Bone Necrosis Flashcards
What is Osteochondritis
localised necrosis of bone due to underlying ischaemia from a reduction in blood supply - caused by increased repetitive stress (compression or traction).
Age group most commonly affected by osteochondritis
children and young adults
Pathophysiology of osteochondritis
recurrent impact or traction injuries causes bleeding and oedema in bone, resulting in capillary compression. This leads to necrosis and separation of bone.
Freiburg’s disease
Osteochondritis of the 2nd metatarsal head
Kohler’s disease
Osteochondritis of the navicular bone
Keinbock’s disease
Osteochondritis of the lunate bone
Panner’s disease
Osteochondritis of the capitellum of the elbow
Scheuermann’s disease
Osteochondritis in the spine causing vertebral compression
Osgood-Schlatter disease
Traction osteochondritis at the tibial tubercle where the tendon attaches
Sever’s disease
Traction osteochondritis at the calcaneus where the tendon attaches
Osteochondritis dissecans
Fragmentation with separation of bone and cartilage within a joint
Sites predisposed to osteochondritis dissecans
Lateral part of medial femoral condyle
Anteromedial talar dome
Superomedial femoral head
Humeral capitellum
Presentation of osteochondritis dissecans
Pain
Effusions
Locking
Giving way of the weight bearing joint
Tx of compression types of osteochondritis
Restriction of activities is usually enough
splintage in the wrist or foot
Tx of traction types of osteochondritis
self limiting & settles with rest
Tx of osteochondritis dissecans
surgical pinning of fragments
removal of detached fragments
Sites most prone to AVN
femoral head femoral condyles head of humerus capitellum proximal pole of scaphoid proximal part of talus
Age group most commonly affected by AVN
adults
Causes of AVN
Alcohol Steroid abuse Idiopathic Secondary to fractures Thrombophilia Sickle cell disease Antiphospholipid syndrome Caisson's disease
Why do alcohol and steroid abuse cause AVN
They alter metabolisation of fat - gets into circulatory capillaries and sludges them up and promotes coagulation. Increased fat content in the marrow compresses venous outflow causing stasis.
Why does Caisson’s disease cause AVN
This is decompression sickness.
Nitrogen gas bubbles form in the circulation after to fast decompression from deep sea diving.
AVN appearance on xray
patchy sclerosis
subchondral collapse
irregular articular surfaces
secondary OA changes
Tx of AVN
Depends on stage of disease
Early -
if articular surface has not collapsed,
drilling under fluoroscopy to decompress the bone
Late -
if articular surface has collapsed,
joint replacement
What is osteomyelitis
infection of the bone including compact and spongy bone, and bone marrow
How do the organisms causing osteomyelitis infect bone
Directly - penetrating trauma, surgery
Indirectly - haematogenous spread from an infection or bacteraemia at distant site
Patients most susceptible to osteomyelitis
Immunocompromised
patients with chronic disease
elderly
young
Pathogenesis of osteomyelitis
Once infection is present in the bone, enzymes from leukocytes cause local osteolysis and pus forms which impairs local blood flow
What is a sequestrum
A dead fragment of bone which forms in osteomyelitis that usually breaks off
What is the consequence of a sequestrum being present in osteomyelitis
It means that antibiotics alone will not cure infection
What is an involucrum
New bone formation around the area of necrosis in osteomyelitis
What is a Brodie’s abcess
A subacute steomyelitis found in children, which presents insidiously and where the bone reacts by walling off the abscess with a thin rim of sclerotic bone
Why are children at risk of osteomyelitis
The emtaphyses of lone bones contain abundant tortuous vessels with sluggish flwo that can result in the acucmulation of bacteria, and infection spreads towards the epiphysis
Most common bones in adults affected by osteomyelitis
Axial skeleton (spine and pelvis)
Most common sources of infection for osteomyelitis in adults
Pulmonary infections (incl TB)
Urinary infections
Discitis
Previous open fracture or internal fixation
Most common causative organism for osteomyelitis
Staph. aureus
Tx acute osteomyelitis
“best guess” IV Abx (usually high dose fluclox)
Tx chronic osteomyelitis
Surgery to access deep bone tissue, remove any sequestrum and excise infected bone
Predisposing conditions to osteomyelitis
Diabetes mellitus Sickle cell anaemia IVDU Immunosuppression Alcohol
Ix for osteomyelitis
MRI
