CHAPTER 2 Thrsal Tunnel Syndrome

Kieran T. Maban, DPM.

Tarsal tunnel syndrome is both a diagnostic and ankle. It is particularly helpful to determine therapeutic challenge. It is a diagnostic challenge whether or not the patient is prone to venous vari- because frequently it can be confused with pathol- cosities. The presence of multiple varicosities on ogy in other anatomical structures in the same the medial side of the ankle might raise the index vicinity. In addition, it is important that once a of suspicion regarding this issue. For many of these tarsal tunnel syndrome has been diagnosed, the patients, a venous occlusion test should be per- exact etiology of the syndrome must be deter- formed. A blood pressure cuff is placed around the mined wherever possible. Some patients with heel calf and inflated to 30 or 40 mm of mercury. This pain may have symptoms very similar to tarsai tun- occludes the venous return, and if the nel syndrome. Therefore, it becomes impofiant to patient's symptoms are reproduced or increased by differentiate those patients in whom the tarsal tun- this maneuveq then it is likely that there are nel syndrome is primary, versus those patients in venous varicosities that may be causing the com- whom the plantar fascitis or other heel pain syn- pression of the posterior tibial nerve. drome is primary. Similarly, approximately fifteen Muscle testing and evaluation is important in percent of patients with tibialis posterior dysfunc- order to rule out the presence of adjacent tenosyn- tion have neurologic symptoms consistent with ovitis of the tibialis posterior or long flexor tendon tarsal tunnel syndrome. Often, patients with tibialis sheath. Radiographic evaluation can also be help- posterior dysfunction can be diagnosed as having ful to rule out the presence of a coalition or other tarsal tunnel syndrome, instead of the recognition osseous masses which might be compressing the that they have a musculoskeletal dysfunction. nerye. The classic description of tarsal tunnel syn- A variety of special diagnostic tests can be drome is of an entrapment neuropathy caused by performed. Electrophysiologic studies have gener- compression of the posterior tibial nerve beneath ally been viewed as the gold standard for tarsal the flexor retinaculum. Throughout the literature, tunnel diagnosis. EMG studies seek to identify the most frequent descriptions of the clinical fea- muscle fibrillations, pafiicularly in the abductor tures are of pain around the medial malleolus hallucis muscle belly. Nerue conduction studies are radiating proximally or distally, paraesthesias, performed to identify motor and sensory latencies. dysesthesias, burning pain, and sharp stabbing The literature seems to indicate that the sensory pain. Some patients will describe more of a tight- conduction studies are more sensitive than motor ening in the vicinity of the posterior tibial nerwe. conduction studies. Nonetheless, there are many reports in the literature indicating that electrodiag- CLINICAL EXAMINATION nostic studies ate neither fully sensitive, nor entirely specific. Therefore, it should be concluded Commonly, patients with tarsal tunnel syndrome that an abnormal EMG or nelve conduction study will have their pain reproduced by percussion is not necessary in order to have a diagnosis of along the posterior tibial nelve. If paraesthesias are tarsal tunnel syndrome. Indeed, many patients who reproduced, this indicates a positive Tinel's sign. have negative electrical studies are determined not Pafiicular attention should be paid to compression to have a tarsal tunnel syndrome, and unfortu- of the nerve against the sustentaculum tali and nately are treated for other entities or not treated al compression of the medial plantar nerve beneath all. Despite the limitations of electro-diagnostic the navicular. Both of these areas tend to be studies, they are important in ruling out the pres- acutely sensitive in these patients, In addition to ence of any radiculopathy that may be mimicking evaluation of the nelve itself, it is important to eval- the tarsal tunnel syndrome. uate the surrounding mideal aspect of the foot and Takaktra et. al performed an interesting study CHAPTER 2 on fifty feet in forty-five patients with tarsal tunnel need to release the abductor fascia and abductor syndrome from 7975 to 1988. They found that the muscle belly. majority of these patients had identifiable muscu- The author's technique is to perform a culi- loskeletal pathology as the cause for the tarsal linear incision which extends from behind the tunnel syndrome. Gangha were identified in eigh- medial malleolus, following the posterior tibial teen of these feet, a bony prominence and talar nerve, and then coursing beneath the navicular. A calcaneal coalition in fifteen, a tumor in three, five Metzenbaum scissor is then used to incise the reti- feet had sustained an injury to the area, and in only naculum posterior to the tibialis posterior and nine cases was there no obvious cause. Based flexor digitorum longus tendons. The posterior tib- upon this study, it seems clear that imaging tech- ial nerve is identified proximally, and a Penrose nology plays an important role in the evaluation of drain, or vascular loop, is used to separate the patients with tarsal tunnel syndrome. Specifically, nerve from the surrounding tissue. The nerve is MRI evaluation can help to determine the presence then followed distally into the medial and lateral of any soft tissue masses, or tenosynovitis which plantar nerve branches. The calcaneal nelve may be causing the tarsal tunnel syndrome. This branches should also be identified and inspected assists the surgeon in preoperative planning. for any possible entrapment. At this point, the extent of the release TREATMENT depends to a great degree on the patient's clinical symptoms. Those patients who have pain along the Clearly, the treatment of tarsal tunnel syndrome calcaneal neryes should have an adductor release depends, lo a greal degree, on the etiology of the around the calcaneal neles. Those patients who syndrome. Those patients who have a mechanical have more inferior pain congruent with the posi- etiology for stress on the posterior tibial nerve may tion of the lateral planlar nelve should also have a respond to intensive mechanical therapy, along more aggressive dissection approach around the with a variely of symptomatic measures including abductor hallucis. Regardless of the patient's symp- nonsteriodal anti-inflammatories and steriod injec- toms, the author performs a more distal reflection tions. There is not a large body of evidence in the of the abductor muscle belly from the medial col- literature that indicates conselvative therapy is suc- umn. This frees the abductor from the medial cessful for any prolonged period of time. plantar nelve, which is particularly important in Nonetheless, if the diagnosis has been made rela- those patients who have medial plantar nerwe pain. tively early, if there is no evidence of electrical Attention is then focused back on the lateral deterioration, and if there is no evidence of a plantar nelve. Tracing the lateral plantar nere is space-occupying lesion, then mechamcal therapy somewhat more difficult due to its relationship may be worthwhile in those patients for whom with the abductor muscle belly. In some patients, it mechanics appears to be the etiology. will be necessary to incise the abductor fascia as it Surgical treatment of tarsal tunnel syndrome is lies over the lateral plantar nen/e. In revisional particularly successful when the diagnosis is made surgery patients, or in those patients who are par- early. On the other hand, revisional tarsal tunnel ticularly symptomatic in this area, it may be surgery is frequently unsuccessful, or only partially worthwhile to incise the abductor muscle be1ly in successful. The techniques used for decompression order to decompress the lateral plantar nerve. of the posterior tibial nerve have changed some- The venous structures around the posterior what over the years. The initial technique for tarsal tibial nerves are also important to mobilize and tunnel syndrome was to place a curued incision reflect. Any venous structures which cross the pos- behind the medial malleolus and release the flexor terior tibial nerye should be identified, ligated and retinaculum, following the medial and lateral plan- divided. If a varicosity is present over the posterior tar nelves distally. More recently, there has been a tibial nerve, it should be excised. much greater interest placed on a more thorough If the etiology of the tarsal tunnel syndrome is release around the medial and lateral plantar traumatic, it may be necessary to release the nerves. Lee Dellon, MD has emphasized the need epineurium in order to get adequate decompres- to release a fascial band joining the two nerve sion of the nerve. However, the author does not branches. John Kenzora, MD has emphasized the perform an epineural release on a routine basis. CHAPTER 2

