Sakellariou & Claridge (1998) - Tarsal coalition- aetiology, diagnosis and treatment.pdf

Current Orthopaedics (1998) 12, 135-142 © 1998 Harcourt Brace & Co. Ltd

Foot and ankle

Tarsal coalition: aetiology, diagnosis and treatment

A. Sakellariou, R. J. Claridge

INTRODUCTION AETIOLOGY

Tarsal coalition was probably first described by Buffon in 1769. Subsequently, the discovery of a variety of coalitions and their characterizations has been aided by the evolution and refinement of plain radiology and, more recently, by computerized tomography (CT) and magnetic resonance imaging (MRI).

Tarsal coalition refers to a condition characterized by a restriction or absence of hindfoot motion, secondary to an abnormal union between two or more bones of the hindfoot or, less commonly, the midfoot. Coalitions may be cartilaginous (synchondrosis), fibrous (syndesmosis), or bony (synostosis) and the condition may be congenital or acquired. Often asymptomatic, the congenital form may go unrecognized until such time as a minor sprain or hindfoot trauma leads to its incidental diagnosis. Once symptomatic, children and adolescents are those usually affected, although presentation in young adults is fairly common. Following presentation, however, tarsal coalition may continue unrecognized as the cause of chronic pain or discomfort in the hindfoot, often leading to incorrect diagnosis and inappropriate treatment.

The purpose of this article, therefore, after outlin- ing the aetiology, is to focus on the accurate diagnosis and management of tarsal coalition, and to discuss aspects of its treatment that remain controversial.

Anthony Sakellariou BSc MB FRCS(Orth), Visiting Fellow; Richard J. Claridge MD FRCS(C), Foot and Ankle Clinic, Department of Orthopaedics, Mayo Clinic Scottsdale, 13400 East Shea Boulevard, Scottsdale, Arizona 85259, USA.

Correspondence to: Mr Anthony Sakellariou, West Cottage, Walton Manor, Walton-on-the-Hill, Surrey KT20 7SA, UK.

Heredity

Two theories have been proposed for the aetiology of tarsal coalition. The first of these arose from the observation that accessory ossicles are often noted at the sites of some coalitions. This led to the suggestion that these accessory bones gradually become ossified into a bony union, resulting in coalition. The exis- tence of the anomaly in fetuses, however, does not support the theory of accessory ossification. The theory currently most favoured is that the condition represents a failure of segmentation of primitive mes- enchyme. The observation of familial occurrence suggests that this condition is inherited, and the finding in some cases of involvement of subsequent generations further suggests a dominant type of inheritance. ~,2 Further work in this field by Leonard in 19743 has now led to the general acceptance that tarsal coalition is usually due to an inherited autosomal dominant disorder with variable penetrance.

The overall prevalence of tarsal coalition in the general population is reported to be in the region of 1%. 2~ However, as many coalitions remain asymptomatic in life, the actual figure may be higher. Race does not appear to be significant and, of those affected, between 50 and 60% have the condition bilaterally? '3'5 The relative incidence of the two most common types of coalition is almost equal (talocalcaneal 48%, calcaneonavicular 44%), and together they account for the great majority of coalitions? Of the talocalcaneal coalitions, most involve the middle facet; posterior and anterior facet subtalar coalitions are much less commonJ ,7 Talonavicular coalitions account for only 1% and calcaneocuboid about the same. Other types of coalition make up the remainder, but individually are very rareY Some patients

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136 Current Orthopaedics

may have more than one coalition in the same foot and a high percentage are bilateral.

Although failure of segmentation is the most common cause of tarsal coalition, acquired 'coalition' of any of the tarsal bones may occur secondary to trauma (intra-articular fracture), inflammatory arthropathy, neoplasm or even osteonecrosis, resulting in a rigid painful flatfoot. 74

