Hip Replacement

Osteoarthritis of the hip joint is very commonly seen in our community and often leads to severe pain, stiffness and disability. Total hip replacement has revolutionised the treatment of this condition and results in excellent relief of pain and restoration of mobility in a very high percentage of cases.

The procedure involves removal of the worn out femoral head and replacing it with a stemmed femoral prosthesis and replacing the worn out socket (acetabulum) with an acetabular shell and liner.

The decision about having hip replacement is yours but Mr Dunin will discuss the pros and cons of surgery to help you make that informed decision. Please do not hesitate to discuss any of your concerns about having surgery. Sometimes it is wise to make another appointment if you have further questions that arise out of the initial consultation. Whilst over 95% of patients are extremely happy with the outcome after joint replacement surgery, there is a small percentage of patients where the outcome is below the patients expectations, particularly if there has been complications.

Over the last 5 years there has been a growing trend to perform hip joint replacement surgery through smaller and smaller incisions. A number of different approaches to the hip have been used. Initial studies, particularly from the USA, showed patients being discharged from hospital within 2 days and walking unaided within a very short period of time. Since then, several controlled studies have shown that the length of the incision is only a small factor in decreasing the length of stay and the time taken to recover from hip replacement surgery. Click here to visit our AMIS page for further information regarding minimally invasive total hip replacement.

There are several other important factors which can lead to a shorter length of stay with less pain and these include the following:

Preoperative Patient Education

The patient is aware of what is going to happen, they are usually less fearful and anxious. This has shown to reduce postop pain.

Multimodal Anaesthesia and Analgesia

This involves the use of a spinal anaesthetic combined with local anaesthetic in the wound. Postoperatively the patients are given a regular cocktail of different pain killers combined with anti-inflammatory medication. This has been shown to dramatically reduce the incidence of severe pain postoperatively. It is not uncommon for many patients to state that they have had little or no pain after hip replacement surgery with this regime.

Early Mobilisation

Day 1 with full weight bearing. Some patients are fearful about walking so early after surgery, however it is quite safe to do so and the patient will be assisted by physiotherapy and nursing staff. Getting going early, in fact, reduces the risk of complications such as calf thrombosis.

Inpatient Stay

The procedure is usually done under a spinal anaesthetic, although you will be sedated during the operation and many patients have minimal recollection of the procedure itself. The operation takes approximately 1 hour and is done through a small incision of less than 10cm. Local anaesthetic is introduced into the wound at the end of the procedure.

Postoperatively below-knee stockings will be fitted, as well as foot pumps applied to the foot. This improves the blood flow through the leg, and both of these measures as well as Aspirin, reduce the risk of blood clots.

Most patients are surprised by how little pain they have after the operation, although some wound discomfort is to be expected. In addition, there will be some swelling in the thigh which may last several weeks. Walking aids such as crutches or a frame will be used initially, but I encourage my patients to discard their walking aids once they are able to walk comfortably without a significant limp.

The length of the stay varies according to your postoperative progress, and length of stay varies considerably from one patient to the next, with some patients being able to go home on the third postoperative day, whereas older patients that live on their own may well need to go to a rehabilitation hospital prior to going home.

Patients are reviewed in my consulting rooms at 6 weeks postoperatively and it is usual for most patients to be walking very well at that stage with minimal to no limp. Return to full activities can be expected somewhere around 2 to 3 months postoperatively.

Type of Prosthesis

There are several different materials used in a total hip replacement. The risk of loosening of the prosthesis, which used to be a problem 10 to 20 years ago, is now uncommon due to the excellent ingrowth of bone into the prostheses.

Acetabular Prosthesis

The socket component consists of two parts, a titanium shell is inserted into the pelvic socket which has a roughened surface to encourage bone growth into it. A modular liner is then placed into the shell. There are several different materials that can be used, and this will depend on the patients age and activity level.

