The Utility of the Tinel Sign in the Diagnosis of High Tarsal Tunnel Syndrome

Abstract

Background: Tarsal tunnel syndrome (TTS) can be divided into distal and proximal components. The latter is referred to as high TTS (HTTS) in which the tibial nerve is compressed above the location of the laciniate ligament. Although diagnosis of TTS has been shown to be enhanced by elicitation of a positive Tinel sign, no research into the utility of this provocation test has been conducted in the diagnosis of HTTS. This study aims to investigate the usefulness of the Tinel sign in diagnosing HTTS. Methods: Seventy patients with electrophysiologic confirmation of HTTS were evaluated for the presence of a positive Tinel sign over the posterior tibial nerve’s course in the area of the proximal tarsal tunnel (above the laciniate ligament). Results: Of the 70 patients, 17 had a positive Tinel sign. Thirty-eight patients (54.3%) had electrodiagnostic evidence of polyneuropathy, and 12 of them (31.6%) had a positive Tinel sign. Among the 26 patients with HTTS and polyneuropathy who did not have a Tinel sign, electrodiagnostic testing found severe axonal dysfunction in ten. Fifteen of the patients with polyneuropathy were diagnosed as having diabetes mellitus, and a Tinel sign was present in 11 of them (73.3%). The four diabetic patients without a Tinel sign had marked axonal dysfunction (motor evoked responses were absent or significantly reduced). Conclusions: The utility of the Tinel sign in patients with HTTS was found to be low; however, in the subpopulation of patients with diabetic neuropathy, the Tinel sign may be more useful.

The Tinel sign, also known as the Hoffman-Tinel sign, was recognized in 1915, first by Paul Hoffman and, independently, by Jules Tinel a few months later.[1,2] The sign is positive when a distal paresthesia—a sensation of tingling or “pins and needles”—is experienced by the patient when the practitioner gently taps (percusses) on a peripheral nerve.[3]

The Hoffmann-Tinel sign is considered the most accurate nomenclature, although typically the sign (or test) is referred to as the Tinel sign.[1,2,4,5] The predominance of this term may be because Tinel contributed more broadly to medical knowledge. He wrote and published several hundred articles in scientific publications.[4] Moreover, his description of the sign was more detailed than that of Hoffman.[5,6] Tinel, unlike Hoffman, stressed the separation of pain and paresthesia, stating that “[p]ain is a sign of irritation of the nerve; tingling is a sign of regeneration, or more precisely, tingling reveals the presence of regenerating axons.”[6] ^(p388) Tinel further found that if tingling did not progress, surgery was warranted to restore normal function. In addition, he also correctly predicted that the phenomenon referred to regeneration of not only sensory nerves but also motor nerves.[5]

The value of the Tinel sign came to be more fully appreciated in 1946, when it was determined that nerve regeneration is not concomitant with paresthesia alone. It was found to occur when the evoked paresthesia progresses distally across the location of the lesion.[2,7] The sign has emerged to indicate compression or regeneration of a particular peripheral nerve.[1,3] Although its utility has been questioned,[8] research has found the test’s use to be valid to varying degrees in assisting with the diagnosis of a variety of peripheral nerve conditions, including carpal tunnel syndrome, cubital tunnel syndrome, peroneal (fibular) nerve entrapment, deep peroneal nerve entrapment, superficial peroneal nerve entrapment, tarsal tunnel syndrome (TTS), and other peripheral nerve injuries.[9,10,11,12,13,14,15,16,17,18]

In TTS, a positive Tinel sign has been demonstrated to be a valid measure of tibial nerve abnormality[16] and a predictor of pain relief and improved plantar sensation in those with diabetic neuropathy who undergo nerve decompression at the tarsal tunnel.[19] Generally, TTS is entrapment of the posterior tibial nerve as it passes under the laciniate ligament at the foot/ankle junction, or compression of the calcaneal, medial, and plantar nerves of the foot as they pass under the abductor hallucis muscle.[16,17,20,21,22] More specifically, TTS has been described as having a distal component, referred to as distal TTS,[23] and a more proximal entrapment site, referred to as high TTS (HTTS).[24,25,26]

Originally HTTS was described by Baxter[26] in 1995, then by Baxter and Schon[24] and Kennedy and Baxter[25] in 2008, and finally by Segura[27] 2 years later. More recently, Segura and Nirenberg[28,29] described this condition. The authors described it as entrapment by fascia at the level of the lower fibers of the gastrocnemius muscle.[26,28,29]