Pathomechanics

The subtalar joint complex consists of the subtalar joint itself and the transverse tarsal joint, consisting of the talonavicular and calcaneocuboid joints. This complex functions as a torque converter of the forces transmitted to the foot, from the tibia. The position of the subtalar joint is critical in determining the degree of mobility at the transverse tarsal joint in that, when the hindfoot is everted into a valgus position, the transverse tarsal joint is unlocked and the forefoot is flexible. Conversely, when the hindfoot is in varus, the transverse tarsal joint is rigid. 9 Restriction of motion in any one of these joints, therefore, by a coalition, limits motion of the others and subjects them to higher stresses. These abnormal stresses, plus a reduced adaptive ability, together result in a predispo- sition to ankle instability as well as pain and inflam- mation, which eventually lead to joint degeneration. However, since patients do not in general become symptomatic before early adolescence, it is thought that the mild restriction of motion caused by a cartilagenous coalition is not enough to produce symptoms. With increasing age, though, as the cartilagenous coalition ossifies, significant restriction in hindfoot movement occurs, leading to the appear- ance of symptoms. Should total ossification occur, subtalar motion becomes markedly restricted. As mentioned, many adults with this condition remain asymptomatic. These individuals are generally thought to have enough compensatory motion in adjacent joints to have protected them from develop- ing symptoms.

DIAGNOSIS

Clinical presentation Patients become symptomatic as they lose motion in the foot due to ossification of the coalition, and due also to the usual increase in activity typical of child- hood and early adolescence. Talonavicular coalitions ossify in patients from 3 to 5 years of age, calcaneonavicular coalitions between the ages of 8 and 12 years, and talocalcaneal coalitions between the ages of 12 and 16 years. 7 Althot~gh these figures represent the typical age of presentation of the different coalitions, this is certainly not always the case and presentation later in the second and third decade of life is not uncommon, especially with talocalcaneal coalition.

A history of intermittent, vague, aching, hindfoot pain over several months, which is usually not very well localized, and often aggravated by activity or pro- longed standing, is the usual presenting symptom. Although the onset is often insidious, some patients may have been symptom-free until a relatively trivial 'ankle sprain' or sudden increase in activity renders them symptomatic. ~° Many patients give a history of recurrent sprains and of a sensation of instability on uneven ground which can lead to misdiagnosis.

A large proportion of patients with tarsal coalition are asymptomatic 3,7 and the diagnosis is made inciden- tally on routine clinical examination of the foot. Many will remain asymptomatic.

Physical examination

This should be conducted with the patient both standing, and seated with the legs and feet dependent. Patients can present with a painful flatfoot (planoval- gus) deformity which is to be distinguished from the painless flexible flatfoot commonly found in both children and adults. The hindfoot is often held in valgus resulting in an increased tibiocalcaneal angle. Accom- panying forefoot abduction can give rise to the 'too many toes' sign more typical of posterior tibial tendon pathology (Fig. 1). Nevertheless, it is important to note that the foot can appear entirely normal despite limited subtalar motion or, rarely, coalition can present with a cavovarus deformity. Typically, however, they do not display normal hindfoot inversion on single stance heel rise and have absent or markedly reduced subtalar motion when tested with the foot plantigrade. Because it is difficult to demonstrate subtalar motion accurately, the 'heel-tip' test has been used to evaluate restricted tarsal motion. H The patient stands while the examiner supinates the foot by raising the medial border of the forefoot. The lateral border of the foot and heel remain flat on the floor. Since supination of the foot causes external rotation of the tibia, this will be visible by external rotation of the patella. Although both talocalcaneal and calcaneonavicular coalitions can eliminate subtalar motion and produce valgus malalignment of the

Fig. 1 Valgus hindfoot on the right as demonstrated by an increased tibiocalcaneal angle. Note also the presence of the 'too many toes sign'.

Tarsal coalition 137

hindfoot, the former is more likely to do so. Symptomatic tarsal coalition with painful limitation of inversion is also invariably accompanied by point tenderness laterally, deep in the sinus tarsi, or occasionally over the site of the coalition. The latter sign is more common in coalitions that are incomplete or cartilaginous.

Very occasionally, a patient may present with the classic 'peroneal spastic flatfoot' in which the hindfoot is held in rigid valgus and the forefoot is abducted due to peroneal muscle spasm. Despite the term 'peroneal spastic flatfoot', patients do not have spasticity; rather, as a result of limited subtalar motion and pro- gressive hindfoot valgus, the peroneal muscle-tendon unit shortens adaptively. When inversion is attempted, the shortened peroneal muscles contract to protect the painful subtalar joint, resulting in the clinical finding of protective peroneal spasm, not spasticity.

Peroneal spasm with a flatfoot deformity can also arise as a result of degenerative or inflammatory pro- cesses within the midfoot or hindfoot. Thus, although this is the most impressive presentation of tarsal coalition, not only is it rare, but it is also not pathognomonic. Use of the term 'peroneal spastic flatfoot' synonymously with tarsal coalition is, therefore, inappropriate. The term 'rigid flatfoot' describes the condition more accurately.

