Introduction
The pediatric foot presents a wide spectrum of normal and developmental variants, from congenital abnormalities in otherwise healthy individuals, to complex problems resulting from a generalized developmental abnormality or a broader syndrome. Generally speaking, patients who have a stable, plantigrade foot should initially be treated with a course of non-operative management. Conversely, patients with deformities that create pain or difficulty with ambulation are more often managed with surgical intervention.
Normal Variation
The “normal” shape of the pediatric foot is, at best, a moving target. Normal arch height is not well defined, although in infancy the foot is normally flat, with the arch gradually rising over the first five years or so. The shape and posture of the foot does not necessarily indicate which pathologies will occur in it. Differentiating a normal variant from a pathological foot is based upon an assessment of the complete picture, including the foot position, the patient’s symptoms, physical examination, and radiographic findings.
Accessory ossicles are a common radiographic finding. In fact, more than 20% of children have an accessory bone on radiographic imaging1. These are generally an incidental finding and most are of limited or no clinical significance. The os trigonum and os naviculare will be discussed in further detail as they do cause occasional symptoms.
Os Trigonum
The medial and lateral posterior processes of the talus appear between eight and 11 years of age and then join to the talus in the subsequent year. The posterolateral process forms the lateral border of the groove for the flexor hallucis longus (FHL) as it courses behind the ankle2. In approximately 13% of patients the posterolateral process remains unfused as the os trigonum (Figure 20.1).
Figure 20.1 Lateral radiograph demonstrating an os trigonum.
Injury to the os trigonum typically occurs in patients who perform activities that require maximal plantar flexion, such as ballerinas who dance en pointe. However, a single traumatic event involving extreme plantar flexion of the ankle can injure the os trigonum. The patient presents with posterior ankle pain. On physical examination, forced ankle plantar flexion reproduces the pain, which must be distinguished from FHL tenosynovitis, which is also frequently seen in ballet dancers. Careful examination can often identify FHL tenosynovitis, which typically causes tenderness in the posteromedial ankle on deep palpation over the FHL tendon when the hallux is put through a range of motion. However, in the acute setting it may be difficult to distinguish between the diagnoses on examination alone.
Radiographs will show the os trigonum. A true os can be distinguished from a fracture of the posterior process by its smooth, well-corticated margin. A fracture has a rough, irregular border. If the diagnosis is unclear a CT or MRI scan can be utilized to further evaluate the posterior ankle. CT is useful for distinguishing an os from a fracture. MRI will demonstrate an increased signal if the os is injured, as well as in the case of tenosynovitis of the FHL tendon.
Treatment of a painful os trigonum starts with a period of immobilization with a cast or walking boot. If the pain persists despite immobilization, excision of the os using either an open or arthroscopic approach is appropriate.
Accessory Navicular
The presence of an accessory navicular has an autosomal dominant inheritance pattern with incomplete penetrance4. The reported prevalence is near 10%2, thus an accessory navicular is often an incidental finding, although it can become symptomatic. An accessory navicular may be classified as type I in which an ossicle exists in the substance of the posterior tibial tendon, type II in which there is a distinct synchondrosis between the main body of the navicular and the accessory bone, and type III in which there is a “cornuate navicular” or enlarged medial process of the navicular.3
Despite clinical experience often associating a painful accessory navicular with pes planovalgus, a study evaluating the relationship of the accessory navicular to the development of a pediatric flat foot showed that the accessory ossicle does not contribute to the development of a flat foot6. The histology of a painful accessory navicular has shown microfracture through the cartilaginous synchondrosis, acute and chronic inflammation, and cellular proliferation indicating attempted repair5.
The child with a symptomatic accessory navicular presents with pain over the medial tuberosity at, or near, the insertion of the tibialis posterior tendon. The pain may be especially prominent over the plantar medial aspect of the navicular tuberosity, not just over the medial edge. The pain may be increased with pressure from tight-fitting shoes.
X-rays can be used to classify the type of accessory navicular. An external oblique radiograph(Figure 20.2), the opposite of the usual internal oblique, best visualizes the synchondrosis or bony ossicle. Important to surgical planning is that it is primarily plantar and proximal to the navicular tuberosity on the lateral radiograph.
Figure 20.2 External oblique radiograph demonstrating type II accessory navicular.
The initial treatment of a symptomatic accessory navicular is with padding or stretching of the shoe over the bony prominence, and the avoidance of tight shoes. If there is an associated planovalgus deformity, an orthosis with a medial heel wedge, to induce varus, and an arch support may help. However, the arch support may press directly on the bony prominence of the navicular, unless specifically designed with a padded flange to protect the prominence. If orthoses fail a period of immobilization in a short-leg walking cast or a walking boot is tried.
