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MHH researchers want to help people with traumatic amputations by preserving their limbs until they can be reattached.
The number of traumatic amputations is rising worldwide – caused by road traffic accidents, accidents at work or during leisure activities, but also as a result of terrorist attacks or war. Only a few specialist clinics are able to perform autologous replantation on patients with often life-threatening injuries, i.e., reattaching severed limbs to the body in such a way that they regain their function completely or at least to a limited extent. In addition, the operation must be performed quickly, as the amputated limbs are stored in an ice bag as standard and can only survive for a few hours without a blood supply. Professor Dr. Bettina Wiegmann, emergency physician and specialist in cardiac surgery at the Department for Cardiac, Thoracic, Transplant, and Vascular Surgery at Hannover Medical School (MHH), and Professor Dr. Kirsten Haastert-Talini, head of the ‘Peripheral Nerve Regeneration’ working group at the Institute for Neuroanatomy and Cell Biology.
The scientists want to develop an extremity care system that, on the one hand, fits into any ambulance as a transportable storage box and gives seriously injured people the chance of a life without amputation and prostheses. On the other hand, it should be able to be used in the same way as organ transplantation to preserve donor extremities and then successfully transplant them. The scientists have now developed an initial plan for setting up such an ex vivo limb perfusion (EVEP) system, including perfusion instructions, and published it in the journal Military Medical Research.
Time plays a crucial role
‘In Germany alone, there are around 56,000 amputations every year,’ says Professor Wiegmann, head of the ‘Ex-vivo Organ Perfusion’ working group at the Lower Saxony Center for Biomedical Engineering, Implant Research and Development (NIFE), where the project funded by the Federal Ministry of Defense is based. In most cases, traumatically amputated limbs are replaced with prostheses. This is partly due to the lack of expertise in many clinics for the complicated surgical procedure of replantation, which involves treating bone fractures, reattaching blood vessels, and reconnecting nerves. On the other hand, time plays a crucial role, because the seriously injured must first be stabilized in order to survive. The limb is stored on ice until then. ‘It can sometimes take days before the patient is stable enough for further surgery,’ says the surgeon. However, the limbs do not survive this, as after a certain amount of time without blood flow, they suffer ischemic damage, in which the cells die due to a lack of oxygen.
Organ Care System model
In order to save both the lives of seriously injured patients and their limbs, the scientists are relying on a procedure that works similarly to a portable organ care system. This connects donor organs to an artificial blood circulation system via a pump, thereby maintaining organ function outside the body until transplantation. Professor Wiegmann has already successfully used such a care system many times in clinical practice on hearts and lungs. ‘We have tested different perfusion solutions on large animal extremities and collected initial evidence from various parameters such as blood gas analyses, serum markers, thermal imaging, and joint mobility that our system works reliably and can preserve tissue for over six hours,’ explains Professor Wiegmann. In order to create conditions that are as realistic as possible, the scientists planned for two hours of warm ischemia time, during which the limb is not supplied with blood or otherwise nourished. ‘ “This simulates the time between traumatic amputation and arrival at the replantation center.’
Preventing nerves from proliferating
To ensure that the limb functions as well as possible after reattachment, the research team is also focusing on the nerves for the first time worldwide. ‘Severed nerves in the limb stump can lengthen and become tangled, causing phantom pain,’ explains Professor Haastert-Talini. To prevent this from happening and to ensure that the nerves grow back together in a targeted manner, the damaged parts of the limb must first be completely broken down and the surrounding area prepared for the new nerve fibers to grow in. This requires, among other things, various messenger substances that initiate a kind of inflammatory reaction. ‘That's why, unlike in the Organ Care System, we do not use anti-inflammatory drugs in our limb perfusion solution,’ says the anatomist.
Fine-tuning as the next goal
‘The basic instructions for our EVEP are in place,’ says Professor Haastert-Talini. ‘We have the tissue supply under control and have significantly reduced the formation of harmful fluid accumulations.’ Next, the scientists want to investigate how they can improve the composition of the perfusion solution so that the nerves are optimally prepared at the same time. They also want to extend the perfusion times to allow for longer transport times. ‘The fine-tuning of our system should then enable a surgical team to care for the patient while a second team calmly prepares the limb for replantation.’ The scientists are convinced that the medical need for their development will continue to grow. ‘According to scientific studies, the number of traumatic amputations is expected to increase by more than 70 percent by 2025,’ notes Professor Wiegmann.
SERVICE:
For further information please contact Professor Dr Bettina Wiegmann, wiegmann.bettina@mh-hannover.de, and Professor Dr Kirsten Haastert-Talini, haastert-talini.kirsten@mh-hannover.de.
The original paper, ‘Ex vivo limb perfusion in military and civilian medicine: inspired by ex vivo organ perfusion, pioneered for traumatic limb amputation and peripheral nerve regeneration,’ can be found here: https://pubmed.ncbi.nlm.nih.gov/41163096/
Professor Dr Bettina Wiegmann (left) and Professor Dr Kirsten Haastert-Talini check the thermal data ...
Copyright: Karin Kaiser/MHH.
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Professor Dr Bettina Wiegmann (left) and Professor Dr Kirsten Haastert-Talini check the thermal data ...
Copyright: Karin Kaiser/MHH.
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