37 years after its introduction by Paul Grammont, much time and money has been spent in innovating different designs for reverse total shoulder arthroplasty.

Some of the many are shown here (figure with permission from Orthopaedic Network News).

These designs differ in substantial ways, some of which are listed below.

Glenoid

Offset

Eccentric

Hooded

Diameter of curvature

Inferior overhang

Inferior tilt

Version

Lateralization

Bone augmentation (BIO RSA)

Metal Augments

Screws

Number

Compression

Locking

Parallel vs diverging

Central post

Trabecular metal

Polyethylene

Type

Thickness

Eccentric

Standard/retentive

Humerus

Neck shaft angle

Inlay/onlay

Offset

Stemless, short stem, standard stem

Straight / curved stem

Ingrowth/ cement/impaction grafting/ pressfit

Retroversion

Lateralization

Distalization

However at this point, the clinical advantages of one design over the others have not been demonstrated.

The authors of a recent article Inlay versus Onlay Humeral Design for Reverse Shoulder Arthroplasty: A Systematic Review and Meta-Analysis sought to determine if there were differences in clinical outcomes and complication rates between these designs using a systematic review of 12 studies comparing clinical results of both humeral designs. A total of 1447 patients were included with a minimum follow-up of 12 months. When comparing inlay versus onlay groups, the American Shoulder and Elbow Surgeons score was slightly higher in the inlay group (mean difference 2.53 points), but this difference was not clinically significant. Postoperative motion was not clinically different.

Comment: This review with short minimum followup did not control for the many other factors that influence the clinical outcome of reverse total shoulder, such as age, sex, diagnosis, pathoanatomy, and implant position.

A recent publication (see this link) found that the best results with reverse total shoulder were in patients with osteoarthritis and an intact rotator cuff - a diagnosis that is well treated by the less expensive anatomic total shoulder arthroplasty.

Thus, better clinical research is required to determine the appropriate use of reverse total shoulder and the relative value of different prostheses. Meanwhile, new innovative designs continue to appear in the marketplace each year without clear clinical evidence of their advantages.

For now, an attractive strategy is to gain working familiarity and experience with one reverse total shoulder implant that has an established track record along with the recognized technical steps that lead to the best outcome for the patient.

You can support cutting edge shoulder research that is leading to better care for patients with shoulder problems, click on this link.