THE HIP JOINT :

The hip joint comprises of a long thigh bone articulated with cup shaped cavity of hip bone.Rounded head of the thigh bone fits into the cavity to from a ball and socket joint.

The surface of the head of the thigh bone and the socket are covered by specialised tissue called articular cartilage.

The joint cavity is lined by a membrane called the synovium which secretes synovial fluid into the joint and allows smooth movement of the ball within the socket.

PROSTHESIS OF HIP JOINT :

The doctor will decide about the best material to be used in your particular case. This selection will depend upon factors such as –

• You’re age
• Normal level of Activity
• Degree of damage
• Deterioration of bones of your Hip Joint

Although a replaced hip joint may continue to function successfully for 15 yrs. or more, it will not last forever. Careful consideration is therefore necessary before replacing the hip of someone in their forties or fifties, as they are likely to require revision surgery in future. In such conditions cementless prosthesis may be most appropriate.

Femoral Component :

Femoral component prosthesis replace the head of the femur. It contains ball shaped head & a stem which is inserted into the shaft of femur.

Femoral component is made of a variety of metals

• Stem :
  • Cemented Stem : Cemented Stem is made from steel, titanium & titanium alloys and is highly polished. It is fixed with the help of cement in femoral shaft.
  • Uncemented Stem : Uncemented Stem is coated with Hydroxyapatite or is porous coated. It fixes into femoral shaft. These allow bone to grow onto their surface.
• Head :
  Head is fixed on neck of stem & acetabulum component. It is made of any one of the following metals. –
  • Cobalt Chrome : It is a very strong alloy having high resistance to wear & corrosion.
  • Oxidized Zirconium : It is toughest metal known today. It is also having high resistance to wear & corrosion.
  • Ceramic : Ceramic cornponents are brittle but hard which do not scatter easily, are durable & have low friction. These are particularly good in young active people.
• Acetabular Component :
  • Uncemented : It consists of a shell & a liner. The shell is made of titanium alloy, which allow bone to grow easily onto its surface. These have good press fit design. The liner is made of highly cross linked polyethylene and has very good wear properties.
    Ceramic liners are also available, and are durable & have low friction.
  • Cemented : Cemented components are made of highly cross linked polyethylene and have very good wear properties.