Collaboration between the Danish and Swedish hernia registers - a study protocol.

INTRODUCTION: The most common laparo-endoscopic groin hernia repair techniques are TEP (total extraperitoneal) and TAPP (transabdominal preperitoneal) repair. Despite geographic proximity, Swedish surgeons distinctively favour TEP, whereas Danish surgeons prefer TAPP. The aim of this study is to analyse the risk of reoperation for recurrence after TAPP, TEP and Lichtenstein repair using data from two nationwide registers. We also aim to discuss advantages of international collaboration between nationwide registers. METHODS: All groin hernia operations registered as TEP, TAPP or Lichtenstein repair in the Swedish Hernia Register and the Danish Hernia Database between January 2004 and December 2020 will be included. Cumulative hazard rate of reoperation for recurrence will be estimated using Cox-regression analyses adjusted for age and anatomy. CONCLUSION: Approximately 400,000 operations are estimated to have been registered prospectively in the inclusion period in the registers. The merging of two nationwide registers was made possible owing to close cooperation between the register steering committees and by obtaining the necessary approvals. This unique collaboration between nationwide registers will make it possible to compare the risk of reoperation for recurrence after TAPP, TEP and Lichtenstein repair on an international level. In future, similar collaboration may be established to explore other outcomes such as complication rates and chronic pain. FUNDING: This study protocol is financed by grants generated from Sahlgrenska University Hospital (ALF grant ALFGBG-733561, an agreement concerning research and education of doctors) and the Swedish Society of Medicine (SLS-784551). TRIAL REGISTRATION: not relevant.