Total Hip Replacement
Total hip replacement is one of the treatment options for hip arthritis. Read below to learn more about hip arthritis and whether you would benefit from hip replacement surgery.
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What causes hip arthritis?
The hip joint is made up of a ball (the head of the femur) that fits into a socket in the pelvis (acetabulum). A healthy hip joint is lined by a specialised, smooth, low-friction (articular) cartilage which allows the joint to move smoothly and freely. Hip arthritis occurs when this specialised cartilage degenerates or wears out, and the underlying bone becomes exposed.
There are two main causes for the specialised cartilage in the hip joint to degenerate:
- Osteoarthritis is the most common cause of hip arthritis. Osteoarthritis may run in families, determined by genetics, however it may also occur as a result of injury, trauma or previous surgery. An impaired blood supply to the hip joint may cause collapse of the head of the femur. More rarely, a childhood disorder of the hip may lead to early-onset osteoarthritis.
- Inflammatory arthritis is an immune disorder that leads to inflammation in the (synovial) lining of the hip joint. Common causes are auto-immune disorders such as rheumatoid arthritis. The synovial lining becomes inflamed and thickened with the production of various damaging molecules in the joint. This in turn leads to damage of the specialised articular cartilage. Rheumatologists treat inflammatory arthritis with medications that target the damaging molecules.
What are the symptoms of hip arthritis?
- Pain. The most common locations for pain from hip arthritis is in the groin, in the thigh and even down to the knee. Pain on the outside of the hip or in the buttock is less characteristic of hip arthritis and may be due to another condition, such as trochanteric bursitis or lumbar spine arthritis. Pain that shoots down the leg is rarely caused by hip arthritis.
- Stiffness. Hip arthritis can cause a reduced range of motion in the hip joint. This is usually something that develops slowly over time and may be worse in the morning or with inactivity.
- Limp. Hip arthritis may lead to a limp and the need to use a walking stick or walking frame for balance.
- Functional limitations. Pain, stiffness and a limp may lead to every day functional limitations. This may be a reduction in exercise or walking distance over time. More specifically, it may be uncomfortable to sit on low chairs or toilets, or to sit in a car for prolonged periods. It may be difficult to stand after being seated. Putting on or taking off shoes and socks, and cutting toenails, may be a problem.
How is hip arthritis diagnosed?
Hip arthritis is best diagnosed by your treating doctor. A combination of your history, physical examination and an x-ray is usually enough to determine whether the hip joint is arthritic.
The hip joint will usually have a painful limitation in range of motion and may impinge in certain positions. An x-ray may show the space in the hip joint to be narrowed with bony deformity.
Rarely, an MRI may be needed to determine if the articular cartilage in the hip joint is damaged.
Blood tests are used to diagnose the different inflammatory causes of hip arthritis.
What are the non-surgical treatments for hip arthritis?
There are a multitude of suggested treatments for osteoarthritis, but be careful, not all treatments are supported by the best medical evidence.
The treatments for osteoarthritis with strong supporting evidence in the medical literature include:
- Exercise – referral to a physiotherapist or exercise physiologist may be beneficial.
- Weight loss – for those patients with a body mass index (BMI) greater than 25, a weight loss target of 5-10% of body weight is recommended. Referral to a dietician or upper gastrointestinal surgeon may be beneficial.
Other treatments, that may help, where the medical evidence is less clear, include:
- Cognitive behavioural therapy
- Stationary cycling
- Aquatic exercises (hydrotherapy)
- Massage therapy
- Manual therapy such as stretching
- Heat therapy
- Aids such as walking sticks and frames
- Transcutanous electrical nerve stimulation (TENS)
- Oral anti-inflammatory medications (NSAIDs)
- Corticosteroid injections
Interventions with evidence against use for hip or knee arthritis treatment include opioid medications, viscosupplementation injections, stem cell therapy, glucosamine, chondroitin and omega-3 fatty acid supplements.
What are the surgical options for hip arthritis?
