Case volume and complications after thyroid gland surgery in Germany: an analysis of routine data from 48,387 AOK patients

Background Many studies showed that hospital and surgeon volume have a significant influence on the complication rates of thyroid surgery. The present study investigates whether this relationship applies in subtotal as well as total lobe resections. Furthermore, it is still unclear which threshold for the hospital-related case volume can be determined, above which the risk of complications lies below the current national average. Material and methods The study was based on nationwide routine data for persons insured with the Local General Sickness Fund (AOK) who had undergone thyroid surgery in 2014-2016. Permanent vocal cord palsy, bleeding and wound infection needing revision were recorded using indicators. The effect of the case volume on the indicators and the case number threshold was determined using logistic regression. Results Permanent vocal cord palsy was observed in 1.3% and bleeding or wound infections needing revision in 1.6% and 0.3% of the cases. Compared to hospitals with >450 surgeries per year, the risk of permanent vocal cord palsy in hospitals with fewer than 201, 101 and 51 surgeries was significantly increased (OR [95% CI]: 1.5 [1.1-2.1]; 1.5 [1.1-2.1]; 1.8 [1.3-2.5]). The threshold needed to achieve a risk for permanent vocal cord palsy below the national average (1.3%) was 265 thyroid surgeries per year (95% CI: 110-420). For bleeding or wound infection in need of revision, no association between volume and outcome was found. Conclusion The present study showed that the risk of postoperative permanent vocal cord palsy decreased with increasing case volume. The broad confidence interval of the threshold makes clear case volume recommendation difficult. In order that the risk for a postoperative permanent vocal cord palsy is not likely above the national average, the annual case volume should reach 110 thyroid interventions.