A three and a half year old white German shepherd dog from Dorchester, Dorset, has become the first in the world to have an ankle amputation prosthesis.

Mitzi Davis was trampled by a horse which crushed her foot, tearing off all blood and nerve supply, back in October 2010.

In a pioneering procedure, Dr. Noel Fitzpatrick from Fitzpatrick Referrals fitted a titanium implant to the bone below her joint - the first time a prosthesis has been put in a fully articulating bone of a dog.

The ITAP implant (which stands for Intraosseous Transcutaneous Amputation Prosthesis) is a new way of attaching prosthetic limbs. It involves implanting a titanium rod in the bone, onto which skin can attach just like a deer's antler, leaving a "peg" sticking out of the skin which can't get infected because of the resilient seal. The technology was developed for dogs by Professor Gordon Blunn at University College London (UCL) in association with Dr. Fitzpatrick.

The "exo-prosthesis" or foot is then screwed onto the peg and can be changed and modified as necessary. First Mitzi's gait had to be modelled on a computer, much like in a CGI movie. Then a foot was made using computer finite element analysis, designed so that the material of the foot would absorb shock from the ground and, most importantly, snap and break before the implant in the bone or the bone itself.

Dr. Noel Fitzpatrick said: "Today of course has implications not only for animals but for human amputees in the future and I will continue to work closely with Professor Blunn and the Stanmore Implants team to advance this technology to improve the quality of life for animals and eventually, for humans."

The ITAP technology is being tested in humans and has already been used to create a prosthetic for a woman who lost her arm in the July 2005 London bombings.

Professor Blunn said: "Humans and other animals share a large number of degenerative musculo-skeletal conditions. The repair process of the musculoskeletal system is essentially the same whether in a dog, cat or human being.  Reconstruction of the musculoskeletal system share common problems and the interchange of information between both veterinary and human orthopaedics is very important. Therefore treating animals is not only ethical in its own right but is a useful paradigm for human orthopaedics.

"Treating Mitzi with an ITAP device has proved to be beneficial and the information learned from this case has been directly applied to human surgery.  Mitzi's ITAP is made from titanium alloy which is attached to the residual bone. The surface of the implant is coated with hydroxyapatite which enhances bone attachment, securing the implant in place. Part of the implant just underlying the skin has a surface which encourages dermal and epidermal attachment. This ties the skin into the implant and produces a seal preventing infection. This implant has been adopted for human use."

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