Indian Journal of Dental Research

: 2019  |  Volume : 30  |  Issue : 4  |  Page : 634--638

Traumatic myositis chondro-ossificans of masseter muscle associated with TGF-β1, Indian Hegdehog, BMP2, osteopontin and osteocalcin upregulation: Case report

Allan Fernando Giovanini1, Katheleen Miranda2, Aline Fernanda Costa Vaz3, Rafael Correia Cavalcante4, Paola Fernanda Cotait de Lucas Corso5, Leandro Eduardo Klüppel6, Rafaela Scariot7,  
1 Professor of School of Health Science, Department of Dentistry, Positivo University, Curitiba, Brazil
2 Masters Student at School of Health Science, Department of Dentistry, Positivo University, Curitiba, Brazil
3 Oral and Maxillofacial Resident at Positivo University, Curitiba, Brazil
4 Oral and Maxillofacial Resident at Federal University of Parana, Curitiba, Brazil
5 PhD Student at School of Health Science, Department of Dentistry, Positivo University, Curitiba, Brazil
6 Professor of School of Health Science, Department of Anatomy, Federal University of Parana, Curitiba, Brazil
7 Professor of School of Health Science, Department of Dentistry, Positivo University; Professor of School of Health Science, Department of Stomatology, Federal University of Parana, Curitiba, Brazil

Correspondence Address:
Prof. Rafaela Scariot
Department of Oral and Maxillo-Facial Surgery, Positivo University, Professor Pedro Viriato Parigot de Souza Street, 5300, Curitiba - 81280-330


Masseter traumatic myositis chondro-ossificans (TMCO) is a rare pathological condition that causes severe mandibular function restriction. The aim of the present study is to report a TMCO case after direct masseter muscle injury and correlate it to bone and cartilage biomarkers up-regulation. Caucasian male patient, 38 years old, seeks treatment nine days after trauma with severe mouth opening limitation. Physical examination revealed a circumscribed hardened area connected to masseter muscle on the left side. Cone beam tomography and ultrasonography of masseter region were requested. There was incomplete fracture between the posterior board of inferior jaw and coronoid process as well as calcification within masseter muscle. The proposed treatment was excisional biopsy of calcification, coronoid process removal to enhance mouth opening as well as incomplete condyle fracture monitoring. Material removed was sent for histological analysis in order to confirm diagnosis. Immuhistochemistry was conducted and it was found that chondro-ossification biomarkers such as TGF-b1, Indian Hegdehog (IHH), BMP2, osteopontin (OP) and osteocalcin (OC) were up-regulated. One-year follow-up showed that the patient is stable with increased mouth opening and satisfactory jaw movements. Pathologists and maxillofacial surgeons must be aware of differential diagnosis of TMCO. Understanding cellular mechanisms of muscle tissue after trauma is also important once cellular pathway modifications leads to clinical features that differ from previously described in literature.

How to cite this article:
Giovanini AF, Miranda K, Costa Vaz AF, Cavalcante RC, Corso PF, Klüppel LE, Scariot R. Traumatic myositis chondro-ossificans of masseter muscle associated with TGF-β1, Indian Hegdehog, BMP2, osteopontin and osteocalcin upregulation: Case report.Indian J Dent Res 2019;30:634-638

How to cite this URL:
Giovanini AF, Miranda K, Costa Vaz AF, Cavalcante RC, Corso PF, Klüppel LE, Scariot R. Traumatic myositis chondro-ossificans of masseter muscle associated with TGF-β1, Indian Hegdehog, BMP2, osteopontin and osteocalcin upregulation: Case report. Indian J Dent Res [serial online] 2019 [cited 2020 Aug 5 ];30:634-638
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Full Text


Traumatic myositis ossificans (TMO) constitutes a non-neoplastic injury characterised by fibrous tissue proliferation and bone formation. It is a rare condition characterised by a heterotropic ossification (HO) within large muscles. TMO is described to occur combined with trauma and inflammatory process. Literature suggests approximately 30 TMO cases in head and neck with male predilection and no predilection for age. HO can result in pain and dysfunction, making rehabilitation difficult as well as revision surgeries.[1]

Its most common clinical presentation, especially when masticatory muscles are involved, is lockjaw.[1] The real challenge for surgeons is differential diagnosis between TMO and other conditions that can result in mouth opening limitation. Conditions as joint ankylosis, anterior disc displacement without reduction, foreign body reaction, coronoid process enlargement, or neoplasms are reasonable diagnostic hypotheses.[2] Thus, evaluation of trauma etiology as well as histology involved is vital for an accurate and correct TMO diagnostic. Microscopically, it shows a central area with fibroblast proliferation, an intermediate area composed of osteoid matrix and cartilage, and a peripheral zone with mature lamellar bone and active osteoclasts.[3]

Although several different treatment modalities have been proposed, many authors suggest interference only after ensuring that ossification has stopped as surgery performed during immature stage may worsen ossification. The most accepted treatment modality is complete excision of the ossified mass after its maturation. Most authors believe in mandatory intensive physiotherapy during postoperative care.[4]

Thus, the main purpose is to report a TMCO case after direct masseter muscle injury and correlate it to bone and cartilage biomarkers upregulation.

