TARSAL cOAtlTlON: CURRENT cllNlcAt ASPECTS wtTHINTRODUCTION OF A SURGICAT CLASSIFICATION

Michael S. Down€/2 D.P.M.

INTRODUCTION

Tarsal coalition is a condition that exists when thereis absent or restricted motion between two or more tar-sal bones. Coalitions can produce a dramatic symptomcomplex which may ultimately be identified as rigidperoneal spastic f latfoot. Tarsal coalition and itsassociated symptom complex should be well understoodboth clinically and radiographically. Such understandingwill enable the clinician to properly identify tarsal coali-tions and to initiate appropriate treatment.

HISTORICAT REVIEW

Tarsalcoalitions have been identified and recorded forseveral hundred years. Heiple and Lovejoy (1) reporteda tarsal coalition in the foot of a pre-Columbian indianskeleton circa A.D. '1000. Coe and Broman (2) found aneven older specimen located in the ruins of a Mayan tem-ple. Historically, the first written description of tarsalcoalition is attributed to Buffon (3) in 1769. Sir RobertJones (4) gave the first detailed clinical description ofperoneal spastic flatfoot in 1897, but did not associateit with tarsal coalition. The first radiographic demonstra-tion of a tarsal coalition was by Kirmissin (5) in 1898, onlythree years after Roentgen's discovery of x-rays.

Many years intervened between the earliest anatomicdescriptions and the discovery of x-rays, and many morebefore the identification of the relationship between tar-sal coalition and peroneal spastic flatfoot. In this sense,the two most common tarsal coalitions: calca-neonavicular and talocalcaneal, were identified in similarfashion. First, they were identified anatomically, thenradiographically, and more recently related to peronealspastic flatfoot.

Calcaneonavicular coalition was first describedanatomically by Cruveilhier (6) in 1829. Slomann (7), in1921 , reported five cases of calcaneonavicular bar anddemonstrated the coalition on an oblique radiographicview of the foot. However, not until 1927 when Badgely(8) resected a calcaneonavicular coalition, was the de-formity associated with peroneal spastic flatfoot.

Similarly, Zuckerkandl (9) first anatomically identifieda talocalcaneal coalition in1877. Korvin (10), in 1934, util-

ized an axial radiographic view of the calcaneus todemonstrate a talocalcaneal coalition . ln 194f., Harris andBeath (11) popularized the ski-jump or axial view of thecalcaneus and recognized talocalcaneal coalition as acause of peroneal spastic flatfoot.

Other tarsal coalitions are less frequent, but have beenreported. Talonavicular coalition was first reported byAnderson (12)in1879. Calcaneocuboid coalition was firstdescribed by Holland (13) in 19'18. Cubonavicular coali-tion was first reported by Waugh (14) in 1955. Lusby (15)

first identified a naviculocuneiform coalition in 1959.Multiple and massive coalitions involving several tarsalbones have also been reported (16).

ETTOTOCY

Tarsal coalition is clearly the most common cause ofperoneal spastic flatfoot. However, the cause of tarsalcoalitions is not so clear. Many authors have attemptedto attribute all tarsal coalitions to one etiology. lt is nowcertain that there are many etiologies, and that tarsalcoalitions can be either congenital or acquired.

Congenital tarsal coalition is more frequently identifiedand reported, although the mechanism of congenitalcoalition is not conclusively known. Pfitzner (17) sug-gested that congenital tarsal coalition is formed from theincorporation of accessory ossicles into the normal tar-sal bones on either side. Although this has been shownto be one possible cause of coalition (18), Harris (19) hasdisproven it as the sole cause by demonstrating a tarsalcoalition in a fetus.

Harris' finding supports Leboucq (20) who suggestedthat congenital coalition results from the failure of dif-ferentiation and segmentation of primitive mesenchyme.This theory would attribute congenital coalitions to aheritable defect or to an insult in the first trimester ofpregnancy. Subsequently, numerous authors havereported hereditary patterns of coalitions (16,21-27).

A large field study by Leonard (28) provided the mostsupportive evidence to Leboucq's theory. Leonard con-cluded that tarsal coalition was a unifactorial disorderwith autosomal dominant inheritance. Thus, today, themost commonly accepted theory for the etiology of

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congenital coalition is a genetic mutation to anautosomal gene which results in the failure of differen-tiation and segmentation of primitive mesenchyme.

Acquired tarsal coalition can result from arthritis, in-fection, trauma, neoplasms, or other causes (29). Ac-quired coalition will be less common in pediatric andadolescent patients (30). The causes of acquired tarsalcoalition can also lead to varying degrees of joint limita-tion without complete coalition (31). When all age groupsare considered, this is a frequent cause of peronealspastic flatfoot.

INCIDENCE

The incidence of tarsal coalition in the general popula-tion is unknown. Vaughan and Segal (32), studying armypersonnel, found the incidence to be approximately 1%(i.e., 21 cases of tarsal coalition in 2,000 patients). Thisis the highest reported incidence to date. The actualincidence may be higher or lower.

It should be remembered that the incidence of tarsalcoalition is not the same as the incidence of peronealspastic flatfoot. Peroneal spastic flatfoot is usually a

sequela of the tarsal coalition. A tarsal coalition may bepresent without symptomatology and/or withoutperoneal spastic flatfoot. Rarely, peroneal spastic flatfootmay be present without tarsal coalition.

