The THR is made up of two components; the acetabular component; a socket or cup which partly replaces the acetabulum and the femoral component, and a stem; which replaces the femoral head and part of the femoral neck. The moving parts between the ball and the cup (bearings) can be made of various materials such as ceramic, metal or plastic, and it is here that technological advances in bearing materials have reduced wear, which should increase the longevity of the hip replacement.

The stem and cup can be fixed to the patient’s bone by cement, or can come in direct contact to the bone and allow a living biological bond to form between the implants and the bone. Mr Damasena uses a variety of these implants to suit each patient’s demands and functional needs.

Indications

Cause of arthritis of the hip

It used to be thought that arthritis of the hip was nearly always caused by just wear and tear (primary OA). More recently, it has become apparent that actually in the vast majority of cases a structural abnormality can be identified that has caused the arthritis to develop (secondary OA).

The majority of these abnormalities occur before birth, or in childhood and include, developmental dysplasia of the hip, femoro-acetabular impingement, slipped upper femoral epiphysis (SUFE) and Perthes disease.

Other causes of secondary arthritis include conditions that cause damage to the cartilage including; trauma, avascular necrosis, infection, and inflammatory arthritis. Even within those cases where no obvious cause is found for the OA (primary OA), there is often a strong family history of hip disease, suggesting a genetic weakness in the patient’s cartilage.

The importance of identifying a cause for hip arthritis is that it can make a difference to treatment in how the surgery is technically performed and which implant is selected. Furthermore, it is becoming increasingly clear that some of these processes can be halted or even reversed by early intervention, if they are picked up early enough before arthritis becomes established.

The decision to undergo total hip replacement always remains with you, the patient. The surgeon will make sure of the diagnosis and advise you of the implications and possible complications. Pain and loss of function are the most important indications for joint replacement surgery.

Pain

Different people have different pain thresholds and also respond to painful diseases differently. We often try and quantify pain by the number of painkilling tablets or analgesics patients take each day, what the pain stops the patient from doing, and if their sleep is affected. If this pain cannot be controlled by other measures, then surgery is indicated.

Loss of function

Once again there is no absolute guideline as this is a very individual interpretation based on the patient’s own expectations of mobility and function. For convenience the surgeon will record the ability to put on socks, cut toe nails, go up and down stairs, get in and out of a car etc. as a measure of function.

Both of these factors affect the quality of life of the patient, at home and at work. When the quality of life is affected to an unacceptable level by the disease, and not controlled by other non-surgical measures, then surgery should be considered.

Implant survival

Joint replacement was previously reserved for elderly patients because we know that over 80% of implants will survive 20 years, but much less will survive in the more active and demanding younger patients. There is no doubt that joint replacement can make an enormous positive difference in the quality of life in younger patients, and should not be denied to them.

Contraindications to THR

There are very few contraindications to THR. However, some patients may be at very high risk of complications, and some may need special facilities such as ICU. The presence of active infection is a contraindication to primary hip replacement.

Surgical approach

Posterior approach

This is the favoured approach by Mr Damasena and is the most commonly used approach in Australia. It allows excellent access to the acetabulum and femur, can be extended easily if there is a problem during the operation, causes minimal damage to the walking muscles (making a limp much less likely), aids rehabilitation, reduces blood loss, and allows for a very discrete scar. It is particularly good for revision surgery and minimally invasive hip replacement.

Possible complications include

Infection <1%

Organisms are usually introduced onto the prostheses at the time of surgery from the patients skin, or just after surgery from wound problems. Occasionally infection can spread from a distant site to a well functioning prosthesis. Once established, infection is hard to eradicate without removal of the prostheses. Extensive surgery is usually required usually in 2 stages, and results can be poor.

Thrombosis/Pulmonary embolus 1%

Thrombosis in the deep veins of the leg (DVT) are common after hip or knee surgery, however rarely do these cause any problem and they need no specific treatment. About 1% of patients will have a DVT that requires treatment either because of calf pain, or when the thrombosis has spread into the thigh. About 1 in 1000 patients will have a thrombosis that will travel up into the lung (PE) where it can cause serious problems including death. All patients are assessed for risk preoperatively. Routine preventative management is by minimising operative time, keeping the patient hydrated, regional anaesthetic (if possible), foot/calf pumps to circulate the blood, and early mobilisation.

Mr Damasena will discuss ways to reduce DVT and PE with you prior to surgery. Mr Damasena uses Low Molecular weight Heparin (LMWH) whilst you are an in-patient and Aspirin as an outpatient. For those patients who are higher risk additional medications or more powerful blood thinning medications will be required.

Dislocation <1%

This occurs when the ball of the femoral component is dislocated from the acetabular cup. This is less common with hips with larger heads, minimally invasive approaches and with careful component positioning.

Anaesthetic complications <5%

Complications may result from the anaesthetic and stress of the surgery. Patients are carefully assessed preoperatively in order to try and minimise these risks, but clearly patients with some medical problems such as diabetes and heart conditions will be at higher risk. Optimising preoperative health, such as stopping smoking, reducing excessive weight, balanced diet etc., can further minimise risk.

Bleeding

It is very rare for patients to require a transfusion after this type of operation (<1%). Despite this we will test your blood before and after surgery to make sure you are fit for surgery and don not require a blood transfusion post operatively.

Death (very rare)

Leg length discrepancy

Every effort is made to equalise leg lengths during THR surgery. Occasionally this cannot be achieved because of the anatomy or stability issues, however the vast majority of people will have a leg length difference of less than 5mm. Often patients have been walking with a twisted spine to compensate for their painful or deformed arthritic hips. After surgery patients will often initially feel that the new hip is longer, until time and appropriate physiotherapy have corrected their postural abnormalities. These discrepancies need to be carefully assessed by the surgeon and physiotherapist.

Loosening

Modern implants may become loose after many years of use. This is often associated with wear.

Wear

The moving parts of all prostheses wear, causing bone loss and loosening of prostheses. Modern materials are harder wearing so that wear is becoming less of a problem.

Fracture of the acetabulum or femur<1%

This is rare, but more common in complex operations, deformity or revision operations. Most can be dealt with during surgery, but occasionally they are only picked up after surgery and may require intervention.

Vascular injuries<1 in 1000

Penetration or incision of an artery or vein.

Nerve injuries<1 in 1000

Heterotopic ossification (HO)

This is where new bone forms in the muscles around a hip replacement after surgery. It is more common in men, with OA, after fracture, in patients with previous HO, and patients with certain medical conditions. Although HO is rarely a significant problem, we routinely give anti-inflammatory medication after joint replacements to reduce the incidence and severity.

Implant breakage

This is very rare, but may require additional surgery.

Activity after THR

Walking and normal daily activity is encouraged after THR, but impact sport is probably damaging. Resurfacing is an exception to this, and we allow these patients to do anything after six months. If you are to have any invasive procedures after a THR such as dental work, bowel surgery etc. please inform your treating professional that you have a joint replacement, as you may need to be given antibiotics to protect the prosthesis from infection. The highest risk for this is within the first three months.