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Total Hip Replacement

Osteoarthritis of the hip joint occurs very commonly 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 head of the femur (thigh bone) and replacing it with a stemmed femoral prosthesis and replacing the worn out socket (acetabulum) with an acetabular shell and liner.

Even though 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 patient’s expectations, particularly if there have been complications.

There are several important factors that can lead to a less stressful and a smoother recovery. These include the following.

Preoperative Patient Education

At the time of the consultation the patient will be given a full explanation of what is involved in the joint replacement procedure, expected recovery period and eventual outcome. 

If there are any concerns or questions, which arise for patients after the consultation, the staff at KOG welcome calls from patients to clarify any of these issues. If the issues require further explanation a further consultation with the surgeon is encouraged. 

The patient will be asked to attend a pre-operative education session at Knox Private Hospital, which is conducted by experienced nurses and physiotherapists. If the patient is aware of what is going to happen to them, they are usually less fearful and anxious about the procedure. This increased knowledge has been shown to reduce postoperative pain and lead to a less stressful recovery.

Multimodal Anaesthesia and Analgesia

This involves the use of a spinal anaesthetic combined with the insertion of local anaesthetic in the wound at the end of the procedure. Postoperatively the patients are given a regular cocktail of different pain killers along with anti-inflammatory medication. These medications dramatically reduce the occurrence 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

The majority of patients will be asked to walk with assistance on the same day as the operation 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. Becoming mobile early reduces the risk of complications such as calf thrombosis and respiratory problems.

Inpatient Stay

The procedure is usually done under a spinal anaesthetic, although patients may be sedated during the operation and many patients have minimal recollection of the procedure itself. The operation takes approximately one 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 and foot pumps will be applied to the feet. This improves the blood flow through the legs, and both of these measures as well as Aspirin or other blood thinners, 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 patients are encouraged to discard these once they are able to walk comfortably without a significant limp.

The length of the stay in hospital varies according to the patient’s postoperative progress. There is a significant variation from one patient to the next following this major procedure. Some patients will be able to go home as early as the third post-operative day while older patients who live alone may need to go to a rehabilitation hospital prior to going home.

Patients are reviewed in the consulting rooms at six weeks postoperatively and it is usual for most patients to be walking very well at that stage with minimal or 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 was a problem ten to twenty years ago.  This is now uncommon due to the excellent ingrowth of bone into the newer prostheses.

Acetabular Prosthesis

The socket component consists of two parts. A titanium shell is inserted into the pelvic socket. To encourage bone growth into the shell, it has been designed with a roughened surface. A modular liner is then placed into the shell. There are several different materials that may be used, and this will depend on the patient’s age and activity level.

Femoral Prosthesis

A tapered cementless titanium stem is inserted into the femur bone. This also has a roughened textured surface to allow bone ingrowth into the prosthesis. In older patients with softer bone the femoral prosthesis may be inserted with bone cement.

A modular head is then inserted on top of the stem.

Bearing Surfaces

There are three alternative bearing surfaces available:

Metal on Polyethylene

This is the traditional material, which has been used for many years. There have been significant improvements in the polyethylene over the last ten to fifteen years. Ultra cross-linking of the polyethylene molecules has dramatically reduced its wear and this has allowed for larger ball heads to be used. With larger heads the risk of hip dislocation has been shown to be significantly reduced. The Australian Joint Registry has demonstrated a significant reduction in the revision rate using this newer polyethylene.

Metal On Metal

A metal on metal bearing surface became popular in the 1980s and 90s when treating younger active patients with hip replacement surgery. The reason this was chosen was that the wear rate of most metal on metal articulations was very low and it was hoped that this would last thirty or more years. 

Metal on metal bearings were used both with standard hip replacements as well as is with hip resurfacing. The first modern hip resurfacing was called the Birmingham hip prosthesis and the results for many patients continue to be excellent. 

In 2001 an alternative hip resurfacing called the ASR was used but within seven years the Australian Joint Registry noted that there was a much higher revision rate with this prosthesis. This high revision rate was the result of a faulty design of the ASR and it led to excessive wear of the metal surfaces and subsequent damage to the surrounding bone and soft tissues. This, along with some delayed hypersensitivity reactions to metal on metal articulations, has led to a dramatic decline in the use of this metal on metal bearing surface. 

No surgeons at KOG have used the ASR prosthesis and none of the surgeons continue to recommend this form of articulation.

Ceramic on Ceramic

This bearing surface has a very low wear rate. It is also a very bio-inert substance, in that the small amount of wear debris does not seem to cause any significant reaction 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 component. If this occurs, it requires urgent revision of the articulating surfaces. In approximately 10 to 15% of cases there is an audible sound 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

Hip replacement surgery is a major stress on the body, and if there are pre-existing medical conditions, 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 on the day of 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 even 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 can be taken to minimise this complication.

Leg Length Discrepancy

Every endeavour 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. It 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 revision of the hip replacement.

There are 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.

Images supplied courtesy of Zimmer ©  Zimmer.