A total hip joint replacement is an operation to remove a damaged hip joint and replace it with parts made from metal, plastic or ceramics. The aim of the surgery is to relieve pain and restore function to the joint.
Hip joint replacement surgery is a common operation undertaken in New Zealand as planned (non-urgent) surgery in both public and private hospitals, typically involving a 4- to 7-day hospital stay. If the operation is done in a private hospital, and paid for by the patient or through health insurance, the cost is likely to be between $22,400 and $27,300.
Why have hip replacement surgery?
The most common cause of deterioration of the hip joint is osteoarthritis. This condition causes the usually smooth cartilage (which covers the ball-shaped end of the thighbone and the inside of the hip socket) to become damaged and worn. This means the bones within the hip joint rub together, causing them to become roughened and irregular. This, together with the development of small breaks in the bone, causes pain and stiffness.
Other conditions that can damage the hip joint to the extent that requires replacement include rheumatoid arthritis (inflammatory arthritis), osteonecrosis (where poor blood supply to the ball portion of the hip causes it to weaken and deform) and hip fractures (particularly in the elderly due to falls).
People who might benefit from hip replacement surgery include those who have hip pain and/or stiffness that:
- Limits everyday activities, such as walking, bending, or rising from a seated position
- Interferes with sleep
- Persists despite anti-inflammatory/pain medication, physical therapy, or walking supports.
An orthopaedic surgeon will assess the need for a hip replacement, taking into account medical history, lifestyle, physical examination (especially range of motion of the hip joint and strength of the supporting muscles), blood tests, and x-rays or magnetic resonance imaging (MRI) scans.
Although most people who undergo hip replacement surgery are between the ages 50 to 80 years, consideration for hip joint replacement surgery is based on a patient's pain and disability, not their age. A person also needs to be well enough to cope with both a major operation and the rehabilitation that is required afterwards.
A hip replacement is a major operation and there are many things to consider before deciding upon surgery. The risks and benefits of the surgery should be discussed with the surgeon. The most common risks include:
- Anaesthetic risks (common to all surgery)
- Infection — both of the wound and of the artificial hip joint itself
- Development of blood clots in one of the deep veins of the legs (deep vein thrombosis)
- Damage to the nerves and blood vessels surrounding the hip joint
- Fracture of healthy portions of the hip joint during surgery
- Dislocation of the artificial hip joint
- A change in the length of the leg that has been operated on.
The artificial hip joint (prosthesis) consists of a ball and stem, and a socket. These can be made of various metals (eg: stainless steel, chrome, titanium), ceramics, plastic, or a combination of these. The two components of the prosthesis fit together to form a smooth joint. Some prostheses are “cemented” into place using special acrylic bone cement. Others do not require cement and rely on bone growing around the prosthesis to anchor them into place.
The surgery typically takes up to 2 hours to complete and can be performed using either local or general anaesthetic. Surgery begins with an incision being made along the side of the hip joint that is to be replaced. The muscles that support the hip joint are detached and parts of the thighbone (femur) and hip socket (acetabulum) cut away.
The ball and stem component of the prosthesis is inserted into the thighbone and the socket component of the prosthesis is inserted into the pelvic bone. The artificial ball and socket are then fitted together and the surgeon reattaches the muscles to the top of the thighbone. Drainage tubes may be inserted to drain any fluid and/or blood from the new joint and the incision is then closed.
Antibiotics are usually given during and after the operation to prevent the development of infection in the new joint. A blood transfusion may also be required. This will be discussed by the surgeon before surgery begins.
A catheter will be in place to drain urine from the bladder. This usually stays in place for 24–48 hours. Pain will be managed by administering pain-relieving medications by tablet and via a drip in the hand or arm. Some people may have an infusion of pain-relieving medication administered through a small tube in their back (an epidural). This is usually given for up to 48 hours after surgery.
There is an increased risk of developing blood clots in the legs after hip replacement surgery. Preventative measures may include:
- Early mobilisation: Sitting up and even trying to walk with crutches or a walker soon after surgery will be encouraged
- Wearing elastic compression stockings or inflatable leg coverings (compression boots) to help keep blood from pooling in the leg veins, which reduces the risk of clots forming
- Blood-thinning medication: Injected or oral blood-thinning drugs may be given after surgery.
The healthcare team will work together to set movement guidelines and exercises that will assist with recovery. The success of the surgery depends on following these instructions while in hospital and carrying out the prescribed exercises when at home. The following guidelines may be given for recovery when at home:
- Do not cross the legs (including the ankles)
- Do not bend down low
- Avoid lifting heavy objects
- Avoid forceful or jarring movement of the hip
- Avoid twisting movements of the hip
- Do not lie on the operated side
- Always have a pillow between the legs when lying on the unoperated side
- Do not stand for long periods
- Sit in a firm chair with arms (to assist getting in and out of the chair)
- Treat scratches and cuts promptly to decrease the chance of infection affecting the new joint.
Crutches or a walking frame will need to be used for up to six weeks after the operation. By six weeks, the majority of people should be able to return to most normal activities, including driving. Full recovery can take 3 to 6 months.
Outcomes of surgery
Long-term follow up may be recommended in order to monitor the wear of the artificial joint. It may be that replacement of the artificial hip joint will be recommended if it wears significantly. In general, most hip replacements last at least 15 years if cared for and not subjected to excessive stress.
There have been concerns about some metal-on-metal hip prostheses wearing out sooner than anticipated. Metal-on-metal protheses have only been used in a minority of all hip replacement surgeries and are now rarely used. People who have had a hip replacement and have concerns, or are experiencing pain or discomfort, should see their doctor. Despite these concerns, hip replacement is generally a safe and successful procedure that reduces pain and improves mobility.
Mayo Clinic (2020). Hip replacement (Web Page). Rochester, MN: Mayo Foundation for Medical Education and Research. https://www.mayoclinic.org/tests-procedures/hip-replacement/about/pac-20385042 [Accessed: 14/07/20]
Ministry of Health (date not stated). Total hip replacement: a guide for patients (PDF pamphlet). Wellington: New Zealand Ministry of Health. https://www.health.govt.nz/system/files/documents/pages/guide-hip-replacement-surgery.pdf
NHS (2019). Hip replacement (Web Page). Redditch: National Health Service (NHS) England. https://www.nhs.uk/conditions/hip-replacement/ [Accessed: 14/07/20]
Southern Cross Annual Report Summary (2020). How much does it cost? www.southerncross.co.nz/annualreport