Pediatric foot deformities encompass a range of conditions affecting the bones, tendons, and muscles of the foot. Clubfoot, a prevalent and significant pediatric foot deformity, is discussed in its own chapter. Here, a brief review is presented of some of the other more commonly seen conditions: metatarsus adductus, tarsal coalitions, accessory navicular, planovalgus foot deformity (planovalgus), and cavas foot deformity (cavovarus).

Metatarsus Adductus

Metatarsus adductus describes a congenital deformity in which the forefoot is turned inward relative to the hindfoot (Figure 1). Metatarsus adductus may be "flexible" (the foot can be straightened by the examiner’s hand) or "nonflexible" (in which the foot cannot be straightened by hand).

The forefoot comprises the 5 metatarsal bones and 14 phalangeal bones. In metatarsus adductus, these bones are deviated medially. Thus, the inside border of the foot is concave, the outside or lateral border of the foot is convex, while the hindfoot remains in a relatively neutral position. The angulation is at the tarsometatarsal joint.

Metatarsus adductus is usually noted soon after birth, but can present at any age. Commonly, the parents or pediatrician of a child with metatarsus adductus will notice in-toeing incidentally. Parents may also comment regarding a wider gap between the first and second toes. This often suggests a mild flexible deformity that is observed to actively correct when the lateral border of the foot is tickled.

The exact cause of metatarsus adductus is not known, but it is thought to be a “packaging” disorder, or a result of positioning inside the uterus.

Metatarsus adductus is the most common congenital foot deformity occurring in approximately 1 of every 1000 live births, with equal frequency in males and females. Metatarsus adductus is bilateral in approximately 50% of cases.

Metatarsus adductus is defined on clinical examination by the heel bisector line. To determine this, a line is drawn on the plantar foot starting from the center of the heel directly vertical past the toes. In normal alignment, this line will exit the forefoot through the second webbed space, between the 2nd and 3rd toes (Figure 2). In metatarsus adductus, the line will exit more laterally in the forefoot. The greater the number of toes on the same side of the line as the great toe, the more severe the metatarsus adductus.

For patients presenting with in-toeing, one must also examine for and consider femoral anteversion and internal tibial torsion (see Pediatric Lower Limb Deformities).Another foot deformity called skew foot also presents with adduction of the forefoot, but unlike metatarsus adductus there are additional deformities of the midfoot in abduction and hindfoot valgus. Congenital hallux varus differs from metatarsus adductus in that the medial deviation is isolated to the great toe.

There is always full range of motion of the ankle and subtalar joint with metatarsus adductus. Stiffness in these areas should lead the examiner to consider other diagnoses.

Figure 2. The heel bisector line identifies the severity of metatarsus adductus.

Although X-rays are not usually necessary to evaluate metatarsus adductus, they are recommended in the case of nonflexible metatarsus adductus, and in older children.

In the majority of cases, metatarsus adductus is mild and flexible. This will improve over time, up to about 4 years of age. Parents can perform stretching and stimulation of the foot.

If the metatarsus adductus is only partly flexible or rigid, serial stretching casts are sometimes necessary to achieve correction. Parents can be reassured that good results are expected with mild or moderate deformity and no functional limitations. It is rare that surgery is needed for correction of metatarsus adductus, reserved for the most severe rigid cases or cases resistant to serial casting. Soft tissue releases of the abductor hallucis and the first tarsometatarsal joint capsule followed by more casting may be indicated. If a child is older with rigid adductus osteotomies may be considered.

Metatarsus adductus is associated with other presumed packing deformities like torticollis and developmental dysplasia of the hip. It is important to examine the entire child when they present with a congenital foot deformity. Risk factors include twin pregnancy or oligohydramnios.

Tarsal Coalition

Tarsal coalition describes the abnormal connection between two or more tarsal bones that limits range of motion and causes a rigid flat foot.

There are seven tarsal bones. These include the talus, calcaneus, navicular, cuboid, and the three cuneiforms, the medial, middle (or intermediate), lateral (see Figure 3).

Figure 3. The tarsal bones, as seen from above.

The abnormal connection between these bones may be composed of bone, fibrous tissue or cartilaginous tissue. This occurs embryologically due to failure of segmentation. Any abnormal connection between the tarsal bones can result in decreased range of motion of the subtalar joint, thereby limiting inversion and eversion of the heel.

