Exploration of causal relationship between shoulder impingement syndrome and rotator cuff injury: a bidirectional mendelian randomization

The pathogenesis of shoulder impingement syndrome (SIS) is still unclear, and its questionable causal relationship with rotator cuff (RC) injury has led to confusion in treatment. The purpose of this study was to explore the bidirectional causal relationship between SIS and RC injury.

SIS and RC injury datasets downloaded from the IEU Open GWAS project and GWAS catalog databases. Inverse variance weighted (IVW), MR Egger, Weighted median, and Weighted mode were used in this Mendelian randomization (MR) analysis. Cochran’s Q test, leave-one-out, and funnel plot method were used to evaluate heterogeneity between single nucleotide polymorphisms (SNPs). MR-Egger regression was used to test the horizontal pleiotropy of this study.

The IVW method (OR = 1.189, P = 0.0059) suggest the putative causal effect of RC injury on SIS. The results of MR Egger method (OR = 1.236, P = 0.2013), weighted median method (OR = 1.097, P = 0.2428) and weighted mode method (OR = 1.013, P = 0.930) showed no statistically significant (OR = 1.069071, P = 0.6173). Heterogeneity test and horizontal pleiotropy analysis suggested that there was no significant heterogeneity and horizontal pleiotropy in the results of this MR analysis. The reverse MR analysis showed heterogeneity, and the conclusion needs to be further explored.

The results of MR analysis support that RC injury may be causally associated with SIS.