Finally, careful examination should help exclude other conditions that can also give rise to a painful rigid flatfoot. Deformity and previous skin trauma should raise the suspicion of previous injury to the talus and/or calcaneus, and erythema with effusion and diffuse synovial swelling, especially if involving other joints too, may suggest an inflammatory arthropathy such as rheumatoid arthritis or Reiter's syndrome.

Imaging Plain radiographs

Routine radiographs consisting of weight-bearing AP and lateral views, as well as a 45 ° oblique view, are

used to screen for tarsal coalition. Although coalitions are often not identified on these views, they remain essential as they can provide numerous clues as to their presence. They are also useful in delineating possible coexistent pathology or joint degeneration as well as identification of some of the rarer types of coalition.

The AP view of the foot can demonstrate the rare talonavicular and calcaneocuboid coalitions, and an AP projection of the ankle can demonstrate the presence of a 'ball-and-socket' articulation, which is an uncommon secondary change associated with any tarsal coalition.

The standing lateral projection is the most useful in that both primary and secondary signs of coalition may be evident on this view. Narrowing of the posterior subtalar joint space, failure to visualize the middle subtalar joint and the more recently described 'C-sign', which is a C-shaped line formed by the medial outline of the talar dome and the inferior outline of the sustentaculum tali, ~2 are considered primary signs. Of the secondary signs 'talar beaking' is the most significant (Fig. 2). This periosteal traction spur of the superoanterior surface of the talar head at the talonavicular joint is secondary to abnormal motion of the tarsal complex and is not regarded as a sign of degenerative change. 5,6,1°,~3,14 Other secondary signs of tarsal coalition on the lateral radiograph include blunting of the lateral process of the talus and concave undersurface of the talar neck. Not all of these signs are necessarily present at one time and none is pathognomonic. However, they should alert the examiner to the possibility of tarsal coalition. The uncommon posterior facet coalition may also be visu- alized on the lateral radiograph. This is demonstrated by a bony mass in the area of the os trigonum, accompanied by talar beaking. A fairly consistent sign of calcaneonavicular coalition on the lateral radiograph is the presence of a long thin extension of the anterior process of the calcaneus toward the navicular, known as the 'anteater nose' sign ~5 (Fig. 3).

The 45 ° oblique view best demonstrates a calcaneonavicular coalition (Fig. 4). Bony coalitions are

Fig. 2 Weight-bearing lateral projection of a talocalcaneal coalition (medial subtalar), showing several radiological signs of tarsal coalition. A large talar beak is apparent on the dorsum of the talar head (white arrow). The posterior facet is narrowed (three small black arrows) and there is blunting of the lateral process of the talus (curved black arrow). Also note the C-sign (outlined by white arrowheads), typical of a subtalar coaIition.


Fig. 3 Weight-bearing lateral radiograph of a calcaneonavicular coalition demonstrating elongation of the anterior process of the calcaneus (arrow) - the 'anteater nose sign'. A talar beak is also present.

easily noted. Secondary signs on this view suggestive of fibrous or cartilaginous calcaneonavicular coalition include proximity of the calcaneus to the navicular, irregularity of the cortical surface of the navicular at the site of coalition, and flattening of the calcaneus as it approaches the navicular.

If a coalition is suspected clinically and not demonstrated on the initial radiographs, the axial ('ski-jump') view of the hindfoot, first described by Korvin z6 and later popularized by Harris and Beath ~ can be obtained. This is taken with the patient standing on the cassette, bending forward at the ankle about 10 °. The X-ray beam is then directed from behind downward and forward through the heel and subtalar joint at 45 ° to the vertical. In the normal foot, this view will show both the middle and posterior talocalcaneal facets. These are oriented in a parallel fashion, the medial facet being located above that of the posterior (Fig. 5). As middle facet coalitions are the most common site of talocalcaneal coalition, abnormalities are usually seen on the medial side. If a bony coalition is present, the joint line is obliterated. If the coalition is cartilaginous or fibrous, it may be difficult to appreciate. However, irregular and/or sclerotic facet surfaces, and loss of the parallel orien- tation of the two facets are strong evidence of coalition, even if the facet appears open ~,68,1~ (Fig. 5).

