Targeted Muscle Reinnervation: Surgical Techniques - Rehabilitation Institute of Chicago

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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.

Surgical Techniques for Targeted Muscle Reinnervation

Surgical Techniques

Overview

The ultimate goal of TMR surgery is to enhance an individual’s control of a myoelectric prosthesis.

Myoelectric devices are controlled by small electrical signals (EMG signals), which are generated by contraction of muscles in the residual limb. EMG signals are detected by electrodes placed on the skin surface.

EMG signals are generated in response to neural signals, sent from the brain, when the individual attempts to move their limb. These signals continue to be sent even after amputation of the limb; however, this valuable control information cannot be accessed.

TMR surgery involves transfer of severed brachial nerves to new target muscles – muscles that are biomechanically redundant because of the amputation.

After TMR, neural signals from transferred nerves cause target muscles to contract, generating new EMG control signals. TMR thus allows access to neural control information that was lost due to amputation.

Brachial plexus anatomy (Click image to enlarge)

TMR makes prosthesis control more intuitive because the transferred brachial nerves carry control signals intended for the missing limb: attempts to move the missing limb generate EMG signals that can be used to control corresponding movements in a prosthesis.

TMR surgery requires an understanding of the anatomy and functions controlled by the four major infraclavicular branches of the brachial plexus.

The four nerves involved in TMR surgery are the:

  • Musculocutaneous nerve
  • Radial nerve
  • Median nerve
  • Ulnar nerve
NerveElbow FlexionElbow Exten-
sion
Hand OpenHand CloseWrist Pron-
ation
Wrist Supin-
ation
Wrist FlexionWrist Exten-
sion
Musculo-
cutaneus N.
X
Radial N. X X X X
Median N. X X X
Ulnar N. X X X

Further Reading

Bueno RA, Jr., French B, Cooney D, Neumeister MW. Targeted muscle reinnervation of a muscle-free flap for improved prosthetic control in a shoulder amputee: case report. The Journal of hand surgery. May 2011;36(5):890-893.

O'Shaughnessy KD, Dumanian GA, Lipschutz RD, Miller LA, Stubblefield K, Kuiken TA. Targeted reinnervation to improve prosthesis control in transhumeral amputees. A report of three cases. The Journal of bone and joint surgery. American volume. Feb 2008;90(2):393-400.

Dumanian GA, Ko JH, O'Shaughnessy KD, Kim PS, Wilson CJ, Kuiken TA. Targeted reinnervation for transhumeral amputees: current surgical technique and update on results. Plastic and reconstructive surgery. Sep 2009;124(3):863-869.

Hijjawi JB, Kuiken TA, Lipschutz RD, Miller LA, Stubblefield KA, Dumanian GA. Improved myoelectric prosthesis control accomplished using multiple nerve transfers. Plastic and reconstructive surgery. Dec 2006;118(7):1573-1578.

Transhumeral

Transhumeral TMR

Key muscles for transhumeral TMR. (Click image to
enlarge)

The key muscles for transhumeral (above elbow) TMR are

  • Triceps brachii
  • Brachialis
  • Deltoid
  • Biceps brachii

Goals

TMR in transhumeral patients involves preservation of existing control sites and creation of additional control sites to provide four basic prosthetic arm functions: elbow flexion, elbow extension, hand open, and hand close. Additional control sites may also be created if possible.

During TMR, proximally based adipofascial flaps are created; this procedure thins the overlying skin flaps and provides tissue to be used as a spacer between target muscle segments. Physical separation of the target muscles allows strong, well-differentiated EMG signals to be recorded from each muscle [1].

Brief Surgical Overview (Transhumeral TMR)

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

During targeted reinnervation surgery for individuals with transhumeral amputations, two procedures, on the ventral and dorsal sides of the residual upper arm, are performed [2, 3]. See below for detailed instructions of each operative procedure.

