Aims. The aim of this study was to examine the recent trend in delivery of arthroscopic subacromial decompression (ASD) in Scotland and to determine if this varies by geographical location. Methods. Scottish Morbidity Records were reviewed retrospectively between March 2014 and April 2018 to identify records for every admission to each NHS hospital. The Office of Population Censuses and Surveys (OPCS-4) surgical codes were used to identify patients undergoing primary ASD. Patients who underwent acromioclavicular joint excision (ACJE) and rotator cuff repair (RCR) were identified and grouped separately. Procedure rates were age and sex standardized against the European standard population. Results. During the study period the number of ASDs fell by 649 cases (29%) from 2,217 in the first year to 1,568 in the final year. The standardized annual procedure rate fell from 41.6 (95% confidence interval (CI) 39.9 to 43.4) to 28.9 (95% CI 27.4 to 30.3) per 100,000. The greatest reduction occurred between 2017 and 2018. The number of ACJEs rose from 41 to 188 (a 3.59-fold increase). The number of RCRs fell from 655 to 560 (-15%). In the year 2017 to 2018 there were four (28.6%) Scottish NHS board areas where the ASD rate was greater than 3 standard deviations (SDs) from the national average, and two (14.3%) NHS boards where the rate was less than 3 SDs from the national average. Conclusion. There has been a clear decline in the rate of ASD in Scotland since 2014. Over the same period there has been an increase in the rate of ACJE. The greatest decline occurred between 2017 and 2018, corresponding to the publication of epidemiological studies demonstrating a rise in ASD, and awareness of studies which questioned the benefit of ASD. This paper demonstrates the potential impact of information from epidemiological studies, referral guidelines, and well-designed large
