Myositis ossificans comprises two syndromes characterized by heterotopic ossification

Heterotopic ossification

Heterotopic ossification is the process by which bone tissue forms outside of the skeleton.-Diagnosis:During the early stage, an x-ray will not be helpful because there is no calcium in the matrix...

 (calcification) of muscle.

Classification

• In the first, and by far most common type, nonhereditary myositis ossificans (commonly referred to simply as "myositis ossificans", as in the remainder of this article), calcifications occur at the site of injured muscle, most commonly in the arms or in the quadriceps of the thighs.
  • The term myositis ossificans traumatica is sometimes used when the condition is due to trauma
    Physical trauma
    Trauma refers to "a body wound or shock produced by sudden physical injury, as from violence or accident." It can also be described as "a physical wound or injury, such as a fracture or blow." Major trauma can result in secondary complications such as circulatory shock, respiratory failure and death...
    
    . It is passive stretching then active exercise, is responsible for bone formation.
• The second condition, myositis ossificans progressiva (also referred to as fibrodysplasia ossificans progressiva
  Fibrodysplasia ossificans progressiva
  Fibrodysplasia ossificans progressiva , sometimes referred to as Stone Man Syndrome, is an extremely rare disease of the connective tissue. A mutation of the body's repair mechanism causes fibrous tissue to be ossified when damaged. In many cases, injuries can cause joints to become permanently...
  
  ) is an inherited affliction, autosomal dominant pattern, in which the ossification can occur without injury, and typically grows in a predictable pattern.

Presentation

The condition may sometimes be diagnosed from radiographs obtained for unrelated problems.

Most (i.e. 80%) ossifications arise in the thigh or arm, and are caused by a premature return to activity after an injury. Other sites include intercostal spaces, erector spinae

Erector spinae

The Erector spinæ is a muscle group of the back in humans and animals. It is also known as sacrospinalis in older texts. A more modern term is extensor spinae, though this is not in widespread use. The name of the muscle is pronounced e-rec-tor speen-aye, or e-rec-tor spinae-ee.It is really not...

, pectoralis muscles, glutei, and the chest

Chest

The chest is a part of the anatomy of humans and various other animals. It is sometimes referred to as the thorax or the bosom.-Chest anatomy - Humans and other hominids:...

. Hazy densities are sometimes noted approximately one month after injury, while the denser opacities eventually seen may not be apparent until two months have passed.

If the ossification is located in the adductor muscles, it is known as "Prussian's disease".

Pathophysiology of myositis ossificans traumatica: The specific cause and pathophysiology are unclear - it may be caused by an interaction between local factors (e.g., a reserve of available calcium in adjacent skeletal tissue or soft tissue edema, vascular stasis tissue hypoxia or mesenchymal cells with osteoblastic activity) and unknown systemic factors. The basic mechanism is the inappropriate differentiation of fibroblasts into bone-forming cells (osteoblasts). Early edema of connective tissue proceeds to tissue with foci of calcification and then to maturation of calcification and ossification.

Prevention

Radiation therapy subsequent to the injury or as a preventive measure of recurrence may be applied but its usefulness is inconclusive .

Treatment

Treatment is initially conservative, as some patients' calcifications will spontaneously be reabsorbed, and others will have minimal symptoms. In occasional cases, surgical debridement

Debridement

Debridement is the medical removal of a patient's dead, damaged, or infected tissue to improve the healing potential of the remaining healthy tissue...

of the abnormal tissue is required, although success of such therapy is limited.

Treatment of myositis ossificans:

• Rest
• Immobilization
• Anti-inflammatory drugs
• physiotherapy management

Surgical removal of the myositis ossificans is rarely warranted. If the myositis ossificans is excised before its maturation, it will likely reoccur. Consequently, most healthcare providers wait 6-12 months before considering excision. There is a chance of relapse even when removed in a mature state. In general, myositis ossificans is removed surgically if it limits the range of motion of the joint, irritates a nerve or lowers quality of life.