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8 Articles in Volume 16, Issue #3
CDC Issues Final Guidelines for Opioid Prescribing: PPM Editorial Board Responds
Don't Flinch From Prescribing Pain Medications!
Help Patients Achieve Diet/Weight Goals to Manage Pain
Hormone Testing and Replacement: Status Report 2016
Living With, and Managing, Chronic Pain: A Patient’s Story
Nerve Decompression Surgery Can Reverse Neuropathy of the Foot
Pulsed Electromagnetic Field Therapy: Innovative Treatment for Diabetic Neuropathy
Specialized Pharmacies Step Into Risk-Management Role

Nerve Decompression Surgery Can Reverse Neuropathy of the Foot

Similar to carpal tunnel syndrome surgery, nerve decompression surgery helps improve symptoms of diabetic peripheral neuropathy of the foot and prevents amputation.

Nerve decompression surgery can be used effectively to treat the pain and complications of diabetic peripheral neuropathy (DPN), reversing the symptoms of numbness and tingling, and in most cases, preventing amputation.

This article will review the science behind DPN and explain how this surgical procedure may benefit your diabetic patients.

Etiology of DPN

While there are many hypotheses about what causes diabetic neuropathy, they all have one theme in common—that is, DPN is a systemic disease that is progressive and irreversible.1,2 The only way to prevent DPN is through proper glycemic control. It has been established that hyperglycemia is responsible for vascular complications, which have been linked to the development of neuropathies in diabetic patients. An accumulation of sorbitol and fructose within the nerve caused by unchecked hyperglycemia alters the aldose reductase biochemical pathway.

Additionally, an increase in blood glucose levels causes an increased binding of glucose to collagen resulting in advanced glycosylation end products (AGEs), which thicken the connective tissue of both the nerve and the tunnel and constrict the anatomical site it runs through.3

Like water flowing through a dam, nerve decompression surgery can reverse the symptoms of numbness and tingling (nerve compression and entrapment) associated with diabetic neuropathy.

In 1978, Jakobsen published a landmark study of the effect of hyperglycemia on the peripheral nerve—specifically, the expansion of the endoneurial space in the sciatic nerve of diabetic rats.4 Interestingly, he found significant changes in the sciatic nerve upon necropsy. The sciatic nerves were up to 50% larger in a cross-sectional area, had significant edema, but surprisingly, the large fibers (A-α, A-β) were still well myelinated for the most part. From his work some very important concepts have been proffered:

  • The peripheral nerve, which is subjected to hyperglycemia, becomes edematous, and therefore is larger in a cross-sectional area
  • The nerve has less ability to repair itself, because there is a slowing of anterograde and retrograde transport in the axon
  • The nerve is more susceptible to compression
  • The nerve remains relatively well myelinated in areas where there is no focal compression.

What does this mean clinically? First, we know that if the nerve is edematous, it is more likely to become entrapped in small, non-expandible anatomical tunnels or constrictive areas (Figures 1-7). This has been demonstrated in both the upper extremity and in the leg and foot. In fact, the incidence of carpal tunnel syndrome in the general population in the United States is 2%, while in the diabetic population it is estimated to be between 14% and 30%.5


Could this focal physical entrapment of a nerve caused by a systemic disease (diabetes) account for most of the symptoms attributed to DPN rather than a true axonopathy itself? Could this entrapment be the cause of the gamut of symptoms (pain, numbness, burning, loss of sensation, etc), which manifest as “diabetic symmetric polyneuropathy”?

The skeptic may ask how the patient with diabetes develops a “stocking” or “glove” distribution of their neuropathy from a focal entrapment. If there is only a focal entrapment, what is accounting for the majority of symptoms? Table 1 lists peripheral nerve compression pathology, illustrating that focal entrapment can cause widespread symptoms.

Surgical Treatment of Entrapment

It is well documented that the pain and symptoms of carpal tunnel syndrome can be relieved by peripheral nerve decompression in the diabetic patient.6-12 In the 1980s, MacKinnon and Dellon noted that most diabetic patients with carpal tunnel syndrome and symptoms of peripheral neuropathy—such as numbness and tingling in their hands—regained their sensation after carpal tunnel decompression surgery.6 The patients’ pain also improved, if it was not completely eliminated.

The researchers then went on to discover that if the ulnar nerve, and subsequently the radial sensory nerves, were surgically decompressed, most of these patients would then regain sensation in the remainder of their previously “gloved” distribution of “polyneuropathy sensory deficit.” It is easy to visualize how this combination of peripheral nerve compressions can produce a “glove” effect.6 These pleasantly surprised and satisfied patients had another question for the surgeons. “What can you do for my feet?” Why would the same concept not apply to the lower extremities? Certainly nothing metabolic has been changed by surgery!

