Background: Opioid prescription before knee replacement surgery is associated with longer
hospital stays, more postsurgical pain, and a higher rate of complications. Despite the growing
evidence against opioids, they remain popular preoperative pain management prescriptions.
Objectives: The purpose of this study was to examine the effects of dosage of preoperative
opioid use on orthopedic knee surgery pain control and postoperative outcomes and
complications.
Study Design: Observational, retrospective evaluation.
Setting: University of Wisconsin Madison hospitals.
Methods: The patients underwent orthopedic knee surgery between May 1, 2014 and
April 30, 2015. We randomly selected 197 patients and divided them into 2 groups that had
preoperative opioid dosages of either low dose ≤ 120 mEq morphine (MME) or high dose
>120 MME. Of 197 patients, 100 were in the low dose morphine group, whereas 97 were
high dose. The cutoff at 120 MME was calculated to be the median dosage across all patients.
The primary outcomes were compared, differences in postoperative pain control, and range of
motion (ROM). Secondary outcomes included anesthetic complications, length of hospital stay,
postoperative opioid dose, and postoperative complications.
Results: There were no statistically significant differences between the groups with regard
to postoperative pain control, ROM, and immediate postoperative complications. Both groups
showed similar length of hospitalization (2.199 to 2.304 days; P = 0.374), rate of postoperative
infection, and joint intervention. The high dose group was more likely to have postoperative
hemarthrosis and emergency department (ED) visits. However, the low dose group was more
likely to have hypertension concurrently.
Limitations: Because the study length was restricted to one year, the lack of data on longer
term prognosis may limit extrapolation of data. Subjectivity of pain is difficult to measure and
compare objectively. This study was not randomized prospectively, which may bias certain
results due to unobserved differences.
Conclusions: Preoperative opioid dose did not affect postoperative pain control or ROM in
patients who received knee surgeries. Higher preoperative opioid doses were associated with
more hemarthrosis and ED visits. Further exploration into quality of life indices and surgical
complications such as need for revision may be a fruitful avenue.
Key words: Opioids, analgesic, knee pain, total knee replacement, knee surgery, preoperative opioids, knee outcomes
Is a Single Low Dose of Intrathecal Morphine a Useful Adjunct to Patient-Controlled Analgesia for Postoperative Pain Control Following Lumbar Spine Surgery? A Preliminary Report
