I find that my patients who have had a unicompartmental knee replacement (UKR, uni-knee, or half-knee replacement) are among my happiest and most active post surgery. I treat many younger patients with knee arthritis, and I find that in many of these patients uni knee is an excellent option, allowing them to maintain an active lifestyle. Compared with my colleagues, I perform a high number of uni knee, comprising about 25% of knee joint replacements in my practice.
X-ray of a uni knee
Most studies show that patients having uni knee have excellent results, with less pain, faster recovery, improved function, and a more ‘normal’ feeling knee.
Studies have shown more people report being ‘highly satisfied’ with their uni knee than do patients who have had total knee replacement. Likewise, fewer people report being ‘dissatisfied’ with their union knee than those who have had total knee replacement. Function is also better following uni knee, than after total knee replacement. Many studies have reported a statistically significant improvement of physical activity following uni knee, with hiking, cycling and swimming the most common activities. Sport participation before the onset of restricting symptoms ranged from 64 to 93 % and slightly decreased by 2-9 % following uni knee. The return to activity rate ranged from 87 to 98 %.
A unicompartmental knee prosthesis, and the custom 3D-printed patient specific cutting guides used during surgery.
Despite these benefits, unicompartmental knee replacement has declined in popularity in recent years due to concerns about its higher revision rate compared with that of total knee replacement. Revision rate is the percentage of cases which have been re-operated, and the prosthesis changed. Revision may occur most frequently in UKR due to loosening of the prosthesis from its attachment to the bone, or due to arthritis developing in other areas of the knee.
The revision rate in Australia for total knee replacement has been 5.5% after 10 years. That is to say, 5.5% have been re-done for some reason within 10 years of surgery. Uni knee has had a much higher rate of failure, with a 15% revision rate when considering all implants and all surgeons. However, the prosthesis I use is performing much better, with a 5.6% revision rate after 7 years in all of the implants inserted in Australia.
Factors which can impact on how long the implant lasts for include:
- Implant design – certain types of design are faring better than others.
- Patient selection – the knee needs to demonstrate arthritis confined to one area of the knee, and good movement with intact ligaments.
- Surgeon experience – analysis of the National Joint Replacement Registry has shown that surgeons who regularly perform the procedure in high numbers have a far lower revision rate.
- Final knee alignment – overcorrection of any deformity or inserting a prosthesis which is too thick can promote faster development of arthritis on the opposite side of the knee.
To discuss whether uni knee is the right option for you, please contact my office for an appointment on 1300 695 633 or enquiries@drbalalla.com.au
Copyright Dr Balalla 2016.
