Replacing only worn-out parts of the knee

SINGAPORE - Up to a third of those with knee osteoarthritis have two of the three parts of a knee so badly worn out that they rub against each other causing pain.

Many of these patients have their entire knee removed and replaced with an artificial one, instead of just the parts which are diseased. But a total replacement means they will lose their cruciate ligaments, which connect the bones of the knee joint and aid in a person's ability to sense joint position. With the ligaments gone, patients often feel that their knees move less naturally.

Now, local studies are showing promising results for a relatively new and less drastic procedure.

In a bicompartmental knee replacement, the surgeon replaces the two parts of the knee with two implants, leaving the remaining knee portion and ligaments untouched.

The worn-out parts are commonly the medial (inner) and patellofemoral (front) sections of the knee, as more forces pass through them than through the lateral (outer) part of the knee, said Dr Andrew Quoc Dutton, medical director and consultant orthopaedic surgeon at the Singapore Medical Group (SMG Orthopaedic Group) and a visiting consultant at the National University Hospital (NUH).

Doctors at NUH and the Singapore General Hospital (SGH) began performing bicompartmental knee surgery six years ago and the results have been similar to those from a total knee replacement, which is considered the gold standard in treating knee osteoarthritis.

This spells new hope for patients whose active lifestyles place greater demand on their knees - usually those below 65, say doctors.

Dr Dutton said bicompartmental procedures were done as early as the 1980s, but poorly designed implants caused high failure rates, so the method never quite took off.

In contrast, the knee implant in a total replacement has a proven track record with more than 95 per cent of them still working after 15 years.

Last year, NUH published two studies which showed that patients who have undergone either a bicompartmental knee or total knee procedure reported about the same levels of pain, stiffness and other symptoms, as well as complications and ability to perform activities after surgery, such as walking and getting out of bed.

One study, published in February last year in The Journal Of Knee Surgery, tracked 16 patients who had bicompartmental knee replacements and 20 who had total replacements.

On average, the bicompartmental group can move 24 degrees more than the other group six months after surgery, even after accounting for differences in age and range of motion before the operation.

The second NUH study, in which 15 patients with bicompartmental knee replacements were assessed against 12 with total replacements, was published in the Journal Of Orthopaedic Surgery in December.

Researchers found that the newer procedure resulted in less blood loss during the operation, as less bone had to be removed. Likewise, Dr Darren Tay, a consultant at the department of orthopaedic surgery at SGH, said he never had to give a blood transfusion to a patient during a bicompartmental procedure, while up to 10 per cent of those receiving a total replacement would require one.

In SGH's study of 40 patients, those who had a bicompartmental procedure reported less blood loss and pain compared with those who had a full replacement. Both groups had minimal complications, said Dr Tay. The hospital intends to present its findings at an international conference later this year.

The downside is that a patient who has had a bicompartmental procedure faces a higher chance of needing more surgery in the future if the implants loosen or when the rest of the knee wears out.

Both doctors said the cost of a bicompartmental procedure is about the same as a total replacement.

At SGH, a private patient pays $17,000 to $20,000, while a patient at Mount Elizabeth Hospital pays $20,000 to $25,000. These include up to five days of hospital stay.

Former physical education teacher Foo Yong Lai, 52, found relief for her weak and swollen left knee after a bicompartmental knee replacement in 2009. She can now navigate the stairs with ease and has no problem doing a full squat.

Said the temple volunteer: "I no longer exercise by running, but I can definitely run after a bus if I need to."

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