The Hip Joint and Hip Replacement
In people who have arthritis (osteoarthritis, rheumatoid arthritis), the smooth cartilage lining on the bones of the hip replacement wears away, making the joint painful and stiff. The majority of patients who have arthritis, which is severe enough to warrant hip replacement, are over 65 years old. Younger patients needing surgery have often suffered from a childhood hip problem or other cause of “secondary arthritis”.
A more detailed description of arthritis is in the conditions section of the site.
During a total hip replacement, the top of the femur is removed and a replacement ball on a stem is inserted in its place. A metal + ceramic (or metal + plastic) cup is frequently used to replace the socket. An artificial joint is called a prosthesis. The prosthesis may be attached directly to the bone via a “press-fit” (effectively a tight wedge effect) and be supplemented with screws. In some cases, special bone cement is used to fix the prosthesis in place.
Hip replacements have evolved over 40 years although the designs of most hip replacements are not very different to each other. In Australia approximately 30,000 to 35,000 initial hip replacements are performed every year. For those patients who clearly have hip arthritis as the cause of their pain and disability (and in whom surgery goes well) the outcome of hip replacement surgery is excellent. It is considered one of several great surgical advances of last century (along with cataract surgery for blindness and open heart surgery).
Alternatives to Hip Replacement
Not everyone who has arthritis of the hip joint needs a hip replacement. Patients may wish to liaise with Arthritis Tasmania (1800 011 041 or www.arthritistasmania.com.au).
Non-surgical treatment options for hip and knee arthritis are discussed in the conditions section of this site.
Hip replacement surgery is performed when a patient’s level of pain or functional disability warrants proceeding with surgery, acknowledging the risks of surgery, the potential costs, the recovery period and the potential for future surgery. It is important to have realistic expectations regarding the surgery and outcomes. There is no “age at which a hip replacement should be performed”. It is rare for surgery to be made more difficult by waiting.
How Long Do Hip Replacements Last?
Worldwide literature studies have shown that the majority of hip replacements will not require further surgery within the next 15 years. Some patients may require reoperation within the first few months due to complications of the surgery. Within Australia a “National Joint Replacement Registry” has tracked the reoperation on hip replacements that have been inserted since 2000. Each year the registry is able to update surgeons on the statistical likelihood of patients requiring a reoperation to their hip replacement. By 15 years post hip replacement fewer than 10% of patients will have had any parts of their hip prosthesis replaced again. Not surprisingly it shows that younger (and therefore more active) patients have a higher chance of reoperation on their hip replacement over the first 10+ years.
An artificial hip can never be as good as a normally functioning hip joint. There are a number of reasons hip replacements are replaced or re-operated upon. The commonest (approximately 30% of reoperations) is gradual loosening of the cup or stem in the bone over the course of many years. Approximately 20% of re-operations are performed because of recurrent dislocation of hip replacements (the ball jumping out of socket in certain positions of the hip). Fifteen percent of re-operations are performed for infection (which may be apparent within the first year, or may occur many years after hip replacement due to an infection spreading through the bloodstream). Fifteen percent of re-operations are performed after trauma, with the femur breaking and requiring a new femoral prosthesis to help stabilise both the hip and the break. The remaining 15% of re-operations are performed for many reasons (including very rare implant related faults or recalls).
Preparation at Home Before Hip Replacement
If the planned surgery is more than 6 weeks away patients may benefit from seeing a physiotherapist. The recovery period following surgery may be shorter in those patients who commence an exercise and activity program prior to surgery.
If any infections, cuts, or grazes occur prior to surgery in the leg being operated upon, or if patients suffer any other generalised medical illness, they should inform Dr. Mackie’s office. If urine tests performed at preadmission clinics demonstrate an infection or other tests are of concern it will be safer to delay elective surgery until the condition has been treated.
Prior to any surgery it is important to consider general health and risk issues. It is important to disclose any medical problems, medications taken and allergies to medications.
