Journal of Indian Academy of Oral Medicine and Radiology

: 2019  |  Volume : 31  |  Issue : 3  |  Page : 280--283

Unilateral myositis ossificans traumatica of medial pterygoid muscle: Case report and review

Pinakapani Ramakrishna1, Biswajit Mishra2, Sanjay Jadwani2, Seema Dengra2,  
1 Department of Oral Medicine and Radiology, Government Dental College, Raipur, Chhattisgarh, India
2 Department of Oral and Maxillofaciall Surgery, Government Dental College, Raipur, Chhattisgarh, India

Correspondence Address:
Dr. Pinakapani Ramakrishna
Department of Oral Medicine and Radiology, Government Dental College, Raipur, Chhattisgarh


Myositis ossificans is a rare disease that is characterized by nonneoplastic, heterotopic bone formation within a muscle. It rarely involves the masticatory muscles. Since 2001 to 2015 only 20 cases involving the masticatory muscles have been reported. This case report is one such rare case of myositis ossificans traumatica involving left medial pterygoid muscle in a 37 year-old female patient. Surgical excision of the entire muscle was done and adequate mouth opening was achieved. One-year post surgery no signs of recurrence was observed and there was presence of adequate mouth opening. The article also reviews the literature of myositis ossificans of the masticatory muscles.

How to cite this article:
Ramakrishna P, Mishra B, Jadwani S, Dengra S. Unilateral myositis ossificans traumatica of medial pterygoid muscle: Case report and review.J Indian Acad Oral Med Radiol 2019;31:280-283

How to cite this URL:
Ramakrishna P, Mishra B, Jadwani S, Dengra S. Unilateral myositis ossificans traumatica of medial pterygoid muscle: Case report and review. J Indian Acad Oral Med Radiol [serial online] 2019 [cited 2021 May 14 ];31:280-283
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Myositis ossificans (MO) is a rare disease that is characterized by nonneoplastic, localized, self-limiting, heterotropic bone formation within a muscle.[1] It rarely, but can also involve tendons, layers, periosteum, and subcutaneous fat tissues.[2] The disease has four distinct clinical pathologies:[2]

MO Progressiva, also known as fibrodysplasia ossificans progressive. It is an autosomal dominant disease commonly seen among children and females, characterized by symmetric skeletal malformations of hands and feet such as microdattilia, syndattilia, poidattilia, and agenesis of one or more feet phalanx. A progressive heterotropic ossification of soft tissues is also present.MO traumatica (MOT) or circumscripta that is characterized by bone metaplasia in a muscle. The disease has been identified among patients with the history of trauma, in which the intramuscular haemorrhage causes bone metaplasia. Repeated microtrauma and/or inflammatory disease have also been attributed. Both lateral and medial pterygoid muscles are commonly involved. Masseter muscle involvement is rarely seen.Pseudomalignant MO often presenting as soft tissue mass with intermittent pain and localized erythema. The disease is most frequently localized around the pelvis, greater trochanter, femur, and knee. There is no history of trauma reported by the patients.MO associated with paraplegia. This variant indicates a primitive variant associated with atrophy and tissue degeneration. The prognosis of this variant is poor.

MO of masticatory muscles are still rare, thus according to Jiang Q et al. only 20 cases were reported from 2001 to 2015.[3] The aim of this article is to present a case of MOT of the left medial pterygoid muscle and to review the literature of MO of masticatory muscle.

 Case History

A 35-year-old female patient was referred from tertiary health care centre to Government Dental College, Raipur, Chhattisgarh with a complaint of restricted mouth opening in the last two years. Her history revealed the above complain associated few months following mandibular block anaesthesia that was administered for dental extraction procedure. She observed a gradual reduction in mouth opening associated with occasional exacerbation of pain in the same side of jaw. The patient had also experienced weakness when biting and chewing during these times. Despite multiple medications and exercises as told by her dentist, there was no improvement. In the last two months, she had observed inability to open mouth. She denied any medical history of interest except for weight loss over one year.

Physical examination revealed that the patient was moderately nourished, with no evidence of any developmental abnormalities. No facial asymmetry was apparent on the extraoral examination [Figure 1]. On palpation the masseter and temporalis muscles were normal. However, mild tenderness was elicited with the left medial pterygoid muscle. The lymph nodes (submandibular and deep cervical) were nonpalpable and non-tender. On intraoral examination, the patient presented with inability to open mouth [Figure 2]. Carious involvement of right maxillary central incisor and canine, and left maxillary third molar was examined. The right mandibular first, second, and third molars' residual roots were examined. Left and right mandibular second premolar; left first, second and third molars were missing. The patient's dental hygiene was reasonably good. Based on history and clinical examination, a provisional diagnosis of trismus secondary to left pterygomandibular space infection was made. Following were considered under differential diagnosis – musculoskeletal trauma, temporomandibular joint diseases like anterior disc displacement without reduction and ankylosis, and foreign body reaction.{Figure 1}{Figure 2}

