A Prospective, Randomized Comparison of the Postoperative Administration of Tramadol and Morphine following Primary Total Knee Arthroplasty

Background: Different techniques and medications are used to achieve pain relief and early mobilization after total knee arthroplasty (TKA). However, the relationship between subacute postoperative pain and early functional recovery remains to be fully resolved. We examined the effects of low-dose tramadol, and morphine on subacute postoperative pain management with NSAID in patients after TKA. Hypothesis: The low-dose tramadol combined with NSAIDs are effective for subacute postoperative pain in TKA. Methods: We prospectively studied 81 patients who underwent primary TKA. Before surgery, we randomly assigned participating patients into one of three treatment groups; Group NSAID, Group Tramadol, or Group Morphine. The postoperative pain intensity was measured and recorded by physical therapists with a visual analogue scale (VAS) at rest (rVAS) and during movement (mVAS) on the day before surgery, and on postoperative days (PODs) 3, 7 and 14. The lower leg functional recovery was also evaluated by the range of motion (ROM) of the knee, and the quadriceps muscle strength (% muscle strength). Results: Twenty-two patients from each group completed the study. The mean rVAS scores of the groups showed no significant differences between throughout the postoperative period. The mean mVAS scores showed no differences on PODs 7, 10, and 14. However, the mVAS scores of Group Tramadol were significantly lower than those of Group NSAID on POD 3 (p=0.0216). No significant differences were found among the groups in ROM or % muscle strength. The incidence of constipation in Group Morphine was significantly higher than that in Group NSAID (p=0.0026). Conclusion: Tramadol 100mg/day was effective for postoperative pain management, especially in the first week after TKA. Level of Evidence: Level II, low-powered prospective randomized trial.