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Diabetic sensorimotor polyneuropathy (DSPN) is the commonest form of neuropathy. Loss of sensations in sole leads to diabetic foot ulcers (DFU) and its complications. Surgical decompression has been used in the treatment of diabetic peripheral neuropathy, however; its effectiveness has been questioned.
Purpose of this study was to evaluate the sensory recovery in sole after tarsal tunnel decompression (TTD) in patients having DSPN.
Methods
Thirteen patients (Age28-70 years, average 35.57 years; 7 Males, 6 Females; 20 feet) with DSPN and positive Tinel's sign over the tarsal tunnel were included in the study. Pre and post-operative sensory tests performed on the sole included tests for touch, pain, temperature, pressure, vibration perception threshold (VPT) and two-point discrimination (2-PD). Results were classified as per British Medical Research Council (MRC) scoring system.
Results
–Sixteen feet were followed-up for 6 months. In all feet perception of touch, pain and pressure recovered. Temperature perception recovered in 75% feet. VPT came to normal range (16.81V) from 40.37 V and 2-PD came down to average of 6.0 mm from preoperative average of11.2 mm.MRC scale improved from S0 in 5 feet and S2 in 15 feet to S3+ in all 16 feet.There were no ulcers or amputation in operated limbs during follow up period of 6 months.
Conclusions
TTD improves plantar sensations in diabetic neuropathy and prevents ulcers and its related complications.
Diabetic sensorimotor polyneuropathy (DSPN) occurs most frequently in lower limbs. Insensate sole leads to diabetic foot ulcers (DFU) and its sequelae like infection, sepsis, gangrene, amputation, loss of balance leading to falls and risk of fractures and mortality.
Value of surgical decompression of compressed nerves in the lower extremity in patients with painful diabetic neuropathy: a randomized controlled trial.
The incidence of DFU is 17% in diabetics which increases every year with a rate of 2.5% per year. Even if the DFU heals, there is very high risk of recurrence, reported to be 25–35% at 1 year, 50% by 3 years, and near 100% by 10 years.
Non-healing ulcers are precursor of more than 80% of amputations in patients with DSPN. Nerve decompression (ND) has shown to have a role in DSPN for recovery of sensation and to prevent complications.
This study was conducted to evaluate the recovery of sensations in sole after tarsal tunnel decompression (TTD) in patients having DSPN.
2. Material and methods
This study was conducted over a period of two years from December 2016 to October 2018 in a tertiary referral center in Central India. Before starting the study institutional ethical committee approval and written/informed consent from patients was taken.
Seventy patients with diabetes who complained of tingling, numbness and burning pain in feet were screened in diabetic clinic and 13 patients (Age28-70 years, average 35.57 years; 7 Males, 6 Females; 20 feet) with positive Tinel's sign over the posterior tibial nerve in tarsal tunnel were selected for tarsal tunnel decompression (TTD). (Fig. 1).
Fig. 1Flowchart of Patient selection for Tarsal Tunnel Decompression.
All patients had Type II diabetes. The average duration of diabetes was 9 years (range = 5–15 years) in these patients and average duration of neuropathic symptoms was 1 year (range = 6–18 months). All 13 patients were on oral hypoglycemic agents for the control of diabetes and were shifted to insulin for peri-operative period. None of the patient presented with painful neuropathy. All patients had positive Tinel's sign over the posterior tibial nerve in tarsal tunnel and palpable pulsations in the posterior tibial artery and dorsal pedal artery.
None of the patients had presence of Tinel's sign at head of fibula or dorsum of foot and there were no sensory symptoms in the territory of common and deep peroneal nerves. Patients with a body mass index of greater than 35 kg/m2, general condition unsuitable for surgery, history of ankle fractures or amputations proximal to the tarso-metatarsal joint, gangrenous foot, osteomyelitis, positive Tinel's sign without sensory neuropathy and other causes for neuropathy were excluded from the study (Fig. 1).
