Wednesday, 13 April 2016

Total Hip Replacement

Total Hip Replacement is an operation to remove the acetabulum and femoral head of the hip joint to implant a ball and socket prosthesis to function as a moveable joint as a replacement. Total Hip Replacement is called Arthroplasty.

In a well-functioning hip joint both the acetabulum and the femoral head are lined with surface cartilage, or what is called articular cartilage. This surface layer of cartilage is encapsulated by synovial fluid which acts as a lubricant to assist joint movement. The cartilage acts as a shock absorber and smoothens the roll of the joint and under normal circumstances lasts a lifetime.

When the depletion of cartilage exposes bone to friction, chemical reactions and inflammation occur to degenerate the condition of the cartilage further. The mechanical wear caused by bone on bone friction is the primary condition of osteoarthritis and the source of the associated swelling and pain. 

The prosthesis used in Total Hip Replacement comes in two sections. The upper thighbone, (femoral head), implant is generally made of a metal or ceramic ball attached to a splint inserted into the top of the bone. The socket half of the implant is made of ceramic or a special plastic called polyethylene. Due to the acetabulum being concaved the implant is surrounded by bone surface to adhere to.

As to how the implants are affixed, two standard types of total replacement methods exist. There is the cemented method and the cement-less. The cement used to affix implants to bone is called methyl methacrylate. The cement-less method however uses microscopically porous materials to allow the bone to grow into and adhere to the implant.   

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