MusculoskeletalOsteonecrosis & Osteochondrosis

Mohamed Zaitoun

Assistant Lecturer-Diagnostic Radiology Department , Zagazig University Hospitals

EgyptFINR (Fellowship of Interventional

Neuroradiology)-Switzerlandzaitoun82@gmail.com

Knowing as much as possible about your enemy precedes successful battle

and learning about the disease process precedes successful management

Osteonecrosis (Avascular Necrosis)a) Incidenceb) Etiologyc) Radiographic Featuresd) Special Types

a) Incidence :-Osteonecrosis (avascular necrosis, ischemic

necrosis, aseptic necrosis) may be caused by two mechanisms

1-Interruption of arterial supply2-Intra / extraosseous venous insufficiency-The pathophysiology of all osteonecrosis is the

same : ischemia → revascularization → repair → deformity → osteoarthrosis

b) Etiology :1-Trauma (fracture or dislocation)2-Dislocation 3-Collagen vascular disease4-Sickle cell disease5-Gaucher's disease6-Caisson disease7-Radiation 8-Pancreatitis, alcoholism9-Hormonal (steroids, Cushing's disease)10-Idiopathic (Legg-Calve-Perthes disease) 11-Pregnancy

c) Radiographic Features :1-Plain Radiography :-In general there is initial minor osteopaenia,

followed by variable density-Gradually microfractures accumulate in the dead

bone, which is unable to repair leading to collapse of the articular surface and the crescent sign of AVN

-Eventually the cortex collapses and fragments, with superimposed secondary degenerative change

Subchondral fracture (crescent sign)

2-MRI :-MRI is the most sensitive (95%) modality and

demonstrates changes well before plain film changes are visible

-The progression is:a) Diffuse edemab) Focal serpiginous low signal line with fatty center

(most common appearance)c) Double line sign on T2 is diagnosticd) Osteochondral fragmentation: rim signe) Secondary degenerative change•

*Osteonecrosis in brief :1-Kienbock disease : lunate2-Preiser’s Disease : scaphoid3-Legg-Calve-Perthes : femoral head4-Kohler’s Disease : navicular bone5-Frieberg's Disease : metatarsal head6-Kummel’s Disease : vertebral body

d) Special Types :(i) Upper Limb :1-Kienbock disease (Osteonecrosis of the

lunate) :-Sclerotic lunate on plain radiography-Sclerosis (low T1 and T2)

T1 T2

2-Preiser’s Disease : (Osteonecrosis of the scaphoid) :

-As before

(ii) Lower Limb :1-Legg-Calve-Perthes (Osteonecrosis of

femoral head) : school age (5-8 years) a) Incidenceb) Radiographic Features

a) Incidence :-Osteonecrosis of femoral head-School age (5-8 years)

b) Radiographic Features :-Plain film staging system (Ficat) :*Stage I : clinical symptoms of AVN but no

radiographic findings*Stage II : osteoporosis, cystic areas and

osteosclerosis*Stage III : translucent subcortical fracture line

(crescent sign) , flattening of femoral head*Stage IV : loss of bone contour with secondary

osteoarthritis  

Stage II

AP pelvic radiography showing flattening of the superolateral aspect (the weightbearing portion) of the right femoral head, there is a zone of decreased density representing the crescent sign, indicating subchondral fracture (stage III)

AP radiographic view of the pelvis shows flattening of the outer portion of the right femoral head from avascular necrosis, with adjacent joint space narrowing, juxta-articular sclerosis, and osteophytes representing degenerative joint disease (stage IV)

-Early signs :1-Asymmetrical femoral epiphyseal size

(smaller on affected side)2-Apparent increased density of the femoral

head epiphysis3-Widening of the medial joint space4-Blurring of the physeal plate

-Late signs :1-The femoral head begins to fragment with

subchondral lucency (crescent sign) 2-Femoral head deformity with widening and

flattening3-Osteoarthritis

Bilateral Perthes

Bilateral

2-MRI :-Earliest sign is bone marrow edema (nonspecific)-Early AVN : focal subchondral abnormalities (very

specific):Dark band on T1, bright band on T2Double-line sign (T2) : bright inner band / dark outer

band occurs later in disease process after the start of osseous repair (inner bright line representing granulation tissue and an outer dark line representing sclerotic bone)

