Avascular Necrosis of the Femoral Head

Also known as: AVN, Osteonecrosis

Avascular necrosis, more accurately termed osteonecrosis of the femoral head, results from disruption of blood supply to subchondral bone.

Necrotic bone initially retains shape but cannot remodel normally under repetitive load. Subchondral fracture then develops, followed by femoral head collapse and secondary osteoarthritis.

Major causes include:

Corticosteroid exposure
Excessive alcohol use
Femoral neck fracture
Traumatic hip dislocation
Sickle cell disease
Systemic lupus erythematosus
Organ transplantation
Coagulopathy and thrombophilia
Gaucher disease
Dysbarism
HIV associated factors
Idiopathic disease

Nontraumatic disease is frequently bilateral. Both hips should therefore be assessed when one side is diagnosed.

Ficat and Arlet classification

Stage 0

No symptoms and normal imaging, usually historical concept only.

Stage I

Symptoms may be present
Plain radiographs normal
MRI or bone scan abnormal

Stage II

Sclerosis
Cysts
Focal osteopenia
No subchondral collapse

Stage III

Crescent sign
Subchondral fracture
Beginning collapse or flattening
Joint space remains relatively preserved

Stage IV

Advanced femoral head collapse
Joint space narrowing
Acetabular degenerative change
Secondary osteoarthritis

Revised ARCO classification

The current practical staging system is:

ARCO I

Radiographs normal
MRI demonstrates osteonecrosis

ARCO II

Radiographs show sclerosis, focal osteoporosis or cysts
No subchondral fracture or femoral head flattening

ARCO III

Subchondral fracture or collapse is present.

IIIA

Femoral head depression 2 mm or less

IIIB

Femoral head depression greater than 2 mm

ARCO IV

Secondary osteoarthritis with joint space narrowing and acetabular degeneration.

Lesion size

Stage alone does not determine prognosis.

The risk of collapse rises greatly when the necrotic segment:

Is large
Extends laterally into the weight bearing dome

Lesions involving more than approximately 30% of the femoral head and the lateral weight bearing surface have a particularly poor natural history.

Early disease may be asymptomatic.

Typical symptoms are:

Groin pain
Buttock pain
Anterior thigh pain
Pain with weight bearing
Reduced hip internal rotation
Limp

Pain can precede radiographic abnormalities.

Advanced collapse produces:

Rest pain
Night pain
Significant loss of hip movement
Shortening
Secondary osteoarthritis

Ask specifically about:

Current and previous corticosteroid dose
Alcohol exposure
Previous hip trauma
Sickle cell disease
Autoimmune disease
Organ transplantation

Treatment is determined primarily by:

Collapse versus precollapse
Lesion size
Lesion location
Age
Symptoms
Underlying cause

Risk factor modification

Where possible:

Minimise unnecessary corticosteroid exposure
Stop excessive alcohol consumption
Optimise sickle cell management
Treat metabolic and coagulation disorders where identified

Risk modification is important but does not reverse established structural necrosis.

Small asymptomatic lesion

A small medial non weight bearing lesion can be observed with:

Activity modification
Serial imaging
Clinical follow up

Not every MRI lesion requires surgery.

ARCO I and II

These are precollapse stages and therefore the main window for femoral head preservation.

Core decompression is the most established joint preserving operation.

The procedure:

Drills one large or multiple small channels into the necrotic segment
Reduces intraosseous pressure
Promotes revascularisation and bone repair

Best results occur with:

Early disease
Small lesions
No subchondral collapse

Core decompression alone is less reliable with large lateral lesions.

Biological augmentation

Core decompression may be combined with:

Bone marrow aspirate concentrate
Cancellous bone graft
Synthetic bone substitute

Current evidence suggests possible reduction in collapse with bone marrow augmentation compared with decompression alone, but the evidence remains limited and heterogeneous.

Bone grafting

Options include:

Nonvascularised bone graft

Provides structural and biological support.

Vascularised fibular graft

Provides:

Structural support
Vascularised bone
Potential revascularisation

It is technically demanding and most suitable for younger patients in specialist centres.

