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Congenital Vertical Talus: Etiology and Management

Miller, Mark MD; Dobbs, Matthew B. MD

JAAOS - Journal of the American Academy of Orthopaedic Surgeons: October 2015 - Volume 23 - Issue 10 - p 604–611
doi: 10.5435/JAAOS-D-14-00034
Review Article
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SDC

Congenital vertical talus is a rare foot deformity. If left untreated, it causes significant disability, including pain and functional limitations. Although the etiology of vertical talus is likely heterogeneous, recent evidence strongly supports a genetic cause linking it to genes expressed during early limb development. Traditional management for vertical talus involves extensive surgeries that are associated with significant short- and long-term complications. A minimally invasive approach that relies on serial manipulation and casting to achieve most of the correction has been shown to produce excellent short-term results with regard to clinical and radiographic correction in both isolated and nonisolated cases of vertical talus. Although long-term studies are needed, achieving correction without extensive surgery may lead to more flexible and functional feet, much as Ponseti method has done for clubfeet.

From the Department of Orthopaedic Surgery, Washington University School of Medicine, St. Louis, MO.

Dr. Dobbs or an immediate family member has received royalties from and serves as a paid consultant to D-Bar Enterprises and serves as a board member, owner, officer, or committee member of the American Academy of Orthopaedic Surgeons, the American Orthopaedic Association, the Missouri State Orthopaedic Association, the Orthopaedic Research and Education Foundation, and the Pediatric Orthopaedic Society of North America. Neither Dr. Miller nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this article.

Received June 22, 2014

Accepted December 19, 2014

Congenital vertical talus (ie, rocker-bottom flatfoot) is a rare rigid flatfoot disorder characterized by hindfoot valgus and equinus, with associated midfoot dorsiflexion and forefoot abduction caused by a fixed dorsal dislocation of the navicular on the head of the talus. The condition is not always diagnosed accurately in newborns because of the difficulty in differentiating it from other, more common benign positional foot anomalies.1 Without treatment, vertical talus can lead to significant disability, including foot and ankle pain as well as medial plantar callus formation on the foot around the prominent talar head.2-4 Traditional surgical management for vertical talus is intensive, long, and fraught with short-term and long-term complications.5 Complications include both undercorrection and overcorrection of the deformity; both require additional surgeries and carry a higher risk of morbidity. The scar tissue created with extensive soft-tissue releases in a child’s foot can lead to stiffness and pain over time. A minimally invasive alternative developed a decade ago has proved successful in providing correction while avoiding the need for extensive soft-tissue release procedures.1,6-9,10-17

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Epidemiology

Although the exact incidence of vertical talus is unknown, the estimated prevalence is 1 in 10,000 live births.18 This number, however, is likely low because of the lack of recognition of the condition in newborns. Furthermore, because this condition is rare, large studies are lacking, making it difficult to determine whether there is a laterality or gender predilection for this deformity. Emphasis should be placed on gathering this type of information through large, multicenter studies because the data are essential for identifying the development pathways responsible for vertical talus.

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Etiology

In most cases, the etiology of vertical talus deformity remains unknown. Approximately one half of cases of vertical talus occur in conjunction with neurologic disorders (neuromuscular and central nervous system)19 or known genetic defects and/or syndromes.20 The other half occur in children without other congenital anomalies and are considered idiopathic or isolated cases. The most common neurologic disorders associated with vertical talus are distal arthrogryposis and myelomeningocele,19 and the most common genetic defects include aneuploidy of chromosomes 13, 15, and 18.21 Vertical talus is also commonly associated with a variety of syndromes, including De Barsy, Costello, and Rasmussen syndromes22 and split hand and split foot limb malformation disorders. Of the 50% of cases of vertical talus that are isolated, almost 20% have a positive family history of vertical talus. In most of these cases, the condition is inherited in an autosomal dominant fashion, supporting the theory that a significant number of isolated cases have a genetic etiology, as well.23 Specific gene mutations in the homeobox transcription factor and cartilage-derived morphogenetic protein-1 genes have been found to be causative in some patients with familial, autosomal dominant isolated vertical talus and in some families with congenital hand and foot anomalies of which vertical talus is a feature.23-25 Growth differentiation factor 5 is closely related to the bone morphogenetic proteins associated with neurologic and limb development.