Clinically, a tarsal coalition may present as a rigid flat foot. Patients usually present with a chief complaint of pain over the sinus tarsi, an aching pain along their arch, or pain under their medial malleolus that is worse with activity and alleviated with rest. The most common age for presentation of tarsal coalition is around 8 to 16 years, typically becoming symptomatic in adolescence. Some children may present with the complaint of recurrent ankle sprains or progressive flat foot.

On physical exam, patients will often have a rigid subtalar joint. This is best assessed with the foot held in neutral dorsiflexion and then applying an inversion and eversion force to evaluate subtalar motion. With standing toe rise there is no inversion of the hindfoot due to limited subtalar motion. Those with calcaneonavicular coalitions often have more preserved motion since the two connected bones do not cross the subtalar joint.

Imaging studies are required for diagnosis of a tarsal coalition. AP, lateral, oblique and, Harris axial views should be obtained. The Harris view is obtained by having the patient stand on the cassette with the x-ray beam angled between 35 and 45 degrees and will detect any coalition between the talus and calcaneus.

A calcaneonavicular coalition is best seen on an oblique x-ray of the foot (Figure 4). It may also be noticed on a standing lateral x-ray of the foot, seen as an elongated anterior process of the calcaneus. This is known as the “ant-eater sign.” A talocalcaneal coalition may also be appreciated on the lateral radiograph by a finding known as the “C-sign.” This is a “C” shaped line that is formed by the dome of the talus and the sustentaculum tali of the calcaneus (Figure 4). However, it is important to note that these findings have a low sensitivity, and their absence does not rule out the presence of a tarsal coalition.

The best imaging technique to evaluate for tarsal coalition is a CT scan. The CT can also aide in surgical planning and is used to look for other coalitions if surgery is being considered. If the history and physical exam are consistent with a coalition but the CT scan is non-diagnostic an MRI may reveal a fibrous coalition.

Most commonly, tarsal coalitions are seen between the talus and calcaneus, and between the calcaneus and the navicular bones. These two combinations account for about 90 percent of all tarsal coalitions. Other described locations are between the talus and navicular, the calcaneus and cuboid, the navicular and cuneiform, and between a cuneiform and metatarsal, however these are uncommon. In about half of cases a tarsal coalition will be present bilaterally.

In the case of rigid flat foot, it is also important to consider other causes such as juvenile idiopathic arthritis, septic arthritis, osteomyelitis, and other bone lesions for example an osteoid osteoma.

Any constitutional symptoms should prompt investigation into one of the differential causes of a rigid flatfoot. Pain worse in the morning rather than after activities may indicate a rheumatologic cause. There are syndromes associated with tarsal coalitions such as Apert and Crouzon syndrome and any dysmorphic features should be noted.

Up to 25 percent of tarsal coalitions are thought to become symptomatic, and only those that cause symptoms should be treated. First line treatment includes symptom management with activity modification, orthoses, and anti-inflammatories as needed. Second line treatment is to try cast immobilization for a period of about 4-6 weeks.

If non-operative treatment fails to provide long-term pain relief, surgery can be considered. Prior to surgery, a CT scan should be obtained to evaluate for the presence of a second coalition. Surgery begins with resection of the coalition with placement of interposed tissue (muscle or fat) to help prevent its reformation. If there is a significant foot deformity associated with the coalition, consideration can also be given to osteotomies for deformity correction. In cases where there is degeneration of the joint involved in the coalition, or if a subtalar coalition is particularly large, a fusion of the joint is considered; resection in these cases may lead to poorer outcomes.

There are no preventative measures for tarsal coalition. It is associated with certain other congenital abnormalities like fibular hemimelia, and syndromic associations.

Accessory Navicular

An accessory navicular is a prominence of the navicular on the plantar medial surface and is considered a normal variant (Figure 6).

The navicular bone sits along the medial aspect of the foot and articulates with the talus, the cuneiforms, the cuboid, and the calcaneus. An accessory navicular is clinically defined as an enlargement of the navicular bone along its plantar medial surface. This enlargement can be a separate piece of bone connected to the native navicular body by fibrous or cartilaginous tissue, or it can simply be an enlargement of the native bone beyond its normal size (as the “extra” part of the navicular can be completely ossified to the true navicular.)

