Hip replacement is, by and large, a reliable and successful surgery. However, a small number of people may have problems following surgery. The success rate of surgery is 90 to 95% at 10 years.
The potential problems include –
1. Infection in the hip.
Infection in the replaced hip joint is a serious but rare problem and the risk is less than 1%. Superficial infections in the wound present as discharge from the wound, and generally respond to antibiotics and dressing. Deep infection presents as persistent wound discharge, formation of sinus over the wound, or persistent pain. Deep infection may often require revision hip surgery - removal of the artificial hip joint and insertion of a new joint.
The surgery is done in clean air operating theatres, and with use of appropriate antibiotics, the risk of infection is very low (less than 1%). With meticulous surgical technique, strict asepsis and rigourous attention to detail, it is possible to achieve an infection rate near zero.
Infection at the time of surgery is extremely rare. Most of the infections seen in modern practice are late infections, and these are the result of spread of infection from another site in the body through the blood stream. In my patients, the risk of infection is extremely low - less than 1 in a 1000 (0.1%)
2. Dislocation of the hip
The ball of the artificial hip joint articulates with the socket. The socket in most hips joints is hemispherical, and provides the articulation, but does not capture the ball. Accurate positioning of the components, good muscle balance and restoration of normal anatomy at the time of hip surgery prevent dislocation of the ball.
Less than 1 percent people may experience a hip dislocation – which is the ball coming out of the socket. The hip is painful after dislocation, and the leg appears shortened and malrotated. It is not possible to walk with a dislocated hip.
Hip dislocation requires emergency admission and relocation of the hip joint under anaesthetic. In most patients, the hip is stable afterwards, but one third of patients having a hip dislocation may require revision surgery.
Modern techniques of soft tissue repair, improved materials and component designs have enabled surgeons to achieve a dislocation rate less than 1%.
Dislocation risk in my patients is 1 in 300 (0.3%)
3. Deep vein thrombosis and Pulmonary Embolism
Deep vein thrombosis is development of a blood clot in the veins of the calf, thigh or pelvis. This is a risk with any hip or knee surgery and prophylaxis against this provided in the form of tablets or by injections. Foot pumps are provided while patients are in hospital and these mechanically help blood circulation. Current guidlines recommend prophylaxis for 5 weeks after surgery.
Deep vein thrombosis causes swelling of the leg and pain, and temporarily delays rehabilitation following surgery. Clots require treatment with Warfarin.
Pulmonary Embolism is a very rare complication where a clot from the leg travels to the lungs and blocks circulation. Small clots are inconsequential and may not be noticed or detected. Large clots are potentially life threatening.
I use an oral medicine to reduce the risk of blood clots. This is for a period for 4 weeks after hip surgery.
4. Leg length difference
Arthritis of the hip leads to wear, and a shortened leg. At the time of surgery, it is usually possible to equalise leg lengths. Excess shortening may not be fully correctable. Very rarely, the operated leg may end up being slightly longer. This may be required where the muscle tension in the hip is inadequate and does not support the hip unless stretched. With modern techniques, this is very rare.
Sometimes, the leg may simply feel long, despite being equal. This is because the muscle have been restored their normal lengths. This feeling will subside with time.
I use an accurate measurement system for assessing leg lengths at the time of surgery, and with that, it is possible to match leg lengths accurately.
Following hip surgery, walking aid in the form of Zimmer frame, crutches and sticks are needed temporarily. As muscle strength improves, the gait improves and by two months, most people are able to walk without sticks. Some people can take a longer time, and this is within normal expected recovery patterns.
I use a surgical approach whereby the main muscles which move the hip joint are not divided or damaged, and as a result, most patients are able to walk normally within 4 weeks.
6. Rare complications
Rare complications of hip surgery include chest infection, urinary tract infection, or injury to the nerve at the back of the hip (sciatic nerve). In some instances, there may be a crack in the thigh bone during fixation of the femoral component. These are generally detectable and treatable at the same time.
Some people experience swelling of the leg after surgery, which is normal and usually settled within 3 months. Some degree of stiffness of the hip may also be noticed.
The risk of dying as a result of hip replacement is extremely low – risk is a fraction of 1%. Pulmonary embolus, heart attack or stroke, especially with a history of such an event in the past, are the underlying factors for this.
7. Long term complications
In the long term (years), the fixation of the artificial joint into the bone may become loose, or the polyethylene liner may wear out. These situations result in pain and damage to bone around the hip joint. Revision to a new hip joint is required to correct these problems.
Revision of the hip is more extensive operation than the primary surgery and the risk of complications is also higher in revision surgery.
Despite all the risks mentioned here, most patients (90%) have a speedy and uneventful recovery after hip surgery and do well. 5 to 8% may have a minor complication which delays rehabilitation, but does not affect the outcome. Only 1 or 2 percent end up with a significant problem. It is advisable that the surgery is undertaken only when the expected benefit outweighs the potential risks.
New technology and modern implants are helpful, but not a substitute for surgical skill. Some modern implants do not have proven track records and the surgeon endeavours to choose an implant which is safe, reliable and the right choice for the particular patient.