Total hip replacement

Total hip replacement (THR) is one of the most successful interventions in modern medicine.
The first successful THRs were performed in the UK by Professor Sir John Charnley in the 1960s (fig 1), and since then it has alleviated the pain and improved the mobility of hundreds of thousands of patients crippled with arthritis of the hip.
 
The THR is made up of two components (fig 2): 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 (see Bearings for 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. At Orthopaedics WA we use 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).

Stacks Image 1874
Fig 1: Professor Sir John Charnley's book.
Stacks Image 10933
Fig 2. Deltamotion Corail implant.
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.
Stacks Image 11044
Fig 3: Implant survival rates.

Advances in technology such as high performance hip replacement bearing and implants have improved implant survival in this group. However, the likelihood of further re-do surgery is inevitable, and this presents potential future problems for these patients. Options more suited to the younger hip patient are joint preserving procedures such as osteotomies around the hip, impingement surgery, alternative bearings and resurfacing of the hip.

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 approaches

There are four commonly used approaches. Orthopaedics WA use all of these, but have specific indications for each.
Stacks Image 11117
Fig 4: Surgical approaches.
Posterior approach
This is the favoured approach of most hip surgeons, and is our most commonly used approach. 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. The main drawback is that in some surgeon’s hands, this approach has been associated with a higher chance of dislocation.
Anterior (front) approach and Lateral (side) approaches
These two approaches make the hip more stable, but make injury to the nerves and muscles around the hip much more likely. We only use these for patients with hip fractures, where stability is more important than the risk of muscle injury.
Trochanteric
Orthopaedics WA occasionally use this specialist approach for hip impingement surgery in order to preserve the blood supply, for complex primary and revision hip surgery for adjusting the muscle tension or for special access to the hip joint.

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.

At Orthopaedics WA we do not believe that heparin significantly reduces the risk of important thrombosis, and definitely causes wound problems. However, the hospital policy is that this is used in all joint replacements. Orthopaedics WA treat most high-risk patients with warfarin for six weeks after surgery or LMWH.
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, MIS 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 Orthopaedics WA patients to require transfusion after this operation (<1%), and at Fremantle, we have published results showing one of the lowest transfusion rates in the World.
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.

Orthopaedics WA provide the full range of treatments for disease of the hip including joint preserving procedures, hip replacement, hip resurfacing, MIS hips, specialist implants and bearings, and revision surgery. Orthopaedics WA have designed a new hip replacement, and have assessed several others.
See the frequently asked questions about hips. Also see the Related links on this page.
Related links: