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Infection in Hip and Knee Replacements

Special Reports

by Paul Partington is a Consultant Orthopaedic Surgeon,

Each year in England, Wales and Northern Ireland using data from the National Joint Registry in 2013, more than 86,000 hip replacements and 91,000 knee replacements were performed. This is an underestimate of the numbers of joint replacements performed in these countries as not all of them will have made it the registry. Infection is thankfully uncommon, but rates from National Joint Registry data estimate a 1% infection rate for a total hip replacements and 0.5% for a total knee replacements. Of these, at least 50% are deep infection involving the hip or knee prosthesis. A national survey of Surgical Site came up with the infection rate of a mean of about 1.6% in hip replacements and 4.2% in knee replacement. Overall this means more than 5000 patients per year suffer post operative infection after hip and knee replacement in England, Wales and Northern Ireland.

Deep infection following hip and knee replacement is a devastating complication and often requires long periods of admission to hospital, multiple operations to try and get rid of the infection and is very expensive to treat in terms of long inpatient stays, expensive prolonged he operations and expensive revision (‘redo’) knee and hip implants. The outcome of patients who have had an infection and require surgical treatment is often poor, even after successful eradication of the infection. Following hip surgeries they may have a limp, leg length difference, muscle weakness or persistent pain. Often walking aids and additional care is needed. They are at risk of further revision procedures and function is reduced. Infection following knee replacements, even with the best treatment may give a stiff painful joint and reduced walking capability. Patients of working age can have long periods of absence from work and their employment threatened by the prolonged treatment required to treat and attempt to eradicate infection. Sometimes the whole total hip replacement has to be removed in an attempt to treat infection - what is called a Girdlestone procedure and this typically leaves the patient with a weak shortened leg and reliance on the use of sticks or crutches. Uncontrolled infection following a knee replacement occasionally results in amputation of the leg, above the knee with all that brings in terms of poor mobility, restriction of work and leisure activities and the need for care and change of housing etc. Patients suffer anxiety, depression and fear of further surgery or amputation.

Prevention of infection.
The risks of infection can be reduced and the process of infection prevention starts well before the date of surgery. While policies are not universal some or all of
the following may form part of the hospital protocols. Stopping smoking reduces the risk of infection and if this is a local policy, stopping several weeks before the date of surgery is optimal. Patients are usually screened by taking swabs from the groin, nose and other areas for MRSA carriage. If a patient is carrying this resistant organism on their skin then they maybe handled differently in the preoperative pathway possibly with antiseptic decolonising body wash and if MRSA carried in the nostrils antiseptic nasal cream. Patients who are immunosuppressed (increased risk of infection due to altered immune mechanism) should be optimised where possible. Diabetic patients for example who are at greater risk of infection should have the diabetes as well controlled as possible. Patients with rheumatoid arthritis who might be on drugs to reduce inflammation from their rheumatoid arthritis and slow the progression of joint damage from this condition may have to have some of their drugs stopped for a few weeks before surgery. These so-called disease modifying drugs are immunosuppressants and each
hospital will have a policy relating to these drugs and timing of halting them prior to an operation.

Once the patient is admitted to hospital usually joint replacement patients are segregated from emergency admissions and medical patients to reduce the chance
of cross infection from already infected patients. Preoperatively guidance will be given to the patients about having a shower or bath on a day of operation before they come into hospital, again reducing the number of bacteria carried on the skin.

Once they arrive at the operating theatre the skin will be carefully prepared and draped with sterile drapes and antiseptic skin preparation. Sterile instruments
will be used and the sterility confirmed and recorded in the nursing notes intraoperatively. During the surgery careful haemostasis (stopping bleeding), washing of the wounds with sterile fluid and careful closure with protective sterile dressings applied.

Postoperatively patients need careful management of any anticoagulants (blood thinning medications) with the correct dose and duration given. These anticoagulants may be prophylactic against deep vein thrombosis or pulmonary embolism, or restarting of anticoagulants for other conditions such as atrial fibrillation which require lifelong preventative treatment. This needs to be managed carefully so that excessive bleeding does not occur leading to haematomas, leaking wounds and infections.

If a haematoma or a leaking wound persists after surgery this has a great risk of developing an infection. This might be a superficial (surface) infection which can easily be treated by antibiotics, on the other hand, it can become a deep infection involving the joint replacement itself.

Treatment of Infection.
Deep infections involving hip and knee replacements are very difficult to eradicate. The bacteria stick to the metal and plastic and cement of the joint replacements and cannot easily be killed by either the body's defences or antibiotics. Often more surgery is required to debride, that is thoroughly clean the joint
and remove as much infected tissue as possible. This together with powerful, specific antibiotics can eradicate joint infection completely. The chance of success of eradication of postoperative deep infection by debridement without removing the joint replacement itself depends on the timing. It is critical that this is performed earlier enough to get rid of the infection before it is taken a strong hold and cannot be removed from the joint without removing the joint replacement itself. Typically, debridement and retention of the prosthesis (joint replacement) is likely to work only if dealt with within the first few weeks after the joint replacement if put in. If a leaking wound is ignored and left too long then more major surgery in the way of revision (redo) of the joint replacement will be required.

Revision surgery itself is technically difficult, should be performed by a surgeon appropriately trained and experienced in this surgery and with support of an interested Microbiologist. Preoperative specimens of fluid should be taken from the joint replacement to find out what bacteria is involved, intraoperatively
multiple specimens should be taken to be sure of the organisms and the correct antibiotic treatment. The removal of the joint replacement and the cement
needs to be extremely thorough and avoid, as much as possible, making the situation worse with fractures, ligament damage, nerve or blood vessel damage and
so on. Most often this surgery is what is called a two-stage procedure where the first operation is to remove the infected joint replacement, cement and infected soft tissue and then a second operation, usually several weeks later, is performed to put back a new joint replacement. Before the second operation can be performed there needs to be proof, as much as possible, that the infection has been eradicated usually with a further specimen of fluid removed from the joint (aspiration) and sent for analysis.

Unfortunately despite all of the measures and improvements in healthcare, the increased expectation of joint replacement patients and the ability to perform surgery on higher risk cases that might have been denied previously, means that infection as a complication of joint replacements is here to stay. The numbers of hip and knee replacements continue to increase year by year. In good hospitals and trusts all of the preventative management for infection follows a protocol and treatment of infection is performed by an experienced multidisciplinary team with appropriate training and expertise. Unfortunately sometimes one or more steps in this pathway fall down and there maybe areas of care which fall below a standard expected by their peers. Simple examples might include omission of antibiotics or inappropriate timing of antibiotics at the time of implantation of the joint replacement. More complex failing might include inappropriate wound management and delay in debridement of a wound that is evolving towards a deep infection.

For these patients appropriate expert advice is required to determine whether infection and its complications were preventable, or correctly managed when they occurred or not.

Paul Partington is a Consultant Orthopaedic Surgeon, and specialises in Revision Hip and Knee Arthroplasty. He is an experienced expert witness with a specialist interest in the complications of hip and knee joint replacement and has prepared independent reports for both Claimant and Defendant in this area of interest.

He can be contacted via his secretary Anne Slater on 07541878329 or via email This email address is being protected from spambots. You need JavaScript enabled to view it. website: www.pfpartington.co.uk

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