Prosthetic hip dislocation (dislocation after total hip replacement)

Prosthetic hip dislocation (dislocation after total hip replacement):
The hip joint is a ball-and-socket joint. The ball, at the top of the femur is called the femoral head.
The socket, called the acetabulum, is a part of the pelvis.
A total hip replacement means the ball of the hip and the socket of the hip joint are both replaced.
the dislocation after total hip replacement is a complication usually occurring due to patient noncomplicance with post-operative precautions,
implant malposition,
or soft-tissue deficiency.
Up to 3% of people who have had a total hip replacement will experience a dislocation
with 70% occur within first month when the soft tissues are still healing,
and 75-90% being posterior dislocations.
This type of dislocation normally caused by minimal trauma,
usually falls or turning,
moving into the contra-indicated positions, and putting stress on the capsule that was incised for the replacement surgery.
Significant risk factors mechanically predisposing individuals with total hip replacement to dislocation include:
prior hip surgery (greatest risk factor),
advanced age (older than 75 years),
female sex,
prior spinal fusion,
alcohol or drug abuse,
spastic or neuromuscular disease, such as Parkinson’s,
cognitive dysfunction, such as dementia or Alzheimer’s disease,
Polyethylene wear, a common cause of late instability occurring 5 years after surgery.
Dislocation of a THA is not a subtle phenomenon.
Patients will typically experience a significant "pop" or "clunk" with immediate pain.
There is often shortening and rotation of the affected limb
typically, external rotation with anterior dislocation;
internal rotation with posterior dislocation.
Weightbearing is usually not possible.
Dislocation can be diagnosed with plain radiography of the hip.
Most patients with an early dislocation, however, can be treated with a simple closed reduction under sedation or anesthesia.
the orthopedic surgeon will pull on the leg to reposition the hip within the socket.
X-rays will be obtained to ensure the hip is repositioned.
Following closed reduction, strict dislocation precautions are usually recommended based on the direction of dislocation.
Occasionally, a hip abduction brace is used to reinforce dislocation precautions.
For dislocations related to implant failure,
implant malalignment,
excessive soft tissue laxity,
recurrent instability,
or If closed reduction is unsuccessful,
surgical treatment is often necessary.
Surgical options include exchange of modular components
or trochanteric advancement to increase soft-tissue tension,
or revision arthroplasty with use of constrained liners,
or using elevated rim liners
or using dual mobility implants.
The dual mobility cup features two articulations:
a small articulation between the femoral head and the mobile bearing
which is where most of the movement occurs
and a large articulation between the mobile bearing and the acetabular component.
A success rate of 80 percent can be expected for reoperations in which the specific cause of the dislocation has been well defined.
The highest reported success rates have been with constrained acetabular components
or the use of a dual mobility construct.

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