primary fixation. They indicate that the best glenoid system should have a solution for severe glenoid bone loss or for bony lateralization with a longer fixation system, making it possible to have a strong purchase of at least 10mm in native glenoid bone. In addition, some amount of glenoid lateralization (6–8mm) seems necessary to improve active axial rotation, to decrease scapular notching, and to improve impingement free range of motion.

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With respect to the humeral cup, a decrease in neck-shaft angle to a more anatomic 135 degrees may provide better passive range of motion without any adverse effects in terms of stability. There have been concerns recently regarding excessive tension with the use of onlay systems and a trend to more medialized inlay designs. 

With respect to humeral stems, these authors suggest that the optimal design should be a compromise between strong humeral fixation without excessively filling the humeral canal to prevent bone remodeling but sufficiently filling the canal to prevent misalignment

Again, no implant design and no specific design modification have proven to be better than another in clinical studies.

With respect to the outcomes of reverse total shoulder arthroplasty, it may be that "the surgeon is the method". It is the surgeon that applies her or his experience and skill to assess the patient and the shoulder preoperatively, carries out the procedure, and manages the recovery. These factors may be more important to the clinical outcome and longevity than the implant design.  

We should be asking, "What is the best way to spend our time and money to improve the outcomes of reverse total shoulder arthroplasty for our patients?"

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How you can support research in shoulder surgery Click on this link.

Here are some videos that are of shoulder interest

Shoulder arthritis - what you need to know (see this link)

Shoulder arthritis - x-ray appearance (see this link)

The smooth and move for irreparable cuff tears (see this link)

The total shoulder arthroplasty (see this link).

The ream and run technique is shown in this link.

The cuff tear arthropathy arthroplasty (see this link).

The reverse total shoulder arthroplasty (see this link).

Shoulder rehabilitation exercises (see this link).

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Note that author has no financial relationships with any orthopaedic companies.