Adhesive capsulitis secondary to COVID-19 vaccination: a retrospective study from southern Italy

Purpose: To evaluate the prevalence of adhesive capsulitis changes in MRI examinations after COVID-19 vaccine administration. Materials and methods: We performed a retrospective cohort study of 940 participants who underwent shoulder MRIs between 2018 and 2022 in a single institution. Two groups were identified: group 1, consisting of 470 reports (261 males, 209 females, mean age 55 years old) during the pre-vaccination period from 2018 to 2020, and group 2, including 470 reports (267 males, 203 females, mean age 53 years old) during the vaccination period from 2021 to the end of 2022. MRI images were reviewed by a single radiologist with 17 years’ experience in musculoskeletal radiology and evaluated for the presence of capsulitis. Results: Based on the reports from group 1 (2018–2020), the prevalence of positive reports of AC was 16.2% CI95% (13.0-19.9). There was a total of 76 cases, with 33 women and 43 men affected. Group 2 (2021–2022) observed that adhesive capsulitis had a prevalence rate of 23.4% CI95% (19.7–27.55); among the 110 reported cases, 50 were women and 60 were men. Analyzing the sample by focusing on the difference in prevalence by gender, group 1 has a prevalence of 56.6% (43/76) CI95% (44.7-67.6) of men and 43.42% (33/76) CI95% (32.3-55.3) of women, while group 2 has a prevalence of 54.6% (60/110) CI95% (44.8-64) in men and 45.5% (50/110) CI95% (36.0-55.2) in women. Considering the total number of capsulitis cases, a statistically significant difference is highlighted between the pre-vaccination and post-vaccination periods (Fisher’s exact test p=0.007).