Comparison of femoral nerve block with posterior capsule infiltration versus anterior and posterior capsule infiltration after total knee replacement

This prospective randomized controlled trial compares the SFNB group with the LiA group. The SFNB group gets a femoral nerve block with ropivacaine 0.375% and 75 microgram clonidine, and furthermore recieves 50 cc ropivacaine 0.2% with epinephrine 1:100.000 in the posterior part of the capsule. The LIA group recieves local infiltration with 50 cc ropivacaine 0.2% in the anterior capsule and 50 cc ropivacaine 0.2% in the posterior capsule. And the third injection in the subcutis with 50 cc ropivacaine 0.2% without epinephrine to prevent tissue necrosis. Patients meeting the inclusion criteria will receive information about the study and informed consent letters at the anesthesiology outpatients department. The eligible patients receive a call a week after visiting the outpatients department to obtain permission. Informed consent documents will be signed before surgery by the patient and the investigator/anesthesiologist. Patients will be randomized just before the surgery to the SFNB or LiA group.

All patients will receive the same pain medicaticn cperatively: acetominophen 1000 mg Q?D and naproxen BID and a single dose of intravenous metamizol 1000 mg (dipyrone). Moreover all patients receive a patient controlled analgesia pump with morfine. Every morning at 10.00 am the painconsulent and/or the researcher will note how much morphine is consumed. At the post-anesthesia care unit (PACU) the patients were instructed that no pain and worst possible pain equals to 0 and 10 respectively, on the visual analog scale (VAS). This VAS score is measured at the FACU until day 3 after surgery, and is noted by the patient in their patient journal during rest, flexion exercises and during walking. Side effects like nausea, vomiting, drowsiness, pruritus, paresthesia (day 1 tc 3) and obstipation (at discharge) are registered by the patient in their patient journal as well as by the clinician in the medical file in EPIC.

A total of 90 patients will be included by interviewing them at the time of intake and asking informed consent. Fewer calculations showed that 80 patients are needed to show a difference in opioid consumption

This prospective randomized controiied trial designed to compare the quality of analgesia offered by SFNB and LiA and their effects cn morphine consumption, mobilization and pain control postoperatively. Our first hypothesis concerning opioid use is a significantly reduced opioid use in the SFNB group. Seccndiy, we hypothesize that with respect to the mobilization there is no significant difference between SFNB en LIA group

Patients in the SFNB group will get a femoral nerve block with ropivacaine 0,375% and 75 microgram clonidine, and furthermore will recieve 50cc ropivacaine 0,2% with epinephrine 1:100.000 in the posterior part of the capsule. The LiA group will receive 3 local infiltrations: 50cc ropivacaine 0,2% in the anterior capsule and 50cc ropivacaine 0,2% in the posterior capsule, and the third injection in the subcutis with 50cc ropivacaine 0,2% without epinephrine to prevent tissue necrosis. Ropivacaine is a local anestheticum which is favorable considering its low cardiovascuiar and neurologic toxicity comparing tc bupivacaine. Moreover it has less motor blokkade compared to bupivacaine.