Why femoral neck fracture have a poor capacity of healing?

The femoral head obtains its blood supply from three sources:

1. Intramedullary vessels in the femoral neck

2. Ascending cervical branches of medial & lateral circumflex

3. Vessels of ligamentum artery

Why femoral neck fracture has high risk of avn?

Blood supply is interrupted due to tearing of capsular blood vessel

They have a poor capacity of healing because:

1. Main blood supply is interrupted due to tearing of capsular blood vessel

2. Difficult for callus formation à because intra- articular bone has only flimsy periosteum and has no contact with soft tissue

3. synovial fluid prevent blood clot for haematoma formation