X-ray of the foot was done to look for osteomyelitis, ultrasound of tarsal tunnel to rule out space occupying lesions and Arterial Doppler study of lower extremity to rule out ischemia. Sensory tests were performed on the sole in the territory of lateral plantar, medial plantar and calcaneal nerves. The sensory testing includes estimation of touch (5-0 Semmes-Weinstein monofilament), pain/pressure (blunt and sharp tip of office pin), temperature (hot water and ice cubes), 2 PD(molded paper clip) and vibration sense (Biothesiometer (BIOTHEZI-VPT by Kodys, Chennai India). For the details of sensory tests readers can refer article by Agarwal et al.
Sensory assessment was graded by British Medical Research Council (MRC) scoring system (range = S0–S4). In addition, history of previous ulcerations or any existing ulcers on sole were recorded. After undergoing all preliminary investigations, patients were taken up for tarsal tunnel release to decompress the posterior tibial nerve.
Surgery was done under spinal anaesthesia and under tourniquet control. Under loupe magnification incision began 6–8 cm proximal to the tip of medial malleolus and extended distally along the course of nerve, approximately 1–2 cm posterior to the tibia and medial malleolus. The incision was deepened flexor retinaculum exposed (Fig. 2, Fig. 3).The flexor retinaculum was divided in entire length. Distally, the retinaculum was incised to the point where the medial and lateral plantar nerves divided and followed a course deep into the plantar surface of the foot. Deep fascia of the abductor hallucis muscle and the septum between medial and lateral plantar nerves was released for complete decompression. The calcaneal branch of the nerve was identified and traced distally for a minimum of 1–2 cm posterior tibial nerve is exposed in complete length of tarsal tunnel (Fig. 4).The epineurium of posterior tibial nerve was opened in all cases and internal neurolysis was done in those cases (8 feet) where the nerve was fibrotic and encased in the scar. After achieving hemostasis wound was closed in layers (Fig. 5). Post operatively a compression dressing with a posterior Plaster of Paris slab was applied. The patient was advised to elevate the limb and was allowed walking with the support on the same day. At two weeks the stitches were removed and gentle active range of motion exercises was initiated.
Sensory recovery of sole was evaluated at 6 weeks, 3 months and 6 months postoperatively.
3. Results
Thirteen patients (20 feet) were included in the study. Flowchart of patient selection for TTD can be seen in Fig. 1. We did not have any patients of painful DSPN in this study.
Two patients had history of sole ulcer which had healed and one patient had history of great toe amputation. None of the patient had ulcer at the time of presentation. One patient died on 3rd PO day due to myocardial infarction. One patient was lost to follow-up at 3 months. Eighteen feet were available for follow-up at 6 weeks, 16 feet at 3 and6 months.
In preoperative evaluation touch was absent in 60–75% of patients in MP, LP and calcaneal territory of feet. 35–65% patients had loss of pain perception, 65–77% had loss of temperature perception and only 5–30% had loss of pressure sensation. The VPT was average 40.37 V in all patients. 2-PD was average 11.2 mm and MRC scale was S0 was in 5 feet and S2 was in 15 feet(Table 1).
Table-1Recovery of sensation after tarsal tunnel release.
At 6 week follow up 18 feet were available. Pressure perception was regained in all patients in all territory except 3 feet (16%) in calcaneal nerve territory. Touch sensation was regained in all except 5 feet (27.77%) in Lateral plantar territory and 8 feet (44.44%) in calcaneal nerve territory. Pain was regained in all except 4 feet (22.22%) in calcaneal territory. Temperature perception was present in all except7 feet (38.88%) in lateral planter nerve territory and in 13 feet (72.22%) calcaneal nerve territory.VPT improved to average 30.54V in all feet. 2-PD improved to average 8.33 mm. MRC scaleimproved toS2+ in 15 feet and S3 in 3 feet(Table 1, Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11).
