METATARSOCU NEIFORM EXOSTOSIS-EVATUATION ANDPRINCIPLES OF MANAGEMENT

Thomas F.

INTRODUCTION

The first metatarsocuneiform joint (MCJ) exostosis isa common presenting complaint in the forefoot. It maypresent as an isolated deformity causing shoe irritation.It may likewise appear in combination with a variety oflocal first ray conditions such as hallux valgus, orsystemically related conditions such as Charcot jointdisease. Careful clinical assessment/ accurate diagnosis,and a logical approach to treatment is in order. The varie-ty of tissues in this anatomic area, coupled with the com-plexity of first ray function, demands special attentionto this relatively common forefoot problem (Fig. 1).

To understand the complexity or simplicity of the con-dition, treatment will be related to the physical findingsand chief complaints of the patient. This practical ap-proach may help to keep the discussion more clinicallyoriented. A thorough review of the possible clinical syn-dromes is provided, and patient complaints are cor-related to clinical findings. Management is based onclinical findings and a review of surgical techniquesfollows. We will emphasize the surgical approaches andtech n iq ues.

CTINICAL HISTORY

First metatarsocuneiform joint problems may be a

primary concern or only a secondary complaint of thepatient. Often the patient is distracted by a painful halluxvalgus or hallux limitus so as to be unaware of signifi-cant discomfort proximally at the first metatar-socuneiform joint. The old saying "sitting on a tack, whilebeing hit with a stick" can only too often be realizedpostoperatively. With successful correction of primarycomplaints, secondary concerns may move to assumetheir place. The first metatarsocuneiform joint should bethoroughly evaluated in any condition affecting thehallux or first metatarsophalangeal joint.

Pain or complaints about the first metatarsocuneiformjoint vary according to the tissue involved. Symptomshelp assess the soft tissues and osseous structures in-volved. The complaint may be as simple as skin irrita-tion over the bump on the dorsum of the foot. Rarelyis the situation this simple on close examination (Fig. 2).

Smith, D.P.M.

Deep aching pain, especially coupled with post-staticdyskinesia may signal significant arthrosis or joint in-volvement. The level of pain, either superficial or deepcan be a helpful clue. A history of trauma, recent or past,and its management at the time of injury is very impor-tant in arthrosis assessment.

lf trauma is reported, a thorough record of the pastdiagnosis and treatment should become part of the of-f ice record. Whether dislocation, fracture, or tendon in-jury was present or suspected should be determined.Years may pass before the complications of anoverlooked or subtle inlury present.

Fig. 1. A. Preoperative lateral radiograph and, B. Postoperative lateralradiograph of first metatarsocuneiform joint (MCl).

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Fig. 2. Differential diagnosis of first metatarsocuneiform ioint pro-

minences. A. First MCJ exostosis. B. LisFranc's joint hypertrophy as seen

A treatment summary or copy of office or emergencyroom records may be helpful. Only then can the ap-propriateness of treatment provided at the time of in-jury be assessed. It should be kept in mind that standardsof care may vary regionally and may have been changedor adapted over time. An injury twenty years ago mayhave been treated far differently than it would be today.

Burning or other paresthetic complaints need to be

carefully assessed, especially if operative options are be-

ing considered. The presence of these findingspreoperatively is critical. Postoperative neurologic symp-toms may only be a continuation or exacerbation of a

preoperative neuropraxia. They need not necessarily be

a postoperative complication. Such symptoms may signal

beginning healing of nerve tissue long damaged bychronic shoe pressure and irritation preoperatively.

The patient must be asked Specifically aboutneurologic type symptoms. These should be accuratelyrecorded in the patient chart. A mapping by the patientof any areas of paresthesia or numbness withphotographic or artistic record in the patient chart is veryhelpful. Rarely is a diagnosis of simple metatar-

here post-traumatic. C. Pseudo-exostosis of pes cavus' D. Soft tissue

mass represented by ganglion here.

socuneiform joint exostosis made without a concomitantdiagnosis of neuritis. The neuritis may involve either themedial dorsal cutaneous nerve or saphenous nerve' The

dermatome distribuiion of discomfort will help make thedistinction (Fig. 3).

[:xtreme soft tissue pain of an acute nature may markthe presence of tendinitis. Pain on activity, especially

against resistance, generally points to tendon involve-ment. Tendinitis usually produces severe pain, at timesincapacitating in its severity. Surgical consideration fora first metatarsocuneiform joint exostosis complicatedby tendinitis may need to be delayed until the tendinitiscan be controlled. Careful note should be made of anyhistory of tendon injury or lacerations about the area ofthe first metatarsocuneiform joint. Subtle tendon lacera-

tions misdiagnosed in prior years may present with firstray deformity as a complication. The force of tendon im-balance about the first ray should not be underestimated.