If non-operative treatment fails, surgical management involves excision of both the painful ossicle and prominent medial navicular tuberosity. The ossicle is carefully dissected from the surrounding tendon, the prominent navicular tuberosity is removed with a micro-saw, and the tendon is reconstructed for maximal functional outcome. The redundant tendon is advanced and maximally tightened into the navicular and surrounding soft tissues, with the foot held in inversion, in order to maximize tibialis posterior function. Similar to the classic Kidner procedure, the tendon must be advanced to prevent iatrogenic dysfunction and weakness of the tibialis posterior muscle, although there has been disagreement about this in the literature7.
Osteochondroses
Sever’s Disease
Sever’s disease is believed to be an overuse injury of the calcaneal apophysis. The usual presentation is in an active child who participates in running and jumping activities. Generally, the child will complain of pain over the posterior or plantar aspect of the heel, aggravated by activity. The heel is tender to palpation. Treatment is universally non-operative and the disease process is self-limited, although not necessarily quick to resolve. Treatment consists of heel wedges to elevate the heel and reduce the tension in the plantar fascia and the tendo Achillis (TA) through the growth plate. Stretching of the TA is helpful but it can be difficult to get the child to participate in this on a regular basis. Forced rest with cast immobilization for four to eight weeks may assist recalcitrant cases. The disease will eventually resolve when the apophysis closes.
Köhler’s Disease
Köhler’s disease is an osteochondrosis of the navicular, of unknown cause. There are two predominant theories as to its etiology:
1. The location of the navicular coupled with the fact that it ossifies relatively late makes it susceptible to mechanical compression injury.
2. Periodic compression of the navicular leads to AVN.
Köhler’s disease most commonly presents in children around the age of five and is more common in boys than girls. Few patients give a history of specific trauma relating to the onset. They usually complain of pain, tenderness, and swelling in the midfoot. Radiographs demonstrate a flattened, sclerotic navicular (Figure 20.3).
Figure 20.3 Anteroposterior radiograph demonstrating normal navicular (right) and the flattened, sclerotic navicular typical of Köhler’s disease (left, with arrow).
Treatment is non-operative because the symptoms and radiographic changes spontaneously resolve over 18 months to three years. Restricted weight bearing and the use of walking casts, or boots, are prescribed according to the patient’s pain.2
Freiberg’s Infraction
Freiberg’s disease is an osteochondrosis of the metatarsal head, most commonly of the second metatarsal, although it also occurs in the third. The cause is poorly understood but it is believed to be a result of AVN. It usually occurs in adolescents after 13 years of age and is more common in girls than boys.
The patients usually complain of pain underneath the metatarsal head. Radiographs show subchondral lucency and collapse of the metatarsal head (Figure 20.4).
Figure 20.4 Radiograph demonstrating the typical findings of Freiberg’s infraction of the third metatarsal head.
Initial non-operative treatment is with a hard-soled shoe, boot, or cast. A metatarsal pad can also be used to help offload pressure from the metatarsal head. If the pain persists, surgical intervention may be warranted.
Several surgical options exist for the treatment of Freiberg’s disease. The affected area is predominantly on the dorsal aspect of the metatarsal head and the plantar condyles are relatively spared. A dorsal closing wedge osteotomy will rotate the better preserved plantar cartilage into the area of articulation with the phalanx. Alternatively, if the dorsal cartilage is in satisfactory condition, the collapsed segment of the metatarsal head is curetted and the resulting defect filled with cancellous autograft to buttress the subchondral bone and cartilage joint surface. In the latter case metatarsal shortening, for example with a Weil osteotomy, may be attempted in an effort to decrease the joint pressure. Finally, in select cases, metatarsal head allograft or metatarsal head resection may be attempted9.
Congenital Deformity
Congenital Talipes Equinovarus (Clubfoot)
Clubfoot is a common congenital deformity found in one to two of every 1000 live births. It is more frequent in males. While clubfoot tends to occur in multiple members of the same family, it does not follow typical genetic inheritance patterns. The majority of congenital talipes equinovarus (CTEV) cases are idiopathic, although it may result from an underlying neuromuscular condition or syndrome. Thus a patient with CTEV, particularly if it is rigid, should be evaluated for neuromuscular disease, including arthrogryposis, diastrophic dwarfism, Möbius syndrome, Streeter’s dysplasia, spinal dysraphism, and fetal alcohol syndrome.
