Clinical Outcomes of "Paralyzed" Nerve Transfer for Treating Spinal Cord Injury: A Proof of Concept in a Human Model

Functional electrical stimulation (FES) is an option to restore function in individuals after high cervical spinal cord injury (SCI) who have limited available options for tendon or nerve transfer. To be considered for FES implantation, patients must possess upper motor neuron (UMN) type denervation in potential recipient muscles, which can be confirmed by response to surface electrical stimulation during clinical evaluation. Lower motor neuron (LMN) denervated muscles will not respond to electrical stimulation and, therefore, are unavailable for use in an FES system. Previous animal studies have demonstrated that a "paralyzed" nerve transfer of a UMN-denervated motor branch to an LMN-denervated motor branch can restore electrical excitability in the recipient. In this study, we report the indications, surgical technique, and successful outcome (restoration of M3 elbow flexion) after the first "paralyzed" nerve transfer in a human patient.

A Rare Case of Cervical Charcot After Spinal Cord Injury: A Case Report

CASE

We present a rare case of cervical Charcot disease that was diagnosed in a paraplegic patient by loss of function caudal to the original level of spinal cord injury. Clinical imaging, diagnosis, differentials, and operative management are discussed.

CONCLUSIONS

Charcot disease of the cervical spine is rare and very difficult to diagnose in the paraplegic patient population. High clinical suspicion should be maintained in these patients who demonstrate any form of neurologic deterioration, mechanical instability, or change in spinal alignment. It is often necessary to rule out infection. Spinal decompression and surgical stabilization is the treatment of choice.

Evolution of Neuroprosthetic Approaches to Restoration of Upper Extremity Function in Spinal Cord Injury

Background: Spinal cord injury (SCI) occurring at the cervical levels can result in significantly impaired arm and hand function. People with cervical-level SCI desire improved use of their arms and hands, anticipating that regained function will result in improved independence and ultimately improved quality of life. Neuroprostheses provide the most promising method for significant gain in hand and arm function for persons with cervical-level SCI. Neuroprostheses utilize small electrical currents to activate peripheral motor nerves, resulting in controlled contraction of paralyzed muscles. Methods: A myoelectrically-controlled neuroprosthesis was evaluated in 15 arms in 13 individuals with cervical-level SCI. All individuals had motor level C5 or C6 tetraplegia. Results: This study demonstrates that an implanted neuroprosthesis utilizing myoelectric signal (MES)-controlled stimulation allows considerable flexibility in the control algorithms that can be utilized for a variety of arm and hand functions. Improved active range of motion, grip strength, and the ability to pick up and release objects were improved in all arms tested. Adverse events were few and were consistent with the experience with similar active implantable devices. Conclusion: For individuals with cervical SCI who are highly motivated, implanted neuroprostheses provide the opportunity to gain arm and hand function that cannot be gained through the use of orthotics or surgical intervention alone. Upper extremity neuroprostheses have been shown to provide increased function and independence for persons with cervical-level SCI.

Restoration of reaching and grasping movements through brain-controlled muscle stimulation in a person with tetraplegia: a proof-of-concept demonstration

BACKGROUND

People with chronic tetraplegia, due to high-cervical spinal cord injury, can regain limb movements through coordinated electrical stimulation of peripheral muscles and nerves, known as functional electrical stimulation (FES). Users typically command FES systems through other preserved, but unrelated and limited in number, volitional movements (eg, facial muscle activity, head movements, shoulder shrugs). We report the findings of an individual with traumatic high-cervical spinal cord injury who coordinated reaching and grasping movements using his own paralysed arm and hand, reanimated through implanted FES, and commanded using his own cortical signals through an intracortical brain-computer interface (iBCI).

METHODS

We recruited a participant into the BrainGate2 clinical trial, an ongoing study that obtains safety information regarding an intracortical neural interface device, and investigates the feasibility of people with tetraplegia controlling assistive devices using their cortical signals. Surgical procedures were performed at University Hospitals Cleveland Medical Center (Cleveland, OH, USA). Study procedures and data analyses were performed at Case Western Reserve University (Cleveland, OH, USA) and the US Department of Veterans Affairs, Louis Stokes Cleveland Veterans Affairs Medical Center (Cleveland, OH, USA). The study participant was a 53-year-old man with a spinal cord injury (cervical level 4, American Spinal Injury Association Impairment Scale category A). He received two intracortical microelectrode arrays in the hand area of his motor cortex, and 4 months and 9 months later received a total of 36 implanted percutaneous electrodes in his right upper and lower arm to electrically stimulate his hand, elbow, and shoulder muscles. The participant used a motorised mobile arm support for gravitational assistance and to provide humeral abduction and adduction under cortical control. We assessed the participant's ability to cortically command his paralysed arm to perform simple single-joint arm and hand movements and functionally meaningful multi-joint movements. We compared iBCI control of his paralysed arm with that of a virtual three-dimensional arm. This study is registered with ClinicalTrials.gov, number NCT00912041.

FINDINGS

The intracortical implant occurred on Dec 1, 2014, and we are continuing to study the participant. The last session included in this report was Nov 7, 2016. The point-to-point target acquisition sessions began on Oct 8, 2015 (311 days after implant). The participant successfully cortically commanded single-joint and coordinated multi-joint arm movements for point-to-point target acquisitions (80-100% accuracy), using first a virtual arm and second his own arm animated by FES. Using his paralysed arm, the participant volitionally performed self-paced reaches to drink a mug of coffee (successfully completing 11 of 12 attempts within a single session 463 days after implant) and feed himself (717 days after implant).

INTERPRETATION

To our knowledge, this is the first report of a combined implanted FES+iBCI neuroprosthesis for restoring both reaching and grasping movements to people with chronic tetraplegia due to spinal cord injury, and represents a major advance, with a clear translational path, for clinically viable neuroprostheses for restoration of reaching and grasping after paralysis.

FUNDING

National Institutes of Health, Department of Veterans Affairs.

