STUDY DESIGN Double blind randomise control trial. Study design is non-inferiority trial testing 0.2% ropivacaine vs 0.4% ropivacaine. Expected 1 year to complete recruitment of 54 patients. All patients are expected to participate in the study for a period of 24h and will be followup during their convalescence in the hospital. There will be no change in scheduling of operation or additional visits for the purpose of the study.