MYOSITIS OSSIFICANS

MYOSITIS OSSIFICANS

Q. 1 What is myositis ossificans?

 A Worm calcification

 B

Callus formation

 C

Regeneration

 D

Post traumatic ossification

Q. 1

What is myositis ossificans?

 A

Worm calcification

 B

Callus formation

 C

Regeneration

 D

Post traumatic ossification

Ans. D

Explanation:

Myositis ossificans refers to ossification within the muscle which occur when there is sufficient trauma to cause a hematoma that later heals in the manner of a fracture.

The injury is usually a contusion and most commonly occur in the quadriceps of the thigh or triceps of the arm.

Patients usually presents with local swelling, heat and extreme pain on the slightest motion of the adjacent joint.  

Treatment: Involves resting until local reaction subsides, followed by gentle active excercises.

Surgery when indicated is usually done before 9 months to 1 year after injury.

Ref: CURRENT Diagnosis & Treatment: Pediatrics, 20e, chapter 24


Q. 2

A 15-year-old boy developed myositis ossificans following an elbow injury.

Assertion: It is a common condition in children compared to adults.

Reason: The periosteum is loosely attached to the bones in children.

 A

Both Assertion and Reason are true, and Reason is the correct explanation for Assertion

 B

Both Assertion and Reason are true, and Reason is not the correct explanation for Assertion

 C

Assertion is true, but Reason is false

 D

Assertion is false, but Reason is true

Ans. A

Explanation:

This is the ossification of the hematoma around a joint, resulting in the formation of a mass of bone restricting joint movements, often completely.

It is particularly common around the elbow joint. Massage following trauma is a factor known to aggravate myositis.

 Pathology: Myositis ossificans the ossification between the muscles is brought about by the osteoblasts, which are activated by stripping of the periosteum from the underlying bone. Since, in children, the periosteum is loosely attached to the bone, the periosteum is stripped off easily and widely. This is the reason why the condition is more common in children compared to adults. 

Q. 3 After an injury of a joint an 8 year old child developed stiffness of the joint. Development of myositis ossificans is seen in X-ray. The joint commonly involved is:

 A

Knee

 B

Elbow

 C

Shoulder

 D

Hip

Ans. B

Explanation:

Myositis ossificans or post-traumatic ossification is the process of ossification within muscle occurs when sufficient trauma causes a hematoma that later heals in the manner of a fracture.
Contusions of the quadriceps of the thigh or the triceps of the arm (around the elbow) are the most common injuries.
Disability is great, with local swelling, heat and extreme pain with the slightest provocation of the adjacent joint.
The limb should be rested until the local reaction has subsided (5–7 days). 
 
Ref: Erickson M.A., Merritt C., Polousky J.D. (2012). Chapter 26. Orthopedics. In W.W. Hay, Jr., M.J. Levin, R.R. Deterding, J.J. Ross, J.M. Sondheimer (Eds), CURRENT Diagnosis & Treatment: Pediatrics, 21e.

Q. 4

Histology of Myositis ossificans mimics –

 A

Osteosarcoma

 B

Osteosarcoma

 C

GCT

 D

Ewing’s tumour

Ans. A

Explanation:

Ans. is ‘a’ i.e., Osteosarcoma

o Histologically myositis ossificans mimics osteosarcoma.

o They can be differentiated by zone phenomenon :-

a Osteogenic sarcoma –>         Central zone contains mature cells and peripheral zone contains more active immature cells.

 Myositis ossificans –>            Central zone contains active immature cells and peripheral zone contains more mature cells.


Q. 5 Myositis ossificans is most common around the — joint

 A Knee

 B

Elbow

 C

Wrist

 D

Hip

Ans. B

Explanation:

B i.e. Elbow


Q. 6

Myositis ossificans is due to:

 A

Ossification

 B

New bone formation

 C

Ossification of subperiosteal haematoma

 D

All of the above

Ans. D

Explanation:

D i.e. All


Q. 7

Treatment of choice in Acute myositis ossificans is:

 A

Immobilization of elbow

 B

Short wave diathermy

 C

Passive movements of arm

 D

Active exercises

Ans. A

Explanation:

A i.e. Immobilization of elbow

* Rest of the affected part during the period while the process is active is the basic principle of treatment(TN 91) .

* No massage should be given.

* If any physical therapy is going on, it should be discontinued immediately.

* All passive movements and vigorous exercise must be stopped. Very gentle exercise must be started.

* Indomethacin and radiotherapy prevent calcification. However, radiotherapy should be avoided in children.

  – Surgical excision is indicated if myositis ossificans interferes with function. It is worth noting that surgical excision is contraindicated during active phase when calcification matures.

* Surgical excision, if required, should be done only after complete maturation of ossification.


Q. 8

Following are recognized F/O Myositis ossificans EXCEPT:

 A

It is a post traumatic ossification

 B

It follows either a posterior dislocation or a spuracondylar fracture of elbow joint

 C

The complication is less likely in children

 D

Diagnosis is made with certainty by skiagraphy

Ans. C

Explanation:

C i.e. The complication is less likely in children


Q. 9

In myositis ossificans mature bone is seen:

 A

At periphery

 B

In center

 C

Whole muscle mass

 D

In the joint capsule

Ans. A

Explanation:

A i.e. At periphery


Q. 10

Radiological feature differentiating myositis ossificans from bone tumor is:

 A

Peripheral ossification

 B

Central lucency

 C

Discontinuity with the bone

 D

None

Ans. C

Explanation:

C i.e. Discontinuity with the bone 


Q. 11

Which of the following is not true about Myositis ossificans?