The best surgical option for treating hip arthritis is usually a total hip replacement.
Total hip replacement involves completely replacing the arthritic ball and socket joint with an artificial joint (prosthesis).
Rarely, a joint preservation procedure may be possible. This surgery is performed only in specialised centres and involves realigning the hip joint with an osteotomy (cutting the bone) of the pelvis or femur, to offload the arthritic area.
What is a total hip replacement?
Total hip replacement is a surgical procedure that replaces the arthritic hip joint with an artificial joint (prosthesis). The main goals of total hip replacement are pain relief, improved mobility and quality of life. Total hip replacement is one of the most successful surgical procedures performed in the world today and was named by The Lancet as the “operation of the century” in 2007.
Common reasons for undergoing total hip replacement include:
- Severe pain
- Reduced mobility and independence
- Difficulty performing job due to pain and stiffness
- Inability to enjoy recreational activities due to pain and stiffness
- Pain at night that interrupts sleep
459,265 primary total hip replacements have been performed in Australia since 1999. The ball (head of the femur) is removed and replaced with a femoral component that is fixed inside the femoral canal. The femoral component has a new ball on top. The arthritic socket of the hip joint is also replaced with a metal acetabular component. A liner is inserted into the acetabular component. The ball of the femoral component moves inside the liner of the acetabular component.
What is hip resurfacing?
Hip resurfacing is an alternative to total hip replacement. Rather than removing the arthritic head of the femur completely, the surface of femoral head is covered with a metal cap.
The bone of the femoral neck is largely preserved, and the prosthesis does not need to be placed in the femoral canal. The arthritic socket of the hip joint is replaced in a similar way to a total hip replacement.
The metal cap on the femoral head moves inside the metal acetabular component. The potential benefits of hip resurfacing are preserved bone, improved range of motion and increased stability of the resurfaced joint.
Not all patients are suitable for hip resurfacing. The procedure is largely limited to male patients under the age of 55 with a larger body frame and good bone quality.
What is a minimally invasive direct anterior approach, and posterior approach?
There are different ways or “approaches” to perform a total hip replacement. Irrespective of the approach used, total hip replacement can offer long-term pain relief and improved quality of life. The most common approaches used today are the “posterior approach” and the “direct anterior approach”.
The posterior approach is the most common approach utilised in Australia today. The arthritic hip joint is exposed through the back of the joint. The posterior approach requires the large gluteus maximus muscle to be split and the detachment of some short external rotator muscles from the femur. It is generally a more invasive approach.
The minimally invasive direct anterior approach is a muscle-sparing approach that exposes the arthritic hip joint from the front. The anterior approach utilises the hip’s natural intermuscular planes, going between muscles, rather than cutting through muscles. Due to the less invasive and muscle-sparing nature of this approach, patients may experience a quicker short-term recovery and return to usual level of activity.
The medical literature suggests that this benefit is limited to the first 6-12 months. In the longer term, however, there is no functional difference between the two approaches and the long term outcomes are the same.
In 2019, the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) reported on approaches in total hip replacement for the first time. This was based on data from hip replacements performed in Australia between 2015 – 2019.
The primary finding was that there was no difference in overall rate of early revision between posterior approach and direct anterior approach.
However, when revisions were required, the reason for revision was different between approaches. Posterior approach total hip replacements were more commonly revised for infection and dislocation, while anterior approach total hip replacements were more commonly revised for loosening or fracture.
What is a hip replacement made of and how is it fixed in place?
There are many different designs of total hip replacement prostheses.
The main differences between prostheses are the way in which the prosthesis is fixed to the bone and the prosthesis bearing surfaces.
Hip replacement prostheses may be classified as:
- Uncemented – both femoral and acetabular components rely on a tight fit for initial bone fixation. The bone grows onto the components for long term fixation.
- Hybrid – the femoral component is fixed inside the femur with bone cement and the acetabular component relies on bone growth for fixation.
- Cemented – both the femoral and acetabular components are fixed in place with bone cement.
The Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) provides some guidance on how to choose a particular prosthesis for a particular patient. Generally speaking, for patients over the age of 65, a hybrid total hip replacement has the lowest revision rate. Uncemented prostheses may be used for younger patients. The best prosthesis choice is determined for each individual patient.
The bearing surfaces are the femoral head and the acetabular liner. These may be made from metal alloy, ceramic or polyethylene (plastic). The most commonly used bearing surfaces are metal alloy heads and polyethylene liners. Ceramic heads and liners may be used in younger patients. Metal on metal hip prostheses (with the exception of hip resurfacing) are not currently used.
How long will the hip replacement last?
In 2019, the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) reported the overall revision rate of primary total hip replacement as 11.7% at 18 years after surgery.
How long does it take to recover after a hip replacement?
Whilst every patient has a different starting point prior to hip replacement, relief from arthritic hip pain is usually very rapid. Patients are encouraged to walk almost immediately following surgery under the supervision of a physiotherapist. It takes approximately 2 weeks for the skin wound to be well healed and it may be wet after that.
Hip replacement patients will have returned to driving a car by 6 weeks. After a rapid improvement in the first three months, progress will start to plateau, and you will return to normal activity levels. Depending on the approach taken for a hip replacement there may be restrictions in positioning for three months.
Hip precautions are taken for posterior approach total hip replacement. There are less restrictions for anterior approach total hip replacement.
What are the main risks of hip replacement surgery?
Deep venous thrombosis (DVT). A blood clot may form in the leg after surgery. This has the potential to propagate or break off, travelling to lung. This is potentially life threatening. Medications can be used to reduce the risk of DVT. Other things that you can do to prevent clots include remaining well hydrated, wearing TED stockings and mechanical calf pumps immediately after the operation. Also, moving around and walking early after surgery will lower your risk of DVT.
Infection. Infection can be either superficial or deep down at the hip prosthesis. This may occur soon after surgery or even many years down the track. The hip replacement may need to be removed while being treated with antibiotics. Infection is the complication that orthopaedic surgeons fear the most. On average the risk of deep infection is 1%. This means that 1 in 100 patients may develop an infection. We do everything we can to prevent this. This includes antiseptic body wash before the operation, antibiotics during and after the operation, and meticulous wound care after the operation. All joint replacements are performed in a laminar air flow operating theatre under sterile conditions.
Fracture. The bone supporting the hip prosthesis may fracture both during or after surgery. Small fractures may heal on their own. Larger, unstable fractures may require further operations.
Dislocation. Certain positions after hip replacement can cause the hip replacement to dislocate, particularly when a posterior approach has been used. For the first 3 months, precautions should be taken. Avoiding positions of high hip flexion to 90 degrees, avoiding low chairs and toilets, and avoiding bending to the ground to pick things up will help reduce this risk.
Change in leg length. The length of the leg being operated on can be altered during a hip replacement but not during a knee replacement. Patients with osteoarthritis may have a short leg without even noticing it. The aim of surgery is to restore leg length back to what is equal, and we use a number of tools to do this. We look at your x-rays and template the implant size before the operation. During the operation we may use a leg length guide which is inserted into the pelvis by a separate small incision. We also trial the implant, checking for stability and leg length before it is finally inserted. During a hip replacement, through a direct anterior approach, an x-ray is taken to confirm accurate leg length and implant size. We do not compromise leg length for stability. Very rarely if someone feels uneven, they may need to wear a shoe lift in the opposite shoe. More often than not with time you will not notice a difference in leg length. This is because you have gotten used to having a short leg and will need to get used to having equal leg lengths again.
Loosening. The femoral or acetabular component may become loose over time. This is rare with modern day techniques and prostheses. Further revision surgery may be required for this.
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Dr Matthew Broadhead
BSc(Med) MBBS(Hons) ChM PhD FRACS FAOrthA
Consulting in Coffs Harbour, Nambucca, South West Rocks and Yamba.