Anterior facet coalitions are quite rare and much more difficult to visualize with plain radiography. Tomographic examination of the suspect region, as described by Conway and CowelP has, until relatively recently, been used to detect anterior talocalcaneal coalition. CT however, has superseded tomography as

Fig. 4 (A) Pre-operative 45 ° oblique radiograph of a fibrous calcaneonavicular coalition; (B) 45 ° oblique view of same patient, three months following calcaneonavicular bar resection.

an imaging option and, in most cases, the Harris axial view. CT should now be considered part of the routine radiological work-up of suspected tarsal coalition together with the standard 3-view foot series.

Computerized tomography

CT is now regarded as the gold standard for imaging of talocalcaneal coalitions? 7-2° It is also a useful tool for surgical planning because of its ability to demonstrate both the nature and cross-sectional area of the coalition (Fig. 6), as well as the presence and extent of any degenerative arthritis present in the joints. For the coronal views, the patient lies supine with the hips and knees flexed and feet plantarflexed 20 ° at the ankles. The transverse plane views are said to be appropriate for the rare talonavicular and calcaneocuboid coalitions. CT can be used for calcaneonavicular coalitions, but is not as helpful as for talocalcaneal coalitions and the plain 45 ° oblique radiograph remains the best method of detecting this type. 17,18

Bone isotope scanning

Radionucleotide scanning, using technetium-99, has been used to aid the diagnosis of symptomatic tarsal coalition. 21 It could potentially provide important


Fig. 5 Harris-Beath axial projection of the calcaneus showing a fibrous right middle facet subtalar coalition. Note the obliquity of the middle facet on the right, compared to its opposite on the left, which is horizontal and parallel to the posterior facet lying below it.

Fig. 7 A Tl-weighted, gradient echo sequence MR image of a fibrous medial subtalar coalition.

Fig. 8 Use of ankle braces such as this, which can be worn over a sock and inside any lace-up shoe or trainer can, in patients with symptomatic coalition, provide relief of symptoms by reducing subtalar motion.

Fig. 6 Coronal section CT scan of a unilateral osseous medial subtalar (talocalcaneal) coalition.

localizing information in difficult cases where it may be used as a screening procedure. ~9 Howevel; because of its lack of specificity and detail, its place in the investigation of tarsal coalition should be considered as limited.

Magnetic resonance imaging

The Tl-weighted sequence of the MRI (Fig. 7) has been reported to be more sensitive than CT in the identification of fibrous or cartilaginous coalitions? °,= This would be advantageous in the investigation of the non-ossified coalitions of children and adolescents potentially missed by CT. Should MRI become as easily available as CT is now, then this may become the investigation of choice.

TREATMENT

For asymptomatic tarsal coalitions, where the diagnosis is incidental, especially with children, simple observation is a reasonable course of action. Many will remain asymptomatic into adulthood. Such patients do not require treatment.

Nonoperative treatment

Symptomatic coalitions deserve conservative management initially, irrespective of the type of coalition, although talocalcaneal coalitions are much more likely to respond than calcaneonavicular bars, or the rarer talonavicular coalitions. Treatment should include activity modification, anti-inflammatory med- ication and shoe modifications and/or orthoses 5,9 aimed at reducing stress across the subtalar joint and supporting the foot. A medial heel wedge, Thomas heel, or medial arch support designed to help decrease subtalar motion can be helpful. The authors also pre- scribe a proprietary 'airsplint' ankle brace, which may also provide some increased subtalar stability, both mechanically and through increased proprioceptive feedback (Fig. 8). Boots or 'high-top' shoes are an alternative where the symptoms are mild and compliance likely to be suboptimal, as in the adolescent or young adult. For more severe pain, stiffness, and deformity, or failure to respond to the more conservative treatment options, immobilization in a short leg walking cast in neutral for 6 weeks often results in resolution of symptoms. On removal of the cast, an orthotic shoe insert or ankle brace should be pre- scribed. A second period of casting may be necessary if symptoms are not completely resolved after the first 6 weeks, or recur shortly after. Should symptoms be relieved in the cast but recur on removal, then a rigid


custom-made ankle-foot orthosis (AFO) may be considered, depending on the likely compliance and expectations of the patient. If two periods of casting fail to achieve resolution of symptoms, however, then surgery should be considered.