Osteotomy

Selected young patients with a medium sized necrotic lesion can undergo proximal femoral osteotomy to rotate intact cartilage into the major weight bearing zone.

This is technically demanding and can complicate later total hip arthroplasty.

It has a specialised rather than routine role.

ARCO III

Once subchondral fracture has developed, success of conventional decompression falls sharply.

Very early IIIA disease in a young patient may still be considered for advanced joint preserving reconstruction in specialist practice, but prognosis is significantly poorer than in stage I or II disease.

ARCO IIIB and IV

Established collapse and secondary arthritis are usually treated with total hip arthroplasty.

Do not persist with repeated decompression after major structural collapse.

Sickle cell disease

Sickle cell associated osteonecrosis often affects younger patients and can be bilateral.

Perioperative management requires:

Hydration
Oxygenation
Avoidance of hypothermia
Careful haematological planning
Appropriate transfusion strategy according to haemoglobin and sickling risk

Follow up

Monitor for:

Progressive collapse
Secondary osteoarthritis
Contralateral disease

Persistent increase in pain in a precollapse lesion should trigger repeat imaging rather than waiting for major radiographic deformity.

Clinical toolsCalculators

BMI GCS EDD Parkland Formula

Corrected Sodium Corrected Calcium Anion Gap Creatinine Clearance Insulin Calculations qSOFA Wells PE Wells DVT CHA₂DS₂-VASc HAS-BLED CURB-65 Centor/McIsaac

Pelvic Fracture

Pelvic fractures range from stable pubic ramus injuries to complete disruption of the pelvic ring with massive retroperitoneal haemorrhage.

A pelvic ring injury should be approached first as a potential haemorrhagic emergency, not merely an orthopaedic fracture.

Major bleeding sources include:

Presacral and pelvic venous plexus
Exposed cancellous bone
Internal iliac arterial branches

The retroperitoneum can contain several litres of blood.

Associated injuries frequently involve:

Bladder
Urethra
Rectum
Vagina
Abdominal viscera
Spine
Major nerves

Tile classification

Based on mechanical stability.

Type A: Stable

Posterior arch remains stable.

Avulsion or fracture not significantly involving pelvic ring stability.

Stable or minimally displaced pelvic ring fracture.

Transverse sacral fracture.

Type B: Rotationally unstable, vertically stable

Open book injury.

Lateral compression injury.

B2.1 typically involves ipsilateral anterior ring injury.

B2.2 may produce a contralateral bucket handle pattern.

Bilateral rotational instability.

Type C: Rotationally and vertically unstable

Unilateral complete instability.

Subclassified according to posterior lesion through:

Ilium
SI joint
Sacrum

Bilateral injury with one side type C and the opposite side type B.

Bilateral complete instability.

Young Burgess classification

Based on force direction.

Anterior posterior compression

APC I

Symphyseal widening below approximately 2.5 cm
Posterior SI ligaments intact
Usually mechanically stable or minimally unstable

APC II

Symphyseal widening greater than approximately 2.5 cm
Anterior SI joint opening
Sacrospinous and sacrotuberous ligament disruption
Posterior SI ligaments intact

Rotationally unstable but vertically stable.

APC III

Complete anterior and posterior SI ligament disruption
Complete hemipelvic instability
High haemorrhage risk

Lateral compression

LC I

Pubic ramus fracture
Ipsilateral sacral compression fracture

Most common pelvic ring pattern.

LC II

Rami injury plus posterior iliac crescent fracture through the SI complex

LC III

Ipsilateral lateral compression with contralateral external rotation injury

Called a windswept pelvis.

Vertical shear

Vertical displacement of one hemipelvis with complete posterior ligament disruption.

Severely unstable and associated with major bleeding and neurological injury.

Denis sacral zones

Useful when the posterior injury passes through the sacrum.

Zone I

Lateral to neural foramina.

Lowest neurological risk.

Zone II

Through neural foramina.

Risk of radicular injury.

Zone III

Central sacral canal.

Highest risk of cauda equina, bowel and bladder dysfunction.

Follow major trauma resuscitation principles.