Interestingly, when evaluating patients with diabetes after lower extremity peripheral nerve decompression, Maloney et al showed a predictive success rate of 88% for decompression of patients’ lower extremities.13 What occurred was that the focal nerve entrapment was relieved (the true pain generator), and their pain disappeared or was greatly diminished. Immediate sensory improvement with improved motor function is often seen in the postoperative acute care unit after nerve decompression.

There has been extensive research into the effects of peripheral nerve decompression done for the treatment of DPN symptoms, and in particular tarsal tunnel decompression.14,15 In more recent study, greater effects were seen when the common peroneal nerve was decompressed in addition to the tarsal tunnel.16 This not only means that symptomatic DPN can be effectively treated via surgical nerve decompression, but that surgical decompression can prevent the complications of DPN from developing.17

Preoperative Evaluation

While it is not within the scope of this article to discuss the specifics of the surgical techniques, there are some points that the reader might find helpful. First, in some provider groups there is a misperception that it is not safe to operate on a patient with diabetes. This is simply not true, and in fact, more foot surgery is performed on patients with diabetes than without.

It is imperative, however, that the vascular status of the patient is evaluated and determined to be adequate, usually with an ankle brachial index (ABI—the ratio of the blood pressure in the lower legs to the blood pressure in the arms)—of ≥0.7 (which is adequate perfusion to safely perform surgery, though normal ABI is 1.0 to 1.2) with palpable pulses and little trophic change to the skin.18 In fact, this surgery is now being implemented into limb salvage surgery regimens.19

The patient is ideally allowed to walk the same day as the procedure, and the complication rate has been very small with the most common complication being a partial wound dehiscence easily managed by local wound care.19

How do complication rates of foot surgery compare to conventional care in patients with diabetes? In other words, can decompression surgery prevent ulcers and amputations? In a 2-year study of infection rates in 1,666 diabetic patients in a managed-care setting, Lavery et al reported that 151 patients (9.1%) developed 199 foot infections, almost universally associated with an ulcer or penetrating wound, yielding an overall hospitalization rate of 3.7%.20 The development of deep-seated ulcers significantly increased rates of amputation (P<0.001).

By comparison, a study of 1,322 decompression surgeries performed on 1,025 patients with diabetes by 36 different surgeons showed only a 0.8% admission rate.21 Data for infection was not included in this registry, but in over 12 years of performing more than 500 of these surgeries in our private practice, there have been no hospital admissions for infection, and fewer than 10 patients who developed minor local cellulitis.

This compares favorably with the experience reported by Wukich et al, in which consecutive surgical cases were evaluated—including nondiabetic patients without neuropathy, nondiabetic patients with neuropathy, patients with diabetes but no diabetic complications, and patients with diabetes who had at least 1 complication of diabetes.22 The authors found that the overall surgical site infection rate in this study was 3.1%. But when they drilled down into the data, found that complications rates were higher in patients with neuropathy and elevated hemoglobin A1c, rather than just diabetes.

“Patients with complicated diabetes had a 7.25-fold increased risk of surgical site infection compared with nondiabetic patients without neuropathy and a 3.72-fold increased risk compared with patients with uncomplicated diabetes,” wrote the authors. “Despite this, nondiabetic patients with neuropathy did not have a significantly higher rate of surgical site infection than patients with uncomplicated diabetes, and the frequency of surgical site infection in the group with uncomplicated diabetes was not significantly different from that in the nondiabetic patients without neuropathy.”22

Accurate diagnosis and assessment is imperative, preoperative patient education mandatory, and formalized training in peripheral nerve surgery is a prerequisite for patient safety and excellence of outcomes. It is also imperative to stress the point that not all patients with diabetes with neuropathic symptoms are candidates for this type of surgery, and that a highly predictive factor is a positive Tinel’s sign at the known fibro-osseous tunnel sites of compression.

Assessing Decompression Surgery

The reviews of the efficacy of decompression surgery as a treatment for symptomatic diabetic neuropathy have been mixed. In 2006, the American Academy of Neurology (AAN) conducted a literature review of surgical decompression and concluded that “the literature revealed only Class IV studies concerning the utility of this therapeutic approach. Given the current evidence available, this treatment alternative should be considered unproven.”23

However, the literature also reveals very positive studies of decompression surgery. One small study by Aszmann et al compared the impact of surgery on the development of ulcers and amputations in an operated and non-operated limb of 50 patients with diabetes. The authors reported no ulcers or amputations in the decompressed leg, compared to 12 ulcers and 3 amputations in the contralateral limb, P <0.001.24

In a separate report, Dellon wrote that “…there have been 15 peer-reviewed studies that used the inclusion criteria of:

  1. Presence of symptomatic neuropathy
  2. Positive Tinel’s sign over the tarsal tunnel demonstrating a site of compression
  3. No previous history of ulcer or amputation
  4. Used the Dellon Triple Decompression technique.

