Introduction:  Post-operative pain management following total knee replacement (TKA) is crucial. The introduction of some available, inexpensive, and effective methods for post-operative pain management is necessary. Therefore, this randomized clinical trial was done comparing the analgesic effect of an oral low-cost drug (oxycodone) and ultrasound-guided nerve block (saphenous nerve block) to assess the best method for post-operative pain management after TKA surgery.
Methods: This single-blind, randomized, controlled, single-center clinical trial was performed from June 2017 to June 2018. There were 80 patients undergoing TKA randomly divided into two groups; group A received a single shot ultrasound-guided saphenous nerve block and, group B took oxycodone which started before and continued every 6 hours after surgery to control post-operative pain. The pain score by visual analog scale (VAS), nausea- vomiting, and diclofenac use were assessed postoperatively at 2, 6, 12, and 24 hours’ post-spinal anesthesia administration. Data were analyzed by SPSS-21, Chi2, Fishers' exact test, and Mann-Whitney test were used for comparing data between the two groups.
Result: The pain intensity according to the visual analog scale at 2, 6, 12, and 24 h post-operative was 1.25±1.37, 4.12±1.11, 5.25±0.89, and 4.57±095 in group A, and 1.10±0.953.77±0.99, 4.05±0.78, and 2.95±0.78 in the group B, respectively; this was significantly lower in group B at 12 and 24 hours (P<0.05). The mean diclofenac use was 87.01±68.02 mg in group B and 262.04±92.05 mg in the group A (P<0.001). Also, the incidence of nausea and vomiting was significantly higher in group B compared to group B (P<0.001).
Conclusion: Oral oxycodone can control post-operative pain better than saphenous nerve block in the management of post-operative pain and reducing total additional analgesic drug consumption. Although, adverse effects such as nausea and vomiting were lower in saphenous nerve block.