Ventral side (download pdf)

Dorsal Side (download pdf)

References

  1. Bueno RA, Jr., French B, Cooney D, Neumeister MW. Targeted muscle reinnervation of a muscle-free flap for improved prosthetic control in a shoulder amputee: case report. The Journal of hand surgery. May 2011;36(5):890-893.
  2. O'Shaughnessy KD, Dumanian GA, Lipschutz RD, Miller LA, Stubblefield K, Kuiken TA. Targeted reinnervation to improve prosthesis control in transhumeral amputees. A report of three cases. The Journal of bone and joint surgery. American volume. Feb 2008;90(2):393-400.
  3. Dumanian GA, Ko JH, O'Shaughnessy KD, Kim PS, Wilson CJ, Kuiken TA. Targeted reinnervation for transhumeral amputees: current surgical technique and update on results. Plastic and reconstructive surgery. Sep 2009;124(3):863-869.

Shoulder Disarticulation

Shoulder Disarticulation TMR

Brief Surgical Overview

TMR surgery is more challenging in individuals with shoulder disarticulation amputations, as the precipitating injuries frequently cause greater anatomical distortion and these individuals generally have shorter donor nerve length.

Although creating a strategy before surgery may be helpful, each procedure must be individually tailored to the nervous and muscular anatomy observed intraoperatively. As a result, the surgical team should expect to diverge from the preoperative plan quite frequently. Thus flexibility and expertise in upper chest and axillary anatomy is essential for a successful procedure.

Surgical Goals

TMR for the shoulder disarticulation patient is designed to create independent myoelectric control sites for four basic prosthesis functions—hand open, hand close, elbow flexion, and elbow extension [4]. Additional sites are desirable and should be created if possible.

This is accomplished by:

  1. Identifying candidate target muscles and their motor nerve innervation.
  2. Identifying the amputated nerves as they emerge off of the brachial plexus.
  3. Denervating the target muscles.
  4. Performing the nerve transfers.
  5. Manipulating the overlying soft tissues to improve later EMG signal detection.

Nerve Transfers

Donor nerves should be transferred in this priority, achieving prosthetic function in order of importance of key functions (elbow flexion, followed by hand close, elbow extension, and finally hand open):

  1. Musculocutaneous nerve
  2. Median nerve
  3. Radial nerve
  4. Ulnar nerve (this can lead to an unpredictable pattern of reinnervation as a result of its diverse pattern of motor innervation within the hand and forearm, and is thus given the lowest priority).

If available, additional sites can be paired to wrist pronation or supination but any attempts to improve wrist function should not compromise the primary functions previously outlined.

Case Studies

As mentioned earlier, a TMR surgical plan for shoulder disarticulation amputations must be modified per patient and as necessary intraoperatively. See the case studies below to view examples of TMR procedures performed on individuals with shoulder disarticulation amputations.

Authors

Gregory Dumanian, MD

Gregory A. Dumanian, MD, is Chief and Program Director of the Division of Plastic Surgery at the Northwestern Feinberg School of Medicine, and holds professorships in Surgery, Neurosurgery, and Orthopedic surgery. Dr Dumanian obtained a BA in Chemistry from Harvard and an MD from the University of Chicago Pritzker School of Medicine. After a residency in general surgery at the Massachusetts General Hospital, Dr. Dumanian completed plastic surgery training at the University of Pittsburgh and a fellowship in hand surgery at the Curtis Hand Center in Baltimore, Maryland, and is board certified in surgery, plastic surgery, and hand surgery. His specialties include state-of-the-art reconstructive breast surgery after cancer treatment, aesthetic surgery, abdominal wall reconstruction, peripheral nerve surgery, hand surgery, and reconstructive microsurgery. Dr. Dumanian co-developed the TMR procedure and performed the first TMR surgery in a human amputee in 2002.

Jason Souza, MDJason M. Souza, MD, received a ScB in neuroscience from Brown University, and an MD from Harvard Medical School. Dr. Souza is currently completing an integrated residency in plastic and reconstructive surgery at Northwestern Feinberg School of Medicine, Chicago, IL and is a Lieutenant Commander in the Medical Corps of the United States Navy. Dr. Souza has participated in numerous TMR procedures.