Somewhere between 10% and 15% of patients are unsatisfied with their outcome after primary total knee arthroplasty (TKA). In some cases, dissatisfaction is related to poor range of motion, but more often it is related to residual—or even intensified—pain in the knee several weeks after surgery.
In the January 2, 2019 issue of The Journal, Koh et al. report the results of a prospective randomized trial assessing the effects of duloxetine (Cymbalta) in TKA patients who were screened preoperatively for “central sensitization.” In central sensitization, a hyperexcitable central nervous system becomes hypersensitive to stimuli, noxious and otherwise.
Koh et al. randomized 80 centrally sensitized patients (mean age of 69 years), 40 of whom received a multimodal perioperative pain management protocol plus duloxetine, and 40 of whom received the multimodal protocol without duloxetine. During postoperative weeks 2 through 12, patients taking duloxetine reported better results in terms of pain and functional and emotional outcome measures than those not receiving the drug. Patients in the duloxetine group expressed greater satisfaction with pain control (77% vs 29%) and daily activity (83% vs 52%) at postoperative week 12, compared with those in the control group.
This research represents an important advance in identifying and treating patients who are prone to poor outcomes after TKA. The concept of central sensitization is relatively new to the orthopaedic community, and this pharmacologic intervention is likely to be just the first among many that will help these patients. I think it is probable that other, nonpharmacological interventions will eventually be as or even more successful in helping TKA patients with central sensitization. Koh et al. make a valuable contribution in this article by educating us as to the neurophysiologic basis of this condition, and their work should pave the way for more important research in this area.
Marc Swiontkowski, MD
JBJS Editor-in-Chief
OK, let me ask that hard question:
How about giving these “centrally sensitized” chronic pain sufferers duloxetine without the TKA surgery?
Duloxetine will almost certainly not address mechanical problems and dysfunction in advanced knee osteoarthritis, an issue that is by no means a minor problem in a region where squatting toilets are still prevalent, among other issues with activities of daily living.
However, if these findings are to be translated into a bigger scheme, there may be a group of patients with apparent knee pain attributed to osteoarthritis who will not benefit from arthroplasty, regardless of the skill of the surgeon or the quality of the implant, and perhaps…. just perhaps, duloxetine would assist in their neuropathic pain far more than surgery?
While not questioning the integrity or clinical judgment of our Korean colleagues, I am sure we all have seen patients with radiographically advanced degenerative knees who would normally have been offered arthroplasty, but alarm bells are deafeningly ringing in our ears when we consult with these individuals. The characteristic of the pain, the personality of the client, the behaviour and expectations of the patient AND their attending loved ones–these are soft signs that sometimes make it hard to offer the surgery they expected.
To those who believe they have no further responsibilities as long as the patient signs on that dotted line for consent for surgery, our legal colleagues will easily find holes in that defence.
When does a surgeon (no matter how skilled or talented) know not to operate? Only experience, wisdom, and that sixth sense can help me here.