The surgery is performed under tourniquet SUMMARY hemostasis. The tourniquet is released prior to clo- sure, which allows the surgeon to ensure that Tarsal tunnel syndrome should be evaluated in adequate hemostasis has been achieved. A TLS patients who present with pain along the posterior drain is also used, and the patient is placed in a tibial nerve, or pain which radiates into the heel posterior splint. region. A positive electrical study is not necessary to make the diagnosis. It is impofiant to carefully POSTOPERATIVE CARE evaluate the patient for space-occupying lesions which may be the cause of the tarsal tunnel syn- The postoperative care for tarsal tunnel syndrome drome. has traditionally been to immobilize the parient for Surgical treatment should be extremely metic- a period of three weeks. For the last several years, ulous and thorough with a full release of the the author has taken a much more aggressive laciniate ligament. Release of the abductor muscle approach towards mobilizing these patients post- belly is performed as needed in order to free the operatively. The patient is placed in a removable medial andlateral plantar nerves. Venous structures posterior splint, and after the first postoperative can also play an impofiant role in tarsal tunnel syn- visit in three to five days is instructed to begin drome and should be identified and ligated when ankle sagittal plane range of motion exercise, three necessary. to four times a day, for fifteen minutes at a time. Vhen tarsal tunnel surgery is successful, it is Once the incision is stabilized (at ten to twelve extremely gratifying to both the patient and the days), the patient is allowed to bathe the foot and surgeon. In patients with Reflex Sympathetic engage in much more aggressive range of motion Dystrophy (RSD), or additional entrapment neu- exercises. The prevention of fibrosis in this area is ropathies, the prognosis is guarded. Revisional important and can only occur when the patient is tarsal tunnel surgery is generally more fi'tistrating adequately mobilized. for the patient and the surgeon.