Any blood thinning medications and medications for serious heart or lung conditions should be discussed prior with Dr. Mackie or the anaesthetist. It is necessary to cease Aspirin / Warfarin / Plavix / Iscover / Pradaxa / fish oil or any other medications which cause excessive bleeding. Learn about preparation for major surgery.
Patients will require a preoperative visit to an anaesthetist in order to ensure the anaesthetist is willing to proceed without further medical assessments. This visit will allow patients to discuss the type of anaesthetic that can be used for a hip replacement and postoperative pain management.
General Physician Review
If required - a referral to see a specialist physician will be arranged to deal with any medical conditions, which may be improved pre-operatively (making the surgery and recovery safer). A general physician will be able to familiarize themselves with a patient’s medical conditions through a preoperative consultation and then be available in the immediate postoperative period to help prevent or treat any medical complications. Dr. Mackie will determine which patients may require this additional medical support.
Hospital Preadmission Visits
Before the operation, an appointment with a “preadmission service” at the hospital is usually arranged. At this appointment, patients will receive education about their time in hospital from Nursing staff. If required: a physiotherapist or occupational therapist will discuss home requirements. Aids and services can be planned before going into hospital. These might include handrails in the bath or shower, a raised toilet seat, and help with shopping or laundry.
This service also assists in arranging the following preoperative general health tests:
- Chest X-ray if needed
- ECG (Cardiograph) if needed
- Blood Tests
- Urine test to exclude infection
Day of Surgery
Typically, patients are required not to eat or drink for about six hours before a general anaesthetic.
For morning operations it is recommended that patients fast from midnight prior to surgery (no food or drink) although a small sip of water may be used to take normal medications. For afternoon operations it is recommended that patients have nothing after an early breakfast (~ 07:00 am). Some anaesthetists will permit clear fluids (water) to be consumed up until 2 hours prior to surgery.
Dr. Mackie will generally speak with patients prior to the anaesthetic on the day of surgery. He will use a texta-marker to confirm the side for operation and draw an arrow on it. In the period immediately prior to surgery patients will be asked multiple times by nursing and medical staff to confirm which hip is being operated upon, to avoid surgery to the incorrect side.
A Total Hip Replacement Operation
Total hip replacement is a major operation. It involves a stay in hospital of generally 3 - 5 days, until it is safe to walk with the aid of sticks or crutches. The operation itself takes one to two hours, although most people are away from their room or ward for at least three hours.
The operation may be performed under a general anaesthetic or spinal anaesthetic (using local anaesthetic injected into the lower back). During spinal anaesthesia the patient may remain awake but have no sensation from the waist downward. The majority of patients who (after discussion with their anaesthetist) have a spinal anaesthetic also have a general anaesthetic.
Once the anaesthetic has taken effect, an incision, usually around 10-20cm long is made along the hip and thigh. The joint is replaced as below and the incision closed (usually with dissolving stitches).
- Diseased / arthritic bone is removed.
- The acetabulum is reshaped to take a new socket.
- The new socket, comprising of a metal shell (with ceramic or plastic surface) is inserted and may be additionally supported by screws.
- The canal of the femur is opened up in preparation for insertion of the stem and the femoral stem is inserted either by a firm press-fit or using “bone cement” to act as a grout.
- A femoral head (the new ball) is attached.
Hip Resurfacing and Metal on Metal Hip Replacements
These prostheses initially received media attention because of a perceived quicker recovery and improved function following surgery. The risk of complication however has been shown to be greater with these prostheses and more than twice as many require further surgery within 5 years compared with traditional hip replacements.
The worldwide recall of one particular metal-on-metal hip replacement has led to most companies removing them from routine use. Their use in Australia dropped from ~3,000 per year in 2006 to ~ 50 in 2015!
Dr Mackie routinely uses ceramic bearing surfaces rather than metal bearing surfaces for hip replacements. Some patients may be deemed more appropriate to have a metal (rather than ceramic) ball on the top of the femur prosthesis. If so, a plastic insert into the shell or acetabulum is used rather than metal or ceramic.
