Do radiographic measurements of glenoid or humeral lateralization and distalization affect post-operative outcomes for reverse total shoulder arthroplasty?

Optimizing patient outcomes in reverse total shoulder arthroplasty remains a subject of ongoing research. Newly described radiographic angles allow the determination of the glenoid and humeral component contributions to lateralization and distalization, which might play a role in patient outcomes. Thus, this study aims to explore the effect of radiographically measured glenoid vs. humeral lateralization and distalization on patient-reported outcomes and reoperation. Two hundred seventeen consecutive patients who underwent reverse total shoulder arthroplasty from November 2016 to August 2022 were retrospectively reviewed. Pre-operative and final follow-up subjective shoulder value (SSV), visual analog scale for pain, American Shoulder and Elbow Surgeons score, and unplanned reoperations were recorded. Pre-operative and post-operative lateralization shoulder angle (LSA) and distalization shoulder angle were also recorded. Post-operative glenoid lateralization angle, humeral lateralization angle (HLA), modified distalization shoulder angle, glenoid distalization angle, and humeral distalization angle. Correlations between different pairings of radiographic angular measurements were calculated along with correlations between individual radiographic measurements and each patient-reported outcome measure. Greater positive change from pre-operative to post-operative LSA and smaller post-operative distalization shoulder angle were significantly correlated with improved SSV in both univariable and multivariable analysis. A larger decrease from pre-operative to post-operative LSA was associated with higher odds of reporting visual analog scale >0 on univariable analysis at follow-up. Otherwise, there were no associations between radiographic measurements and post-operative outcome scores. The strongest correlation for post-operative lateralization measurements was between LSA and HLA (r = +0.83) and for post-operative distalization measurements was between modified distalization shoulder angle and glenoid distalization angle (r = +0.72). Greater post-operative LSA and HLA values had higher odds of reoperation (post LSA odds ratio = 1.11, P = .011; post HLA odds ratio = 1.10, P = .047). Greater positive change from pre-operative to post-operative LSA was associated with improved SSV scores. Lower global distalization was associated with greater SSV scores. While global lateralization may be beneficial in moderation along with limiting global distalization, the independent effects of glenoid or humeral-sided lateralization or distalization measured radiographically may have a lesser impact on patient-reported outcomes.