Tarsal coalition has been reported to have no racepreference. Further, roughly 50o/o ol the cases have beenreported as being bilateral (33), although Leonard (28)

reported as high as B0% bilateral involvement.

Several authors have suggested a greater incidence oftarsal coalition in males. Beckly et al (34) noted a

male:female ratio of 12:5, and Conway and Cowell (35)

noted a ratio of 4:1. lt has been theorized that this un-equal sex predilection may be due to the studies havingbeen performed on army personnel (36). lndeed, if thesestudies are correct in their suggested predilection, thetheory of mutation of an autosomal dominant gene mustbe reconsidered. Leonard reported a more equal sex

incidence in his large study (28). Thus, the actual sexpredilection remains unclear.

Talocalcaneal coal ition and calcaneonavicu lar coal itionare by far the most common anatomic types. These twotarsal coalitions account for approximately 90% of all tar-sal coalitions (37). Controversy does exist as to which ofthese two coalitions is most prevalent. Leonard (28)

reported an extremely skewed study with 27 oul ol 31

patients having calcaneonavicular coalitions. Otherstudies have demonstrated a more even division or f ind-

ings favoring a higher incidence of talocalcaneal coali-tion. ln 68 patients, .lack (38) reported 27 talocalcanealcoalitions and 23 calcaneonavicular coalitions. In Rankinand Baker's (33) series there were 9 talocalcaneal coali-tions and 5 calcaneonavicular coalitions. Thus, it is thecurrent consensus of opinion that talocalcaneal coalitionis the most common.

Talonavicular coalition appears to be the third mostcommon type of tarsal coalition. This type is rare withless than forty cases reported in the literatu re.Calcaneocu boid, cu bonavicu lar, navicu locu neiform,combination tarsal coalitions and massive coalitions oc-cur with even less frequency (36,39).

CLASSIFICATION

Tarsal coalitions may be classified in several ways: (1)

etiologic type; (2) anatomic type; (g) tissue type; and (4)

according to articular involvement. The author proposesthe latter classification (i.e., according to articular involve-ment) as a surgically-based classification which is the onlysystem above that might relate any tarsal coalition to theIikelihood of surgical success.

Tarsal coalitions can be classified according to theiretiology-either congenital or acquired (311. Thisclassification is not generally helpful in ascertaining thebest possible treatment plan.

Further, tarsal coalitions may be classified accordingto their anatomic constituents. Tachdjian (40) has pro-vided a classification subdividing coalitions into thebones that are abnormally united, or infrequently, as partof a complex malformation (Fig. 1). Although onlydescriptive in nature, Tachdiian's classification suggeststhe importance of assessing other areas of the foot andthe remainder of the body when an apparently local orisolated coalition is identified.

Another common manner of grouping tarsal coalitionsis to classify them according to the tissue type of theirunion. ln this way/ a coalition may be a synostosis(osseous union), synchondrosis (cartilaginous union),syndesmosis (fibrous union), or a combination of theabove. A synostosis may evolve f rom a synchondrosis orsyndesmosis. This has been theorized to occur with ageor possibly after trauma to the coalition (30). A synostosisis also referred to as a complete coalition since all mo-tion is necessarily absent. An incomplete coalition has

varying amounts of interposed cartilaginous or fibroustissue and may allow motion between the bonesinvolved. The tissue type of the coalition is importantand should be noted when attempting to diagnosea coalition.

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lsolated AnomalyDual between two tarsal bones

TalocalcanealMiddle

CompletelncompleteRudimentary

PosteriorAnterior

Calcaneonavicu larTalonavicularCalcaneocuboidNaviculocuneiform

Multiple - combinations of the aboveMassive - all tarsal bones fused together

Part of Complex MalformationIn association with other synostoses

Carpal coalitionSymphalangism

As one of manifestations of a syndromeNievergelt-PearlmanApert's

ln association with major limb anomaliesAbsence of toes or rays"Ball-and-socket" ankle jointFibular hemimeliaPhocomeliaProximal focal femoral deficiency

Fig. 1. Tachdlian's classification of tarsal coalitions. (Revised fromTachdiian MO: Ihe Child's Foot, pp 262, WB Saunders, Philadelphia,198s).

It is the author's impression that the aforementionedclassification systems are primarily descriptive in nature.By combining these classifications, a useful descriptionof a tarsal coalition can be made. For example, a tarsalcoalition may be described as a congenital synchondrosisof the middle facet of the talocalcaneal joint. Civen thisinformation, one can more accurately understand the tar-sal coalition present. However, these classif icationsystems, even when combined, provide only a smallamount of information related to the development of asurgical treatment plan.

For this reason/ a new classification system based uponthe articular relationship of the bones involved in thecoalition and the indirect effect of the coalition on sur-rounding joints is proposed (Fig. 2). This articularclassification system, when combined with the descrip-

tive parameters already discussed may serve as a basisfor communication about possible surgical treatment.The classification assumes that the most importantcriteria for determining treatment are the age of the pa-tient, the type of coalition, and the degree of secondaryarthritic changes.