Cemented Vs Uncemented Hip Replacements
The femoral prosthesis can be inserted via a “press fit” / wedge-type effect or by using a form of bone cement which helps to support the prosthesis. There are advantages and disadvantages to each. Dr. Mackie continues to use both options, allowing for the option best suited to each patient to be used. In general, most patients under the age of 80 will have a press-fit stem used because bone quality is adequate to grow onto the new prosthesis. Older patients may require a cemented prosthesis to help lock it in.
Surgical Approach and the Anterior Hip Replacement
Some hip replacements are now inserted via the anterior (front) approach to the hip. There may be a slightly more rapid recovery of muscle function around the hip after such an approach and some patients are off crutches within a couple of weeks.
The approach however is generally restricted to certain implants and has not been shown to have any longer term benefits for patients. A higher number of early complications after this approach has been reported worldwide, especially whilst surgeons develop their experience during early training in the technique. It is very difficult to perform “cemented” hip replacements via the technique.
Dr Mackie has elected not to use the anterior approach to the hip and uses a “posterior” approach (via which the majority of hip replacements worldwide are inserted). He would prefer patients to use crutches for 2 – 3 weeks postop in order to slow them down during normal wound healing and bony integration of the new hip. Taking such a postoperative course is aimed at improving the longevity of the hip replacement, rather than attempting a very rapid increase in activities.
Minimally Invasive Hip Replacement
Hip replacement surgery has become a very successful treatment for many patients. Technical advancements have allowed the use of customised instruments that provide easier access for surgeons to the hip joint. The surgical approach relies on adequate visualisation of the bones and surgical site. Dr Mackie uses the available customised instruments to ensure the smallest possible scar is used for safe access to the hip replacement for each patient but does not wish to “push the boundaries” by attempting to make incisions “smaller than anyone else”.
After Hip Replacement Surgery
During the stay in hospital, every effort is made to keep discomfort to a minimum. The anaesthetist will explain the different kinds of pain relief that can be used. Most people find that, after the first week, they need only mild painkillers in tablet form.
In hospital, the physiotherapist will visit to help with exercises designed to promote recovery. Patients are generally encouraged to move their new hip from the first day after the operation. By the time they go home, they are able to walk with sticks or crutches and will have learned how best to move about and manage daily tasks. However, they will need to make arrangements to be driven home.
Before discharge, a nurse usually gives advice about caring for surgical wounds, hygiene and bathing, and a follow-up appointment in the outpatient clinic is arranged.
A period of time may be required in a rehabilitation ward prior to a final return home. This is determined by the preoperative health and mobility of patients and after assessment of how independent they may be in their home environment postoperatively. In-patient rehabilitation involves transfer to a different ward or hospital between 4 and 7 days post-operatively and a minimum of 1 week of additional in-patient time. Many patients however will be assessed as being safe to discharge directly home from ~ day 4 - 5 postop.
Most people find that they are able to move around their home and manage stairs. However, some routine daily activities such as shopping, will be difficult for a few weeks so it's important to arrange help.
There are certain movements that should be avoided if possible in the first 6 weeks. If not avoidable then the movements should be performed carefully or slowly. These include:
- bending the hip at more than a right angle,
- bending down rapidly,
- twisting the hip,
- crossing the legs rapidly,
- sitting on low seats (including low toilet seats),
- lying on one side without a pillow between the legs.
When not walking or doing the recommended exercises, it is safer sit in an upright chair rather than a low couch or sofa.
It won’t be safe to drive until Dr. Mackie advises (usually after six weeks for a hip replacement).
The exercises recommended by the physiotherapist are a crucial part of the recovery process, so it's essential to continue them.
The new hip will improve over at least six months.
