Metatarsus adductus

Intoeing is one of the most frequent concerns that families have about their children. In the infant, the cause of intoeing often is metatarsus adductus (MA).

In MA, the forefoot is adducted with respect to the hindfoot. The cosmetic appearance of the foot has been described as kidney or bean shaped. Most often the anatomical site of deformity is the tarsometatarsal joints, with lesser degrees of adduction through the transtarsal joints. The medial cuneiform–first metatarsal articulation often is oblique, and autopsy findings reported by Reiman and Werner⁸⁰ noted alterations in the size and shape of the first cuneiform. Usually no significant bowing of the metatarsals themselves is seen.

The subtalar joint, and therefore the heel, may be in various degrees of varus or valgus but most frequently is near neutral. Some authors use heel position to make a distinction between typical MA and metatarsus varus.^77,97 If the heel is resistant in valgus, the condition may be skewfoot (see section on skewfoot). Significant or rigid heel varus raises the possibility that the deformity is a clubfoot. A key differential between MA and clubfoot is ankle motion. In clubfoot, the calcaneus is resistant in equinus and the foot as a unit cannot be passively dorsiflexed normally at the ankle. The hindfoot in MA can be manipulated through a full range of dorsiflexion and plantarflexion at the ankle joint.

The exact etiology of MA is unknown, but the condition usually is attributed to intrauterine positioning. Although the incidence has been reported as 1:1,000, most practitioners argue that MA is much more frequent.¹⁰⁷ Bilateral involvement is present in over 50% of cases, and a positive family history is found in 10% to 15% of patients.⁷⁷ An initial report of association with hip dysplasia⁵⁰ has not been reproduced in other studies.⁶²

The severity of MA is variable in terms of degree of deformity and flexibility of the foot. Radiographic classification of severity¹² has been criticized because of significant variability.²³ If a permanent image is desired, an impression of the weight-bearing foot can be made by having the child stand on a photocopying machine.⁹² A clinical classification system proposed by Bleck¹⁴ uses the heel bisector to describe the appearance (Fig. 35-1) and flexibility (Table 35-1) found at physical examination. Another simple assessment of flexibility²⁴ suggests that a type 1 foot actively corrects with stroking or tickling the lateral foot, a type 2 foot corrects only with passive stretching, and a type 3 foot cannot be passively corrected.

Fig. 35-1 Heel bisector method defines the relationship of the heel to the forefoot. Normal—bisecting between the second and third toes. Valgus—bisecting between the great and second toes. Mild MA—bisecting the third toe. Moderate MA—bisecting between the third and fourth toes. Severe MA—bisecting between the fourth and fifth toes.

(Adapted from Bleck EE: Dev Med Child Neurol 24:545,1982.)

Table 35-1 Clinical classification system for metatarsus adductus

A long-term study by Farsetti et al.³⁶ confirmed that classification based on flexibility at the time of diagnosis is valid. Feet with mild or moderate deformity that were passively correctable did well untreated. Those with rigid MA responded well to correctly performed serial manipulation and plaster casting. These authors advise treatment as soon as the deformity is diagnosed and found not to be passively correctable. Bleck’s large study of MA also emphasized that patient age at initiation of treatment was the best predictor of good outcome.¹⁴

Treatment of MA is based on severity, flexibility, and patient age. For infants younger than 6 months, feet that actively correct or that passively correct past the midline generally do well with observation and stretching. A typical regimen includes stretching of foot four to six times each day, 10 repetitions each time, with the forefoot held in the corrective position for no less than 6 seconds per repetition. Parents or caretakers should be taught to support the child’s heel during this stretching, to prevent spurious correction through the subtalar joint with creation of heel valgus.

For infants and toddlers, treatment of the more rigid MA usually begins with serial manipulation and casting. Long leg casts are most often recommended,⁷⁷ with the knee flexed, the forefoot abducted, and the foot somewhat externally rotated. Katz et al.⁵⁶ believe that below-knee casts are just as effective. Casts are changed at 2-week intervals or more frequently, and with each cast change an attempt is made to manipulate the foot into an overcorrected position. Goals include correction of the static deformity and improvement of midfoot flexibility.

