myossitis ossificans

8/13/2019 Myossitis Ossificans

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What is it?• Myo-muscle

Itis-inflammation

Ossificans-ossificationBUT MYOSITIS OSSIFICANS DOESN’T IMPLY MS

INFLAMMATION!!Then what is it?....



Defn: A benign tumour-likelesion characterized by osteoid

& heterotopic bone formationin soft tissues or even beneaththe periosteum.



CLASSIFICATION

Post traumaticLocalised to softtissues affected bytraumaCommon 75%

CongenitalSoft tissues all over thebody involvedRare

Myositis ossificanstraumatica

Myositis ossificansprogressiva



S YNONYMS - MYOSITIS OSSIFICANS TRAUMATICA

Pseudomalignant osseous tumourOssifying hematomaExtraosseous localised non-neoplastic bone &

cartilage formationLocalised myositis ossificans



M YOSITIS OSSIFICANS TRAUMATICA

CAUSES :

• 1. Trauma• - simple blow (contusion)•

-dislocation (injury duringreduction)• - avulsion (periosteal

stripping in children)• Fracture-short period of

immobilisation

• 2. Massage: Immediatelyafter injury, spread ofhematoma

Hematoma& periosteal

strippingdue to



P ATHOPHYSIOLOGY Structures involved -

muscles ,ligaments,tendons, fascia, periosteum

Zone phenomena (Ackermann)

1. Central highly cellular- fibroblasts highly mitotic2. Fibroelastic tissue3. Mature well oriented bone



P ATHOPHSYSIOLOGY CONTD .

Peculiar alteration inground substance

of connectivetissue- proliferation

of mesenchymalcells & metaplasia

.Based on location-extraosseous , periosteal,parosteal



P ATHOPHYSIOLOGY CONTD .

Degenerated & necrosedtissues are cleared off bymacrophages

Fibroblasts invade &proliferate(fibrosarcoma)

Sarcoplasmic nuclei proliferate& sarcoplasm productionincreases(only in ms)



P ATHOPHYSIOLOGY CONTD .

Cluster of nuclei in sarcoplasmic mass(giant cell tumour or myosarcoma)

Ground substance-hyaline changeand encloses mesenchymal cells

Mesenchymal cells show metaplasia

to form osteoblasts

Mineralisation and bone formation



This process begins at the periphery & graduallyprogresses toward the centre. Hence zonephenomenon.

Ossification may disappear by osteoclasticresorption

When myositis ossificans is not removed it getscovered by a cartilagenous cap due to ms action(post traumatic osteochondroma)



Acute stage- painswelling tenderness.

Active & passive movtpainful

Later -pain reduces &well circumscribed

indurated painlessmass

Stretching of msdifficult-inelasticity &

ms action difficult-obstruction

Hard mass maypersist or undergocomplete regression

or post traumatic

osteochondroma

Clinicalfeatures



CLINICAL FEATURES CONTD .

Muscles commonly affected :Brachialis anticusQuadratus femoris

Adductors in thigh (Prussian disease)Deltoid

Joints involvedElbow AnkleKnee(Pellegrini Stieda disease)ShoulderHip



MYOSITIS OSSIFICANS PROGRESSIVA

o Rare congenital condition evident in childhoodassociated with disorders like Microdactyly,Brachydactyly, Klippel Feil etc.

o Starts as solitary firm mass in upper back(trapezius,lattissimus dorsi) but later other masses in softtissues all over body

o Ossification takes place months or years latero IP joints of foot & thumb as well as joints of spine

may fuseo Only lab finding – raised ESR



MY

O S I T I S

O S S I F I C AN

S

Myositisossificansin the

brachialismsanteriorly &in thetriceps msposteriorly .



MY

O S I T I S

O S S S I F I C AT I ON

RE C URRE N

C E A

F T E R

S X Z

A.Involvementof brachialis ms5 m afterdislocation ofelbow

B.Osseousmass wasexcised 9 mlater.microscopically bone wasmature

C.Large mass ofmyositisossificans inbrachialis



THANK YOU !

myossitis ossificans

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