Voluntary activation of biceps-to-triceps and deltoid-to-triceps transfers in quadriplegia

The biceps or the posterior deltoid can be transferred to improve elbow extension function for many individuals with C5 or C6 quadriplegia. Maximum strength after elbow reconstruction is variable; the patient’s ability to voluntarily activate the transferred muscle to extend the elbow may contribute to the variability. We compared voluntary activation during maximum isometric elbow extension following biceps transfer (n = 5) and deltoid transfer (n = 6) in three functional postures. Voluntary activation was computed as the elbow extension moment generated during maximum voluntary effort divided by the moment generated with full activation, which was estimated via electrical stimulation. Voluntary activation was on average 96% after biceps transfer and not affected by posture. Individuals with deltoid transfer demonstrated deficits in voluntary activation, which differed by posture (80% in horizontal plane, 69% in overhead reach, and 70% in weight-relief), suggesting inadequate motor re-education after deltoid transfer. Overall, individuals with a biceps transfer better activated their transferred muscle than those with a deltoid transfer. This difference in neural control augmented the greater force-generating capacity of the biceps leading to increased elbow extension strength after biceps transfer (average 9.37 N-m across postures) relative to deltoid transfer (average 2.76 N-m across postures) in our study cohort.

Posture-Dependent Corticomotor Excitability Differs Between the Transferred Biceps in Individuals With Tetraplegia and the Biceps of Nonimpaired Individuals

BACKGROUND

Following biceps transfer to enable elbow extension in individuals with tetraplegia, motor re-education may be facilitated by greater corticomotor excitability. Arm posture modulates corticomotor excitability of the nonimpaired biceps. If arm posture also modulates excitability of the transferred biceps, posture may aid in motor re-education.

OBJECTIVE

Our objective was to determine whether multi-joint arm posture affects corticomotor excitability of the transferred biceps similar to the nonimpaired biceps. We also aimed to determine whether corticomotor excitability of the transferred biceps is related to elbow extension strength and muscle length.

METHODS

Corticomotor excitability was assessed in 7 arms of individuals with tetraplegia and biceps transfer using transcranial magnetic stimulation and compared to biceps excitability of nonimpaired individuals. Single-pulse transcranial magnetic stimulation was delivered to the motor cortex with the arm in functional postures at rest. Motor-evoked potential amplitude was recorded via surface electromyography. Elbow moment was recorded during maximum isometric extension trials, and muscle length was estimated using a biomechanical model.

RESULTS

Arm posture modulated corticomotor excitability of the transferred biceps differently than the nonimpaired biceps. Elbow extension strength was positively related and muscle length was unrelated, respectively, to motor-evoked potential amplitude across the arms with biceps transfer.

CONCLUSIONS

Corticomotor excitability of the transferred biceps is modulated by arm posture and may contribute to strength outcomes after tendon transfer. Future work should determine whether modulating corticomotor excitability via posture promotes motor re-education during the rehabilitative period following surgery.

A neural interface provides long-term stable natural touch perception

Touch perception on the fingers and hand is essential for fine motor control, contributes to our sense of self, allows for effective communication, and aids in our fundamental perception of the world. Despite increasingly sophisticated mechatronics, prosthetic devices still do not directly convey sensation back to their wearers. We show that implanted peripheral nerve interfaces in two human subjects with upper limb amputation provided stable, natural touch sensation in their hands for more than 1 year. Electrical stimulation using implanted peripheral nerve cuff electrodes that did not penetrate the nerve produced touch perceptions at many locations on the phantom hand with repeatable, stable responses in the two subjects for 16 and 24 months. Patterned stimulation intensity produced a sensation that the subjects described as natural and without "tingling," or paresthesia. Different patterns produced different types of sensory perception at the same location on the phantom hand. The two subjects reported tactile perceptions they described as natural tapping, constant pressure, light moving touch, and vibration. Changing average stimulation intensity controlled the size of the percept area; changing stimulation frequency controlled sensation strength. Artificial touch sensation improved the subjects' ability to control grasping strength of the prosthesis and enabled them to better manipulate delicate objects. Thus, electrical stimulation through peripheral nerve electrodes produced long-term sensory restoration after limb loss.

Stability and selectivity of a chronic, multi-contact cuff electrode for sensory stimulation in human amputees

OBJECTIVE

Stability and selectivity are important when restoring long-term, functional sensory feedback in individuals with limb-loss. Our objective is to demonstrate a chronic, clinical neural stimulation system for providing selective sensory response in two upper-limb amputees.

APPROACH

Multi-contact cuff electrodes were implanted in the median, ulnar, and radial nerves of the upper-limb.

MAIN RESULTS

Nerve stimulation produced a selective sensory response on 19 of 20 contacts and 16 of 16 contacts in subjects 1 and 2, respectively. Stimulation elicited multiple, distinct percept areas on the phantom and residual limb. Consistent threshold, impedance, and percept areas have demonstrated that the neural interface is stable for the duration of this on-going, chronic study.

SIGNIFICANCE

We have achieved selective nerve response from multi-contact cuff electrodes by demonstrating characteristic percept areas and thresholds for each contact. Selective sensory response remains consistent in two upper-limb amputees for 1 and 2 years, the longest multi-contact sensory feedback system to date. Our approach demonstrates selectivity and stability can be achieved through an extraneural interface, which can provide sensory feedback to amputees.

Posture-dependent changes in corticomotor excitability of the biceps after spinal cord injury and tendon transfer

Following tendon transfer of the biceps to triceps after cervical spinal cord injuries (SCI), individuals must learn to activate the transferred biceps muscle to extend the elbow. Corticomotor excitability of the transferred biceps may play a role in post-operative elbow extension strength. In this study, we evaluated whether corticomotor excitability of the transferred biceps is related to an individuals' ability to extend the elbow, and whether posture and muscle length affects corticomotor excitability after SCI and tendon transfer similarly to the nonimpaired biceps. Corticomotor excitability was assessed in twelve nonimpaired arms and six arms of individuals with SCI and biceps-to-triceps transfer using transcranial magnetic stimulation (TMS) delivered at rest. Maximum isometric elbow extensor moments were recorded in transferred arms and the fiber length of the transferred biceps was estimated using a musculoskeletal model. Across the SCI subjects, corticomotor excitability of the transferred biceps increased with elbow extension strength. Thus, rehabilitation to increase excitability may enhance strength. Excitability of the transferred biceps was not related to fiber length suggesting that similar to nonimpaired subjects, posture-dependent changes in biceps excitability are primarily centrally modulated after SCI. All nonimpaired biceps were most excitable in a posture in the horizontal plane with the forearm fully supinated. The proportion of transferred biceps in which excitability was highest in this posture differed from the nonimpaired group. Therefore, rehabilitation after tendon transfer may be most beneficial if training postures are tailored to account for changes in biceps excitability.

