Skip to Content

Research

The Center for Bionic Medicine has many completed and ongoing projects. The focus of our research is to improve the control of artificial limbs.

  1. Overview of Accomplishments with Targeted Reinnervation

  2. Clinical Application of Targeted Reinnervation in Transradial Amputees

  3. Advanced Signal Processing Methods to Enhance Prosthetic Limb Control with Targeted Reinnervation

  4. Quantification of Targeted Sensory Reinnervation

  5. Neural Plasticity after Targeted Reinnervation

  6. Clinical Training and Outcome Measures for Upper Limb Prostheses

  7. Development of Neural Interfaces for Lower Limb Prostheses

Overview of Accomplishments with Targeted Reinnervation


Clinical Application of Targeted Reinnervation in Shoulder Disarticulation Amputees

Reinnervation in Shoulder Disarticulation Amputees

Targeted reinnervation surgery has been performed successfully on shoulder disarticulation (SD) amputees and is now a clinically available option for them.  In SD patients, targeted reinnervation involves the connection of the residual brachial plexus nerves, which carry the neural information to and from the arm, to the pectoral muscles of the chest. The musculocutaneous, median, radial and ulnar nerves of the brachial plexus are used for reinnervation. The musculocutaneous nerve normally innervates elbow flexors such as the biceps muscle.  The median nerve normally innervates wrist, palm and finger flexors, wrist pronator muscles, and intrinsic hand muscles. The radial nerve normally innervates elbow extensor muscles, such as the triceps muscle, as well as the wrist and finger extensors of the forearm.  Finally, the ulnar nerve innervates wrist and finger flexors as well as many intrinsic hand muscles.  Depending on the anatomy, additional muscles such as the serratus anterior muscle and the latissimus muscle may also be used.  It takes several months for the nerves and muscles to form functional connections. Eventually, neural commands intended for the missing limb are successfully routed to the new target muscles.  This results in contractions of the target muscles when the patient attempts to move his/her missing limb (view Targeted Reinnervation Effect on Chest Muscle Movement).

Summary of Findings from NICHD-Funded Contract

CBM recently completed a 5-year research project funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). In this study, we performed the first targeted muscle reinnervation (TMR) surgery on a woman, a functional shoulder-disarticulation amputee. We attempted new surgical techniques to further increase the number of myoelectric control sites made available while minimizing cosmetic consequences. Four functional control sites were obtained, significantly improving prosthesis control. High-density EMG recordings indicated that even more neural control information was available for extraction, and pattern recognition techniques were implemented to allow intuitive control of an advanced multifunction prosthesis.

As a part of this project, we also performed the first intentional transfer of sensory nerves, termed targeted sensory reinnervation (TSR), to achieve sensation referred to the missing limb, called transfer sensation (see Quantification of Targeted Sensory Reinnervation below). As a result, the patient in this study had near-normal sensory thresholds for touch, temperature, electrical stimulation, graded pressure, and point localization, indicating reinnervation of different sensory end organs. In addition, the use of sensory feedback was shown to enhance perceptual ownership of a prosthesis.

Neural mechanisms involved in transfer sensation were investigated in human targeted reinnervation subjects and in a rat targeted reinnervation model: sensory representations of the missing limb were reestablished in the sensorimotor cortex, indicative of both central and peripheral neural plasticity (see Neural Plasticity after Targeted Reinnervation below).

Targeted reinnervation and transfer sensation show immense potential to restore both motor and sensory capability to upper limb amputees.

Clinical Application of Targeted Reinnervation in Transhumeral Amputees

Targeted reinnervation has also been performed successfully on transhumeral amputees and is a clinically  available option for them as well.  For transhumeral amputees, the surgery involves changing the innervation of two muscles of the upper arm, the short head of the biceps and either the brachialis or the lateral head of the triceps. The original innervation of these target muscles is cut and the median and distal radial nerves* are connected. The innervation of the lateral biceps (elbow flexion) by the musculocutaneous nerve and the remaining triceps (elbow extension) by the proximal radial nerve are left intact.  Due to the limited number of available muscle sites, the ulnar nerve has not yet been reconnected during targeted reinnervation on transhumeral amputees.

