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Ski on: Paul Wilmott, 51, is back on the slopes thanks to a new type of bespoke knee replacement created with the help of a 3D printer

Keen skier Paul Wilmott feared he might never hit the slopes again after an old injury to his left knee flared up again last June.

Even mowing the grass became painful and doing any exercise made it swollen, painful and unable to withstand pressure.

He was forced to abandon his favourite pastimes of skiing and cycling.

Yet thanks to a new type of bespoke knee replacement created with the help of a 3D printer, the 51-year-old company director was back in his skis by December.

'I had no pain whatsoever, even though I was on the slopes at Ischgl, in Austria, for up to seven hours a day and skiing is renowned for putting pressure on knees,' says Paul.

'My new knee is remarkable and I feel so lucky to have the new implant.'

Paul has been fitted with a bespoke implant made by US company Conformis which uses the latest in 3D technology.

The company says the implant makes recovery faster, there is less bone and tissue removed during surgery and knee function may turn out to be as good as new.

Consultant orthopaedic surgeon Richard Carrington of Spire Bushey Hospital, Hertfordshire, who fitted Paul's knee, says: 'This is a huge advance – a bespoke knee replacement is like having a suit fitted and adjusted rather than buying a standard size over the internet. All knees are completely different.'

Knee problems like Paul's develop because of cartilage wearing away.

Cartilage covers each end of the bones in the knee – the femur (thigh bone), patella (knee cap) and tibia (shin bone) – allowing the joint to glide smoothly.

When it wears away the bones are exposed and rub against each other. This causes pain, stiffness and swelling, and severely affects quality of life.

There are around 85,000 knee replacement operations in the UK every year. A total replacement involves the worn part of all three bones being replaced with metal and plastic implants while a partial replacement replaces just one part.

Mr Carrington last year performed five partial knee replacements using the Conformis option, along with about 120 standard replacements.

The new bespoke replacement has been available in Germany for four years, and Mr Carrington trained for the surgery there.

The procedure is offered in the UK at a few private hospitals, with limited NHS availability.

The Conformis implant requires the removal of only up to 7mm of bone, compared to up to 12mm for a standard implant.

Paul' s implant is known as the iUni G2 and replaced his tibia. 'You could see on scans that there was no cartilage left and the bones were touching,' says Mr Carrington.

For the procedure, the patient first has a CT scan to produce a 3D image of the knee. The design of the replacement joint is based on what engineers see on this scan. Next a mould is made to this specific design, using 3D printing technology. From this mould the engineers construct the bespoke implant using a plastic called polyethylene and a metal alloy known as cobalt chrome, hard-wearing materials that should last 15 years. These components exactly replicate the shape of the patient's knee.

The 3D engineers also print out iJigs – small bespoke plastic instruments – that slot on to the knee and show exactly where the bone has to be cut, improving accuracy and meaning fewer cuts are needed.

The implant is fitted during an hour-long operation under general anaesthetic. The surgeon first makes a two to three inchlong incision into the inside of the knee cap and exposes the knee bones. Damaged cartilage is removed and small cuts are made into the bones. The parts of the replacement joint are inserted and fixed with bone cement.

Paul had suffered from knee pain since his mid-30s. He says: 'I went through years of pain and operations – I was on four types of pain relief a day.

'By the time I had the replacement, I couldn't even mow the grass because any weight bearing was agony. I love skiing, sailing and running so found the situation incredibly frustrating.'

He is thrilled with the results of his surgery, saying: 'Next day I was able to put weight on my leg and two days later I was in the hospital swimming pool with a physiotherapist. I occasionally have discomfort but that's unsurprising considering I've had about ten operations altogether.

'I'm just so happy that I finally found one that worked – and worked brilliantly.'

spirebushey.com