Myositis Ossificans of the Left Medial Pterygoid Muscle: Case Report and Review of the Literature of Myositis Ossificans of Masticatory Muscles

Abstract

Myositis ossificans is a disease that is characterized by nonneoplastic, heterotopic bone formation within a muscle. Myositis ossificans traumatica, also called myositis ossificans circumscripta, is a disease in which muscles are ossified presumably following acute trauma, burns, surgical manipulation, or repeated injury. It is often remitted after surgical excision though some patients have repeated recurrences. Myositis ossificans traumatica of masticatory muscles is not frequently reported in the literature, with the most common clinical finding being a progressive limitation of motion in the mandible. The aim of this article is to present and discuss a case of myositis ossificans traumatica of the left medial pterygoid muscle and to review the literature of myositis ossificans of the masticatory muscles.

Myositis ossificans (MO) is a disease that is characterized by nonneoplastic, heterotopic bone formation within a muscle. MO can be classified into MO progressive (or fibrodysplasia ossificans progressive), that is the autosomal dominant disease with multiple, heterotopic ossifications in the systemic muscle, fascia, tendons, and ligaments, and MO traumatica.^{1 2 3 4 5 6}

MO traumatica, also called MO circumscripta, is a disease in which muscles are ossified presumably following acute trauma, burns, surgical manipulation, or repeated injury.^{1 3 4}

Unlike MO progressive, MO traumatica is often remitted after surgical excision though some patients have repeated recurrences.¹

MO traumatica of masticatory muscles is not frequently reported in the literature,^{1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37} with the most common clinical finding being a progressive limitation of motion in the mandible.^{2 3 4}

The aim of this article is to present and discuss a case of MO traumatica of the left medial pterygoid muscle and to review the literature of MO of the masticatory muscles.

Case Report

A 37-year-old woman referred to the Division of Maxillofacial Surgery of the University of Turin with a complaint of trismus. She reported a blow to the left side of her face several years before and a progressively increasing limitation of mandibular motion for the last 2 years. Her medical and family history was unremarkable.

At clinical examination, she had trismus, with a maximum interincisal opening of the mouth of 5 mm. The patient was also unable to protrude or produce a left lateral excursion. The occlusion was stable, without significant intraoral findings. Neither swelling nor pain of the left side of her face could be appreciated on palpation (Fig. 1). Submandibular and cervical lymph nodes were nonpalpable and nontender. Results of hemogram and tests for serum phosphatase, parathyroid hormone, and calcitonin were within normal limits. A panoramic radiograph revealed a radiopaque calcified region with apparent bony features in correspondence of the left coronoid process and sigmoid notch. (Fig. 2) Axial and coronal computed tomography (CT) scans confirmed the presence of irregular heterotopic calcification involving the left medial pterygoid muscle (Figs. 3 and 4).

Figure 1.

Preoperative frontal (A) and lateral (B) images of the patient.

Figure 2.

Panoramic radiograph revealing a radiopaque calcified region with apparent bony features in correspondence of the left coronoid process and sigmoid notch.

Figure 3.

Axial computed tomography scan confirming the presence of irregular heterotopic calcification involving the left medial pterygoid muscle.

Figure 4.

(A) Coronal computed tomography scan confirming the presence of irregular heterotopic calcification involving the left medial pterygoid muscle. (B) The medial pterygoid muscle origin is on the bottom of the mandible, but in this pathological case the ossification of some muscular fibers did not reach the bottom of the mandible. Therefore, the osteotomy was made to remove just the inner corticle and to remove the condyle.

Surgical excision of the ossification was planned under general anesthesia.

After fiber optic-assisted nasotracheal intubation, a combined intraoral and extraoral (submandibular and preauricular) approach was performed. The calcified mass within the left medial pterygoid muscle was exposed and completely excised together with the left coronoid and condyle by surgical burs and trimmer. After removal of the fused mass and site preparation, Biomet/W Lorenz Surgical System temporomandibular joint (TMJ) prosthesis (Biomet/Lorenz, Warsaw, IN) with condylar and fossa components was placed. An intraoperative interincisal mouth opening of 35 mm was achieved. The wound was closed in layers after complete hemostasis.

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

Aggressive jaw physical therapy was started postoperatively. A rigorous physiotherapy was recommended, and the patient was regularly followed up. Follow-up at 30 days confirmed the restoration of the posterior ramus height and the maintained facial symmetry (Fig. 5); furthermore, maximum spontaneous opening mouth recovered to 31 mm. Postoperative radiographs showed excision of the ossification and the correct placement of the TMJ prosthesis (Figs. 6 and 7). Follow-up at 3 years was unremarkable without any evidence of recurrence.

Figure 5.

Postoperative frontal (A) and lateral (B) images of the patient confirming the maintained facial symmetry after surgical treatment.

Figure 6.

Postoperative panoramic radiograph showing the excision of the ossification and the correct placement of the temporomandibular joint prosthesis.

Figure 7.

Postoperative posteroanterior cranial radiograph confirming the correct placement of the temporomandibular joint prosthesis.

