Stuart D. Miller and Venus R. Rivera
DEFINITION
Adhesive neuritis describes the pain from a nerve scarred to surrounding tissues. A common cause for such a condition in the lower extremity occurs after a tarsal tunnel release with subsequent scarring. While many nerves can be involved, the frequency of posterior tibial nerve involvement overwhelms that of other reported nerves and thus will be the primary focus of this chapter.
ANATOMY
Adhesive neuritis can affect any nerve in the lower extremity. Lower extremity nerve anatomy involves the posterior tibial nerve, the superficial peroneal nerve, the sural nerve, the deep peroneal nerve, and the saphenous nerve, and distal branches of these nerves. The most common site of adhesive neuritis anecdotally seems to be the posterior tibial nerve, a continuation of the sciatic nerve, which courses along the medial leg in a discrete retinacular anatomic tunnel with the posterior tibial artery and vein. Around the medial malleolus, the nerve splits into the medial and lateral plantar nerves. The lancinate ligament obliquely crosses at this level and can cause tarsal tunnel compression. The calcaneal branches (usually one or two) split from the main nerve trunk or occasionally from the lateral plantar nerve alone and can be constricted in the medial soft tissues. More distally, the nerves run under the abductor hallucis muscle, which has a very thick lateral fascial covering. This fascia can be thickened and can become a major source of mechanical compression of the nerve.
The superficial peroneal nerve runs in the anterolateral aspect of the leg, often in its own sheath, between the anterior intermuscular septum and lateral muscle compartment fascia. This nerve can be constricted at several points, but by far the most common area is above the level of the ankle joint, where it emerges from the deep fascia of the peroneal muscle. The nerve becomes subcutaneous distal to this region, usually splitting into two main branches. The nerve demonstrates a wide variation in its anatomic course in this region. Prior surgery or injury to this area can cause adhesive neuritis, from the posterior aspect of the fibula to the anterolateral portal for arthroscopy.
The sural nerve can often be enveloped by scar tissue in the lateral aspect of the foot as a complication of surgery on the posterior calcaneus (Haglund deformity), on the calcaneus for fracture, for peroneal tendinitis, or for triple arthrodesis. The nerve also is at risk with surgery on the base of the fifth metatarsal as it drapes over the bone.
The deep peroneal nerve lies along the anterolateral border of the tibia as it approaches the ankle between the extensor digitorum longus and the tibialis anterior muscles. This nerve has a muscle branch to the extensor digitorum brevis and may also send branches to the sinus tarsi before innervating the first web space distally. The deep peroneal nerve can become pinched at the anterior ankle retinaculum as well as scarred down over the dorsum of the foot at the cuneiforms. In addition to repetitive trauma, which can cause soft tissue inflammation and scar formation, the nerve is at risk from arthritic irritation and osteophyte formation, as well as from cyst encroachment.
The saphenous nerve travels with the saphenous vein anteromedially. This superficial nerve is at risk with open reduction and internal fixation of the ankle joint and with any medial surgery, such as triple arthrodesis or arthroscopy.
PATHOGENESIS
Adhesive neuritis may occur after insult to the nerve or neighboring tissues resulting in adhesion between the nerve and surrounding tissue. The local damage usually comes from mechanical irritation and scar, such as surgery or soft tissue damage. While any nerve can be affected, each nerve is at higher risk where it naturally rounds a bend or courses under a retinaculum. The scar tissue then prevents movement of the nerve along with normal range of motion of the foot or ankle, thus the designation adhesive neuritis.
The most common cause of such a condition to the posterior tibial nerve would be after tarsal tunnel release. Other trauma, such as a severe contusion or stretch, surgery on adjacent tendons, or resection of tumor or cyst, can cause adhesions with healing.