Once the foot can be easily brought to an overcorrected position, whether through stretching of the moderate deformity or through serial casting of the more rigid deformity, then various types of shoe modifications and orthoses may be useful in maintaining desired alignment. No evidence-based literature documents whether any particular bracing technique is superior.

In one popular method, the foot is braced with specially constructed shoes, commonly referred to as orthopedic or corrective shoes. The last, in this case meaning the basic shape of the sole of the shoe, determines the type of forces that are directed to the foot. Reverse last shoes (Fig. 35-2), also known as tarsal pronator shoes, turn outward at the midfoot to maintain the abducted position achieved by either surgical or manipulative correction. Straight last shoes accomplish that same goal to a lesser degree. Another useful commercial product is the Bebax shoe (Fig. 35-3),⁴ which is designed with an adjustable multidirectional hinge between the hindfoot and forefoot sections. This setup allows progressive adjustment of position as the deformity becomes more flexible. Several authors have advised against joining the shoes with the Denis-Browne bar for treatment of MA. Addition of the bar results in a tendency to produce correction through the subtalar joint, leading to heel valgus and flatfoot.^12,77

Fig. 35-2 Reverse last or “tarsal pronator” shoe is designed to brace the forefoot into abduction with respect to the hindfoot. The high-top design, along with the ankle strap, helps to keep the shoe in place.

Fig. 35-3 Bebax “boot” is designed with an adjustable turnbuckle between the hindfoot and forefoot sections so that position and bracing forces can be adjusted.

The Wheaton brace (Fig. 35-4), a plastic knee–ankle–foot orthosis (KAFO) or ankle–foot orthosis (AFO) with an extended medial sidewall to prevent forefoot adduction, is frequently used. This polypropylene KAFO/AFO is manufactured with an outward flare shape to the foot section, much like the shape of a reverse last shoe.

Fig. 35-4 Wheaton AFO is designed to maintain forefoot abduction. A KAFO design also is available.

Rarely, surgery is indicated for more severe cases and for older children with delayed diagnosis. Many procedures are available, and discussion of specific operations is beyond the scope of this chapter. Maintenance casts, orthoses, or special shoes are commonly advised following surgical correction. These devices are similar to the devices described earlier.

Long-term studies of MA in adulthood are scarce. Farsetti et al.³⁶ reported few adult complaints. Most pediatric orthopedists continue to observe the flexible deformities and treat the more severe rigid feet with serial casting, followed by bracing in straight last or reverse last shoes.

Skewfoot

Skewfoot is an uncommon deformity, and it is especially uncommon in the newborn.^68,72 The etiology is unknown. The deformity presents generally as MA with heel valgus. On closer inspection, an almost “corkscrew” alignment of the foot is seen. The forefoot is in adduction with some degree of supination, while the hindfoot is in abduction with significant valgus. A key finding is lateral displacement of the navicular on the talus. Unfortunately the navicular does not ossify before age 3 to 6 years, so this displacement is radiographically silent in the infant or toddler. Berg¹² described simple and complex types of skewfoot, based on whether or not the calcaneocuboid joint was similarly displaced.

Treatment ranges from serial casting to surgical correction. Although Berg¹² believes that milder forms of skewfoot can be corrected with serial casting, Peterson,⁷² in a review of the world literature, reported that all authors found nonoperative treatment to be unsuccessful. It has been suggested that a skewfoot results from improper manipulation and casting of MA.⁷⁷ Virtually all of the shoe modifications and orthoses used for treatment of simple MA have the potential to worsen heel valgus. No specific corrective orthosis is available for skewfoot. A foot orthosis (FO) can be custom molded to accommodate the foot shape for pain relief.

Clubfoot

Clubfoot, more properly called congential talipes equinovarus, is easily recognized because the cosmetic appearance resembles a club on the end of the leg. The disorder is highly variable with regard to severity, rigidity, and response to treatment.

The incidence of clubfoot is different among geographic and ethnic groups, ranging from 0.64 to 6.8 per 1,000 live births.⁷ About 70% of clubfoot occurs in males, and the right foot is more frequently affected. The condition is bilateral in about 50% of cases.

