Knee Replacement

What:

  • Knee replacement,
    or knee arthroplasty,
    is a surgical procedure to
    replace the weight-bearing surfaces of
    the knee joint.
  • A round ended implant is used for the femur,
    mimicking the natural shape of the joint.
  • The tibia component is flat,
    it sometimes has a stem
    which goes down inside the bone for further stability.
  • A flattened or slightly dished
    high density polyethylene surface is
    inserted onto the tibial component,
    so that the weight is transferred metal to plastic not metal to metal.
  • The articular surface of the patella is removed and replaced by a polyethylene button cemented to the posterior surface of the patella.

Why:

  • To relieve pain and disability.

How:

  • The surgery consists of
    replacing the diseased or damaged joint surfaces of the knee
    with metal and plastic components
    shaped to allow continued motion of the knee.
  • During the operation
    deformities must be corrected,
    and the ligaments balanced
    so that the knee has a good range of movement
    and is stable and aligned.
  • The operation involves substantial postoperative pain,
    and includes vigorous physical rehabilitation.
  • The recovery period may be
    6 weeks or longer
    and may involve the use of mobility aids,
    such as walking frames, canes, and crutches,
    to enable the return to preoperative mobility.

Algorithm:

  • Expose the front of the knee,
    detach part of the quadriceps muscle, aka vastus medialis, from the patella.
  • The patella is displaced
    to one side of the joint,
    allowing exposure of
    the distal end of the femur and
    the proximal end of the tibia.
  • The ends of these bones are then accurately cut to shape
    using cutting guides
    oriented to the long axis of the bones.
  • The cartilages and the anterior cruciate ligament are removed;
    the posterior cruciate ligament may also be removed
    but the tibial and fibular collateral ligaments are preserved.
  • Metal components are impacted onto the bone
    or fixed using
    polymethylmethacrylate (PMMA) cement.

//end//

Knee Replacement