Re: Tarsal tunnel syndrome caused by epineural ganglion of the posterior tibial nerve

Tarsal tunnel syndrome secondary to accessory or variant muscles: a clinical and anatomical systematic review

PURPOSE

Many etiologies are known to lead to a tarsal tunnel syndrome (TTS). One rare cause is mass-occupying lesions, and particularly accessory or variant muscles (AVM). This study aimed to systematically collect published clinical cases of TTS caused by AVM.

METHODS

An electronic literature search was conducted from inception to April 2021. The diagnosis of AVM should be reported in one of the following methods: ultrasonography, magnetic resonance imaging (MRI), or per-operatively. Data extraction included types and prevalence of accessory muscles, clinical presentation and diagnosis, and treatment modalities. Twenty-five studies were identified with a total 39 patients (47 ankles).

RESULTS

The prevalence of TTS was reported in only two studies (9%). Forty-nine AVM were identified with the accessory flexor digitorum longus being the most common (52%). The most common sign/symptoms were tenderness (78.7%), pain (82.9%), dysesthesia (57.4%), Tinel sign (44.6%), and a swelling (25.5%). Decompression and excision were the most commonly performed procedures. Four accessory/variant muscles in the ankle have the potential to induce a tarsal tunnel syndrome.

CONCLUSION

This review highlights the clinical and imagery specificities of TTS secondary to accessory or variant muscles. Mass-occupying etiology should be included in the list of differential diagnoses whenever a posterior tibial nerve compression is suspected.

Atypical musculoskeletal manifestations on flexor hallucis longus tendon of gout causing tarsal tunnel syndrome in diabetic patients: A case report

RATIONALE

Deposition of tophus is a common feature in chronic gout; however, signs and symptoms are not always well-pronounced in cases of uncommon sites. We report a rare case with a tophaceous tendonitis on the flexor hallucis longus (FHL) tendon with tarsal tunnel syndrome (TTS). This is the first surgical case of TTS by gouty tophi in FHL.

PATIENT CONCERNS

A 55-year-old woman presented with a 6-month history of mild discomfort at the right foot, which gradually worsened in the past 3 weeks. The patient visited our outpatient clinic due to persistent and aggravating foot pain and swelling around the tarsal tunnel.

DIAGNOSIS

The patient was diagnosed with hyperuricemia and diabetes mellitus with chronic kidney disease, and did not receive regular antigout treatments. Paresthesia was found along the distribution of medial and plantar nerve and tinel test was positive on tarsal tunnel. Biochemical examination showed she had raised serum uric acid (10.6 mg/dL) and decreased estimated glomerular filtration rate (69 mL/min/1.73 m). Conventional radiography examination showed negative pathology except soft tissue swelling. Magnetic resonance imaging revealed a fusiform mass within the FHL tendon and fluid collection around tarsal tunnel.

INTERVENTIONS

Surgical exploration was performed to remove the mass. Inflammation fluid exploded out from FHL tendon sheath, which was later proven to have infiltration of monosodium urate crystal. Superficial dissection revealed a white chalky mass and posterior tibial nerve was significantly compressed by the tophus mass.

OUTCOMES

The mass was removed and the symptoms were relieved at immediate postoperative period.

LESSONS

A tophaceous tendonitis on FHL tendon can cause TTS and surgical decompression of the gout lesion can reduce the symptoms.

Degenerative subtalar joints complicated by medial plantar intraneural cysts : cutting the cystic articular branch prevents recurrence

AIMS

The pathogenesis of intraneural ganglion cysts is controversial. Recent reports in the literature described medial plantar intraneural ganglion cysts (mIGC) with articular branches to subtalar joints. The aim of the current study was to provide further support for the principles underlying the articular theory, and to explain the successes and failures of treatment of mICGs.

PATIENTS AND METHODS

Between 2006 and 2017, five patients with five mICGs were retrospectively reviewed. There were five men with a mean age of 50.2 years (33 to 68) and a mean follow-up of 3.8 years (0.8 to 6). Case history, physical examination, imaging, and intraoperative findings were reviewed. The outcomes of interest were ultrasound and/or MRI features of mICG, as well as the clinical outcomes.

RESULTS

The five intraneural cysts followed the principles of the unifying articular theory. Connection to the posterior subtalar joint (pSTJ) was identified or suspected in four patients. Re-evaluation of preoperative MRI demonstrated a degenerative pSTJ and denervation changes in the abductor hallucis in all patients. Cyst excision with resection of the articular branch (four), cyst incision and drainage (one), and percutaneous aspiration/steroid injection (two) were performed. Removing the connection to the pSTJ prevented recurrence of mIGC, whereas medial plantar nerves remained cystic and symptomatic when resection of the communicating articular branch was not performed.

