About Total Hip Replacement
A total hip replacement (THR) is an operation to replace the worn ball-and-socket joint with new components. The head of the femur is removed, allowing a metal stem to be inserted into the femur itself. This can be uncemented (allowing the bone to grow onto the prosthesis), or cemented (using acrylic bone cement as a grout to lock the stem onto the bone).
The socket is prepared to accept a new metal socket, which is coated with a porous material to allow the bone to grow onto it. Screws may be required as well to ensure a good hold. A liner is inserted into the metal socket, usually made of high density polyethylene. Finally, a ceramic head is placed onto the stem to articulate with the liner.
The aim of a hip replacement is to relieve your pain, while maintaining or improving your movement. You can expect gradual improvement up to 1 year following hip replacement, although the most rapid improvement is between 6 weeks and 6 months.
Prior to surgery, you will have a pre-operative assessment to ensure that you are fit to undergo the operation. You will also see a physiotherapist, who will show you exercises and teach you to use crutches. On the day of the operation, you will be seen by me and by the anaesthetist before surgery. Your leg will be marked and the consent form signed. The operation itself will usually take around 1 hour. The majority of these operations are carried out under a spinal anaesthetic, where the legs are numb, but sedation can also be given to ensure that you are sleepy.
Following surgery, you will be transferred back to the ward. Pain control is prescribed to allow you to undertake your exercises; please alert the nursing staff if more pain relief is required. You will be seen by the physiotherapists to encourage you to move the hip and start mobilising.
Most patients are able to return home within 3 days, once safely mobilising with crutches and able to climb stairs. You will be able to put your full weight through the operated hip. The hip will be somewhat stiff and sore for the first few weeks following surgery and regular pain relief may be needed. It is important to maintain your exercises in these first weeks to ensure a good range of movement of your hip, as well as to decrease the risk of dislocation. The incision is usually closed with a dissolvable stitch and skin glue, so there are usually no staples or sutures to remove. I encourage patients to keep the waterproof dressing in place for 2 weeks, although showering with the dressing on is permitted.
You will be seen by me or my team at the six week mark to ensure that all is progressing well. An X-ray is not usually required at this visit. If all is well, your next appointment will be at the 6 month mark, with an X-ray at that visit.
Outcomes of Total Hip Replacement
The majority of THR patients do extremely well and are very satisfied with their new hip.
All of my joint replacement patients are invited to participate in the National Joint Registry which monitors outcomes of hip and knee replacement. Using this national data, and other national registries, we can predict that approximately 97% of THRs are still functioning well after 10 years, and 95% at 15 years. Loosening or early failure of the hip replacement is rare, and if it were to occur then the hip may need to be exchanged for a revision total hip replacement.
Complications of Total Hip Replacement
Although THR is a reliable procedure and one of the most successful operations performed today, all such operations come with attached risks, although the chances of one of these occurring is very small. These can include:
Bleeding – a blood transfusion may be required but this is rare.
Infection – This is a potentially devastating complication and all efforts are taken to prevent this. These include the use of antiseptic skin preparations during surgery, ultra-clean air laminar flow operating theatres with every care taken to maintain sterility during surgery, and the use of antibiotics during and after surgery. Despite this infections can still occur. These may be superficial wound infections which can be successfully treated with antibiotics, but a severe deep infection is likely to need further surgery to wash out the hip, or even to remove and replace the components. The risk of a deep infection is less than 0.5%.
Dislocation – this occurs when the femoral head comes out of the socket. Although this is relatively rare, historical studies have shown a risk of approximately 3%. During surgery, every care is taken to accurately position the implants and reconstruct the soft tissues to decrease the chance of dislocation. Following surgery you will receive advice regarding exercises and safe positioning of the hip to reduce the risk of dislocation.
Blood clots – a blood clot in the leg (a deep vein thrombosis; DVT) or in the lung (a pulmonary embolus; PE) is a potentially serious complication. The risk is decreased by giving you blood thinning medication for 14 days following surgery. The most important factor to reduce this risk is getting you mobile as quickly as possible. The risk of a DVT that causes symptoms is approximately 2%; the risk of a PE is 0.5%. If you are unfortunate enough to develop either of these, then blood thinning medication such as warfarin is usually required for 3-6 months.
Nerve injury – the sciatic nerve is close to the operative area and potentially could be damaged during surgery. Fortunately this is very rare. If the sciatic nerve is injured, it will affect the ability to raise the foot (called a “foot drop”). The majority of these cases recover by themselves, but a splint to maintain foot position may be needed. Extremely rarely, this damage is permanent.
Leg length difference – often the affected leg is slightly short prior to the operation. The surgery is carefully planned and templated to reconstruct the correct leg length and your leg may feel long after surgery. Any sensation of lengthening will settle over the first few months and any significant leg length difference is very uncommon.
Wear – Modern hip prostheses mean that your joint replacement should last many years. The polyethylene can wear out, and if the metal components are well fixed, the bearing can be replaced. However, if the wear is significant, it can lead to loosening of the implants and therefore a need for revision surgery.
Revision – THRs have a very low rate of revision and the majority of patients with them do very well. The implants I use have excellent long term results with a low revision rate. However, should the THR wear out or become loose, then it may be necessary to remove and replace the components.