Targeted Muscle Reinnervation: Introduction - Rehabilitation Institute of Chicago

Skip to Content

Targeted Muscle Reinnervation: A Neural Interface for Artificial Limbs

Targeted Muscle Reinnervation: A Neural Interface for Artificial Limbs (CRC Press, 2013) can be purchased at the CRC Press website or on Amazon.

RIC Center for Bionic Medicine

TMR research was pioneered at the Center for Bionic Medicine (CBM). The CBM combines science, engineering, and clinical skill to improve function and life quality for persons with limb loss.

Development of this website was supported by the National Library of Medicine of the National Institutes of Health, Award Number G13LM011221. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Introduction to Targeted Reinnervation



An estimated 41,000 people in the United States live with amputations at or above the wrist. Many more people are affected by arm amputation throughout the world.

Loss of an arm causes a severe disability. Simply put, our hands and arms are incredible tools; arm amputation affects the ability to perform daily tasks and often the emotional well-being of the individual.

The most common reason for arm amputation is trauma, such as industrial accidents or combat-related injuries. Many individuals with upper-limb amputations are active, young adults who must spend decades living without their arm or hand.

Dysvascular disease and cancer are less common causes of arm loss; and although rare, congenital limb deficiency affects the upper limb more than 50% of the time.

The optimal treatment for arm loss is to use a prosthetic arm; however, the dexterity and functionality of the intact hand and arm set high expectations for arm prostheses;and pose the technological challenge of developing devices that are both functional and easy to control.

Types of Prostheses

This video was produced thanks to generous support
from the McCormick Foundation.

Currently, there are two main functional prosthetic options available for people with upper-limb amputations—body-powered or myoelectric (i.e., motorized) prostheses.

Improving Control of Myoelectric Prostheses

Controlling a multifunctional prosthesis requires a neural interface that can record motor commands intended for the missing limb, decipher the user’s intended movements, and command the prosthetic arm.

There are two obvious places to create this interface: the brain (brain-machine/brain-computer interfaces) or the peripheral nerves (peripheral nerve interfaces). There are, however, many significant challenges in the clinical implementation of both these interfaces. Targeted Muscle Reinnervation (TMR) is a surgical procedure that provides access to motor control information intended for the missing limb.

TMR Surgery

What is TMR? View this video to learn about the
concept of TMR.

During TMR surgery, severed arm nerves are transferred to spare target muscles in a person's residual limb or surrounding area. Over a period of months, these nerves grow into, or reinnnervate, the target muscles. Once this process is complete, the target muscles contract in response to attempted movements of the missing limb. EMG signals generated by these contractions can be used to control the prosthesis.

  • TMR makes prosthesis control more intuitive because neural control signals intended for the missing limb are used to control analogous functions in a prosthesis.
    For example, when a person attempts to bend their missing elbow, the motor control information from the brain travels down the transferred nerve and makes the target muscle contract. EMG signals from that target muscle are used to make the prosthetic elbow bend.
  • TMR also creates additional control sites so the person can use different muscles to control different prosthetic functions.

Individuals interested in TMR surgery can find further information here.

Statistics & Resources

Amputation Statistics

Cause of Upper-Limb AmputationsSource: Ziegler-Graham, et al. Estimating the prevalence
of limb loss in the United States: 2005 to 2050. Archives
of Physical Medicine and Rehabilitation. 89(3):422-429,
2008. (Click image to enlarge)

  • It is estimated that more than 1.6 million people in the United States are living with limb amputations [1].
  • Amputation causes vary greatly by level and type. Overall, the vast majority (82%) of amputations are caused by vascular disease [2], often a result of diabetes, which causes 93% of lower-limb amputations. Less frequently, lower-limb amputation is caused by trauma (5-6%) or cancer (1%). In contrast, upper-limb amputation is overwhelmingly caused by trauma (92%), followed by dysvascular disease (7%) and cancer (1%).
  • Although the incidence of upper-limb amputation is decreasing, the number of lower-limb amputations is increasing [2]and is expected to double by 2030, largely due to the aging population and the increasing incidence of diabetes.
  • Between January 2001 and July 2012, 1,221 individuals sustained major amputations as a result of combat in Iraq and Afghanistan. Most (over 85%) involved the lower limb; 229 individuals sustained upper-limb amputations. Almost 30% of individuals experienced amputation of multiple limbs[3].
  • According to a 2002 study, about 75% of persons with amputations use prostheses.