Discussion

MO traumatica is an extraskeletal bone-forming disease in the head and neck region.⁴

The term “MO traumatica” may be inadequate to describe this disorder, because in various cases a history of trauma cannot be recognized^{3 4 7 15 32} and there is little inflammation.

The pathogenesis of MO is still controversial and several theories have been proposed. The most widely accepted theory involves the differentiation of extraosseous cells exposed to bone morphogenic proteins that would have been released from native bone sources following trauma or surgical injury.^{1 2 4}

Other theories suggested the displacement of bony fragments into the surrounding tissue and hematoma with subsequent bony proliferation, the detachment of periosteal fragments into the soft tissue with proliferation of osteoprogenitor cells, or the migration of subperiosteal osteoprogenitor cells into surrounding tissue through periosteal perforations.²

Laboratory tests are usually within normal ranges, except for some cases with a reported elevated alkaline phosphatase level that might be due to disease progression.⁴

An English literature review revealed 42 cases of MO of the masticatory muscles, including our case. The results are shown in Table 1. Mean age of affected patients is 38.1 years (range, 15–73 y; median, 34 y; standard deviation, 14.2). Men were 29, whereas female patients were 12, with a ratio M:F of 2.4:1.

Table 1. Review of cases of myositis ossificans of masticatory muscles in the literature.

Case	Author	Year	Age	Sex	Location	History of trauma	Treatment	Outcome
1	Ivy and Eby7	1924			Masseter	Unknown	Excision/removal of the entire muscle	Immediate full opening, no follow-up
2	Cameron and Stetzer8	1945	28	M	Masseter	Fall	Excision	Recurrence in 6 mo, reintervention
3	Nizel and Prigge9	1946	21	M	Masseter	Gunshot	Expansion appliance/exercise	No follow-up
4	Kostrubala and Talbot10	1948	21	M	Masseter	Gunshot	Excision/removal of the entire muscle	Recurrence in 1 mo, second intervention with dermal graft; good function 9 mo later
5	Davidoff11	1955	53	M	Masseter	Contusion	Excision	No follow-up
6	Goodsell12	1962	39	M	Masseter	Blow	Excision	No recurrence
7	Palumbo et al13	1964	52	M	Masseter	Blow	Excision/removal of the entire muscle	No recurrence
8	Parnes and Hinds14	1965	27	M	Masseter	Blow and bite wound	Excision	No recurrence
9	Hellinger15	1965	21	F	Masseter, temporali, lateral pterygoid	Unknown	Biopsy	No follow-up
10	Shawkat16	1967	24	M	Masseter, temporalis	Blow, tooth extraction	Excision	No recurrence
11	Vernale17	1968	29	M	Masseter	Contusion	Excision	No recurrence
12	Vernale17	1968	31	M	Masseter	Traffic accident	Excision	No recurrence
13	Trester et al18	1969	29	F	Masseter	Overturning	Excision	Recurrence in 1 mo
14	Narang and Dixon19	1974	49	M	Medial pterygoid	Tooth extraction	Excision	Recurrence in 1 mo
15	Plezia et al20	1977	47	F	Masseter	Contusion	Excision	No recurrence
16	Christmas and Ferguson21	1982	51	M	Masseter	Fall	Excision	No recurrence
17	Abdin and Prabhu22	1984	43	F	Lateral pterygoid	Drainage after odontogenic infection	Excision	No recurrence
18	Arima et al23	1984	25	M	Masseter	Struck on the cheek	Excision	No recurrence
19	Lello and Makek24	1986	31	F	Masseter	Anesthetic injection	Excision	No recurrence
20	Lello and Makek24	1986	32	M	Masseter	Struck on the cheek	Excision	No recurrence
21	Lello and Makek24	1986	34	M	Temporal, lateral pterygoid	Traffic accident	Excision	No recurrence
22	Nilner and Petersson25	1989	57	M	Medial pterygoid	Anesthetic injection	Physical therapy	Unknown
23	Parkash and Goyal26	1992	28	M	Medial pterygoid	Pericoronitis	Excision, condylectomy, coronoidectomy	No recurrence
24	Tong et al27	1994	73	F	Bilateral medial pterygoid	Anesthetic injection	Biopsy	Unknown
25	Steiner et al28	1997	40	M	Masseter	Mandibular fracture	Excision	No recurrence
26	Steiner et al28	1997	15	F	Masseter	Shotgun wound	Excision, coronoidectomy	No recurrence
27	Spinazze et al29	1998	55	M	Masseter, temporal, lateral pterygoid, medial pterygoid	Periodontal surgery	Coronoidectomy	Twice recurrence (then excision, then arthroplasty plus osteotomy)
28	Myoken et al30	1998	53	M	Bilateral temporal, masseter	Laceration over ear	Excision	Unknown
29	Geist et al31	1998	44	M	Masseter	Mandibular fracture	Excision	Unknown
30	Takahashi and Sato32	1999	71	F	Medial pterygoid	Unknown	Excision	No recurrence
31	Aoki et al1	2002	44	M	Masseter, lateral pterygoid, medial pterygoid	Struck on the cheek	Excision	Recurrence
32	Kim et al4	2002	30	F	Bilateral lateral pterygoid	Unknown	Excision	Recurrence (excision and interpositional fat graft)
33	Saka et al33	2002	33	M	Temporal	Blunt trauma	Excision	No recurrence
34	Yano et al34	2005	34	M	Bilateral masseter	Violence	Excision and coronoidectomy	No recurrence
35	Rattan et al6	2008	45	M	Medial pterygoid	Alcohol injection for trigeminal neuralgia	Excision and buccal fat pad	No recurrence
36	Conner and Duffy2	2009	18	F	Medial pterygoid, temporal	Surgical extraction of third molars	Excision and coronoidectomy	Twice recurrence (then mandibular resection, then condylar disarticulation)
37	Ramieri et al5	2010	64	M	Lateral pterygoid, temporal. Then Medial pterygoid	Tooth extraction	High condylectomy, then excision	Unknown
38	Trautmann et al35	2010	33	M	Medial pterygoid	Anesthetic injection, coronoidectomy	Excision	Unknown
39	Godhi et al3	2011	21	M	Temporal, bilateral lateral pterygoid	Unknown	Excision	No recurrence
40	Thangavelu et al36	2011	36	F	Medial pterygoid	Tooth extraction	Excision and interpositional fat graft	No recurrence
41	Ebbert et al37	2012	45	M	Bilateral medial and lateral pterygoid	Tooth extraction	Surgery deferred	Unknown
42	Present case	2012	37	F	Medial pterygoid	Unknown	Excision, condylectomy and TMJ prosthesis	No recurrence

