The authors of Comparison of Reverse and Anatomic Total Shoulder Arthroplasty in Patients With an Intact Rotator Cuff and No Previous Surgery compared the clinical and radiographic outcomes of the Equinoxe primary anatomic total shoulder arthroplasty (aTSA) and the Equinoxe primary reverse total shoulder arthroplasty (rTSA) in patients with osteoarthritis (OA), an intact rotator cuff, and no previous history of shoulder surgery at a minimum follow-up of 2 years. The procedure performed, either aTSA or rTSA, was decided by the surgeon. The authors have strived to standardize practices across 30 different surgeons.

They matched 370 aTSA patients and 370 rTSA patients from an international multi-institutional registry for age, sex, and length of follow-up .

Internal rotation was scored as the posterior segment reached: hip = 1, buttocks = 2, sacrum = 3, L4-5 = 4, L1 to L3 = 5, T8 to T12 = 6, T7 =7

Preoperatively, the rTSA patients had lower outcome metrics and less motion.

Postoperatively, aTSA and rTSA patients had similar clinical outcomes, motion, and function.

Patients having aTSA had significantly greater postoperative internal and external rotation and greater improvement in these motions than those receiving rTSA.

94% of patients having aTSA rated their shoulder arthroplasty as much better or better, compared with 93% for rTSA patients.

Adverse events in rTSA patients included three periprosthetic joint infections (all 3 revised), one dislocation, one broken baseplate screw, one humeral liner disassociation (revised), one humeral fracture (revised) and one patient with unexplained pain.

Adverse events in aTSA patients included four glenoid loosenings (3 revised), two humeral loosenings (1 revised), four rotator cuff tears (all 4 revised), three periprosthetic joint infections (all 3 revised), and four patients with unexplained pain.

Comment: This study found that in comparison to the rTSA, the aTSA provided significantly better external and internal rotation (see this link on how to achieve internal rotation), but was subject to the risk of rotator cuff tears. A few patients with each type of arthroplasty experienced infections, hardware related problems, and unexplained pain. The rate of patient satisfaction was high for both types of implants.

It will be of interest to continue to follow this series as longer term followup becomes available and to compare revision rates with other long term studies, such as Total shoulder replacement stems in osteoarthritis-short, long, or reverse? An analysis of the impact of crosslinked polyethylene that compared the long term revision rates in a large series of 28,467 different primary arthroplasties performed for osteoarthritis. Of note is that the lowest revision rates were seen with all-polyethylene glenoid components made of cross linked poly (XLPE). It is also noteworthy that that the cumulative revision rates for all arthroplasty types continued to increase with increasing time of followup, especially for the reverse total shoulders and for anatomic total shoulders performed with non-cross linked polyethylene.