Myositis ossificans (OM) is characterized by limited bone formation within the muscle. OM is a tumor-like process localized in soft tissues [1]. The disease was first described in 1648 and is rare in children, except in those with an inherited condition known as progressive OM (fibrodysplasia ossificans progressiva, Münchmeyer's disease). The prevalence is 1 case in 2 million people [4]. There are also traumatic OM or limited OM [8, 16], and in patients with spinal cord injury - neurogenic OM [3].
OM is not associated with muscle inflammation, so some clinicians prefer to call this disease heterotopic ossification. In 70-80% of cases, the disease is localized on the thigh, shoulder, or buttock [1, 8]. In most cases, the appearance of OM is preceded by a single or multiple blunt trauma [5, 6]. The time between injury and detection of muscle changes can vary from 3 weeks to 20 years.
The scientific literature presents isolated cases of OM m. masseter, m. temporalis, m. pterygoideus, m. buccinator, m. platysma, m. sternocleidomastoideus
[10, 14]. Damage to the OM of the masticatory muscles is often unilateral, but bilateral lesions have also been described [7]. Cases of OM of the masticatory muscles were observed after complex removal of the lower third molar [4, 16], 4-week intensive therapy of a cancer patient with developed sepsis, neuromyopathy and nephropathy [7].
The reason for bone formation in muscle is unknown [5]. The pathogenesis of OM remains unknown. One theory is that muscle injury stimulates the proliferation of fibroblasts, which then undergo bone metaplasia. There is also a widely discussed theory that skeletal muscle injury induces the expression of bone morphogenetic protein at the injured site, which in turn stimulates primitive stem cells to differentiate into osteoblasts, leading to heterotopic ossification [16, 17]. According to E. Shore et al. [13], progressive OM is caused by a mutation in the gene encoding activin type kinase, which leads to changes in chondro- and osteogenesis [2, 12].
To date, the pathomorphology of ossification of the masticatory muscles and the differential diagnosis of OM have not been sufficiently studied.
The purpose of the study was to study the morphological features of OM in cases of damage to the masticatory muscles.
Material and methods
The study included 8 patients (3 women, 5 men) aged from 19 to 60 years (average age 33.8 years). When contacted, all patients complained of severe limitation of mouth opening and impaired chewing function. According to the anamnesis, 7 patients had a previous injury to the maxillofacial area; in 1 patient, the restriction of mouth opening was not associated with anything. The duration of the disease ranged from 1 to 12 months.
All patients underwent clinical, radiological, and laboratory examinations. In 7 patients, surgical treatment was performed with subsequent examination of the surgical material. The postoperative period proceeded without complications. Patients were prescribed symptomatic therapy, mechanotherapy, and physiotherapy. One patient refused surgery.
The surgical material was fixed in a 10% solution of neutral formaldehyde, decalcified in Biodek R solution, passed through alcohols of increasing concentrations, embedded in paraffin and microtomized. Histological sections were stained with hematoxylin and eosin, picrofuchsin according to Van Gieson.
Results and its discussion
In 7 patients, unilateral traumatic OM was detected with damage to only the masticatory muscles: m. pterygoideus lateralis
- at 1,
m.
temporalis - at 2,
m.
masseter - in 4. One patient with OM
m.
pterygoideus medialis denied any history of trauma. The duration of the disease was: 1 month - in 2 patients, 2 months - in 2 patients, 3 months - in 1 patient, 6 months - in 2 patients, 12 months - in 1 patient.
The reason for the patients’ referral was a persistent limitation of the mobility of the lower jaw, which interfered with eating and speech. The maximum mouth opening was 5-15 mm. When opening the mouth, the lower jaw shifted towards the affected muscle, sometimes with a clicking sound in the temporomandibular joint. There was no pain syndrome. Skin color was not changed. When m. is affected. temporalis
and
m.
masseter, a painless, non-displaceable area of tissue compaction with clear boundaries was determined by palpation.
Palpate m.
pterygoideus was not possible during clinical examination. No characteristic clinical symptoms of OM were identified.
Computed tomography excluded lesions of the temporomandibular joint and identified areas of ossification in the affected masticatory muscles with clear boundaries. Surgical treatment of 7 patients made it possible to restore the function of the lower jaw and chewing. No relapses of OM were observed.
Microscopic examination revealed different morphological structures of OM nodes in the masticatory muscles. Thus, a 19-year-old patient with a traumatic lesion of m. masseter
on the left 6 months ago, a node with well-formed bone beams, loose connective tissue with a small amount of intertrabecular tissue with weak calcification was microscopically determined
(Fig. 1).
Figure 1. Patient 19 years old. Myositis ossificans. Microphoto. Hematoxylin and eosin staining. ×400. a - formed bone beams among fibrous tissue, b - separated by a layer of loose connective tissue, bone beams with signs of degeneration. Fibrous tissue smoothly transitioned into bone tissue. Muscle fibers with signs of dystrophy.
A 60-year-old patient with damage to m. masseter
on the right, 6 months ago (after tooth extraction), a node was microscopically identified, delimited from the surrounding muscle tissue by coarse fibrous connective tissue
(Fig. 2).
Figure 2. Patient 60 years old. Myositis ossificans, zoning phenomenon. Microphoto. Hematoxylin and eosin staining. ×100. A delimited node (a) among fibrous tissue with a large number of fibroblasts (b) with areas of hyalinosis formed by bone beams (c) with signs of degeneration.
Muscle fibers with dystrophic changes. In the center of the node, fibrous tissue with proliferation of fibroblasts was detected. The middle zone is represented by immature osteoid and developing cartilage and bone tissue. The periphery of the node contained stroma with collagen fibers and a large number of bone beams. The “zoning phenomenon” was microscopically revealed.
A 44-year-old patient with a traumatic lesion of m. temporalis
on the left 12 months ago, OM in the mature stage was detected
(Fig. 3).
Figure 3. Patient 44 years old. Myositis ossificans. Microphoto. Hematoxylin and eosin staining. ×100. a — areas of degeneration of striated muscle fibers, b — a focus of bone tissue with signs of necrosis.
The microscopic picture was characterized by the presence in the muscle tissue of areas of bone structures with signs of necrobiosis. Muscle fibers are dystrophically changed. The node contained well-differentiated bone beams of irregular shape, randomly located areas of osteoid with weak calcification. The “zonal phenomenon” was absent.
OM is characterized by the appearance of a dense, immobile, painless node on palpation. The diagnosis of traumatic OM is based on the history of trauma (although in only 70% of cases patients report the presence of a blow), clinical symptoms, radiological signs and microscopic examination of biopsy material. Patients with OM of the masticatory muscles are characterized by limited mouth opening [11, 15]. According to R. Wiggins et al. [16], the development of traumatic OM goes through several histological phases: 1) early phase - rapid proliferation of fibroblasts; 2) intermediate phase - formation of osteoid, appearance of zoning; 3) the last phase is the formation of spongy bone and fat on the periphery.
The microscopic picture of OM is characterized by a significant diversity of tissue structures [1]. In the early stage, hemorrhages are observed among the fibrous connective tissue, foci of myxomatosis, angiomatosis, chondromatosis, and foci of calcification. Fibroblasts and fibrocytes in some places form clusters in large numbers. Fibroblasts are large or irregular in shape with a hyperchromic nucleus and granular cytoplasm. Mitotic figures are few in number. Inclusions of fat cells and foci of hematopoiesis may be observed. Foci of bone formation are observed at various stages of maturation. These may be areas of enchondral ossification, osteoid with varying degrees of calcification, and randomly arranged formed bone beams, often surrounded by osteoblasts.
