Intraarticular, epidural, and intravenous analgesia after total knee arthroplasty

After total knee arthroplasty, patients regularly suffer from severe pain. It is unclear whether epidural or systemic pain therapy is superior in terms of postoperative pain relief, patients' comfort and side effects. A new therapeutic approach, intraarticular opioids, has been suggested with the detection of opioid receptors in inflamed tissue. This method has proven suitable for clinical use in small operations (e.g. knee arthroscopy). In this study, we compared epidural analgesia and intraarticular application of morphine plus "on-demand" intravenous analgesia to "on-demand" intravenous analgesia alone.

Thirty-seven patients, scheduled for total knee arthroplasty, were randomly assigned to three treatment groups: in group 1 (EPI) patients received bolus doses of morphine via an epidural catheter; in group 2 (IA) an intraarticular bolus of 1 mg of morphine was applied at the end of the operation with subsequent use of a patient-controlled analgesia (PCA) pump; group 3 (Control), in which only PCA was provided, served as control for both analgesic procedures. Main outcome measures included visual analogue pain scales, total morphine consumption, and stress hormones.

No statistically significant differences in visual analogue pain scales could be detected between the three groups. Application of intraarticular morphine did not reduce the amount of analgesics required for postoperative analgesia as compared to intravenous analgesia alone. Application of epidural morphine significantly suppressed beta-endorphine release, but did not significantly influence other stress hormones as compared to the control group.

Epidural and intravenous analgesia after total knee arthroplasty are equivalent methods of pain relief. In major orthopaedic procedures, application of intraarticular morphine does not reduce analgesic requirements.