 Case Report

The patient is a 38-year-old male referred to the Oral and Maxillo-Facial emergency service reporting direct trauma in the face nine days before initial examination. Clinical investigation revealed mild edema of the posterior left jaw, severe mouth opening limitation (10 mm) [Figure 1], absence of lacerations and presence of a hardened and painful area. Palpation of left masseter muscle region evidenced stiffness and imaging showed incomplete fracture of condyle and coronoid process [Figure 2]. Ultrasonography showed a calcified mass in left masseter measuring 15 × 7 × 16 mm, approximately 8 mm of skin [Figure 2].{Figure 1}{Figure 2}

The proposed treatment plan was excisional biopsy of the hardened area under general anesthesia and conservative treatment of incomplete condyle fracture, since it did not show any signs of fragment displacement. Risdon access was performed with extensive dilatation for calcification and coronoid process removal [Figure 3]. An incision line was marked 2–3 cm below the lower mandible border, between the angle and the facial notch of the mandible. The incision was normally 4–5 cm, but was extended in either direction in cases of inadequate exposure. After skin incision, dissection was carried out down to the platysma muscle. The muscle was bisected using blunt scissors, and the cervical fascia was cut with care to not damage the facial nerve, until the masseter muscle was exposed. The masseter was cut just above the lower mandible border and dissection was carried out to the periosteum. The calcified mass was also dissected, being removed with a safety margin of approximately 1 cm of healthy muscle tissue to decrease the chances of relapse with the use of electrobisturi to improve hemostasis. Coronoid process removal and temporal muscle freeing were performed in order to expand mouth opening movements. At the end of surgical procedure, the patient had a 46-mm forced mouth opening.{Figure 3}

Material removed was sent to histological analysis confirming TMO diagnosis. The histological analysis showed chondroid and bone tissue with a large number of osteoblasts surrounded, presence of significant fibrous tissue as well as adipocytes and blood vessels and scarce inflammatory process in the central region [Figure 4]. Based on the histopathological frame, the established diagnosis was compatible with myositis chondro-ossificans of masseter. To better understand the pathogenesis of this peculiar pathological condition, immunohistochemical techniques were used which demonstrated the expression of TGF-β1, both in specific fibrotic area as well as in the area of mineralisation. In addition, the simultaneous presence to IHH, BMP2/4, OP and OC was demonstrated to be concentrated in the chondroid-like and bone tissues. Immunohistochemistry was also conducted and some biomarkers were found [Figure 5].{Figure 4}{Figure 5}

After 24 hours of the surgery, the patient received medical discharge and postoperative medication. Physiotherapy followed the whole treatment and the jaw function improved, with 25 mm of mouth opening after 30 days postoperative [Figure 6].{Figure 6}


Traditionally, myositis ossificans is classified into two groups: Progressive myositis ossificans and traumatic myositis ossificans. Traumatic myositis ossificans (TMO) is determined as a heterotrophic and non-neoplastic proliferation of bone inside a muscle or other soft tissues previously exposed to a trauma. It is a localised and self-limiting injury.[1] Pathogenesis is not fully explained, but has trauma as the main etiological factor. This study reports a case of traumatic myositis chondro-ossificans (TMCO) due to the fact that histologic evaluation showed ectopic formation of bone as well as cartilage in masseter muscle after trauma.

