Foot and Ankle Conditions in Children and Adolescents

Robert F. Murphy, MD

Dr. Murphy or an immediate family member serves as a board member, owner, officer, or committee member of the Pediatric Orthopaedic Society of North America and the Scoliosis Research Society.

This chapter is adapted from Sawyer JR, Kelly DM: Foot and Ankle Conditions in Children and Adolescents in Chou LB, ed: Orthopaedic Knowledge Update: Foot and Ankle 5. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2014, pp 37-49.

ABSTRACT

The most common foot and ankle conditions in children and adolescents include accessory navicular, tarsal coalition, and flexible flatfoot. Painful symptoms associated with these conditions are usually self-limiting and can be successfully treated using conservative modalities such as an orthosis, activity modification, and physical therapy. Surgery usually is not necessary for these conditions, but it can be effective for relieving pain and improving function in the few of patients who have persistent symptoms and who have exhausted all conservative treatments. To provide the appropriate treatment for these patients, it is mandatory to identify the exact location and character of the symptoms on history, as well as perform a comprehensive physical examination. Appropriately obtained imaging modalities can help refine the diagnosis and guide the treatment plan.

Accessory navicular

Introduction

An accessory navicular (os naviculare) is a common condition found in the pediatric and adolescent foot and ankle and is often asymptomatic.¹ Three types exist (Figure 1). A type I accessory navicular is a small, round ossicle of bone that lies completely separate from the navicular within the substance of the tibialis posterior tendon at its insertion into the navicular. Type II typically is a larger bone that connects to the navicular tuberosity by a synchondrosis. A type II accessory navicular constitutes a large portion of the tibialis posterior tendon. Type III is similar to type II in appearance except for the absence of the synchondrosis; instead, the navicular is completely fused to the accessory ossicle.²

Clinical Findings

An accessory navicular is typically diagnosed in adolescent patients with progressively worsening medial midfoot pain. Occasionally, the symptoms begin with a sprain of the foot or ankle, and the pain often is exacerbated by sports activities or shoe wear. A flexible pes planovalgus deformity is present in 50% of patients with a symptomatic accessory navicular. The patient typically reports tenderness to palpation over the medial prominence. The pain often can be reproduced by resisted tibialis posterior tendon contraction by asking the patient to plantarflex and invert the foot. The patient and parents may be concerned about the size and appearance of the bump on the medial arch (Figure 2).

Radiographic Evaluation

Standing AP, internal oblique, and lateral radiographic views usually are sufficient for detecting the accessory bone, although a reverse (external) oblique radiograph of the foot may be helpful in identifying the accessory ossicle (Figure 3). It is important to identify any associated abnormalities, such as pes planus or a calcaneonavicular coalition. Advanced imaging such as CT or MRI is unnecessary unless there are concerns for concomitant pathology based on history or physical examination. In a patient with symptoms, a bone scan is likely to show signal intensity at the site of the ossicle in a type II deformity. MRI is excellent for defining the soft-tissue anatomy of the tibialis posterior tendon insertion and identifying a synchondrosis. A symptomatic accessory navicular sometimes is found on MRI obtained to determine the cause of ankle pain of unclear etiology. In a symptomatic accessory navicular, MRI often reveals edema in the synchondrosis and nearby bony structures.³

FIGURE 1 Illustrations showing the classification of the accessory navicular. A, Type I, in which a small, round ossicle is completely separate from the navicular. B, Type II, in which a larger ossicle is connected to the navicular by a synchondrosis. C, Type III, which is similar to type II except for the absence of a synchondrosis.

FIGURE 2 Clinical photograph showing a foot with an accessory navicular.

FIGURE 3 AP radiograph showing an accessory navicular. An external oblique view sometimes helps detect or fully delineate the accessory bone.

