Tarsal Tunnel Syndrome

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The natural history of diabetic distal sensory polyneuropathy (DPN) is well-established. Diabetic neuropathy is a progressive, irreversible, large fiber, symmetric polyneuropathy in its most common form.

Diabetic peripheral neuropathy leads to ulceration and/or amputation in 15% of the patients. Bilateral amputation is frequently necessary. That's right, one of out six diabetic patients in their lifetime.

Eighty to eighty-five percent of amputations are preceded by non-healing ulcers in patients with neuropathy. In fact, it is estimated that 27% of direct medical costs of diabetes mellitus is related to (DPN) diabetic neuropathy. The number of patients with diabetes is increasing as the obesity epidemic escalates.

The literature documents the best methodology of testing sensibility and identification of treatable patients with pain and/or sensibility loss from diabetic neuropathy with or without ulceration using quantitative sensory testing. This may allow intervention before the entrapment causes irreversible nerve damage. In the presence of a positive Tinel's sign at the site of a pinched nerve (compression), we should then offer them or make available to those who are medically stable selective nerve decompression. We can predict with 90% certainty that the outcome will be beneficial and should result in more comfortable living and prevention of diabetic foot ulcers whether the ulcers are primary or recurrent. This should prevent ultimate amputation. It only makes sense that since we have proven that the nerves enlarge too much for the compartments that they are in, they need to be decompressed surgically. The response to treatment is dramatic and predictable and cannot be achieved through simple medical or orthotic and footwear management of the patient with diabetes.

Since the introduction of the NMT Pressure Specific Sensory Device (PSSD)* by A.L. Dellon at Johns Hopkins University Medical Center, Semmes-Weinstein monofilament testing has clearly been made obsolete in the monitoring of diabetic neuropathy. Use of Semmes-Weinstein filaments may allow diabetics to progress beyond the optimal time for possible intervention because the filaments are not graduated in enough increments. By the time of identification of a problem with Semmes-Weinstein, fairly advanced neuropathy already exists. In diabetes, aldose reductase, an abnormally functioning enzyme, results in excessive conversion of glucose into sorbitol, a non digestible sugar. This accumulates in the nerves and causes them to swell resulting in nerves that are too big for the compartments that they traverse in addition to whatever other physiologic abnormalities are occurring in the nerves.

It only makes sense that since we have proved that the nerves of diabetics may enlarge too much for the compartments that they are in, they may need to be decompressed surgically. The response to treatment is dramatic and predictable and cannot be achieved through simple medical (eg Lyrica) or orthotic footwear management of the patient with diabetes.

Dellon reported the first group of neuropathy patients to undergo decompression of upper and lower extremity peripheral nerves. Six subsequent studies confirm that decompression of the tibial nerve and its branches at the tarsal tunnel (medial and lateral, plantar, and calcaneal branches) can relieve pain in 90% of patients with painful diabetic neuropathy and can restore sensibility in as many as 80% provided they exhibit a positive Tinel's sign (electronic feeling upon tapping the nerve). In the December 2004 Annals of Plastic Surgery, Aszmann, et al reported on a group of 50 diabetic patients who had undergone tarsal tunnel release. All had pulses in their feet confirming that circulation was not the problem. He looked for ulceration or amputation in either extremity. Follow-up averaged 4.5 years (range 2-7 years). Only one of the 50 had an ulcer on the operative side before surgery. No amputations or ulcerations occurred in the operative patients postoperatively. In contrast, 25% of the unoperated feet had developed ulcers and another three (about 6%) went on to require an amputation.