Anatomy

Femoral neck fractures are intracapsular and may threaten any or all of the three sources of blood to the femoral head:

• the cervical vessels in the retinaculum of the joint capsule - usually damaged if the fracture is displaced
• intramedullary vessels - always torn
• from the ligamentum teres - usually contributes minimally in the elderly and not uncommonly, may be non-existent

In addition to the damage to the blood supply, the intracapsular nature of the fracture hinders recovery from the injury:

• intra-articular bone has only a thin periosteum and has no contact with soft tissues - the response to injury - callus formation - is weak
• blood remains inside the joint capsule, increasing intracapsular pressure and further damaging the femoral head; synovial fluid hinders clotting