 A

Associated with muscle tendon rupture

 B

Inflammation around the ruptured muscle deposition of hydroxyapatite crystals with

 C

Common in supracondylar fracture

 D

Ossification of musculo-periosteal haematoma

Ans. A

Explanation:

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 important 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.

– Partial 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.


Q. 12 All are true regarding myositis ossificans progressive except

 A Usually involve childs

 B

Progressive form of normal myositis

 C

Respiratory problems

 D

Ankylosis

Ans. B

Explanation:

B i.e. Progressive form of normal myosites

Fibrodysplasia (Myositis) Ossificans Progressiva

Patho Histology

– It is a rare autosomal dominant (AD) disorder of connective tissue differentiation.

–  Main pathogenic mechanism is defective regulation of the induction of endochondral ossification

–   Intense perivascular lymphocytic infiltration into
normal skeletal muscles is the earliest featureQ

–  The proliferating loose myxoid fibrous tissue infiltrates and replaces normally formed fibrous connective tissue and striated muscle

–  Numerous small blood vessels, cells immunoreactive for S -100 protein and cartilagenous foci are scattered among proliferating lesion.

–   Endochondral ossification is a feature of maturing lesion. Only the absence of normal anatomical orientation differentiates this hetrotropic bone from normal. Otherwise it demonstrates all features of normal bone modeling (i.e., cortical & trabecular organization, medullary canal, metaphyseal funneling) and remodeling (i.e., respond to weight bearing stress, resistance to fatigue fracture)

– Bone morphogenetic protein – 4 (BMP – 4) is over expressed and Basic fibroblast growth factor which is an extremely potent stimulator of angiogenesis (in vivo) is elevated in urine during acute flare up stage.

Clinical features

In myositis ossificans progressiva, the life expectancy is decreased and the commonest causes of death is lung diseaseQ. This autosomal dominant disease is characterized by hetrotropic ossification most commonly involving spine and congenital defomities of hand &feetQ. The disease usually starts before 6 year of ageQ

Mortality in fibrodysplasia ossificans progressive (myositis ossificans progressiva) is usually related to restrictive lung disease caused by an inability of chest to expandQ.

–  Begins in childhood usually before age of 6 yearsQ and becomes evident with in first 10 years of life.

– Primary congenital skeletal abnormality is deformity of great toeQ. The toes may be short, in valgus, monophalangic or have abnormal shaped proximal phalanx.

– Begins as painful erythematous subfascial nodule mostly located on posterior aspect of neck & back which gradually calcify & eventually ossify (hetrotropic ossification)

–  The hetrotropic ossification progress in a axial to appendcular, cranial to caudal and proximal to distal direction. So the most commonly involved site is neck followed by spine & shoulder girdleQ. And same is the order for limitation of motion .

Trauma in form of tripping & falling, immunization, injection or biopsy stimulates new bouts of ossificationQ, and can be catastrophic.

– The ossification is irreversible, unlike other forms of hetrotropic ossification. This condition is quite different from myositis ossificans traumaticaQ.

– Diaphragm, extra ocular muscles & smooth muscles are characteristically sparedQ

Limitations of jaw mobility , extremely limited chest expnsionQ, reduced lung volumes 44% of normal) but relatively preserved flow rates and scoliosis / hypokyphosis are other feature Life expectancy is decreased and premature death usually result from respiratory failure Alt restrictive lung disease and their complicationsQ or from inanition caused by jaw ankylosis.


Q. 13 Myositis ossificans is differentiated from other reactive fibroblastic proliferations by the presence of:

September 2009

 A Dysplastic bone

 B

Dystrophic bone

 C

Metaplastic bone

 D

Hypertrophic bone

Ans. C

Explanation:

Ans. C: Metaplastic bone

Myositis ossificans usually develops in the athletic adolescents and young adults and follows an episode of trauma in more than 50% of cases.

The lesion typically arises in the musculature of proximal extremities.

It shows metaplastic bone.

It should be differentiated from extraskeletal osteosarcoma.


Q. 14 Osteosarcoma is differentiated from myositis ossificans by radiology by:

 A Location

 B

Absence of osteomyelitic changes

 C

Shape of swelling

 D

Peripheral field of differentiation

Ans. D

Explanation:

Ans. Peripheral field of differentiation


Q. 15

Most common site of myositis ossificans ‑

 A

Knee

 B

Elbow

 C

Shoulder

 D

Wrist

Ans. B

Explanation:

Ans. is ‘b’ i.e., Elbow

  • Myositis ossificans is the extraskeletal hetrotropic ossification that occurs in muscles and other soft tissues.
  •   Trauma is the most important cause of myositis ossificans.
  • Usually there is history of severe single injury.
  • It is more common in children.
  • Most commonly involved joint is elbow followed by hip.
  • There is history of trauma around the elbow, i.e. fracture supracondylar humerus, dislocation of elbow or surgery with extensive periosteal stripping.
  • Massage to the elbow and vigorous passive stretching to restore movements are aggravating factor.
  • It occurs in muscles which are vulnerable to tear under heavy loads, such as quadriceps, adductors, brachicilis, biceps, and deltoid.
  • X-ray finding is characteristic and shows distinct peripheral margin of mature ossification and a radiolucent center of immature osteoid & primitive mesenchymal tissue


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