The complaint may be only of a mass, swelling, or a

growth on the dorsum of the foot. Careful history as tothe onset, duration, and changes in size should be noted.One should avoid snap diagnosis but keep an open mind

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Fig. 3. Extensor hallucis longus tendon and medial dorsal cutaneousnerve as visualized in dissection of first MCJ.

to the diagnostic possibilities. Neurologic symptoms maycharacterize patient concern, yet an unknown soft tissuemass or carcinoma may become your concern. Pressurefrom a tumor can result in misdiagnosis.

Commonly ganglions may be found on the dorsum ofthe foot. Adventitious bursae that become acutelyinflamed are occasionally encountered at this level of theforefoot. A bony prominence may be present in conjunc-tion with one or all of these soft tissue conditions. Thepossibility of multiple diagnosis should always be con-sidered. No one diagnosis is mutually exclusive.

Past medical history is always an important part of theinitial or follow-up discussions with any patient. Bonyprominence complaints or concerns can be associatedwith Charcot joint disease. The first metatarsocuneiformjoint or LisFranc's joint complex is a common site ofCharcot degeneration. Cenerally, the hypertrophy ofbone associated with Charcot disease is tremendouslyexaggerated compared to degenerative joint disease. lnaddition there is normally a significant associated hyper-mobility. The exostosis of Charcot joints can be variablealong the metatarsocuneiform joints or involve any orall of the lesser and greater tarsal joints. The etiology ofthe Charcot joint can be variable as well. The diagnosismay include diabetes mellitus, as well as alcoholism,tabes dorsalis, or spinal cord tumors and trauma. Acareful history can be very helpful in attempting toestablish the diagnosis of Charcot disease prior to anyradiographic or laboratory confirmation.

Charcot joint changes may appear at any stage in thedisease. Early presentations as well as sequellae fromlongstanding joint disease are all possible. The earlyCharcot changes may be the first clinical sign of a

systemic disease process.

As the history of the chief complaint is being taken oneshould think of all tissues present in this area of the foot

from skin to bone. Questions should be asked specifical-ly beginning at the skin level and working from super-ficial to the deeper joint levels. A quick screening ques-tion at each tissue level helps guide more in-depthassessment. AII tissues are thus screened prior to thephysical examination. The physical examination can thenbe more logically performed.

A cross-section of the first metatarsocuneiform jointincludes all tissues, osseous and soft, as found in anyextremity. Each may be of primary concern or secondarilyaffected. Careful clinical questioning begins thethorough evaluation process.

PHYSICAI EXAMINATION

Physical assessment logically follows the carefulhistory. A logical sequence of evaluation maneuverssuperficial to deeper tissues is also helpful in this por-tion of the history and physical. The examination will em-phasize those areas of concern noted in the history, yetat least screen all tissues and layers present. The absenceof neurologic complaints, for example, in a chief com-plaint does not mean that the nerve function is not atleast screened. Sensory neuropathy of diabetes mellituscan be overlooked where its presence would be helpfulin the diagnosis of Charcot disease hypertrophy of thefirst metatarsocuneiform joint.

The skin is evaluated first to describe any visualfindings of edema, erythema, or changes in texture.These changes in texture may take the form of hyper-trophy, lichenification, or callosity. Ulcerative breakdownin the face of poor vascular status and pressure may benoted. The exact location of irritation from the shoe onthe dorsum of the foot should be noted. This irritationmay be localized to the first metatarsocuneiform jointor extend more laterally across Lisfranc's joint.

The subcutaneous layer is considered next. The nervesare first screened by several physical assessment tech-niques. Sensation is established for light touch andpressure for the distribution of the saphenous nerve,medial dorsal cutaneous nerve, and deep peronealnerves. Varying nerve dermatome distributions are possi-ble for this area of the forefoot. For clinical evaluationpurposes, only the sensation that is present and of nor-mal quality is of importance. Any change or alterationshould be carefully noted as compared with the con-tralateral extremity.

The nerves are then palpated to recreate any pain orparesthesia distally as may be noted during ambulationin shoe gear. Any nerve, if palpated firmly enough, willcreate paresthesias distally. lf, however, light digitalpalpation or percussion produces significant discomfort,neuropraxia or neuritis should be considered as a

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diagnosis. Ceneral hypertrophy of the nerve itself maybe noted as compared to the unaffected extremity. Themedial dorsal cutaneous nerve and its terminal branchesare the most commonly affected in this area of theforefoot.