Incidence of limb amputation 1988-1996 (from [1])

 Upper LimbLower Limb

% of total
% of total
Thumb 27,021 2.3% Toe 338,288 28.5%
Finger(s) 122,272 10.3% Foot 107,837 9.1%
Hand 2,330 0.2% Ankle 8,465 0.7%
Wrist 950 0.1% Transtibial 287,295 24.2%
Transradial 5,839 0.5% Knee 5,291 0.4%
Elbow 854 0.1% Transfemoral 266,465 22.4%
Transhumeral 5,007 0.4% Hip 4,698 0.4%
Shoulder 755 0.1% Pelvic 1,890 0.2%
Bilateral 462 0.0% Bilateral 1,504 0.1%
Forequarter 586 0.0%
Total 166,076 14.0% Total 1,021,733 86.0%
  1. Ziegler-Graham K, MacKenzie EJ, Ephraim PL, Travison TG, Brookmeyer R. Estimating the prevalence of limb loss in the United States: 2005 to 2050. Archives of physical medicine and rehabilitation. Mar 2008;89(3):422-429.
  2. Dillingham TR, Pezzin LE, MacKenzie EJ. Limb amputation and limb deficiency: epidemiology and recent trends in the United States. Southern medical journal. Aug 2002;95(8):875-883.
  3. Krueger CA, Wenke JC, Ficke JR. Ten years at war: comprehensive analysis of amputation trends. The journal of trauma and acute care surgery. Dec 2012;73(6 Suppl 5):S438-444.

TMR Surgeries

TMR has been performed on more than 100 patients in hospitals around the world, including:

Northwestern Memorial Hospital

Walter Reed National Military Medical Center

San Antonio Military Medical Center (formerly Brooke General Hospital)

Johns Hopkins Medicine

Southern Illinois University School of Medicine

Medical University of Vienna

Additional Resources

Amputee Coalition

Centers for Disease Control


RIC TMR page (for patients)


RIC's Todd KuikenTodd A. Kuiken, MD, PhD, began studying nerve transfers with the intention of producing new EMG signals for control of myoelectric prosthetic arms while in graduate school. Years of animal work and EMG simulation studies resulted in the first human nerve transfer surgery intended to improve prosthesis control, in 2002. The technique, called targeted muscle reinnervation (TMR), was successful and has since become an established clinical procedure, benefiting many patients across the US and overseas.

Dr. Kuiken leads an interdisciplinary team that includes physicians, prosthetists, therapists, neuroscientists, engineers, software developers, graduate students, and post-doctoral researchers at the Center for Bionic Medicine within the Rehabilitation Institute of Chicago. This combination of clinical and research expertise provides a unique environment in which to understand and develop TMR and to translate research data into clinical applications. Four integrated research groups within the Center for Bionic Medicine seek to study the functional and sensory benefits of TMR, to develop lighter, more functional prosthetic devices, and to design control systems to capitalize on the vast neural information made available by TMR. TMR has continued to evolve and improve, in particular with recent collaborative research on pattern recognition control. Dr. Kuiken has continued to lead efforts to understand and capitalize on the potential of TMR to improve prosthetic function.

Dr. Kuiken received a BS in biomedical engineering from Duke University, and a PhD in biomedical engineering and an MD from Northwestern University. He completed a residency in physical medicine and rehabilitation at the Rehabilitation Institute of Chicago and Northwestern University Medical School. In addition to leading the Center for Bionic Medicine, Dr. Kuiken is Director of Amputee Services at the Rehabilitation Institute of Chicago. He is also a Professor in the Departments of Physical Medicine and Rehabilitation, Surgery, and Biomedical Engineering at Northwestern University. Dr. Kuiken is the recipient of many awards and honors for his work on TMR and is an internationally respected leader both in research and the clinical care of people with limb loss.