As we evolve in our treatment of foot and ankle conditions, it seems like each treatment meets with some reservation from the medical community. As podiatric physicians, our mindset is scientific in nature and we need hard facts and evidence-based results to show each treatment option is beneficial. I am with the mainstream in that thinking but I also try to rationalize a treatment option and see why it may or may not benefit a patient.
To that extent, there has been a great deal of interest in treatment options for diabetic neuropathy. A. Lee Dellon, MD, a peripheral nerve plastic surgeon from Johns Hopkins University in Baltimore, first advanced the idea of surgical nerve decompression. He originally was a hand surgeon and many of his patients were diabetic. These patients expressed an interest in treating their painful feet similar to how Dr. Dellon treated their hands. Dr. Dellon has dedicated the past 20 years or so to treating peripheral nerve conditions and has made significant inroads in the surgical treatment of peripheral neuropathy conditions.
With time, Dr. Dellon has also developed a nerve testing machine that allows for the quantitative analysis and diagnosis of peripheral nerve entrapments. One would employ this machine in the workup and postoperative re-evaluation of peripheral nerve surgery in the lower extremity. About 200 doctors of all surgical backgrounds are now performing peripheral nerve releases in the foot and leg around the world. The background of these surgeons ranges from podiatry and orthopedics to plastic surgery and neurosurgery.
What Research Reveals About The Etiology Of Diabetic Neuropathy
There is extensive research on the potential causes of diabetic neuropathy. Many of these animal studies examined streptozotocin injections. Many of the studies noted there was increased intraneural edema from sorbitol infiltration as well as increased fibrosis surrounding the nerve and involving the ligamentous retinaculum at sites of potential compression. Tightness and stiffness of the retinaculum and edema of the nerves have been noted to cause a decrease in axoplasmic flow and eventual vascular damage to the nerve, resulting in axonal degeneration and the dropout of nerve fibers. Researchers have also noted the compression may be the potential cause of pain, axonal degeneration and sensation loss.
Although one must consider metabolic issues in the cause of diabetic neuropathy, several studies have compared regions of potential nerve compression to normal nerve regions in patients with diabetes. These comparisons show a dramatic difference in the quality and damage noted to the nerve. While we are essentially still learning the overall causes of nerve pain and neuropathy in patients with diabetes, there is enough evidence and basic science-based research to show compression plays a role in part of the underlying pain and symptoms.
Understanding The Essential Elements Of Peripheral Nerve Surgery
One would perform this surgery with the patient under sedation or a general anesthesia with a local nerve block as a possible option. The outpatient procedure lasts about one and one-half to two hours.
The surgical technique is beyond the scope of this article but involves the release of the common peroneal nerve at the neck of the fibula with release of the peroneal retinaculum in that region. The surgery also entails release of the deep peroneal nerve on the dorsum of the foot, including the extensor retinaculum over the nerve and transection of the extensor hallucis brevis tendon over the dorsum of the first metatarsal. The third nerve release involves the tibial nerve and its branches, including the medial, lateral plantar and calcaneal branches. Finally, one would perform an internal microvascular neurolysis of any scarred or fibrotic nerves in order to decompress internal fascicular compression on the nerve bundles as deemed necessary.
It is not a very difficult process or surgery and the most difficult aspect is the tarsal tunnel region. There is also a rapid recovery process for the patient. One would emphasize no weightbearing or limited touchdown weightbearing for two to three weeks until removing the sutures. Patients may then progress to increased weightbearing, as tolerated, and physical therapy.
In terms of complications, one mostly sees superficial wound dehiscence, which clinicians can treat very easily with local wound care and antibiotic therapy. There may be some mild increase in tingling and pain at first as the nerve begins to hyperreact to decompression but this pain resolves over time.
Ensuring Appropriate Patient Selection
To put it simply, this surgery is not meant for every patient with diabetes. The results have shown that the success of the procedure is not age dependent and that, with proper patient selection, the procedure will help improve pain relief in most cases.
