Lateralized reverse shoulder arthroplasty (RSA) has emerged as an attempt to improve on some of the drawbacks of conventional RSA, such as glenoid notching and decrease in ROM. Although this new design is being used in clinical practice, the evidence is mostly limited to case series and has not been systematically reviewed.
(1) How much did patient-reported outcome measures (PROMs) and ROM improve among patients who receive a lateralized RSA implant? (2) What proportion of shoulders experience complications, revision surgery, or scapular notching?
The PubMed and EMBASE databases were searched from database inception to January 31, 2020. We included clinical studies that reported the PROMs and/or ROM of patients with insufficient rotator cuffs undergoing RSA with a lateralized implant. All other types of studies and those including patients with fractures, instability or escape, infection, rheumatologic disease, neurologic disease, or revision surgeries as an indication for RSA were excluded. PROMs and ROM were collected and are reported as mean values and ranges. Complications, revision surgery, and scapular notching are presented as proportions. The percentage of the mean change relative to the minimum clinically important difference (MCID) was calculated using the anchor-based value for each outcome. The Methodological Index for Non-randomized Studies (MINORS) was used to assess study quality. The initial search yielded 678 studies; 61 full-text articles were analyzed according to our eligibility criteria. After a detailed analysis, we included nine studies that evaluated 1670 patients (68% of whom  were women) with a mean age of 71.8 ± 0.6 years. The mean follow-up period was 41.1 ± 5.6 months. The mean MINORS score was 12 ± 4.
Active ROM improved for forward flexion (mean change 47° to 82°; MCID 12°), abduction (mean change 43° to 80°; MCID 7°), external rotation (mean change 8° to 39°; MCID 3°), and internal rotation (mean change -2 to 1 points). PROM scores also improved, including the American Shoulder and Elbow Surgeons score (mean change 20 to 50; MCID 20.9 points), Constant score (mean change 28 to 40; MCID 5.7 points), Simple Shoulder Test score (mean change 3 to 7; MCID 2.4 points), and VAS score (mean change -1.8 to -4.9; MCID -1.6 points). The proportion of shoulders with complications ranged from 0% (0 of 44) to 21% (30 of 140), and the proportion of shoulders with scapular notching ranged from 0% (0 of 76) to 29% (41 of 140). The proportion of patients undergoing revision ranged from 0% (0 of 44) to 13% (10 of 76) at short-term follow-up.
Lateralized RSA is a reasonable alternative to medialized implants for patients with rotator cuff insufficiency because it might reduce the likelihood of scapular notching without apparently compromising PROMs or ROM. More studies are required to determine whether there is a direct correlation between the amount of lateralization and PROMs or ROM.