Myositis ossificans

Myositis ossificans
Classification and external resources
ICD-10	M61
ICD-9	728.1
MeSH	D009221

Myositis ossificans comprises two syndromes characterized by heterotopic ossification (calcification) of muscle.

Heterotopic Ossification Elbow1

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. 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) 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, pectoralis muscles, glutei, and the chest. 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 of the abnormal tissue is required, although success of such therapy is limited.

Treatment of myositis ossificans:

• Rest
• Immobilization
• Anti-inflammatory drugs
• Physiotherapy management
• Chiropractic care

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.