The diagnosis of osteoarthritis is made on history, physical examination & X-rays
There is no blood test to diagnose Osteoarthritis (wear & tear arthritis)
Total Hip Replacement – Pre-opTotal Hip Replacement – Post Op
You are admitted to the hospital and after appropriate pre-operative tests and admission procedures you will be taken to the operating theatre. The anaesthetist will discuss with you the type of anaesthetic. Anaesthesia may be either general or regional. With a general anaesthetic you are asleep and with a regional (spinal or epidural) your legs and hips are numb allowing you to have the operation without pain. Usually the anaesthetist will either sedate you or give you a full anaesthetic if you have a spinal/epidural procedure.
Most approaches to the hip are done with the patients lying on their side. When you are asleep you are positioned in a special brace that stabilises your pelvis and keeps you on your side. An incision is made along the side of your hip joint and the muscles carefully split and divided to expose the hip joint.
The worn out joint is exposed and the femoral head is resected. This allows visualisation of the acetabulum (socket). The socket is then cleared of debris and a reamer is inserted to appropriately fashion the socket to accept the artificial acetabular component.
After reaming is complete, the artificial socket is inserted. There are two types of sockets, (a) a cemented socket or (b) an uncemented socket. A cemented socket is cemented into the bone and an uncemented socket allows bone to grow into it. Your surgeon will advise you which is the most appropriate socket for your bone quality.
An uncemented socket has the ability to accept a socket lining which is either polyethylene (special plastic), ceramic or metal. The liner is inserted into the socket. Ceramic and metal articulating joint surfaces have lower wear rates than plastic sockets and therefore tend to be used in younger patients. The newer plastics last a lot longer than the older ones and are appropriately used in older patients.
After preparation of the socket, the femoral bone is prepared with various instruments to accept either a cemented or an uncemented femoral component. Once the canal is prepared the femoral stem is inserted with or without cement. A trial femoral head is placed on the stem and the hip is reduced. During the trial reduction the hip is tensioned appropriately and put through a range of motion. At the same time leg lengths and stability are examined.
Following the trial reduction the appropriate head is then placed on the stem and the hip is reduced. Occasionally leg lengths may not be entirely equal in order to tension the hip appropriately and thereby prevent dislocation.
Following insertion of the components the wound is closed usually with absorbable sutures and a drain is inserted.
What about the bearing (articulating) surface?
When the first hip replacements were made 35 years ago, it was found that over time they started to wear out and loosen. The reason they wore out was that fine plastic (polyethylene) particles were released from the socket which caused a small inflammatory response. This inflammatory response around the prosthesis caused the bone to weaken and the prosthesis to loosen and therefore a revision was needed. Occasionally these inflammatory areas can become large cysts and structurally weaken the bone so that when the hips are revised extra bone is required to fill up these defects. This extra bone may be taken from the patient or may be allograft bone, which is bone that has come from a bone bank.
In order to reduce the amount of wear particles, newer technologies have evolved. This includes new polyethylene, ceramic on ceramic and metal on metal articulations. The wear rates of ceramic on ceramic and metal on metal are 10 to 100 times less than the original plastic material.
Newer technology surfaces are tested in a laboratory on hip and knee simulators. The tests are extremely encouraging but only time will tell if they prove to be as successful as laboratory tests show. Younger patients tend to have ceramic or metal articulations in the expectation that less wear will occur and the joint will last longer.