Regional variations in surgeries for carpal tunnel syndrome and ulnar nerve disorders: A registry-based study in Finland

BACKGROUND AND AIMS: A large variation in surgery rates can be indicative of its overuse. In Finland, surgeries for carpal tunnel syndrome (CTS) and ulnar nerve disorder (UN) are common, but regional differences in their incidence rates remain unexplored. This study examined how the incidence rates of these surgeries vary across hospital districts in Finland to evaluate regional consistency. METHODS: We compared regional age- and sex-adjusted incidence rates per 100,000 person-years based on data from Finland's Care Register for Health Care for CTS and UN surgeries from 2010 to 2021, calculated relative to population size as reported by Statistics Finland. The study included 21 hospital districts in Finland. RESULTS: During the 4-year period from 2018 to 2021, the difference between the lowest (99.6 cases per 100,000 person-years (95% confidence interval (CI) 80.7-122)) and the highest (351 cases per 100,000 person-years (95% CI 336-367)) adjusted incidence rates for CTS surgery was 3.5-fold, with a median adjusted incidence rate of 213 cases per 100,000 person-years. Over the same period, the difference between the lowest (1.04 cases per 100,000 person-year (95% CI 0.03-5.78)) and the highest (81.9 cases per 100,000 person-years (95% CI 73.2-91.5)) adjusted incidence rates for UN surgery was up to 79-fold, with a median adjusted incidence rate of 17.8 cases per 100,000 person-years. CONCLUSIONS: Surgery for CTS shows up to a 3.5-fold variation across Finland's hospital districts. Although less common in absolute numbers, surgical treatment rates for UN vary up to 79-fold among these regions. Such significant variations are unlikely to be attributed solely to differences in population morbidity. Instead, the findings indicate that the criteria for performing these surgeries vary considerably across the Finland's hospital districts, suggesting a potential overuse in certain areas.