The congenital idiopathic clubfoot is diagnosed clinically. Patients have a consistent and predictable pattern of deformity, comprised of cavus, forefoot adductus, hindfoot varus, and equinus (Figure 20.5). Furthermore, there is dysplasia of the talar neck, which consistently deviates in a medial and plantar direction. The navicular is subluxed medially and there is internal rotation of the calcaneus.
Figure 20.5 A child with bilateral clubfoot deformity.
Several etiologies have been proposed for the idiopathic clubfoot. These include a primary germ plasm defect, soft tissue abnormalities with a “retractive fibroblastic response,” and developmental arrest of the foot. None of these theories fully explains all of the features of CTEV encountered in practice, and for this reason it is believed that the etiology is multifactorial2.
The initial treatment of the idiopathic clubfoot has alternated between operative and non-operative. At the current time there is a consensus for early non-operative treatment13–15. By contrast, the neuromuscular clubfoot is typically rigid, and resistant to non-operative correction.
The Ponseti method is based upon weekly changes of a long-leg cast, with gradual correction by manipulation of each component of the deformity. The acronym “CAVE” describes the order of correction and also conveniently defines the clinical deformity. It stands for Cavus, Adductus, Varus, and Equinus. Correction is usually achieved with the use of five or six casts. Nevertheless, aggressive attempts to manipulate and cast a rigid equinus deformity can result in dorsiflexion through the midfoot and the creation of a rocker bottom foot. Thus TA tenotomy is required in over 85% of patients in order to achieve adequate correction of the equinus. The tenotomy is delayed until satisfactory correction of all other components of the deformity have been achieved.
After the completion of cast treatment, the patient is placed into a foot abduction orthosis, the Denis–Brown bar and shoes, to maintain correction. The brace holds the feet in 70° of external rotation and 5 to 10° of dorsiflexion. It is used all the time for three to four months and thereafter during sleep for a period of two to four years. Compliance with use of the brace is important in achieving a successful outcome. Fifteen to 20% of patients treated successfully with the Ponseti method require subsequent lateral transfer of the anterior tibial tendon to correct dynamic forefoot supination during swing phase. At a mean follow-up of 34 years, 78% of 71 idiopathic congenital clubfeet, in 45 patients, treated with the Ponseti method had good or excellent outcomes, even though 30 of the 71 required later anterior tibial tendon transfer14.
An alternative non-surgical treatment is with the French physiotherapy, or “functional” method. This has proven to be equally effective16. The functional method requires daily manipulation of the foot for two months. The foot is strapped with non-adhesive strapping in between manipulation sessions. After approximately two months the manipulation is reduced to three times per week for up to six months. Nighttime splinting is used for two to three years thereafter. This method of treatment is not as popular as the Ponseti method as it requires daily treatment, with considerable parental training and participation.
A prospective comparison of these two non-surgical treatment methods included 267 feet in 176 patients treated with the Ponseti method and 119 feet in 80 patients treated with the functional method. Initial correction was similar for the two groups with 94% correction in the Ponseti group and 95% in the functional group. In the Ponseti group, 37% of feet relapsed and two-thirds of these required surgical intervention. Twenty-nine percent of the feet in the functional group relapsed, and all of these required surgical intervention. Good results were obtained in 72% of the feet treated with the Ponseti method and 67% of the French physiotherapy method. The study concluded that while a trend demonstrating better results with the Ponseti method was identified, it was not significant. The authors further noted that parents chose the Ponseti method twice as often as the functional method17.
Idiopathic clubfeet that are resistant to non-surgical treatment and neuromuscular clubfeet require surgical treatment at about one year of age, once the child is able to walk. There are multiple surgical variations, but all consist of a series of soft tissue releases to correct the foot position. The calcaneofibular ligament, posterior talofibular ligament, and superficial deltoid ligament are released, the TA and medial tendons (PTT, FDL, and FHL) are lengthened, and the tibiotalar, subtalar, and talonavicular capsules are released18.
Long-term complications following clubfoot surgery usually can be considered as either the result of undercorrection, or recurrence, on the one hand, and overcorrection on the other. Dorsal subluxation of the navicular, valgus overcorrection, a dorsiflexed first metatarsal, or dorsal bunion, and ankle pain and stiffness are all recognized complications, which may require further surgical intervention21.
