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Oscar the Bionic Cat

Firebird PR publicises a world-first in veterinary surgery: a cat who was successfully given two prosthetic implants in a single operation

Cats have nine lives so they say, but few felines can have had a luckier escape from the jaws of death than Oscar, whose rear paws were chopped off by a combine harvester while he was basking in the sunshine, only to have them replaced through a bioengineering miracle, performed by one of the country's leading neuro-orthopaedic veterinary surgeons.

Surrey-based Noel Fitzpatrick is a neuro-orthopaedic surgeon who has given the two year old cat a pair of new artificial feet in a single surgical procedure – something which has never been done before by any team anywhere in the world. The revolutionary design of the feet uses custom-made implants to 'peg' the ankle to the foot and mimics the way in which deer antler bone grows through skin – a case of science 'copycatting' the natural world.

These pegs, or ITAPs (intraosseous transcutaneous amputation prosthetics), were first developed by a team from University College London led by Professor Gordon Blunn, Head of the Centre for Bio-Medical Engineering at UCL's Institute of Orthopaedics and Musculoskeletal Science. Working in partnership with UCL, Fitzpatrick has pioneered the use of these weight-bearing prosthetic implants, combining engineering mechanics with biology to give Oscar the cat two new feet.

In a three-hour operation, the veterinary surgical team had to insert the ITAPs by drilling into one of the ankle bones in each of the back legs – an extremely delicate feat, which could have fractured the ankle joint before the procedure had even begun, and even more challenging had to be performed twice. These artificial implants which are attached to the bone at an amputation site are coated with hydroxyapatite, which encourages bone cells to grow onto the metal. The skin then grows over the special umbrella at the end of the ITAP to form a resilient seal against bacteria and potentially fatal infections. The ITAP itself protrudes through the bone and skin, allowing the custom-built artificial paws to be securely attached.

Oscar's lucky break began when his local vet Peter Howarth from St Saviour in Jersey referred his owners Kate and Mike Nolan who live in the Channel Isles, to Fitzpatrick Referrals in Eashing in Surrey, following the accident last October. His life-threatening injuries first had to be treated and a course of antibiotics administered before surgery could be contemplated. "We had to do a lot of soul-searching and our main concern has always been whether this operation would be in Oscar's best interests and would give him a better quality of life," explained Kate. Her husband Mike continues, "Through our own background reading, we were aware that this sort of procedure is cutting-edge and also has an impact on human medicine, so knowledge about the way that Oscar's been treated can be carried over to human treatment going forward, so that's good for everyone."

Following successful surgery on 13 November, the focus of the veterinary team has turned to the slow process of rehabilitation and helping Oscar to learn to walk again – firstly using external scaffolding anchored to the tibia for five weeks to protect the new implants until the ITAPs integrated into the bone and also the skin grew onto the ITAP. Remarkably Oscar was trying to stand within a day of the operation and despite some problems with infection that had to be overcome, in less than four months Oscar could stand and bear weight equally on all four limbs. He has since been fitted with a series of prototype new paws to ensure the best possible long term fit and now can claim to a be a truly bionic cat.

Full limb amputation frequently constitutes the standard of care in cases of trauma victims such as Oscar, who have experienced irreversible vascular or neurological damage to limbs. While such procedures are common in both humans and animals, and despite a range of technological and surgical advances, post-amputation complications still arise when stump-socket exoprostheses (strap-on) are used, including infection, stump morbidity, abrasions and pressure sores, and mobility problems associated with weight-bearing, often leading to fractures and limb failure.

What makes this procedure so complicated is that Oscar's feet were severed at the junction of the tarsus and metatarsus, which is the junction between the ankle bones and the arch of the foot, but a cat stands up on its toes, whereas humans stand on the entire flat of the foot, so the ankle is the equivalent of the cat's hock.

As Noel Fitzpatrick explains: "The real revolution with Oscar is because we have put a piece of metal and a flange into which skin grows into an extremely tight bone, with very narrow tolerances in the region of nanometres, rather than millimetres. We have then successfully managed to get the bone and skin to grow into the implant and we have developed an exoprosthesis that allows this implant to work as a see-saw on the bottom of an animal's limbs to give him effectively normal gait. Oscar can now run and jump about as cats should do."

Find out more about the work of Dr Noel Fitzpatrick and his team