Purpose: This study attempted to evaluate the pattern of change of the pain after total hip arthroplasty (THA) and to confirm the effect of periarticular multimodal drug injection (PMDI) on controlling the early postoperative pain.
Materials and Methods: Of the total patients who underwent primary THA at our hospital because of osteonecrosis of the femoral head from March to October 2008, 60 patients were enrolled in this study. The subjects were divided into three groups. Groups 1 & 2 received periarticular injection. Group 1 included the patients who were injected with a combination of opioid, long-acting local anesthetics, a non-steroidal anti-inflammatory drug and epinephrine. Group 2 received a combination of morphine and ropivacaine and group 3 was not injected with any analgesics. The visual analogue scale (VAS) at 4 hours, 8 hours, 12 hours, 24 hours, 2 days, 3 days, 5 days, 14 days and 1 month after surgery, the frequency that patients pushed the self-controlled pain medication machine for 2 days after surgery and the amount of clonac that was injected according to the needs of the patients were used as objective measures.
Results: The VAS score at postoperative 4 hours to 3 days among the groups showed a significant difference (P<0.05), but the VAS scores at postoperative 5 days to 1 month among the groups showed no significant difference (P>0.05). The frequency of pushing the self-controlled pain medication machine among the groups and the amount of clonac according to the needs of the patients among the groups showed that there were significant decreases at the operation day, the postoperative 1, 2 day and the 3 days (P<0.05).
Conclusion: PMDI has a significant effect on controlling the early postoperative pain after THA.

Keywords: Hip joint, Total hip arthroplasty, Pain, Periarticular drug injection