Orthopedic Teaching Cases 2023, Jan, 18 | 12:00 am

Pediatric orthopedic cases 34

CASE                               34                               

 

You see a 14-year-old girl in your clinic for the first time who has a chief complaint of right medial ankle pain. While doing physical therapy for a contralateral ankle injury, her right ankle was noted to have decreased inversion. Upon further questioning you find that the patient has also noted pain on the medial aspect of the ankle that is described as vague and deep in the ankle joint. The pain has caused her to adjust her gait during activities. There is no history of antecedent trauma or sprains. She denies constitutional symptoms. There is no family history of foot abnormalities.

On examination, there is decreased subtalar motion on the right side when compared to the left. She is tender to palpation on the medial aspect of her hindfoot slightly distal to the tip of the medial malleolus. There is a negative anterior drawer test. There is no tenderness to palpation over the sinus tarsi, midfoot, and forefoot. There is no ankle effusion. Her hindfoot rests in slight valgus, which corrects when the foot is plantarflexed, although subtly less on the right side than the left side.

What is the most likely cause of her medial ankle pain?

  1. Accessory navicular

  2. Talocalcaneal coalition

  3. Calcaneonavicular coalition

  4. Talar dome osteochondral defect (OCD)

  5. Osteomyelitis

  6. Tumor

 

Discussion

The correct answer is (B). The patient presents with vague symptoms, which makes pinpointing a definitive diagnosis challenging. However, there are important features of her history and physical examination that are most consistent with a talocalcaneal coalition.

A talocalcaneal coalition is a fibrous, cartilaginous, or bony connection between the talus and calcaneus. It forms as a result of failure of segmentation of primitive mesenchymal tissue and has an incidence of 1%. Patients with talocalcaneal coalitions commonly describe a vague, deep discomfort on the medial aspect of the ankle. Symptoms are most prevalent between 12 and 16 years of age, which coincides with increasing ossification of a cartilaginous or fibrous coalition. Clinical symptoms also frequently follow ankle sprains. On physical examination, there may be a lump under the tip of the medial malleolus. This is in contrast to patients with calcaneonavicular coalitions who present with lateral sided ankle pain and tenderness to palpation over the sinus tarsi between the ages of 8 and 12 years. While your patient does not have a rigid flatfoot, she does have limited subtalar motion, which is common with talocalcaneal coalitions and can lead to a severe valgus hindfoot with time.

The other diagnosis options are unlikely but should be considered. An accessory navicular commonly presents with tenderness over the medial midfoot, and a medial sided talar dome OCD often manifests with recurrent ankle effusions, both of which were not discovered on physical examination. Osteomyelitis and tumor should be included in the differential diagnosis; however, they are less likely than a tarsal coalition given the lack of constitutional symptoms. Additional imaging should be obtained to pinpoint a definitive diagnosis.

You discuss the aforementioned diagnosis with the patient and her family. They ask you how you will definitively diagnose the condition.

Your next step is:

  1. No further work-up is needed

  2. Obtain radiographs (3-views) of the foot and ankle

  3. Order a bone scan of the foot and ankle

  4. Obtain radiographs (3-views) AND a CT scan and MRI of the foot and ankle

 

Discussion

The correct answer is (B). Diagnosis of a tarsal coalition starts with obtaining plain radiographs of the foot and ankle. The most helpful radiographs are the internal oblique and weight-bearing lateral views. On the internal oblique view, a calcaneonavicular coalition is best visualized (Fig. 10–54). On the lateral radiograph there are numerous secondary signs that are associated with talar coalitions. A few notable ones include the “anteater nose,” the “C” sign, and talar beaking. The “anteater nose” is formed by the extension of the anterior process of the calcaneus past the calcaneocuboid joint in calcaneonavicular coalitions. It has been reported to be present in 100% of patients with this type of coalition. The “C” sign is formed by a posterior continuity of the talus and sustentaculum tali as a result of coalition of the middle and posterior facets of the subtalar joint. As the most common talocalcaneal coalition involves the middle facets of the subtalar joint, the “C” sign may be posteriorly disrupted if the posterior facet is not involved, and therefore, the sign has low specificity. Another sign of a talocalcaneal coalition is talar beaking, which forms as a result of increased stress at the talonavicular joint and traction from the talonavicular ligament. Talar beaking does not represent degenerative changes and does not predict degenerative changes of the joint. It can also be associated with other conditions that cause decreased subtalar motion, such as trauma, rheumatoid arthritis, acromegaly, and hypermobile flatfeet.

 

 

 

Figure 10–54 Primary and secondary radiographic findings of tarsal coalitions on the lateral projection (Reproduced with permission from Newman JS, Newberg AH. Congenital Tarsal Coalition: Mutimodal Evaluation with Emphasis on CT and MR Imaging. Radio Graphics 2000;20:321–332.).