No single gene defect is responsible for all cases of vertical talus; therefore, it is likely that the pathophysiologic basis for the development of vertical talus is heterogeneous in nature. One hypothesis to explain vertical talus associated with neuromuscular disorders is an imbalance in muscle strength. In patients with myelomeningocele with vertical talus, a weak posterior tibialis and relatively strong ankle dorsiflexors could be contributing factors, whereas weakness of the foot intrinsic muscles may play a contributing role in other neuromuscular disorders. These mechanisms and congenital muscle abnormalities, which are also seen in the setting of distal arthrogryposis, may play a role in some cases of isolated vertical talus, as well. This is supported by the high percentage of abnormal skeletal muscle biopsies performed in this patient population.20 Congenital vascular deficiency of the lower extremities has also been proposed as a potential cause of vertical talus based on magnetic resonance angiography findings that demonstrated congenital arterial deficiencies of the lower extremity in a group of patients with isolated vertical talus.26

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Pathoanatomy

Autopsy and surgical findings have contributed to the understanding of the pathologic anatomy of the vertical talus.27,28 The hindfoot is in marked equinus and valgus caused by contracture of the Achilles tendon and the posterolateral ankle and subtalar joint capsules. The midfoot and forefoot are dorsiflexed and abducted relative to the hindfoot secondary to contractures of the tibialis anterior, extensor digitorum longus, extensor hallucis brevis, peroneus tertius, and extensor hallucis longus tendons and the dorsal aspect of the talonavicular capsule. The navicular is dorsally and laterally dislocated on the head of the talus, resulting in the development of a hypoplastic and wedge-shaped navicular. Both the talar head and neck are abnormal in shape and orientation, resulting in a flat appearance that is angled medially from the midline. The position of the talus stretches vertically and weakens the plantar soft tissues, including the calcaneonavicular, or spring ligament, which gives the foot a rocker-bottom appearance. The plantar surface of the foot is convex, whereas the dorsal aspect of the midfoot has deep creases (Figure 1). The calcaneus is in extreme equinus, which often causes either dorsolateral subluxation or frank dorsal dislocation of the calcaneocuboid joint. The posterior tibial tendon and the peroneus longus and brevis are commonly subluxated anteriorly over the medial and lateral malleolus, respectively; the subluxated tendons may then function as ankle dorsiflexors rather than plantar flexors.16

Figure 1

Figure 1

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Physical Examination and Clinical Features

Hindfoot equinus, hindfoot valgus, forefoot abduction, and forefoot dorsiflexion are present in all newborns with vertical talus. The rigidity of the deformity is the key to distinguishing between vertical talus and more common conditions, such as calcaneovalgus foot, posteromedial bowing of the tibia, and oblique talus. If hindfoot equinus is not a clinical feature, then the deformity is not vertical talus and is likely positional in nature. Because of the frequency of neuromuscular and genetic abnormalities associated with vertical talus, it is important to perform a comprehensive physical examination. The clinician should look for facial dysmorphic features that require a referral to a geneticist or abnormalities suggestive of a neuromuscular etiology, which would require MRI evaluation of the neuroaxis and referral to a pediatric neuromuscular specialist. The presence of a sacral dimple, in particular, should alert the examiner to possible central nervous system anomalies.

It is equally important for the examiner to document motor function of the foot and ankle with special attention to the toe flexors and extensors. This is done by stimulating the plantar and dorsal aspects of the foot separately to elicit plantar flexion and dorsiflexion of the toes. This should be done serially during treatment sessions because the examination can be difficult, and results from serial examinations are more telling. The presence of dorsiflexion and plantar flexion of the toes is recorded as absent, slight, or definitive. This should be recorded for the great toe alone as well as the lesser toes as a separate group. In our experience, slight or absent ability to move the toes with stimulation correlates with a vertical talus deformity that is more rigid and less responsive to treatment. It may also be indicative of a subtle congenital neurologic or muscular anomaly.

Clinically, a congenital vertical talus foot has a convex plantar surface that results in a rocker-bottom appearance (Figure 1, A). The dorsum of the foot has deep creases secondary to forefoot and midfoot dorsiflexion (Figure 1, B). The extreme dorsiflexion of the forefoot creates a distinct palpable gap dorsally where the navicular and talar head would articulate in a normal foot. Characteristics of this gap can help the examiner assess rigidity. If the gap reduces with plantar flexion of the forefoot, then the deformity has a degree of flexibility; this may help predict responsiveness to treatment. Left untreated, a rigid vertical talus deformity may worsen with weight bearing because secondary adaptive changes occur in the tarsal bones.3 Painful callosities can develop along the plantar medial border of the foot around the prominent and unreduced talar head. Heel strike does not occur, shoe wear becomes difficult, and pain develops.3,4