Patients with a symptomatic accessory navicular often present with pain and tenderness over the medial palpable bony prominence. They may also have a flat foot, however no cause and effect relationship between an accessory navicular and a flat foot has been proven. Often the pain is aggravated by tight shoes that press against the medial prominence.

Plain radiographs are useful in diagnosing an accessory navicular as they can often be seen on standing AP and lateral views. A lateral oblique x-ray of the foot may also be useful to visualize an accessory navicular (Figure 7).

This is the most common accessory tarsal bone seen in the foot with a prevalence of approximately 10%. When present, accessory navicular bones are often bilateral.

A pain and tenderness at the navicular insertion may be from tendinitis of the tibialis posterior tendon (with or without an accessory navicular). A bipartite navicular can also be seen as a separate osseous navicular structure; it is distinguished from an accessory navicular by the dorsal displacement of the separate fragment and maintained articulation with the talus. Less commonly a fracture or stress fracture of the navicular may be on the differential. An avulsion fracture of the accessory navicular can also occur with an eversion mechanism; the clinical exam and imaging should be scrutinized for acute changes in the cases of trauma with focal findings. Plantar fasciitis can also present with pain along the medial foot.

If the patient has a rigid flatfoot consider alternative diagnoses such as the presence of a concomitant tarsal coalition or underlying inflammatory arthropathy.

Patients who present with a painful accessory navicular are first treated with non-operative measures. First line measures include activity modification and shoe wear modification. If there is a planovalgus foot deformity concomitantly, a valgus correcting orthotic may help relieve pressure over the area. If this fails to relieve symptoms, rigid immobilization in a short leg cast can be done for a period of 4-6 weeks followed by gradual return to activities.

If extensive non-operative measures fail to provide long-term relief, surgical excision may be considered. Surgical options consist of removal of any ossicle that may be present along with the bony prominence of the main body of the navicular bone. The ossicle can sometimes exist within the substance of the posterior tibialis tendon, which must be taken into consideration when performing surgical excision. Others have described removal of the ossicle and advancement or re-routing of the tibialis posterior. While good results are reported with either approach, it should be noted that this is based on small, low level of evidence studies.

Planovalgus Foot Deformity

Pes planovalgus is defined as excessive valgus alignment of the heel (hindfoot) with loss or flattening of the medial longitudinal arch of the foot. It is commonly known as “flatfoot,” (see Figure 8). In this condition, the forefoot is abducted outward but often rotated inward, or supinated, in relation to the hindfoot. A planovalgus foot is also called a flatfoot. This may be a physiologic variant or due to underlying pathology. The focus here will be on flexible pes planovalgus flatfoot.

A flat foot is a combination of foot deformities that includes a valgus hindfoot and an abducted and supinated forefoot. In pes planovalgus there is flattening of the medial longitudinal arch of the foot along with the excessive hindfoot valgus. The normal alignment of the hindfoot can be up to 5 degrees of valgus. In pes planovalgus the forefoot is abducted and supinated in relation to the hindfoot. Young children develop a medial longitudinal arch over time and this flattening can improve.

Patients will present with loss of the medial longitudinal arch and a valgus hindfoot. In order to assess the degree of forefoot supination, the hindfoot must be corrected to a neutral position. If both deformities can be corrected to a neutral position, the flat foot is said to be flexible.

Another way to assess for flexibility is to have the child stand on their toes. If when standing on their toes the medial arch re-constitutes and the heel inverts, the deformity is said to be flexible. A flexible flat foot is caused by an equinus contracture due to a gastrocnemius muscle contracture and/or a tight Achilles tendon. To assess for the degree of gastrocnemius or Achilles tightness, the hindfoot must again be corrected to a neutral position. One may then perform a Silfverskiöld test to further assess where the tightness is originating. This test is performed by comparing the amount of maximal ankle dorsiflexion with the knee flexed versus extended. If more ankle dorsiflexion was achieved with the knee flexed than with the knee extended, the primary tightness is from the gastrocnemius muscle. If dorsiflexion is limited in both knee extension and knee flexion, the contracture is of the Achilles tendon itself also called the heel cord. This is important when considering surgical intervention.

