Hip Replacement

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