Over 115,000 hip replacement surgeries happen in the UK every year. Most often, hip replacement surgery is needed to treat hip pain caused by osteoarthritis. This refers to gradual wear and tear of the cartilage that lines the ball and socket joint of your hip. First, the cartilage thins and eventually it is completely worn away, exposing the bones. As bone rubs against bone, hip pain and stiffness worsens, which ultimately can lead to needing hip replacement surgery.
Although osteoarthritis is commonly associated with getting older, it can also occur in younger individuals after a trauma to the hip (eg hip fracture) or those with structural problems in their hips, specifically femoroacetabular impingement (FAI) and developmental dysplasia of the hip (DDH). Both FAI and DDH can lead to degeneration of the hip joint which leads to osteoarthritis.
Rheumatoid arthritis, an autoimmune disease where your body’s immune cells mistakenly attack healthy tissues in your joints, can also lead to the need for hip replacement surgery.
Before considering hip replacement surgery, your doctor will discuss your symptoms and medical history with you in detail, as well as perform a physical examination and take X-rays of your hip.
If the cause of your hip pain is identified as hip arthritis and it is clear that your hip pain and consequently your quality of life could be significantly improved with hip replacement surgery, your doctor will discuss the risks, benefits and complications with you. You will have time to reflect on the information, ask questions and raise any concerns before committing to surgery.
A nurse will determine whether you are fit enough for surgery during your pre-operative assessment, which will involve filling in a questionnaire.
Hip replacement surgery involves the use of general or spinal anaesthesia. This places a certain amount of strain on your heart and lungs, which is why you need to be fit enough to endure this. A consultant specialising in anaesthesia (an anaesthetist) may also need to be consulted to determine your fitness for surgery.
The day of your surgery
You will be asked not to eat for six hours before your surgery — you can drink water up to two hours before your surgery. Once you’re admitted onto the ward, you will change into a hospital gown and be seen by your anaesthetist and your surgeon. Your surgeon will once again go through the risks of the surgery and if you are happy to go ahead, you will be asked to sign a consent form.
Immediately prior to your surgery, you will be given anaesthesia. Your anaesthetist will decide on the most appropriate anaesthesia in your case ie general anaesthesia where you are asleep throughout your surgery or spinal anaesthesia with a sedative, where you remain awake but drowsy and cannot feel anything from the waist down.
Although hip replacement surgery is major surgery, tens of thousands of hip replacements are performed every year. What’s more, improvements in surgical techniques mean that, in some cases, hip replacement surgery can be performed as minimally invasive surgery. This means less tissue needs to be removed and smaller cuts are made, resulting in smaller scars of around 10cm (compared to previous scars of around 30cm).
Hip replacement surgery can be used for a partial hip replacement or a total hip replacement.
Total hip replacement surgery
This involves hollowing out your hip socket and removing the top of your thigh bone. A new hip joint will then be created by inserting a new socket into the hollow of your pelvic bone and a ball with a rod attached that is inserted into the upper part of your thigh bone. A smooth, gliding surface will be created between your ball and socket by fixing a liner onto the socket.
The new parts of your hip joint can be fixed in place using acrylic cement or can be uncemented. When cement isn’t used to hold the implants in place, natural bone growth is encouraged by using implants with a roughened surface or coated with a special material. Uncemented implants are more commonly used for younger individuals leading more active lifestyles.
Partial hip replacement surgery
A partial hip replacement involves only replacing the ball part of your hip joint, leaving your natural socket in place. This type of surgery is often performed to treat hip fractures ie where the head of the thigh bone has fractured.
What materials are used for hip replacements?
The artificial ball and socket used in a hip replacement can be made of plastic, metal or ceramic. In most cases, sockets are made of metal or plastic and the balls are made of metal or ceramic. The liner is usually made of ceramic or highly crosslinked polyethylene.
Due to improvements in the plastics and ceramics used in hip replacements today, artificial hip joints are more durable. This means that around 90% of hip replacements will last on average 20 years.
In more recent years, developments in the composition of ceramics used in hip replacements have seen the use of fourth-generation ceramic in the balls and liners of artificial hip joints. The evidence so far suggests that these hip replacements can last 30 years or more.
Every surgery comes with risks; some risks apply to all surgery, while others are specific to the type of surgery you’re having.
General risks of surgery include blood clots, which can lead to deep vein thrombosis (DVT) or a pulmonary embolism (PE), infection, bleeding and nerve damage.
Steps are taken to reduce these general risks, such as taking antibiotics to prevent infection, taking blood thinners to prevent blood clots and taking the drug tranexamic acid to reduce bleeding. The risk of nerve damage can also be reduced with surgical techniques that help visualise nerves to avoid injuring them.
Risks specific to hip replacement surgery include hip dislocation and differences in leg length. Hip dislocation refers to the ball of the hip joint popping out of the socket. This occurs in less than 5% of individuals after hip replacement surgery and in most cases happens because the artificial ball isn’t as large as the natural ball that was present before surgery.
Leg length inequality is also a risk in hip replacement surgery. This is because those needing surgery often have a difference in leg length due to wearing away of the cartilage in their affected hip joint, often causing a limp. Surgeons endeavour to correct for this difference but in some cases, this may need surgery to lengthen the leg. Correcting any difference in leg length helps reduce the risk of hip dislocation.
Read more on the risks of hip replacement surgery.
Standard hip replacements use a liner fixed into a socket, with the ball moving along the liner. Dual-mobility hip replacements are a recent development where not only is the ball able to move along the liner but the liner can move inside the socket. This allows a greater range of movement before the ball is likely to pop out of the socket and, therefore, reduces the risk of dislocation.
Dual-mobility hip replacements are, consequently, especially helpful for individuals with a higher risk of hip dislocation, namely individuals with a failing hip replacement who need revision surgery, as well as those with hip dysplasia and hip fractures.
Mr Parag K Jaiswal is a Consultant in Trauma & Orthopaedics at Spire London East Hospital and the Royal Free London NHS Foundation Trust, specialising in hip and knee surgery, including sports injuries, arthroscopy and replacements, as well as the treatment of young adults with hip problems and older adults with failing hip and knee replacements. He qualified from Guy’s and St Thomas’ Medical School and completed fellowships in Canada and at Frimley Park Hospital, which has one of the highest volumes of hip arthroscopies in England. He was also awarded the British Hip Society Travelling Fellowship, which he used to visit one of the world’s leading arthroscopic hip surgeons in the USA, Marc Philippon.
If you're concerned about symptoms you're experiencing or require further information on the subject, talk to a GP or see an expert consultant at your local Spire hospital.