Reconstructing knees with kangaroo tissue is one step, or hop, closer to being a reality, with human trials set to get under way in 2024.
“I’ve always said that kangaroos are nature’s greatest athletes,” says orthopedic surgeon Dr Nick Hartnell one of the authors of the study. “They really are the most impressive animals – they can jump lengths of up to 12 meters (39 ft), clear a three-meter (10-ft) fence and hop at 70 km/h (43 mph).
"Watching them in action, I started to wonder how much of this athletic ability was related to the way their tendons were formed, and whether they might be used to replace ruptured human ligaments,” he said.
Following years of research, Hartnell and his team are progressing towards a human xenograft trial to repair injuries such as a ruptured anterior cruciate ligament (ACL).
A xenograft, in which an organ or other tissue is transplanted from another species, is already a feature of surgeries such as replacing heart valves with those from donor pigs. However, biological compatibility is a huge barrier. The team believes it's also cracked the code on how to ensure the ‘foreign’ kangaroo tissue would not be rejected by the human recipient.
"Xenografts – using tendons from other species – have the potential to be a better option, but so far medicine has struggled both to find a suitable donor species that has strong, durable tendons that will not be rejected,” Dr Hartnell said.
While the Australian marsupial may not provide someone with superhuman jumping abilities, it does present a promising alternative to current treatment.
In the US, around 200,000 ACL ruptures occur each year, and up to a quarter of those require additional surgeries. The nature of the injury means additional tissue needs to be grafted at the injury site. Grafts taken from elsewhere on the patient’s body often increase pain and recovery time, and both those from deceased donors and synthetic sources present surgeons with other issues.
"There is a very limited supply of these cadaveric tendons available, and unfortunately the strength tends not to be as good as we would like, leaving the patient with a weaker knee,” Dr Hartnell said.
“In addition to this, up to a quarter of all ACL reconstructions fail,” he added. “If that happens, or the person has damaged two ligaments at once, or they are injured a second time, they are running out of options.”
The kangaroo tendon not only has the potential to be the best option, but could be sourced from elsewhere (culling, food production), where this part of the animal is used for pet food, if anything at all.
All of the research has been conducted on kangaroo tendons acquired from other industries, so has not involved any live animals.
"They are biologically superior as far as tendons are concerned, and currently all of that potential is just being wasted because the tendons aren't being used for anything,” Dr Hartnell added.
The team hopes a successful human trial will pave the way for the kangaroo tendons to be used in procedures worldwide.
The study was published in The American Journal of Sports Medicine.
Source: Macquarie University