HIP SURGERY

Surgery at the Wellington

Total Hip Replacement

Why is it done?
Most total hip replacements are performed because of degeneration of the hip joint. The most common cause of this degeneration is osteoarthritis as a result of the normal aging process. Abnormal wear and tear resulting from previous fractures or an underlying congenital defect may also cause osteoarthritis. A condition known as avascular necrosis, in which the head of the femur loses its blood supply, may also necessitate a hip replacement.

How is it done?
Through an incision over the hip joint, the head and neck of the thigh bone (femur) are removed and an angled shaft with a smooth ball on the end is inserted into the bone. The socket part of the hip (acetabulum) is smoothed out and an artificial socket fitted.

There are a number of different bearing types in artificial hip joints. The one that is most widely used consists of a metal (normally cobalt-chrome alloy or stainless steel) ball and a plastic (polyethylene) socket, but wholly metal or ceramic replacements can also used in some cases.

Most types of joint are fixed into position with special acrylic bone cement. Others are designed in a way which encourages the patient’s own bone to grow into them and hold them in place.

The type of implant to be used will be decided by your surgeon, based on his professional experience and taking into account a number of factors including your age, level of activity and health.

What can go wrong?
Complications can occur with any major surgical procedure. The medical team in charge of your care will discuss these fully with you before your operation. Some specific complications following hip replacement are:

Deep vein thrombosis, caused by blood clots forming in the leg veins. In some cases this can lead to a pulmonary embolism (a clot breaking off and getting stuck in the lung). The risk of DVT is reduced by pressure stockings, medication to thin the blood and by getting the patient moving as soon as possible after the operation.

Infection is a rare but serious complication of hip surgery. Antibiotics will normally be given before and after the operation to lessen the risk.

Dislocation, where the ball comes out of the socket, is more likely to happen to a replacement hip than a natural one. You will be given advice on how to reduce this risk.

Loosening of the new hip joint may occur over time. The life-span of a hip replacement can vary enormously, according to the type of implant and the age and lifestyle of the patient. On average, about 10% of patients will eventually need a second operation in their lifetime.

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Minimally Invasive Total Hip Replacement

Two-incision THR is a technique developed over the last 5 years in the US that involves placing a standard uncemented total hip replacement through two smaller incisions. The socket is placed through a small incision in the groin and the stem is placed through a small incision in the buttock. The advantages are:

  • Shorter hospital stay and faster rehabilitation (day case surgery has been achieved in the US and UK)
  • Decreased pain
  • Greater patient satisfaction
  • Improved cosmetic appearance
  • Use of standard implants with an established track record
  • Use of xray during the procedure ensures accurate positioning of implant

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Hip Arthroscopy

Why is it done?
Arthroscopy (keyhole surgery) can be used to diagnose, evaluate and treat certain hip problems. Some of the most common of these are:

  • Loose fragments of cartilage or bone in the joint, caused by trauma or the early stages of arthritis
  • Tears in the labrum, the special cartilage which surrounds the acetabulum (hip socket)
  • Inflammation of the synovial membrane (synovitis)

How is it done?
Under anaesthetic, traction is applied to the hip to open up the joint. Two or more very small incisions are made through which a miniature camera (arthroscope) and specially designed surgical instruments can be inserted into the joint. The surgeon can then get an accurate picture of what is going on in the hip and make small repairs if appropriate. Saline solution is pumped into the joint during the procedure to help the surgeon to see more clearly and to wash out any debris.

What are the advantages?
This minimally-invasive procedure is preferable to open hip surgery for some relatively minor problems. It can usually be performed on an out-patient basis and post-operative pain is greatly reduced.

What are the disadvantages? Arthroscopy is not suitable for patients with severe osteoarthritis or for those who have had previous open hip surgery.