The classification begins with a division into juvenile(osseous immaturity) and adult (osseous maturity). lt isthen further subdivided into the types of coalition -

whether extra-articu lar o r i ntra-articu lar. Extra-articu larcoalitions are those that occur outside a normal joint.These coalitions have been frequently called bars, andthe calcaneonavicular coalition is the most common ex-ample. Intra-articular coalitions occur at normal jointsites and have been referred to as bridges. A talocal-caneal coalition of the middle facet of the subtalar jointis the most common example of an intra-articular coali-tion (Fig. 3). Finally, the classification is further sub-divided into the presence or absence of significantsecondary arthritis or changes within surrounding joints.

As an example, a middle facet talocalcaneal coalitionoccurring in an adult with secondary arthritic changesat the talonavicular andior calcaneocuboid joints wouldbe an Adult-llB coalition (Fig. a). A calcaneonavicularcoalition occurring in a child with no secondary arthriticchanges would be a Juvenile-lA coalition (Fig. 5). ln thismanner, treatment plans may be related to the classifica-tion system as will be discussed later.

Juvenile (Osseous lmmaturity)Type I - Extra-articular coalition

A - No secondary arthritisB - Secondary arthritis

Type ll - lntra-articular coalitionA - No secondary arthritisB - Secondary arthritis

Adult (Osseous Maturity)Type I - Extra-articular coalition

A - No secondary arthritisB - Secondary arthritis

Type ll - lntra-articular coalitionA - No secondary arthritisB - Secondary arthritis

Fig. 2. Articular Classification System. Classification of tarsal coalitionsbased upon articular involvement. Note that classification can be usedas basis for discussion of surgical treatment.

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Extra-articu lar Coal itionsCalcaneonavicu IarCubonavicular

I ntra-articular CoalitionsTalocalcaneal

MiddlePosteriorAnteriorCombination

TalonavicularCalcaneocuboidNavicu Iocu neiform

Fig. 3. Division of tarsal coalitions into extra-articular and intra-articularcoalitions. Multiple and massive coalitions are usually intra-articularcoalitions and most frequently are associated with degenerativechanges.

Fig. 4. Middle facet talocalcaneal coalition in 34 year old. Note second-ary degenerative changes at talonavicular ioint. This would be

"Adult-llB" coalition in articular classification system.

CLINICAL FINDINGS

Tarsal coalition may be completely asymptomatic andan incidental finding on routine radiographs. ln study-ing23 patients with tarsal coalition, Jack (38) found that5 (22%) were asymptomatic. However, three clinical find-ings: pain, limitation of joint motion, and muscle spasmshould make the clinician suspicious of a tarsal coalition.

Pain is a co/nmon finding in patients with tarsal coali-tions. The pain is usually deep and aching in nature, andis frequently in the area of the tarsal coalition. The pa-tient often can localize the pain to the sinus tarsi,anterolateral ankle, or dorsum of the midfoot. With a

middle facet talocalcaneal coalition, the patient may in-dicate that the pain encompasses the entire rearfoot-localizing the pain to the sustentaculum tali medially andthe sinus tarsi laterally (Fig. 6). lf significant secondaryarthritic changes are present, the pain may be greatestin these latter areas (e.9., pain at the talonavicular jointsecondary to arthritic changes from a talocalcaneal coali-tion). lf the patient is unable to localize the pain, the clini-cian can, in most instances, localize it accurately withfirm palpation.

The onset of the pain is usually insidious, developingafter some unusual activity (e.9., excessive walking, hik-ing, or running) or innocuous trauma (e.9., minor anklesprain). Further, it has been stated that all coalitions areinitially cartilaginous in nature, and eventually ossify.Cowell (41) suggested that different coalitions ossify atdifferent ages and that pain begins as this ossificationprocess occurs. He stated that talonavicular coalitionossifies from ages 3 to 5, calcaneonavicular coalitionossifies from ages 8 to 12, and talocalcaneal coalitionossifies from ages 12 to 16 (4\ ffig. V.

Fig. 5. Calcaneonavicular barchanges are noted. This wouldclassif ication system.

in 1-1 year old. No secondary arthriticbe a "luvenile-lA" coalition in articular

Fig. 6. Patient with middle facet talocalcaneal coalition,to sinus tarsi area.

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Talonavicu lar Coal ition : 3-5 years

Calcaneonavicular Coal itions: 8-12 years

Talocalcaneal Coalition: 12-16 years

Fig. 7. Age when ossification begins in most common tarsal coalitions.Beginning of ossification may correlate with onset of symptomatology.

The pain associated with a tarsal coalition is usuallyaggravated by activity and relieved with rest. Upon ques-tioning, the patient will frequently relate pain when walk-ing over rough, uneven terrain, with prolonged standing,or with athletic activity.

Limitation of subtalar and midtarsal joint motion iscommon with tarsal coalition. Usually the subtalar jointis limited in the direction of inversion. This limitationbecomes even more apparent if peroneal muscle spasmis present.

With tarsal coalition, tonic muscle spasm may occur.It should be clearly understood that this is a tonic mus-cle spasm and NOT clonic muscle spasticity. Theperoneus brevis is usually the muscle most significantlyinvolved. However, spasm of the tibialis posterior, tibialisanterior, and peroneus longus can occur (42,43).