-Late AVN : fibrosis of subchondral bone :Dark on T1 and T2Femoral head collapse

Bilateral AVN, (a) T1, (b) T2

T1 T2

-Mitchell classification :*Class A (early disease) : signal intensity

analogous to fat (high on T1 and intermediate on T2)

*Class B : signal intensity analogous to blood (high on T1 and T2)

*Class C : signal intensity analogous to fluid (low on T1 and high on T2)

*Class D (late disease) : signal intensity analogous to fibrous tissue (low on T1 and T2)

Coronal T1 of the pelvis in a patient with bilateral avascular necrosis of the femoral head shows increased signal within the superior aspect of the femoral head, representing fat, surrounded by a line of decresed signal, representing sclerotic reactive margin, this is an MRI class A (fatlike)

Patient 39 years old with use of high dose of corticosteroids, Cor T1 and T2 of the pelvis shows a stage B (blood-like) at the level of right femoral head with increased signal on T1W and T2W; AVN stage C (fluid-like) in left femoral head, with decreased signal intensity on T1W and increased signal on T2

Cor T1 and T2 in a patient with AVN on the left femoral head with decresed signal intensity on T1 and T2, representing a stage D (fibrous-like)

2-Kohler’s Disease (Osteonecrosis of the navicular bone) :

-As before

Normal navicular bone

3-Frieberg's Disease (Osteonecrosis of the Metatarsal head) :-Osteonecrosis of the distal end of the 2nd (75%) or 3rd (25%)

metatarsal-Bilateral in 10% of patients-The only osteonecrosis more frequent in females (75%)-Early :*Flattening and cystic lesions of the affected metatarsal head*Widening of the metatarsophalangeal (MTP) joint-Late :*Sclerosis and flattening of the bone-MRI : as before

(iii) Spine :-Kummel’s Disease (Osteonecrosis of the

vertebral body) :-Collapse of affected vertebrae

Osteochondrosis-Abnormal bone and cartilage at the end of bone-The term is a catch-all term referring to a

spectrum of diseases : a) Abnormal endochondral ossification

secondary to repeated stress without osteonecrosis :

1-Scheuermann's disease : spine2-Osgood-Schlatter disease : tibial tubercle3-Blount's disease : tibial epiphysis

b) Osteonecrosis disease :1-Kienbock disease : lunate2-Preiser’s Disease : scaphoid3-Legg-Calve-Perthes : femoral head4-Kohler’s Disease : navicular bone5-Frieberg's Disease : metatarsal head6-Kummel’s Disease : vertebral body

a) Abnormal endochondral ossification secondary to repeated stress without osteonecrosis :

1-Scheuermann's disease : spine2-Osgood-Schlatter disease : tibial tubercle3-Blount's disease : tibial epiphysis

1-Scheuermann Disease (Juvenile Kyphosis) (Vertebral apophyses) :

-Common condition which results in kyphosis of the thoracic or thoracolumbar spine

-Diagnostic criteria :*Thoracic spine kyphosis > 40 deg (normal 25-40

deg) or*Thoracolumbar spine kyphosis > 30 deg (normal 0

deg) and*At least 3 adjacent vertebrae demonstrating wedging

of > 5 degrees

-Plain Radiography :*Progressive narrowing of disk spaces*Wedging of the anterior portion of vertebral

bodies*Irregularity of endplates*Changes seen in >3 vertebral bodies*Multiple Schmorl's nodes

Wedge shaped vertebrae

2-Osgood-Schlatter Disease (Tibial tubercle) :-Secondary to repeated trauma to deep fibers of

patellar tendon-Male : female = 5 : 1-25% are bilateral-Irregular tibial tuberosity-Thickening of patellar tendon, soft tissue swelling

around patellar ligament

3-Blount’s Disease : (Congenital tibia vara), (Proximal medial tibial epiphysis)

-The tibial shaft is in varus position (Tibiofemoral angle > 15 degrees) and the epiphysis is wedge-shaped, fragmented or can appear absent

-The adjacent metaphysis is also depressed and has a beak-like protuberance of rarified bone oriented medially, this causes the metaphyseal diaphyseal angle (MDA) of Drennan to increase (typically more than 11 degrees)

b) Osteonecrosis disease :1-Kienbock disease : lunate2-Preiser’s Disease : scaphoid3-Legg-Calve-Perthes : femoral head4-Kohler’s Disease : navicular bone5-Frieberg's Disease : metatarsal head6-Kummel’s Disease : vertebral body-See before