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Traumatic bone cyst of an anterior mandible with previous symphyseal fracture in a pediatric patient: a rare finding and etiopathologic correlationKumar Nilesh, MDS ¢ Aaditee V. Vande, BDS ¢ Shivsagar Tewary, MDS ¢ Suresh K.V., MDS

Traumatic bone cysts (TBCs) are uncommon intraosse-ous lesions, classified as pseudocysts because they lack an epithelial membrane lining. The etiology of a pseudo-cyst has not been determined. Various hypotheses have been put forward to explain its pathogenesis, of which the traumatic-hemorrhagic theory is the most commonly accepted. Minor trauma, insufficient to cause fracture or iatrogenic injury, is commonly implicated as the stimulus initiating cyst formation. A TBC presenting after jaw fracture has been rarely reported in the literature. This article presents a case of a TBC of the anterior mandible in a child with a previous history of trauma and fracture of the symphysis. The article also reviews the literature to corroborate the possible role of major trauma in the pathogenesis of TBC.

Received: July 23, 2016Accepted: September 9, 2016

Key words: bone cavity, mandible, simple bone cyst, traumatic bone cyst

Traumatic bone cysts (TBCs) are unusual lesions, char-acterized by bony walls enclosing an empty space or containing blood, serous fluid, or (rarely) connective

tissue. They were first reported by Lucas & Blum in 1929.1 Since then, various terms has been used to describe this lesion, includ-ing traumatic cyst, traumatic hemorrhagic cyst, progressive bone cavity, solitary bone cavity, solitary bone cyst, simple bone cyst, idiopathic bone cavity, hemorrhagic bone cyst, extravasa-tion cyst, hemorrhagic cyst, unicameral bone cyst, hemorrhagic extravasation, and solitary hemorrhagic cyst.

The World Health Organization classified the TBC as a non-neoplastic osseous pathology and included it along with other lesions, such as aneurysmal bone cyst, fibrous dysplasia, ossify-ing fibroma, osseous dysplasia, central giant cell granuloma, and cherubism.2 The etiology of TBCs is still unclear. Trauma is one of the factors implicated in pathogenesis of TBC.1 The trau-matic-hemorrhagic theory suggests that when minor trauma (accidental or iatrogenic) causes intramedullary hemorrhage, the clot formed may not undergo resolution. The clot liquefies, leading to formation of an empty or fluid-filled cavity without an epithelial lining.

TBCs are commonly found in the metaphyses of long bones. Involvement of the jawbone is rare and presents as an asymp-tomatic lesion that usually is diagnosed incidentally during routine radiographic examination. The lesion predominantly involves the posterior mandible, located between the inferior alveolar canal and root apices of the mandibular premolar and molar teeth.3 This case report describes a TBC of the anterior mandible in a boy with a history of trauma and symphyseal fracture. A literature review of the association between TBC and major trauma or jaw fracture is also presented.

Case reportA 12-year-old boy was referred to an oral surgery clinic for evaluation of an asymptomatic periapical lesion that was dis-covered incidentally during routine radiographic screening. The patient’s medical and dental histories were noncontribu-tory; however, he had a fall from a swing 3 years earlier, for which no active treatment was provided. On clinical examina-tion, no dental or mucosal abnormality was seen. The man-dibular anterior teeth were responsive to electric pulp testing. No swelling, cortical expansion, tooth mobility, or draining sinuses were noted.

A panoramic radiograph of the patient showed a well-defined, 3 × 1-cm unilocular radiolucency with scalloped, wavy margins that was located between the root apices of the anterior teeth and the lower border of the mandible. Discontinuity of the lower

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border of the mandible was noted at the midline, suggestive of previous symphyseal fracture (Fig 1). The lamina dura of the anterior teeth was intact.

The radiographic findings were suggestive of a benign intraos-seous lesion, with evidence of previous symphyseal fracture. A provisional diagnosis of TBC was made; differential diagnoses included central giant cell granuloma, aneurysmal bone cyst, and ameloblastoma.

Surgical exploration and biopsy of the lesion were planned and executed under local anesthesia. A vestibular incision was placed, and the mucoperiosteal flap was raised over the labial cortex. There was no expansion or thinning of the cortical bone. A bony window was created to access the lesion, which was empty and had no soft tissue lining. The intraoperative findings, along with the clinical and radiographic features, confirmed the diagnosis of TBC. The bone cavity was explored, and surround-ing bone was curetted to induce fresh bleeding. Primary closure was attained using resorbable suture (Fig 2).

DiscussionThe diagnostic criteria for a TBC include an intraosseous lesion without an epithelial lining, surrounded by bony walls. The lesion is either empty or contains liquid or connective tissue.

The fact that TBCs have been known by a variety of names over the years reflects the lack of understanding of the true etio-pathogenesis of the disease. Of the various theories proposed to explain the development of a TBC, the traumatic-hemorrhagic theory is most widely accepted.4 This theory states that when a hematoma from intramedullary hemorrhage subsequent to trauma fails to consolidate, it gives rise to a TBC.4 The hema-toma then liquefies and induces transudation of fluid into the cyst. This causes an increase in internal pressure, leading to venous stasis, bone marrow necrosis, and osteoclastic resorp-tion, contributing to the formation and growth of the TBC.

One type of trauma implicated in the formation of TBCs is iatrogenic damage (such as tooth extraction, orthodontic trac-tion, or any external injury) that is insufficient to cause jaw fracture. A TBC arising in a patient subsequent to mandibular fracture rarely has been reported. A search of the English-language literature in the PubMed database—using the terms traumatic, solitary, idiopathic, cyst, mandible, and fracture—revealed 102 articles, of which only 4 cases were reported to be associated with mandibular fracture (Table).5-8 Fractures in 3 of the cases were secondary to trauma to a mandible weakened by a cystic lesion (pathologic fracture).5,7,8 In 1 case, multiple cysts were diagnosed in a patient with osteogenesis imperfecta who

Fig 2. Surgical exploration of the lesion. A. Armamentarium. B. Bone cavity. C. Closure of the surgical site.