At 3 month 16 feet were available for follow up. Perception of pressure recovered in all except in 2 feet (12.5%) in calcaneal nerve territory. Touch recovered in all except 1 Feet (6.25%) in Lateral plantar territory, 5 feet (31.25%) in calcaneal nerve territory. Pain recovered in all territory except 4 feet (25%) in calcaneal territory. Temperature recovered in all except in 4 feet (25%) in Lateral plantar territory and 9 feet (56.25%) in calcaneal nerve territory. VPT improved to average 23.84V and 2-PD reduced to average 8.31 mm in all feet. MRC scale improved to S2+7 feet and S3 .9 feet (Table 1, Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11).
At 6 month16 feet were available for follow-up. Perception of touch, pain and pressure recovered in all feet. Temperature perception did not recover in 1 foot in Lateral plantar territory and 4 feet (25%) in calcaneal territory. VPT returned to normal range (16.81V) and2-PD came down to average 6.0 mm.MRC scale improved from S0-5 feet and S2- 15 feet to S3+ in all 16 feet(Table 1, Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11).
There were no ulcers and amputation in operated limb during follow up period of 6 months. Complications included hyperesthesia in the medial aspect of foot in 2 patients (3 feet) and delayed wound healing in 4 patients (6 feet).
4. Discussion
There are two theories of why peripheral nerves in Diabetes get compressed when passing through a fibro-osseous tunnel like tarsal tunnel: 1) Nerve volume is increased as glucose in Diabetes is metabolized into sorbitol which leads to increased water content within the nerve and 2) Hyperglycemia and dyslipidemia, frequently associated with diabetes, lead to an excess of intra mitochondrial oxygen radical, inflammatory reactions, and edema formation in the peripheral nerves.
Diabetic control does not prevent the occurrence of diabetic neuropathy, though it reduces its incidence. Nerve compression by rigid tunnel causes a decrease in blood flow and anterograde axoplasmic flow and over a period of time leads to inflammation, scar formation. This produces demyelination histologically, and paresthesia, tingling and numbness clinically.
TTD relieves the compression of nerve and increases the blood flow and anterograde axoplasmic flow which transports the lipoproteins necessary for rebuilding the nerves.
In 1992, Dellon first proposed peripheral nerve decompression (PND) in the tarsal tunnel to treat DSPN with 85% improvement of the symptoms, normalization of Tinel's sign and nerve conduction studies.
Value of surgical decompression of compressed nerves in the lower extremity in patients with painful diabetic neuropathy: a randomized controlled trial.
DNND (Diabetic Neuropathy Nerve Decompression) study - a controlled, randomized, double-blinded, prospective study on the role of surgical decompression of lower extremity nerves for the treatment of patients with symptomatic diabetic neuropathy with chronic nerve compression.
in: 77th American Diabetes Association Scientific Sessions. 2017
Surgical peripheral nerve decompression for the treatment of painful diabetic neuropathy of the foot - a level 1 pragmatic randomized controlled trial.
have shown that nerve decompression improves sensory function of the foot in more than 80% of cases, relieves the pain, prevents formation of DFU and its subsequent complications like amputations.
Prevention of ulceration, amputation, and reduction of hospitalization: outcomes of a prospective multicenter trial of tibial neurolysis in patients with diabetic neuropathy.
But the idea of PND for DSPN has not met with widespread acceptance; mainly because of two reasons: 1) The skeptics refuse to believe in benefits of surgical treatment for a metabolic disease,
as immediate pain relief, bilateral pain relief after unilateral surgery, and large number of patients getting relief were considered too good to be true.
2) The diagnosis of DSPN is difficult to make objectively since there is no clear cut definition and symptoms are nonspecific which may occur in number of other conditions. Additionally, conventional electrophysiological tests which help in other areas are not so useful in the lower extremities, because advanced neuropathy leads to absent/reduced conduction velocity and amplitude which is not measurable thereby giving false negative findings.