Implanted neuroprosthesis for assisting arm and hand function after stroke: a case study

Loss of arm and hand function is common after stroke. An implantable, 12-channel, electromyogram (EMG)-controlled functional electrical stimulation neuroprosthesis (NP) may be a viable assistive device for upper-limb hemiplegia. In this study, a research participant 4.8 yr poststroke underwent presurgical screening, surgical installation of the NP, training, and assessment of upper-limb impairment, activity limitation, and satisfaction over a 2.3 yr period. The NP increased active range of finger extension from 3 to 96 degrees, increased lateral pinch force from 16 to 29 N, increased the number of objects from 1 to 4 out of 6 that the participant could grasp and place in a Grasp-Release Test, and increased the Arm Motor Abilities Test score by 0.3 points. The upper-limb Fugl-Meyer score increased from 27 at baseline to 36 by the end of the study. The participant reported using the NP at home 3-4 d/wk, up to 3 h/d for exercise and household tasks. The effectiveness of the NP to assist with activities of daily living was dependent on the degree of flexor tone, which varied with task and level of fatigue. The EMG-based control strategy was not successfully implemented; button presses were used instead. Further advancements in technology may improve ease of use and address limitations caused by muscle spasticity.

Surgical restoration of arm and hand function in people with tetraplegia

Improved hand and arm function is the most sought after function for people living with a cervical spinal cord injury (SCI). Surgical techniques have been established to increase upper extremity function for tetraplegics, focusing on restoring elbow extension, wrist movement, and hand opening and closing. Additionally, more innovative treatments that have been developed (implanted neuroprostheses and nerve transfers) provide more options for improving function and quality of life. One of the most important steps in the process of restoring upper extremity function in people with tetraplegia is identifying appropriate candidates - typically those with American Spinal Injury Association (ASIA) motor level C5 or greater. Secondary complications of SCI can pose barriers to restoring function, particularly upper extremity spasticity. A novel approach to managing spasticity through high-frequency alternating currents designed to block unwanted spasticity is being researched at the Cleveland FES Center and may improve the impact of reconstructive surgery for these individuals. The impact of these surgeries is best measured within the framework of the World Health Organization's International Classification of Function, Disability and Health. Outcome measures should be chosen to reflect changes within the domains of body functions and structures, activity, and participation. There is a need to strengthen the evidence in the area of reconstructive procedures for people with tetraplegia. Research continues to advance, providing more options for improved function in this population than ever before. The contribution of well-designed outcome studies to this evidence base will ultimately help to address the complications surrounding access to the procedures.

Surgical treatments to restore function control in spinal cord injury

People with spinal cord injury (SCI) have a profound loss of control of their lives and abilities. Surgical procedures are of significant benefit in improving autonomy, self-care, and body function. Functional electrical stimulation (FES) is useful at higher levels of paralysis such as ASIA C5 or C6 where there are no remaining voluntary muscles for tendon transfer and can partially replace respiration, balance, and ambulation. Outcomes studies show that surgical care improves independence, strength of grasp, and measured quality of life. Those with tetraplegia should be referred for consultation for surgical reconstruction, release of contractures, consideration for neuroprostheses, and reconstruction.

Twenty year experience with implanted neuroprostheses

The long-term durability and safety of implanted devices is of great importance in the field of motor neuroprosthetics, where systems may possibly be utilized in excess of 50 years by some individuals. Neuroprosthetic systems have now been implanted in the upper extremity of spinal cord injured individuals for more than 20 years. The experience with these systems shows a high level of durability of the implanted components, particularly the stimulating electrodes and leads.

Stimulation stability and selectivity of chronically implanted multicontact nerve cuff electrodes in the human upper extremity

Nine spiral nerve cuff electrodes were implanted in two human subjects for up to three years with no adverse functional effects. The objective of this study was to look at the long term nerve and muscle response to stimulation through nerve cuff electrodes. The nerve conduction velocity remained within the clinically accepted range for the entire testing period. The stimulation thresholds stabilized after approximately 20 weeks. The variability in the activation over time was not different from muscle-based electrodes used in implanted functional electrical stimulation systems. Three electrodes had multiple, independent contacts to evaluate selective recruitment of muscles. A single muscle could be selectively activated from each electrode using single-contact stimulation and the selectivity was increased with the use of field steering techniques. The selectivity after three years was consistent with selectivity measured during the implant surgery. Nerve cuff electrodes are effective for chronic muscle activation and multichannel functional electrical stimulation in humans.

An implanted upper-extremity neuroprosthesis using myoelectric control

PURPOSE

The purpose of this study was to evaluate the potential of a second-generation implantable neuroprosthesis that provides improved control of hand grasp and elbow extension for individuals with cervical level spinal cord injury. The key feature of this system is that users control their stimulated function through electromyographic (EMG) signals.

METHODS

The second-generation neuroprosthesis consists of 12 stimulating electrodes, 2 EMG signal recording electrodes, an implanted stimulator-telemeter device, an external control unit, and a transmit/receive coil. The system was implanted in a single surgical procedure. Functional outcomes for each subject were evaluated in the domains of body functions and structures, activity performance, and societal participation.

RESULTS

Three individuals with C5/C6 spinal cord injury received system implantation with subsequent prospective evaluation for a minimum of 2 years. All 3 subjects demonstrated that EMG signals can be recorded from voluntary muscles in the presence of electrical stimulation of nearby muscles. Significantly increased pinch force and grasp function was achieved for each subject. Functional evaluation demonstrated improvement in at least 5 activities of daily living using the Activities of Daily Living Abilities Test. Each subject was able to use the device at home. There were no system failures. Two of 6 EMG electrodes required surgical revision because of suboptimal location of the recording electrodes.

CONCLUSIONS

These results indicate that a neuroprosthesis with implanted myoelectric control is an effective method for restoring hand function in midcervical level spinal cord injury.

Spiral nerve cuff electrodes for an upper extremity neuroprosthesis

Four nerve cuff electrodes were implanted in the shoulder and arm of one subject with high tetraplegia. Stimulation produced shoulder abduction, elbow flexion and extension, and wrist and finger extension. Recruitment properties were quantified using twitch EMG recruitment curves and tetanic moment measurements. The chronic qualitative 'function' of each channel of stimulation could be predicted from the intraoperative data collection. The average threshold was 11.3 +/- 9 nC and stabilized to this value over the 35 weeks of testing. The moment production of most muscles increased over the testing period due to exercise of the atrophied muscles. No muscle decreased its moment and most appeared to plateau after 15 weeks. Sensation was also evaluated since this subject had an incomplete injury and nerve stimulation was not found to painful throughout the range of muscle activation. Nerve electrodes have been shown to be a stable, effective means of activating muscles for neuroprosthetics.