Imaging studies are usually not needed for flexible flat foot diagnosis, but may be required if other etiology is suspected. All x-rays should be obtained while the patient is bearing weight. The lateral radiograph can be helpful to quantify the deformity using the talus-first metatarsal angle, also known as the Meary angle (Figure 9). This is measured by placing a line along the longitudinal axis of the talus and a second line along the longitudinal axis of the first metatarsal. The angle formed by the intersection of these two lines should be near zero in a normal foot.

The incidence of flexible flat foot is not known, likely due to the fact that this is considered within natural physiologic variation. It is common in infants and children, while up to 20% of adults have a flexible flatfoot. A physiologic flat arch in a young child that is asymptomatic is likely to improve over time without intervention.

Underlying disorders that can be associated with a flatfoot include: accessory navicular, ligamentous laxity, neurologic or neuromuscular disorders, and obesity.

If a patient presents with a rigid flatfoot deformity the possibility of other diagnoses must be considered. These can include, but are not limited to: tarsal coalition, spastic peroneal flatfoot, inflammatory arthropathy, previous trauma, and congenital vertical talus.

If the patient has a rigid flatfoot you should consider alternate diagnoses such as a tarsal coalition or underlying inflammatory arthropathy.

Flexible flat foot may also be thought of as a normal anatomic variation and not a disabling deformity. No treatment is needed for asymptomatic flat feet. If children or adolescents are symptomatic, over the counter shoe inserts may help relieve symptoms but will not change the shape of the foot. If the child has a tight Achilles or gastroc-soleus-complex, an Achilles stretching program should be initiated. Surgery is rarely indicated in the treatment of flexible flat foot. When performed it may consist of tightening of the soft tissues medially, tendon lengthening and transfer, and osteotomies to lengthen the lateral column of the foot.

In the setting of primary tightness of the gastrocnemius muscle (as found with a positive Silfverskiöld test), a gastrocnemius recession can be performed to selectively lengthen the gastrocnemius muscle. If the Silfverskiöld test is negative, but passive dorsiflexion is limited, a tendoachilles lengthening is performed.

Cavus Foot Deformity

A cavus foot is one with a high arch in the midfoot due to pronation of the forefoot on the hindfoot. The hindfoot can be in neutral (isolated cavus) but is often in varus (cavovarus). In most cases, a cavovarus foot is secondary to an underlying neurologic disorder which causes a muscle imbalance. Cavus may also be a result of residual clubfoot deformity. Cavus may rarely result from trauma such as compartment syndrome, sciatic nerve injury, or tendon lacerations.

A cavus foot is the result of muscle imbalance with weak intrinsic muscles that become contracted. Cavovarus foot deformity is combination of the high arch with forefoot pronation and inversion or varus of the hindfoot. The midfoot may be adducted or neutral. The ankle may be plantarflexed, neutral, or in dorsiflexion. There is often concomitant external tibial torsion. Another type of cavus foot deformity is calcaneovarus where the entire arch is elevated off the ground from medial to lateral.

Often, patients will present with a complaint of recurrent ankle sprains or ankle instability. This instability can be the result of actual muscle weakness, loss of sensation over the foot, or from the deformity itself. It is also common for a callus to form along the lateral base of the fifth metatarsal due to the patient walking on the lateral border of their foot. It is vital to obtain a detailed neurologic exam as well as to obtain a detailed family history in these patients to evaluate for an underlying cause. Patients may have asymmetric muscle bulk or a leg length discrepancy. An examination of the spine is important to look for signs of spinal dysraphism.

To evaluate for the deformity itself, providers can look for what is called the “Peek-a-Boo” sign. This sign occurs when the medial aspect of the heel can be seen while looking from straight on, as the patient is standing (Figure 10).

An assessment of both the hindfoot and the forefoot are important to ascertain the flexibility of each of these segments. The Coleman block test can be used to assess the flexibility of the hindfoot by placing a block under the lateral foot and metatarsals and allowing the medial forefoot to hang free (see Figure 11). If the varus position of the hindfoot corrects it is flexible.