A positive Tinel sign as predictor of pain relief or sensory recovery after decompression of chronic tibial nerve compression in patients with diabetic neuropathy.
A positive Tinel's sign in the tarsal tunnel is a valuable predictor of excellent result after nerve decompression (92% positive predictive value for diabetic neuropathy and 88% with idiopathic neuropathy). Thus a positive Tinel's sign at the known site of anatomic narrowing is considered enough to support the diagnosis.
If Tinel's sign is doubtful then dorsiflexion-eversion test can be performed. In this test, the ankle is passively maximally everted and dorsiflexed while all of the metatarsophalangeal joints are maximally dorsiflexed and held in this position for five to 10 s. By doing this maneuver the symptoms of tarsal tunnel syndrome get intensified and Tinel's sign becomes more pronounced.
The relief of contralateral symptoms in unilateral PND is explained by the release of immunomodulatory cytokines which get transported via blood and affect contralateral peripheral nerves and mirror image theory of pain pathway.
Patient selection is critical in successfully using TTD to obtain best results. The ideal patient for decompression of peripheral nerves is one who has symptomatic sensorimotor/autonomic neuropathy, presence of Tinel's sign at the known sites of anatomic narrowing, failed conservative treatment, sufficient circulation (palpable pulse, ankle brachial index > 0.75), and no medical contra-indications to a general or spinal anesthetic. A poor candidate for decompression of peripheral nerves is morbidly obese (>140 kg), has venous stasis/hypertension, has history of failed decompression surgery at other sites, has insufficient circulation, osteomyelitis or gangrene of fore foot.
The other causes of tarsal tunnel syndrome, and indications for TTD include trauma, varicosities, space occupying lesion (tumors/cysts/ganglion/bone spurs), tenosynovitis, flat feet and Rheumatoid Arthritis.
Causes of failure of tarsal tunnel release include an wrong diagnosis, an incomplete release, adhesive neuritis, intraneural damage, and the double crush syndrome or combination of these causes.
In our study patients 6 months after TTD recovered touch, pain and pressure sensations in all feet; temperature perception recovered in 75% patients, VPT came to normal range, 2-PD reduced significantly and MRC scale improved in all 16 feet(Table 1, Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11). There was no ulcer formation and none of the limb underwent amputation. Limitations of our study are small number of cases with limited 6 months follow-up. There was some selection bias as we did not have any patients with painful neuropathy and nerve function in terms of electrophysiology, morphology, and improvement in circulation was not assessed.
TTD is a simple operation with minimal complications, which can significantly improve sensations in the sole in selected cases of DSPN and thereby prevent further complications like DFUs and amputations. It is not difficult to recognize nerve entrapments in DSPN and PND should be incorporated in the management of DSPN. TTD/PND has the potential to improve the quality of life of patient, change the natural course of disease and as Dellon very rightly suggested, 'it is a cause for optimism in diabetic neuropathy’.
Value of surgical decompression of compressed nerves in the lower extremity in patients with painful diabetic neuropathy: a randomized controlled trial.
DNND (Diabetic Neuropathy Nerve Decompression) study - a controlled, randomized, double-blinded, prospective study on the role of surgical decompression of lower extremity nerves for the treatment of patients with symptomatic diabetic neuropathy with chronic nerve compression.
in: 77th American Diabetes Association Scientific Sessions. 2017 (San Diego (CA))
Surgical peripheral nerve decompression for the treatment of painful diabetic neuropathy of the foot - a level 1 pragmatic randomized controlled trial.
Prevention of ulceration, amputation, and reduction of hospitalization: outcomes of a prospective multicenter trial of tibial neurolysis in patients with diabetic neuropathy.
A positive Tinel sign as predictor of pain relief or sensory recovery after decompression of chronic tibial nerve compression in patients with diabetic neuropathy.
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