Reconstruction of upper limb motor function using functional electrical stimulation (FES)

Functional electrical stimulation (FES) techniques progress by adopting the developments in computers and engineering, but complete functional reconstruction is not yet possible to be achieved. The attachment of the devices to the body can be complex, and training to handle FES is not easy. FES systems are expensive and their coverage by medical insurance is limited with the exception of a few systems. Hence, recognition of FES by the medical community is limited and as a result, it is not a common therapy. However, FES is the main method available for reconstruction of motor function, at present. The improvement in activities of daily living (ADL) of patients using FES may not only improve the patient's quality of life (QOL) but also reduce the burden to persons who look after them, and hence, secure a valuable work force. The medical insurance should support the use of FES and reduce the patients' financial burden. Studies and developments based on a close collaboration of users (patients and care-givers), persons involved in therapy (doctors and nurses), and manufactures (engineers and technicians) are necessary. In addition to FES, other methods such as therapeutic electrical stimulation (TES) for prevention of atrophy and spasms of paralytic limbs show the therapeutic potential of neuromodulation.

Human Nerve Stimulation Thresholds and Selectivity Using a Multi-contact Nerve Cuff Electrode

Testing of the recruitment properties and selective activation capabilities of a multi-contact spiral nerve cuff electrode was performed intraoperatively in 21 human subjects. The study was conducted in two phases. An exploratory phase with ten subjects gave a preliminary overview of the data and data collection process and a systematic phase with eleven subjects provided detailed recruitment properties. The mean stimulation threshold of 25 +/- 17 nC was not significantly different than previous studies in animal models but much lower than muscle electrodes. The selectivity, defined as the percent of total activation of the first muscle recruited before another muscle reached threshold, ranged from 27% to 97% with a mean of 55%. In each case, the muscle that was selectively activated was the first muscle to branch distal to the cuff location. This study serves as a preliminary evaluation of nerve cuff electrodes in humans prior to chronic implant in subjects with high tetraplegia.

Dorsal column stimulation for persistent vegetative state

Dorsal column stimulation (DCS) is described as a therapy for persistent deterioration of consciousness. The mechanism of its effect has not yet been elucidated. Various other methods, such as deep brain stimulation of the CM-p f complex, vagus nerve stimulation, and musical functional therapy, are being investigated as potential treatments of this problem. We present our series of DCS for persistent vegetative state and review the potential mechanisms of action and the relevant literature.

An implanted myoelectrically-controlled neuroprosthesis for upper extremity function in spinal cord injury

A second generation implantable neuroprosthesis has been developed which provides improved control of grasp-release, forearm pronation, and elbow extension for individuals with cervical level spinal cord injury. In addition to the capacity to stimulate twelve muscles, the key technological feature of the advanced system is the capability to transmit data out of the body. This allows the use of myoelectric signal recording via implanted electrodes, thus minimizing the required external components. Clinical studies have been initiated with a second generation neuroprosthesis that consists of twelve stimulating electrodes, two myoelectric signal recording electrodes, an implanted stimulator-telemeter device and an external control unit and transmit/receive coil. This system has now been implemented in nine arms in seven C5/C6 spinal cord injured individuals. The results from these subjects demonstrate that myoelectric signals can be recorded from voluntary muscles in the presence of electrical stimulation of nearby muscles. The functional results show that the neuroprosthesis provides significantly increased pinch force and grasp function for each subject. All subjects have demonstrated increased independence and improved function in activities of daily living. We believe that these results indicate that implanted myoelectric control is a desirable option for neuroprostheses.

Clinical applications of electrical stimulation after spinal cord injury

During the last one-half century, electrical stimulation has become clinically significant for improving health and restoring useful function after spinal cord injury. Short-term stimulation can be provided by electrodes on the skin or percutaneous fine wires, but implanted systems are preferable for long-term use. Electrical stimulation of intact lower motor neurons can exercise paralyzed muscles and reverse wasting; improve strength, endurance, and cardiovascular fitness; and may reduce the progression of osteoporosis. Other potential therapeutic uses being investigated include reduction of spasticity, prevention of deep vein thrombosis, and improvement of tissue health. Pacing of intact phrenic nerves in high tetraplegia can produce effective respiration without mechanical ventilation, allowing improved speech, increased mobility, and increased sense of well-being. Improvement of cough has also been demonstrated. Stimulation of intact sacral nerves can produce effective micturition and reduce urinary tract infection; it can also improve bowel function and erection. It is usually combined with posterior sacral rhizotomy to improve continence and bladder capacity, and the combination has been shown to reduce costs of care. Electroejaculation can now produce semen in most men with spinal cord injury. Significant achievements have also been made in restoring limb function. Useful hand grasp can be provided in C5 and C6 tetraplegia, reducing dependence on adapted equipment and assistants. Standing, assistance with transfers, and walking for short distances can be provided to selected persons with paraplegia, improving their access to objects, places, and opportunities that are inaccessible from a wheelchair. This review summarizes the current state of therapeutic and neuroprosthetic applications of electrical stimulation after spinal cord injury and identifies some future directions of research and clinical and commercial development.

Restoration of elbow extension via functional electrical stimulation in individuals with tetraplegia

Functional electrical stimulation of the triceps is a method of restoring elbow extension to individuals with paralyzed triceps. Eleven arms of individuals with cervical-level spinal cord injuries (SCIs) received a triceps electrode as an addition to a hand-grasp neuroprosthesis. Stimulation was controlled either as part of a preprogrammed pattern or via a switch or an accelerometer that was connected to the neuroprosthesis external controller. The outcome measures were (1) elbow extension moments at different elbow positions, (2) performance in controllable workspace experiments, and (3) comparison to an alternative method of providing elbow extension in these individuals--a posterior deltoid (PD) to triceps tendon transfer. Stimulated elbow extension moments in 11 arms ranged from 0.8 to 13.3 N.m. The stimulated elbow extension moments varied with elbow angle in a manner consistent with the length-tension properties of the triceps. Triceps stimulation provided a significantly stronger elbow extension moment than the PD to triceps tendon transfer. The elbow extension moment generated by the tendon transfer and triceps electrode being activated together was always greater than either method used separately. Stimulation of the long head of the triceps should be avoided in persons with weak shoulder abduction, since the long head adducts the shoulder and limits shoulder function in these cases. Statistically, elbow extension neuroprostheses significantly increased the ability to successfully reach and move an object and significantly decreased the time required to acquire an object while reaching.