Nonsurgical Treatment

Patients with an insidious onset of symptoms often can achieve pain relief with activity modifications, wearing an over-the-counter soft orthosis, and/or using NSAIDs. A rigid arch-support orthosis can be painful because of increased contact pressure over the accessory navicular. Patients with associated flatfoot deformity and a contracture of the gastrocnemius or Achilles tendon may benefit from a supervised or independent stretching program. A period of immobilization in a walking cast or boot may help relieve symptoms that began acutely or are not resolved after other treatments. Most patients can be successfully treated using nonsurgical measures.¹

Surgical Treatment

Surgical treatment is an option if an extended course of nonsurgical treatment does not result in relief of symptoms. The original Kidner procedure involved excision of the accessory ossicle and advancement of the tibialis posterior tendon to the medial cuneiform. Satisfactory results have been reported with a modified Kidner procedure that entails simple excision of the ossicle and side-to-side repair, rather than advancement, of the tibialis posterior tendon.⁴^,⁵

The type of accessory navicular usually dictates the treatment plan. A type I accessory navicular ossicle can be simply excised through a longitudinal split in the tibialis posterior tendon. A type II or III deformity requires subperiosteal dissection from the tibialis posterior tendon insertion. Care should be taken to avoid violating the talonavicular joint capsule. The tibialis posterior tendon can be repaired in a side-to-side fashion. Resection of a large type II or III deformity may require nearly complete
detachment of the tibialis posterior tendon insertion to achieve adequate bony decompression. The detached tendon can be reattached to the residual navicular using bone tunnels or suture anchors (Figure 4). Recent literature has found no significant difference in outcomes or complications after simple excision with or without advancement of the tibialis posterior tendon.⁵^,⁶

FIGURE 4 Intraoperative photograph showing disruption of the tibialis posterior tendon insertion after excision of an accessory navicular. Reattachment with suture anchors is required.

Some authors have report arthrodesis of a large ossicle to the native navicular with screw fixation has the apparent advantage of avoiding disruption of the insertion of the tibialis posterior tendon. Although a 20% rate of nonunion was reported in one study, overall patient satisfaction was high.⁷^,⁸ Studies with large numbers of patients and lengthy follow-up are necessary to determine the role of fusion in the treatment of an accessory navicular.

Surgical treatment of associated flatfoot deformity and Achilles contracture at the time of accessory navicular excision remains controversial. Authors have reported concomitant subtalar arthroereisis,⁹ calcaneo-cuboid-cuneiform osteotomies,¹⁰ and medial displacement calcaneal osteotomies¹¹ at the time of symptomatic accessory navicular treatment. It is unclear whether these additional procedures result in better long-term outcomes than simple excision.

Tarsal Coalition

Tarsal coalition is an abnormal connection between the bones of the hindfoot or midfoot and is caused by failure of mesenchymal segmentation. A coalition can be fibrous, cartilaginous, or bony, and it can occur in isolation or as a component of a genetic syndrome. Progression from fibrous to cartilaginous and ultimately to bony tissue occurs during skeletal maturation, coinciding with a gradual onset of symptoms. This process explains why a symptomatic coalition is rare in young children. An association between rigid pes planus and tarsal coalition has been described, commonly referred to as peroneal spastic flatfoot. Calcaneonavicular and talocalcaneal coalitions, especially of the middle facet, are most common. Coalitions between other tarsal bones occur less often. Fifty percent of coalitions are bilateral. Multiple coalitions are rare, but it is essential to consider this possibility before undertaking surgical treatment.¹² The true prevalence of tarsal coalition is unknown because many coalitions are asymptomatic.

Clinical Findings

A tarsal coalition usually is discovered in a juvenile or adolescent patient, often after an acute ankle sprain or another minor trauma caused by impaired subtalar mobility. Patients report lateral hindfoot pain and tenderness in the sinus tarsi and often have peroneal muscle spasms secondary to pain. Hindfoot motion usually is limited, especially in patients with a complete bony coalition. Pes planovalgus deformity is typical and often is associated with an Achilles tendon or gastrocnemius muscle contracture. On single-limb heel rise test, the foot has poor restoration of the medial longitudinal arch and persistence of hindfoot eversion. Other causes of peroneal spastic flatfoot should be considered, however, including an osteochondral lesion of the talus, inflammatory arthritis, infection, fracture, and tumor.

Radiographic Evaluation

The initial radiographic evaluation includes the weight-bearing AP, lateral, and 45° internal oblique views of the foot as well as an axial (Harris) view of the hindfoot. Talar beaking (a dorsal osteophyte) at the talonavicular joint often is seen in a talocalcaneal or calcaneonavicular coalition and is not typically associated with true talonavicular arthritis. A calcaneonavicular coalition is best seen on a 45° internal oblique radiograph. A lateral radiograph may reveal prominence of the anterior process of the calcaneus toward the navicular (the so-called anteater’s nose sign; Figure 5). A talocalcaneal coalition is best seen on the axial view as an irregularity and an oblique orientation of the middle subtalar facet. A talocalcaneal coalition is less consistently seen on the lateral view, usually because the valgus obliquity of the subtalar joint causes it to be poorly defined.