Other nerves, such as the superficial peroneal nerve, are at risk due to surgery as well, especially due to arthroscopic portals and after open reduction of lateral malleolus fracture. The saphenous nerve is at risk from open reduction of medial malleolus fractures as well. Sural nerves are at risk with open reduction of calcaneus fracture, with repair of the Achilles tendon, with triple arthrodesis, and with insertional Achilles tendinitis as well as resection of Haglund deformity.
While the essential pathophysiology has yet to be defined, the end result is scar and fibrinous tissue adhering to the nerve epineurium. This scar can impede nerve conduction due to physical impingement. The infiltrative scarring can also directly affect nerve function and vascularity. The mechanical pull on the nerve can be irritating and limit conduction, particularly in extreme limb positions. The surgical guidance for simple nerve release versus epineurolysis has not been well delineated and remains at the surgeon's judgment.
NATURAL HISTORY
The typical scenario of adhesive neuralgia is an initially good result after surgery with subsequent scarring and progressive nerve irritation. While a mild problem may ease with motion and tearing of the restricting tissues, the neuralgic pain often does not ease markedly with time, and often slowly worsens.
After tarsal tunnel release, neuritis might be a recurrence of nerve pain 2 to 4 months after the original surgery. The pain is often related to activity and foot position. Extremes of inversion or eversion put more mechanical strain on the posterior tibial nerve and strain the adhesions to the soft tissue, causing nerve pain. The nerve does seem to be at higher risk with more proximal nerve compression, such as a radiculopathy, represented by the term “double crush” syndrome.
PATIENT HISTORY AND PHYSICAL FINDINGS
The patient with adhesive neuralgia will typically provide an event leading to the nerve issues. Prior surgery is a common trigger and the physician must determine whether the neuralgia is secondary to scarring or due to failure of the surgery to resolve the initial problem (ie, inadequate tarsal tunnel release). Prior medical history is essential; patients with diabetes or other metabolic insults to the nervous system should be fully evaluated and systemic neuropathy differentiated from local symptoms. The patient with any sciatica or symptoms extending proximally to the posterior thigh should be tested with electromyography and nerve conduction studies—not necessarily to diagnose the adhesive neuralgia as much as to rule out and possibly treat proximal causes of nerve pain.
Physical examination must be taken in context of the extremity examination. A general leg examination sitting and standing is important, as varus or valgus angulation can cause many problems. Gait abnormalities may also be reflected in medial pain. A simple check for dorsal pedal pulses and toe capillary refill can find vascular insufficiency. Various joint issues such as synovitis or arthritis can contribute to nerve irritation, as could a palpable mass such as a ganglion cyst or neurilemmoma. Direct percussion can cause pain and pinpoint the location of impingement.
Palpation of the posterior tibial nerve can often elicit pain at the area of the lancinate ligament and sometimes at the abductor fascia. Some surgeons have noted increased sensitivity of the nerve when the foot is passively placed in the dorsiflexed and everted position. Distal neural examination may map out a pattern of medial or lateral plantar nerve altered sensation or may demonstrate global peripheral neuropathy, sometimes with motor weakness. The irritation of the nerve to motion of the extremity is the hallmark of adhesive capsulitis and is a good prognostic sign for surgical intervention.
IMAGING AND OTHER DIAGNOSTIC STUDIES
No radiologic studies are confirmatory for this condition. Indeed, most studies help in ruling out other causes for the pain.
Plain radiographs are important to rule out other sources of lower extremity pain, such as fracture, severe malalignment, coalition, arthritis, or bone cysts.
MRI may discern an underlying mechanical insult to the nerve, such as tendinitis, ganglion cyst, or tumor (FIG 1).
Ultrasonography plays a similar role as MRI but involves a great deal of interpretation.
An electromyelogram and nerve conduction studies help to rule out a systemic neuropathy or more proximal lumbosacral pathology.
The test may not always be confirmatory for significant tarsal tunnel nerve compression and often lacks the specificity for other peripheral nerves, but the exclusion of more proximal pathology is important.