Durability of implanted electrodes and leads in an upper-limb neuroprosthesis

Implanted neuroprosthetic systems have been successfully used to provide upper-limb function for over 16 years. A critical aspect of these implanted systems is the safety, stability, and-reliability of the stimulating electrodes and leads. These components are (1) the stimulating electrode itself, (2) the electrode lead, and (3) the lead-to-device connector. A failure in any of these components causes the direct loss of the capability to activate a muscle consistently, usually resulting in a decrement in the function provided by the neuroprosthesis. Our results indicate that the electrode, lead, and connector system are extremely durable. We analyzed 238 electrodes that have been implanted as part of an upper-limb neuroprosthesis. Each electrode had been implanted at least 3 years, with a maximum implantation time of over 16 years. Only three electrode-lead failures and one electrode infection occurred, for a survival rate of almost 99 percent. Electrode threshold measurements indicate that the electrode response is stable over time, with no evidence of electrode migration or continual encapsulation in any of the electrodes studied. These results have an impact on the design of implantable neuroprosthetic systems. The electrode-lead component of these systems should no longer be considered a weak technological link.

Functional Electrical Stimulation (FES) for spinal cord injury

Restoration of respiratory motion by stimulation of the phrenic nerve was investigated. Respiratory motion was restored successfully by introducing a breathing pacemaker to a patient with respiratory disturbance due to upper cervical spinal cord injury. Breathing pacemakers are considered to be more similar to physiological conditions compared to mechanical ventilators. Although the system is very expensive, its cost effectiveness may be excellent, provided that it can be used for long hours each day over an extended period. The system is effective in improving patient QOL because it dramatically increases patient mobility. From these findings, it is concluded that breathing pacemakers should be used more frequently in Japan, and that various forms of support are necessary to cope with economic and other concerns.

The influence of elbow position on the range of motion of the wrist following transfer of the brachioradialis to the extensor carpi radialis brevis tendon

BACKGROUND

In patients who have an injury of the cervical spinal cord, the brachioradialis tendon may be transferred to the extensor carpi radialis brevis tendon to restore voluntary wrist extension. We hypothesized that the active range of motion of the wrist depends on the position of the elbow after this transfer because the brachioradialis changes length substantially during elbow flexion, which implies the maximum force that the muscle can produce varies with elbow position. The objectives of this study were to determine whether the position of the elbow influences the range of motion of the wrist following transfer of the brachioradialis to the extensor carpi radialis brevis tendon and to evaluate the effect of surgical tensioning.

METHODS

The range of motion of eight wrists was assessed after brachioradialis transfer. Two positions of the elbow were tested, the passive limit of elbow extension and 120 degrees of flexion. The range of motion of the wrist was also simulated with use of a biomechanical model. Using the model, we compared the active range of motion of the wrist, with the elbow at 0 degrees and 120 degrees of flexion, following three different approaches to surgical tensioning. The simulations were also repeated to evaluate how muscle strength influences outcomes.

RESULTS

Wrist extension decreased and passive flexion increased when the elbow was flexed. Maximum wrist extension was significantly correlated with passive flexion in all subjects (r = 0.95 and p < 0.001 when the elbow was extended and r = 0.82 and p < 0.03 when the elbow was flexed). The biomechanical model suggested that tensioning the tendon transfer so that the fibers of the brachioradialis do not become excessively short when the elbow is flexed may improve outcomes. The simulations also revealed that it is more difficult to maintain a consistent wrist position with the elbow in different postures when a weaker muscle is transferred.

CONCLUSIONS

The model suggests that altering the surgical tension could improve wrist extension when the elbow is flexed. However, the ultimate result is sensitive to the strength of the brachioradialis.

Electrode fracture rates and occurrences of infection and granuloma associated with percutaneous intramuscular electrodes in upper-limb functional electrical stimulation applications

This study was performed to assess the rate of electrode fracture and to provide an account of the occurrences of infection and granuloma associated with percutaneous intramuscular electrodes implanted in upper-limb muscles. Data were reviewed on 858 electrodes implanted in 62 research participants between October 1978 and July 1998. Survival analyses showed that the probability of an electrode remaining intact within the body at 6 months after implantation is 95%, and at 1 year is 91%. The probability of the electrode surviving both the in situ period and extraction after 6 months is 78%, and after 1 year is 57%. Ten participants (16%) experienced at least one occurrence of infection or granuloma associated with in-dwelling electrodes. Five of the twenty-three total adverse medical incidents were associated with electrode fragments retained in the body; the others were associated with intact electrodes. All incidents were localized nonsystematic occurrences and were resolved by administering antibiotics, cleaning the implant site, removing electrodes, cauterizing with silver nitrate, or excising electrodes or granulomas.

Indications and future directions for upper limb neuroprostheses in tetraplegic patients: a review

The development of the upper extremity neuroprosthesis has been a challenging and rewarding contribution to the management of the SCI patient. The authors' experience and that of their clinical trial teams has verified that this technology is a strong alternative to conventional reconstruction and conservative management. In the future, even more powerful tools will emerge from the laboratory as these devices and collaborative surgical procedures evolve.

Implementation of an implantable joint-angle transducer

An implantable joint-angle transducer (IJAT) was implemented to provide command-control information from the wrist for functional neuromuscular stimulation (FNS) neuroprostheses. The IJAT uses the Hall effect to sense joint angle. The objectives of this study were to evaluate (1) chronic functionality, (2) safety and biocompatibility, (3) repeatability of the implantation procedure, and (4) clinical feasibility. Accelerated bench testing projected an operating period of over 50 years. In chronic animal experiments, stable output was obtained from three of four IJATs for periods of 10 to 19 months. Histology revealed acceptable osseointegration of the implant. The device has been implanted in human subjects for over 2 years and provides an excellent control signal for hand grasp. We conclude that this device is safe and effective for chronic human use as a control input for an implanted hand neuroprosthesis.