Inspect for:

Pelvic deformity
Perineal bruising
Scrotal or labial haematoma
Rectal bleeding
Vaginal bleeding
Open wounds
Leg length discrepancy
Neurological deficit

Do not repeatedly spring or compress the pelvis after an unstable injury has been identified because repeated manipulation can disrupt clot.

Look for urethral injury:

Blood at urethral meatus
Inability to void
Perineal haematoma
High risk pelvic ring pattern

Perform retrograde urethrography before blind catheterisation when urethral disruption is suspected.

Open pelvic fractures involving rectum or perineum have extremely high septic and haemorrhagic morbidity.

Haemorrhage control

In an unstable pelvic ring injury, apply a pelvic binder over the greater trochanters, not around the iliac crests.

The binder:

Reduces pelvic volume in APC injury
Improves tamponade
Stabilises fracture surfaces

Initiate balanced haemostatic resuscitation when major bleeding is present.

A practical massive transfusion strategy uses approximately:

Packed red cells : plasma : platelets in a 1 : 1 : 1 ratio during active uncontrolled haemorrhage.

Correct:

Hypothermia
Acidosis
Hypocalcaemia
Coagulopathy

Persistent haemodynamic instability requires rapid haemorrhage control.

Options include:

Preperitoneal pelvic packing
External pelvic fixation or pelvic C clamp where appropriate
Angiography with arterial embolisation

These are complementary rather than competing techniques.

Angioembolisation is particularly effective when CT or ongoing physiology suggests arterial bleeding.

Preperitoneal packing rapidly controls predominantly venous and cancellous bleeding and is valuable in an unstable patient requiring immediate operative control.

Temporary mechanical stabilisation

APC injuries can be stabilised using:

Binder
Anterior external fixator
Pelvic C clamp in selected posterior instability

Vertical shear may require:

Skeletal traction
Temporary external fixation
Definitive posterior fixation

Stable pelvic fracture

Tile A and many LC I injuries can be managed nonoperatively.

Provide analgesia and mobilise early with protected weight bearing according to pain and stability.

Prolonged bed rest should be avoided.

Operative indications

Fixation is appropriate for:

APC II and III instability
Vertical shear
Tile C fracture
Displaced crescent fracture
Symptomatic unstable posterior ring injury
Progressive displacement
Open unstable pelvic fracture
Selected LC injuries demonstrating instability under stress

Posterior ring

Posterior stability is critical.

Options include:

Percutaneous iliosacral screws
Transsacral screws
Posterior plating
Lumbopelvic fixation for severe spinopelvic dissociation

Careful preoperative CT assessment is mandatory because sacral dysmorphism alters safe screw corridors.

Anterior ring

Options include:

Symphyseal plate
Ramus screw
External fixation

In vertically unstable injuries, anterior fixation alone is inadequate. The posterior ring must also be stabilised.

Open pelvic fracture

Urgently address:

Haemorrhage
Faecal contamination
Urinary injury
Devitalised perineal tissue
Unstable bone

Broad antimicrobial coverage is required when rectal or gross perineal contamination exists, for example:

Piperacillin tazobactam 4.5 g IV every 8 hours by extended infusion, renal adjusted.

Perform repeated debridement as necessary.

Faecal diversion is considered with:

Rectal injury
Massive perineal contamination
Destructive anorectal injury

It is not mandatory for every open pelvic wound.

VTE prophylaxis

Pelvic fracture carries high venous thromboembolism risk.

Begin pharmacological prophylaxis once haemostasis is secure and bleeding risk is acceptable.

A commonly used regimen is:

Enoxaparin 40 mg subcutaneously once daily, with adjustment for renal function, body weight and local trauma protocol.

Major complications include:

Fatal haemorrhage
DVT or pulmonary embolism
Pelvic sepsis
Neurological injury
Chronic pelvic pain
Sexual dysfunction
Urological dysfunction
Malunion
Leg length discrepancy

Avascular Necrosis of the Femoral Head

Overview

Clinical Features

Diagnosis

Management

Overview

Clinical Features

Diagnosis

Management