CONCLUSION

Our findings support a standardized treatment algorithm for mIGC in the presence of degenerative disease at the pSTJ. By understanding the pathoanatomic mechanism for every cyst, we can improve treatment that must address the articular branch to avoid the recurrence of intraneural ganglion cysts, as well as the degenerative pSTJ to avoid extraneural cyst formation or recurrence. Cite this article: Bone Joint J 2018;100-B:183-9.

The mechanism underlying combined medial and lateral plantar and tibial intraneural ganglia in the tarsal tunnel

Intraneural ganglion cysts in the tarsal tunnel are rare. We present a patient who had an intraneural ganglion cyst involving the medial and lateral plantar and distal tibial nerves. Magnetic resonance imaging revealed evidence to support the joint-related (i.e., subtalar) origin of the cyst. Careful reinterpretation of the imaging supported a phasic mechanism (i.e., cross-over) to explain the interrelated pathogenesis of the intraneural cyst within the three nerves. This mechanism is analogous to that described for the prototypes-the peroneal, tibial and sciatic nerves in the knee region-and can be generalized to other nerves in the foot and ankle region. We believe that understanding the pathogenesis sheds light on the effective treatment.

Tarsal tunnel syndrome and flexor hallucis longus tendon hypertrophy

Tarsal tunnel syndrome (TTS) defines an entrapment neuropathy of the posterior tibial nerve or one of its branches, within the tarsal tunnel. Numerous etiologies have been described explaining this entrapment, including trauma, space-occupying lesions, foot deformities, etc. We present an unreported cause of a space-occupying lesion in the etiology of TTS, namely the combination of a hypertrophic long distally extended muscle belly of the flexor hallucis longus and repetitive ankle motion. Surgical debulking of the muscle belly in the posterior ankle compartment resolved all symptoms.

THE UNIFYING ARTICULAR (SYNOVIAL) ORIGIN OF INTRANEURAL GANGLIA

THE PATHOGENESIS OF intraneural ganglia has been an issue of curiosity, controversy, and contention for 200 years. Three major theories have been proposed to explain their existence, namely, 1) degenerative, 2) synovial (articular), and 3) tumoral theories, each of which only partially explains the observations made by a number of investigators. As a result, differing operative strategies have been described; these generally meet with incomplete neurological recoveries and high rates of recurrence. Recent advances in magnetic resonance imaging and critical analysis of the literature have clarified the mechanisms underlying the formation and propagation of these cysts, thereby confirming the unifying articular (synovial) theory. By identifying the shared features of the typical cases and explaining atypical examples or clinical outliers, several fundamental principles have been described. These include: 1) a joint origin; 2) dissection of fluid from that joint along an articular nerve branch, extension occurring via a path of least resistance; and 3) cyst size, extent, and directionality being influenced by pressures and pressure fluxes. We believe that understanding the pathogenesis of these cysts will be reflected in optimal surgical approaches, improved outcomes, and decreased frequency, if not elimination, of recurrences. This article describes the ongoing process of critically analyzing and challenging previous observations and evidence in an effort to prove a concept and a theory.

Tibial intraneural ganglia in the tarsal tunnel: Is there a joint connection?

Intraneural ganglia are rare entities, and, as such, their pathogenesis has been extremely controversial. Recent evidence from intraneural ganglia occurring at more proximal sites-the peroneal nerve at the fibular neck (the most common site) and the tibial nerve at the knee-has suggested an articular origin rather than de novo formation. To our knowledge, of the 10 previous reports of tibial intraneural ganglia within the tarsal tunnel by others, a joint connection to the ankle joint was only identified in 2 cases. To support a hypothesis that tibial intraneural ganglia occurring within the tarsal tunnel region arise from neighboring joints, we analyzed 3 patients retrospectively, all of whom had magnetic resonance (MR) imaging and operative intervention. One of these patients was treated by a peripheral nerve surgeon specializing in foot and ankle surgery. The other 2 patients were the only ones previously published in the literature who had MR images available for reinterpretation. In none of these cases was a joint communication appreciated by radiologists interpreting the MR images preoperatively or by surgeons intraoperatively. Our review of these same cases demonstrated radiographic evidence of joint communications with the subtalar joints. Based on our findings in this article and our knowledge of intraneural ganglia occurring at more proximal sites, we believe that tibial intraneural ganglia within the tarsal tunnel originate from neighboring joints and that their connections to the joints (pedicles) are through articular branches. The importance of these connections is 2-fold: first, for their role in the pathogenesis of this entity, and second, for their potential therapeutic implications. As is highlighted by the clinical and radiographic follow-up in the 1 patient in this article and in many previously reported at other sites, intraneural cyst recurrence can occur if surgeons do not specifically address the articular connection.