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MYOSITIS OSSIFICANS TRAUMATICA OF THE

MASSETER MUSCLE- review of the literature and

case report

Elitsa G. Deliverska,Department of Oral and Maxillofacial surgery, Faculty of dental medicine, MedicalUniversity, Sofia, Bulgaria

Journal of IMAB - Annual Proceeding (Scientific Papers) 2013, vol. 19, issue 4ISSN: 1312-773X (Online)

ABSTRACT:Introduction: Myositis ossificans traumatica (MOT) is

known mostly in the orthopedic literature as non-neoplastic,heterotopic bone formation within muscle or fascia,presumably due to acute trauma or repeated injury. Myositisossificans traumatica of the masseter muscle is uncommondisease producing limitation of opening of the jaws.

Purpose: To present a case of MOT of the massetermuscle in patient with history of facial trauma.

Material and methods: The medical history of a 53years patient with complaint of decreasing ability to open hismouth over the past 10 years after a blow to face. CT revealedenlarged calcification in the left masseter muscle.

Conclusion: Treatment of MOT of the masseter muscleis surgical- total extirpation of the ossified muscle but alsosurgical techniques including osteotomy that involve themuscle attachment region should be considered and after thatappropriate physical therapy.

Key words: MOT; masseter muscle;

INTRODUCTION:Myositis ossificans traumatica (eponyms: myositis

ossificans circumscripta, ossifying hematoma, calcifiedhematoma, parosteal bone formation) was initially describedby Thorma [9] in 1958 as a condition generally caused bycalcification and progressive ossification of an intramuscularhematoma after trauma. [7, 8] Very few cases have beenreported in the head and neck region. Arima et al. [2]reviewed the literature and discovered 26 cases involving thehead and neck. The muscles most commonly affected, indecreasing order of involvement, are the masseter (75%),temporalis, genioglossus, buccinator, and medial pterygoid.[2, 5] Only few cases have been reported with bilateralinvolvement .[7] Myositis ossticans traumatica (MOT) shouldbe differentiated from its related counterpart myositisossificans progressiva (MOP). MOP is a rare hereditaryconnective tissue disorder of unknown origin occurringprimarily in children. [4, 6, 10] The condition is autosomaldominant, with variable expressivity. MOP is characterizedby progressive ossification of any and all skeletal muscles ofthe body unrelated to trauma. Ossification of skeletal muscle,fascia, tendons, and ligaments occurs with seemingly no

definitive pattern. [1, 11]Many theories have been proposed. Carey’l [3]

summarized these as 1) displacement of bony fragments intothe soft tissue and hematoma with subsequent proliferation,2) detachment of periosteal fragments into the surroundingtissue with proliferation of osteoprogenitor cells, 3) “leakage”of subperiosteal osteoprogenitor cell into surrounding softtissue through periosteal perforations suffered via trauma, and4) differentiation of extraosseous cells exposed to bonemorphogenic protein (BMP). Most clinicians adhere to thelast theory. According to this theory, bone fragmentationduring trauma may result in autolysis and release of BMP intothe soft tissue mass; BMP induction of cellular differentiationwith progressive ossification then occurs. [2, 5]

Potential diagnoses to be considered are:1. Fibrous ankylosis, left temporomandibular joint; 2.

Scarring or calcification of the left masseter muscle (myositisossificans); 3. Left anterior disc displacement withoutreduction or “anchored disc phenomenon”; 4. Right coronoidimpingement; 5. Tumor

CASE REPORTWe present a 55 years-old man complained of a

decreasing ability to open his mouth over the past 10 years(fig. 1). After soft tissue blunt trauma (intramuscularhematoma of left masseter) he reveal progressive limitationof motion of the mandible (fig. 2). The patient was treatedinitially with nonsteroidal anti-inflammatory medications(NSAIDs), cold and hot compresses, and range of motionexercises. Nonsurgical therapy was unsuccessful and thepatient was referred to our department for evaluation inFebruary 2013. Clinical examination showed limited mouthopening- incisal opening to 3 mm and no lateral movements.Painless swelling palpated in this region. Palpation andauscultation of temporomandibular joints (TMJs) wereunremarkable. Differential diagnosis should be considered: 1)benign or malignant tumors; 2) degenerative condylarirregularities, or 3) a pathologic fracture.

