a five - year - old girl suffered a traumatic injury ( left condylar dislocation ) during a regular dental appointment . she had no history of other diseases or trauma on the face that could lead to a misinterpretation of the diagnosis before and after the condyle dislocation . at 10 years of age she began to progressively develop left side facial pain and jaw joint limitation on range of motion . unfortunately , she returned only two years later , presenting with mouth opening of 10  mm , no facial asymmetry , and no jaw joint pain or other symptoms ( figs . 1 and 2 ) . computer tomography ( ct ) exam was requested and revealed calcification of the left lateral pterygoid muscle , extending from the head of the mandible to the pterygoid process ( fig . thus , in order to allow the patient to open her mouth wider , the proposed treatment plan included left side pterygoid muscle excision . after general anaesthesia , an intraoral incision was done along the anterior mandibular ramus and the ossified mass was easily detected after detachment of mucosa . 4 ) and a 35  mm mouth opening was achieved immediately after the procedure ( fig . 5 ) . new post - operative ct images showed absence of calcified mass over the medial left mandibular . laboratories tests of calcium , alkaline phosphatase presented normal results and histopathological examination showed simply calcified bone confirming the pathology diagnosed pre - surgically . however , three weeks after surgery patient started to feel limitation upon mouth opening and a new ct showed a new big mass of bone formation along the surgical tract . one month after total bone structure removal ( first surgery ) the patient could not open her mouth anymore ( figs . 6 and 7 ) due to a significant calcified mass . traumatic miosytis ossificans is a rare clinical pathology , uncommon in the region of head and neck , and was first described by thoma in 1958 as a calcification and an intramuscular haematoma ossification after trauma . several other trauma injuries have been reported as the main cause for this condition , including third molar extraction , neck imobilization with cervical collar after laminoplasty , repeated absolute alcohol injection as trigeminal neuralgia treatment , temporomandibular joint luxation caused by 3-h mouth opening during periodontal surgery , direct or proximal physical trauma , odontogenic infection and anaesthetic injection . it is not completely understood why some patients developed an ossification of muscles after trauma , but it has many pathogenesis theories as follows : ( 1 ) displacement of bony fragments into the soft tissue and haematoma with following proliferation ; ( 2 ) detachment of periosteal fragments into the surrounding tissue with proliferation of osteoprogenitor cells ; ( 3 ) migration of subperiosteal osteoprogenitor cells into surrounding soft tissue , through periosteal perforation induced by trauma ; and , the most feasible and more accepted content among clinician , ( 4 ) metaplasia of extraosseous cells in contact to bony morphogenetic proteins derived from the lysis of bone fragments displaced within the soft tissue during traumatic injury . another possibility could be a genetic polymorphism inducing the disease in certain patients as in fibrodysplasia ossificans progressive , as described by carey . the masseter has been reported to be the predominant muscle involved with ossification , followed by temporalis , genioglossus , buccinator , medial pterygoid and lateral pterygoid . and males are more affected than females . elevated alkaline phosphatase was cited during evolution in some mo cases , perhaps resulting from disease inflammatory progress . early and complete excision of the involved muscles plus additional procedures in order to try to avoid recurrence are the worldwide therapy of choice for most surgeons . all procedures conducted in this case , such as osteotomy of the muscle attachment region , fat insertion ( considered to prevent heterotopic bone formation ) for haematoma formation prevention , associated to non - surgical treatments , such as corticosteroids , nonsteroidal anti - inflammatory drugs , bisphosphonates , and a low - dose radiotherapy and warfarin , have been reported as successful . unfortunately , the results from this case were not as expected and the patient developed a new calcified bone . as current follow up , this patient could benefit from a new surgical procedure or tmj prosthesis insertion . also , fractioned radiotherapy has shown some benefit for this pathology , but it compromises the region and contraindicates a surgery afterwards . another surgical procedure could result in scarring and recidive and tmj prosthesis would not prevent heterotopic bone formation . after all considerations , her father has decided to wait until his daughter grows older . the surgical technique used in this case avoided invasive gap arthroplasty to access lateral pterygoid muscle and anaesthetic scarring formation , by using an intraorally incision accessing the muscle directly as reported previously . the authors of these study did not see any relation with the condylar dislocation that the patient had five years prior to the pathology , and they could not find any real cause for the myositis ossificans of lateral pterygoid muscle . the outcome of the surgical procedure was not successful , perhaps due to the expression of the disease , indicating the need to further physiologic and genetic studies to elucidate the aetiology of mo as well as to provide directions to an adequate treatment choice for such cases . all authors participated in the treatment of the patient , before and after surgery.key learning pointintra oral access is a viable surgical option.post-operative images ( ct ) is mandatory for this kind of pathology.recurrence should be discussed and addressed with patient and family . intra oral access is a viable surgical option.post-operative images ( ct ) is mandatory for this kind of pathology.recurrence should be discussed and addressed with patient and family .