It is theorized that as subtalar joint motion becomespainful the peroneus brevis attempts to guard or restrictthis motion. This tonic spasm occurs much like ab-dominal muscle guarding in a patient with appendecitis.It is a subconscious attempt by the peroneus brevis tolimit painful motion. This spasm is not neurologic innature as in clonic spasticity, but simply an increase intension of the peroneus brevis muscle-tendon unit (i.e.,tonic spasm). The muscle spasm, like pain, is precipitatedby activity and relieved by rest.

Fig.8. Spasm of peroneus brevis observed in inferior-lateral leg in pa-tient with peroneal spastic flatfoot secondary to tarsal coalition.

The peroneus brevis muscle spasm may be intermit-tent or continuous. As the symptoms progress, the mus-cle guarding or tonic spasm generally becomes more in-tense. As the peroneus brevis contracts, subtalar jointmotion is further restricted and the taut tendon can bepalpated and/or observed laterally (Fig. 8). The rearfootwill be maintained in a valgus position with depressionof the medial longitudinal arch and abduction of theforefoot. The rearfoot valgus occurs as this is the "posi-tion of comfort" of the foot. With time and if left un-treated, the deformity will become rnore rigid in nature.ln this manner, tarsal coalition may become associatedwith rigid peroneal spastic flatfoot. Further, significantforefoot supinatus, forefoot varus, and/or changes secon-dary to associated ankle equinus may become apparent.Clinical identif ication of these secondary adaptivechanges is imperative to the development of anappropriate treatment plan (Figs. 9 A-B).

It should be remembered that peroneal spastic flatfootdoes not always occur with tarsal coalition and thatperoneal spastic flatfoot can result from other conditions.Occasionally other muscles may be spastic with a tarsalcoalition. lf other muscles are involved, the foot may notdevelop a pes valgo planus attitude. Simmons (43)

reported a varus position of the heel in a patient witha calcaneonavicular coalition (Figs. 10 A,B). Further,peroneal spastic flatfoot can occur secondary to othercauses includi ng arth ropath ies, inf lam mation, i nfection,and osteochondral fractures (44). These causes may alsobe considered acquired etiologies of tarsal coalition incertain instances.

When evaluating a patient with a tarsal coalitionassociated with restricted motion and/or muscle spasm,a local anesthetic injection in the area of the coalitionor to a proximal nerve segment (e.g., common peronealblock) may provide valuable diagnostic information. Theanesthetic block may relieve the pain and muscle spasmsufficiently to allow a more accurate assessment of jointmotion. This will not only allow direct confirmation ofthe extent of the coalition (i.e., complete versusincomplete), but also can afford information as to thejoint motion quality and quantity. This information maybe helpful if surgery is considered and resection of thecoalition is contemplated.

ROENTGENOGRAPHIC FI NDINGS

Roentgenographic evaluation of a suspected tarsalcoalition should be performed in a systematic, cost-effective manner. In most instances, routine radiographswill allow an accurate diagnosis of tarsal coalition. Moresophisticated studies such as tomography, computedtomography, or magnetic resonance imaging should be

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Fig. 9. Peroneal spastic flatfoot of left foot. Note increased rearfootvalgus and forefoot abductus associated with deformity.

reserved for cases where standard radiographs are in-conclusive, or where one wishes to assess the identifiedcoalition in more detail.

Rad iograph ic Eval uation

When the clinical findings suggest a possible tarsalcoalition, initial routine radiographs (includinganteroposterior, lateral, and medial oblique views)should be obtained. In the majority of cases, theseroutine films will clearly portray a tarsal coalition andconfirm its diagnosis. However, one must have a

thorough appreciation of the normal radiographicanatomy and the radiographic pathology expected withtarsal coalition if one is to use routine radiographs tomaximum benefit. ln this sense, different views will bemore helpful in different coalitions.

As stated earlier, the calcaneonavicular coalition wasfirst radiographically demonstrated by Slomann (7) on anoblique view. This coalition is still most readilyappreciated on the medial oblique view (i.e., lateral

Fig. 10. Cavovarus foot deformity in patient with calcaneonavicular coali-

tion. A. Cavus deformity on lateral view. B. Calcaneonavicular synostosis(i.e., complete coalition) noted more readily on medial oblique view(lateral oblique proiection).

oblique projection), although it may be suggested on an

anteroposterior or lateral view. The connecting barbetween the calcaneus and navicular may be osseous/cartilaginous, fibrous or mixed in nature. Completeosseous union is fairly simple to diagnose (Fig. 10B).

However, an incomplete union can be more difficult. lnthese cases, the calcaneus and navicular are frequentlyin close proximity to one another and their contiguouscortical surfaces appear flattened and irregular like a

pseudarthrosis (Fig. 11).

A talocalcaneal coalition can usually be identified anddiagnosed from a lateral radiograph if the normalradiographic anatomy of the subtalar joint is wellunderstood (Fig. 12A). The middle and posterior facetsof the subtalar joint can be visualized on a properly takenlateral view. The anterior facet cannot be visualizedbecause its obliquity causes it to be obliterated by otherosseous structures (39,45). A talocalcaneal coalition in-volving the middle or posterior facets may be directlyvisualized on a lateral radiograph as absent or diminishedjoint space. lt may only be suggested if it involves theanterior facet.

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Fig. 11. lncomplete calcaneonavicular coalition noted on medial ob-lique view (lateral oblique projection). Note that adjacent surfaces ofnavicular and calcaneus resemble pseudoarthrosis.

