Rajiv Saigal

Intraspinal microstimulation generates functional movements after spinal-cord injury

Restoring locomotion after spinal-cord injury has been a difficult problem to solve with traditional functional electrical stimulation (FES) systems. Intraspinal microstimulation (ISMS) is a novel approach to FES that takes advantage of spinal-cord locomotor circuits by stimulating in the spinal cord directly. Previous studies in spinal-cord intact cats showed near normal recruitment order, reduced fatigue, and functional, synergistic movements induced by stimulation through a few microwires implanted over a 3-cm region in the lumbosacral cord , . The present study sought to test the feasibility of ISMS for restoring locomotion after complete spinal-cord transection. In four adult male cats, the spinal cord was severed at T10, T11, or T12. Two to four weeks later, 30 wires (30 /spl mu/m, stainless steel) were implanted, under anesthesia, in both sides of the lumbosacral cord. The cats were then decerebrated. Stimulus pulses (40 - 50 Hz, 200 /spl mu/s, biphasic) with amplitudes ranging from 1 - 4x threshold (threshold = 32 /spl plusmn/19 /spl mu/A) were delivered through each unipolar electrode. Kinetics, kinematics, and electromyographic (EMG) measurements were obtained with the cats suspended over a stationary treadmill with embedded force platforms for the hindlimbs. Phasic, interleaved stimulation through electrodes generating flexor or extensor movements produced bilateral weight-bearing stepping of the hindlimbs with ample foot clearance during swing. Minimal changes in kinematics and little fatigue were seen during episodes of 40 consecutive steps. The results indicate that ISMS is a promising technique for restoring locomotion after injury.

Effects of electrical stimulation in C2C12 muscle constructs.

Electrical stimulation affects the deposition of extracellular matrices and cellular differentiation. Type I collagen is one of the most abundant extracellular matrix proteins; however, not much is known about the effects of electrical stimulation on collagen type I deposition in C2C12 cells. Thus, we studied the effects of electrical voltage and stimulation frequency in 3D cultured C2C12 muscle cells in terms of metabolic activity, type I collagen deposition and cell morphology. Electrically excitable C2C12 muscle cells were seeded in collagen scaffolds and stimulated with rectangular signals of voltage (2, 5, 7 V) and frequency (1, 2 Hz), using parallel carbon electrodes spaced 1 cm apart. Metabolic activity was quantified by the glucose:lactate concentration ratio in the medium. Apoptotic activity was assessed by TUNEL staining and changes in collagen deposition were identified by immunohistology. The ultrastructure of the tissue was examined by TEM. Glucose and lactate analysis indicated that all groups had similar metabolic activity. TUNEL stain showed no significant difference in apoptotic damage induced by electrical stimulation compared to the control. Samples stimulated at 2 Hz exhibited reduced collagen deposition compared to the control and 1 Hz stimulated samples. Muscle‐protein marker desmin was highly expressed in constructs stimulated with 1 Hz/5 V sample. TEM revealed that the stimulated samples developed highly organized sarcomeres, which coincided with improved contractile properties in the 1 Hz/5 V‐ and 2 Hz/5 V‐stimulated groups. Our data implicate that a specific electrical frequency may modulate type I collagen accumulation and a specific voltage may affect the differentiation of muscle sarcomeres in excitable cells. Copyright

Locomotor-Related Networks in the Lumbosacral Enlargement of the Adult Spinal Cat: Activation Through Intraspinal Microstimulation

It is commonly accepted that locomotor-related neuronal circuitry resides in the lumbosacral spinal cord. Pharmacological agents, epidural electrical stimulation, and sensory stimulation can be used to activate these intrinsic networks in in vitro neonatal rat and in vivo cat preparations. In this study, we investigated the use of low-level tonic intraspinal microstimulation (ISMS) as a means of activating spinal locomotor networks in adult cats with complete spinal transections. Trains of low-amplitude electrical pulses were delivered to the spinal cord via groups of fine microwires implanted in the ventral horns of the lumbosacral enlargement. In contrast to published reports, tonic ISMS applied through microwires in the caudal regions of the lumbosacral enlargement (L7-S1) was more effective in eliciting alternating movements in the hindlimbs than stimulation in the rostral regions. Possible mechanisms of action of tonic ISMS include depolarization of locally oscillating networks in the lumbosacral cord, backfiring of primary afferents, or activation of propriospinal neurons

Health Economic Analysis of Adult Deformity Surgery

Given the substantial growth in frequency and expense of spine deformity surgery, and the general economic landscape of the health care system, health economics research has an important role in the literature on adult spinal deformity (ASD). The purpose of this article is to provide an update on the current state of health economics studies in the ASD literature and to introduce areas in which health economics might play some additional role in future research on ASD.

Three-dimensional conductive constructs for nerve regeneration.

The unique electrochemical properties of conductive polymers can be utilized to form stand-alone polymeric tubes and arrays of tubes that are suitable for guides to promote peripheral nerve regeneration. Noncomposite, polypyrrole (PPy) tubes ranging in inner diameter from 25 microm to 1.6 mm as well as multichannel tubes were fabricated by electrodeposition. While oxidation of the pyrrole monomer causes growth of the film, brief subsequent reduction allowed mechanical dissociation from the electrode mold, creating a stand-alone, conductive PPy tube. Conductive polymer nerve guides made in this manner were placed in transected rat sciatic nerves and shown to support nerve regeneration over an 8-week time period.

