The effect of continuous femoral nerve block for postoperative TKR analgesia

Objective To investigate the effect of continuous femoral nerve block on pain relief after total knee replacement and the efficacy of obturator nerve blockade. Methods Sixty patients who underwent total knee replacement were studied. Postoperatively, 0.2% ropivacaine 5 ml/h was given to all patients through femoral nerve catheter, in addition,5 ml(lock time 30 min) as was given as patient controlled bolus. 24 h after operation, the VAS score, location of pain, ratio of blockade of femoral nerve, obturator nerve and lateral femoral cutaneous nerve were noted. The patients were assigned into group A(both femoral and obturator nerve were blocked) and group B(femoral nerve was blocked but not obturator nerve). The analgesia effect of the two groups was compared. Results 24 h after operation, the VAS[M(Q25~Q75)] during the rest and movement was 1(0~3) and 5(3~6) respectively. The ratio of patients complained of pain at the back of knee was 53%. The ratio of patients with the main three nerve blocked was 42%. The analgesia effect of group A was better than that of group B. Conclusion Continuous infusion of 0.2% ropivacaine through femoral nerve can not block femoral nerve,obturator nerve and lateral femoral cutaneous branch completely at the same time. The main site of pain is located at the back of knee. Obturator blockade can improve the analgesia effect after total knee replacement.