FIG 1 • MRI of cyst formation along the tibial nerve.
DIFFERENTIAL DIAGNOSIS
Intrinsic nerve damage, crush injury
Systemic neuropathy
Diabetic neuropathy
Leprosy
Peripheral vascular disease
Posterior tibial tendinitis
Rheumatoid arthritis
Ganglion cyst
Lipoma
Neurilemmoma
Giant cell tumor of the tendon sheath
Abscess or infection
Spinal or nerve root pathology
Fracture
Malalignment (varus or valgus foot or ankle)
Tarsal coalition
Plantar fasciitis
NONOPERATIVE MANAGEMENT
Tarsal tunnel syndrome, especially with adhesive neuritis, can often be mechanically exacerbated and a trial of immobilization is usually warranted. While a cast provides the best hold, a walker boot is much more practical, especially if some relief ensues. Many patients will begin walking postoperatively in a walker boot; thus, the investment can be worthwhile even if surgery later occurs.
Pharmacologic management continues to develop, with anticonvulsants such as pregabalin or gabapentin augmenting the use of tricyclic antidepressants such as amitriptyline. Clonazepam and similar benzodiazepines also seem to help peripheral nerve irritation. Due to the complexity of these medications, referral to a pain management specialist often helps in patient care. Systemic anti-inflammatories can also help with pain control, especially when the nerve irritation is worsened by an arthritic or synovitic condition.
Topical anesthetic creams can help with peripheral nerve irritation, especially with nerves close to the skin surface such as the sural or superficial peroneal nerves. Lidocaine can help either in a local pad or a gel. Other medications in a topical gel can be absorbed through the skin, such as ketamine or anti-inflammatories. Some patients respond well to capsaicin pepper cream, which raises the “background noise” about the nerve.
SURGICAL MANAGEMENT
Preoperative Planning
The surgery should be respected as a revision nerve procedure, with attendant greater risk for intrinsic nerve damage, accompanying vessel damage, and time-consuming difficulty. A careful preoperative discussion regarding indications, risks, and expectations should be mandatory.
Loupe or microscopic magnification can be very helpful. A 2.0× magnification has proven adequate for most cases.
A microsurgical set of tools should be available, along with finer sutures, such as 8-0 nylon or Prolene, for repair of vascular structures. Sometimes a small branch will rip off the artery, and a simple suture of that resulting hole will control bleeding without arterial sacrifice. Documenting a good dorsal pedal pulse before surgery would greatly ease fears of vascular compromise to the foot. When in doubt (and especially when the dorsal pedal pulse is not palpable), a preoperative vascular consultation may prove fruitful.
A set of bipolar forceps can ease some of the dissection difficulty.
These procedures can be markedly variable in difficulty and duration. Some cases will “unzip” easily and allow easy nerve exposure while others may take several hours of meticulous dissection to uncover the nerve. Surgeons must allow adequate time to perform these operations, perhaps overbooking the time allotment to avoid rushing through a tough dissection.
Positioning
Patients should be supine, perhaps on a bean bag positioner or a bump under the contralateral hip to allow easy access to the medial aspect of the foot. These surgical procedures can be long and appropriate padding to the bony prominences should be noted.
A tourniquet is very helpful for control of vigorous bleeding, but its routine application is discouraged; we apply a tourniquet but rarely inflate the device. The dissection often proceeds more easily if the vessels remain full, thus being easily discerned against the nerve in a scar situation.
A table that elevates and tilts is helpful for establishing a Trendelenburg position and lessening the blood flow to the limb.
Approach
The surgical approach to the revision tarsal tunnel is usually along the same lines as the original incision with extension both proximally and distally. When in doubt, an extensile exposure seems ideal, following the line of neurovascular bundles. Often, the initial incision will cause difficulty with distal direction plantar as it included a plantar fascia release. For these occasions, especially when the bulk of symptoms are at the medial plantar nerve entrapment by the abductor fascia, the revision incision must curve anteriorly and at an angle to the original cut. The skin seems well vascularized here and sharp angles rarely have healing problems.
