Inclination angle does not affect clinical outcomes, complication rate after RSA
Humeral inclination angle has no effect on clinical outcomes, pain or complications after reverse total shoulder arthroplasty; however, an angle of 155° was associated with high rates of scapular notching.
In a recently published study, Alexander Otto, MD, and colleagues analyzed 121 patients (mean age of 69.7 years) who underwent reverse total shoulder arthroplasty (RTSA) with an inclination of either 135° (n = 97) or 155° (n = 24) in a modular prosthesis with a minimum 2-year follow-up.
According to the study, clinical outcome measures included American Shoulder and Elbow Surgeons (ASES), VAS, single assessment numeric evaluation (SANE), and simple shoulder test (SST) scores. Researchers also compared forward elevation (FE), abduction (ABD), external rotation (ER), scapular notching, radiolucency and complications between the two cohorts.
Otto and colleagues found no significant differences in ASES, VAS, SANE or SST scores between the cohorts; however, the 155° inclination group had “significantly higher” FE, ABD and scapular notching rates compared with the 135° group. Complications were similar between the cohorts, according to the study.
“Overall, the inclination angle does not significantly affect clinical outcomes or the complication rate after RTSA at midterm follow-up,” the researchers wrote in the study.
They concluded by noting the potential negative effects of scapular notching in patients undergoing RTSA.
“Cases with scapular notching are associated with significantly reduced mean ASES scores and ER as well as significantly higher VAS scores,” they wrote. “Determining when scapular notching after RTSA with an inclination of 155° begins to affect clinical outcome would be highly important,”
Perspective
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The authors of the study titled “Clinical and radiological outcomes in reverse total shoulder arthroplasty by inclination angle with a modular prosthesis” perform a multicenter retrospective review on a variable angle humeral implant. There has been substantial debate in humeral inclination in reverse prosthesis. Implants typically range from 135 to 155 degrees. The benefits of 135-degree stems include more external rotation and less scapular notching; however, reports of increased incidence of glenoid loosing and radiolucent lines have been reported. The benefits of 155 degrees of humeral inclination include decreased glenoid loosening and radiolucent lines but with increased scapular notching and external rotation.
This study interestingly looks at a prosthesis that can be variably set at the discretion of the surgeon in the range of 135 to 155 degrees. The angle of 135 degrees was selected roughly 80% of the time, but there appeared to be no difference on patient reported outcomes. There was a significantly significant increase in scapular notching in the patients who had a 155-degree humeral stem. The patients who received humeral stems with 155 degrees of inclination had significant improvements in forward elevation and external rotation compared to 135 degrees.
This study highlights many factors that surgeons must think about when choosing an implant that meets the needs of their patients, including the risks and benefits of 135- and 155-degree stems.
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