Upon presentation, plain radiographs are often obtained. A cavus foot will have an increased calcaneal pitch (>30 degrees), which is determined by the angle between the long axis of the calcaneus and a line parallel to the bottom of the foot. The Meary angle can also indicate a cavus foot if it angles upward with a magnitude of more than 4 degrees (Figure 12).

Figure 12: Pes Cavus on lateral standing x-ray. Meary’s angle (red) and the calcaneal pitch angle, between the long axis of the calcaneus and the bottom of the foot (green), are shown.

An AP Pelvis radiograph should be obtained to fully evaluate the patient with a cavovarus foot, as one cause of the foot deformity, Charcot-Marie-Tooth, is associated with hip dysplasia. Likewise, spinal radiographs should be obtained to exclude scoliosis in patients with a cavovarus foot.

Cavus foot deformities are associated with neuromuscular disorders. The most common neuromuscular disorder causing a cavus foot deformity is Charcot-Marie-Tooth (CMT) disease. CMT is the most common hereditary motor sensory neuropathy. In CMT, the peroneus longus is the last muscle to atrophy and weaken. Unopposed pull of this muscle (ie, while it is relatively strong and other muscles are weak) will cause hindfoot varus and a cavus deformity to the arch. Rarely no underlying etiology can be identified for a cavus foot.

There are several causes of cavus foot deformities with some being more common in bilateral deformities. These can include: CMT disease, Friedrich’s ataxia, spinal muscular atrophy (SMA), myelomeningocele, cerebral palsy (CP), and recurrent clubfoot. A unilateral cavus foot deformity can have the same causes, but should also consider previous trauma, peripheral nerve injury, poliomyelitis, tendon injury, or prior compartment syndrome.

A detailed evaluation of strength, sensation, reflexes, and vascularity is required. A new or progressive cavovarus foot deformity should raise concern for underlying neurologic abnormalities and a referral to neurology and advanced imaging of the spine and brain with MRI is indicated. A cavovarus foot should be considered a manifestation of an underlying neuromuscular disorder until proven otherwise.

The first step in treatment of a cavus foot deformity is to diagnose and treat any potential underlying cause (i.e. neuromuscular disorder). Non-operative treatment options for a cavus foot include arch supports and shoe modifications. However, many severe cavus foot deformities in children do require surgery in the long term as the deformity is often progressive.

Indications for surgery are progressive deformity, pain, pressure injuries, and gait instability. When deciding on surgical management, it is important to understand how rigid or flexible the deformity is and where. The hindfoot and forefoot are the important considerations and one may be flexible while the other stiff. This can be accomplished by using the Coleman block test as described. This test helps the examiner determine whether the deformity is forefoot or hindfoot driven, and what aspects of the foot need to be addressed during surgical reconstruction. There is not one surgical procedure for the management of a cavovarus foot, but rather there are many procedures that may be performed to address whatever aspects of the patient’s foot are contributing to the deformity.

Surgical treatment can be divided into these broad categories: soft tissue, osteotomy, arthrodesis. Contractures should be released and the soft tissues should be rebalanced in all cases. In flexible feet, this may be all the surgery that is required. In more advanced cases with stiffness or rigidity, osteotomies to correct the adaptive boney changes are required. Finally, in cases of advanced rigid deformities, older patients may consider fusion as a last resort

The biggest risk factor for a cavus foot deformity is an underlying neuromuscular disorder.

Miscellany

Metatarsus adductus has also been called “bean foot” due to the shape.

The navicular is known as the scaphoid of the foot. Both names refer to the “boat shape” of the bone (sharing roots with the word “navy” and “skiff”).

Key Terms

Cavus, cavovarus, metatarsus adductus, flatfoot, hindfoot, forefoot, Silfverskiöld test, tarsal coalition, rigid flatfoot, subtalar joint, calcaneonavicular joint, navicular, tarsal bones, tibialis posterior

Skills

Recognize the normal shape of the foot. Distinguish relationships between the forefoot, midfoot, hindfoot. Distinguish a flexible from a rigid flat foot. Be able to identify a cavus foot deformity. Understanding the “peek-a-boo” sign. Understand how to perform and interpret the Coleman block test. Recognize that there may be many normal anatomical variants in the foot with bony structure.