In the mature stage of OM, the zoning of the structure is determined [1, 5, 8, 16]. The central zone is represented by undifferentiated spindle-shaped cells with abundant mitoses of fibrous, bone marrow tissue and necrotic muscle tissue. The middle zone with active osteoblasts, immature osteoid, developing cartilage and bone tissue is separated by thin-walled vascular canals [5, 16]. Along the periphery of the node there are well-differentiated bone beams with mature cancellous bone, osteoclasts and stroma containing collagen fibers [8]. The node is separated from the surrounding tissue by a layer of coarse fibrous connective tissue with cartilaginous areas and bone beams oriented along the periphery [1, 16]. The node contains bundles of muscle fibers, individual fibers with dystrophic changes, and myoblasts with eosinophilic cytoplasm.
The zonal architectonics of the histological structure of the OM in cases of damage to the masticatory muscles is described by many researchers [1, 5, 8, 16]. In a histological study of the OM of the masticatory muscles, S. Meng et al. [9] in 5 cases found zonal changes in areas of muscle ossification; in 10 cases there was no zonation. Our study also identified cases of zonal and non-zonal structure of the OM node in cases of damage to the masticatory muscles.
Conclusion
Features of the morphological structure of the OM: abundance of osteoid, immature unevenly mineralized bone trabeculae with round osteoblasts and osteoclasts in the vascular base. These structures are also detected in osteoid osteoma and osteoblastoma, but in them there is “reverse zoning”, i.e. mature bone in the center and immature osteoid with cell proliferation at the edge.
OM must be differentiated from benign connective tissue tumors, osteoma, osteoblastoma, osteosarcoma, nodular fasciitis, rhabdomyoma, chondroma, osteochondroma [1, 16].
Thus, the OM of the masticatory muscles has a different morphological structure with the presence or absence of zonation during tissue ossification. Proposed by E.L. Neustadt and A.B. Markochev [1] differential signs of OM: 1) absence of spicules, Codman’s triangle during X-ray examination, 2) a small number or absence of mitotic figures in cells, 3) a large number of mature bone beams, 4) zonality of the microscopic structure, - must be supplemented with an inconsistent sign of zonation node with damage to the masticatory muscles, persistent impairment of the mobility of the lower jaw without pain.
The main causes of trismus
Often the causes of trismus are diseases that are localized near the jaw:
- osteomyelitis of the jaw;
- inflammatory process of masticatory muscles;
- jaw injuries;
- periostitis;
- advanced caries, extensive carious damage to teeth;
- inflammation of the gum tissue;
- acute stage of pulpitis;
- inflammation of the periosteum of the lower jaw;
- abscesses.
Compression can also occur in the background:
- neurosis;
- brain inflammation;
- cerebrospinal meningitis;
- epileptic seizures;
- paralysis;
- cerebral hemorrhages;
- rabies;
- muscle cramps;
- tetanus;
- tumor processes;
- hysteria.
Sometimes the disease can occur due to a direct blow to the jaw area, due to an unexpected dousing with cold water. Often a spasm occurs after an animal bite (one of the consequences of rabies).
What can you do at home if:
Head muscle spasms
To relieve spasm and pain, you can take aspirin, a painkiller tablet like Ibuprofen, or a painkiller in powder form (for example, Nimesil). Give yourself peace of mind. You can try pressing trigger points and stretching your earlobes.
Jaw muscle spasm
If trismus manifests itself, before the doctor arrives, you can self-massage the masticatory muscles, accelerating the blood in them, alternately pressing on the muscles constrained by spasm. It is also possible to use compresses (alternate warm and cold compresses, apply them to the lower third of the face).
Cervical muscle spasms
Make gentle rotational movements with your head, lower and lift it (without throwing it back too much), turn it right and left. You can try stretching your neck muscles with your hands. Warm compresses and rubbing are effective.
*Attention! The information is for informational purposes only and does not constitute medical advice.
Reviews
Tatiana
I am happy to be among your guests at the clinic, I enjoy our communication, I am grateful for your super professionalism, for giving beauty and a sense of confidence in your professional actions, protection from “age-related changes”