An advanced neuroprosthesis for restoration of hand and upper arm control using an implantable controller

An advanced neuroprosthesis that provides control of grasp-release, forearm pronation, and elbow extension to persons with cervical level spinal cord injury is described. The neuroprosthesis includes implanted and external components. The implanted components are a 10-channel stimulator-telemeter, leads and electrodes, and a joint angle transducer; the external components are a control unit and transmitter-receiver coil. The system has completed preclinical testing and has been implanted fully in 3 persons and partially in 1 person, all with tetraplegia caused by spinal cord injury at C5 and C6. The minimum follow-up time for any system component is 16 months. All subjects had improvements in grasp strength, range of motion, and ability to grasp objects and increased independence in activities of daily living. Each subject became a regular user of the neuroprosthesis and is satisfied with it. The implanted components have not caused any medical complications. The operation of the electrodes and sensors has been stable. The data show that this advanced neuroprosthetic system is safe and can provide grasping and reaching ability to individuals with cervical level spinal cord injury.

Neuroprostheses for the upper extremity

Functional electrical stimulation (FES) neuroprostheses can be used to replace lost motor and sensory function in persons with neurological disorders. FES technology has subsequently been shown effective and safe in restoring hand function in adults with spinal cord injury. The freehand system consists of an implanted receiver-stimulator, an external shoulder position sensor, and an external control unit. Commands are originated by voluntary movement of the contralateral shoulder and are measured by the sensor. There are several types of electrodes: epimysial, intramuscular, nerve cuff, and intraneural. Neuroprostheses are recommended within the context of all available reconstructive options for the upper limbs. Voluntary tendon transfers are the first choice. The clinical outcomes as measured by improvement on scales of impairment, activities of daily living, and satisfaction are rewarding. The next step in improvement of the motor function of person with spinal cord injury will be the addition of a controllable second upper extremity and the elimination of additional external hardware.

Efficacy of an implanted neuroprosthesis for restoring hand grasp in tetraplegia: a multicenter study

OBJECTIVE

To evaluate an implanted neuroprosthesis that allows tetraplegic users to control grasp and release in 1 hand.

DESIGN

Multicenter cohort trial with at least 3 years of follow-up. Function for each participant was compared before and after implantation, and with and without the neuroprosthesis activated.

SETTING

Tertiary spinal cord injury (SCI) care centers, 8 in the United States, 1 in the United Kingdom, and 1 in Australia.

PARTICIPANTS

Fifty-one tetraplegic adults with C5 or C6 SCIs.

INTERVENTION

An implanted neuroprosthetic system, in which electric stimulation of the grasping muscles of 1 arm are controlled by using contralateral shoulder movements, and concurrent tendon transfer surgery. Assessed participants' ability to grasp, move, and release standardized objects; degree of assistance required to perform activities of daily living (ADLs), device usage; and user satisfaction.

MAIN OUTCOME MEASURES

Pinch force; grasp and release tests; ADL abilities test and ADL assessment test; and user satisfaction survey.

RESULTS

Pinch force was significantly greater with the neuroprosthesis in all available 50 participants, and grasp-release abilities were improved in 49. All tested participants (49/49) were more independent in performing ADLs with the neuroprosthesis than they were without it. Home use of the device for regular function and exercise was reported by over 90% of the participants, and satisfaction with the neuroprosthesis was high.

CONCLUSIONS

The grasping ability provided by the neuroprosthesis is substantial and lasting. The neuroprosthesis is safe, well accepted by users, and offers improved independence for a population without comparable alternatives.

Reduction of costs of disability using neuroprostheses

The lifetime costs associated with spinal cord injury are substantial. Assistive technology that reduces complications, increases independence, or decreases the need for attendant services can provide economic as well as medical or functional benefit. This study describes two approaches for estimating the economic consequences of implanted neuroprostheses utilizing functional electrical stimulation. Life care plan analysis was used to estimate the costs of bladder and bowel care with and without a device restoring bladder and bowel function and to compare these with the costs of implementing the device. For a neuroprosthesis restoring hand grasp, the costs of implementation were compared to the potential savings in attendant care costs that could be achieved by the use of the device. The results indicate that the costs of implementing the bladder and bowel system would be recovered in 5 years, primarily from reduced costs of supplies, medications, and procedures. The costs of the hand grasp neuroprosthesis would be recovered over the lifetime of the user if attendant time was reduced only 2 hours per day and in a shorter time if attendant care was further reduced. Neither analysis includes valuation of the quality of life, which is further enhanced by the neuroprostheses through restoration of greater independence and dignity. Our results demonstrate that implantable neuroprosthetic systems provide good health care value in addition to improved independence for the disabled individual.

Pin reduction and fixation of volar fracture fragments of distal radius fractures via the flexor carpi radialis tendon

BACKGROUND

The objective of this study was to evaluate a technique for reduction and stabilization of residually displaced volar fragments in intraarticular distal radius fractures.

METHODS

A consecutive series of patients with AO type C3 distal radius fractures treated by one surgeon were studied. Percutaneously placed pins were placed through the flexor carpi radialis tendon to reduce and stabilize volar fracture fragments of distal radius fractures when closed reduction was unsuccessful. The goal of treatment was to achieve less than 2 mm of articular congruity. Postoperative physiotherapy was protocol-based. A validated outcome measurement was used to evaluate patients.

RESULTS

Of 117 patients, 10 met the inclusion criteria. In all patients, a successful reduction of the volar fragment was achieved with less than 2 mm of residual articular step-off. Reduction was maintained in 8 patients. Follow-up averaged 29 months, and there were no complications associated with the technique. All patients were satisfied with the treatment.

CONCLUSION

Although the final outcome of patients with this type of fracture depends on many factors, in the small series of patients described, a satisfactory reduction was possible using the describe technique. Transtendinous pinning is a new, undescribed technique that is useful in the treatment of such specific injuries.

Implantable transducer for two-degree of freedom joint angle sensing

An implantable joint angle transducer (IJAT) was developed to provide command-control and feedback-control information for chronic use with functional neuromuscular stimulation (FNS) neuroprostheses. The IJAT uses Hall effect sensors to transduce joint angle. A titanium encapsulated array of Hall effect sensors and support circuitry is surgically implanted in one bone, and a similarly encapsulated permanent magnet in an opposing bone, across a joint. The IJAT provides consistent, reliable, high quality signals that reflect joint movement from midsized two-degree-of-freedom joints. IJAT's were implanted using a chronic in vivo dog model to demonstrate the feasibility of implantation and periodic measurement techniques, and to validate modeling techniques used for prediction of function and calibration. The flexion resolution ranged from 0.4 to 3.0 degrees over a range of 115 degrees. The maximum deviation from a linear response was 9 degrees. The resolution and linearity depend on several transducer and joint geometry parameters, and can be predicted prior to implantation and calibrated after implantation. The results of this study 1) defined the most appropriate hermetic capsule designs for the IJAT sensor and magnet, 2) defined the best orientation of the magnetic field to optimize device function, 3) provided a computer model of the IJAT to aid in placement, calibration, and evaluation of the device, 4) verified the surgical techniques used to implant the device, and 5) verified the long-term functionality and the biocompatibility of the device.

