A stable recovery: Donor schemes for animals
Doctors use donor schemes to help save patients' lives. Now vets can too – and they're healing cats and dogs as well as thoroughbred horses, as Sue Corfield explains
Monday 18 July 2011
Few sporting spectacles can match the drama of 40 horses thundering at 30mph towards Becher's Brook in the Grand National.
As a horse lands after jumping one of these awe-inspiring fences, the force on its tendon has been measured at one tonne per sq cm, so it's little wonder that tendon and knee injuries are among the most common sustained by race horses. Indeed, injuries like these can mean the end of a horse's racing career, but now advances in veterinary medicine mean that a horse may once again achieve its former level of fitness.
National Hunt racehorse Dream Alliance suffered severe tendon damage during the 2008 Grand National, but following stem-cell therapy he went on to win the Welsh Grand National in 2009 and is still racing today.
Advances in veterinary medicine mean that orthopaedic surgery is becoming increasingly commonplace for animals suffering from severe disabilities and injuries.
For us humans, this is not a new concept and is used in many procedures. The NHS runs a human tissue bank, which uses tissue donated for transplant by people when they are alive or after their deaths for use in transplant procedures to treat many conditions.
For example, patients may need a transplant to replace diseased or damaged bone and tendons, heal severe wounds caused by burns, replace diseased heart valves or repair a deformity in a child's heart or to replace diseased or damaged corneas.
Now dogs, cats, horses and even more exotic species can also get a new lease of life, thanks to a tissue donation programme established by Veterinary Tissue Bank to help animals in need of tissue transplants.
Veterinary Tissue Bank, the UK's first ethical animal donor programme, has been driven forward by veterinary surgeons John Innes, professor of surgery at University of Liverpool Veterinary School and Peter Myint, who has extensive experience in managing and developing tissue banks for human procedures.
So far, the scheme has proved highly successful in helping pets and companion animals in need of life-saving and life-enhancing surgery. Cruciate ligament injuries are the most widely known, common injuries to benefit from surgery. Overweight and large dogs, such as Labradors and Rottweilers, are particularly prone to these injuries and with these breeds living longer, orthopaedic surgery is becoming more popular.
Until now, a major stumbling block to successful correction of some injuries has been finding suitable bone and tissue to graft on to the injury. As a result, most grafts had to be taken from the injured animal in a procedure known as autograft. Now, bone and soft tissue is being taken from donor pets in a method called allograft.
Tia, an eight year-old Labrador bitch, was the first pet in the UK to benefit from a cartilage knee joint transplant – a procedure known as meniscal transplant – that replaces the wedge-shaped cartilage of the knee joint using donor tissue. She had suffered a severe injury to her knee joint following a car accident last year and her vet referred her to Patrick Ridge from Devon-based Ridge Referrals.
After examination using a miniature camera inserted into the joint to visualise the extent of the damage, Ridge felt Tia was an ideal candidate for knee cartilage replacement surgery. Keyhole surgery was conducted to remove the injured tissue and insert therapeutic agents.
Veterinary Tissue Bank provided the healthy tissue for transplantation into Tia's knee joint, making her the first dog in the UK to receive a meniscal transplant. Mirroring the same principles and many of the supply problems as human tissue donation, the tissue bank needs owners to come forward to donate their deceased pets' soft tissue and bone tissue so that it can be supplied to veterinary surgeons throughout the UK and Europe for allografts.
There is an urgent need for more pet donors, especially cats, for which there is particular demand for grafts to help fracture repair.
Professor John Innes, MRCVS, veterinary medical director of Veterinary Tissue Bank, says: "Not surprisingly, consumers aren't really aware of our service or of the valuable contribution it can make to injured animals' lives.
"Veterinary surgeons are already on board with the concept and the demand for donor tissue can at times outstrip our ability to supply.
"A single donation can help as many as 50 or 60 pets. We have processed around 1,000 grafts so far and we estimate that we will need around 40 donors for the next 12 months. Our ability to fulfil this commitment depends entirely on the generosity of pet owner donors who are willing to make this gift to others." Innes explains how they extract long bones from below the elbow and knee to repair fracture injuries or to fuse joints and soft tissues, such as tendons and ligaments, to repair ruptures and cartilage in the knee. The spine and skull are not touched.
"Willing owners can donate their deceased dog or cat's tissue to benefit recipient patients and, just as in human medicine, donors are treated with the utmost respect at all times," Innes concludes.
There's no charge for owners who wish to donate their pets' tissues. Instead the vets who use them pay to cover the vast amount of processing and technical improvements involved in making the samples ready for transplants. Once tissues have been retrieved, Veterinary Tissue Bank arranges a cremation and then returns the pet's ashes to the owners.
When an owner signs on the donor register, the tissue bank contacts their vet to ask the practice to include details on the pet's medical record and owners then carry a pet donor card. When the pet dies, the owners decide if they are still agreeable to donation and if they are, the vet contacts the tissue bank and arranges collection.
Innes explains: "There's no direct benefit for people who donate, other than the knowledge that they are helping other pets who might not otherwise be able to walk properly again or who may lose a leg because they can't access a correct graft.
"This can be an enormous consolation for people who are suffering considerable grief following the loss of a beloved pet."
All potential donor animals are screened to make sure they meet strict criteria, which include a full medical history and record of vaccinations and being free of any infectious disease or cancer. These advances in veterinary medicine are also opening doors for ground-breaking treatments in horses.
Although allograft procedures are still in their infancy in the equine world, thoroughbred and sport horses, who are particularly prone to leg injuries, could benefit from the new techniques.
One of the world's leading providers of veterinary healthcare to the thoroughbred racing and breeding community, Newmarket based Rossdale & Partners, is at the leading edge of the latest veterinary advances and believes allograft techniques could mark a major milestone in equine recovery rates.
Marcus Head, veterinary surgeon and senior associate of Rossdales Diagnostic Centre, elaborates: "Subchondral cysts commonly occur in the stifle or knee area of the horse and these are painful and very difficult to treat. Traditional treatment is to operate and remove the cyst and hope that the remaining hole refills.
"Unfortunately, it doesn't always do so, which can leave the horse with permanent lameness and prematurely end its career. So the ability, through minimally invasive keyhole surgery, to graft bone tissue into that area, will significantly improve the horse's chances of making a full recovery and return to fitness.
"All types of horses can suffer bone injuries, either as a result of high speed training and racing or as a result of trauma. While the ability of vets to repair this damage has significantly improved, bone grafts could augment the current practice of using internal fixation methods (plates and screws) to improve recovery rates and convalescence times."
Stem cells prepared from the bone marrow of injured horses are already being used in the treatment of tendon and joint injuries and Head views allograft procedures as a natural progression. He explains: "One of the key factors in the use of allografts is their potential for 'off-the-shelf' treatments. Currently, I need to take a bone marrow sample and then send it to the lab for culture, a process that takes at least three weeks. If those cells were immediately available for implantation it would improve the process immeasurably."
In the future, big cats, giraffes and other zoo and safari park animals could benefit from the new techniques, allowing for less invasive surgery for treatment of injuries and therefore less risky procedures with a faster recovery time.
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