Analgesia after total knee arthroplasty: is continuous sciatic blockade needed in addition to continuous femoral blockade?

Continuous femoral "3-in-1" nerve blocks are commonly used for analgesia after total knee arthroplasty (TKA). There are conflicting data as to whether additional sciatic blockade is needed. Our routine use of both continuous femoral (CFI) and sciatic (CSI) peripheral nerve blocks was changed because of concerns that sciatic blockade, and its motor consequences in particular, might obscure diagnosis of perioperative sciatic nerve injury. The revised protocol includes placing single-shot blocks and perineural catheters at both sites, but infusing local anesthetic postoperatively only in the CFI. CSI is reserved for patients having poorly controlled posterior knee or calf pain. A sample group of 12 patients treated with this protocol was followed. Ten of 12 patients required use of the CSI. Within 1 h of a 5-10 mL CSI bolus of 0.2% ropivacaine and beginning an infusion of the same drug at 5 mL/h, patients' median pain by verbal analog scale decreased from 7.5 to 2.0 (mean scores from 7.3 to 2.4). It was possible to maintain this level of analgesia until the third postoperative day when catheters were discontinued. Our experience suggests that, in most patients, adequate analgesia after TKA cannot be achieved with CFI alone and that the addition of CSI renders a significant improvement in analgesia.