The approach to the lesser peripheral nerves in the foot and leg usually follows anatomic guidelines. The superficial peroneal nerve can be compressed and adhesive to the peroneal muscle fascia at the supramalleolar level of the leg. The nerve here often runs in its own separate sheath and must be directly visualized to ensure complete release. Very little information has been presented regarding barrier procedures for these more purely sensory nerves.
TECHNIQUES
REVISION NERVE RELEASE
The revision nerve release remains the crucial and most difficult part of these procedures. The amount of scar tissue formation varies widely and dictates the pace of the surgery. Starting more proximally in “virgin” tissue seems wise as distal dissection proceeds more easily when the nerve and vessels have been identified. The initial skin incision should be superficial, especially distally when the nerve moves more medial and superficial by the lancinate ligament. Deep dissection with dissection scissors and simple blunt clearing of tissue allows the visualization of the fascia overlying the flexor digitorum longus tendon and then the tarsal tunnel. A band of yellow fat often marks the location of the tarsal tunnel under fascia.
TECH FIG 1 • Dissection of the tarsal tunnel is facilitated by the bipolar forceps.
Incise the fascia and isolate the nerve. Take care to cauterize small bleeding vessels; this is often made easier with use of the bipolar forceps (TECH FIG 1). The posterior tibial nerve will have a venous plexus around it, which can be stripped off with some bleeding. The larger vessels will send small branches by the nerve, and these may need cauterization or ligation depending on size.
Separate the nerve from the artery and veins with care. Do not inflate the tourniquet unless severe bleeding occurs, as the vessels are more easily identified when full (TECH FIG 2). Persistent or vigorous bleeding can often be controlled with local pressure distally, but the tourniquet is sometimes needed to better dissect and cauterize the difficult venous plexus around the medial plantar nerve. Vessel loops aid with retraction of the vessels and for movement of the nerves without damage.
The decision to perform epineurolysis depends on the clinical findings and on the dissected status of the nerve: grossly scarred nerves that then appear healthy after neurolysis probably do not warrant more extensive incision of the epineurium, but no conclusive studies are available to help in this decision.
The dissection must include the region above the ankle joint, and dissection proceeds distally beyond the abductor fascia. The abductor can be very thick and restrictive to the nerve (TECH FIG 3). The soft tissues should yield easily to a small hemostat sliding along the nerve, ensuring release.
TECH FIG 2 • Wrapping with NeuraWrap. Note the intact vasculature, as the procedure is usually performed without inflation of the tourniquet.
TECH FIG 3 • Typical scarring of the medial plantar nerve as it courses under the abductor fascia.
VEIN WRAP PROCEDURE
The saphenous vein can be harvested by standard fashion (when in doubt, consult with cardiovascular surgical technicians, who harvest these veins daily), either by skip incisions or one long incision (TECH FIG 4).
Tie off small side branch vessels to allow later expansion of the vessel.
Once the maximal length is harvested, to the knee region, the vein is prepared.
Mark the outer lining of the vessel with a marking pen (TECH FIG 5).
Tie off the end of the nerve and any branches.
Tie the vein ending around a bulb-tipped needle.
Fill and then distend the vein with a Marcaine and saline solution (TECH FIG 6).
Cut the vein longitudinally.
TECH FIG 4 • Extensive incision to see the tarsal tunnel and the saphenous vein dissection.
TECH FIG 5 • Labeling vein to later identify outside layer.
TECH FIG 6 • Distending saphenous vein graft with bupivacaine and saline.
TECH FIG 7 • Vein being brought around the tibial nerve. Each throw is secured with 7-0 suture.
TECH FIG 8 • Vein wrapping in place.
Begin wrapping the nerve with the vein, inner lumen to the nerve.