The etiology remains unknown in most instances. Familial associations are observed, but the genetic relationships are not determined. Clubfoot is quite common in some conditions, such as spina bifida, diastrophic dwarfism, arthrogryposis, and amniotic band syndrome. Clubfoot associated with these syndromes tends to be resistant to both nonoperative and surgical treatment.

Physical examination includes equinus and varus of the hindfoot, with adduction and supination through the midfoot. This combination brings the medial side of the great toe and first metatarsal adjacent to the medial distal tibia. A transverse crease is almost always present across the midfoot in the medial longitudinal arch. The appearance of the heel may be misleading, and it is important to palpate the actual location of the tuberosity of the calcaneus. Frequently the heel pad is “empty” and the ankle equinus has positioned the tip of the calcaneus more proximally, against the distal fibula. This resistant equinus deformity through the ankle distinguishes clubfoot from severe MA or skewfoot. Relative underdevelopment of the calf musculature and some shortening of the limb are almost always present with clubfoot. The family must be aware of these associations so that they are not subsequently identified as complications of treatment.

The pathoanatomy of clubfoot includes contracture and shortening of soft tissues, such as the tendons and ligaments; subluxation of joints, such as the subtalar and talonavicular articulations; and actual deformity of the bones, especially the talus. Whether one of these components is primary or causative to the clubfoot has not been proven. However, I believe that knowledge of hindfoot subluxation facilitates our understanding of soft-tissue contractures and bone deformity. The subtalar joint is subluxated, with the calcaneus displaced into varus beneath the talus. Simultaneously and inseparably, the calcaneus has rotated around an axis defined by the interosseous talocalcaneal ligament, bringing the tuberosity of the calcaneus laterally toward the lateral malleolus and the anterior end of the calcaneus medially toward the medial malleolus. The navicular is subluxated medially on the talar head, which brings the navicular immediately adjacent to the tip of the medial malleolus. The cuboid is displaced medially to a variable degree. As indicated, the ankle is in equinus. Further plantarflexion through the midfoot and forefoot creates an overall cavus condition. With the developing cartilage anlage of the foot displaced in this fashion, the talar neck is foreshortened and medially deviated, and the calcaneocuboid and medial cuneiform–first metatarsal joints are oblique medially. Posterior, medial, and plantar soft tissues are contracted.

Various orthoses are used for treatment of clubfoot. Most often, the orthosis is used as a holding device after correction by nonoperative or surgical methods. Typically a more restrictive orthosis is used initially on a full-time schedule. Once the child begins to crawl and/or walk, different bracing regimens for daytime and sleeping can be prescribed.

Scarpa in 1803 gave the first detailed description of an orthosis for treatment of clubfoot. The device was an AFO with metal upright bars and cuffs at the proximal calf and the malleoli, with a cup gripping the hindfoot. The orthosis produced a pronation and an abduction moment at the forefoot.

Straight last and reverse last shoes are the most commonly used orthoses for treatment of clubfoot. As discussed in the section on MA, the effectiveness of these shoes depends on the ability of the relatively stiff heel counter to control the hindfoot while the material of the medial side of the toe box pushes against the first ray of the forefoot. A high-top design, often augmented with a strap over the dorsum of the ankle, is almost mandatory to minimize the number of times the child removes the shoe. The Bebax shoe is adjustable through the midfoot according to the amount of abduction force desired.

Denis Browne²⁰ described his special splint for treatment of clubfoot in 1934. Treatment consisted of taping the feet onto a bar to maintain the position obtained by manipulation. Modern commercial Denis-Browne bars have adjustable footplates with screw attachments designed to match threaded plugs in the soles of certain “corrective” shoes (Fig. 35-5). The Fillauer bar is a variation on this theme, with adjustable metal clamps designed to grasp the sole of the patient’s shoe (Fig. 35-6). Typically the devices are adjusted to keep the feet externally rotated, augmenting the forefoot abduction forces provided by the shoes and adding an external rotation stretching force at the ankles. The bar can frequently be bent, center downward and away from the patient, to include a valgus moment at the hindfoot. With the footplates strongly rotated externally, this downward central bend adds some ankle dorsiflexion. In contrast to the caution given in the section on MA, application of corrective forces through the subtalar and ankle joints is desirable in patients with clubfoot. The length of the bar should approximate the width of the child’s pelvis. A cost-effective variation of this combined shoes-and-bar orthosis, constructed of basic and readily available materials, has been designed for use in underserved and financially less able regions (Fig. 35-7).