Abbreviation: F, female; M, male; mo, month(s).

In 29 patients only a masticatory muscle was involved, while in the remaining 13 cases two or more muscles were affected by MO. Masseter was the most frequently involved muscle, with 25 patients, followed by medial pterygoid muscle (14 patients), lateral pterygoid muscle (9 patients), and temporalis muscle (5 patients).

The higher incidence of MO of masseter may be attributed to the external position of this muscle that is likely to receive a direct trauma.¹

The most frequent subjective symptom of MO is trismus,^{1 3} that should be differentiated from trismus related to perimandibular inflammation or abscess, tumor, trauma, or TMJ diseases.^{38 39}

Diagnosis of MO may be challenging, and an accurate history is essential, as a history of trauma, previous surgical intervention, or injection was recognized in 35 cases.²

On plain radiographs, that are usually performed first, it may be difficult to identify the real amount and site of ossification because of the superimposition of the cranial bones.^{1 2} CT scans are fundamental to perform a correct diagnosis, and to accurately plan a surgical treatment.

The pathognomonic feature of MO is a well-circumscribed, high-attenuating periphery with a low-attenuating central portion, whereas lesions may or may not be attached to the adjacent bone depending on the maturity of MO.

As Kim et al⁴ said, early lesions of the axial skeletons are reported to appear as amorphous calcifications within soft tissue, more mature lesions appear well circumscribed with a ring of calcification surrounding a relatively radiolucent central portion, and finally long-standing lesions may appear diffusely calcified and attached to the adjacent bone.

Histopathologically, MO typically present a peripheral zone with mature lamellar bone and active osteoclasts, an intermediate area made up of osteoid and cartilage, and a central cellular area with proliferating fibroblasts, spindle cells, and prominent giant mesenchymal cells.^{4 33}

Several different treatment strategies of MO have been proposed in the literature: mostly, a simple excision of the calcified mass was performed (25 cases). Some surgeons proposed a further surgical phase in addition to the excision of the mass: the removal of the entire muscle (3 cases), a coronoidectomy and/or condylectomy (6 cases), or an interpositional fat graft (2 cases). Interestingly, some authors just performed a biopsy or suggested functional exercise.^{9 15 25 27}

Therefore, treatment of MO is controversial and may be challenging. There are no treatment protocols, as the literature almost always just includes single case reports, and authors are often unclear as for surgical timing.² In particular, some authors insist that early surgical intervention (within 3–6 wk postinjury) is ideal for curative excision,^{14 23} whereas others have stated that surgical intervention should be initiated only when the disease has completely halted.² Biopsy is usually contraindicated, though a biopsy is often performed to exclude the possibility of malignant tumors.³ However, complete excision of the ossified mass seems to be the universally accepted treatment for this disease.

On the other hand, reconstruction options vary widely and are much more controversial. In fact, several authors did not perform any reconstruction after the removal of the ossified mass, whereas few articles mentioned the use of interpositional fat graft.^{6 36}

Literature data about recurrences are quite poor, as few articles offer follow-up greater than 1 year.²

We decided to perform a total TMJ replacement in addition to the removal of the mass, the coronoidectomy, and the condylectomy. The aim of this treatment was to avoid a relapse of the disease and to allow a reestablished mandibular motion. The use of a total alloplastic TMJ prosthesis may give several advantages in comparison with other surgical reconstruction techniques: in fact, physical therapy can begin immediately, there is no need of donor site, the restoration of the posterior ramus height can be immediately obtained after the removal of the mass, and last but not the least facial symmetry can be maintained too.

In conclusion, recommendations about treatment of MO should be cautiously made as limited data are available about recurrences and long-term follow-up.