Secure each turn with a simple suture of 7-0 Vicryl (TECH FIG 7).
Once complete, put the foot and ankle through a full range of motion to ensure there is no binding (TECH FIG 8).
Close the subcutaneous tissues with a 3-0 or 4-0 resorbable suture.
Close the skin with 4-0 Monocryl suture.
Place a bulky cotton wrap around the leg with a medial lateral U-splint and a posterior L-splint of plaster, covered with Coban or elastic wrapping.
NEURAWRAP APPLICATION PROCEDURE
Once the nerve is exposed and free, the various sizes of NeuraWrap are selected. Each segment should be slightly larger than the portion of nerve being wrapped.
The NeuraWrap sections should be soaked in saline for 5 minutes.
TECH FIG 9 • The NeuraWrap processed bovine collagen tube retains a convenient shape.
Each section is simply wrapped around the nerve without tension. The material has a shape memory to be a tube (TECH FIG 9), and no suture is needed.
Separate sections of NeuraWrap can be applied to each side branch.
A branch can also be resected by cutting a small rectangular section of the NeuraWrap around the larger nerve to allow the branch to exit unimpeded.
Most posterior tibial nerve segments require one or two 7 × 4-mm sections of NeuraWrap.
Most medial or lateral plantar nerves require a 5 × 4-mm section of NeuraWrap (Tech Fig 2).
Occasionally the calcaneal branch or the first branch of the lateral plantar nerve will be wrapped. These usually require a 3 × 4-mm section of NeuraWrap (TECH FIG 10, which shows the wrapping of patient seen in Tech Fig 3).
TECH FIG 10 • Release of the nerve with subsequent NeuraWrap placement. Note the large calcaneal branch.
Once wrapping is complete, put the limb through a range of motion to ensure stability.
Close the subcutaneous tissues carefully with resorbable suture and close the skin with resorbable suture when possible to avoid irritation in the postoperative period.
Place a bulky cotton wrap around the leg with a medial lateral U-splint and a posterior L-splint of plaster, covered with Coban or elastic wrapping.
FETAL UMBILICAL VEIN WRAP OF TARSAL TUNNEL
The use of fetal umbilical vein wrap for neuritis seems to have decreased with time. The procedure is similar to the above surgeries, with careful neurolysis (TECH FIG 11) followed by application of the vein wrap. This material is somewhat thicker than the saphenous vein but easier to apply because it can often be wrapped circumferentially rather than “barber-poled” with the labor-intensive wrap technique that the saphenous vein requires.
TECH FIG 11 • Tarsal tunnel released and ready for wrapping.
TECH FIG 12 • Cutting the fetal umbilical vein longitudinally.
Cut the fetal umbilical vein longitudinally (TECH FIG 12).
Carefully wrap the material around the nerve (TECH FIG 13). The smaller side nerves may require a portal or hole cut in the nerve.
The completed wrapping must glide easily with ankle motion (TECH FIG 14).
In the case of postoperative infection, the material should be removed (TECH FIG 15), but the inflammatory reaction may leave a reasonable bed for the nerve.
TECH FIG 13 • Placing the umbilical vein around the posterior tibial nerve.
TECH FIG 14 • Finished umbilical wrap in place.
TECH FIG 15 • Infected graft removed at 3 weeks.
OTHER PERIPHERAL NERVE WRAP PROCEDURES TO MINIMIZE ADHESIVE CAPSULITIS
The decision to wrap the superficial peroneal nerve, the deep peroneal nerve, the saphenous nerve, or the sural nerve must be made in light of reasonable results with neurotomy.
The procedure would be similar to that for the posterior tibial nerve, with careful neurolysis and then wrapping with either autologous saphenous vein or NeuraWrap. The superficial peroneal nerve has been wrapped most often, with encouraging results.
POSTOPERATIVE CARE
Postoperative care depends on the extent of surgery performed and the risks of early motion on wound healing compared to the risks of stiffness.
