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Making an artificial knee fit perfectly

The Straits Times - by Joan Chew (27 January 2011)

These days, one can customise just about anything from shoes to travel packages.

But how about a one-of-a-kind tool that helps your surgeon during knee replacement surgery?

What if this customised jig or precision cutting instrument makes more accurate cuts in the bones so that surgical time is reduced and the artificial knee fits like a glove?

At least two operations using such a tool have been performed in Singapore. In November last year, Dr Teo Yee Hong, consultant at the department of orthopaedic surgery and head of service (adult reconstruction) at Tan Tock Seng Hospital, used one to carry out a knee replacement. He completed another on Tuesday.

Last month, Dr Kevin Lee, then a consultant with the National University Hospital, also performed such an operation.

His patient, retiree Sharon Lee, 56, had endured years of osteoarthritis until the stiffness and pain in her right knee became unbearable in August last year. She had tried many treatments for her condition, which is caused by degeneration of the cartilage in the joints. She took pain killers and glucosamine supplements, tried acupuncture and tui na here and in Malaysia and even had hyaluronic acid injections to lubricate her joints.

These helped to provide some pain relief. When the pain intensified earlier last year, she was still hesitant about undergoing surgery as she still held on to the hope that 'things would become better on their own', she said in Mandarin.

But when she was increasingly confined to the house and found she could get around only with the aid of a walking stick, she knew an operation was inevitable.

A knee replacement would remove the worn and damaged surfaces of the bones at her knee joint and put in their place an implant made of metallic alloys and polyethylene.

About a month before surgery, she underwent magnetic resonance imaging (MRI) for her knee. Dr Lee put the 3-D image into a special computer program to create a detailed plan for the operation.

Using the program, he could assess the fit of different implant sizes on her knee - a process usually done only in the operating theatre. He could also plan the cuts to make.

Then he ordered a jig that was customised to her operation to be made in Belgium.

The jig is used to make cuts at the end of the thigh bone (femur), top of the shin bone (tibia) and kneecap surface (patella) during surgery.

Although conventional knee replacement operations are already so successful that more than 90 per cent of implants are still intact 15 years after surgery, what the computer technology does is to make the fit close to perfect.

Now an orthopaedic surgeon and medical director of the Centre for Joint & Cartilage Surgery and Singapore Sports Orthopaedic Surgery Centre, Dr Lee said: 'The patient-specific jigs allow highly accurate positioning of the implants, which means that patients will find it easier to adapt to their artificial knees."

A special computer program used to plan the operation and customise tools can cut surgery time by 20%

The pre-operative plan can potentially cut surgery time by 20 per cent, he added - from 90 minutes to less than 75.

This could reduce the risk of surgical complications such as infections for the patient.

TTSH's Dr Teo said it also means less anaesthesia is required.

But few patients have opted for the jig up until now because of its cost.

Dr Teo said full-paying patients at TTSH have to fork out about $2,000 more for the MRI and customised jigs.

A check on the Ministry of Health (MOH)'s website showed that on average, it would cost $3,925 for a patient hospitalised for six days in a Class C ward at TTSH for knee replacement surgery.

With MediShield coverage and Medisave, a patient will not have to pay any out-of-pocket expense, said a MOH spokesman.

The Centre for Joint & Cartilage Surgery, a subsidiary of the Singapore Medical Group, charges between $400 and $450 for the MRI and up to $1,800 for the jig.

Last week, Ms Lee, who is single, was busy shopping for Chinese New Year goodies.

She said it was worth the money to get a precise replacement.

Her only regret was not going for surgery earlier. As she had relied on her left knee to support her weight, it is starting to give her problems now.

She advised other patients: 'Go for surgery quickly if you feel pain.'

joanchew@sph.com.sg

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Source: The Straits Times © Singapore Press Holdings Limited. Reproduced with permission.