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Revision Hip Replacement

Why is it done?
Despite considerable advances in technology, artificial hip joints do not last forever. A significant percentage will wear out or loosen within the patient’s lifetime and a further operation will become necessary. Because the success of revision surgery is directly related to the quality and quantity of remaining natural bone, the earlier a problem is identified the better the potential outcome will be. Regular, routine follow-up, combined with x-rays, can spot problems beginning to happen before the patient experiences symptoms. Revision in these cases can be relatively straightforward. Unfortunately, many “failed” hip replacements only come to light at a much later stage when a fracture or dislocation occurs. This poses a greater challenge for the surgeon as a complex revision is called for. In relatively rare cases, replacement hips become infected and this may also require a second operation.

How is it done?
When a hip replacement is revised, one or both parts of the original implant must first be removed. If the amount of healthy bone is adequate to provide anchorage, the surgeon will then fit new prostheses. In cases where bone loss is severe, bone grafts or specially designed components will be required.

Why is it more difficult and less successful than the first time?
Because the old implant has to be removed as well as the new one fitted, revision operations are generally longer than first-time ones. A larger incision may also be required. This can result in greater blood loss and a higher level of post-operative pain. Patients having revision surgery are also that much older, having enjoyed their first hip replacement for many years. Long term results are excellent with modern revision implants, although complications are slightly less infrequent.

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Hip Resurfacing

Why is it done?
For younger, more active patients, total hip replacement may not offer the best solution to their osteoarthritis. Traditional hip implants can wear over time and loosen, necessitating difficult revision surgery in later life. Moreover, the active lifestyle which these younger patients are keen to resume may itself increase the wear and tear on the implant and accelerate the loosening process. Hip resurfacing may be the better option in these circumstances.

How is it done?
In this procedure, rather than removing the head and neck of the femur and replacing them with a prosthesis, the head of the femur (the “ball” part of the joint) is trimmed and fitted with a round metal cap. The socket is then lined with a metal cup. The body’s own fluid provides lubrication between the two surfaces.

What are the advantages?
Because less bone is removed, any further surgery, which might be required later in life, should be less complex. The operation also carries a lower risk of subsequent dislocation, thus allowing the patient to continue to undertake more vigorous activity such as skiing.

What are the disadvantages?
In its current form, this procedure has only been in use since 1997, so long-term results are not yet available. However, medium-term results look extremely promising. Because of a small risk of femoral neck fractures after hip resurfacing, the operation is not suitable for patients with or at risk of osteoporosis.

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Hip Replacements for Younger Patients

The first successful hip replacement for osteoarthritis was performed in the 1960s and since then the procedure has been one of the greatest success stories of modern medicine, relieving pain and disability and vastly improving the quality of life for millions of patients. However, despite considerable technical advances over the years, the limited life-span of a metal-on-plastic hip replacement has been a barrier to surgical treatment for younger patients.

In the traditional, most widely used implant, the socket component is made of high grade polyethylene. Over time, the normal wear of the metal ball on this surface causes the release of microscopic particles into the joint. The body’s natural defence system is unable to differentiate between these particles and invading bacteria and an inflammatory response occurs which gradually erodes the healthy bone around the implant and causes it to become loose. This process is accelerated by the level of activity expected in younger patients, increasing the failure rate of hip replacement in this group.

Fortunately, recent developments in “hard on hard” implants (either metal-on-metal or ceramic-on-ceramic), which produce much smaller volumes of wear particles, have made hip replacement surgery for younger and more active patients a feasible option.

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Periacetabular Osteotomy

Why is it done?
This operation is used to correct a condition known as Acetabular Dysplasia, a congenital defect of the acetabulum (the hip socket) in which the socket is shallower and more upward-sloping than normal. Sometimes there may be deformity of the upper femur as well. In severe cases, this defect may be detected at or soon after birth, but in its milder form it often goes unrecognised until adulthood when symptoms, particularly pain, start to appear. Left untreated, arthritis can develop, due to the abnormal stress on the joint.

How is it done?
In this procedure, the surgeon cuts around the acetabulum (the hip socket) and rotates it so that it covers the head of the femur better. Screws are used to hold the bone in place while the natural healing process occurs. In cases where there is also abnormality of the femoral head (the ball part of the joint), a femoral osteotomy may be performed to improve its shape.

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