CHAPTER I I

PERIPH[P,g NEURECTOMY

Micbael S. Doumey, D,P.M.

Resection of a Morton's neuroma is the mostcommon example of surgical neurectomy of a

peripheral nerve. The time proven success of thisprocedure might falsely lead the surgeon to believethat neurectomy for other peripheral nerues of thelower extremity can be met with a similar success

rate. Unfortunately, this is not the case. In fact,Mofion's neuroma resection is the only frequentlyperformed neurectomy in the entire body. Exceptfor Morton's neuroma extirpation, surgicalneurectomy of a peripheral nerve should beavoided whenever possible. External and/orinternal neurolysis should be attempted wheneverthe entrapped nele or neuroma has a reasonablechance for recovery. Routine performance ofperipheral neurectomy for entrapped or damagednelves will frustrate both the surgeon and thepatient. Peripheral neurectomy frequently canresult in continuing pain syndromes related tostump neuroma formation, causalgia, bothersomehypoesthesia, or increased "compensatorysensation" in surrounding previously unaffectedperipheral nelves. However, when the peripheralnerve is damaged to an extent that neurolysishas failed or is unlikely to be beneficial, andconselvative measures have failed, peripheralneurectomy may still be the primary option.This paper reviews the author's clrrrent recommen-dations regarding peripheral neurectomies aboutthe foot and ankle.

DIAGNOSIS

The patient with a painful peripheral nerveentrapment or neuroma will typically present withsymptomatology related to the damaged or affectednerve(s). Typically, the pain has a primary sensorycomponent and is described by the patient as

"burning, shooting, or laciniating" pain. A thoroughhistory should be taken from the patient withpossible peripheral nerve pathology.

Once suspected, a complete physicalexamination should be performed. This examinationshould include obseruation and palpation of the

suspected neuroma or damaged nelve, and sensorytesting. Since most peripheral nerve injuries havesensory involvement before motor involvement,sensory testing will often be the "key" to thediagnosis. Reflex examination and skeletal motortesting should also be included in the evaluation.If a peripheral nele entrapment or neuroma is

suspected, the particular nele or nelves involvedmay be temporarily anesthetized to help confirmthe diagnosis. \7ith the combination of sensorytesting and diagnostic nerve biocks, mostperipheral neuromas and entrapped nerwes can bediagnosed. If larger nerves are involved, electrodi-agnostic studies or diagnostic imaging modalitiessuch as MRI may be considered to help confirm orsupport the diagnosis.

TREATMENT

Once a peripheral nen/e entrapment has beendiagnosed, treatment can be instituted. In mostcases, conselative measures should be attemptedprior to surgical intervention. These conservativemeasures most often include local steroid orsclerosing injections, oral anti-inflammatories,biomechanical suppofi or control, physicaltherapy modalities including iontophoresis orphonophoresis and desensitization techniques, andtopical medications such as capsaicin. \7henconselvative treatment has failed or been deemedinappropriate, surgical intervention is considered. As

stated eadier, external and/or internal neurolysisshould be considered initially if there is a reasonable

chance for the neurolysis to result in netwe recovery.If there is minimal or no chance that neurolysis can

lead to nelve recovery, or if neurolysis has failed,peripheral neurectomy should be considered.Obviously, resection of the typical Morton'sneuroma represents the exception to this approach,as neurectomy has proven to be a reliable methodfor the management of this condition.

Neurectomy involves the excision of a

segment of nerve. At times, especially when thenerve provides critical sensation and the distal

68 CFIAPTER 11

nelve and sensory receptors are ava1lab7e,neurectomy combined with nerue reconstructionmay be the most viable approach. If function of theentrapped nelve is not critical, or if previousattempts at neurolysis or nelve reconstructionhave failed, then resection of the nerve with orwithout transposition of the remaining nelve stumpis indicated.

Neurectomy is performed by isolating theentrapped portion of nerve, neuroma in-continuity,or stump neuroma. Dissection is carried proximallyuntil normal nerve is identified. Once the normalnerve trunk is delineated, sharp sectioning of thenerve is performed as far proximally as possiblethrough this normal nerwe tissue. The entrapmentor neuroma site may then be excised. Once theentrapped portion of nele has been resected,numerous operative techniques to inhibit axonalregrowth and transposition away from painfulstimuli have been described (Table 1). Each ofthese methods attempts to diminish stumpneuroma formation and/or attempts to transposethe nerye to an area subjected to the least possibleamount of mechanical stimulation.