When coalition of the subtalar joint occurs, it ispredominantly of the middle facet. The commonradiographic hallmarks of a middle facet talocalcanealcoalition seen on a lateral radiograph are: 1) a halo signrepresenting absence or diminished visualization of themiddle facet with enhancement of the sustentaculumtali;2) narrowing of the posterior facet of the subtalarjoint with loss of subtalar joint clarity; 3) talonavicularjoint beaking; and 4) flattening of the lateral talarprocess (Fig. 12B) (30,34). These findings may also be seenwith varying degrees in coalitions involving the anteriorand posterior facets.

Harris and Beath views (i.e., axial or "ski jump" views)may be performed to obtain additional information asto the status of the middle and posterior facets of thesubtalar joint. lf a complete osseous coalition is present,the involved facet(s) will not be visualized. lf anincomplete coalition is present, the facet(s) involved willusually demonstrate osseous irregularity, joint space nar-rowing, and facet obliquity. ln the normal foot, theposterior and middle facets are parallel to the groundand to one another (Fig. 13A). lf a facet is angulated morethan 25 degrees from the ground or its neighboring facet,a talocalcaneal coalition can be strongly suspected(a1XFig. 13B).

Isherwood views can also provide information on atalocalcaneal coalition. Unfortunately, the views requireexact positioning of the patient and are very difficult toperform properly (46-48).

Further, neutral position radiographs, radiographstaken while performing the Hubscher maneuver, andlateral stress dorsiflexion ankle radiographs may provideevidence as to the flexibility of the deformity. In com-plete talocalcaneal coalitions, the deformity will fre-

Fig. 12. Lateral radiographic views of: A. Normal right foot. Pointersdelineate middle and posterior facets of subtalar joint. B. Right footwith middle facet talocalcaneal coalition. Note four classic features ofsuch coalition:1) halo sign (small pointers-most inferior),2) Loss ofsubtalar joint clarity (large pointers), 3) Talonavicular loint beaking (smallpointers - most superior), and 4) Flattening of lateral talar process(arrow).

quently result in a rigid pes valgo planus deformitywhether or not it is associated with peroneal musclespasm. The subtalar joint may be placed in its neutralposition and a lateral radiograph taken. No change in thetalocalcaneal relationship will be noted if the deformityis rigid.

Another test for flexibility is the Hubscher maneuver.This maneuver involves passive dorsiflexion of the halluxwhile the patient stands in a normal relaxed position.When the hallux is dorsiflexed, the medial strand of theplantar fascia and flexor hallucis longus are tightened.ln the flexible pes valgo planus foot deformity, themedial longitudinal arch will increase in height and therearfoot will supinate. While holding the hallux in a dor-siflexed position, a lateral radiograph can be takenattempting to demonstrate an increase in the mediallongitudinal arch and a change in the lateral talocalcanealrelationship representing rearfoot supination (i.e., adecrease in the lateral talocalcaneal angle) (Fig. 1a A-C).

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Fig. 13. A. Normal Harris and Beath view of right foot. Note that mid-

dle and posterior facets (pointers) are parallel with ground and one

another. Middle facet is slightly superior to posterior facet in normal

foot. B. Abnormal Harris and Beath view in patient with middle facet

talocalcaneal coalition of right foot. Note angulation of middle facet

with weight-bearing surface and posterior facet.

Fig. 14. A. Lateral weightbearing view of left foot in patient with pes

valgo planus deformity. B. Lateral view of same foot with Hubscher

maneuver being performed. C. While Hubscher maneuver is per-

formed, note change in talocalcaneal relationship. Lateral talocalcaneal

angle has decreased. This is flexible collapsing pes valgo planus

deformity.

lf this does not occur, the deformity is rigid in nature(4e).

Finally, a lateral stress dorsiflexion view of the anklecan be taken. This should place a dorsiflexory force uponthe subtalar and midtarsal joints. ln a flexible deformi-ty, this will cause pronation of the subtalar joint and the

lateral radiograph should demonstrate a decrease in themedial longitudinal arch and a change in thetalocalcaneal relationship representing rearfoot prona-tion (i.e., an increase in the lateral talocalcaneal angle)(Fig. 15A-B). Further, any osseous impingement of thetalus and tibia may be documented with this view. This

should be differentiated from the talonavicular beakingassociated with a tarsal coalition (50).

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Fig. 15. A. Lateral weight-bearing view of right ankle and rearfoot. B.

Lateral stress dorsiflexion view of same ankle and rearfoot. No changein talocalcaneal relationship is noted. lf deformity were flexible, an in-crease in lateral talocalcaneal angle would be noted. Thus, this is a rigiddeformity, which was subsequently found to be due to talocalcanealcoalition on computed tomography images.

Talonavicular and other rarer coalitions can usually beeasily seen on standard radiographs. The anteroposteriorand lateral views will, in most cases/ clearly demonstratethese coalitions (Fig. 16). lt should be remembered thatboth feet need to be evaluated for other coalitions whenany tarsal coalition is found. This information may sug-gest a complex malformation (Fig. 1)and will be helpfulin the construction of a treatment plan.