Operative treatment

Should a patient fail a trial of nonoperative treatment, the operative choice is essentially one between resection of the coalition or arthrodesis (although cal- caneal osteotomy has been reported), 23 and is deter- mined by factors such as the age of the patient, type and extent of coalition, and the presence or absence of degenerative changes in the affected and/or adjacent tarsal joints. Should an arthrodesis be deemed necessary, the choice should be between an isolated subtalar or triple arthrodesis depending on the extent of degenerative joint disease (DJD) present in the tarsus.

Despite the fact that plain radiographs and CT help determine both the presence and extent of DJD in the tarsal joints, radiographic signs do not always correlate with clinical findings. The authors believe, therefore, that a diagnostic local anaesthetic block performed by a skilled radiologist using contrast fluoroscopy provides important localizing information (Fig. 9). This relatively straightforward investigation not only helps to decide whether arthrodesis is likely to abolish symptoms but also, by selective infiltration of the suspect joints, in deciding which joints need to be fused.

Calcaneonavicular coalition

As calcaneonavicular bars tend in general to present at an earlier age than talocalcaneal coalitions, they are less likely to have developed associated degenerative changes. Simple resection of the coalition, therefore, is likely to be successful 7'2~27 provided there is no radiological evidence of DJD in the tarsus. Long-term follow-up data reveal 69-77% good-to-excellent results. 2~,28,2~ A talar beak, which represents increased stress across the talonavicular joint rather than degenerative change, should not be regarded as a con- traindication. 9 Excision of the coalition can be performed in older patients, but the risk of undetected degenerative change exists and persistent pain may require a subsequent triple arthrodesis. 25'29

The technique of calcaneonavicular bar excision consists of a standard lateral approach to the sinus tarsi, followed by a generous resection of the coalition (Fig. 4b). It should be noted that there is a tendency to resect an inadequate amount of bone, especially from the navicular. It is important that the shape of the excised piece should be trapezoidal and that the proxi- mal and distal cut surfaces are parallel and not conver- gent. One must also avoid breaching the capsule of the talonavicular joint, as this may allow subluxation of the navicular on the talus? 4 Next, extensor digitorum

Fig. 9 Fluoroscopically guided diagnostic local anaesthetic block of the subtalar joint.

brevis (EDB) 1,9,25 or autogenous adipose tissue 5,24 is interposed between the resected ends of the calcaneus and navicular in an attempt to limit haematoma for- mation and bony regrowth. Bone wax applied to the resected surfaces is also often used as a supplement to the interpositional material. 9'24 Mitchell and Gibson 29 using no interpositional material, reported a significant recurrence of coalitions. However, some authors report reasonable results with resection of a larger rectangle of bone and not placing EDB into the defect. 2 Postoperatively, splint immobilization is used for 7 1 0 days, within which early active motion is started. Increased range of active motion is encouraged following removal of the splint. Gradual weight-bearing is allowed as pain decreases and range of motion increases.

Although limited hindfoot motion is often not greatly improved by the procedure, especially in adults, most patients obtain good pain relief. In those that don't, we believe the source of persisting pain to be a degenerate subtalar joint. In such a case, we would perform a local anaesthetic diagnostic block under fluoroscopy to confirm that this is the source of pain and, if satisfactory relief is obtained, would pro- ceed with an isolated subtalar fusion (Fig. 10). If pain relief is incomplete following the block, or there is significant DJD in the midtarsal joints, triple arthrodesis is indicated.

Talocalcaneal coalition

Traditionally, triple arthrodesis has been recom- mended as the procedure required if conservative treatment has failed. ~,5,7,14 Many authors, however, have reported good results following resection of the coalition, 1°,24,3°-34 although with rates of success ranging from 50% 30 to 94%, 32 the results of simple resection do not appear as predictable as for calcaneonavicular coalition. It has been argued that resection seldom produces satisfactory results because secondary changes will have already developed in the subtalar joint by the time of presentation. 8 This is probably due to the fact that talocalcaneal coalitions present later than calcaneonavicular ones and, in general, restrict


Fig. 10 Isolated subtalar fusion.

