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by Christopher Williams, FRACS
Orthopaedic Surgeon
As we age, our joints naturally wear out. When wear is severe, it produces the condition known as Osteoarthritis. This results in pain, stiffness, and a significant reduction in quality of life for thousands of New Zealanders. Before 1960, pain killers and crutches were the mainstays of treatment, with people sometimes becoming wheelchair or bed bound because of the severity of symptoms.
 Knee Replacement
In the last forty years, however, Orthopaedic surgery has seen a revolution centered around the ability to replace worn and painful joints, with new metal and plastic pain-free artificial joints. In the 1960’s, the hip was the first joint to benefit from this new technology, based on initial work done by Sir John Charnley. Knee joints followed in the early 80’s, and more recently shoulder and elbow joint replacements have become available.
Although the shape of each joint is different, the basic design concept remains the same. At the time of surgery, the ends of the old worn joint are carefully cut away using bone saws, and new manufactured or “prosthetic” ends are cemented or impacted on in their place. Traditionally, this was metal on one side of the joint, and high-density polyethylene plastic on the other. More recently, metal-to-metal or metal-to-ceramic surfaces have become available, which may last longer.
Joint replacements are some of the most successful operations currently available to surgeons and their patients. Several thousand are performed each year in New Zealand. They offer a very high chance of relieving pain, while still permitting reasonable movement of the joint. This allows a return to normal daily activities, independence, and for a lot of people “gives them back their lives”. Typically, 3 months after surgery, playing tennis or completing 18 holes of golf is possible. Walking for an hour a day, swimming, or cycling, are all achievable. For most people, these benefits far outweigh the need to spend a few days in hospital, and the low risk of complications.
Artificial joints are not perfect, however, and despite all possible cares, they do occasionally develop infections, or dislocate. Long-term wear is also a problem, and these joints on average need to be re-done after 15 years. Although materials are constantly improving, we also know that the way the joint is put in and aligned is very important in producing a longer-lasting result. Good positioning in most cases is not a problem, but in very deformed joints, it can be challenging to achieve.
This has stimulated researchers and surgeons to look for new ways to accurately implant the latest generation of joint replacements. The result is the option of computer-assisted surgery. Computers are now able to intra-operatively display a real-time virtual image of the joint being operated on in the theatre. This helps the surgeon position the components anatomically, improving durability. Although not needed for most operations, in difficult cases it is very useful.
Aorangi Hospital has used this system for a number of patients, and it will continue to be available if required. This means that an additional group of patients with severe joint deformities, who previously may not have been good candidates for joint surgery, can now be considered for this procedure. The vast majority of people with worn out painful joints now have a joint replacement operation available to them, which for nearly everyone will significantly improve their quality and enjoyment of life.
Christopher Williams, FRACS
Orthopaedic Surgeon
Chris Williams is a general Orthopaedic Surgeon, operating at Aorangi Hospital. He has a special interest in Joint Replacement surgery.
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