Routine radiographs may also be used to evaluate thefoot for arthritic changes secondary to the tarsal coali-tion. These secondary changes include joint beaking(e.9., talonavicular or calcaneocuboid joint beaking),osteoarthritis with diminished joint space, and secondaryadaptive changes (e.g., ball-and-socket ankle joint in atalocalcaneal coalition or increased joint motion at thenaviculocuneiform joint in a talonavicular coalition). Theextent of these secondary arthritic or degenerativechanges f requently determines the prognosis and treat-ment plan.

Tomograph ic/Cross-Sectional Eval uation

Standard tomography, computed tomography, andmagnetic resonance imaging offer the ability to obtainmulti-planar cross-sectional images of the foot withminimal bony overlap (39, 51-54) (Fig. 1n. Thesemodalities should be reserved for cases in whichradiographs are inconclusive, for evaluation of a coali-tion of the anterior facet of the subtalar joint, and/or forcases in which the treating physician desires more de-tailed information involving a specific coalition (e.g., aneed to determine more specifically the size and tissue

Fig. 16. Anteroposterior (A) and lateral (B) views of talonavicular coali-tion. Note rounding and increased joint space of naviculocuneiformjoints.

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type of a coalition). However, one should avoid theexpensive pitfall of believing that one of these modalitiesis always necessary. Most tarsal coalitions can bediagnosed by clinical examination combined with tradi-tional radiographs.

Special ized Stud ies/Eval uation

Radionuclide scanning and arthrography have alsobeen used in the diagnosis of tarsal coalitions. A bonescan obtained with Technitium-99 methylene methylenediphosphate (Tc-99) may be sensitive to the presence ofa tarsal colition (Fig. 18). This sensitivity is secondary tothe bone activity generated by the abnormalbiomechanical stress and arthritic changes occurring inthe area of the coalition. Since many conditions cancause similar activity, a Tc-99 bone scan is nonspecificfor tarsal coalition and should only be used as a screen-ing study (55,56). Arthrography of the talocalca-neonavicular joint can be used to detect a talocalcanealcoalition when routine radiographs are inconclusive (57).

However, the use of tomographic techniques is moreaccurate and noninvasive.

TREATMENT

Not all tarsal coalitions are symptomatic. Also whensymptomatic, not all coalitions necessarily remain so.Therefore, in most cases, conservative treatment shouldinitially be attempted. lf this proves unsuccessful, thensurgical intervention may be considered.

tig. 17. Computed tomography coronal plane image of middle facetsynostosis of talocalcaneal foint (arrow). Note sinus tarsi and posteriorfacet are clearly visible.

Conservative Treatment

Conservative therapy is directed towards restrictingsubtalar and midtarsal joint motion, thereby reducingpain and muscle spasm. This may be combined withphysical therapy and anti-inflammatory medication as

needed.

Subtalar and midtarsal joint motion may be effective-ly limited with shoe modifications, padding, orthoticdevices, or casting. Shoe modifications may include a

Thomas heel, medial heelwedge, or longer medial heelcounter. Padding in the shoe gear may include a heelwedge or medial longitudinal support. Orthoses shouldbe specifically constructed to limit subtalar joint motion.A neutral position device with a long rearfoot post or anorthotic posted in valgus may prove to be beneficial. lfthese modalities fail or if the patient has significant symp-tomatology, a soft cast, strapping, or below-knee walk-ing cast may be considered. If desired, these may be ap-plied after a local steroid injection to the area of the coali-tion. The below-knee cast is applied with the ankle andsubtalar joints in their neutral positions and kept intactfor a period of 3 to 6 weeks. ln more severe cases, orif initial casting fails, a non weight-bearing cast may beattempted. Jayakumar and Cowell (58) reported thatapproximately 25 to 30% of their patients improved withcasting.

Symptomatic relief of coalitions may be afforded byphysical therapy or anti-inf lammatory medication.Therapeutic modalities such as heat, warm soaks, paraf-fin baths, or whirlpool baths may be beneficial. Kendrick(59) suggested manipulation under anesthesia as a possi-ble treatment, but this has not been supported. Localinjections of steroid and/or local anesthetic may provide

Fig. 18. Technitium-99 bone scan (thirdtalocalcaneal coalition. Note activity in areawell secondary to biomechanical stress.

phase) of middle facetof talonavicular joint as

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relief. Further, injection of a local anesthetic agent intothe area of an incomplete coalition may allow increasedmotion. This can be extremely helpful when evaluatinga patient for a coalition and determining a possiblesurgical treatment plan. Oral anti-inflammatory medica-tion may also provide symptomatic relief.

Surgical Treatment

Surgical treatment is essentially confined to eitherresection of the coalition or fusion of the involved jointcomplex. However, significant controversy exists as tothe indications and results to be expected with these twodiverse surgical approaches. For this reason, the authorproposes a new classification system (Fig. 2)which maybe used as a framework for the construction of anappropriate treatment plan. The classification system isnot meant to be all inclusive, but considers severalimportant parameters used in the development of anytreatment regime - patient age, articular involvement, andextent of secondary arthritic changes. Certainly, otherfactors not included in the classification system will needto be considered.

Juvenile - lA

Traditionally, extra-articular coalitions, such as a calca-neonavicular coalition, have been considered moreamenable to surgical resection. This is particularly truewhen no secondary degenerative changes have oc-curred. Thus, in the younger patient with an extra-articular coalition and minimal secondary arthriticchanges, resection arthroplasty is generally tlre pro-cedure of choice.

lf the coalition is a calcaneonavicular bar, the classicprocedure, as first described by Badgely (8), is excisionof the coalition with interposition of the extensordigitorum brevis muscle belly. The approach for this pro-cedure is through a lateral curvilinear or Ollier-type in-cision beginning over the lateral calcaneus/sinus tarsiarea and extending medially to the lateral aspect of thetalonavicular joint (Fig. 19A).