subtalar motion to a greater degree2 Both are factors that increase the likelihood of secondary DJD presence, ~ thus militating against successful simple excision. Cowell has also reported that resection of the coalition at the middle facet disturbs hindfoot mechanics and places undue stress on the remainder of the subtalar joint. 7 Nevertheless, proponents of excision cite their results and also, that with the advent of CT, it is now possible to assess accurately the presence of secondary DJD, which would pre- clude resection as an option. Some believe that the extent of coalition is also important and that successful resection depends on 50% or less of the area of the joint being involved? °'3° Most reports of successful resection of talocalcaneal coalition though, have follow-up of less than five years, ~°'24,31'33'~4 and have involved mostly young patients with a mean age of less than 16. 24,3°-33 Results of a recent report, however, involving a slightly older average age group of patients, with longer follow-up and a more critical method of grading, were less favourable. Although most of their patients had some improvement, few were completely asymptomatic and the results were worse for patients followed for five or more years25 Interestingly, they also showed continuing difficulties with function of the hindfoot and ankle after resection, which is in contrast to several previous reports citing improved function as one of the reasons to perform r e s e c t i o n . 1°,24,31.33,34 Therefore, the efficacy of resection of a talocalcaneal coalition remains controversial.

The technique of resection of a medial subtalar facet coalition has been well described. 2,9,1°,33 For posterior facet coalition resection, Scranton *° has described a lateral approach, either anterior or posterior to the fibula so as to avoid disturbance of the fibular collat- eral ligaments. As with calcaneonavicular resection, authors vary as to whether or not to use interpositional material. Of those who do, most use bone wax and an autogenous fat g r a f t ; 9'~°'31'33 others have used slips of flexor hallucis longus. 34,35 Postoperatively, the patient is started on a rehabilitation regimen similar to that for calcaneonavicular bar resection, consisting of protected early active movement with no weight- bearing. Gradual weight-bearing is introduced when

there is no pain on movement of the subtalar joint, and range of motion is similar to that obtained at the time of surgery.

The authors are of the opinion that, by the time most talocalcaneal coalitions present, secondary changes already exist, which are generally confined to the subtalar joint and that, although the subtalar joint has little or no clinical motion, there is enough micro- motion to cause pain. If, as Kitaoka et a135 have shown, resection does not result in improved function of the hindfoot, then the principal aim of operative intervention remains the abolition of pain. It is our belief that a primary subtalar fusion achieves this more reliably than resection in the case of talocalcaneal coalition and is therefore, certainly in the older patient, our preference provided there is no evidence of DJD in the midtarsaljoints. If there is any doubt as to the source of pain, we would perform a diagnostic local anaesthetic block as outlined previously.

We also agree with Mann et al ~3 that an isolated subtalar fusion with the heel in an appropriate degree of valgus, is preferable to a triple arthrodesis if the problem is isolated to the subtalar joint because it results in a more mobile forefoot. Fusion of only the subtalar joint results in more residual midtarsal joint mobility than either double or triple arthrodesis 36 and the foot is thus able to dissipate more energy. Other authors also recommend a subtalar arthrodesis in preference to a triple, but as a salvage procedure for a failed resection with little or no degenerative change present, rather than as a primary procedure?

For those patients primarily presenting with degenerative changes and pain in both hindfoot and midfoot or, if clinically significant changes occur subsequent to a subtalar arthrodesis, then triple arthrodesis is indicated.

S U M M A R Y

Tarsal coalition is an uncommon, autosomal dominant hereditary disorder of the hindfoot that primarily affects adolescents but often presents in adults. Calcaneonavicular and talocalcaneal coalitions are the commonest types. Ma W coalitions are asymptomatic but commonly present with a rigid, painful flatfoot. Peroneal spastic flatfoot is the least common but most impressive presentation. A history of repeated ankle sprains is not unusual and misdiagnosis not uncommon. Despite advances in diagnostic imaging, a thorough history and physical examination remain the keys to its diagnosis. Although plain radiographs remain important, both CT and MRI have proved to be the most sensitive investigations. Nonoperative treatment should be tried initially in all patients. The indication for surgery is failed nonoperative treatment of a symptomatic coalition. The operative choice is dependent on various factors, but is essentially one between resection of coalition and


arthrodesis. Resection appears best for calcaneonavicular coalitions. Results are less predictable for talocalcaneal coalitions, especially in adults, for which the authors advocate isolated subtalar arthrodesis. Triple arthrodesis should be reserved for those with significant degenerative changes in other joints too.

ACKNOWLEDGEMENT

The authors would like to thank Ian J. Alexander MD FRCS(C) for permission to use Figure 5.

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Sakellariou & Claridge (1998) - Tarsal coalition- aetiology, diagnosis and treatment.pdf