Denervation Procedures
Information for Medical Professionals
What is a denervation?
Denervation procedures target the afferent nerves to a joint. These nerve fibers carry pain signals from joints to the central nervous system. Traditional treatment options for joint pain are targeted at reducing the inflammatory response, either by injecting an anti-inflammatory agent (cortisone or gel) or removing the damaged tissue causing inflammation. A denervation procedure, however, seeks to interrupt the afferent nerve signal, thereby bypassing the body’s perception of pain.
Targeting the nerves instead of the inflammatory response has the benefit of potentially permanently interrupting the pain signal. In addition to cutting the nerves there is additional benefit in transfering the nerves to surrounding muscle. Transfering a nerve to muscle allows the nerve to grow into and innervate the muscle. This causes a change in the nerve fibers from a ‘sensory’ nerve to a ‘motor’ nerve. This nerve change leads to changes in the grey matter of the brain cortex and rewiring of the brain anatomy, permanently shutting off the pain signal from the joint.
Evidence continues to mount for a nerve related solution to joint pain. Radiofrequency ablation has been successfully used in the spine and knee, and surgical denervation has been shown to be beneficial in the hand, wrist, and knee.
Knee Denervation
Knee osteoarthritis is one of the most common orthopedic ailments in the world. There are currently one million total knee arthroplasty procedures conducted in the United States each year, and that number is expected to increase to four million. 1 in 4 adults in the United States suffer from knee pain. Recent evidence suggests that gel injections are not as efficacious as once thought, leaving the primary treatment options for knee OA to cortisone injection and arthroplasty.
There has been a significant increase in the use of arthroplasty, however despite the best surgeons and improved instrumentation only 70-80% of patients report resolution of pain. In addition, evidence suggests that arthroplasty procedures have significant increases in risk with body mass indices above 40, hemoglobin A1C above 7, and multiple comorbidities. Many institutions in the United States have cut off values of BMI 40 and hA1C of 7 for arthroplasty.
The combination of obesity, diabetes, and advanced ailments means many Americans are no longer appropriate candidates for arthroplasty. In addition, a growing number of patients are undergoing arthroplasty but still have pain.
Is Denervation the Solution?
Surgical denervation of the knee has been shown to improve pain in non-arthroplasty candidates. In one study conducted by Dr. Joshua Hustedt at the University of Arizona patients were selected who had been seen by the arthroplasty surgeons and found not to be candidates for arthroplasty. These patients underwent a denervation procedure and had reduction in pain from 8.8 to 2.7 at two years of follow up, with additional improvements in funcational and quality of life scores. In another study from the Medical College of Wisconsin patients were selected for surgical denervation after having residual knee pain after arthroplasty. These patients had pain reductions from 9.4 to 1.1.
Both of these studies suggest that surgical denervation offers an exciting new pain management option for non-arthroplasty candidates and patients who have residual knee pain following arthroplasty.
What does the procedure entail?
The surgical denervation procedure is done as an outpatient and can be done under spinal anesthesia in patients at high risk. A small 3 cm incision is made on either side of the knee. The superomedial and superlateral geniculate nerves are identified, transected, and transfers to the vastus medialis and lateralis. The inferomedial and inferlateral geniculate nerves are indentified and transected. The procedure is done minimally invasive with an endoscope. The incisions are kept small and 7 cm away from the midline to prevent any issues with an anterior approach for arthroplasty in the future.
Surgical Pictures of Geniculate Nerves
New Endoscopic Surgical Incision size of 3 cm
Geniculate Nerve
Non-Arthroplasty Patients
BMI > 40
Hemoglobin A1C > 7
History of Infection
Geniculate Nerve after Transection
Nerve Transfer to Vastus Muscle Cuff
Who are the ideal Candidates?
Pain after Arthroplasty
20 - 30 % of patients report residual pain after a total knee arthroplasty
Multiple Comorbidities
Advanced age
Chronic Conditions
Will this cause a chaot joint (advancement of arthritis)?
One of the major concerns often raised is: Will a denervation procedure lead to rapid progression of arthritis or a charcot joint? Denervation procedures do not contribute to rapid arthritis progression. A charcot joint happens primarily because of lack of blood flow to the joint in patients with diabetes. Our denervation techniques are partial denervation procedures which target the sensory nerves only. In the knee, the posterior capsule is left intact where a majority of the proprioceptive fibers are located. Patients, therefore, have a reduction in their pain but not proprioception. The combination of maintaining blood flow and proprioception means that patients do not see a rapid advancement in arthritis or a charcot joint.
Pain Management Providers and Interventional Radiologists
Who to Refer
Radiofrequency Ablation or Embolization Patients
Radiofrequncy ablation and embolization has been shown to significantly improve pain in patients with knee osteoarthritis. However, the effect of ablation and embolization are temporary, usually 6-12 months. In addition, the responses can be variable depending on patient anatomy of the geniculate nerves and the proximity of the probes to the nerves. Patients who have failed ablation or embolization or desire longer lasting pain relief are great candidates for surgical denervation.
Chronic Pain Management Patients
Surgical knee denervation has the potential to remove knee pain. Most of our patients are able to wean off all narcotic pain medications only a few weeks after the procedure. Any patient who has been deemed to have failed other treatments and is on chronic pain meds can be referred for surgical denervation.
Orthopedic Surgeons
Who to refer
Residual Pain after Arthroplasty
20-30% of patients may report continued knee pain following a well performed arthroplasty. This may be due to residual inflammatory responses in the surrounding tissues. Surgical denervation can be very helpful in these patients as it interrupts the afferent pain signal from the joint to the brain.
A study of 50 patients published in the Journal of Arthroplasty has shown the benefits of surgical denervation for post arthroplasty pain.
Non-Arthroplasty Candidates
Patients who are deemed to not be candidates for arthroplasty may be good patients to refer for consideration of surgical denervation. These patients usually are those with elevated risk due to high BMI, elevated hemoglobin A1C, advanced age, or overall comorbidity burden.
Hand, Wrist, and Thumb Denervation
Hand, wrist, and thumb denervation has seen significant rise in popularity in the past few years. This technique offers relief of pain for finger arthritis of the PIP and MCP joints, as well as base of thumb pain (CMC), and wrist pain. Recent studies have shown the benefits of denervation as compared arthroplasty.
Two recent studies compared denervation of the base of thumb (CMC) to arthroplasty. One study by Dr. Joshua Hustedt at the University of Arizona showed equivalent outcomes at one year with pain, function, and quality of life, but with return of function in 3 weeks with denervation versus 4 to 5 months with arthroplasty. A similar study from Johns Hopkins also showed equivalent outcomes of denervation and arthroplasty with two year follow up.
Wrist denervation has also been shown to provide significant pain relief. A study from the Mayo clinic examined the use of wrist denervation and found excellent pain relief with denervation only with 3 to 4 year outcomes.