Symptoms of HTTS are similar to those of TTS: individuals are said to experience pain or an abnormal sensation or numbness on the bottom of their foot and/or into their toes. Patients may relate burning, tingling, shooting, cramping pain, or numbness.[24,25,26,28] Clinically, in long-standing cases, the small muscles of the foot may atrophy, which may result in the development of digital deformities, such as hammertoe.[17,30,31,32]

To recognize patients with HTTS, researchers rely on each patient’s history and the physician’s clinical examination, which may include testing for a Tinel sign.[28] The physician will check for a Tinel sign along the course of the posterior tibial nerve at the lower leg, ankle, and foot.[33] Other examination findings may include a provocation sign, in which moderate pressure applied to the site of entrapment elicits discomfort or withdrawal from the patient,[34] or a positive provocation test, such as the dorsiflexion-eversion test, the plantarflexion-inversion test, or the triple compression stress test.[23,25,30,35,36,37,38]

In diagnosing HTTS, diagnostic tests have been found to be adjunctive. Such tests include diagnostic nerve blocks, magnetic resonance imaging, radiographs, diagnostic ultrasound, and both electromyography and nerve conduction studies, together referred to as electrodiagnostic (EDX) testing.[31,39,40,41,42]

In the evaluation of nerve entrapments, including compression of the posterior tibial nerve, EDX testing can be applied in a conventional manner or with an “inching” technique.[43,44,45,46,47] The term inching refers to the stimulation of the nerve in short segments, which yields a more precise localization of focal slowing.[48,49,50] Originally, the technique was used in the upper extremity,[51,52] and it was first used for TTS in 1992.[47] The use of inching to determine an entrapment of the posterior tibial nerve above the laciniate ligament, known as HTTS, was noted by Segura[27] in 2010. As a result, this entrapment point has been referred to as Segura’s area.[53]

The usefulness of the Tinel sign in assisting with the diagnosis of HTTS has not been investigated. This study examined the diagnostic utility of the Tinel sign in assisting with HTTS diagnosis, which was identified clinically and confirmed with EDX testing that used an inching technique.

Methods

This study involved a retrospective review of the medical records of 70 patients who had HTTS confirmed with EDX testing. The inclusion criteria were patients with a clinical suspicion of TTS as determined by a podiatric physician who was a Fellow of the Association of Extremity Nerve Surgeons (M.S.N.). The study complied with the Helsinki Declaration of 1975 and its amendments. Institutional board review approval was not required because the study was within Exempt Category 4, as defined by the US Department of Health and Human Services’ Office of Human Research Protections. Furthermore, patient data existed before initiation of the study, and patient identifying information was anonymized.

Patients ranged in age from 15 to 90 years, with a mean age of 64 years. Forty-one patients were male and 29 were female. The podiatric medical examination determined that all of the patients had adequate circulation, and none had open wounds or infection, were pregnant, or had a history of surgery in the area of the tarsal tunnel or complex regional pain syndrome. Because the identification of a Tinel sign relies on feedback from the patient, individuals who lacked the mental faculty to provide this feedback were excluded from the study.

Before EDX testing, the patient was assessed for a Tinel sign by a clinical neurophysiologist who evaluated the posterior tibial nerve in the area of HTTS. Patients who related feeling an electric-like, pins or needles, or tingling sensation radiating distally from the site being evaluated were considered to have a Tinel sign. Those who did not have such sensation or voiced uncertainty were deemed to not have had a Tinel sign.

After this determination, the neurophysiologist performed EDX testing on each patient’s lower extremities. Initially, conventional EDX testing was completed, which entailed a motor conduction evaluation on the tibial and common peroneal nerves, along with sensory conduction studies on the sural, superficial peroneal, medial plantar, and lateral plantar nerves. This testing included a determination of latencies, amplitudes, and distances, which were compared against the contralateral limb. For intersegmental conduction velocities, a lower limit of 40 m/sec was considered normal.[46] To eliminate proximal pathology, needle electromyography was also performed.