Congenital Vertical Talus
A congenital vertical talus is defined by a severely plantar flexed talus with dorsal dislocation of the navicular. The fixed hindfoot equinus produces a rocker-bottom deformity of the foot with a tight TA. The underlying etiology of the vertical talus is unknown but the deformity is often associated with neuromuscular conditions such as myelomeningocele, arthrogryposis, prune-belly syndrome, spinal muscular atrophy, neurofibromatosis, congenital dislocation of the hip, Tasmussen’s syndrome, and trisomy 13–15 and 18.
On examination there is a rocker-bottom deformity of the foot, the talar head is prominent in the plantar-medial foot, and the heel is in equinovalgus, with a dorsiflexed and abducted forefoot. The lateral x-ray shows a severely plantar flexed talus, with the longitudinal axis of the talus lying almost parallel to that of the tibia. The calcaneus lies in equinus. As the navicular does not ossify until three years of age, its dorsally dislocated position is not seen. Its position must be inferred from the dorsally dislocated position of the midfoot and forefoot. If a congenital vertical talus is suspected a forced plantar flexion radiograph is taken. If a line drawn along the longitudinal axis of the talus passes plantar to the midfoot and first metatarsal, this indicates that the navicular and midfoot dislocation is fixed, confirming the diagnosis (Figure 20.6). If the line passes through the first metatarsal, there is a congenital oblique as opposed to vertical talus. Thus while both an oblique and vertical talus have a similar clinical appearance, with a rocker-bottom deformity, the difference between the two is that the midfoot is reducible with an oblique talus.
(a) A lateral radiograph showing a congenital vertical talus.
(b) Forced plantar flexion radiograph demonstrating persistent dorsal midfoot subluxation on the plantar flexed talus, confirming the diagnosis of congenital vertical, as opposed to oblique, talus.
Recent studies have demonstrated considerable success with manipulation and serial casting to correct the deformity in both the idiopathic and rigid vertical talus associated with neuromuscular or genetic disease22–23. The technique involves weekly serial casting with gradual deformity correction, similar to the management of a clubfoot deformity. As in the treatment of a clubfoot, all components of the deformity are corrected by manipulation and casting, except the equinus. With a dorsal force imparted on the plantar-medial aspect of the talar head, the midfoot and forefoot are manipulated into a plantar flexion and inversion, in order to gradually reduce the navicular onto the plantar flexed talus. After several casts, talonavicular reduction is confirmed radiographically. If the talar–first metatarsal angle in maximal forced plantar flexion is less than 30°, talonavicular stabilization in a reduced position is held with a percutaneous Kirschner wire, with or without a small talonavicular arthrotomy to confirm anatomic alignment of the joint. The TA can then be released percutaneously to correct the equinus deformity. The final cast and wire are left in place for approximately four weeks at which point the wire is removed and bracing is instituted to prevent recurrence.
If serial casting fails, presentation is delayed, or if the deformity is rigid and irreducible, surgery is performed at around one year of age. The surgery consists of:
1. reduction of the navicular onto the talus by releasing the capsular structures and the tibialis anterior tendon
2. lengthening of the long toe extensors and peroneal tendons
3. reduction of the cuboid onto the calcaneus through release of the bifurcate ligament and capsular structures
4. transfer of the tibialis anterior tendon to the neck of the talus
5. temporary pin fixation of the talonavicular joint to maintain alignment.
This is followed by six to twelve weeks in a cast. In older children, excision of the navicular and a Grice extra-articular talocalcaneal arthrodesis may be necessary.
Neglected deformities are challenging. It is usually not possible to correct the foot with joint-sparing surgery in the older child with a symptomatic foot. A corrective triple arthrodesis with soft tissue releases is usually necessary.
Calcaneovalgus Foot
A calcaneovalgus foot in a newborn occurs as a result of intra-uterine molding. The foot will be in extreme dorsiflexion with eversion of the hindfoot and abduction of the forefoot. The calcaneovalgus foot is passively correctable and is treated with stretching and observation.
Flexible Flat Foot (Pes Planovalgus)
It is important to distinguish between a flexible and rigid flat foot. A flexible flat foot will have normal or excessive mobility of the subtalar joint. When the child is non-weightbearing the arch should reconstitute. In a flexible flat foot when the patient moves up onto tip-toes the heel should move into varus. A rigid flat foot does not correct.
In infancy the foot is normally flat. The arch gradually constitutes over the first five years or so, although in 15 to 20% of children the flat foot persists into adulthood. Flexible flat foot is a common cause for parental concern, although the child is rarely symptomatic. It is almost always bilateral and there is often a family history. It is associated with rotational abnormalities of the lower extremities and may be associated with ligamentous laxity. Typically the medial arch is flat, with a valgus hindfoot and an abducted forefoot (Figure 20.7).
