Robert D. Lipschutz

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.

A Strategy for Identifying Locomotion Modes Using Surface Electromyography

This study investigated the use of surface electromyography (EMG) combined with pattern recognition (PR) to identify user locomotion modes. Due to the nonstationary characteristics of leg EMG signals during locomotion, a new phase-dependent EMG PR strategy was proposed for classifying the users locomotion modes. The variables of the system were studied for accurate classification and timely system response. The developed PR system was tested on EMG data collected from eight able-bodied subjects and two subjects with long transfemoral (TF) amputations while they were walking on different terrains or paths. The results showed reliable classification for the seven tested modes. For eight able-bodied subjects, the average classification errors in the four defined phases using ten electrodes located over the muscles above the knee (simulating EMG from the residual limb of a TF amputee) were 12.4% plusmn 5.0%, 6.0% plusmn 4.7%, 7.5% plusmn 5.1%, and 5.2% plusmn 3.7%, respectively. Comparable results were also observed in our pilot study on the subjects with TF amputations. The outcome of this investigation could promote the future design of neural-controlled artificial legs.

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.

Robotic leg control with EMG decoding in an amputee with nerve transfers

The clinical application of robotic technology to powered prosthetic knees and ankles is limited by the lack of a robust control strategy. We found that the use of electromyographic (EMG) signals from natively innervated and surgically reinnervated residual thigh muscles in a patient who had undergone knee amputation improved control of a robotic leg prosthesis. EMG signals were decoded with a pattern-recognition algorithm and combined with data from sensors on the prosthesis to interpret the patients intended movements. This provided robust and intuitive control of ambulation--with seamless transitions between walking on level ground, stairs, and ramps--and of the ability to reposition the leg while the patient was seated.

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 …

Gait characteristics of persons with bilateral transtibial amputations

The gait characteristics of persons with unilateral transtibial amputations are fairly well documented in the literature. However, much less is known about the gait of persons with bilateral transtibial amputations. This study used quantitative gait analysis to investigate the gait characteristics of 19 persons with bilateral transtibial amputations. To reduce variability between subjects, we fitted all subjects with Seattle Lightfoot II feet 2 weeks before their gait analyses. The data indicated that subjects walked with symmetrical temporospatial, kinematic, and kinetic parameters. Compared with nondisabled controls, the subjects with amputations walked with slower speeds and lower cadences, had shorter step lengths and wider step widths, and displayed hip hiking during swing phase. Additionally, compared with the nondisabled controls walking at comparable speeds, the subjects with amputations demonstrated reduced ankle dorsiflexion and knee flexion in stance phase, reduced peak ankle plantar flexor moment, reduced positive ankle power (i.e., energy return) in late stance, and increased positive and negative hip power. These results demonstrate the deficiencies in current prosthetic componentry and suggest that further research is needed to enhance prosthesis function and improve gait in persons with amputations.

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.

Real-Time Myoelectric Control of Knee and Ankle Motions for Transfemoral Amputees

33.3% of candesartan patients received 76% or more of the target dose vs 78.0% of losartan patients. For the model using 150 mg of losartan as the target dose, 33.3% of candesartan patients received 25% or more of the target dose vs 0.2% of losartan patients. The actual mean (SD) dose of candesartan was 18 (11) mg (56% [36%] of the target dose of 32 mg) and of losartan, 53 (26) mg (106% [52%] of the target dose of 50 mg and 35% [17%] of the target dose of 150 mg). Candesartan was associated with less mortality than losartan in all models, with adjustment for dose with a target of 50 mg or 150 mg, and in multivariate models with and without propensity scores. There was no interaction with dose, regardless of whether the target losartan dose was 50 mg or 150 mg. This was a retrospective analysis and not a trial, but we agree that patients were likely titrated toward 50 mg prior to the HEAAL study and 150 mg after, if it was tolerated. Our findings should be confirmed in other studies, but the suggestion that candesartan is associated with lower mortality than losartan in HF remains.