Side Effects and Complications of Hip Replacement
A planned hip replacement is generally a safe surgical procedure. For most people, the benefits in terms of pain relief are greater than the disadvantages. However, in order to give informed consent, anyone deciding whether or not to have this operation needs to be aware of the possible side–effects and the risk of complications.
Side effects are the unwanted but usually temporary effects of an otherwise successful procedure. Examples include feeling sick as a result of the general anaesthetic and painkillers.
In addition to these, some specific side effects can be expected for this operation:
- The new joint is likely to be uncomfortable for several weeks.
- There is likely to be some temporary pain and swelling in the thigh and knee.
- It is quite common to have a swollen leg and ankle for more than three months afterwards.
- The operation will leave a 10-20cm scar along the hip and thigh.
- Blood loss may require a transfusion of blood in < 10% of patients
Complications are unexpected problems that can occur during or after the operation. Most people are not affected, but the main possible complications of any surgery are excessive bleeding, infection or an unexpected reaction to the anaesthetic. Complications may require further treatment such as a further operation to stop bleeding, or antibiotics to treat an infection.
Patients may suffer heart attacks, strokes, chest infections, urinary infections and other medical problems which usually reflect their general preoperative state-of-health. In rare circumstances patients may die as a result of medical conditions being exaccerbated by the stress associated with anaesthesia and surgery.
If patients experience increasing pain, swelling, redness, fevers or are generally unwell it is important to be reviewed early to ensure no infection has occurred. If infection is suspected most patients will be readmitted to hospital for assessment and possibly a prolonged period of in-patient management. It is important that Dr. Mackie is notified if any other medical practitioner is treating a potential infection.
Up to 1 in 200 patients may require repeated surgery (2 – 3 washout operations over a 1 – 2-week period) for an infection, 6 weeks of antibiotics via intravenous drip and up to 1 year on antibiotics. More than 80% of infections respond to such treatment with the hip “saved”. Occasionally the hip replacement needs to be removed and a temporary antibiotic cement block inserted. A new hip replacement is then reinserted several months later.
Although hip replacement is generally a very successful operation, a small number of patients may experience ongoing pain. This may be due to another underlying case for the pre-existing pain. Some patients will have intermittent ache in the hip with pressure or weather changes for up to 1 – 2 years after surgery.
Nerves that control the leg may rarely be damaged. This is usually very slight and rarely permanent. Most people don't notice it. A very small patch of numbness next to the scar is common.
Occasionally, tiny cracks are made in the bone while fitting the new joint. These usually heal by themselves, but on rare occasions a fracture can result, needing additional treatment, such as prolonged bed-rest or a further operation.
The operated leg may be slightly longer than the other one. When this occurs (to ensure muscle balance in the hip), the difference may be barely noticeable, but sometimes it is necessary to wear a raised shoe on the shorter side. It is generally preferable to have a slightly longer leg after hip replacement than a shorter leg (as a shorter leg may be associated with relative slack within the muscles and ligaments and increase the risk of dislocation). Most patients will have a sense of different leg lengths early after hip replacement due to altered muscle strength and a tilt in the pelvis for a short time.
The new joint may dislocate (the ball may come out of its socket) in up to 2 or 3 out of every 100 patients. This is most likely to happen immediately after the operation (due to rapid twisting or leg movements) and requires an anaesthetic to manipulate the joint back into position. Occasionally, dislocation happens repeatedly and another operation may be needed.
For up to six weeks after the operation, it's possible to develop a blood clot (known as a deep vein thrombosis, or DVT) in the veins of the leg. This clot can break off and cause a blockage in the lungs. In the majority of cases, this is treatable, but it can be a dangerous condition. Preventive drugs, or mechanical means to squeeze the feet should be used to reduce this risk. If a DVT is suspected (pain and swelling in the calf which is worsening) an ultrasound is required for diagnosis and blood thinning medications may be required for treatment.
All artificial joints are subject to “wear and tear” of use and may over time loosen, crack or even break. Some joint replacements will require a revision operation, as per information earlier in this guide.