Blunt dissection is then carried through the sub-cutaneous layer with hemostasis obtained as necessary.The origin of the extensor digitorum brevis is thenreflected off the calcaneus and retracted distally (Figs.198-C). The calcaneonavicular bar is generously resectedwith as much bone as possible being removed (Figs.19D-E). The extensor digitorum brevis muscle belly isthen sutured into the defect (Figs. 19F-G). The suture maybe placed in the muscle and then directed plantar-medially and sutured over a button on the plantar-medialaspect of the foot (Figs. 19H-l). Alternatively, an internal

70

Fig. 19. Extensor digitorum brevis arthroplasty. A. Skin incision. B. Ex-

tensor digitorum brevis muscle prior to reflection. C. Extensor digitorumbrevis retracted distally after reflection from calcaneus. Note calca-

neonavicular bar is now visible. D. Resection of coalition. E. Defect be-

tween calcaneus and navicular. F. Suture placed in extensor digitorumbrevis for insertion into defect. C. Muscle inserted into defect. H. Suturepassed through plantar-medial aspect of foot. l. Suture tied over but-ton. J. Anatomic closure with insertion of TLS drain and applicationof steristrips.

suture technique, where the muscle is anchored to softtissue or bone/ may be employed.

A large closed suction drain is inserted, and anatomicclosure performed (Fig. 19J). Postoperatively, a below-knee non weight-bearing cast is applied for 4 to 6 weeks.The cast may be split or bivalved after 2 to 3 weeks andsubtalar and midtarsal joint range of motion exercisesbegun. Weightbearing is initiated after approximately 6

weeks.

Many authors have reported good success with thisprocedure (58, 60-65). The most frequent postoperativeproblem reported has been varying amounts of recur-rent bone growth of the bar. This has generally not beenfound to be a problem if a generous resection of the barwas initially performed. Despite this, several suggestedmodifications have been proposed, including thecoagulation of the bone ends (40), the use of bone wax

71

on the bone ends (39), the insertion of adipose tissuebetween the bone ends instead of the muscle belly(40,44), or the insertion of a silicone implant between thebone ends instead of the muscle belly (66).

ln similar fashion, other more rare extra-articular coali-tions without secondary degenerative changes, such asa cubonavicular coalition, should offer similar hope offavorable results following resection (39,67).

Several authors (68,69) have discussed the possibilityof performing a varus-producing osteotomy of thecalcaneus. Dwyer (69) felt that the valgus position of therearfoot, commonly seen with a tarsal coalition, pro-duced an "oblique strain of the ligaments" in the rear-foot and ankle with resultant pain. He suggested anopening wedge calcaneal osteotomy with a bone graftinserted through a lateralapproach. Cain and Hyman (68)

reported success in treating coalitions with a similar pro-cedure. lnstead of an opening osteotomy, Cain andHyman performed a closing osteotomy through a medialapproach. None of these authors suggested resection ofthe coalition along with the calcaneal osteotomy. Cer-tainly, the osteotomy alone would seem of limitedbenefit as demonstrated by orthotic devices which main-tain the heel in a varus position, and yet, afford onlyminimal relief of symptoms. However, if significant heelvalgus is present, a varus-producing calcaneal osteotomycombined with resection of the coalition may be of somebenefit.

Juvenile IB

An extra-articular coalition with secondary arthriticchanges is less amenable to simple surgical resection.However, in the younger patient it should still be stronglyconsidered with arthrodesis presented as a possiblefuture operation.

With a calcaneonavicular coalition, significantdegenerative changes may occur over time. Usually, thetalonavicular joint will demonstrate the most apparentchanges. ln the younger patient with mild degenerativechanges, extensor digitorum brevis arthroplasty mayagain be attempted. However, the patient and parentsshould be told that arthrodesis may need to be per-formed in the future. With more significant degenerativechanges, triple arthrodesis is the procedure of choice(8,11,70).ln cases where triple arthrodesis is to be per-formed, the coalition may be left intact if complete.However, if the coalition is incomplete or if significantpositional abnormalities exist, the coalition should beresected to obtain optimal postoperative position andfusion. Triple arthrodesis is usually performed afterosseous maturity.

Juvenile llA

Although extra-articular coalitions are generallyreasoned to be more amenable to resection, intra-articular coalitions are traditionally considered an indica-tion for arthrodesis. The exception to this premise mightbe the "Juvenile IlA" coalition-an intra-articular coali-tion which occurs in a younger patient with minimal orno secondary degenerative changes. If small enoughand/or if incomplete in nature, this coalition may beamenable to resection arthroplasty. lt should beremembered that future arthrodesis will many times benecessary.

A common example would be a middle facet coalitionof the subtalar joint (Figs. 20A-B). Typically, resection ofthis coalition leaves a defect and an irregular area in anarticular facet of a major weight-bearing joint. However,several authors have described resection of the coalitionwith or without the interposition of fat grafts, and havereported satisfactory results (40,58,65,71). We haveattempted resection of a middle facet talocalcaneal coali-tion with the insertion of a subtalar joint arthroereisisto maintain the joint space (Figs. 21 A-D). More recently,this was similarly reported by Lepow and Richman (72)

with success.