Prosthesis Control

The electrical signals generated by contractions of the reinnervated muscles (or a combination of reinnervated and native muscles) can be recorded using surface electrodes and used to control an artificial limb.  The prosthesis is initially controlled using conventional or “direct” control.  Here, one electrode pair placed over each muscle is responsible for controlling a single motion of the prosthesis (e.g. elbow flexion or hand open/close).  The surgery generally results in four independent myoelectric controls sites which correspond directly to prosthesis movements and are therefore intuitively controlled by the patient (prior to targeted reinnervation surgery, only one to two myoelectric control sites are available and in the case of shoulder disarticulation amputees, these sites are physiologically unrelated to the prosthesis movements).  A more complex control scheme using additional electrodes and pattern recognition algorithms allows for the control of additional and more complex prosthesis movements, such as hand grasping patterns (see Advanced Signal Processing Methods to Enhance Prosthetic Limb Control with Targeted Reinnervation ). 

Functional Outcomes

Several measures are used to assess the performance of targeted reinnervation subjects following recovery and training with their new prosthesis (see Clinical Training and Outcome Measures for Upper Limb Prostheses ).  Subjects show improved performance with their new control scheme.  For instance, subjects have shown two and three-fold improvements on the box and blocks test as well as increased speed on the clothespin relocation test.  AMPS testing on one subject revealed an increase from 0.3 to 1.98 for motor skills and 0.9 to 1.98 for process skills.  Patients report that they are able to perform tasks previously impossible for them prior to reinnervation surgery.  For a bilateral shoulder disarticulation subject who underwent targeted reinnervation and subsequent fitting and testing, these tasks included taking out the garbage, putting on a hat, vacuuming and shaving.  

Related Publications

Dumanian GA, Ko JH, O'Shaughnessy KD, Kim PS, Wilson CJ, and Kuiken TA. Targeted reinnervation for transhumeral amputees: current surgical technique and update on results, Plast Reconstr Surg, 124(3):863-9, Sept 2009.

Miller LA, Stubblefield KA, Lipschutz RD, Lock BA and Kuiken TA. Improved myoelectric prosthesis control using targeted reinnervation surgery: a case series, IEEE Trans Neural Sys Rehab Eng., 16(1):46-50, Feb 2008.

Kuiken TA, Miller LA, Lipschutz R, Lock B, Stubblefield K, Marasco P, Zhou P and Dumanian G. Targeted reinnervation for enhanced prosthetic arm function in a woman with a proximal amputation, Lancet, 369(9558):371-80, Feb 2007.

Hijjawi JB, Kuiken TA, Lipschutz, RD, Miller LA, Stubblefield KA and Dumanian GA.  Improved myoelectric prosthesis control accomplished using multiple nerve transfers, Plast Reconstr Surg., 118(7):1573-78, Dec 2006.

Lipschutz RD, Kuiken TA, Dumanian GA, Miller LA Dumanian GA, and Stubblefield KA. Shoulder disarticulation externally powered prosthetic fitting following targeted muscle reinnervation for improved myoelectric prosthesis control,  J Prosthet Orthot., 18(2):28-34, Apr 2006.

Kuiken TA Dumanian GA, Lipschutz RD, Miller LA and Stubblefield KA. The use of targeted muscle reinnervation for improved myoelectric prosthesis control in a bilateral shoulder disarticulation amputeeProsthet Orthot Int., 28(3):245-253, December 2004.

Clinical Application of Targeted Reinnervation in Transradial Amputees


We are just beginning to extend targeted reinnervation to transradial amputees.  Because transradial amputation is the most common type, this application could potentially benefit thousands of amputees.  Targeted reinnervation in a transradial amputee would be a simple surgical procedure to transfer the residual nerves from the intrinsic hand muscles to remaining forearm muscles.  This has the promise of giving the amputee intuitive control over the prosthetic wrist and hand, with the potential to control multiple degrees of wrist movement and more complicated grasping patterns. 

Related Publications

Li G, Schultz AE, and Kuiken TA. Quantifying pattern recognition-based myoelectric control of multifunctional transradial prostheses, IEEE Trans Neural Sys Rehab Eng, 18(2):185-92, Apr 2010.