FIGURE 5 Lateral radiograph showing a calcaneonavicular coalition and an anteater’s nose sign.

FIGURE 6 Coronal CT showing a normal foot (A) and a foot with a middle facet coalition and arthrosis (B).

The difficulty of diagnosing a tarsal coalition using plain radiographs, especially a talocalcaneal coalition, has resulted in the increased use of CT and MRI. CT can be used to identify the coalition, determine its extent, differentiate a bony from a fibrous coalition, and identify degenerative changes or additional coalitions in other parts of the foot (Figure 6). CT also is useful for evaluating the foot for other structural abnormalities that are difficult to see on plain radiographs such as an accessory anterior facet or a calcaneofibular impingement, which often accompanies a talocalcaneal coalition.¹³ MRI is the preferred modality for evaluating young patients, who are more likely to have a fibrous coalition because ossification is incomplete.¹⁴^,¹⁵

Nonsurgical Treatment

Initial nonsurgical treatment is recommended for all patients with a tarsal coalition. The modalities include rest, activity modification, and a period of immobilization in a cast, boot, or brace. After the symptoms subside, the patient can progress to using a custom orthosis and slowly resume activities. A stretching program for the Achilles tendon and gastrocnemius should be considered for patients with a contracture. Subsequent treatment may include the use of an orthosis to control hindfoot eversion.

Surgical Treatment

Calcaneonavicular coalitions are excised through a longitudinal Ollier incision over the sinus tarsi. The adequacy of the excision is assessed both clinically and radiographically; full hindfoot motion should be obtained intraoperatively. An associated gastrocnemius-soleus complex contracture should be treated at the time of surgical resection. Care must be taken not to injure the talonavicular joint or the talar head. In an effort to prevent recurrence, it is recommended to interpose soft tissue into the coalition site. The extensor digitorum brevis muscle belly and fascia can be advanced and interposed into the excision site. The use of fat graft is effective and may avoid skin cosmesis issues or inadequate coverage of the resection site associated with extensor digitorum brevis interposition.¹⁶ However, long-term results are modest, as in one series of 10 patients with mean follow-up of 11 years, 25% of patients were found to require further surgical intervention, American Orthopaedic Foot and Ankle Society (AOFAS) outcome scores were only fair, and pain, walking distance, and range of motion outcomes also were only fair.¹⁷

Surgical procedures for treating talocalcaneal coalitions include arthrodesis, coalition resection, and osteotomy without resection. The long-held criteria for determining whether a coalition should be resected include size of less than 30% to 50% of the posterior facet, hindfoot valgus of 16° to 21°, and little or no narrowing or degeneration of the posterior facet of the subtalar joint.¹⁸^,¹⁹ The site of pain and the severity of the valgus deformity may be at least as important as the size of the coalition, however. Calcaneal lengthening osteotomy is preferred over arthrodesis for a painful talocalcaneal coalition and advanced hindfoot valgus.²⁰

Talocalcaneal coalitions are excised through a medial approach between the flexor digitorum longus and flexor hallucis longus tendons. Care must be taken to avoid the medial neurovascular bundle. It is crucial that the coalition be adequately resected, particularly from anterior to posterior. Careful inspection of the anterior and posterior subtalar facets is necessary after removal
of the coalition. Most surgeons prefer to interpose bone wax and local fat in the resected coalition site, although other interpositional materials, including flexor hallucis tendon,²¹ de-epithelialized skin,²² and silicone sheets,²³ also have been used. Fat graft can be obtained from the buttocks or locally anterior to the Achilles tendon. A recent study of a large number of patients treated with resection and fat interposition reported good deformity correction and high AOFAS ankle and hindfoot scale scores.²⁴ Most experts recommend single-stage coalition resection and flatfoot reconstruction rather than arthrodesis as an initial treatment of moderate to severe coalitions.²⁰^,²⁵ Correction of calcaneofibular impingement is another potential advantage of deformity correction and calcaneal lengthening. Calcaneofibular impingement often is present in patients with a talocalcaneal coalition, and further investigation is needed to determine the relationship between impingement and symptoms. Arthroscopic resection of talocalcaneal coalitions has been described, but further evaluation of its safety and efficacy is needed, compared with well-established open techniques.²⁶^,²⁷

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