Which of the following is not true about Myositis ossificans?
A i.e. Associated with muscle tendon rupture Myositis Ossificans (M.O) / Hetrotropic Ossification It is hetrotropic calcification and ossification in muscle tissue. The name is misnomer as there is no myositis (inflammation of muscle) and rarely ossification in the muscle (because the mineral phase differs from that in bone and no true bone matrix is formed). Etiology Injury (trauma) is an impoant factor and m.o. associated with trauma is better k/a post traumatic ossification it is seen in - Elbow > hipQ are commonly involved joints. - Trauma around elbowQ eg. fracture supracondylar humerus, dislocation or surgery. - Surgical trauma specially total hip replacement, - Massage to the elbow and vigorous passive stretchine to restore movements is aggravating factor. - Repeated micro trauma and overuse injuries. This type usually involve soleus muscle in ballerians. It occurs in muscles which are vulnerable to tear under heavy loads, such as quadriceps, adductors, brachicilisQ, biceps, and deltoid. M. 0. not associated with traumatic injury is termed as Pseudomalignant mysitis ossificans. And it is seen in Neurological disorders eg.G.B syndrome, AIDS encephalopathy, closed head injury, hypoxic brain injury & burns. Pathogenesis - Bone formation in muscle represents metaplasia of fibroblast at the site of injury. - Paial rupture & avulsion of muscle , ligament & joint capsule from bone usually cause periosteal elevation with the formation of subperiosteal hematoma and the wide exposure of cells with osteogenic potential. It inevitably lit subperiosteal ossification. - It has four microscopic zones (Ackerman Zonation) with centre most zone of undifferentiated, highly active (mitotic) cells and the outermost zone of well oriented hone encapsulated by fibrous tissue. - It must be distinguished from extaskeletal osteosarcoma. The latter usually occur in elderly, lacks zonationQ, and the most peripheral regions of osteosarcoma are most cellular & primitive, which is reverse of m.o. - It is distinguished from calcinosis, which is a metabolic disorder, often associated with collagen diseases - scleroderma & dermatomyositis. It is distinguished from ectopic calcification, which occurs in the capsule of joints, commonly the shoulder and is caused by inflammatory reaction around deposits of hydroxy - appetite crystals. And it is seen in CRF, hypo/hyper Clinical feature - Mostly asymptoma tic but may present with tenderness, palpable swelling, pain on range of motion, stiffness, and increased warmth. Imaging - Radiographs initially are normal, but by 10 days to 4 weeks fine calcification (dotted veil/ cotton wool appearance) is seen. - There is peripheral ossification and central lucencyQ of the mass. - The mass is usually seperated from underlying bone by at least a thin lineQ & lesion are usually located in the diaphysis. If the lesion is in continuity with the bone it is not myositis ossificans and the possibility of tumor or infection arises. - Calcification may first be noted on USG (focal hypoechoic mass located with in the muscle). - CT is better than x - ray - Biopsy before 4 weeks is usually in accurate. Treatment of Myositis Ossificans - Treatment is normally by 'watchful inactivity'. It must be emphasised that it is a passive stretching and not active exercise that is responsible for stimulating new growth formation. The worst treatment is to attack an injured and stiffish elbow with vigorous mucle stretching exercises; this is liable to precipitate or aggrevate the condition. So any physical therapy should be discontinuedQ. - Relative rest of the affected extremity is helpfulQ, with motion & activity gradually resumed as the acute phase subsides. In acute phase the treatment consist of limiting motion & icing the extremity while avoiding heat or massage - Low dose irradiation & indomethacin may prevent hetrotopic ossification, but the radiation should be avoided in children. - Surgical excision in toto is not done until a year or 2 after the acute phase of disease, at a time when radiograph reveal that the bone is fully mature and bone scan show either a return to normal uptake or decreasing activity in the lesion.
Associated with muscle tendon rupture
Inflammation around the ruptured muscle deposition of hydroxyapatite crystals with
Common in supracondylar fracture
Ossification of musculo-periosteal haematoma