Laura A. Miller

The use of targeted muscle reinnervation for improved myoelectric prosthesis control in a bilateral shoulder disarticulation amputee

A novel method for the control of a myoelectric upper limb prosthesis was achieved in a patient with bilateral amputations at the shoulder disarticulation level. Four independently controlled nerve-muscle units were created by surgically anastomosing residual brachial plexus nerves to dissected and divided aspects of the pectoralis major and minor muscles. The musculocutaneous nerve was anastomosed to the upper pectoralis major; the median nerve was transferred to the middle pectoralis major region; the radial nerve was anastomosed to the lower pectoralis major region; and the ulnar nerve was transferred to the pectoralis minor muscle which was moved out to the lateral chest wall. After five months, three nerve-muscle units were successful (the musculocutaneous, median and radial nerves) in that a contraction could be seen, felt and a surface electromyogram (EMG) could be recorded. Sensory reinnervation also occurred on the chest in an area where the subcutaneous fat was removed. The patient was fitted with a new myoelectric prosthesis using the targeted muscle reinnervation. The patient could simultaneously control two degrees-of-freedom with the experimental prosthesis, the elbow and either the terminal device or wrist. Objective testing showed a doubling of blocks moved with a box and blocks test and a 26% increase in speed with a clothes pin moving test. Subjectively the patient clearly preferred the new prosthesis. He reported that it was easier and faster to use, and felt more natural.

Targeted reinnervation for enhanced prosthetic arm function in a woman with a proximal amputation: a case study

BACKGROUND The function of current artificial arms is limited by inadequate control methods. We developed a technique that used nerve transfers to muscle to develop new electromyogram control signals and nerve transfers to skin, to provide a pathway for cutaneous sensory feedback to the missing hand. METHODS We did targeted reinnervation surgery on a woman with a left arm amputation at the humeral neck. The ulnar, median, musculocutaneous, and distal radial nerves were transferred to separate segments of her pectoral and serratus muscles. Two sensory nerves were cut and the distal ends were anastomosed to the ulnar and median nerves. After full recovery the patient was fit with a new prosthesis using the additional targeted muscle reinnervation sites. Functional testing was done and sensation in the reinnervated skin was quantified. FINDINGS The patient described the control as intuitive; she thought about using her hand or elbow and the prosthesis responded appropriately. Functional testing showed substantial improvement: mean scores in the blocks and box test increased from 4.0 (SD 1.0) with the conventional prosthesis to 15.6 (1.5) with the new prosthesis. Assessment of Motor and Process Skills test scores increased from 0.30 to 1.98 for motor skills and from 0.90 to 1.98 for process skills. The denervated anterior chest skin was reinnervated by both the ulnar and median nerves; the patient felt that her hand was being touched when this chest skin was touched, with near-normal thresholds in all sensory modalities. INTERPRETATION Targeted reinnervation improved prosthetic function and ease of use in this patient. Targeted sensory reinnervation provides a potential pathway for meaningful sensory feedback.

Improved Myoelectric Prosthesis Control Using Targeted Reinnervation Surgery: A Case Series

Targeted reinnervation is a surgical technique developed to increase the number of myoelectric input sites available to control an upper-limb prosthesis. Because signals from the nerves related to specific movements are used to control those missing degrees-of-freedom, the control of a prosthesis using this procedure is more physiologically appropriate compared to conventional control. This procedure has successfully been performed on three people with a shoulder disarticulation level amputation and three people with a transhumeral level amputation. Performance on timed tests, including the box-and-blocks test and clothespin test, has increased two to six times. Options for new control strategies are discussed.

Improved myoelectric prosthesis control accomplished using multiple nerve transfers

Background: The control of shoulder-level disarticulation prostheses is significantly more difficult than that of prostheses for more distal amputations. Amputees have significant difficulties coordinating the separate functions of prosthetic shoulder, elbow, wrist, and hand/hook components. The user must lock one joint at a particular position in space before subsequently moving a different joint. Methods: A patient with bilateral humeral disarticulations after an electrical injury underwent a novel nerve transfer procedure designed to improve the control of a myoelectric prosthesis. The median, radial, ulnar, and musculocutaneous nerves were transferred to the nerves of segments of the pectoralis major and minor muscles. Those muscles then act as bioamplifiers of peripheral nerve signals when the normal upper extremity nerves are activated by the patient’s brain. Therefore, when the patient thinks “flex elbow,” the transferred musculocutaneous nerve fires, and a segment of the pectoralis major contracts. An electromyographic signal is then detected transcutaneously and causes the prosthetic elbow to flex. Results: Three of the four nerve transfers were successful. One of the nerve transfers unexpectedly yielded two separate controllable muscle segments. Standardized testing using a “box-and-blocks” apparatus was performed with the patient’s previous myoelectric device and the current device after nerve transfers. The patient’s performance improved by 246 percent. Conclusions: Nerve transfers to small muscle segments are capable of creating a novel neural interface for improved control of a myoelectric prosthesis. This is done using standard techniques of nerve and flap surgery, and without any implantable devices.

Targeted reinnervation to improve prosthesis control in transhumeral amputees. A report of three cases.

