A young female presented with gradual onset pain in both feet and ankles and multiple episodes of ankle sprain in past.
A 10 year old female patient presents with 2 month history of gradual onset and worsening pain in both feet. She has had multiple episodes of ankle sprain in past few months. Pain in both feet is worst with activity and relieved with rest. On examination there is tenderness on anterolateral aspect of both feet. Plain radiograph AP, lateral, medial oblique view and CT scan were performed of both ankles.
Calcaneonavicular coalition (also known as calcaneonavicular bar) is a connection between Calcaneum and navicular bone. This bridge may be bony, cartilaginous, fibrous or a combination of these. The overall incidence of tarsal coalition in general population is unknown, most studies report it to be less than 1% though a study in Australia on cadaveric feet report the incidence to be 8.8% (5). Of all the tarsal coalitions, calcaneonavicular coalition was found to be the most common, followed by talocalcaneal coalitions. The exact incidence of bilateral tarsal coalition was not found in the literature though a study in New York, USA reported the true incidence of multiple coalition around 0.03% (4). Etiology is unclear but appears to be as a result of the failure of differentiation and segmentation of the foetal mesenchyme. Presentation is usually at 8-12 years of age. Most patients present at the time when the coalition begins to ossify. Clinical symptoms of the tarsal coalition frequently follow a sequence of sprains or other minor injuries to the involved foot. The pain is gradual onset and worst after continued activities. Physical examination usually reveals tenderness at the anterolateral aspect of the foot. Pes planus and heel valgus may be present. Calcaneonavicular coalition is best visualized in Medial Oblique view ( ie foot obliqued approximately 45 degrees relative to the x-ray film). In this view the osseous coalition presents as continuity of the superomedial aspect of the anterior calcaneal beak and inferolateral aspect of the navicular as one bony structure. In the more frequently encountered fibrous/cartilaginous coalition the two bones appear to articulate with one another. Lateral radiograph demonstrates the ‘Anteater’ sign. There is elongation and enlargement of the anterior calcaneal process superiorly and has a blunt tip like anteater’s snout. CT and MRI are now recommended for confirmation of tarsal coalition. Treatment initially is symptomatic and consists of pain relief, shoe modification and change in activity. Surgical resection of coalition is undertaken on failure of conservative treatment.
Bilateral Calcaneonavicular Coalition
Based on the provided bilateral foot X-rays in the anteroposterior and oblique views, as well as CT scans, the following primary characteristics can be observed:
1. An abnormal bony or bone-like connection is visible at the anteromedial dorsal aspect of the foot (between the calcaneus and the navicular), appearing as a “strip” or “bridge.”
2. The oblique X-ray indicates a tightly positioned, continuous-contour abnormal structure between the anterior calcaneal process and the proximal navicular.
3. The lateral X-ray view shows an elongated anterior calcaneal process resembling the “mouth and nose of an anteater,” also referred to as the “Anteater Sign.”
4. CT imaging clearly demonstrates a bony or partially fibrous/cartilaginous union between the calcaneus and the navicular, with reduced or absent joint space and mild surrounding soft tissue swelling.
5. There is no obvious acute fracture sign in the overall bone structure; most other foot joint spaces are acceptable, with no prominent bone destruction or focal bony overgrowth observed.
Considering the patient’s age (10 years old), clinical symptoms (bilateral foot and ankle pain, recurrent sprains), and the radiological findings, the following differential diagnoses are considered:
1. Calcaneonavicular Coalition:
• Common in children or adolescents, often due to congenital developmental abnormality leading to partial or complete fusion (bony, fibrous, or cartilaginous) between the calcaneus and the navicular.
• Radiological characteristics typically include an abnormal connection between the anterior process of the calcaneus and the navicular, and the “Anteater Sign” seen on oblique and lateral views.
2. Subtalar (Calcaneotalar) Coalition:
• Another type of tarsal coalition, more often involving fusion between the calcaneus and the talus rather than the navicular, but can also present clinically with recurrent ankle sprains and foot pain.
• Patients may exhibit flatfoot and valgus deformity. However, the radiological features typically affect the calcaneotalar joint, which differs somewhat from this case.
3. Other Congenital or Developmental Foot Anomalies (e.g., accessory navicular, metatarsal anomalies):
• Can also present with foot pain and functional limitations. However, their radiographic appearances generally differ significantly from a true calcaneonavicular coalition.
Considering the patient’s age, bilateral ankle pain with recurrent sprain history, the characteristic radiological findings (especially the abnormal connection between the anterior calcaneal process and the navicular and the “Anteater Sign” on oblique views), and CT confirmation of local joint fusion, the most likely diagnosis is Calcaneonavicular Coalition.
1. Conservative Treatment:
• Pain Management: Nonsteroidal anti-inflammatory drugs (NSAIDs) or other analgesics may be used to relieve joint pain and inflammation.
• Foot Support or Orthotic Insoles: Use of arch supports or ankle braces can help reduce foot pressure and discomfort.
• Activity Modification: Avoid excessive running or high-impact activities, and follow medical advice to minimize heavy loading on the feet.
2. Surgical Treatment:
• If severe pain and functional impairment persist after conservative management, surgical resection of the coalition or joint fusion (depending on the extent and type of coalition) may be considered.
• Postoperative care typically requires a period of immobilization or partial weight-bearing rehabilitation exercises.
3. Rehabilitation and Exercise Prescription (FITT-VP Principle):
• Frequency: Recommend low-impact rehabilitation exercises 3–5 times per week, such as swimming or cycling.
• Intensity: Begin with light to moderate exercises, for example, 10–15 minutes of low-intensity ankle flexibility training, avoiding prolonged standing or sudden directional changes. Increase load gradually based on pain tolerance.
• Time: Start with sessions of 10–15 minutes and gradually increase to about 30 minutes depending on tolerance.
• Type: Emphasize low-impact aerobic activities (e.g., swimming, using an elliptical machine) combined with exercises to strengthen and stabilize the ankle and foot muscles (e.g., resistance band eversion/inversion drills, foot arch strengthening).
• Volume: Aim for a weekly total of 60–150 minutes of low-intensity exercises combined with joint function training, continued for 8–12 weeks to observe results.
• Progression: If pain and joint stability improve, gradually increase weight-bearing and exercise volume, such as light jogging or mild jumps. Progress slowly, adding 5 minutes per session every 2–3 weeks, while monitoring pain and swelling.
4. Precautions:
• If significant worsening of pain or new injury symptoms occur, seek medical attention promptly to determine whether activities should be further limited or the treatment plan adjusted.
• Because children’s bones are still developing, it is crucial to avoid excessive loads and inappropriate exercise methods to prevent long-term foot deformities or injuries.
This report is a preliminary analysis based on the available imaging and history and cannot replace an in-person consultation or a specialist’s professional diagnosis and treatment recommendations. The patient should follow up with additional examinations and treatment according to clinical findings and medical advice.
Bilateral Calcaneonavicular Coalition
