Hip Dislocations

Posted by e-Medical PPT
Hip dislocations caused by significant force:
Association with other fractures
Damage to vascular supply to femoral head
Thus, high chance of complications

Anatomy of the Hip Joint
Ball and socket joint.
Femoral head: slightly asymmetric, forms 2/3 sphere.
Acetabulum: inverted “U” shaped articular surface.
Ligamentum teres, with artery to femoral head, passes through middle of inverted “U”.

Joint Contact Area
Throughout ROM:
 40% of femoral head is in contact with acetabular articular cartilage.
 10% of femoral head is in contact with labrum.
Acetabular Labrum
Strong fibrous ring
Increases femoral head coverage
Contributes to hip joint stability

Hip Joint Capsule
Extends from intertrochanteric ridge of proximal femur to bony perimeter of acetabulum
Has several thick bands of fibrous tissue
    Iliofemoral ligament
Upside-down “Y”
Blocks hip extension
Allows muscle relaxation with standing

Blood Supply to Femoral Head
1.Artery of Ligamentum Teres
Most important in children.
Its contribution decreases with age, and is probably insignificant in elderly patients.

2. Ascending Cervical Branches
Arise from ring at base of neck.
Ring is formed by branches of medial and lateral circumflex femoral arteries.
Penetrate capsule near its femoral attachment and ascend along neck.
Perforate bone just distal to articular cartilage.
Highly susceptible to injury with hip dislocation.

Hip Dislocation: Mechanism of Injury
Almost always due to high-energy trauma.
Most commonly involve unrestrained occupants in MVAs.
Can also occur in pedestrian-MVAs, falls from heights, industrial accidents and sporting injuries.

Posterior Dislocation
Generally results from axial load applied to femur, while hip is flexed.
Most commonly caused by impact of dashboard on knee.

Mechanism of Anterior Dislocation
Extreme abduction with external rotation of hip.
Anterior hip capsule is torn or avulsed.
Femoral head is levered out anteriorly.

Effect of Dislocation on Femoral Head Circulation
When capsule tears, ascending cervical branches are torn or stretched.
Artery of ligamentum teres is torn.
Some ascending cervical branches may remain kinked or compressed until the hip is reduced.
Thus, early reduction of the dislocated hip can improve blood flow to femoral head...

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