Femoral Prosthesis

A tapered cementless titanium stem is inserted into the femur bone. Once again it has a roughened textured surface to allow bone ingrowth into the prosthesis. A modular head is then inserted on top of the stem and the type that will be used will be that which is appropriate for the acetabular bearing surface.

Bearing Surfaces

There are three alternative bearing surfaces available:

1. Metal on Polyethylene

This is the traditional material which has been used for many years. There has been significant improvements in the polyethylene over the last 5 years. Ultra crossed linking of the molecules has dramatically reduced the wear of the polyethylene and this has allowed for larger ball heads to be used. With larger balled heads the risk of hip dislocation has been shown to be significantly reduced.

2. Metal On Metal

This is often used in younger patients. In fact, it was one of the earliest forms of hip replacement used, but fell into disfavour because the early prototypes were not very well made and often would cause excessive wear or loosening. However, there is now a resurgence of metal on metal articulations. The wear rate is dramatically less than metal on polyethylene, however the number of particles generated is in fact higher.

It is the form of articulation used with hip resurfacing. There is increased level of cobalt and chromium in the blood of patients who have had metal on metal articulations. So far there is no evidence that this causes any deleterious effect in the long term on the body. It is however recommended that it not be used in patients with renal disease, as the cobalt and chrome released in the joint are cleared by the kidneys. There is a small incidence of delayed hypersensitivity to the metal on metal articulatation and this appears to be a little more frequent in females. Excessive wear of the metal on metal articulation can occur if the acetabular component is not placed in the optimum position.

3. Ceramic on Ceramic

This also has a very low wear rate, like metal on metal. It is also a very bioinert substance, in that the wear debris does not seem to cause significant problem either locally or elsewhere in the body. It is however somewhat brittle in structure, and there is a small but definite incidence of fracture of the ceramic. If this occurs it requires urgent revision of the articulating surfaces. In approximately 1 to 2% of cases there is an audible squeak that can develop within the first year of surgery, and this can be quite disconcerting to the patient.

Potential Complications Following Total Hip Replacement

Systemic Complications

These can occur in the postoperative period. Hip replacement surgery is a major stress on the body, and if there is pre-existing medical condition, the following complications may occur:

  • Heart attack
  • Stroke
  • Pneumonia
  • Short Term Confusion

Local Complications

Blood Clots (The medical term for these is Deep Venous Thrombosis)

Measures are taken to minimise this complication, including the wearing of stockings and foot pumps to improve blood flow in the legs. Aspirin or Heparin is used to thin the blood. In addition, patients are mobilised the following day after the operation. Whilst these measures significantly reduce the risk of deep venous thrombosis this condition can still occasionally occur, sometimes the blood clots can travel to the lungs and cause a pulmonary embolus which can have quite serious consequences including death.

Infection

Superficial infection is an uncommon complication that usually responds well to antibiotics. A deeper infection is much less common, but can have serious long term consequences. It sometimes requires further surgery and prolonged high powered antibiotics.

Dislocation

Sometimes the ball and socket joint can dislocate which would cause acute pain and the inability to walk. The hip can usually be put back in place by manipulation without the need for open surgery. It is more common in the first few weeks postoperatively and there are precautions that you can take to minimise this complication.

Leg Length Discrepancy

Every endeavor is made to maintain the legs at equal leg length, however, sometimes the leg can be slightly lengthened as a result of the hip replacement. This may require the use of a shoe raise in the opposite shoe.

Nerve Injury

This is a rare complication of hip replacement but can lead to weakness or altered feeling in the foot and ankle. It usually improves but can be permanent.

Loosening of the Hip Replacement

This is discussed more fully in revision hip surgery - see below.

Revision Hip Surgery

Over 95% of patients who have a hip replacement have excellent relief of pain and improved mobility. Most patients never require a re-do of the hip replacement.

There is however, a small percentage of patients who do require revision surgery because of excessive wear of the ball and socket joint or loosening of the prosthesis. This may cause pain and a limp, and the diagnosis can be confirmed with x-rays. Excessive wear of the ball and socket joint is one of the most common reasons why revision hip surgery is performed.


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