The two most likely diagnoses were fibrous ankylosisand myositis ossificans. Scarring or myositis ossiticans (MO)of the masseter muscle seem like rare possibilities at first, butachieving an accurate diagnosis should not be difficult withthe addition of the medical history, physical, and imaging

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findings. CT finding showed of impressive extensivecalcifications of the masseter muscle attached to the adjacentbone by a broad, calcified stalk. CT revealed no obvious TMJpathology. The images could not rule out intraarticularadhesion or a fibrous ankylosis. (Fig. 3, Fig. 4)

The patient was scheduled for operation with extraoralapproach and release(osteotomia) the bony attachment of theinvolved left masseter muscle to the mandible, arthrotomyand release of fibrous ankylosis / coronoidectomia ifindicated.

DISCUSSIONMyositis ossificans traumatica (eponyms: myositis

ossificans circumscripta, ossifying hematoma, calcifiedhematoma, parosteal bone formation) was initially describedby Thoma [9] in 1958 as a condition generally caused bycalcification and progressive ossification of an intramuscularhematoma after trauma. Very few cases have been reportedin the head and neck region. Arima et al. [2] reviewed theliterature and discovered 26 cases involving the head andneck. Primarily single muscle involvement was reported. Themuscles most commonly affected, in decreasing order ofinvolvement, are the masseter, temporalis, genioglossus,buccinator, and medial pterygoid. The case presented here isMOT that involve the masseter muscle unilaterally. There isa prominent male:female ratio of 24:4. Myositis ossticanstraumatica (MOT) should be differentiated from its relatedcounterpart myositis ossificans progressiva (MOP). MOP isa rare hereditary connective tissue disorder of unknown originoccurring primarily in children. [9] Histologic findings ofMOT typically include newly formed lamellar bone withinfibrous strands of muscle tissue where previous trauma issuspected. There is a mixture of fibrous tissue, bone, and

occasionally cartilage. Careful histologic examination shouldbe performed to rule out extraosseous osteosarcoma. Elevatedalkaline phosphatise levels seem to occur during evolution ofMOT as a result of progress of the disease. Signs andsymptoms within the head and neck region can oftentimes beminimal until severe trismus is evident.[1, 2] A history oftrauma to the affected area is commonly elicited. Typically,there is limited posttraumatic evidence of ossification untiltrismus occurs. In the case presented, trauma caused by buffetmay have produced the hemorrhage/ autolysis to stimulate thesequence of events. Plain films are rarely helpful indiagnosing early ossification, and the introduction of CTscanning and MR imaging has aided in more timelyrecognition of the condition. It is not clear why some musclesare prone to ossification and others are not. No clinical orlaboratory studies have been linked to the diagnosis. [7] Thecase presented raises a question about the degree of traumanecessary to initiate ossification, as well as the theory behindits inception. In addition, it substantiates the belief thatoptimum postoperative results are achieved through completeexcision of the affected muscles and appropriate physicaltherapy.

CONCLUSION:It is not clear why some muscles are prone to

ossification and others are not. No clinical or laboratorystudies have been linked to the diagnosis. There are notreatment protocols, as the literature is unclear as to the needfor surgical intervention, surgical timing, recurrence rates, andeffectiveness of nonsurgical therapies. Good postoperativeresults are achieved through complete excision of the affectedmuscles and appropriate physical therapy after surgery.

Fig. 1. Patient with myosistis ossificans traumatic. Fig. 2. Limitation of motion of the mandible.

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Fig. 3. CT revealed enlargedcalcification in the left masseter muscle.

1. Akin RK, Keller AJ, Walters PJ.Myositis ossiticans rogressive: Adiagnostic problem. J Oral Surg. 1975Aug;33(8):611-615. [PubMed]

2. Akoi T, Naito H, Ota Y, et al:

Myositis ossificans traumatica of themasticatory muscles: Review of theliterature and report of a case. J OralMaxillofac Surg 60:1083, 2002

3. Arirna R, Shiba R, Hayashi T.

Traumatic myositis ossificans in themasseter muscle. J Oral MaxillofacSurg. 1984 Aug;42(8):512-526.[PubMed]

4. Bar Oz B, Boneh A. Myositis

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Fig. 4. Calcification of the left massetermuscle (myositis ossificans);

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Address for correspondence:dr Elitsa Deliverska,Department of Oral and Maxillofacial surgery, Faculty of Dental Medicine,1, Georgi Sofiyski blvd., 1431 Sofia, Bulgaria; tel.+359 888 949 740;email: elitsadeliverska@yahoo.com,