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Computer navigation and knee joint replacement

Posted Nov 06 2012 8:26am

Mr Dinesh Nathwani is pioneering the use of computer navigation to improve outcomes for people whose knee joints have started to degenerate. In this article he explains how computer navigation is used and how it could revolutionise knee replacement surgery in the years to come.

As the average life expectancy continues to rise, far more people are living to the age of 65 and beyond. After more than 60 years of carrying the weight of the body, the joints in the knees often develop problems. Of the 70,000 knee replacement operations that take place in the UK each year, the vast majority are performed in the over-60s.

Most patients in the UK have either a total knee replacement or a partial knee replacement.

In a total replacement operation, both sides of the knee joint are replaced by artificial components. These work well and, with physiotherapyThe use of physical therapies such as exercise, massage and manipulation. and exercise, most people who have them experience an increase in their mobility and fitness and are free from arthritic pain in their knee. Despite this, a completely artificial joint never ‘feels’ the same as the natural knee; some patients find they cannot bend their knee fully and kneeling is often described as being very uncomfortable.

Patients who have a partial knee replacement generally report being more satisfied with their progress and outcome. Only one side of the knee joint is replaced; the damaged area is removed but healthy parts of the knee are left in place. This creates a much more natural feeling once the initial recovery has taken place.

Computer navigation and knee joint replacement

Getting better results depends on two key factors: diagnosing the extent and position of damage in the knee joint with greater accuracy and then using more precise methods to ensure that only damaged tissues are removed and replaced. Since a very accurate partial knee replacement is a less extensive operation, there are other advantages. Patients tend to have less post-operative pain and fewer complications, they need to spend less time in hospital and their initial recovery is much faster.

Partial knee replacement techniques are becoming more widespread as the evidence for their benefits grows. In 2012 fewer than 10% of all knee replacement operations were partial knee replacements (in the rest, the entire joint was replaced). This number is now increasing as new techniques that enable orthopaedic surgeons to work with enhanced accuracy, such as computer navigation, become more widely used.

The concept of using computer navigation in surgery is well established. Surgical navigation is used more frequently by neurosurgeons performing intricate brain surgery but systems for orthopaedic surgeons have become available since about 2005. One leading system is still named ‘BrainLab®’, which reflects its origins in brain surgery. However, the computer navigation system for knee surgery has been heavily adapted from the one used by neurosurgeons, as the challenges are quite different.

This system is installed at relatively few NHS and private hospitals around the UK – it is restricted to the larger teaching hospitals and some of the more extensive private facilities based in central London.

Once the patient is on the operating table, scanning of the knee takes place from every possible angle to obtain three-dimensional images of the joint and its damaged tissues. The data is fed into the computer system, which matches it with an extensive database of previous CTThe abbreviation for computed tomography, a scan that generates a series of cross-sectional x-ray images scans. This information allows the surgeon to create and then execute a surgical plan that will lead to minimal tissue disruption. The amount of bone removed is kept to the barest minimum so that as much healthy knee structure as possible is retained.

The surgeon uses the navigation system to decide exactly where to remove bone from the knee joint with sub-millimetre accuracy and also to choose exactly the right shape and size of knee prosthesisAn artificial device attached to the body., making the surgery much more individualised to specific patients.

It is important to stressRelating to injury or concern. that the navigation system is a guide for the surgeon – it’s not like robotic surgery in which the computer helps control the movements made by the surgical instruments. Using such a system in orthopaedic cases requires specialised training to enable the surgeon to make the most use of the system as a tool and then the operation itself is done using traditional operating skills and techniques.

As with any new drug or medical technique, it is important to collect data from patients who have been treated using computer navigation, and to then compare their outcomes with results obtained in patients who have had standard knee replacement surgery. As computer navigation systems have not been around for that long in orthopaedics, this data is still being collected and analysed.

To date, the signs are that increasing the accuracy of alignment of the partial knee replacement leads to a much better functional result for the patient. As many as forty in every 100 patients having a total knee replacement done without computer navigation are dissatisfied with their new joint a year after surgery but only 3 in 100 patients having a partial knee replacement using computer navigation expressed any concerns about their recovery.

After recovering from the surgery itself, and following a period of physiotherapy and exercise, patients report being able to bend their knee to a much greater angle than those who have had standard total knee joint replacement. The repaired rather than replaced knee joint also ‘feels’ more natural, more part of the body and people are generally much happier with the results.

Systems for increasing the accuracy of orthopaedic surgery will become more commonplace in the next decade but their uptake may be hindered in the NHS due to cost and resource implications.

Application of computer navigation techniques already extends to total and partial knee replacements and hip resurfacing and total hip replacements. It may, in the future, also play a role in developing joint replacement surgery for joints that are currently less frequently replaced – such as the ankle, shoulder and elbow.

As technology improves so does the ability to accurately execute the surgery and there are currently many groups, including one at Imperial College, who are involved in improving the software and hardware systems that is on track to create a new solution for 21st century knee reconstruction.

Once surgical techniques are made as accurate as possible, the next focus will be to improve implant design, moving towards a more custom-made solution for joint reconstruction. The ideal will be to use implants made specifically for individual patients and then inserted surgically with a very high degree of accuracy.

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