Next, the tibial nerve in the lower leg and ankle area was evaluated with an inching technique with the tibial nerve stimulated at 2-cm intervals. The posterior tibial nerve was stimulated along its course 10, 12, 14, and 16 cm from the abductor hallucis muscle. (This EDX testing of the tibial nerve has previously been documented.[27,28,29,46])

Results

This investigation consisted of a medical record review of 70 patients with HTTS confirmed by EDX testing. Seventeen patients (24.3%) had a Tinel sign at the level of HTTS.

Of the 70 patients with HTTS, 38 (54.3%) also had EDX evidence of polyneuropathy. Of these 38 patients, 12 (31.6%) had a positive Tinel sign. Among the 26 patients with HTTS and polyneuropathy who did not have a Tinel sign, EDX testing found severe axonal dysfunction in ten. Fifteen of the patients with polyneuropathy were diagnosed as having diabetes mellitus, and a Tinel sign was present in 11 of them (73.3%). The four diabetic patients without a Tinel sign had marked axonal dysfunction (motor evoked responses were absent or significantly reduced).

Discussion

The results of this study demonstrate the absence of a Tinel sign in most patients (75.7%) with HTTS, suggesting that its utility in the diagnosis of HTTS is low. However, in the subset of patients who were diabetic, the inverse occurred: nearly three-quarters of the patients (73.3%) had a positive Tinel sign.

Rinkel et al[16] found that entrapment of the posterior tibial nerve at the tarsal tunnel can be validly assessed by the presence of a Tinel sign. They found it “highly” prevalent but more so in diabetic patients. The study relied on the presence of neuropathic complaints and the use of a screening instrument rather than EDX testing. Researcher A. Lee Dellon has co-authored several publications that propose that a Tinel sign at the tarsal tunnel is an excellent predictor that decompression of the tibial nerve will be successful.[15,19,54,55] This research used postsurgical results rather than EDX testing. However, in using EDX testing to confirm nerve entrapment, Datema et al[8] found that the Tinel sign was not a reliable test.

Citing the acceptance of the Tinel sign in identifying a site of nerve compression of a peripheral nerve and his experience, Dellon believes that a Tinel sign is sufficient to localize compression in the tarsal tunnel.[56] Dellon[56] and Dellon et al[19] also cite research showing a pathologic foundation for a Tinel sign to identify a site of nerve compression. In brief, the Tinel sign becomes positive only once demyelination of the nerve begins (inducing axonal sprouting), and the sign ceases to occur with advanced axonal loss. This process has been established in experimental models of nerve compression on rats and monkeys,[19] as well as in histopathologic examinations of human specimens in TTS.[57] It is this segmental nerve demyelinization and axonal loss in persons with diabetic neuropathy that Rinkel et al[16] found makes nerve entrapment difficult to diagnose with EDX testing.

The present study is most similar to the study by Datema et al,[8] which used EDX testing; however, in this regard, there is no documentation that they used an inching technique as was performed with the patients in the present study. The results of this analysis suggest that a positive Tinel sign may have more utility in evaluation of HTTS in patients with diabetic polyneuropathy. As such, the lack of a Tinel sign in itself cannot rule out the presence of HTTS.

The technique of administering the Tinel test has been shown to vary between physicians.[58] This factor may introduce erroneous results. Interestingly, this research found that there is little variance in the percussing of the nerve by an individual examiner.

Regardless of the presence of a Tinel sign, we found that in patients with HTTS, pain was elicited when pressure (or deep palpation) was applied over the area where EDX studies detected focal compression. We also noticed a lack of a Tinel sign in persons with HTTS who had a larger calf size, suggesting that the increased tissue prevented its stimulation. The absence of a Tinel sign in other persons with HTTS could stem from the posterior nerve coursing deeper, more centrally, in the leg or due to variations in the soleus muscle and its fascia. These possibilities are avenues for further study.

Future research may also consider a larger sample size with broader patient demographics; the consideration of other patient issues, such as biomechanics, weight (body mass index), and the presence of other medical issues; and additional studies to explore further improvement and standardization of the Tinel test.

Conclusions

The Tinel test is commonly used in assisting with the diagnosis of nerve problems and has value as a prognostic indicator of surgical success in some circumstances. Although the utility of the Tinel sign in patients with HTTS was found to be low, the findings suggest that in the subpopulation of patients with diabetic neuropathy, the Tinel sign may be more useful. We hope that this research stimulates further investigation into HTTS, including analysis of current provocation signs and development of clinical techniques to recognize its presence.