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Technique boosts success of knee replacement surgery


SHAH: Simpler way for knee surgery

The Nairobi technique was developed in 2014 to reduce the risk of a knee replacement becoming loose five years after surgery.

Arthritis is a disease that causes inflammation, pain and stiffness in the joints.

Osteoarthritis, the most common form of arthritis, is associated with the wear and tear of joints that comes with age, leading to the degeneration of joint cartilage and the underlying bone.
Early to moderate osteoarthritis is treated using medicine, injection, physiotherapy and walking aids.
Moderate to severe osteoarthritis which generally occurs in people above the age of 60, with three to four of them suffering from arthritis and one to two of those with arthritis needing total knee replacement surgery to relieve the pain, correct deformity and improve stability.
In total knee replacement surgery, the knee cartilage is replaced by implants, and the gold standard is to use cement to fix the implants to the bone.

POOR ALIGNMENT
Generally, the replaced joint loosens gradually over time and the patient needs a second (revision) surgery after 10 to 15 years.
However, the joint can loosen earlier due to poor cementing technique and poor alignment of the leg during surgery.
Proper alignment of the lower limb after knee replacement surgery is the key to long-term success, but the conventional technique of alignment raises the risk of poor alignment. The conventional technique gives five to 10 per cent poor alignment.
Proper alignment means that the centre of the hip, knee and ankle are in one line – that the mechanical axis is maintained.

To ensure proper alignment, surgeons in the Western world use computer assisted surgery, a navigation system that helps the surgeon align the knee accurately.

PROHIBITIVE COST
However, this method is not available locally as its cost is prohibitive. It is also difficult to use in osteoporotic bone.
For a long time, locals surgeons used the traditional method and relied on three x-rays – one of the hip, the knee and the ankle – to estimate if they had gotten the alignment right.
When full leg x-ray services became available about four years ago, we realised that in 30 per cent of patients, we were not achieving proper alignment.
This meant that while the patients would leave happy that their issue had been fixed, when they walked, the pressure would gradually loosen the implant, and they would need another replacement within five to six years, instead of much longer.
To get around this, we developed the “Nairobi technique” which has produced a proper alignment rate that is as accurate as the one achieved when using the computer navigation system.

INNOVATIVE TECHNIQUE
With the Nairobi technique, once the surgeon has aligned the leg using the traditional technique, he or she can now use the image intensifier (x-ray) on the hip joint to identify the centre, make a cut at the knee and do the knee replacement while ensuring that the hip, knee and ankle are properly aligned.
There is no need to use the image intensifier on the knee and ankle as they are superficial joints and it is not difficult to locate their centre.
With the full-leg x-ray, the alignment can be confirmed, and with proper alignment using the Nairobi technique, the knee replacement can last 15 to 20 years without becoming loose.
Moreover, the Nairobi technique is cheaper, easy to use and easy for surgeons to learn as it requires no customised instruments.

In addition, with this technique, no extra tracer pins are required and there are no pin track infections.
After knee replacement surgery, within the second or third day, the patient can start walking with support, and within a month they can walk without support.

Dr Shah is an orthopaedic surgeon who practises at the Central Memorial Hospital in Thika and at the Aga Khan University Hospital. He presented his findings on the Nairobi technique at the Kenya Orthopaedic Association conference in Mombasa last year, as well as at a conference in India