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Radiographic Evaluation

Standard radiographic evaluation of vertical talus deformity includes an AP view and three lateral views of the foot in maximal dorsiflexion, maximal plantar flexion, and neutral. Standing views are obtained in older children. The lateral view of the foot in maximal plantar flexion, which is the standard of care for accurate diagnosis of vertical talus, is important for determining the rigidity of the talonavicular dislocation (Figure 2, A). However, the cartilaginous nature of the bones in a newborn’s foot can make diagnosis of vertical talus challenging. Although the hindfoot and metatarsals are ossified at birth, the cuneiforms, navicular, and cuboid are not. The cuboid ossifies during the first month of life and the cuneiforms and navicular ossify at age 2 and 3 years, respectively. For this reason, radiographic evaluation of suspected vertical talus in a newborn must focus on the relationships between the ossified structures.

Figure 2

Figure 2

Useful measurements on lateral radiographs (with the foot in neutral, maximal dorsiflexion, and plantar flexion) include the talocalcaneal angle, tibiocalcaneal angle, and talar axis-first metatarsal base angle (TAMBA; Figure 2, B and C). On the neutral lateral view, the long axis of the talus is vertical in relation to the first metatarsal, and the calcaneus is in significant equinus, as evidenced by a high tibiocalcaneal angle. The lateral views of the foot in forced dorsiflexion and plantar flexion are important to help assess the rigidity of the deformity and to help differentiate vertical talus from more flexible deformities, such as an oblique talus or calcaneovalgus foot. For most cases of vertical talus, the lateral view of the foot in plantar flexion demonstrates persistent vertical orientation of the talus, whereas the lateral view of the foot in forced dorsiflexion demonstrates persistent rigid hindfoot equinus. On the lateral view of the foot in plantar flexion, the lateral TAMBA can be used as one criterion to help distinguish vertical talus from oblique talus, with values >35° considered to be diagnostic for vertical talus.29 However, vertical talus cannot be ruled out with values <35°. In such cases, the presence or absence of hindfoot equinus must be documented to distinguish between vertical talus and oblique talus. If equinus is present, then the deformity is rigid and warrants treatment in the same manner as that for vertical talus with a TAMBA angle >35°. Further radiographic measures to consider when assessing for the presence of vertical talus are the AP talocalcaneal angle and TAMBA. Although the talocalcaneal angle is increased in all patients with vertical talus, compared with normative values that indicate hindfoot valgus there is no angle that is pathognomonic of the deformity.

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Classification

Current classification systems for vertical talus focus on either a description of the anatomic abnormalities present or the presence or absence of associated diagnoses. The most widely used anatomic classification system was proposed by Coleman et al.2 They described two types of vertical talus; type I deformity is characterized by a rigid dorsal dislocation of the talonavicular joint. In addition to a rigid dislocation of the talonavicular joint, a type II deformity has a dislocation or subluxation of the calcaneocuboid joint (ie, the long axis of the calcaneus lies plantar to the long axis of the cuboid). Other classification systems have focused on whether the vertical talus was an isolated deformity or was present in addition to other abnormalities.29,30 The problem with these classification systems is that they do not directly take into account the motor function of the lower legs. In our experience, weak or absent motor function in the lower leg musculature is predictive of not only poor response to initial treatment but also a risk of relapse.20,26 The child’s ability to dorsiflex and plantarflex the toes can be evaluated by lightly stimulating the dorsal and plantar aspects of the foot. Movement can be graded as definitive, slight, or absent. This simple examination can be repeated at each clinical visit to improve accuracy. A new classification system that takes this into account is needed because the ability to better predict the response to treatment will allow for the development of an individualized treatment program for patients.

It should be noted that current classification systems have attempted to define oblique talus as a milder form of vertical talus based on radiographic and clinical examination criteria.29,31,32 However, these attempts at classification have not translated into consistent treatment recommendations because some oblique tali do require treatment despite being milder in nature.29 In our experience, oblique tali that have an associated Achilles tendon contracture are at risk of becoming symptomatic with time. For this reason, we consider oblique tali and vertical tali to be related entities that occur along a spectrum of severity. Similar to clubfeet, not all vertical tali have the same rigidity. If oblique talus is diagnosed on radiography, but an equinus contracture (defined as the inability to achieve 10° of passive ankle dorsiflexion with the knee extended and flexed) is present, we treat it as a vertical talus. Treatment decisions, in our experience, should be based on the rigidity of the talonavicular joint as well as of the hindfoot.

