Most of the patients who received a 3-in-1 nerve block for analgesia after total knee replacement (TKR) complained of pain in the back of the knee. We investigated the value of an intrathecal (IT) morphine in patients receiving continuous 3-in-1 nerve block with a PCA technique for pain control after unilateral TKR.

Group 1 (n = 20) received spinal anesthesia with IT fentanyl 10 µg. Group 2 (n = 20) received spinal anesthesia with IT morphine 0.1 mg. All patients received continuous 3-in-1 nerve block performed with 20 ml of 0.25% bupivacaine with epinephrine 1:200000, followed by a continuous infusion of 0.125% bupivacaine at the rate of 2 ml/h plus PCA boluses of 1 ml with a lockout of 10 min. The intensity of pain at rest and on movement was assessed by the patients using a visual analog scale (VAS) for the first 2 postoperative days.

Patients in Group 2 reported significantly lower VAS pain scores at rest than those in Group 1 for the first 1 day (P < 0.05). Cumulative PCA bolus use of 0.125% bupivacaine in Group 2 was significantly lower than those in Group 1 for the first 2 days (P < 0.05). The incidences of pruritus in Groups 1 and 2 were 0 and 50%, respectively (P < 0.01).

We determined that the addition of IT morphine 0.1 mg to continuous femoral 3-in-1 nerve block improves postoperative analgesia after TKR.