However, as I stated earlier, the initial problem was treatment of painful neuropathic legs. These patients cannot sleep at night, cannot walk well and often use multiple medications, including narcotics, to treat their pain. They are often young and would like to be more active.
As the results have been good in the painful cases, the pendulum on diabetic nerve entrapment is also swinging to the extreme and patients with no pain are being treated with decompression for sensation restoration. This is far more risky and often surgeons are dealing with a patient who has no true symptoms and is only worried about possible ulcer formation. Why not treat such a case with insoles, local foot care education and observation?
In most cases, including studies and results from Dr. Dellon, sensation restoration in a patient without pain is a 50-50 shot. In contrast, resolution of pain in cases of painful neuropathy is 80 percent successful when there is a positive Tinel’s sign of the nerve region. The results of sensation restoration on the average non-symptomatic patient with diabetes are not good enough for me to pursue.
That said, if there is a young patient with multiple previous ulcers, excellent circulation, a positive Tinel’s sign and no pain, I may discuss the surgical options and note that it may help prevent ulcer formation if the patient can feel pain.
However, my current protocol is far more selective. I reserve this procedure only for patients who have severe pain; no relief from pain with oral medications such as gabapentin or duloxetine HCl; excellent circulation; and multiple risk factors. In these cases, the results are far more predictable and the outcomes can change lives.
What really changed my mind about this procedure and the underlying philosophy behind diabetic neuropathy and sensation restoration is the fact that a large number of carpal tunnel and ulnar nerve transposition surgeries in the upper extremity are performed on patients with diabetes. Many of the hand surgeons I know at UCLA and in my community do not think twice about the idea of carpal tunnel surgery on a patient with diabetes, and often will state that carpal tunnel syndrome may be partly due to diabetes and its complications.
So why shouldn’t we perform nerve decompression in the foot? I have found, both through my cases and in the literature reviews, that it is very difficult to make a properly selected patient with symptoms worse. One may not make the patient perfect but there are good to excellent outcomes in most cases. Furthermore, what is the downside as long as there are no surgical complications? In the worst case scenario, a patient will have nerve pain that he or she may have had prior to surgery.
What is most exciting about the progress of peripheral nerve surgery is that the peripheral neuropathy fellowship group to which I belong has begun further study of the benefits of nerve release on patients with diabetes. We have started to note potential benefits that may be far more detailed than nerve pain relief.
Some studies show the shuffling gait pattern noted in patients with diabetes may be partly due to weakness of the dorsiflexors of the foot that are controlled by the common peroneal nerve. Calf pain may also partly be related to compression of the common peroneal nerve. Increases in temperature and vasodilation to the foot have been seen with tarsal tunnel and plantar nerve release due to the possible autonomic factors noted with nerve compression. Furthermore, the lateral plantar nerve is known to be associated with innervation of the intrinsic musculature of the foot, which may be the cause of hammertoe formation. There is a possible improvement in intrinsic muscle function of the foot with lateral plantar nerve release.
I believe we need to keep the pendulum on diabetic nerve surgery swinging without the swing going to an extreme. Many physicians in all backgrounds of medicine have shown good to excellent outcomes in their patient population. However, we need to produce detailed studies of the results and also follow these patients for five to 10 years prior to making a full conclusion.
That said, following in the findings of many hand surgeons, there is a definite positive to helping a patient with painful debilitating neuropathy. In my experience, I have not found medications or therapy to be very effective for this condition. I believe nerve decompression surgery is a far better treatment option when one ensures appropriate patient selection in a responsible and educated manner.
Dr. Baravarian (top photo) is Co-Director of the Foot and Ankle Institute of Santa Monica. He is an Associate Professor at UCLA Medical Center and is the Chief of Podiatric Surgery at Santa Monica/UCLA Medical Center. Dr. Baravarian may be reached via e-mail at firstname.lastname@example.org .
Dr. Steinberg (left photo) is an Assistant Professor in the Department of Surgery at the Georgetown University School of Medicine in Washington, D.C. He is a Fellow of the American College of Foot and Ankle Surgeons.