Within diabetes mellitus, there are many forms of neuropathy. The distal, large-fiber, symmetric polyneuropathy is the most common form. The underlying metabolic abnormalities present in diabetes render the peripheral nerve susceptible to chronic nerve compression.
There are 3 currently understood mechanisms for this susceptibility. First, in diabetes, the aldose reductase pathway, which converts glucose to sorbitol, is increased. Sorbitol is hydrophilic, increasing the water content of diabetic nerves, causing them to swell. When the nerve swells in an anatomic area of known narrowing, like carpal or tarsal tunnel, nerve compression occurs. Second, axoplasmic transport is abnormal in diabetes, which means that when peripheral nerve needs to transport proteins to rebuild membranes at sites of compression, it cannot do this efficiently. Third, glucose binds nonenzymatically to collagen. When serum glucose concentration is elevated, it creates advanced glycosylation end products. These bind to the collagen in the peripheral nerve to alter its stress-strain biomechanical properties, making the nerves more stiff.
Not all the patients with diabetic neuropathy should have decompression; just those in whom a compression has been identified with a positive Tinel sign. The surgical treatment includes, depending on the anatomic location of the compression, neurolysis of either the superficial or deep peroneal nerves or release of the tarsal tunnels in the foot (tarsal, medial and lateral plantar and calcaneal tunnels).
In 10 clinical series with a mean relevance score of 70% and a mean methodologic quality score of 50% of the included 875 patients with diabetes and 1053 lower extremity surgeries, 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 with preoperative incidence (odds ratio = 0.066; 95% confidence interval, 0.026–0.164; P < 0.0001).
Thus, following nerve decompression in diabetic patients (1) pain can be relieved, which decreases the cost of medication; (2) sensibility can be improved, which increases balance and thereby reduces the cost of falls resulting in less hip and wrist fractures; and (3) with improved sensibility there will be (a) decreased ulcerations, (b) decreased amputations, and (c) decreased admissions to hospitals for foot infection. The economic cost-benefit to a population of patients with diabetic neuropathy, or to an entire country, can be estimated based on the above observations.