Fig. 35-5 Contemporary commercial Denis-Browne bar has adjustable footplates that attach to shoes using screw lugs in the shoe sole. This Denis-Browne bar has been bent, center downward, to provide additional valgus and dorsiflexion through the child’s ankle.

Fig. 35-6 Close-up view shows the clamping mechanism for attaching shoes of various sizes to a Fillauer bar. This Fillauer bar is adjustable for length, using the clamps shown at the right.

Fig. 35-7 Abduction orthosis advised for maintenance bracing following clubfoot correction using the Ponseti method can be constructed of very simple materials that are locally available.

AFOs and KAFOs have been adapted for use in treatment of clubfoot. They are similar to the molded braces described for the treatment of MA. The foot section incorporates an outward flare and an extended medial sidewall to ensure abduction through the midfoot. Valgus and external rotation shaping can be added to the orthosis as appropriate.

Enthusiasm for comprehensive surgical release and realignment of the clubfoot has waned with the reviews of surgically treated patients published in the 1990s and more recently noted disappointing outcomes.^5,29,55 The majority of current treatments emphasize nonoperative techniques, with limited operative interventions reserved for resistant or recurrent deformity. These techniques aim to provide painless foot function through the life of the patient with less regard to cosmesis or radiographic parameters. The French method of comprehensive physical therapy and taping and the Ponseti method of serial manipulations and holding casts both seem effective for restoration of a flexible plantigrade foot in most cases.

The initial stage of the French method relies on daily manipulation of the clubfoot by trained physiotherapists.^11,81 Between therapy sessions, foot position is generally maintained by taping. In this sense, the “orthosis” consists solely of the tape. The first English-language description of this program suggested using a Denis-Browne splint between therapy sessions for the first 2 or 3 weeks,¹¹ but subsequent reports presented in detail the technique for application of nonelastic and elastic tape and discouraged rigid bracing. In the early 1990s, continuous passive motion, provided with a specially designed machine appropriate to infants, was incorporated into the French method. At about the third month, when the foot is reasonably well corrected, continuous passive motion is discontinued and the family assumes responsibility for continuing the physical therapy and taping. When the child reaches an appropriate age to cooperate, active therapy exercises are added. No special shoes or molded orthoses are recommended. Treatment ends at about age 3 years, with monitoring to completion of growth.

In contrast, the Ponseti regimen⁷⁵ emphasizes the use of maintenance orthoses. This method of clubfoot treatment begins with serial manipulations and application of holding casts. The manipulations must be performed in a specific way, initially maintaining the forefoot in supination to facilitate correction of the cavus component of the deformity. The forefoot is abducted in supination, with counterpressure over the dorsolateral head of the talus. The calcaneus must not be grasped or pushed so that movement of the calcaneus through the subtalar joint is not restricted. Rather, repositioning of the calcaneus occurs simultaneously and spontaneously as the talonavicular joint is reduced. Satisfactory overcorrection of the cavus, adductus, and varus usually is accomplished between cast numbers three and six, at which time residual ankle equinus is assessed. A percutaneous heel cord release is frequently done at this stage, followed by another 3 weeks of cast immobilization. Maintenance of correction requires strict adherence to a bracing program. Ponseti advises using an abduction orthosis consisting of straight last shoes attached to the Denis-Browne bar, with the footplates set at 70 degrees out-toe, and with the bar bent to encourage hindfoot valgus and about 15 degrees of ankle dorsiflexion. This appliance is worn on a full-time basis for 3 months, or until the child is learning to crawl. Night bracing is continued to age 3 or 4 years. Ponseti strongly states that an AFO is not effective for maintaining correction.⁷⁶ Although few outcome studies are available, published long-term results of the Ponseti method seem encouraging. More specifically addressing the use of orthoses, several authors have observed a very high recurrence rate in patients whose families did not adhere to the bracing recommendations.^31,99

