Posterior tibial tendon impingement due to os subtibiale: a case report and up-to-date review

Evaluation and Management of Common Accessory Ossicles of the Foot and Ankle in Children and Adolescents

Accessory ossicles are a common radiographic finding about the foot and ankle in children and adolescents. They are often noted incidentally during evaluation of foot and ankle injuries, and most can be managed nonsurgically. Although over 20 accessory ossicles have been described around the foot and ankle, five specific structures generate the most concern in pediatric patients. An accessory navicular presents commonly with medial midfoot pain and may require surgical intervention after failure of nonsurgical treatment. Although an accessory navicular can be treated surgically with simple excision, there is some recent evidence that supports concomitant reconstruction of associated flatfoot deformities. Os trigonum, an ossicle posterior to the talus, is also commonly asymptomatic. However, os trigonum may be associated with persistent posterior ankle pain, and open and endoscopic resection techniques are successful. Os subfibulare is an uncommon ossicle that may be associated with recurrent ankle sprains. Recent literature reports successful return to activities after ossicle excision and ligament reconstruction. Os subtibiale may be confused with a medial malleolar fracture in skeletally immature patients. Os peroneum may contribute to lateral midfoot pain.

Symptomatic Os Subtibiale Following Injury: A Case Report of Failed Conservative Treatment, Leading to Differential Diagnosis Made Intraoperatively

Introduction:

Os subtibiale is a rare accessory bone found adjacent to the distal tibia and is mostly asymptomatic. Differentiating it from a medial malleolar fracture is challenging. Most cases of acute ankle trauma that presents with an Os subtibiale are initially diagnosed as fractures by treating physicians at emergency centers. It is therefore critical for an orthopedic surgeon who gets referral for such cases to consider complete history of such patients to understand the cause of their symptoms. The goal is to avoid unnecessary surgical treatment and to realize that a symptomatic Os subtibiale can be successfully managed by conservative means. Nonetheless, certain cases may require surgical treatment if conservative treatment options fail. This is a case report of a patient that was diagnosed as a case of symptomatic Os subtibiale intraoperatively, after conservative options were unsuccessful.

Case Presentation:

An 18-year-old patient with an injured right ankle was referred to our clinic after failed attempts to resolve his symptoms conservatively. Based on our initial clinical and radiographic examination, the patient was continued on a conservative treatment plan assuming, it was a case of unsuccessful fracture union. After almost a year of failed conservative treatments, surgery was offered to the patient, with the understanding that the bone fragment might either be fused or completely removed based on intraoperative diagnosis. At surgery, it was observed that the bone fragment had the characteristic of an Os subtibiale. It presented as a round, smooth structure with well-formed cortical boundaries, and minimal attachment to the distal tibia. A diagnosis of symptomatic Os subtibiale was made intraoperatively, which was then successfully excised using standard orthopedic instrumentation. The patient healed uneventfully and reported a pain free, normal ankle range of motion at latest follow-up of 18 months.

Conclusion:

Accurate diagnosis of Os subtibiale continues to present a learning challenge for most orthopedic physicians as these cases are extremely rare and often asymptomatic. Our patient failed to respond to conservative treatment, which led to surgery and intraoperative diagnosis of Os subtibiale that was the pain causing agent.

[Os subtibiale: That odd ankle pain]

Os subtibiale is a low prevalence accessory bone of the ankle. This bone is located in the posterior colliculus of the tibial medial malleolus, both in paediatric and adult ages. It can cause pain, redness and/or swelling, which can lead to a mistaken diagnosis of avulsion fracture. Adequate anatomical knowledge is crucial. First, we present the case of a school-aged boy, seen at the outpatient clinic for a 2-month history of pain in both inner ankles after an injury. Second, we present the case of an adult patient with a 3-day history of right medial ankle pain, with no previous injury, evaluated at the Emergency Department. Accurate history-taking and physical examination are essential. The diagnosis is given by conventional radiology of both ankles, in antero-posterior and lateral load views. The initial treatment is conservative (splint or orthesis) to establish and maintain the function of the foot during loading activities. If there is no recovery after 6 months, surgical treatment can be considered.