The subcutaneous layer may contain masses such as

bursae or tumorous swellings. Masses at this level maybe fixed to the skin and immobile with respect to it. Thelevel of the mass with respect to the extensor tendonsshould be carefully noted. The extensor tendons lie im-mediately deep to the deep fascia. lf the mass is notedsuperficial to the extensor tendons the mass, at least inpart, lies superficial to the deep fascia. The relationshipof the mass to the extensor tendons is very helpful indetermining depth of the mass. lt must be kept in mindthat the deeper masses, especially ganglions, may extendfrom the deeper layers through the deep fascia to themore superficial layers.

The deep fascia and extensor tendon layer is con-sidered next in the clinical evaluation process. The ten-dons should be carefully palpated for continuity fromorigin to insertion. Any areas of hypertrophy or atrophyshould be noted. Manual muscle testing of all first ray

intrinsic and extrinsic muscles should be carefullyassessed and charted. All pedal tendons should be

screened at a minimum. A ruptured tibialis posterior ten-don can present as a rapidly progressing pes valgus ina geriatric patient with a complaint of first metatar-socuneiform joint pain.

Subtle, slowly changing foot problems and deformitiesare generally the result of tendon imbalance. The firstray is plantarflexed and this results in apparent firstmetatarsocuneiform joint prominence, not necessarilyexostosis.

Tendinitis appears clinically as an acutely tender areaabout the dorsum of the foot. Pain may extend along thetendon sheaths into the ankle area. Discomfort may be

present with active motion especially against resistance.The clinical signs may appear so severe as to mimic gout.Tendinitis and inf lammation of surrounding tissues is a

very painful clinical situation.

The bone and joint structures are assessed for possi-ble exostosis formation. Local palpation of the joint aboutits entire circumference should be carried out. Rarely ishypertrophy strictly a dorsal phenomenon. Patient com-plaints are strictly dorsal due to the susceptibility of thebony prominence to shoe irritation. The plantar hyper-trophy is protected by the padding of the intrinsicmuscles within the arch of the foot (Fig. 4).

The lateral extent of the osseous hypertrophy shouldbe carefully palpated. Unrecognized lateral extension ofhypertrophy along LisFranc's joint may become exag-

gerated after resection of first ray hypertrophy.

The stability and range of motion of the first metatar-socuneiform joint is then palpated. An unaffected ex-

tremity is a helpful standard to assess the range of mo-tion. An increased range of motion may indicate com-promise of the periarticular tissues as noted in Charcotjoint disease. Pain on stress and range of motion helpidentify the presence of arthrosis and arthritic degenera-tion. Many times it is difficult for the patient clinicallyto distinguish Iocal irritation from deeper arthrosisrelated discomfort.

An important differential diagnosis is pseudo exostosisof the pes cavus foot type. ln rigid plantarf lexed first ray

and rigid cavus foot types with the apex of deformity near

LisFranc's joint, shoe pressure may be a complaint overthe dorsum of the midtarsus. The first metatar-socuneiform joint contours may appear clinically promi-nent. The first metatarsocuneiform ioint exostosis is not

Fig. 4. Radiographic demonstration of first MC.l exostosis. A

Preoperative and, B. Postoperative radiographs'

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necessarily the diagnosis. The joint contours may bewithout exostosis. An apparent prominence is due to thefoot type and position. Resection in such cases is of lit-tle clinical help in relieving shoe pressure. Pes cavus cor-rection may be needed to help with shoe irritation forsuch patients. The first metatarsocuneiform joint ex-ostosis is more commonly associated with flexible pescavus or hypermobile plantar flexed first ray, not rigidones.

MANAGEMENT PRINCIPTES

The surgical management of first metatarsocuneiformjoint prominence involves soft tissue and osseous con-cerns. lf soft tissue masses are present, such as bursaeor ganglions, they may require excision. Nerve involve-ment may require excision or transposition. Osseous pro-cedure selection involves a choice between simple ex-ostosis resection and arthrodesis.

