The aim of the study is to compare the clinical effects of three different administration forms for an ACB: repeated intermittent boluses through a Certa catheter (CC) versus repeated boluses through a standard catheter (through the needle) (SC) versus a single bolus (SB). Our dual hypothesis is that repeated boluses through a catheter (either Certa or standard catheter) reduces opioid consumption (primary outcome), as well as reduces pain scores, enhances ambulation and muscle strength compared with a single bolus, and that the Certa catheter is superior to a standard catheter.