Inhibition of axonal regrowth or stumpneuroma formation has been attempted viaphysical containment, synthetic containment, andphysiologic containment. Physical containmentincludes the use of alcohol, phenol, formaldehyde,nitrogen mustard, pepsin, hydrochloric acid,iodine, gentian violet, or insoluble steroidsafter neurectomy to attempt chemical cautery orinhibition of further neuroma formation. Further,neurectomy with electrocoagulation, laser cautery,radiofrequency current, and cryosurgery attemptthermal cautery of the nerve stump. Syntheticcontainment includes the use of inert materialssuch as silicone caps, rubber, plastic, lucite,polyethylene, collodium, cellophane, silver andgold foil, tantalum, glass, and nerve glues toattempt containment. Physiologic containment withepineurorrhaphy has been used alone or inconjunction with physical or synthetic containment.Although long-term clinical studies with thesevarying methods are scarce, these approaches havehad minimal reported success at diminishingrecurrent stump neuroma formation, and somehave been associated with foreign body reactions.

Table 1

SURGICAL TREATMENT FORTRANSECTED I\ERVE ENDING

INHIBITION OF AXONAI REGROWTHPhysical Containment

Chemical TreatmentAlcoholPhenolFormaldehydeNitrogen mustardPepsinHydrochloric acidIodineGentian violetSteroids

CauteryElectrocoagulationLaserRadiofrequency currentCryosurgery

LigationSynthetic Containment

Silicone capsRubberPlasticLucitePolyethyleneCollodiumCellophaneMetallic foilTantaumGlassNerve glue

Physiologic ContainmentEpineurorrhaphyNerve grafting

TRANSLOCAIION AWAY FROMPAINFUI, STIMULI

Excision and retractionImplantation into muscleImplantation into boneEn bloc translocation

(Adapted from Downey MS: Management of neurologic trauma. InScurran Bl, ed. Foot and Ankle Trauma New York, N.Y.; ChurchillLivingstone; 1,989: 245)

CHAPTER 11 69

Transposition of a resected nelve end awayfrom potential irritation appears to be preferable toin situ containment. Excision of a neuroma andallowing the netwe end to retract proximally maybe of benefit, as it allows the nerye ending to restin a proximal site away from the surgical incisionand original site of entrapment. However, if thenelve end comes to rest in a poor soft tissue bedor continues to be irritated, this approach will bedoomed to failure. Resection of the classic Morton'sneuroma is an example of excision of a portion ofnelve with proximal retraction of the nelve stump.

Alternatively, the resected end of the neruemay be transplanted into bone or muscle. Thestfticture used should be in close proximity to thenelve ending, and subject the nerue to the leastpossible amount of mechanical irritation.\Thenever possible, the author generally prefersimplantation of the nen/e ending into innervated,weli-vascularized muscle or bone away fromdeneruated skin and scar tissue. Mackinnon andDellon' coined the term "neurotrop(h)ism" tosllggest influences that facilitate both nerve fibermaturation and appropriate direction of regenera-tion. Recent research suggests that cut nelveendings implantecl into inneruated muscle are leastlikely to demonstrate significant "neurotrop(h)ism,"thus the nerve is least likely to attempt regenerationin innerwated muscle tissue.z,3 Implantation intomuscle is accomplished by suturing the epineuriuminto the belly of the muscle. If the surgeon prefersor if an appropriate muscle belly is not available,

Figure 1A. Sural neurectomy wilh implantation of the nerue stumpinto lateral calcaneus. Preoperative appearance. The patient devel-oped post-incisional sural nen-e entrapment lbllowing tr.o previoustailor's bunion procedures.

bone may be used.a,'A small trephine hole is madeinto the bone and the epineurium is sutured intothe opening created, thus buryrng the cut end ofthe nele into bone (Figs. 1A-1H).

Finally, en bloc transfer of an intact neuroma,or neuroma resection with primary neurorrhaphyor grafting may be considered. Herndon et a1.6

reported 720/o minimally painful or tender resultsfollowing en bloc transfer of intact neuromas withtheir fibrous scar tissue encapsulation to anadjacent area that was more protective and freefrom scar tissue. Although these results are promis-ing, en bloc transfer would not appear to offer anyadvantage over implantation of a freshly cut nelveending into bone or muscle. Hattrup and Wood'reported 770/o (10 of 13) of their patients haddiminished symptomatology following neurectomywith interfascicular grafting. However, nervereconstruction is generally reserued for nerves witha maior motor component, and when consideringthe foot and ankle, would be limited to recalcitrantlesions of the posterior tibial nerue.