Advanced Signal Processing Methods to Enhance Prosthetic Limb Control with Targeted Reinnervation


Deciphering Neural Control Information

Deciphering Neural Control Information

A major task in improving prosthetic limb control with targeted reinnervation is to determine how much information can be extracted from the reinnervated muscles. High-density electrogmyogram (EMG) signals are collected with >100 electrodes placed over reinnervated muscles while subjects attempt different movements. The amplitude maps of these recordings demonstrate clear changes in muscle activation patterns with different intended movements.

Electrocardiogram (ECG) signals contaminate the EMG signals of shoulder disarticulation targeted reinnervation subjects; therefore, improved techniques are needed to remove them. Adaptive filters and clipping filters have been developed and successfully implemented to remove ECG contamination in real-time. 

Pattern classification methods are applied on high-density EMG recordings to match the muscle activation patterns with the intended movements. Over 90% classification accuracy can be obtained in deciphering between 16 different intended upper-limb movements, including thumb and finger movements.

Channel Reduction and Real-Time Control of Prostheses

Although high-density EMG recordings provide the maximum amount of control information available from the reinnervated muscles, this technique is not clinically feasible.  Channel reduction algorithms can be used to reduce the number of electrodes needed to preserve the necessary neural control information. We have found that sufficient information for accurate classification can be extracted by 8 to 12 strategically placed electrodes.

A real-time pattern recognition-based prosthesis control system has been developed in collaboration with the Institute of Biomedical Engineering at the University of New Brunswick (UNB) which uses up to 16 optimally placed EMG electrodes as inputs. The intended movement of the user can be decided up to every 30 ms using an algorithm which classifies the signals recorded on the EMG channels. The speed of the motor which controls the corresponding joint on the prosthesis is proportionally controlled by the magnitude estimation involving all EMG signals. We are currently working to improve the classification algorithms and make them adaptable and more robust to slight changes in electrode location, environmental conditions, and changes in muscle contraction patterns over time.        

A 2-dimensional virtual reality system created at UNB includes an arm with a three degree of freedom (DOF) shoulder, one DOF elbow, three DOF wrist, and hand capable of seven different grasping patterns.  The system is used to test real-time control algorithms.  This is an efficient way to assess the functionality and usability of each new design.  It also allows subjects to practice real-time control without a prosthesis.

Real-time control of prostheses with targeted reinnervation is also tested using multifunctional prosthetic arms.  We collaborate in the testing of state-of-the-art prosthetic arms developed outside of the RIC. This contributes to the future design of prosthetic arms, the development of control schemes for use with targeted reinnervation, and the continued care of our patients.

Related Publications

Huang H, Zhou P, Li G, and Kuiken TA. Spatial filtering improves EMG classification accuracy following targeted muscle reinnervation, Ann Biomed Eng, 37(9):1849-57, Sept 2009. 

Sensinger JW, Lock BA, and Kuiken TA. Adaptive pattern recognition of myoelectric signals: exploration of conceptual framework and practical algorithms, IEEE Trans Neural Sys Rehab Eng, 17(3):270-8, June 2009.

Huang H, Zhou P, Li G and Kuiken TA. An analysis of EMG electrode configurations for targeted muscle reinnervation based neural machine interface, IEEE Trans Neural Sys Rehab Eng., 16(1):37-45, Feb 2008.

Zhou P, Lowery M, Englehart K, Huang H, Li G, Hargrove L, Dewald J and Kuiken TA. Decoding a new neural-machine interface for control of artificial limbs, J Neurophysiol., 97(5), Nov 2007.

Zhou P, Lock B and Kuiken TA. Real time ECG artifact removal for myoelectric prosthesis control, Physiol Meas., 28(4):397-413, Apr 2007.

Zhou P, Kuiken TA.  Eliminating cardiac contamination from myoelectric control signals developed by targeted muscle reinnervation, Physiol Meas., 27(12):1311-27, Dec 2006.

Quantification of Targeted Sensory Reinnervation


Quantification of Targeted Sensory Reinnervation

After targeted reinnervation surgery, patients slowly develop new sensations in the skin overlying their reinnervated muscles.  After several months, stimulation of this skin reliably results in the perception that their missing limb is being touched.  We have termed this phenomenon "transfer sensation," and are investigating it in order to better understand the mechanisms of sensory reinnervation as well as to define design requirements for prosthetic feedback devices.

Each patient who has developed transfer sensation is tested repeatedly in an effort to map the referred sensation on his or her reinnervated skin as well as to find the pressure threshold at which these referred sensations are first perceived.