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Extensive Surgical Management

Primary surgical treatment of a congenital vertical talus in a child younger than 2 years can be done with either a one-stage or two-stage extensive soft-tissue release.2,28,33-36 The first stage of the two-stage approach consists of lengthening the contracted dorsolateral tendons, releasing the associated dorsolateral capsular contractures, and reducing the talonavicular and subtalar joint complex. The second stage consists of lengthening the Achilles and peroneal tendons as well as performing a posterolateral capsular release.37 Historically, the one-stage approach was simply a combination of the two stages into a one-stage procedure. Seimon28 modified the one-stage approach, emphasizing that, by carefully addressing the dorsolateral soft-tissue contractures, less extensive soft-tissue release was needed posteriorly. Mazzocca et al38 compared Seimon’s dorsal approach with more extensive staged approaches and found that it required less surgical time, had fewer complications, and resulted in improved clinical outcomes. Today, most authors use some form of the single-stage approach28,33,34-36,38 and report better results than those achieved using a two-stage approach.2,18,37 However, the complications associated with both approaches (eg, wound necrosis, osteonecrosis, undercorrection and overcorrection of deformities) are concerning.5,39 Longer-term problems include stiffness of the ankle and subtalar joints and the development of degenerative arthritis, leading to the need for salvage procedures, such as subtalar and triple arthrodeses. These problems are similar to the poor long-term outcomes and functional disability reported with extensive soft-tissue release surgery for clubfoot.40

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Authors’ Preferred Method

A minimally invasive approach that consists of serial manipulation and casting followed by temporary stabilization of the talonavicular joint by Kirschner wire (K-wire) and an Achilles tenotomy has provided excellent short- and mid-term radiographic and clinical results for isolated and nonisolated congenital vertical talus1,16,17 (Figures 3 and 4). Thus, we recommend this method for management of all vertical tali regardless of the patient’s age at presentation or the presence of associated diagnoses. In patients with a severe rigid deformity (most often nonisolated cases) in which complete correction is not achieved with casting, minor surgery is needed to complete the correction.

Figure 3

Figure 3

Figure 4

Figure 4

To successfully perform this minimally invasive procedure, the treating physician must have a thorough knowledge of the subtalar joint, experience treating clubfeet with manipulation and casting, and the ability to accurately localize the head of the talus on the plantar medial aspect of the midfoot. The head of the talus is the key landmark; it is the structure that the rest of the foot will be manipulated around during correction. All components of the vertical talus are corrected simultaneously, with the exception of the hindfoot equinus, which is corrected last. Manipulations are gentle and consist of stretching the foot into plantar flexion and adduction with one hand while counterpressure is applied as the thumb of the opposite hand gently pushes the talus dorsally and laterally. It is essential not to touch the calcaneus during manipulations because this can prevent the calcaneus from correcting from a valgus to a varus position.

After 1 or 2 minutes of manipulation, a long leg plaster cast is applied to hold the foot in the position achieved with stretching. The cast is applied in two sections, with the short leg portion applied first to allow the treating physician to make the appropriate molds. Although the principles of manipulation and casting are not difficult, attention to detail is crucial. The foot should be held in the position achieved with stretching while an assistant rolls the plaster. Moving the foot into the corrected position after the cast is applied can result in a poorly molded cast, resulting in skin problems or cast slippage.

Once the plaster has been applied, the treating physician then molds carefully around the talar head, the malleoli, and above the calcaneus posteriorly. When the plaster has set, the dorsum of the toes is exposed by removing excess plaster. This is important for assessing circulation and gives the parents a reference point to monitor for cast slippage. The cast is then extended above the knee, with the knee in 90° of flexion. Casting is done weekly in the clinic and is initiated in the first few months of life, if possible. It takes an average of five casts to achieve reduction of the talonavicular joint, and each week the foot is placed further into equinovarus. In the final cast, the foot should be positioned in extreme equinovarus to achieve adequate stretching of the dorsolateral soft tissues (Figure 5). In this extreme position, the foot resembles a clubfoot. With experience, the treating physician will be able to clinically assess the successful reduction of both the talonavicular and calcaneocuboid joints.