The patient's general medical status was normal and laboratory tests such as complete blood count, serum calcium, and phosphorous levels were within normal limits. A panoramic radiograph revealed well-defined radiopaque calcified mass with apparent bony features extending from the left pterygoid process to postero-inferior aspect of ramus of mandible of the same side [Figure 3]. Axial, coronal, and three-dimensional computed tomography scans confirmed the presence of a uniform, well-defined heterotopic calcification with well-defined cortical limits involving the whole of left medial pterygoid muscle [Figure 4] and [Figure 5]. The hyperdense region extended from left inferior-medial aspect of ramus angle to pterygoid blade. There was a uniform calcification observed throughout the muscle path in the 3D-CT volume-rendered images [Figure 6]. The above features were suggestive of MO of left medial pterygoid muscle.{Figure 3}{Figure 4}{Figure 5}{Figure 6}

After nasotracheal intubation, a combined intraoral and extraoral (submandibular and preauricular) approach was performed. The calcified mass involving left medial pterygoid muscle was exposed and completely excised. An intraoperative interincisal mouth opening of 37 mm was achieved [Figure 7]. The wound was closed in layers after complete hemostasis.{Figure 7}

Histopathological examination of the excised specimen showed foci of osteoid woven bone, cartilage, and collagen fibers consistent with the diagnosis of MO.

Postoperatively, aggressive jaw physical therapy was started. Rigorous physiotherapy was recommended, and the patient was routinely followed up. Follow-up at the end of the first month showed well-maintained facial symmetry. A slight deviation of mandible to the left side was observed at the maximum mouth opening. At ninth month, the retention surgical plates were removed. Tenth-month post-operative panoramic radiograph [Figure 8] shows satisfactory bone healing at the surgical site without any evidence of recurrence. At one-year follow-up maximum spontaneous mouth opening was 32 mm (reduced by 5 mm due to post-operative fibrosis). The patient did not complain about any difficulty during mastication.{Figure 8}


MOT involving the maxillofacial region is a rare clinical entity.[4] Thoma in 1958 described MOT as a condition generally caused by calcification and progressive ossification of intramuscular hematoma after trauma.[4] MOT is a benign, self-limiting, localized lesion that is characterized by ossification of fibrous connective tissue within skeletal muscle bundles after multiple traumatic episodes associated with muscle bleeding.[5] Thus, a bone morphogenic signal from the point of injury induces mesenchymal cells differentiation into osteoblast or chondroblasts.[3]

MOT is predominantly seen among males (male to female ratio 7:3); the average age of the patients is 36.6 years (range 21 to 65 years).[6] In a literature review by Boffano et al.[7] and Jiang Q et al.,[8] the mean ages observed were 38.1 (range 15–73 years) and 36.8 years (range 18–68 years), respectively. With respect to location, the masseter is the most affected followed by medial and lateral pterygoid, and temporalis muscle. This has been attributed to the external situation of the masseter, thus making it susceptible to direct external trauma.[6],[7] In our case, the patient had a clear history of multiple dental extractions following inferior alveolar blocks of the same side probably leading to MOT of the left medial pterygoid muscle.

Trismus is the most frequent symptom of MO involving the masticatory muscle.[1] Diagnosing MOT and other conditions that can cause reduced mouth opening has always been a clinician's dilemma. Peri-mandibular inflammation or abscess, foreign body reaction, tumour, musculoskeletal trauma, or temporomandibular joint diseases (ankylosis, anchored disc phenomenon, bilateral anterior disc displacement with reduction) must be considered under differential diagnosis.[6],[7],[9] Conner GA et al. reviewed 35 cases of MO and observed the history of trauma, previous surgical intervention, or injection among patients.[10]

Imaging techniques help with identifying the exact location and shape of ossification. They also aid in establishing the association between the lesion and surrounding tissues. Although plain radiographs have a limited role, yet they may show a soft tissue swelling and a faint peripheral calcification in the early stages of traumatic MO (less than 2–4 weeks). This is followed by well-defined calcification in the middle stages (5–24 weeks) that may be associated with coarser, central calcification. A fully matured traumatic MO (>6 months) is densely calcified and usually lies parallel to the long axis of the adjacent bones.[11] Panoramic radiograph may not be effective for determining the extent of the lesion due to the superimposition of the cranial bones. However, they may aid in the identification of odontogenic infection foci. Computed tomographic scans, especially three-dimensional reconstruction and magnetic resonance imaging scans of oral and maxillofacial regions, are considered efficacious in diagnosing MO. These also aid in planning surgical treatment.

Various treatment strategies have been discussed in the literature for MO. Surgical excision (of calcified mass or the entire muscle), physiotherapy (including TheraBite ™), medical therapy (non-steroidal anti-inflammatory drugs, bisphosphonates, magnesium, warfarin), and low-dose radiation therapy have been used.[12] However, the effectiveness of nonsurgical therapy for MOT till date is uncertain. Presently, the only treatment modality accepted widely is the complete excision of ossified mass as early as possible. Avoidance of surgical intervention has been recommended by few authors, unless a functional disability develops or the lesion regresses, as it is observed that 35%of MOT cases resolve spontaneously over several months.[10] We decided to perform total excision of left medial pterygoid muscle with an aim of avoidance of relapse of the disease. Post-operative active physical therapy was started by the first week of surgery to allow a re-established mandibular motion.

Literature data about recurrences are quite poor, as few articles offer follow-up greater than one year.[10]

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has/given /her/consent for /her/ 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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