 

Calcaneonavicular coalitions are nearly all diagnosed reliably with plain radiographs. However, talocalcaneal coalitions can be easily missed on

conventional radiographs, as the subtalar joint is incompletely visualized. The most definitive method to diagnose a talocalcaneal coalition is with advanced imaging, including CT and MRI scans. The CT scan allows for assessment of bony bridging while the MRI is more accurate for diagnosing, partial osseous coalitions, and fibrous or cartilaginous coalitions. Advanced imaging may also detect other asymptomatic coalitions, such as the uncommon talonavicular and calcaneocuboid coalitions. Radionuclide scanning of the foot with 99m-technetium can also be used to assess for talar coalitions if radiographs are unremarkable; however, bone scans lack anatomic detail and are nonspecific. Therefore, the next best step in management of your patient is to obtain radiographs (3-views) and a CT scan and MRI of the foot and ankle (D).

You order and review the foot radiographs with the patient and her parents in clinic (Fig. 10–55).

 

 

 

Figure 10–55 Anteroposterior and lateral radiographs of your patient.

 

As the radiographs demonstrate an equivocal C-sign and subchondral sclerosis of the subtalar joint, you suggest that the patient has a subtalar coalition and explain the importance of also obtaining CT and MRI scans.

Before her next follow-up appointment, you also recommend:

  1. Nothing additional

  2. Manipulation

  3. Physical therapy

  4. Nonsteroidal inflammatory medications, immobilization, and physical therapy

  5. Subtalar corticosteroid injection

 

Discussion

The correct answer is (D). Nonoperative care is the first line of treatment for symptomatic tarsal coalitions. This involves the use of nonsteroidal anti-inflammatory medications, immobilization, and physical therapy of the ankle with a

CAM boot or short leg cast. Anti-inflammatory medications are used to decrease pain acutely, while immobilization prevents subtalar motion and progressive deterioration of the subtalar cartilage. Other nonoperative options for the supple foot include orthotics, heel wedges, and arch supports. Despite a myriad of nonoperative options, success of conservative treatment for patients with talocalcaneal coalitions is guarded with a reported range between 0% and 46%. Calcaneonavicular coalitions are less likely to respond to conservative treatment. Patients and families should be made aware of the unpredictable success with nonoperative treatment for talocalcaneal coalitions.

You see the patient and her family back for follow-up 6 weeks later. Both the CT (Fig. 10–56) and MRI (Fig. 10–57) scans were completed and they confirm an incomplete talocalcaneal coalition that involves <50% of the subtalar joint surface There are no degenerative changes of the subtalar or talonavicular joints noted on MRI. The patient reports persistent pain despite compliance with her immobilization.

 

 

 

Figure 10–56 Lateral (left) and coronal (middle ) CT scan images and a 3D-reconstruction (right) of the ankle of your patient.

 

 

Figure 10–57 Sagittal (left) and coronal (right) MR images (T1: upper row; T2: bottom row) of the ankle of your patient.

 

What is the next step in management?

  1. Continued immobilization

  2. Subtalar corticosteroid injection

  3. Talocalcaneal resection

  4. Subtalar arthrodesis

 

Discussion

The correct answer is (A). The patient has persistent pain despite a course of NSAIDs and immobilization. Surgical intervention is a consideration; however, a second course of immobilization is often recommended before proceeding with surgical care. If the patient’s pain persists despite a second round of immobilization, she would be a good candidate for a talocalcaneal resection, as she would have failed nonoperative management, the coalition involves <50% of the subtalar joint surface, the foot has good overall alignment (heel valgus angle <16 degrees), and she has no subtalar or talonavicular arthritis. The success rates of operative treatment for calcaneonavicular and talocalcaneal coalitions vary. The success rate after calcaneonavicular coalition resection via a lateral approach and placement of interposing extensor digitorum brevis muscle ranges from 73% to 90%. For talocalcaneal coalitions, surgical resection from a medial approach and placement of interposing fat has a reported success of 33% to 80%. Best outcomes are seen in

younger patients (i.e., <16 years), when the coalition involves <50% of the subtalar joint surface, and if degenerative changes are absent. A subtalar arthrodesis is indicated if a coalition and/or pain recurs after resection if the talocalcaneal coalition involves >50% of the subtalar joint, and if there are degenerative changes of the talonavicular and/or subtalar joints.

 

Objectives: Did you learn...?

 

The common distinguishing clinical features between the two most common tarsal coalitions (calcaneonavicular and talocalcaneal)?

 

 

The appropriate imaging evaluation of a patient with a suspected tarsal coalition? The necessary nonoperative management of tarsal coalitions?

 

The unique surgical indications for tarsal coalitions?