Michael W. Keith

A surgically-implanted intramuscular electrode for an implantable neuromuscular stimulation system

An intramuscular electrode has been developed for use with an implantable neuromuscular stimulator. In vitro tests indicate that the electrode will maintain a stable position within the muscle, but is capable of being removed intact. When tested in a buffered saline environment at the maximum stimulation parameters (0.4 /spl mu/C/mm/sup 2//phase), there was no corrosion of the stimulating surface. In vivo evaluations were conducted, in which four sets of 4 intramuscular electrodes and 4 epimysial electrodes, were surgically implanted in the forelimb of 4 dogs. Each set was connected to an implanted neuromuscular stimulator. All but 1 of the 16 intramuscular electrodes operated properly throughout the study, producing responses functionally indistinguishable from epimysial electrodes. One electrode fractured due to improper surgical placement. After removal, some pitting corrosion was observed in 2 of the 15 retrieved intramuscular electrodes, possibly due to minute surface defects resulting from the electrode manufacturing process. >

Diagnosis and treatment of acute Achilles tendon rupture.

This clinical practice guideline is based on a series of systematic reviews of published studies in the available literature on the diagnosis and treatment of acute Achilles tendon rupture. None of the 16 recommendations made by the work group was graded as strong; most are graded inconclusive; four are graded weak; two are graded as moderate strength; and two are consensus statements. The two moderate-strength recommendations include the suggestions for early postoperative protective weight bearing and for the use of protective devices that allow for postoperative mobilization.

Locking plates for extremity fractures.

Thirty-three peer-reviewed studies met the inclusion criteria for the Overview. Criteria were framed by three key questions regarding indications for the use of locking plates, their effectiveness in comparison with traditional nonlocking plates, and their cost-effectiveness. The studies were divided into seven applications: distal radius, proximal humerus, distal femur, periprosthetic femur, tibial plateau (AO/OTA type C), proximal tibia (AO/OTA type A or C), and distal tibia. Patient enrollment criteria were recorded to determine indications for use of locking plates, but the published studies do not consistently report the same enrollment criteria. Regarding effectiveness, there were no statistically significant differences between locking plates and nonlocking plates for patient-oriented outcomes, adverse events, or complications. The literature search did not identify any peer-reviewed studies that address the cost-effectiveness or cost-utility of locking plates.

Implanted Neuroprosthesis for Restoring Arm and Hand Function in People With High Level Tetraplegia

OBJECTIVEnTo develop and apply an implanted neuroprosthesis to restore arm and hand function to individuals with high level tetraplegia.nnnDESIGNnCase study.nnnSETTINGnClinical research laboratory.nnnPARTICIPANTSnIndividuals with spinal cord injuries (N=2) at or above the C4 motor level.nnnINTERVENTIONSnThe individuals were each implanted with 2 stimulators (24 stimulation channels and 4 myoelectric recording channels total). Stimulating electrodes were placed in the shoulder and arm, being, to our knowledge, the first long-term application of spiral nerve cuff electrodes to activate a human limb. Myoelectric recording electrodes were placed in the head and neck areas.nnnMAIN OUTCOME MEASURESnSuccessful installation and operation of the neuroprosthesis and electrode performance, range of motion, grasp strength, joint moments, and performance in activities of daily living.nnnRESULTSnThe neuroprosthesis system was successfully implanted in both individuals. Spiral nerve cuff electrodes were placed around upper extremity nerves and activated the intended muscles. In both individuals, the neuroprosthesis has functioned properly for at least 2.5 years postimplant. Hand, wrist, forearm, elbow, and shoulder movements were achieved. A mobile arm support was needed to support the mass of the arm during functional activities. One individual was able to perform several activities of daily living with some limitations as a result of spasticity. The second individual was able to partially complete 2 activities of daily living.nnnCONCLUSIONSnFunctional electrical stimulation is a feasible intervention for restoring arm and hand functions to individuals with high tetraplegia. Forces and movements were generated at the hand, wrist, elbow, and shoulder that allowed the performance of activities of daily living, with some limitations requiring the use of a mobile arm support to assist the stimulated shoulder forces.

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

Multi-contact cuff electrodes were implanted in the median, ulnar, and radial nerves of an upper-limb amputee. 19 of 20 contacts produced selective, sensory response in the phantom limb from nerve stimulation. The neural interface has been stable for the duration of this ongoing chronic study, 12 months post-implant, with consistent threshold and impedance measures.

Diagnosis and Treatment of Osteochondritis Dissecans

This clinical practice guideline is based on a series of systematic reviews of published studies in the available literature on the diagnosis and treatment of osteochondritis dissecans of the knee. None of the 16 recommendations made by the work group is graded as strong; most are graded inconclusive; two are graded weak; and four are consensus statements. Both of the weak recommendations are related to imaging evaluation. For patients with knee symptoms, radiographs of the joint may be obtained to identify the lesion. For patients with radiographically apparent lesions, MRI may be used to further characterize the osteochondritis dissecans lesion or identify other knee pathology.

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° 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° and 120° 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.Clinical Relevance: The brachioradialis is the donor muscle most commonly used to restore the function of the wrist and hand in tetraplegia. Because many self-care activities involve acquiring an object at a distance from the body and then bringing the object close to the body, it is important to consider the influence of the position of the elbow on the function of the transferred brachioradialis.

Upper Extremity Assessment in Tetraplegia: The Importance of Differentiating Between Upper and Lower Motor Neuron Paralysis

Scientific advances are increasing the options for improved upper limb function in people with cervical level spinal cord injury (SCI). Some of these interventions rely on identifying an aspect of paralysis that is not uniformly assessed in SCI: the integrity of the lower motor neuron (LMN). SCI can damage both the upper motor neuron and LMN causing muscle paralysis. Differentiation between these causes of paralysis is not typically believed to be important during SCI rehabilitation because, regardless of the cause, the muscles are no longer under voluntary control by the patient. Emerging treatments designed to restore upper extremity function (eg, rescue microsurgical nerve transfers, motor learning-based interventions, functional electrical stimulation) all require knowledge of LMN status. The LMN is easily evaluated using surface electrical stimulation and does not add significant time to the standard clinical assessment of SCI. This noninvasive evaluation yields information that contributes to the development of a lifetime upper extremity care plan for maximizing function and quality of life. Given the relative simplicity of this assessment and the far-reaching implications for treatment and function, we propose that this assessment should be adopted as standard practice for acute cervical SCI.

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.

Surgical alterations and functional neuromuscular stimulation for enhancement of hand function in spinal cord injury

Surgical alterations were combined with functional neuromuscular stimulation to enhance hand function in the patient with high-level spinal injury. These alterations are: thumb interphalangeal joint arthrodesis, finger tendon synchronization, and tendon transfer of muscles with upper motor neuron lesions. These procedures resulted in more uniform movement of the digits, generation of movement unavailable because of denervation, and use of an additional stimulated muscle. The main difficulty with the tendon transfer synchronization procedures was the development of postsurgical adhesions. This problem has been mitigated by earlier postsurgical mobilization of the tendons, with no instances of rupture.<<ETX>>