Researchers from Hannover Medical School (MHH) have developed a system that is intended to significantly extend the survival time of severed limbs and thus increase the chances of successful reattachment (replantation). A major challenge in replantation is time. Amputated limbs are cooled as standard but only survive for a few hours without blood supply. However, severely injured patients often need to be stabilized before complex reattachment surgery is possible. It could also reduce the need for prosthetics.
"It can sometimes take days until the patient is stable enough for another operation," explains Prof. Dr. Bettina Wiegmann. She is an emergency physician and specialist in cardiac surgery at MHH and has already been working on such a system for years. A study titled "Ex-vivo limb perfusion in military and civilian medicine: inspired by ex-vivo organ perfusion, pioneered for traumatic limb amputation and peripheral nerve regeneration" has now been published in the journal Military Medical Research.
To bridge this critical time, Wiegmann and Prof. Dr. med. vet. Kirsten Haastert-Talini from the MHH Institute of Neuroanatomy and Cell Biology has developed an ex-vivo limb perfusion (EVEP). Similar to organ transplantation, the severed limb is connected to an artificial circulatory system and supplied with nutrients outside the body. "We tested different perfusion solutions on large animal limbs and gathered initial evidence from various parameters such as blood gas analysis, serum markers, thermal imaging, and joint mobility that our system functions reliably and can preserve tissue for over six hours," says Wiegmann.
The EVEP system functions similarly to a mobile organ care system already used in heart and lung transplants. The severed limb is placed in a portable box connected to a pump that circulates a special, body-warm nutrient solution through the blood vessels. This ensures the tissue continues to be supplied with oxygen and nutrients while metabolic waste products are removed. This prevents cell death due to lack of oxygen and maintains the vitality of the limb for many hours.
Research is being conducted worldwide on this topic. For example, researchers were able to successfully reattach pig limbs after 33 hours using a similar system, according to a study published in the journal Military Medicine. Researchers already demonstrated in a study in 2017 that the viability of limbs can be extended. Researchers succeeded in supplying donor arms outside the body for 24 hours for potential transplantation.
The team pays particular attention to nerve regeneration to prevent long-term consequences such as phantom pain. "Severed nerves in the limb stump can lengthen and tangle, causing phantom pain," explains Haastert-Talini. To prevent this, the environment must be prepared in such a way that the nerve fibers can grow back together in a targeted manner. This requires certain messenger substances that trigger a kind of inflammatory reaction. "Therefore, unlike in the organ care system, we do not use anti-inflammatory drugs in our limb perfusion solution," says Haastert-Talini.
According to the researchers, the instructions for the system are now ready: "The fine-tuning of our system should then allow a surgical team to care for the patient while a second team can calmly prepare the limb for replantation in parallel," says Haastert-Talini. The demand for such technology is high. "By 2025, the number of traumatic amputations is expected to increase by more than 70 percent, according to scientific studies," says Prof. Wiegmann.