Conservative management is generally attempted asa first line of treatment. Padding and shoe modificationscan be very helpful. They are not wasted if operativerepair is later carried out. They can become usefulpostoperative aids while scars are still immature and sen-sitive. The association of first metatarsocuneiform jointexostosis and first ray hypermobility has been discussed.The use of functional orthoses is very helpful for suchpatients. The intermittent dorsal compressive forces atthe first metatarsocuneiform joint can be reduced by or-thoses and effective shoe gear. These devices are likewisevery useful in the postoperative management. The useof injectable medication such as corticosteroids can behelpful if tendinitis or neuritis are present. lf surgery isconsidered, some delay following a local injection maybe prudent. Compromise to healing tissue may result inthe presence of recent local corticosteroid injection.

Canglions are considered for excision if aspiration andinjection therapies are unsuccessful. The chance of nerveentrapment on the dorsum of the foot is great in thisanatomic area. This complication is viewed by most pa-tients who experience it as far worse than the originalganglion. Excision of all ganglion tissue needs to be ascomplete as possible to help avoid recurrence. Recur-rence following injection as well as excision is alwayspossible.

lf neurologic symptoms are present, special attentionmay be given to them during surgery. The nerves maybe prominent over this area and susceptible to irritationpostoperatively. Epineural sutures and nerve relocationto a more protected position may be helpful. Sub-cutaneous fatty tissue may also be lightly envelopedabout the nerve to help secure and protect it. Rarely isresection of a nerve indicated as a primary procedure.

Cenerally, neurectomy is preserved for more recalcitrantcases where other techniques have failed. A smallamount of short acting corticosteroid may be applieddirectly to exposed nerve prior to closure during osseousresection techniques.

Cood scar management is mandatory postoperativelyuntil healing is complete. This will help reduce thechance of nerve entrapment. Compression dressingsmaintained to some degree throughout the scar matura-tion process can be extremely useful in reducing the den-sity of scar tissue throughout the depth of the surgicalwound. Compression needs to be maintained24 hoursdaily, well through the collagen phase of healing, untilwound maturation begins in 4 to 6 months. Chronic in-duration and scarring of soft tissues is avoided and moresupple mobile tissues are promoted.

Thick dense scarring following osseous resection canbe as much a problem in this area as the original ex-ostosis. The firm scar can be as irritating to surroundingnerves as the original exostosis. All the above mention-ed measures help reduce the incidence of postoperativeentrapment and nerve irritation. Certainly atraumatictechnique and meticulous hemostasis must bemaintained throughout the operative procedure.

Simple first metatarsocuneiform joint exostosis resec-tion is a very rewarding procedure. Foot functionmanagement postoperatively helps prevent recu rrence.The exostosis should be considered realistically as a

symptom not the diagnosis. The diagnosis is generallyan abnormality of foot function resulting increased loadon a hypermobile first ray. The exostosis must be viewedas an osteoarthritic process promoted by chronic abnor-mal joint function.

Significant joint arthrosis with exostosis maynecessitate arth rodesis. Arth rodesis is I i kewi se advi sablewhen gross first ray malalignments are present. Ar-throdesis is useful when significant uncontrollable orunrepairable tendon imbalance is present. First metatar-socuneiform joint arthrodesis should not be viewed as

a correction for associated pes valgus. Such use of thisprocedure generally results in significant tibialsesamoiditis and eventually more proximal joint com-promise and breakdown.

Arthrodesis is considered in cases of Charcotdegeneration. Any LisFranc's joint hypertrophy involv-ing more than the first ray, may necessitate moreinvolved arthrodesis across LisFranc's joint. If the Char-cot joint collapse is present and hypertrophy exists wellacross LisFranc's joint, arthrodesis of the entire tar-sometatarsal joint complex should be considered.

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Fig, 5. Arthrodesis first MC.J with bone graft. A. preoperative and B' Postoperative radiographs. Note maintenance of length o{ first ray

First metatarsocuneiform joint arthrodesis requiresgood fixation techniques. Compression fixation using theASIF technique is employed. An attempt is made to avoidcrossing other lesser tarsal joints with the fixation. Oc-casionally it is necessary to cross other lesser tarsal jointsin order to facilitate screw purchase in osteoporoticstates. These screws must be removed prior to extensiveambulation. Arthrosis may be induced by screws remain-ing in place across joints that have not been arthrodesed(Fig. s).

SUMMARY

Appropriate assessment of the first metatar-socuneiform joint exostosis may result in adequateosseous resection but result in persistence of other softtissue and joint complaints. Any condition affecting thefirst ray should receive a meticulous evaluation of thefirst metatarsocuneiform joint. The forthright approachto assessment through history and physical examinationis recommended. lts use in first metatarsocuneiform jointexostosis is encouraged to help the practitioner makea careful thorough assessment. Only then is treatmentlogical and appropriately applied to one of a number ofpossible clinical situations.

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