Controlling an upper-limb prosthesis is challenging for transhumeral amputees. A central problem is the inability to move multiple prosthetic joints at the same time. With a body-powered prosthesis, an amputee uses shoulder motion to sequentially move the prosthetic elbow and lock it in place before switching to operation of the wrist, hand, or hook. With a myoelectric prosthesis, surface electromyographic signals from the residual biceps and triceps are used to control a motorized arm. Again, sequential control is required, as the biceps and triceps can only operate one joint at a time. The use of these prostheses rarely becomes intuitive. The patient is forced to use chest, shoulder girdle, or upper-arm muscles to move the prosthetic elbow, wrist, and hand in a slow, complex, and burdensome manner. Often, expensive prostheses are left untouched in the patients closet because the sequence of movements that is required to effectively use the prosthetic arm actions does not occur in a workable time frame for the patient. Use of a prosthetic arm will become more intuitive and facile if the nervous-system signals that formerly controlled arm movement can once again be used to direct the movement of the prosthesis. To date, most efforts at neural control have focused on brain-machine interface strategies in which electrodes implanted in the cerebral cortex1,2 and on peripheral nerve interfaces make use of electrode arrays placed in the amputated nerves of the arm3,4. These systems face the challenges of weak signals, signal instability over time, potential infections from implanted devices, implant-device failure, and difficulties with extracting the electrical signals to detectors outside the body. The ideal interface between patient and prosthesis would not break, become infected, need a power source, or require repeated trips to the operating room. Through the process of …

Control of a Six Degree-of-Freedom Prosthetic Arm after Targeted Muscle Reinnervation Surgery

OBJECTIVES To fit and evaluate the control of a complex prosthesis for a shoulder disarticulation-level amputee with targeted muscle reinnervation. DESIGN One participant who had targeted muscle reinnervation surgery was fitted with an advanced prosthesis and his use of this device was compared with the device that he used in the home setting. SETTING The experiments were completed within a laboratory setting. PARTICIPANT The first recipient of targeted muscle reinnervation: a bilateral shoulder disarticulation-level amputee. INTERVENTIONS Two years after surgery, the subject was fitted with a 6 degree of freedom (DOF) prosthesis (shoulder flexion, humeral rotation, elbow flexion, wrist rotation, wrist flexion, and hand control). Control of this device was compared with that of his commercially available 3-DOF system (elbow, wrist rotation, and powered hook terminal device). MAIN OUTCOME MEASURE In order to assess performance, movement analysis and timed movement tasks were executed. RESULTS The subject was able to independently operate all 6 arm functions with good control. He could simultaneously operate 2 DOF of several different joint combinations with relative ease. He operated up to 4 DOF simultaneously, but with poor control. Work space was markedly increased and some timed tasks were faster with the 6-DOF system. CONCLUSIONS This proof-of-concept study shows that advances in control of shoulder disarticulation-level prostheses can improve the quality of movement. Additional control sources may spur the development of more advanced and complex componentry for these amputees.

Summary and Recommendations of the Academyʼs State of the Science Conference on Upper Limb Prosthetic Outcome Measures

The Academys Ninth State of the Science Conference included a group of engineers, prosthetists, and therapists brought together to discuss upper limb prosthetic outcome measures. After a presentation of the evidence based review and discussions on the history of the field and the various perspectives from the various professions, the panel reviewed those outcome measures found to be recommended and those thought to be worth consideration by the Evidence Based Review and the Upper Limb Prosthetics Outcome Measures Group. Outcome measures with the potential to address certain research questions are identified. Throughout the various discussions of the SSC group, a list was kept of commonly identified issues, questions, and missing links. From this list, the panel identified seven key research priority questions. These priority questions and items included in the discussions are presented.

Prosthetic Command Signals Following Targeted Hyper-Reinnervation Nerve Transfer Surgery

High-level upper-limb amputations result in prostheses with many degrees-of-freedom to be controlled, with very few control signals. A novel method for the control of myoelectric upper limb prostheses has been developed. By transferring the residual nerves to spare muscles in or near the residual limb, additional myoelectric control signals are created that allow the simultaneous control of multiple degrees-of-freedom in the prostheses. Since the nerve function correlates physiologically to the prosthetic function, operation is more natural and thus easier than current control paradigms. This surgical procedure and subsequent prosthetic fitting have been successfully completed on one shoulder disarticulation and one transhumeral amputee. The shoulder disarticulation amputee has also been fit with a unique 6 motor system, allowing him to control 3 motors (hand, elbow, and humeral rotator) with the use of 6 myoelectric signals; there was marked increase in functional range-of-motion. He was able to control multiple joints simultaneously and could perform tasks that he could not do before, including reaching out to pick up objects

Occupational therapy protocol for amputees with targeted muscle reinnervation

Targeted muscle reinnervation (TMR) is a surgical intervention to improve the control of myoelectric prostheses in high-level upper-limb amputation. This article briefly describes the procedure and presents the protocol for postoperative, preprosthetic care. We also recommend a guide to patient training using standard-of-care prosthetic devices controlled by up to four intuitive, independent, and isolated myoelectric signals. We discuss the advantages of this new control paradigm and methods for optimizing clinical outcomes for patients with high-level upper-limb amputations. This material is based on more than 6 years of experience treating patients with TMR in a research setting. Detailed results of this research are reported elsewhere.

Shoulder disarticulation externally powered prosthetic fitting following targeted muscle reinnervation for improved myoelectric control

Functional prosthetic restoration is challenging for individuals with high-level upper extremity amputations. It is of greater consequence when the individual has sustained bilateral limb loss. It is possible to denervate expendable regions of muscle in or near an amputated limb and transfer the residual peripheral nerves to this muscle. The surface EMG signals from the reinnervated muscle can then be used as additional control signals for an externally powered prosthesis. This technique, called “targeted reinnervation,” allows the simultaneous control of multiple degrees of freedom in a prosthesis. Control of the prosthesis is also easier and more natural because the myoelectric signals are physiologically correlated to the movements of the lost arm and could greatly improve the function of myoelectric prostheses. The authors describe the first application of targeted reinnervation to a man with bilateral shoulder disarticulation amputations, with a focus on the prosthetic fitting and its challenges. The surgical procedure and preliminary outcomes are presented.