Background and aim: Frozen shoulder is a poorly understood pathological entity that is characterised by a painful and stiff shoulder. To analyse the socioeconomic impact of frozen shoulder in terms of cost generation and prolonged absence from work, we conducted a retrospective cohort study based on shoulder injuries through accidents in Switzerland.
Methods: Data were obtained from the comprehensive database of the Statistical Service for the Swiss National Accident Insurances (SSUV). Cases with shoulder injuries (ICD-10 codes S4* and M84.3*) and/or an additional code of adhesive capsulitis (M75.0) were extracted. Outcomes were work incapacity, with long-term work incapacity defined as absence from work for >90 days and very-long-term cases with >360 days lost. Healthcare and treatment costs as well as total insurance expenses were measured over a 5-year follow-up. Multivariate statistical analyses were used to quantify the effect of the frozen shoulder complication.
Results: Among all 456,926 patients with a shoulder injury, 5% or a total of 22,228 posttraumatic frozen shoulder cases were observed over the 8-year period. Patients suffering from a frozen shoulder after shoulder injury showed significantly longer sick leave periods with 30.8% long-term and 9.7% very-long-term cases compared with 9.4% and 1.3%, respectively, in the non-frozen shoulder cohort. Overall costs per case for an injured shoulder without developing a frozen shoulder was roughly CHF 8000, whereas expenses for cases with posttraumatic and postoperative frozen shoulder were CHF 34,000 per case.
Conclusion: Developing a frozen shoulder after a shoulder injury is associated with significant longer work incapacities (3.3–7.5 times) and is responsible for costs of CHF 78 million every year. The presented numbers are for cases covered by the compulsory accident insurance only and do not include the even more frequent idiopathic frozen shoulder cases.