Total hip replacement

From greek.doctor
  • Joint prosthesis
    • They are used to replace damaged joints
  • Total hip replacement (THR)
    • Surgical technique
      • The acetabulum is opened and reamed (hollowed out)
        • This removes any residual cartilage and leaves only the bony surface
      • The neck of the femur is cut with a saw
      • The medullary cavity is reamed to make space for the femoral stem
      • If bone cement is used, bone cement is applied to the medullary cavity of the femur and the acetabulum to fix the femoral stem and the acetabular parts, respectively
      • If bone cement is not used the femoral stem and acetabular parts are banged in
    • Components
      • Acetabular component
        • Polyethylene insert or liner
          • A special kind of plastic
          • Provides the mobile part of the joint
        • Acetabular shell
          • Made of metal
      • Femoral head
      • Femoral stem – goes into medullary canal of femur
    • Types
      • Cemented THR
        • Both femoral component and acetabular component are fixed to the bone with bone cement
        • Bone cement dries after 15 minutes, meaning that the prosthesis can (in theory) be walked on and used immediately after the procedure
          • However, no patient can walk immediately after any major surgery
        • Bone cement is created by mixing a powder with a solution -> then applied with a cement gun
        • The bone cement will enter the lacunae of the bone, fixing the prosthesis to the bone
      • Uncemented THR
        • Does not use bone cement – instead, the prosthesis is fixed by force
          • This is called “press fit”
        • The acetabular part is banged into the acetabulum
        • The femoral stem is banged into the medullary cavity of the femur
        • The prosthesis has a porous coating and the bony part is rough, which creates a lot of friction between the prosthesis and the bone
          • This is called primary fixation
          • If the friction itself is not enough the prosthesis can be further fixed with screws
        • After some weeks the bone will grow into the porous surface of the prosthesis
          • This is called secondary or final fixation
          • This takes time, and the patient must not be weightbearing during this time
    • Indications
      • Cemented THR
        • For elderly
        • For less active patients
        • For those with poor bone quality
      • Uncemented THR
        • For young, active patients
        • For those with good bone quality