Myositis Ossificans

extra-osseous non neoplastic growth of new bone Misnomer

Heterotopic ossification

not always inflammatory

within extra-skeletal soft tissues – mainly in connective tissue than muscle

Ectopic Calcification ?!!Deposition of radio dense

Calcium PhosphateDifference in mineral phaseNo true bone matrix is formed Eg:- Hyper/Hypoparathyroidism,

Renal failure, Following TB, Calcific Supraspinatus Tendinopathy,

Scleroderma, Dermatomyositis

Diffuse cutaneous, subcutaneous and muscular calcification:

Calcinosis universalis in

Dermatomyositis

Types Myositis ossificans

circumscripta /traumatica

fibrodysplasia ossificans progressiva (FOP)

Myositis ossificans circumscripta /traumatica

In response to soft tissue injury:- blunt trauma, stab wound, fracture/dislocation, surgical incision (THR)

Systemic Conditions:- Head injury,Spinal cord injuryTetanus, Burns

Without known injury:-

Nondocumented trauma,

Repeated small mechanical injuries(blunt trauma in horse riders)

Nonmechanical injuries caused by ischemia or inflammation.

Increased risk in patients with Diffuse Idiopathic Skeletal Hyperostosis (DISH) and Paget’s Disease

Pathophysiology

BMP stimulate primitive stem cells in soft tissues to form osteoblasts

Organization of Haematoma

Fibroblastic hypoplasia

Osteoid formation

Radiographic evidence in 6-8 weeks

The lesion begins to calcify at the periphery and works toward the center (Reverse in Osteosarcoma)

Histopath- 4 distinct zones:the central undifferentiated zone- mitotically

active the surrounding zone of immature osteoid

formation – less activezone with new bone – osteoblast & fibrous

tissue with trabecular organizationPeripheral zone of fibrous tissue

At least 10 days are required following onset of symptoms for these zones to become apparent.

drug abusers elbow ?!!

Paraspinal

most commonly in the second and third decade

Areas commonly affected - elbow, thigh, buttocks, shoulder and calf ., erector spinae, pectoralis muscles(Quadriceps and brachialis - most affected.)

Majority –asymptomatic; may cause pain/ loss of ROM  

presents as a rapid enlargement and significant pain one to two weeks after injury.

Swelling and warmth at the site

Hypercalcemia- contributing factor

Increased ESR and serum alkaline phosphatase.

TreatmentWatchful inactivityRest and gentle stretching.

Surgery if persistent pain – excised in toto in mature cases

Risk of recurrence +

If left alone, the mass will shrink in size

Treatmentshould not continue to play sports or use the

affected muscle.

Avoid Heat and massage. Reinjury to the same area, returning to activity too

early, or initial passive forceful stretching can lengthen recovery.

Prophylaxis: NSAIDS(Indomethacin), low dose radiation

Heterotopic Ossification Osteosarcoma

Site: Diaphysis MetaphysisPeripheral rimming Ossification center

(can mimic necrotic tr) to periphery Improvement in pain over Pain worsens with time and

rest timeBiopsy:Zone phenomenon Undiff tissue- viable muscle

fibres similar to central intact cortex zone

Myositis Ossificans Progressiva / Fibrodysplasia Ossificans Progressiva

rare autosomal dominant disorder skeletal malformation and progressive, disabling

heterotopic osteogenesis.

fibrosing and ossification of muscle, tendon and ligaments of multiple sites often in the upper extremities and back that is disabling and ultimately fatal

Nine-year-old Mexican girl with Fibrodysplasia Ossificans Progressiva (FOP).

Chromosome 2q23-24 Heterozygous mutation (617G®R206H) in the

glycine-serine (GS) domain of the

Activin A receptor type I (ACVR1) gene, a bone morphogenic protein (BMP) type I receptor

Incidence 1in 2 millionAge: Average 5 yrs (Fetus-25 yrs)Their offspring have a 50% probability of

inheriting the condition.

painful lumps and stiffness in the adjoining joint. Lumps decrease in a few weeks, but joint

mobility reduction persists.

Exacerbating factors for ossifications at new sites

minor trauma, venipuncture,

biopsy of lumps, IM injections,

dental treatments, and excision of masses.

Most common sites:- sternocleidomastoid, paraspinal muscles, the masticatory muscles, shoulder and pelvic girdle muscles.

Spared are the abdominal muscles, extraocular muscles, muscles of facial expression, diaphragm, larynx and tongue muscles.

Ossification progresses from proximal to distal

and cranial to caudal.

C/FDigits: Short hallux in valgus with synostosis

short thumbs , ClinodactylyFibrous Tissues: Swelling in aponeuroses,

fasciae, and tendons- ossification in muscles and fibrous tissues, most prominent in the neck dorsal trunk and

proximal extremities (The sternocleidomastoid muscle is commonly affected.)

Kyphoscoliosis: Restricted shoulder and pelvic girdle movements

LabHemogram, ESR, S.Ca, P:- WNLECG findings may be abnormalspirometry :-restrictive pattern, reflective of chest

wall involvement.

Plain radiography of FOP

Short metacarpals and metatarsals Phalangeal synostosis (eg, monophalangeal great

toe) Vertebral fusions, vertebral anomalies (i.e., small

bodies), pedicle thickening Thick, short femoral neck Variations in bone maturation sequence Increased incidence of enchondromas

TreatmentOnce diagnosis is established, usually clinically,

any surgical biopsy is contraindicated in FOP.

No established medical therapy exists.

Pain medications

supportive measures -gentle occupational and/or physical therapy.

Prevention is better!!

avoid falling or getting bruises

avoid IM injections since these can cause bone to grow.

Never stretch their joints outside of their normal ROM.

Flare-ups can occur spontaneously, even perfect preventive care cannot guarantee the absence of bone growths.

The mainstay of diagnosis is bilateral great toe anomaly present from birth, reported in 79 to 100% of patients

microdactyly of both halluces due to a single phalanx in valgus position

The finding of congenital hallux valgus must raise the possibility of FOP so that management should be early and adequate.