Fig 1. Unilocular radiolucent lesion over the anterior mandible (light blue arrows) and discontinuity of the lower border in the symphyseal region (white arrows).

A B C

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had a previous history of condylar fracture.6 In the present case, the lesion was found in an anterior mandible with a history of trauma and radiographic evidence of previous symphyseal fracture. Despite earlier theories that only minor external injury initiates TBCs, these findings suggest that major trauma leading to jaw fracture can also trigger pathogenesis of the lesion.4,6-8 This further emphasizes the need to closely monitor pediatric patients with a history of mandibular fracture to rule out development of a TBC.

Although trauma is believed to be the single most important cause of TBCs, not all cases are associated with a history of trauma. Studies have reported a clear history of trauma in less than 29% of cases.7,9 This may be attributed to lack of careful medical history recording or the fact that minor trauma may not be remembered by the patient. The higher incidence of trauma in the anterior part of the mandible is also at odds with the higher incidence of TBCs in the posterior region of the mandible. Other hypotheses proposed to the explain pathogen-esis of TBCs include degeneration of bone tumors, disorders of calcium metabolism, various mild infections, local disorders of bone growth, venous obstruction, intensified osteolysis, degen-eration of a bone cyst, and ischemia with necrosis of the bone caused by primary vascular or neurogenic disorders.10,11

The majority of maxillofacial TBCs are located in the mandib-ular region between the apices of premolar or molar teeth and the inferior alveolar canal. Although uncommon, cases have also been reported in the symphysis, ramus, condyle, and maxilla.9 In a review of 21 cases of TBC, 16 (76%) were seen in the man-dibular region, 3 (14%) cases were located in the symphysis, and 2 (10%) were in the ramus.12 In a similar retrospective review of 26 patients with TBC, 8 (30%) were seen in the anterior man-dible, 1 (4%) in the ramus region, and 17 (66%) in the mandibu-lar body.4 The traumatic-hemorrhagic theory seems to be the explanation for the more common involvement of the mandible rather than the maxilla. The mandible, which has more cortical bone, repairs itself more slowly than the maxilla.

Although they may be detected at any age, TBCs are more commonly seen in the first 2 decades of life. The greater inci-dence of TBCs in young patients can be possibly explained by the higher likelihood of trauma in this age group, while the reduced prevalence in older patients suggests that this lesion may be self-repairing. There is no consensus on sex predilection, with some studies noting a male predominance while others report equal involvement or a female predisposition.13

The TBC usually presents as an asymptomatic lesion incidentally detected during a radiographic survey. In symp-tomatic cases, pain or tooth sensitivity is the most common presentation. Less frequently reported features include cortical expansion, paresthesia, and fracture.5,8 Radiographically, TBCs typically present as well-defined, unilocular radiolucencies with wavy borders. In its most common location, the radiolucency lies between the apices of mandibular posterior teeth and the inferior alveolar canal. The structure of the mandibular canal may or may not be preserved. The superior margin of the radiolucency is indented between the teeth, creating a scalloped appearance.14 There is no resorption or displacement of teeth. The cortical bone or lamina dura is usually not involved.

In the case described in this report, the lesion presented as a well-defined, unilocular, irregular radiolucency between the apices of the incisor teeth and the lower border of the anterior mandible. A disruption of the lower border at the symphyseal region, in combination with a history of trauma, was sugges-tive of previous symphyseal fracture. This could have been the trigger for the initiation of the TBC, supporting the traumatic-hemorrhagic theory.

Surgical exploration serves for both confirmation of the diagnosis and management of the TBC. Curettage induces fresh bleeding within the bone cavity, which consolidates and ultimately ossifies with complete healing. Specimens for histopathologic evaluation are either scanty or completely absent, limiting the role of pathologic evaluation for diagnosis. The clinical presentation, radiographic features, and intraop-erative finding of an empty bone cavity with fluid, blood, or scanty connective tissue are sufficient for diagnosis of TBCs. Some TBCs heal spontaneously without any intervention. Recurrence is extremely low.

ConclusionTraumatic bone cysts are mostly asymptomatic and are usually discovered during routine radiographic examination. They are predominantly seen in pediatric patients and commonly involve the posterior mandible with or without a history of minor trauma or iatrogenic injury. This article highlights a case of an anterior mandibular TBC in a child with previous symphyseal fracture, which suggests that major trauma causing jaw fracture may possibly initiate pathogenesis of this lesion. This find-ing highlights the importance of closely monitoring pediatric patients after trauma to rule out development of a TBC.

Table. Cases of traumatic bone cyst (TBC) associated with mandibular fracture.

Author (year) Age group Associated fracture

Matise et al (1987)5 Adult Pathologic fracture of the mandible

Jones & Baughman (1993)6 Adult Condylar fracture 5 years prior to diagnosis of multiple TBCs in a patient with osteogenesis imperfecta

Ahlers et al (2013)7 Child Pathologic fracture of the mandible

Chell et al (2015)8 Child Pathologic fracture of the mandible

Present case (2017) Child Symphyseal fracture 3 years prior to diagnosis of a TBC

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Author informationDr Nilesh is a reader, Department of Oral & Maxillofacial Surgery, School of Dental Sciences, Krishna Institute of Medical Sciences Deemed University, Karad, India, where Dr Vande is a postgraduate student and Dr Tewary is a reader, Department of Prosthodontics. Dr Suresh K.V. is a lecturer, Faculty of Dentistry, SEGi University, Kota Damansara, Malaysia.

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