Most wounds are immobilized for 2 weeks to allow healing, and then a gentle range-of-motion protocol begins, often with formal physical therapy for desensitization as well.
Weight bearing can begin at 2 weeks, progressing as tolerated.
Physical therapy later can assist with motion, desensitization, and gait training.
OUTCOMES
While outcome data can be difficult to interpret for initial tarsal tunnel release, the results of revision procedures can be even more confusing.
The best study on revision tibial nerve release5 found the best results when the initial distal release was inadequate.
Easley and Schon1 found significant improvement with peripheral nerve wrapping (scores improving from 8.5/10 to 5/10), especially with adhesive neuritis, which fared better than crush injury. They also found wrapping with fetal umbilical vein to be as effective as autologous saphenous vein. That study also included three superficial peroneal nerves and one deep peroneal nerve.
The data on NeuraWrap are anecdotal at the time of this writing, although initial results have been very satisfying from two centers.
COMPLICATIONS
The complications from revision nerve release and wrapping can be daunting, and careful preoperative discussion is essential. Most patients can expect some persistent nerve irritation for up to 6 months postoperatively, as some nerves are slow to recover (if they ever do). Sensory training can be very helpful in the postoperative period to recondition the limb.
Infection can be devastating, especially with the extensive dissection required and the dysvascular material being applied. The senior author of this chapter treated one infected fetal umbilical graft (for revision tarsal tunnel) with a simple irrigation and débridement, leaving the graft in for 3 weeks. With a more formal removal and débridement at 3 weeks, the vein left an excellent bed of shiny tissue that healed uneventfully and with excellent results. Another surgeon left the vein in for months, with resulting inflammation and irritation and a less satisfactory outcome. Superficial wound infection can be treated with local and oral antibiotics, but deep infection must be treated aggressively.
Vascular damage can often occur with the difficult dissection. Often, a small branch of the artery will be torn from the main posterior tibial artery. This problem can often be solved with one or two stitches of 8-0 or 9-0 suture, sealing the hole adequately. Preoperative evidence of a patent dorsal pedal pulse means that the posterior tibial artery may be able to be sacrificed, important knowledge in light of possible difficult repair.
Recurrent adhesive neuritis remains a difficult complication. Physical therapy, psychological counseling to deal with the stress of such an outcome, and possible revision procedures may offer some help to these patients.
REFERENCES
· Easley ME, Schon LC. Peripheral nerve vein wrapping for intractable lower extremity pain. Foot Ankle Int 2000;21:492–500.
· Kinoshita M, Okuda R, Morkikawa J, et al. The dorsiflexion-eversion test for diagnosis of tarsal tunnel syndrome. J Bone Joint Surg Am 2001;83A:1835–1839.
· Schon LC, Anderson CD, Easley ME, et al. Surgical treatment of chronic lower extremity neuropathic pain. Clin Orthop Relat Res 2001;289:156–164.
· Schon LC, Lam PW, Easley ME, et al. Complex salvage procedures for severe lower extremity nerve pain. Clin Orthop Relat Res 2001;391:171–180.
· Skalley TC, Schon LC, Hinton RY, et al. Clinical results following revision tibial nerve release. Foot Ankle Int 1994;15:360–367.
· Sotereanos DG, Giannakopoulos PN, Mitsionis GI, et al. Vein-graft wrapping for the treatment of recurrent compression of the median nerve. Microsurgery 1995;16:752–756.
· Vartimidis SE, Vardakas DG, Goebel F, et al. Treatment of recurrent compressive neuropathy of peripheral nerves in the upper extremity with an autologous vein insulator. J Hand Surg Am 2001;26:296–302.
· Xu J, Sotereanos DG, Moller AR, et al. Nerve wrapping with vein grafts in a rat model: a safe technique for the treatment of recurrent chronic compressive neuropathy. J Reconstr Microsurg 1998;14:323–330.