This Level-III retrospective comparative study, entitled “Chronic opioid use prior to total knee arthroplasty,” is a very timely and relevant analysis for primary-care physicians who refer patients in need of joint arthroplasty, surgeons caring for patients who are undergoing joint arthroplasty, and third parties seeking to better understand and predict variability in outcome. With the increased focus on outcomes and value in medicine, the hypothesis that the use of chronic pain medication prior to surgery is an independent risk factor for a less favorable outcome after an orthopaedic procedure is one that needs to be tested and understood.
The major conclusion of this analysis is that preoperative narcotic usage may portend diminished success of total knee arthroplasty at a minimum of two years after surgery. While this paper certainly does not provide the final answers to questions about the appropriate role for opioid pain medication usage, it does elevate the scrutiny of this potentially important and modifiable variable that is under the control of the physician. A critical extension of this work will be to determine whether the use of narcotic pain medication is a surrogate for other as yet unidentified patient characteristics or simply a variable that care providers can modify with knowledge of its potential negative impact. At the very least, identification of the use of opioid medication as a risk factor for reoperation or persistent pain will allow for better surgical risk stratification and patient counseling. With additional analysis and prospective evaluation, the use of opioid medication in the preoperative setting may need rethinking and adjustment of appropriate use indications.
In addition to the important findings related to the specific aims of this paper, there are several interesting related observations that add to the clinical relevance of this paper. Some orthopaedic surgeons may be surprised to note that “opioid medications have become the second or even the first-line treatment of choice for primary-care providers for the management of osteoarthritis-associated pain.” The authors point out that the threshold for prescribing narcotic pain medication among care providers outside of orthopaedic surgery may be decreasing, potentially to the detriment of the surgical results. Moreover, more patients in the opioid group had referral to pain management after surgery, which implies that, once started, opioids are difficult to stop. Management of opioid use after surgery may necessitate a treatment plan directed at that issue.
Some important limitations impact the weight and the generalizability of the findings of this study. One limitation is that the threshold for chronic opioid use was defined as “subjects who had documented treatment with oral opioid medications for knee pain for a minimum of six weeks prior to the arthroplasty procedure.” While that metric is consistent, there was significant variability in the amount of opioid usage among the study group, with a range of 20 to 300 mg/day. Additionally, although the control group was matched to the study group, the authors note that the indication for giving or withholding opioid medication in either group was not well defined and may well be subject to a number of confounding variables. The size of the study group is not large.
In the final analysis, the authors’ observation of a poorer outcome after total knee arthroplasty in patients with chronic opioid use does not fully support a conclusion that opiates should be avoided. However, the study raises important questions regarding the early use of opioids to manage osteoarthritis, the timing of a surgical referral, the perioperative management of pain medication, and the expectations for this subset of patients on opioids who ultimately need knee replacement surgery.