Hip Replacement

clipDoc:

What:

• An orthopedic surgical procedure
  to replace the hip joint
  with a prosthetic implant.

Why:

• To relieve pain and disability.
• Total hip replacement treats joint failure caused by
  osteoarthritis,
  rheumatoid arthritis,
  avascular necrosis,
  traumatic arthritis,
  protrusio acetabuli,
  certain hip fractures,
  benign and malignant bone tumors.

How:

• There are several incisions, defined by their relation to the gluteus medius.
• There is no compelling evidence
  in the literature
  for any particular approach,
  but consensus of professional opinion favors either
  modified anterolateral
  or posterior approach.

The prosthetic implant in hip replacement consists of three parts:

the acetabular cup,
the femoral stem, and
the articular interface.

Algorithm:

Acetabular cup/shell:

• Cartilage and bone are removed from the acetabulum
  and the acetabular cup is attached
  using friction or cement.
• The cup is made of metal,
  the outside has a porous coating,
• there are two types of porous coating
  used to form a friction fit,
• sintered beads or
• a foam metal design
  to mimic the trabeculae of cancellous bone,
• initial stability is influenced by under-reaming and insertion force,
  the inside contains a locking mechanism designed to accept a liner.
• Permanent fixation is achieved as
  bone grows onto or
  into the porous coating.
• Screws can be used to lag the shell
  to the bone providing even more fixation.
• Polyethylene liners are placed into the shell and connected by a rim locking mechanism,
  ceramic and metal liners are attached with a Morse taper.

Femoral component:

• The femoral component is the component that fits in the femur (thigh bone).
• Bone is removed
  and the femur is shaped to accept
  the femoral stem
  and attached prosthetic femoral head (ball).
• Stems are made of multiple materials,
  titanium, cobalt chromium,
  stainless steel, and polymer composites,
  and they can be
  monolithic or modular.
• Femoral heads are made of
  metal or ceramic material.

Articular interface:

• The articular interface is not actually part of either implant,
  it is the area between the
  acetabular cup and femoral component.
• The articular interface of the hip is
  a simple ball and socket joint.

//end hip replacement//
Hip Replacement