These studies demonstrated relief of pain in 88% and restoration of sensation in 79% of patients.”25

More recently, Baltodano et al and Garrod et al have published reviews, including literature that show the value for decompression surgery in pain relief, sensory recovery, and ulcer and amputation prevention.26,27 Baltodano et al review of 10 studies included 875 patients with diabetes. Pain relief >3 points on visual analog scale occurred in 91% of patients; sensibility improved in 69%. Postoperative ulceration/amputation incidence was significantly reduced compared to preoperative incidence (P<0.0001).26

In 2010, Nickerson showed similarly compelling findings.28 Certainly, while not randomized, these patients served as their own controls with similar diets, lifestyles, and glycemic control. There are a plethora of studies that refute this suggestion of bias and placebo effects by the AAN, albeit they may not be Class I studies.18,19,25,29-39 A prospective study of 560 decompression patients by Zhang et al showed significant improvement in nerve conduction velocity, quantitative sensory testing, and the Toronto Clinical Scoring System for neuropathy. Even more impressive was what investigators found after 18 months of follow up: 37% of these patients (208) had a Wagner Classification 1 ulcer before surgery. At 18 months the few preoperative active ulcers had all healed and there were no recurrences present in these 208 patients.40

It is likely that semantics played a role in these AAN subcommittees’ conclusions, in that as we know it, it is impossible to operate on DPN, but it is completely reasonable to decompress a focal nerve entrapment superimposed on DPN. We would propose that AAN consider the same question for carpal tunnel surgery in the patient with DPN. Would their conclusion be that it is “unproven” to decompress a focal entrapment of the median nerve? We don’t think so.

In my decade and more of experience with this surgery (SLB), I have seen an 85% return rate of the operated patients seeking decompression of their second extremity. There is no argument that more scientifically robust studies are needed to address the “evidence-based medicine” critique. Level 1 studies are now finally appearing. Macare van Maurick demonstrates with a randomized, prospective, within-patient protocol that unilateral decompression by Dellon’s technique significantly relieves pain in the operated extremity and also in the contralateral leg.41

Confirmatory findings have recently been presented at medical meetings. At the 2016 American Society for Peripheral Nerve surgery annual meeting, Best et al presented the results of decompression surgery in 33 patients with diabetes who had good glucose control and diabetic peripheral sensorimotor polyneuropathy (DSP).42 The researchers found that “in this blinded randomized controlled trial, surgical decompression of the common peroneal, deep peroneal and tibial nerves significantly reduced pain for patients with DPN (P=0.04).”

Shai Rozen, MD, presented the initial results of an even stronger Level 1 protocol at the 2015 Association of Extremity Nerve Surgeons and 2016 American College of Foot and Ankle Surgeons.43 In his presentation, DPN patients were randomized to non-operative best care or nerve decompression plus best care. The operative cases had legs randomized to unilateral decompression and contralateral sham surgery with only skin incisions. This double blinding of observers and patients to intervention legs yielded strong evidence of durable pain relief for the decompressed legs, highly significant in comparison to non-operated control cases at both 1 and 4.5 years.43

Interestingly, pain decreased significantly in sham operated legs as well, though to somewhat lesser degree than those decompressed. This suggests effects at spinal cord level or circulating neuroactive injury molecules, which validates anecdotal clinical impressions of bilateral effects with only unilateral decompression, and confirms the similar observations of Makere van Maurik.41 We anxiously await the imminent publication of the Best and Rozen studies.

Rankin et al have extended the multiple reports of protection against diabetic foot ulceration, recurrences, and subsequent amputation to consider their economic implications.44 They calculate $1 billion per year in economic and societal benefits would be available by the 5th year if nerve decompressions were routinely applied to the 300,000 neuropathic diabetes foot ulcers occurring annually. This would all accrue by protection against recurrences and avoiding its myriad costs. Such savings could even be expanded by application to some neuro-ischemic situations45 and aborting incipient first ulcerations in cases selected by screening technologies that already exist.46

Conclusion

Surgical decompression for the patient with DPN and superimposed focal nerve entrapment are life-changing surgeries—and have saved patients’ lives not only from the sequelae of ulcer and subsequent amputations, but also from suicide. The reader is urged to consider the wide-ranging ramifications of this surgery for the reduction or elimination of pain for the patient, the prevention of diabetic ulcers and amputations, the improvement in the quality of life, and reduction in healthcare costs. It is easy to put this into perspective when performing this type of surgery for the patient, and receiving daily positive feedback from these patients who suffer with horrible symptoms and life changing complications. We would urge any provider who frequently encounters patients with DPN, regardless of surgical specialty, to look further into this. A good resource is the Association of Extremity Nerve Surgeons and their published Guidelines on the topic. Finally, the reader must recognize the fact that while no surgeon is able to operate on DPN, we are clearly able to decompress superimposed nerve entrapments, known to be prevalent in patients with diabetes, and relieve symptoms that are caused by this compression.

Last updated on: April 15, 2016
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