Following neurectomy, the soft tissues shouldbe closed in anatomic fashion. A compressiondressing should be applied and a closed suctiondrain utilized if necessary. Protected weight bearingor non-weight bearing should be considered forthe first 2 lo 4 weeks. Range of motion exercisesand rehabilitative modalities should be institutedafter 7 to 10 days, and accelerated after woundhealing.

Figure 18. The sural nerwe is harwested, evaluated, and determined tobe ertensir.ely damaged.

70 CHAPTER 11

Figure 1C. The sural nerue is resected distally, and then carefully clis-sected proximally to the lateral calcaneal area.

Figure 1D. A trephine hole is made in the lateral calcaneal u,all

Figure 1F. The sural nene is sharply transected proximally. maintain-ing just enough length to implant the nerue stllmp into the calcaneus.

Figure 1H. Resectecl portion of sutal nerwe is sent for pathologic eval-uation.

Figure 1E. The proximal portionsmall amount of dexamethasone

of the sural nerve is injected n-ith a

phosphate.

Figure 1G. The epineurium of the nerue stump is sutured into thetrephine hole in the calcaneus. The hemostat points to the implantednen-e stllmp.

A tliritk)n r{ {}*RcYal kttYlle1Y

CHAPTER 11 7t

COMPLICATIONS

Peripheral nelve surgery can be very rewarding,but just as often can be frustrating for both thesurgeon and patient. Even with an accuratepreoperative diagnosis, good intraoperativetechnique, and proper postoperative management,complications can occur. Therefore, the preopera-tive development of a good patient-physicianrappofi with a thorough, informed discussion ofthe procedure, alternatives, potential risks andcomplications, and postoperative course is criticalto the success of the procedure. Aside from thecomplications inherent to any surgery in the lowerextremity, peripheral neurectomy has a unique setof potential complications which include: recurrententrapment and neuroma formation, sensorimotoralterations as the sensory and motor components ofthe nelve are altered, and reflex sympatheticdystrophy or causalgia as the sympatheticcomponent of the nerve is irritated. In arrypafiicular patient, each of these complications hasthe potential to cause pain greater than thatexperienced prior to surgery.

SUMMARY

\fith the exception of neurectomy for a classicMofion's neuroma, peripheral neurectomy shouldbe considered a "last resort" for the management oflower extremity nefl/e entrapments and neuromas.When peripheral neurectomy is necessary, theauthor advocates implantation of the transectednelve end into either innervated skeletal muscle orbone. In this fashion, many of the complicationsassociated with peripheral neurectomy can bereduced or eliminated.

REFERENCES

1. Mackinnon SE, Del1on AL: Surgety of tbe PeripberdlA?rze. Nes'York, N.Y.: Thieme Meclical Publishers; 1988.

2. Dellon AL, Mackinnon SEr Treatment of the painftrl neuroma byneuroma resection ancl muscle implantation. Plast Reconstr Surg77:427-436. L986.

3. Mackinnon SE, Dellon AL, Hudson AR, Hunter DA: Alteration ofnellroma formation by manipulation of its microenvironment.Plast Reconstr Surg 7 6:345-352, 7985.

4. Boldrey E: Amputation neuroma in nerves implanted in bone.Ann Surg 718:7052-1057, 1913.

5. Goldstein SA, Sturim HS: Intraosseous nelve transposition fortreatment of painful neuromas. J Hand Surg 10A:270-274, 7985.

6. Herndon JH, Eaton RG, Littler JW: Management of painfulneuromas in the hand. .l Bone.Joint Surg 58A:369-313, 7916.

7. Hattfl.lp SJ, Wood MB: Delayed neural reconstmction in thelower extremity: results of interfascicular nerve graftrng. FootAnkle 7:L05, 1986.

ADDITIONAL REFERENCES

Downey MS: Management of neurologic trauma. In Scurran BL, ed.l-oot and Ankle Trauma New York, N.Y.: Churchill Livingstone;1989: 279-216.

Holmes GB Jr: Nen'e compression syndlomes of the foot and ankle.In Gould JS, ed. Operatiue Foot Surgety Philadelphia,PA.: WBSaunders; 1991: 781-197.

Malay DS, McGlamry ED: Acquired neuropathies of the lowerextremities. In McGlamry ED, Banks AS, Downey MS, eds.Comprebensiue Textbook of Foot Surgery 2nd ed, Baltimore,M.D.:'Williams & Wilkins; 1992: 7095-7723.

Merrill TJ: Peripheral nen-e entrapment syndromes of the lowerextremit),. In Nlarcinko DE, ed. Medical and Surgical Therapeuticsof the Foot and Ankle Baltimore, M.D.: riflilliams & Wilkins; 1992:) lq-)\)