Figure 5

Figure 5

When reduction is achieved, the patient is scheduled for surgical stabilization of the talonavicular joint with a K-wire followed by a percutaneous Achilles tenotomy. When learning this technique, we advise the surgeon to make a small skin incision dorsomedially over the talonavicular joint. This allows the surgeon to ensure that the joint is reduced without opening the joint capsule (in most cases) and aids in the placement of the K-wire. If the joint is not completely reduced, a small capsulotomy is made in the anterior subtalar joint to allow the placement of an elevator to gently complete the reduction. Once the talonavicular joint is reduced, the K-wire is placed in a retrograde fashion across the joint under radiographic guidance (Figure 6). We recommend burying the wire to minimize the risk of its backing out; this risk is higher the younger the patient is at the time of surgery. Rarely, residual contracture in the peroneus brevis, tibialis anterior, and/or dorsal extensor tendons is present after serial casting in severe cases of nonisolated vertical talus. In this setting, lengthening of the involved tendons should be performed. Once the talonavicular joint is stabilized, an Achilles tenotomy is done to correct residual equinus.

Figure 6

Figure 6

A long leg cast is applied with the ankle and forefoot in a neutral position. The cast is changed 2 weeks postoperatively to manipulate the ankle to 10° of dorsiflexion. The K-wire is removed in the operating room 6 weeks after the index procedure. The patient then uses a shoe and bar brace system, which must be worn full time for 2 months and then only at night for 2 years, to prevent relapse. The shoes on the brace are set pointing straight ahead to stretch the peroneal tendons. When a static bar is used, it is important not to place a dorsiflexion bend in the bar. The dorsolateral soft tissue is tighter than the posterior structures; therefore, it is more important to stretch the foot into plantar flexion. The dynamic bar allows active motion at the knees and ankles and has a spring assist that promotes stretching of the dorsolateral soft tissues at rest.41 Parents are also taught foot-stretching exercises that emphasize ankle plantar flexion and foot adduction; these exercises are to be performed several times a day at diaper changes to maintain flexibility in the feet. Once patients are old enough to walk, daytime bracing with a solid ankle-foot orthosis is used for support instead of the bar brace system. Bracing off of a bar is not needed for patients with isolated vertical talus.

In our experience, relapses are uncommon. It is more common to see a patient with residual deformity that was not fully corrected during initial treatment. Given the low relapse rate, we have reduced the recommended duration of nighttime bracing from 4 years to 2 years. In most cases, relapses can be managed with repeat casting alone, but patients older than 2 years may require a limited open reduction of the talonavicular joint after serial casting.

Since the introduction of this technique in 2006,1,17 many subsequent studies have demonstrated its efficacy in achieving initial correction in patients with isolated or nonisolated vertical tali as well as its reproducibility.6,8,9-11,13-16,42

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Pearls and Pitfalls

Successful manipulation of the vertical talus requires careful location of the head of the talus, which is on the plantar medial aspect of the foot. It serves as the fulcrum for reducing the associated deformities. In a newborn’s foot, palpation of the vertical talus can be difficult, and pressing on the distal medial aspect of the calcaneus rather than on the head of the talus is a common error. It is crucial not to touch the calcaneus during manipulation. If the calcaneus is prevented from sliding into a varus position, then complete correction will not be achieved. Another common error is not achieving maximal equinovarus positioning in the last cast before K-wire placement. Failure to do so will result in a high risk of relapse because the dorsolateral soft tissue will not be adequately stretched. A skin incision can be made without performing a capsulotomy to ensure accurate wire placement. In an infant’s foot, ensuring that the K-wire is centered is difficult without direct visualization, even with radiographic guidance. However, accurate K-wire placement minimizes the risk of the wire backing out prematurely. The postoperative use of a shoe and bar brace system and stretching exercises are important to minimize the risk of relapse.

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Summary

Congenital vertical talus is a rare foot deformity that is often unrecognized or misdiagnosed in newborns secondary to the spectrum of rigidity of the foot deformity. A careful physical examination, with an emphasis on assessing the patient for the presence of an equinus contracture, can greatly aid the treating physician in differentiating a vertical talus from other, more benign and positional foot anomalies. This distinction is critical because early recognition leads to early treatment, which is more successful. Traditional management involves an extensive surgical release; however, extensive surgery is not necessary because excellent results have been achieved with a minimally invasive approach that emphasizes serial manipulation and casting. By avoiding more extensive surgery, it is likely that patients with vertical talus will maintain more flexibility, experience less pain, and have better function in the feet long-term, similar to the long-term results achieved with minimally invasive approaches for clubfoot. Additional research is needed to elucidate the genetic etiology of vertical talus and to correlate those results with physical examination findings on presentation to develop a new classification system that will allow clinicians to better predict a patient’s response to treatment.

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References

Evidence-based Medicine: Levels of evidence are described in the table of contents. In this article, references 1-29 and 31-42 are level IV studies.

References printed in bold type are those published within the past 5 years.

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