Why is a traumatic hip dislocation typically worse than a shoulder dislocation

Why is a traumatic hip dislocation typically worse than a shoulder dislocation? Contrast the mechanisms which prevent the normal shoulder from dislocating with those of the hip joint, and consider what structures must be damaged when the joint comes out of place.

In brief, the shoulder is a loose joint: the humeral head held in place, adjacent to (but not technically “in”) the glenoid, by soft tissue, not bone. This arrangement allows for more range of motion yet less inherent stability. The hip is held in place, by contrast, via bony congruity: the femoral head sits within the acetabulum.

Conceptually, the hip is a “ball in socket” joint whereas the shoulder joint is more like a ball sitting on a golf tee.


These anatomical differences explain why a traumatic hip dislocation is typically worse than a shoulder dislocation:

  • A hip dislocation requires more force to get the joint out of place. And as a higher energy injury, a hip dislocation is more likely to be associated with other structural damage, such as a pelvic fracture or visceral injury (such as a urethral or bowel tear).

 

 

 

 

  • Because the shoulder has so much natural freedom, the soft tissues are not tethered tightly and typically have fairly wide excursion. Specifically, the axillary artery must naturally be allowed to move as such motion occurs during normal use of the arm. On the other hand, the femoral circumflex arteries on the femur ordinarily do no move much relative to the pelvis, and when a dislocation “demands” them to move, they are less able to comply. 

    As such, when the hip is dislocated, it is correspondingly more likely that the blood vessels (and nerves) are apt to be damaged.That said, a shoulder dislocation can, under the right (or should we say “wrong”) circumstances be associated with a neurovascular injury as well—it is just that there is more margin for error.

 

Attachments:

Copyright © 2012-2024 OrthopaedicsOne