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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?....
8/13/2019 Myossitis Ossificans
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Defn: A benign tumour-likelesion characterized by osteoid
& heterotopic bone formationin soft tissues or even beneaththe periosteum.
8/13/2019 Myossitis Ossificans
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CLASSIFICATION
Post traumaticLocalised to softtissues affected bytraumaCommon 75%
CongenitalSoft tissues all over thebody involvedRare
Myositis ossificanstraumatica
Myositis ossificansprogressiva
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S YNONYMS - MYOSITIS OSSIFICANS TRAUMATICA
Pseudomalignant osseous tumourOssifying hematomaExtraosseous localised non-neoplastic bone &
cartilage formationLocalised myositis ossificans
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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
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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
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P ATHOPHSYSIOLOGY CONTD .
Peculiar alteration inground substance
of connectivetissue- proliferation
of mesenchymalcells & metaplasia
.Based on location-extraosseous , periosteal,parosteal
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P ATHOPHYSIOLOGY CONTD .
Degenerated & necrosedtissues are cleared off bymacrophages
Fibroblasts invade &proliferate(fibrosarcoma)
Sarcoplasmic nuclei proliferate& sarcoplasm productionincreases(only in ms)
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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
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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)
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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
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CLINICAL FEATURES CONTD .
Muscles commonly affected :Brachialis anticusQuadratus femoris
Adductors in thigh (Prussian disease)Deltoid
Joints involvedElbow AnkleKnee(Pellegrini Stieda disease)ShoulderHip
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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
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MY
O S I T I S
O S S I F I C AN
S
Myositisossificansin the
brachialismsanteriorly &in thetriceps msposteriorly .
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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