Panoramic radiography and computed tomography are useful imaging tests for diagnosis and surgical planning, being able to pinpoint the exact location of the injury and its relation with surrounding tissues.[2]

TMO can be one of the causes of temporomandibular joint ankylosis as well as diseases that has mouth opening limitation as the main characteristic, such as anterior disc displacement without reduction, enlargement of the coronoid process and foreign body reaction. It may also be a differential diagnosis of malignant diseases, such as osteosarcoma.[2] In TMO, pain tends to decrease with time, and calcification starts at periphery and progresses toward the centre; in contrast, osteosarcoma pain tends to increase and progression starts in the centre and goes to the periphery.[3]

Histologically, the characteristic feature of TMO is the peripheral ossification and a central zone of cell proliferation. The mesenchymal cells have high mitotic activity and can be easily mistaken for malignant lesions. With maturation of the injury, there is the development of distinct zones: The presence of osteoblasts, immature bone formation, and islands of cartilage tissue due to endochondral ossification characterize the intermediate zone. The peripheral zone comprises active osteoclasts and mature bone, separated from the surrounding tissue by fibrous tissue.[3] Deregulation of inflammatory and wound healing factors could signal mesenchymal progenitor cells (MPCs) or other nearby cells to initiate ectopic bone and cartilage formation. In addition, the formation of fibrotic lesions in regenerating muscle tissues provides a hypoxic, osteoinductive environment that could encourage the cells to undergo endochondral ossification.[5] It is already known that cytokine expression after trauma is not well described; however, some of them are described in literature. Our goal in conducting immunohistochemistry of the lesion was to find the biomarkers related to chondro-ossification, angiogenesis and inflammation within the post-traumatic muscle.

TGF-β1 is the most significantly upregulated gene in traumatised muscle documented in literature. It was identified within traumatised muscle fibres after injury. TGF-β1 has also been reported to induce endothelial cells to undergo differentiation into mesenchymal cells as well as was described to potentiate MPCs to initiate chemotaxis and osteoblasts differentiation. According to that, TGF-β1 ratio is a reliable predictor for identifying susceptible to fibrosis and osteoinductive fibroproliferative lesions, such as myositis ossificans.[5]

Bone morphogenetic proteins are well studied members of TGF-β superfamily that plays important roles in cartilage and bone development by stimulating mesenchymal cells intracellular events. As it was said, it is also involved in the hedgehog pathway, TGF-β1 signalling pathway as well as in cytokine-cytokine receptor interaction.[6] Data suggests that overexpression of BMP-2/4 in combination with or without IHH results in increased deposition of mineralised extracellular matrix, osteogenic marker genes. BMP-2 in conjunction with IHH appears to have a synergistic effect on ontogenesis, promoting expression of osteogenic markers osteopontin and osteocalcin.[7]

CD34 is a widely used cell surface marker for stem cell isolation and detection with robust regenerative potential for therapeutic purposes. It is a transmembrane glycoprotein rich with O- and N-glycans. Its function depends on cell ligand, which is modulated by growth factors such as TGF-B1 and oxygen concentrations. Human peripheral blood cell culture suggests that CD34 induces destabilisation of endothelial cells barrier that may accompany sprout as well as tube formation. Silencing CD34 results in strengthening of cell-cell contact and increased barrier function of endothelial cells.[8],[9]

Once oxygen levels raises through enhanced barrier destabilisation and tube formation, a perfect environment is then created to endochondral ossification. Bone formation is figured by osteopontin (OPN) and osteocalcin (OCN) which were identified in immunohistochemistry. Osteopontin (OPN) is a highly phosphorylated sialoprotein that is a prominent component of mineralised extracellular matrices of bones and teeth produced by many different epithelial cell types.[7] OPN is characterised by a polyaspartic acid sequence presence and the Ser/Thr phosphorylation sites that mediate hydroxyapatite binding. OCN is secreted solely by osteoblasts and were thought to play a role in the body's metabolic regulation and is pro-osteoblastic, or bone-building, by nature. It is also implicated in bone mineralisation and calcium ion homeostasis. As OCN is produced by osteoblasts, it is often used, together with OPN, as markers for bone formation process.[6],[7]

Knowing the cellular nature of the lesion, we established the treatment modality: Complete excision of ossified mass after maturation, which corroborates with literature. Many authors suggest intervening only after ensuring that ossification has stopped as surgery during the immature stage may worsen ossification.[4],[9] However, alternative treatments have been proposed. Some authors discuss conservative treatment using medications such as NSAIDs, bisphosphonates, magnesium and warfarin, and/or the use of low-power radiation.

Intensive physiotherapy should be a mandatory part of postoperative care.[4] Jayade et al., suggested that surgical excision of the calcified mass, associated with vigorous postoperative physiotherapy, shows good results in the recovery of oral function and decreases significant rates of disease recurrence.[10]

Pathologists and maxillofacial surgeons should be aware of differential diagnosis of TMCO. Understanding the cellular mechanisms of muscle tissue after trauma is also important as modifications of cellular pathways may lead to clinical features that differ from those previously described in the literature.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.


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