Postoperative pain control after TKA early walking and rehabilitation, which are important to a quick recovery and early hospital discharge [2,7,8]. Therefore, postoperative pain management is considered an important prognosis factor. Methods to manage postoperative pain of TKA are IVPCA and regional anesthesia. Continuous PCB, continuous epidural nerve block, and continuous femoral nerve block are examples of regional anesthesia. Continuous PCB wets the psoas compartment with local anesthetics and blocks the nerve which passes through it. The psoas compartment is the area between the psoas muscle and the quadratus lumborum muscle. This area is innervated by the rami of the lumbar plexus and sacral plexus, and it consists of the genitofemoral nerve (L1-2), lateral femoral cutaneous nerve (L2-3), femoral nerve (L2-4), obturator nerve (L2-4), and partially the sciatic nerve (L4-S3) [9]. Therefore, blocking this area with a PCB is known to have better effects than not only IVPCA but also a continuous femoral nerve block, which usually blocks the obturator nerve that originates from the posterior branch [10-13]. Another regional anesthetic method, the continuous epidural nerve block, is a bilateral nerve block that limits the movement of the patient, so one should consider the risk of voiding difficulty and rare but serious complications such as epidural hematoma [14-16]. Therefore, this procedure cannot be easily performed on patients with a coagulation disorder or under the administration of anticoagulants to prevent deep venous thrombosis or pulmonary embolism. But the PCB only blocks the nerve unilaterally, and it can be performed even when there is a coagulation disorder. It is difficult to block of the obturator nerve with a continuous femoral nerve block. Thus, it is known that a continuous PCB is more effective in pain management than a continuous femoral nerve block, which has the disadvantage of requiring a separate block for the obturator nerve [11,17]. In a continuous PCB, the sciatic nerve cannot be easily blocked, so there may be difficulties in complete pain control of post- TKA. On the other hand, performing a post-TKA continuous PCB together with a sciatic nerve block has been reported to be as effective as a continuous epidural nerve block for pain control [18]. The presented study would have had better results if a sciatic nerve block was performed as well. However, each nerve block requires a separate catheter, resulting in further discomfort of inserting two catheters and the need to manage them. Therefore, the authors only performed a continuous PCB without performing a sciatic nerve block. Watson et al. [19] and Raimer et al. [18] reported that con- tinuous PCB also resulted in lower pain scores and fewer incidences of side effects such as nausea and sedation when compared to IVPCA. In the present study, the postoperative pain scores 6 hours after surgery between Group IVPCA and Group PCB were not very different. But afterwards, Group PCB 50 Vol. 62, No. 1, January 2012 had significantly lower pain scores than Group IVPCA. This is believed to have occurred because the psoas compartment has to be full with an adequate dose of local anesthetics to have an effect during continuous PCB. However, in the present study, the anesthetics were infused at a rate of 8 ml/hr, because of this, the effect was low until 6 hours had passed. After the area was adequately loaded with local anesthetics, the pain scores in Group PCB were lower than in Group IVPCA. Also, peripheral nerve blocks like continuous PCBs increased tissue perfusion with local anesthetics and broke the vicious cycle of pain- tetany-pain due to the effects of muscle relaxation, as argued by Morin et al. [20]. IVPCA, which uses a large quantity of opioids, can be accom- panied by nausea, sedation, and hypoventilation. However, only local anesthetics are used to block a local region, so the occurrences of systemic side-effects in intravenous patient controlled analgesia were low. In continuous PCBs, complications such as nerve damage, postoperative hemorrhage, durg infusion of the epidural, the subarachnoid space and the blood vessels can occur. Chayen et al. [21] conducted a PCB with 100 patients, and they reported 1 case of intravascular drug infusion and 1 case of epidural puncture. Although it may be safely said that PCB produces relatively low side-effects, the authors aimed at reducing such fatal complications by performing a continuous PCB with the additional use of C-arm images. After inserting the catheter, the authors confirmed that the contrast agent spread in the psoas compartment area before infusing the drugs. Since postoperative hemorrhaging, nerve damage, complications such as epidural and intravascular drug infusion did not occur in the present study, the authors found that it was better to have a continuous PCB using a C-arm than performing this procedure blindly. Group IVPCA had higher usage rates of rescue antiemetics and analgesics than Group PCB because of difficult pain management, nausea, and vomiting but the differences were not statistically significant. This is believed to be the case because the number of patients in the study was low and only the administrations of antiemetics and analgesics were recorded without considering their total doses. In conclusion, the authors found that continuous PCB was good for controlling postoperative pain in TKA patients. This procedure was able to manage pain more effectively than IVPCA, and it produced lower systemic side-effects such as neausa and sedation. Thus, this method was deemed to be a good procedure that can be safely and effectively performed. References 1. Chung MY, Kim CJ. The effect of bilateral femoral nerve block combined with intravenous patient-controlled analgesia after a bilateral total knee replacement. Korean J Pain 2008; 21: 211-6. www.ekja.org