Another example where resection might be preferable,is the posterior facet talocalcaneal coalition secondaryto a fractured Stieda's process or os trigonum. Surgicalresection of the coalition and/or os trigonum may leadto a satisfactory functional result (18).

Again, several reports (68,69) have indicated that varus-producing osteotomies of the calcaneus may afford reliefof symptoms in tarsal coalitions without significantsecondary arthrosis. These procedures may be a usefuladjunct if concomitant resection of the coalition is

attempted, but should not be performed alone.

ln those cases with significant coalition involvementor in cases of failed resection, arthrodesis is the pro-cedure of choice. ln most instances, triple arthrodesisis preferred. With talocalcaneal coalitions involving themiddle facet and without secondary arthritic changes,debate continues as to the preferred arthrodesis -

isolated subtalar joint arthrodesis or triple arthrodesis.The author supports, and recent evidence (73) suggests,that isolated subtalar joint arthrodesis generally providesa superior functional result (Figs. 22 A-B). Triplearthrodesis should be reserved for cases where the coali-tion, although not associated with secondarydegenerative changes, is demonstrating significant struc-tural abnormalities (e.g., profound forefoot varus/ rear-foot valgus, or equinus). ln such cases, triple arthrodesis

72

Fig, 20. A. Talocalcaneal coalition of anterior and middle facets of left foot approached through medial incision. B. Same foot after resection of coalition.

A

Fig.21. A. Preoperative lateral view of left foot in 8 year old patientwith middle facet talocalcaneal coalition. B, C. lnsertion of subtalar ar-

throereisis after resection of coalition. D. Postoperative lateral view offoot. Note improved talocalcaneal relationship.

DB

73

will be necessary to obtain a structurally acceptableforefoot to rearfoot relationship.

Juvenile llB

An intra-articular coalition with moderate to severesecondary arthritic changes is optimally treated with a

triple arthrodesis after osseous maturity (Figs. 23 A-B).

Adult lA

ln the adult, one generally considers arthrodesis morestrongly than in the child. When the coalition is extra-articular and no secondary arthritic involvement is noted,resection arthroplasty may be considered.

Adult lB

When the extra-articular coalition in the adult is

associated with secondary degenerative changes,arthrodesis is preferable. ln most cases, triple arthrodesiswill be indicated.

fig.22, A. Preoperative lateral radiographic view of .19 year old patientwith middle facet talocalcaneal coalition. Note nrinimal secondary ar-thritic changes. B. Postoperative lateral view after isolated subtalar iointarth rodesis.

Adult ltA

Unlike the juvenile patient, resection of an intra-articular coalition should generally not be considered inthe adult. lsolated arthrodesis of the involved joint maybe performed if no secondary arthritic changes are noted(Figs. 22A-B). Triple arthrodesis may also be considered,and is certainly preferable if one wishes to derotate theforefoot to correct a significant forefoot varus orsupinatus deformity.

Adult llB

When an intra-articular coalition is associated withsign ificant secondary arthritic changes, triple arth rodesisis the procedure of choice (Figs. 23A-B).

Thus, the articular classification system can be con-sidered a surgical classification. ln this sense, it providesa superior method of grouping tarsal coalitions. Basedupon this, recommended procedures and the report oflong-term results can be more accurately related (Fi1.24.

Fig. 23. A. Preoperative lateral radiographic view of 15 year old patientwith middle facet talocalcaneal coalition. Note arthritic changesincluding talonavicular and calcaneocuboid joint beaking. B. Postop-erative lateral view after triple arthrodesis.

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luvenile - lAResection with interposition of EDB

muscleResection with interposition of adipose

ti ssueResection with varus-producing

calcaneal osteotomyResection with insertion of implantVarus-producing calcaneal osteotomy

alone

fuvenile - lB

Resection with interposition of EDB

muscleResection with interposition of adipose

tissueResection with varus-producing

calcaneal osteotomyResection with insertion of implantVarus-producing calcaneal osteotomy

aloneTriple arthrodesis

fuvenile - IIA

Resection aloneResection with interposition of adipose

ti ssueResection with interPosition of

arthroereisisResection with varus-producing

calcaneal osteotomyVarus-producing osteotomY aloneI solated/si ngle arth rodesisTriple arthrodesis

Iuvenile - llB

Triple arthrodesis

Adult - lA

Resection withmuscle

Resection withtissue

interposition of EDB

interposition of adipose

Resection with varus-Producingcalcaneal osteotomY

Resection with insertion of implantVarus-producing calcaneal osteotomy

aloneTriple arthrodesis

Adult - lB

Triple arthrodesis

Adult - llA

I solated/si ngle arth rodesisTriple arthrodesis

Adult - lllB

Triple arthrodesis

Fig.2a. Possible surgical procedures based on articular classificationsystem. Note that procedures listed in bold type are currentlyrecommended.

SUMMARY

An in-depth discussion of tarsal coalitions has beenpresented, including the introduction of a surgicalarticular classification system with specific references totreatment. A working knowledge of the clinical androentgenographic findings is imperative to the construc-tion of a logical treatment PIan.

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