EVALUATION OF PERIPHERAL MICROCIRCULATION IMPROVEMENT OF FOOT AFTER TARSAL TUNNEL RELEASE IN DIABETIC PATIENTS BY TRANSCUTANEOUS OXIMETRY EMILIO TRIGNANO, M.D., Ph.D., 1,2 NEFER FALLICO, M.D., 3 * HUNG-CHI CHEN, M.D., M.H.A., F.A.C.S., 2 MARIO FAENZA, M.D., 1 ALFONSO BOLOGNINI, M.D., 1 ANDREA ARMENTI, M.D., 3 FABIO SANTANELLI DI POMPEO, M.D., 4 CORRADO RUBINO, M.D., 5 and GIAN VITTORIO CAMPUS, M.D. 1 Background: According to recent studies, peripheral nerve decompression in diabetic patients seems to not only improve nerve function, but also to increase microcirculation; thus decreasing the incidence of diabetic foot wounds and amputations. However, while the postoperative improvement of nerve function is demonstrated, the changes in peripheral microcirculation have not been demonstrated yet. The aim of this study is to assess the degree of microcirculation improvement of foot after the tarsal tunnel release in the diabetic patients by using transcutaneous oximetry. Patients and methods: Twenty diabetic male patients aged between 43 and 72 years old (mean age 61.2 years old) suffering from diabetic peripheral neuropathy with superimposed nerve compres- sion underwent transcutaneous oximetry (PtcO2) before and after tarsal tunnel release by placing an electrode on the skin at the level of the dorsum of the foot. Eight lower extremities presented diabetic foot wound preoperatively. Thirty-six lower extremities underwent surgi- cal release of the tibialis posterior nerve only, whereas four lower extremities underwent the combined release of common peroneal nerve, anterior tibialis nerve, and posterior tibialis nerve. Results: Preoperative values of transcutaneous oximetry were below the critical thresh- old, that is, lower than 40 mmHg (29.1 6 5.4 mmHg). PtcO2 values at one month after surgery (45.8 6 6.4 mmHg) were significantly higher than the preoperative ones (P 5 0.01). Conclusions: The results of postoperative increase in PtcO2 values demonstrate that the release of the tarsal tunnel determines a relevant increase in microcirculation in the feet of diabetic patients. V C 2015 Wiley Periodicals, Inc. Microsurgery 36:37–41, 2016. Diabetic peripheral neuropathy is recognized as the main factor in the etiopathogenesis of diabetic foot ulcers. 1,2 Lack of sensation from neuropathy is responsi- ble for unrecognized repetitive trauma and pressure load- ing leading to skin injury. Moreover, diabetic metabolic abnormalities make peripheral nerves more susceptible to chronic compression when coursing through their ana- tomical tunnels. 3,4 Increased pressure has been docu- mented intraoperatively in the medial and lateral plantar tunnels in patients with diabetic neuropathy. 5 Nerve com- pression causes compression of the vasa nervorum, thus leading to distal nerve ischemia, and decreased axoplas- mic flow. 6 This impairs the ability of the nerve to com- municate with muscle fibers and skin mechanoreceptors, resulting in loss of function or sensation. Surgical decompression of peripheral nerves in patients with diabetes is reported to restore sensation and improve function. For the lower extremities, this consists of surgery for femoral nerve, peroneal nerve, or tarsal tunnel release. For the upper extremities, this surgery consists of carpal tunnel release, cubital tunnel release, or decompression of radial nerve. 7 Surgical nerve decompression at lower-leg fibro-osse- ous tunnels has been demonstrated to significantly improve sensitivity at the extremities and to reduce the incidence of diabetic foot ulcers in neuropathic high-risk feet. 8 Surgical decompression of the tarsal tunnel deter- mines an improvement of nerve function as well as an increase in microcirculation. 9 However, while the postop- erative improvement of nerve function is demonstrated by improvement in pain levels, recovery of sensation, improved balance, and decreased ulceration and amputa- tion, 10 the changes in vascularization have yet to be evaluated. The technique of transcutaneous oximetry (PtcO2) allows the estimation of the partial pressure of oxygen on the skin surface by employing noninvasive heated electrodes. 11 Because oxygen is carried to tissues by blood flow in the arteries, TCPO2 is an indirect measure of blood flow. This test is often used to evaluate advanced peripheral arterial disease, a condition in which blood flow to an extremity (usually the leg) is greatly reduced. Results of this test help physicians determine how severely tissues are deprived of blood flow. The test 1 Department of Plastic and Reconstructive Surgery, University of Sassari, Sassari, Italy 2 Department of Plastic and Reconstructive Surgery, China Medical Univer- sity Hospital, Taichung, Taiwan, Republic of China 3 Department of Plastic and Reconstructive Surgery, “Sapienza” University of Rome, Rome, Italy 4 Department of Plastic and Reconstructive Surgery, Sant’Andrea Hospital, Rome, Italy 5 Department of Plastic and Reconstructive Surgery, University of Salerno, Fisciano Salerno, Italy *Correspondence to: Nefer Fallico, M.D., Via Val Savio 3, 00141, Rome, Italy. E-mail: nefer.fallico@gmail.com Received 6 September 2014; Revision accepted 16 December 2014; Accepted 19 December 2014 Published online 13 January 2015 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/micr.22378 Ó 2015 Wiley Periodicals, Inc.