Variations in innervation of the flexor digitorum profundus muscle

The composite flexor digitorum profundus muscle has a dual nerve supply from the ulnar nerve (UN) and the anterior interosseous nerve (AIN) but anatomic data regarding the territories of these 2 nerves are limited. In this study, muscles from 20 cadaver forearms were dissected microscopically. The motor nerves were followed to their terminations on individual muscle bellies and the innervation domains mapped. In 75% of cases the AIN supplied the index and middle fingers and the UN supplied the middle, ring, and little fingers; thus, the middle finger had dual innervation. In 20% of cases the AIN went to the index and middle fingers and the UN went to the ring and little fingers. In 5% of cases the AIN went to the index finger and the UN went to the middle, ring, and little fingers. The motor entry points were normalized to the forearm length. The entry points of the UN and AIN branches were at 15% and 30% of forearm length, respectively, distal to the medial epicondyle.

The function of the finger intrinsic muscles in response to electrical stimulation

The actions of the dorsal interosseous, volar interosseous, and lumbrical muscles were investigated using applied electrical stimulation and recording the moments that were generated across the metacarpophalangeal joint in flexion/extension and abduction/adduction, the proximal interphalangeal joint in flexion/extension, and the distal interphalangeal joint in flexion/extension. These measurements were made isometrically at various joint angles and levels of stimulation with both able bodied subjects and persons who had sustained tetraplegia. It was determined that the dorsal interossei, including the first, were strong abductors of the fingers and generated a significant moment in metacarpophalangeal (MP) joint flexion and interphalangeal (IP) joint extension. The volar interossei were the primary adductors of the fingers, as well as providing a significant moment in MP joint flexion and IP joint extension. The lumbrical muscles were found to be MP joint flexors and IP joint extensors, although the moments that were generated were on average 70% lower than the interossei. The role of the lumbricals as finger abductors or adductors could not be determined from the data. This information on the actions and moment generating capabilities of the intrinsic muscles led to the incorporation of the interossei into electrically induced hand grasp provided by an implanted neuroprosthesis. The evaluation of the intrinsic muscles in the neuroprosthesis was accomplished by recording the moment generating capabilities of these muscles across each of the joints of the finger. These muscles were capable of generating moments that were 80-90% of the average attained by the able bodied subjects, and have provided a substantial improvement to the electrically induced hand grasp.

Satisfaction with and usage of a hand neuroprosthesis

OBJECTIVE

To measure the satisfaction with, clinical impact of, and use of an implantable hand neuroprosthesis.

SETTING

Eight different medical centers.

PARTICIPANTS

Thirty-four individuals with spinal cord injuries at the C5 or C6 motor level.

INTERVENTIONS

Participants were implemented with a hand neuroprosthesis that provides grasp and release. The neuroprosthesis includes a surgically implanted stimulator, implanted electrodes sutured to the hand and forearm muscles, and an externally mounted controller.

MAIN OUTCOME MEASURE

A survey was mailed to study participants, who were asked to respond to statements such as "If I had it to do over, I would have the hand system implanted again," using a 5-level Likert scale ("strongly agree" to "strongly disagree").

RESULTS

Eighty-seven percent of participants were very satisfied with the neuroprosthesis, 88% reported a positive impact on their life, 87% reported improvements in activities of daily living, and 81% reported improved independence. Participants reported using the neuroprosthesis a median of 5.5 days per week; 15 participants used the neuroprosthesis 7 days per week, and 5 participants reported not using the device.

CONCLUSIONS

The neuroprosthesis was used by most participants. The neuroprosthesis performed satisfactorily, increased users' ability to perform activities of daily living and independence, and improved their quality of life.

An elbow extension neuroprosthesis for individuals with tetraplegia

Functional electrical stimulation (FES) of the triceps to restore control of elbow extension was integrated into a portable hand grasp neuroprosthesis for use by people with cervical level spinal cord injury. An accelerometer mounted on the upper arm activated triceps stimulation when the arm was raised above a predetermined threshold angle. Elbow posture was controlled by the subjects voluntarily flexing to counteract the stimulated elbow extension. The elbow moments created by the stimulated triceps were at least 4 N.m, which was sufficient to extend the arm against gravity. Electrical stimulation of the triceps increased the range of locations and orientations in the workspace over which subjects could grasp and move objects. In addition, object acquisition speed was increased. Thus elbow extension enhances a person's ability to grasp and manipulate objects in an unstructured environment.

Tissue response to chronically stimulated implanted epimysial and intramuscular electrodes

Twenty-four epimysial and 16 intramuscular electrodes were implanted in five adult dogs for periods ranging from 11 to 50 months. Chronic stimulation was applied to half of the electrodes for eight weeks near the end of the implantation period. The tissue response was rated by the amount and appearance of the fibrous tissue and inflammatory cells seen in the capsule lining the region of the electrode. The encapsulation tissues were composed primarily of collagen and fibroblasts and some macrophages and few other inflammatory cells. The epimysial electrodes exhibited more variation between and within electrodes, but had more of the better scores than the intramuscular electrodes. No difference in the distribution of scores was measured between the control and stimulated groups for the epimysial electrodes. While the scores for the intra-muscular electrodes varied very little, variance was sufficient to indicate a trend for poorer ratings with the application of chronic stimulation. Fibrous capsules were generally thinner under the epimysial electrodes than around the intramuscular electrodes. For both electrode types, the thickness was not correlated with the application or level of chronic stimulation. Thickness was shown to be positively correlated to the degree of loss of the sutures used to anchor the epimysial electrodes.

