Myositis Ossificans

Definition

 

Pathological bone formation in soft tissues

 

Epidemiology

 

In elbow

- 3% of trauma

- 89% if head injury + trauma

 

Types

 

Completely different

 

1.  Myosisitis Ossificans Circumscripta

- post traumatic

- more common

- recognised as a consequence of neurological injury

 

2.  Myositis (Fibrodysplasia) Ossificans Progressiva

- rare inherited condition

- progressive fibrosis of muscles, ligaments and tendons that is ultimately fatal

 

Classification

 

1. Traumatic 

 

Most common

- deltoid

- quadriceps

- elbow joint

 

Ankle Interossesous MO following high ankle sprainElbow Myositis OssificansMyositis Ossificans Quadriceps

 

2. Non-traumatic

 

Adductor tendon in horse riders

 

Aetiology

 

Unclear

 

Progression beyond normal healing to 0ssification

 

Typically single major traumatic incident

- direct blow to muscle

- joint dislocation ± fracture

 

Can occur with repeated minor trauma

- adductor Longus in horse riders

 

Pathology

 

2° muscle inflammation & repair process abnormal

- extensive cellular infiltration

- collagen laid down

- collagen undergoes dystrophic calcification

- chondroblasts differentiate into osteoblasts 

- osteoid produced

 

Clinical Features

 

History of trauma

 

Initial pain / swelling / warmth

 

Develop hard mass

- slow resolution of pain

 

X-ray

 

Changes occur 2-4 / 52 after injury

 

Initial cotton candy appearance

- then osseous in appearance

- not attached to bone

- can be resorbed

 

Mature bone peripherally

 

Myositis Ossificans Tibia LateralTibial Myositis Ossificans AP

 

DDx 

 

Osteosarcoma

STS

Hemangioma

 

MO

- diaphyseal (OS metaphyseal)

- intact cortex (OS fractures)

- mature bone peripheral with central fibrous tissue (OS mature centrally)

- pain and swelling improves with time (OS worsens)

- normal osteoblast on biopsy

 

Management

 

Prevention

 

High risk

- i.e. sports player with trauma to thigh / large haematoma

 

Minimise haemorrhage & inflammation

- ice & elevation

- active ROM / avoid passive ROM

- 3/52 course of NSAIDS

 

Resection

 

Indication

- large mass of bone

- significant pain, stiffness & weakness

 

Timing

- delayed > 12/12 (usually delay minimum 18 months)

- early resection = Recurrence

- don't resect until neurological recovery complete (i.e. if head injury)

 

Maturity

- local pain and tenderness resolved

- mature trabecular pattern on xray

- no progression on xray

- alkaline phos normal

- cold bone scan

 

Prognosis

- poor with in patient with incomplete neurological recovery and spasticity

 

Elbow MO PreoperativelyElbow MO Post resection

 

Myositis Ossificans Progressiva

 

Definition

 

Widespread ossification of connective tissue

 

Epidemiology

 

AD

 

Site

 

Spine

 

Major joints of upper limb

 

Histology

 

Poorly formed bone

Dense scar tissue

Islands of poorly formed cartilage

 

Clinical

 

Patients have short 1st metatarsal / metacarpal

 

Die of restrictive lung disease