MYOSITIS OSSIFICANS....

 In 1918, Dejerine and Ceillier first described heterotopic ossification (HO) in paraplegic patients injured in World War I, referring to the process as paraosteoarthropathy. HO has been defined as the formation of mature lamellar bone in soft tissues. The process involves true osteoblastic activity and bone formation. HO has been reported in cases of brain injury, spinal cord injury, stroke, poliomyelitis, myelodysplasia, tabes dorsalis, carbon monoxide poisoning, spinal cord tumors, syringomyelia, tetanus, and multiple sclerosis. This condition also has been reported after burns and total hip replacement.

Several terms have been used to describe the condition, including heterotopic ossification, ectopic ossification, and myositis ossificans. HO usually involves the large joints of the body (eg, hips, elbows, shoulders, knees). Excessive bone formation may result in significant disability by severely limiting the range of motion (ROM) of these joints (see Image 1).

The following 3 categories of HO have been described:

* Myositis ossificans progressiva is a rare metabolic bone disease in children with progressive metamorphosis of skeletal muscle to bone and is characterized by an autosomal dominant pattern of genetic transmission.

* Myositis ossificans circumscripta without trauma is a localized soft tissue ossification after neurologic injury or burns. This process also is referred to as neurogenic HO.

In relation to your original question some USA stastics showed:

An association has been cited between spasticity and HO. The incidence is higher in a spastic extremity; 84% of patients with HO had spasticity, and 54% of patients with HO had no spasticity. HO is seen in the elbow in 4% of patients with traumatic brain injury (TBI); however, if fracture or dislocation is associated with brain injury, the incidence of HO rises to 89%.Patients with brain injuries are at greater risk for developing HO if they have significant spasticity or increased muscle tone in the involved extremity, duration of unconsciousness longer than 2 weeks, long-bone or associated fractures, and decreased ROM. Therefore, the risk of development of HO in a patient with brain injury increases as the severity of injury, length of immobilization, and duration of coma increase.

* Traumatic myositis ossificans occurs from direct injury to the muscles. Fibrous, cartilaginous, and osseous tissues near bone are affected. The muscle may not be involved.

Pathophysiology: The specific cause and pathophysiology of HO remain unclear. HO may be due to an interaction between local factors (eg, the pool of available calcium in adjacent skeleton, soft tissue edema, vascular stasis tissue hypoxia, mesenchymal cells with osteoblastic activity) and an unknown systemic factor or factors. The basic defect in HO is the inappropriate differentiation of fibroblasts to bone-forming cells. Early edema of connective tissue proceeds to tissue with foci of calcification and then to maturation of calcification and ossification.


The typical Sport (post trauma) myositis ossificans is summarised below

Definition: Myositis ossificans is an unusual condition that often occurs in athletes who sustain a blunt injury that causes deep tissue bleeding. A typical story is a soccer player who is kicked forcefully in the mid-thigh, and develops pain and significant bruising.

The soft-tissues that were injured in the traumatic event initially develops a hematoma, and subsequently develop the myositis ossificans. The word myositis ossificans means that bone forms within the muscle, and this occurs at the site of the hematoma. No one knows exactly why this occurs in some people.

The common concern when abnormal bone is seen on a x-ray is that there is a tumor within the soft-tissues. Fortunately, myositis ossificans has some typical clues that usually make it easily differentiated from a tumor. If there is any question about the diagnosis, repeat x-rays will be obtained several weeks later to ensure the bone mass is a typical myositis ossificans.

Treatment of myositis ossificans consists of:

* Rest

* Immobilization

* Anti-Inflammatory Medication 

Rarely is surgical excision of the myositis ossificans warranted. If the myositis ossificans is removed before it is "mature," it will likely return. Therefore, most surgeons wait between 6 and 12 months before even considering removal. Furthermore, there is a chance of return even when removed very late. Generally, myositis ossificans is only removed surgically if it interferes with joint motion or if it is irritating a nerve