An implanted upper-extremity neuroprosthesis. Follow-up of five patients

An implanted neuroprosthesis supplying functional neuromuscular stimulation was used to provide grasp and release to tetraplegic individuals. This article describes the results, at a minimum of three years, for the first five patients to have operative implantation of an eight-channel stimulator-receiver. All of the patients had a clinically complete spinal cord injury with motor function remaining at the level of the fifth or sixth cervical nerve root. In addition to implantation of the stimulator system, each patient had augmentative operations on the hand to improve function. The procedures included tendon transfers, side-to-side tendon anastomoses, arthrodesis of the interphalangeal joint of the thumb, and rotational osteotomy of the radius. The neuroprosthesis provides two grasp patterns controlled by voluntary motion of the shoulder or wrist. Functional evaluations included measurement of pinch force, a grasp-release test, evaluation of the level of functional independence, and usage surveys. Pinch force ranged from eight to twenty-five newtons. All five patients demonstrated functional grasp patterns, had increased independence, and were able to use the neuroprosthesis at home on a regular basis. The implanted stimulator has proved to be safe and reliable, with seven years as the longest time in situ at the time of writing.

Measurement of isometric elbow and shoulder moments: position-dependent strength of posterior deltoid-to-triceps muscle tendon transfer in tetraplegia

This report describes an apparatus which has been developed to measure several isometric elbow and shoulder forces and moments simultaneously and also allows this characterization to be performed across a range of shoulder and elbow joint angles in a horizontal plane. This apparatus was used to characterize the elbow extension strength in individuals with tetraplegia resulting from cervical level spinal cord injury. In all of these individuals, voluntary elbow extension was provided exclusively by the posterior deltoid muscle, which had previously been surgically transferred to the tendon of the paralyzed triceps muscle. Elbow extension is essential for many daily activities, such as reaching above shoulder level and pushing objects away from the body; the widely used posterior deltoid-to-triceps muscle tendon transfer surgery restores some degree of voluntary control to this important function. The apparatus contained a six-axis force-moment transducer to which the arm of each subject was attached. The six outputs of the transducer were transformed to correspond to physiological elbow and shoulder moments and forces. A customized table allowed the shoulder and elbow angles of the subject to be varied over a wide range in a horizontal plane so that the effects of posterior deltoid muscle length could be characterized over the likely functional range of the subject within this plane. It was found that elbow extension strength varied widely across subjects with C5 or C6 tetraplegia, from quite weak to strong enough to propel a manual wheelchair. Furthermore, the elbow extension strength of most subjects showed a strong dependence on both elbow and shoulder angles. Elbow extension was typically weak when the upper arm was elevated to shoulder level at the side, which unfortunately corresponds to the position often adopted by these individuals due to shoulder weakness.

Carpal instability in the weight-bearing upper extremity

The prevalence of carpal instability in a paraplegic population was investigated to establish an association between chronic repetitive stress on the wrist and the development of such instability. Nine of 162 paraplegic patients had static carpal instability and no history of an acute injury of the wrist. The predominant pattern of instability, found in eleven wrists (six patients), was non-dissociative volar intercalated segmental instability. The prevalence of carpal instability increased with the duration of weight-bearing on the upper extremity. Eighteen per cent of the patients in whom the spinal cord injury had occurred more than twenty years before the study had carpal instability. Carpal instability in these weight-bearing upper extremities and the increase in its prevalence with the duration of the forces across the wrist demonstrate an association between chronic repetitive stress on the wrist and carpal instability.

Restoration of pronosupination control by FNS in tetraplegia--experimental and biomechanical evaluation of feasibility

Individuals with C5/C6 tetraplegia lack voluntary control of the forearm pronators. We evaluated the feasibility of restoring forearm pronation/supination control using an electrically activated pronator opposed by voluntary supination. To this end, we measured the electrically produced pronation moments of subjects with tetraplegia. The maximal pronation moment achieved by stimulating the pronator quadratus ranged from 30 to 100 N cm in three forearms of two subjects. These moments were sufficient to produce forearm pronation in all three forearms. Voluntary control of pronosupination during constant pronator stimulation was achieved by having the subject voluntarily supinate or relax to change the balance of rotational torques acting on the forearm. In all cases, the subjects were able to supinate voluntarily against the continuously stimulated pronator, producing intermediate angles between full pronation and full supination. We also observed under some conditions that subjects could voluntarily pronate and supinate even without pronator stimulation. Using a biomechanical model, we show how pronation can be initiated from a supinated position using the brachioradialis, with gravity completing the pronation. This method of pronation without stimulation is extremely sensitive to the orientation of the forearm in the gravitational field, and thus is not a widely applicable technique. We conclude that forearm pronosupination via Functional Neuromuscular Stimulation is feasible, and would provide subjects the ability to pronate without the assistance of gravity.

Tendon transfers and functional electrical stimulation for restoration of hand function in spinal cord injury

Spinal cord injury at the C5 and C6 level results in loss of hand function. Electrical stimulation of paralyzed muscles is one approach that has demonstrated significant capacity for restoring grasp and release function. One potential limitation of this approach is that key muscles for stimulation may have lower motor neuron damage, rendering the muscles unexcitable. We have used surgical modification of the biomechanics of the hand to overcome this limitation. Tendon transfer of paralyzed but lower motor neuron intact muscles can compensate for potential function lost owing to muscles with lower motor neuron damage. Such procedures have been performed to provide finger extension, thumb extension, finger flexion, and wrist extension. Additional surgical procedures have been performed to enhance the function provided with electrical stimulation. These are side-to-side synchronization of the finger flexor and extensor tendons, the flexor digitorium superficialis Zancolli-lasso procedure, and thumb interphalangeal joint arthrodesis. These procedures have been performed in 11 patients with C5 and C6 level spinal injuries and functional electrical stimulation neuroprostheses. In these patients, 41 different functional electrical stimulation-related procedures were performed and 38 gave the desired result after surgery. One procedure resulted in no increase or decrease in function or muscle output, and two procedures resulted in a decrease in muscle force or joint range of motion. The issues that must be considered in performing functional electrical stimulation-related tendon transfers are discussed.

Functional range of motion of the elbow

One hundred normal upper extremities in 50 adults were sequentially studied in a Bledsoe brace, which limited elbow motion. The amount of flexion and extension of the elbow was serially limited by 15 degree increments. At each setting, the subjects were asked to perform 12 activities of daily living. The percentage of subjects who completed each task with the specified range of motion was determined. Overall, 49 of the subjects performed all of the tasks with extension limited at 75 degrees and flexion limited at 120 degrees. By isolating the allowable range of motion of the elbow and allowing for compensatory motions and strategies of the normal adjacent joints, the functional elbow range of motion is established as 75 degrees-120 degrees flexion. Thus, the functional status of a patient with a specific elbow range of motion can be predicted more accurately.