Innovative amputation medicine

The Innovative Amputation Medicine working group investigates the influence of innovative amputation techniques in communication with the prosthesis and therapy strategies after limb loss. Both in clinical care and in research, our aim is to be able to offer good medicine that enables people to recover both physically and socially.

Research

Nowadays, modern prosthetics is no longer just about imitating what has been lost. Rather, bionic approaches should create innovative, sustainable and resource-saving solutions. The portmanteau word bionics is made up of the terms biology and technology. For us, bionics means that we change the human being - i.e. the human biology - through an additional surgical intervention in such a way that it can communicate with the available technology in the best possible way, thus creating a completely new interface on the residual limb for the absorption of information. Bionics thus combines biology with technology, creating new care options and dimensions for people with disabilities.

Amputation remains one of the most common surgical procedures worldwide. When this focus was established within the Clinic for Trauma Surgery in 2021, we made a conscious decision with Clinic Director Prof. Dr. med. Stephan Sehmisch to synchronize innovative rehabilitation strategies and aftercare concepts with surgical treatment in the context of amputation. Research and development in this area is intended to promote holistic care, inclusive perspectives and social interaction.

The surgical innovations that we treat and scientifically investigate at the MHH in the context of primary amputation or residual limb revision include Targeted Muscle Reinnervation (TMR), Targeted Sensory Reinnervation (TSR), Regenerative Peripheral Nerve Interfaces (RPNI), Agonist-Antagonist-Myoneural Interface (AMI) and Osseointegration (OI). We explain these in brief below:

Targeted Muscle Reinnervation (TMR) & Regenerative Peripheral Nerve Interfaces (RPNI)

TMR is a treatment method developed in the early 2000s by Todd Kuiken (rehabilitation physician) and Gregory Dumanian (plastic surgeon) in Chicago to improve myoelectric prosthesis control. In a complex microsurgical procedure, a selected severed nerve in the amputation stump is redirected to muscles in the socket or near the socket that are no longer biomechanically relevant and reinnervates them. This creates a new and additional "myosignal" that can be used to control the prosthesis.
This also reduces the likelihood of the (re-)development of painful neuromas, as the growth of the sprouting nerve fibres is organized and no longer proceeds in an uncontrolled manner.

The Regenerative Peripheral Nerve Interface (RPNI) also describes a selective nerve transplantation. Compared to TMR, this procedure requires significantly less time and can also be performed by non-microsurgeons. In this procedure, a small, free, avascular, denervated muscle graft (maximum length 30-40 mm, width 15-20 mm and thickness 5-6 mm) is used. This is followed by neovascularization of the muscle graft and reinnervation through regeneration of the nerve. This process enables the formation of new neuromuscular junctions that effectively prevent the development of new symptoms of neuropathy. The use of RPNI has been shown to reduce phantom limb pain by up to 53 percent and neuroma pain by up to 71 percent.

Originally, the method was demonstrated in combination with implanted electrodes in animal models to identify muscle signals that could be used to control prostheses. It has been shown that the transplanted muscle tissue is renervated and has the potential to act as a signal transmitter in the future.

Targeted Sensory Reinnervation (TSR)

In particular, sensory feedback on the residual limb is identified as crucial for improving prosthesis control, reducing phantom pain and improving embodiment (body sensation). The so-called TSR operation can be performed to improve sensory feedback. Equivalent to the TMR technique, TSR surgery involves transposing a selected severed sensory nerve in the amputation stump. First, a specific area of skin on the amputation stump is denervated. In the next step, this denervated skin area is reinnervated using a nerve transfer of a specific sensory nerve from the amputation stump. This reinnervation means that stimulation of the operated skin area is perceived as stimulation of the original innervation area of the transposed nerve. The details of the surgical technique depend on the amputation level, as this determines which nerves and skin areas are available for the targeted reinnervation of the skin.

Agonist-antagonist-myoneural interface (AMI)

We already perform the so-called agonist-antagonist myoneuronal interface technique (AMI) for the majority of primary amputations. Here, muscles - namely the agonists (players) and antagonists (opponents) - are specifically connected to each other. This preserves the original flexion movement as with intact muscles. The aim of the developers from Boston was to restore proprioception. Proprioception describes a person's ability to perceive the position and movement of their body in space even when their eyes are closed. Proprioception is also referred to as the "6th sense". Initial research results show that the targeted connection of these muscles and feedback from the intramuscular receptors increase gait stability and grip reliability. At the same time, the transposition of the muscles leads to improved cushioning of the residual limb. The AMI technique is a reinterpretation of myodesis/myoplasty.

The AMI procedure is usually combined with one of the nerve interventions described above.

Osseointegration

An osseointegrated prosthesis is a bone-guided prosthesis. An implant is surgically inserted into the bone of the stump of the arm or leg and passed through a skin/soft tissue passage - to which the prosthesis can be docked directly. Problems associated with the socket, such as pressure points and skin problems, no longer occur. Osseoperception provides additional feedback quality through the bone anchorage. However, OI is only suitable for certain patients due to the increased risk of infection compared to a stem prosthesis.

Studies currently underway and. Cooperation partners:

Longitudinal observational study on the influence of selective nerve transfer on amputation-associated pain - Targeted Muscle Benefit (TMB), funded by the DGUV, cooperation partner BG Klinikum Duisburg (Clinic for Hand Surgery, Plastic Surgery & Center for Severe Burn Injuries):

The aim of the study is to determine whether selective nerve transfer to the lower extremity from residual limb neuropathy leads to a change in post-amputation pain, in particular phantom and neuroma pain, i.e. the "targeted muscle benefit". Furthermore, it is being investigated whether the reduction in pain affects walking ability, quality of life and occupational/social participation. This study is accompanied by an APP-based, digitalized pain diary.

"Evaluation of the rehabilitation of sarcoma patients and their care with aids and remedies - REHSa" (online patient survey):

Sarcomas are a heterogeneous group of rare, solid, malignant tumors. 70-80% of all sarcomas are soft tissue sarcomas, the remaining 20-30% are malignant bone tumors. Although sarcomas can occur almost anywhere in the body, the extremities are particularly frequently affected. The aim of this study is to investigate and evaluate the current care situation of patients with extremity sarcomas with regard to rehabilitation, follow-up treatment and the provision of aids and remedies. The study is a project within the network of the Comprehensive Cancer Center Lower Saxony (University Medical Center Göttingen & Hannover Medical School).

QR code for participation in online survey (for sarcoma patients)

Augmented and Virtual Reality in Rehabilitation, cooperation partner NeuroXR & RoutineHealth:

"Cyberful" is a VR application for injuries to the upper extremity (fractures, tendon injuries, amputations, paralysis, CRPS). As virtual physiotherapy and occupational therapy, the injured arm can be exercised in a highly specialized manner and associated pain can be treated using virtual mirror therapy, motor imagery or games in the movement exercises.

One AR-based application for the lower extremities is the Routine app from RoutineHealth.

Link to the NeuroXR website: https://www.neuroxr.de

The "Innovative Amputation Medicine" working group is an Advanced Clinician Scientist junior research group funded by the Duderstadt-based medical technology company Ottobock with the research focus "AMputatiOns- und RehaBILItationS Chirurgie Niedersachsen" (MOBILISE-N). Together with the University Medical Center Göttingen, we can analyze and work on relevant gaps in care within this framework.