Subjects are also tested on their reinnervated skin to determine the just-noticeable difference in forces they can perceive at different baseline levels, their ability to perceive the difference between a sharp or blunt stimulus, the threshold at which they can first perceive high and low frequency vibrations, their ability to detect hot and cold stimuli, and the smallest electrical current at which they first experience transfer sensation.

Related Publications

Sensinger JW, Schultz AE, and Kuiken TA. Examination of force discrimination in a human upper limb amputees with reinnervated limb sensation following peripheral nerve transfer, IEEE Trans Neural Sys Rehab Eng, 17(5):438-44, Oct 2009.

Marasco PD, Schultz AE, and Kuiken TA. Sensory capacity of reinnervated skin after redirection of amputated upper limb nerves to chest, Brain, 132(6):1441-48, June 2009.

Schultz AE, Marasco PD, and Kuiken TA. Vibrotactile detection thresholds for chest skin of amputees following targeted reinnervation surgery, Brain Res, 1251:121-29, Jan 2009.

Kuiken TA, Marasco PD, Lock B, Harden RN and Dewald JPA.  Redirection of cutaneous sensation from the hand to the chest skin of human amputees with targeted reinnervation, PNAS, 104(50):20061-20066, Dec 2007

Neural Plasticity after Targeted Reinnervation


Studies are underway in collaboration with Dr. Julius Dewald  and the NeuroImaging and Motor Control Lab to map the brain activity of amputees before and after targeted reinnervation surgery. The effect of re-routing the sensory and motor nerves of the hand on the cortical representations of these areas is not yet understood. This paradigm offers a new opportunity for investigating cortical plasticity in adults. In addition, studies using the rat model of TMR have allowed electrophysiological studies to be undertaken to investigate neural plasticity following targeted reinnervation.

Related Publications

Marasco PD and Kuiken TA. Amputation with median nerve redirection (targeted reinnervation) reactivates forepaw barrel subfield in rats, J Neuroscience, 30(47):16008-16014, Nov 2010.

Clinical Training and Outcome Measures for Upper Limb Prostheses


Clinical Training

Following recovery from targeted reinnervation surgery, patients are fit with a prosthesis which takes advantage of the new myoelectric control sites.  Initial training is essential for fine-tuning electrode placements and settings in the new prosthesis.  Training is important for insuring that patients take full advantage of the benefits offered by the nerve-transfer surgery.  Specifically, subjects are taught to use the direct relationship between the movements they command and the movements of the prosthesis.  Patients learn to operate multiple degrees of freedom simultaneously and to integrate the use of their prosthesis with their able arm by performing two-handed activities.  The goals of training are to increase the ease and fluidity of prosthesis use as well as to decrease the mental load required of the user.  This is ultimately expected to increasing the wearing time and usefulness of the prosthesis. 

Outcome Measures

Patients are routinely tested during visits to the NECAL lab.

Patients are routinely tested during visits to the NECAL lab during the months and years subsequent to targeted reinnervation surgery.  The goals of testing are to quantify the functional benefits offered by the procedure as well as to chart the patient’s functional improvements over time.  Subjects also help us assess the performance of new and experimental arms and new control paradigms.  Standard measures include performance on the box-and-blocks and clothespin relocation tests.  New clinical measures are continuously being assessed for possible inclusion in the standard testing procedure. 

Related Publications

Stubblefield KA, Miller LA, Lipschutz RD, and Kuiken TA. Occupational therapy protocol for amputees with targeted muscle reinnervation, J Rehab Res Dev, 46(4):481-88, Nov 2009.

Development of Neural Interfaces for Lower Limb Prostheses


We are currently in the process of evaluating the potential application of targeted reinnervation to the control of lower limb prostheses.    The targeted reinnervation procedure would provide access to the neural commands intended for the distal muscles of the leg lost by amputation.  These command signals would be used in conjunction with feedback from the powered leg to give the amputee more accurate and intuitive control.  Pattern recognition could be used to robustly detect a change in the user’s intended movement, e.g. from level walking to going up stairs.   

Related Publications

Huang H, Kuiken TA, and Lipschutz RD. A strategy for identifying locomotion modes using surface electromyography, IEEE Trans Biomed Eng, 51(1):65-73, Jan 2009.