In a previous blog, I have highlighted the limitations of current research on therapeutic nerve blocks, and indicated pragmatic approaches as a great way to improve the science of pain procedures.
A recently published study gives opportunity to reflect on a research model that is very promising, and yet underused, to study pain procedures.
We should ask the right question
Pain procedures are not necessarily an alternative to conservative treatments, such as medications or physical therapy. They are frequently proposed as an addition in a multimodal and multidisciplinary approach. For instance, for patients who experience insufficient progress with physical therapy, a clinically relevant question is whether performing a procedure in addition to physical therapy would improve their condition. This is clinically more relevant than the question whether procedures should be used instead of physical therapy. Physical therapy remains of essential importance to improve function and/or prevent worsening (read more here).
Adding an intra-articular injection to current treatment improves hip pain
The right question was asked in an excellent study published on April 6, 2022 in the British Medical Journal. Patients with chronic hip pain due to osteoarthritis were randomly assigned to three groups. All three groups received "best current treatment", consisting in a "bespoke leaflet on exercise and functional activities, and personalized advice and information about weight loss, exercise, footwear, walking aids, and pain management". This was the only treatment in one of the three groups. The second and third groups received, in addition, injections into the hip joint of a steroid and a local anesthetic (group 2), or of a local anesthetic alone (group 3). Patients and study staff that evaluated the treatment were not aware of group allocation 2 or 3. There was no placebo control.
Patients who received the hip injection of steroid and local anesthetic (group 2) had less pain, better physical function, less psychological distress, better quality of life, more work presenteeism and better performance over 6 months, compared to patients who had "best current treatment" without injection.
The group with steroid and local anesthetic was in general superior to the group with local anesthetic alone.
The differences between injection and no injection were much more marked during the early time after the injection (2 weeks -2 months), than later (4-6 months). There was no difference between injection and no injection at 6 months. However, more patients in the injection group were satisfied with treatment (58% vs. 34%), and wanted the same treatment again (64% vs. 34%). The number-needed-to-treat (NNT) was 4 and 3, respectively: 4 and 3 patients have to be treated with injection of steroid and local anesthetic to have 1 patient who is more satisfied with the injection and would like to repeat the treatment. This is considered a good outcome in the treatment of chronic pain.
Do we need a placebo control?
Placebo-control would establish the efficacy of the procedure, but I would argue that we do not strictly need a placebo-controlled study. It seems that the steroid - local anesthetic group was superior to the group with local anesthetic alone, and both patient and study staff were not aware of the group allocation. This provides evidence that the improvements can unlikely be attributed to pure placebo effects. Like every treatment we offer, there is a likely a placebo component, but in clinical practice placebo effects are welcome.
Is the short-term effect clinically valuable?
Like other interventional treatments, the effect does not last very long. If we repeat the injection every few months, what are the concerns? For instance, is there any risk of joint damage with repeated injections of steroids? This concern may be of limited importance for those patients who are anyway candidate for hip replacement and are postponing the surgery by few months or 1-2 years. However, the repeated injections of steroids may be concerning in other situations, and particularly in young patients.
While we will very unlikely have randomized controlled trials that address questions of long-term effectiveness and safety, well-designed prospective cohort studies with long-term follow-up would provide very valuable information to guide clinical practice.
Comparative effectiveness randomized controlled trials, followed by prospective long-term cohort studies, will greatly improve the science of interventional pain management.