Analysis of the direct cost of surgery for four diagnostic categories of adult spinal deformity

BACKGROUND CONTEXT Existing literature on adult spinal deformity (ASD) offers little guidance regarding an evidence-based approach to care. To optimize the value of medical treatment, a thorough understanding of the cost of surgical treatment for ASD is required. PURPOSE To evaluate four clinically and radiographically distinct groups of ASD and identify and compare the cost of surgical treatment among the groups. STUDY DESIGN/SETTING Multicenter retrospective study of consecutive surgeries for ASD. PATIENT SAMPLE Three hundred twenty-five consecutive ASD patients treated between 2008 and 2010. OUTCOME MEASURES Cost data were collected from hospital administrative records on the direct costs (DCs) incurred for the episode of surgical care, excluding overhead. METHODS Based on preoperative radiographs and history, patients were categorized into one of four diagnostic categories of deformity: primary idiopathic scoliosis (PIS), primary degenerative scoliosis (PDS), primary sagittal plane deformity (PSPD), and revision (R). Analysis of variance and generalized linear model regressions were used to analyze the DCs of surgery and to assess differences in costs across the four diagnostic categories considered. RESULTS Significant differences were observed in DC of surgery for different categories of ASD, with surgical treatment for PDS the most expensive followed in decreasing order by PSPD, PIS, and R (p<.01). Results further revealed a significant positive relationship between age and DC (p<.01) and a significant positive relationship between length of stay and DC (p<.01). Among PIS patients, for every incremental increase in levels fused, the expected DC increased by

Complications and outcomes of vasopressor usage in acute traumatic central cord syndrome

3,997 (p=.00). Fusion to pelvis also significantly increased the DC of surgery for patients aged 18 to 29 years (p<.01) and 30 to 59 years (p<.01) but not for 60 years or more (p=.86). CONCLUSIONS There is an increasing DC of surgery with increasing age, length of hospital stay, length of fusion, and fusions to the pelvis. Revision surgery is the least expensive surgery on average and should therefore not preclude its consideration from a pure cost perspective.

Targeted reduction in neurosurgical laboratory utilization: resident-led effort at a single academic institution

OBJECT The optimal mean arterial pressure (MAP) for spinal cord perfusion after trauma remains unclear. Although there are published data on MAP goals after spinal cord injury (SCI), the specific blood pressure management for acute traumatic central cord syndrome (ATCCS) and the implications of these interventions have yet to be elucidated. Additionally, the complications of specific vasopressors have not been fully explored in this injury condition. METHODS The present study is a retrospective cohort analysis of 34 patients with ATCCS who received any vasopressor to maintain blood pressure above predetermined MAP goals at a single Level 1 trauma center. The collected variables were American Spinal Injury Association (ASIA) grades at admission and discharge, administered vasopressor and associated complications, other interventions and complications, and timing of surgery. The relationship between the 2 most common vasopressors-dopamine and phenylephrine-and complications within the cohort as a whole were explored, and again after stratification by age. RESULTS The mean age of the ATCCS patients was 62 years. Dopamine was the most commonly used primary vasopressor (91% of patients), followed by phenylephrine (65%). Vasopressors were administered to maintain MAP goals fora mean of 101 hours. Neurological status improved by a median of 1 ASIA grade in all patients, regardless of the choice of vasopressor. Sixty-four percent of surgical patients underwent decompression within 24 hours. There was no observed relationship between the timing of surgical intervention and the complication rate. Cardiogenic complications associated with vasopressor usage were notable in 68% of patients who received dopamine and 46% of patients who received phenylephrine. These differences were not statistically significant (OR with dopamine 2.50 [95% CI 0.82-7.78], p = 0.105). However, in the subgroup of patients > 55 years, dopamine produced statistically significant increases in the complication rates when compared with phenylephrine (83% vs 50% for dopamine and phenylephrine, respectively; OR with dopamine 5.0 [95% CI 0.99-25.34], p = 0.044). CONCLUSIONS Vasopressor usage in ATCCS patients is associated with complication rates that are similar to the reported literature for SCI. Dopamine was associated with a higher risk of complications in patients > 55 years. Given the increased incidence of ATCCS in older populations, determination of MAP goals and vasopressor administration should be carefully considered in these patients. While a randomized control trial on this topic may not be practical, a multiinstitutional prospective study for SCI that includes ATCCS patients as a subpopulation would be useful for examining MAP goals in this population.

Anterior Column Realignment (ACR) in Adult Sagittal Deformity Correction: Technique and Review of the Literature.

OBJECT Given economic limitations and burgeoning health care costs, there is a need to minimize unnecessary diagnostic laboratory tests. METHODS The authors studied whether a financial incentive program for trainees could lead to fewer unnecessary laboratory tests in neurosurgical patients in a large, 600-bed academic hospital setting. The authors identified 5 laboratory tests that ranked in the top 13 of the most frequently ordered during the 2010-2011 fiscal year, yet were least likely to be abnormal or influence patient management. RESULTS In a single year of study, there was a 47% reduction in testing of serum total calcium, ionized calcium, chloride, magnesium, and phosphorus. This reduction led to a savings of

Adult Spinal Deformity Patients Recall Fewer Than 50% of the Risks Discussed in the Informed Consent Process Preoperatively and the Recall Rate Worsens Significantly in the Postoperative Period

1.7 million in billable charges to health care payers and