Congenital vertical talus

Congenital vertical talus (CVT) is a rare deformity that goes by many names, including congenital convex pes valgus, rocker-bottom foot, and Persian slipper foot. Physical examination reveals that the heel is in fixed equinus, with the forefoot dorsiflexed and everted. The arch is convex, and the head of the talus is prominent medially in the sole. Overall, the foot has a rocker-bottom appearance, and it is rigid and uncorrectable. A true CVT cannot be passively reduced with simple manipulation. If the talonavicular joint can be readily reduced and the ankle can be readily manipulated out of equinus, the deformity probably is either a calcaneovalgus positional deformity or the “oblique talus” of a severe flatfoot.

The etiology of CVT is unknown. Candidate genes have been suggested for some families.^28,89 Associations have been made with chromosomal disorders^100,101 such as trisomy 13, 14, 15, and 18 as well as neuromuscular disorders such as spina bifida, arthrogryposis, and sacral agenesis.

The important defining characteristic of the pathoanatomy is a fixed dorsolateral dislocation of the navicular onto the neck of the talus. In this situation, the sustentaculum tali and spring ligament are incompetent, such that the head of the talus rotates plantarward. The subtalar joint subluxates, with the calcaneus displaced laterally into valgus. Concomitant dorsal subluxation of the calcaneocuboid joint may be present. The ankle is resistant in equinus.

Radiographic confirmation of this diagnosis requires a lateral view of the foot in maximum plantarflexion.⁶¹ The navicular will not be ossified in the infant, so direct visualization of the talonavicular relationship is not possible. However, in true CVT a line drawn through the long axis of the talus will project plantarward to the ossific nucleus of the cuboid.

Treatment of CVT begins with passive manipulation and holding casts, which stretch the soft tissues. Traditionally, actual realignment of the bones by closed means was not expected. This deformity almost always was thought to require surgical correction. A casting regimen pioneered by Dobbs et al.³⁰ advises gradual reduction of the talonavicular joint by manipulations suggestive of a “reverse Ponseti” method. This regimen minimizes surgery, requiring only pin fixation of the talonavicular articulation with percutaneous heel cord release.

Orthoses usually are advised after surgery to passively maintain correction. No literature supports the use of one orthosis over another. FO, supramalleolar orthosis (SMO), and AFO designs that incorporate support of the medial longitudinal arch are acceptable.

Calcaneovalgus foot

This positional variation is a frequent finding among newborns and must be differentiated from CVT. The incidence of calcaneovalgus probably is much greater than the reported 1:1,000 live births,^106,108 as it ordinarily resolves spontaneously and therefore may never attract medical attention. It is common in the firstborn of young mothers and is thought to be the result of intrauterine packing. No inheritance patterns are known.

The forefoot is abducted and dorsiflexed with the dorsum lying against the anterior leg, and the heel is in calcaneus with valgus. In severe cases, the ankle cannot readily be plantarflexed much beyond neutral. Overall, however, the foot is flexible. The heel and forefoot can be passively corrected into varus, and the entire foot can be moved as a unit into plantarflexion/dorsiflexion through the ankle joint. This flexibility and the position of the heel in calcaneus rather than equinus distinguish calcaneovalgus from congenital vertical talus. Radiographs are not ordinarily necessary, but the maximum plantarflexion lateral view can be reassuring.

Kite⁶⁰ pointed out the association of external rotation contractures of the hips with calcaneovalgus foot. Wetzenstein¹⁰⁶ noted the association with flexible flatfoot in later life. Congenital posteromedial bowing of the tibia is sometimes associated. It initially can cause some diagnostic confusion because a normal foot can have the cosmetic appearance of calcaneovalgus when significant posteromedial bowing is present.

Treatment of the calcaneovalgus foot begins with passive stretching. If the ankle cannot be easily plantarflexed beyond neutral, retention taping, casting, or bracing is indicated. A molded AFO with ankle positioned in plantarflexion and the foot in adduction is often used. No literature supports one orthosis over another.