The impact of the COVID-19 pandemic on frozen shoulder incidence rates and severity

Abstract

Background: Although there is evidence that the COVID-19 pandemic had profound physiological and psychological effects, there is no research aimed at understanding if the pandemic has had an impact on the incidence or severity of frozen shoulder (FS). The aim of this study was to compare the incidence and severity of idiopathic FS before and during the pandemic.

Methods: A retrospective cohort study was performed to establish the incidence of FS during the pandemic, from March 2020 to January 2021 (pandemic study period), compared to the same time period 1 year earlier, before the pandemic (control group). All patients who were diagnosed with idiopathic FS were included. To assess the severity of the condition, visual analog scale (VAS) for pain score and Subjective Shoulder Value (SSV) on presentation were recorded and the patients were categorized into 5 different treatment groups (0 injections, 1 injection, 2 injections, 3 injections, or capsular release). As the pandemic and public health restrictions could have influenced the availability of appointments, the waiting time between referral and first appointment was calculated as a possible confounding factor. Statistical analysis was performed using the chi-square and Student t test for categorical and continuous variables, respectively.

Results: There were 847 new patient consultations during the pandemic study period; of these, 232 were for idiopathic FS. One year earlier, there were 898 initial consultations for a new shoulder problem; of these, 176 were for idiopathic FS. This represents a relative increase of 39.8% (P < .001) in the incidence of patients with FS. The mean SSV in the control group was 50% ± 20% vs. 45% ± 18% in the pandemic group-statistically significant (P = .013) but unlikely to be clinically significant. The VAS pain score was similar in both groups: mean 6 ± 2 and 7 ± 2, respectively (P = .06). There was no significant difference between the control and the pandemic group in the distribution of patients per treatment group (P = .94). The mean waiting time from referral to appointment was not significantly different between the control and the pandemic group: 58 ± 30 days vs. 55 ± 27 days (P = .30).

Conclusion: During the COVID-19 pandemic, there was a significant increase in the incidence of patients with FS. No significant difference in severity was observed. Further research is needed to evaluate a causal relationship between the COVID-19 pandemic and FS.

Keywords: COVID-19; Frozen shoulder; adhesive capsulitis; epidemiology; incidence; pandemic.