EEG During Pedaling: Evidence for Cortical Control of Locomotor Tasks

Objective: This study characterized the brain electrical activity during pedaling, a locomotor-like task, in humans. We postulated that phasic brain activity would be associated with active pedaling, consistent with a cortical role in locomotor tasks. Methods: Sixty four channels of electroencephalogram (EEG) and 10 channels of electromyogram (EMG) data were recorded from 10 neurologically-intact volunteers while they performed active and passive (no effort) pedaling on a custom-designed stationary bicycle. Ensemble averaged waveforms, 2 dimensional topographic maps and amplitude of the β (13–35 Hz) frequency band were analyzed and compared between active and passive trials. Results: The peak-to-peak amplitude (peak positive–peak negative) of the EEG waveform recorded at the Cz electrode was higher in the passive than the active trials (p \u3c 0.01). β-band oscillations in electrodes overlying the leg representation area of the cortex were significantly desynchronized during active compared to the passive pedaling (p \u3c 0.01). A significant negative correlation was observed between the average EEG waveform for active trials and the composite EMG (summated EMG from both limbs for each muscle) of the rectus femoris (r = −0.77, p \u3c 0.01) the medial hamstrings (r = −0.85, p \u3c 0.01) and the tibialis anterior (r = −0.70, p \u3c 0.01) muscles. Conclusions: These results demonstrated that substantial sensorimotor processing occurs in the brain during pedaling in humans. Further, cortical activity seemed to be greatest during recruitment of the muscles critical for transitioning the legs from flexion to extension and vice versa. Significance: This is the first study demonstrating the feasibility of EEG recording during pedaling, and owing to similarities between pedaling and bipedal walking, may provide valuable insight into brain activity during locomotion in humans

Epidermal Neural Crest Stem Cell (EPI-NCSC)—Mediated Recovery of Sensory Function in a Mouse Model of Spinal Cord Injury

Here we show that epidermal neural crest stem cell (EPI-NCSC) transplants in the contused spinal cord caused a 24% improvement in sensory connectivity and a substantial recovery of touch perception. Furthermore we present a novel method for the ex vivo expansion of EPI-NCSC into millions of stem cells that takes advantage of the migratory ability of neural crest stem cells and is based on a new culture medium and the use of microcarriers. Functional improvement was shown by two independent methods, spinal somatosensory evoked potentials (SpSEP) and the Semmes-Weinstein touch test. Subsets of transplanted cells differentiated into myelinating oligodendrocytes. Unilateral injections of EPI-NCSC into the lesion of midline contused mouse spinal cords elicited bilateral improvements. Intraspinal EPI-NCSC did not migrate laterally in the spinal cord or invade the spinal roots and dorsal root ganglia, thus implicating diffusible factors. EPI-NCSC expressed neurotrophic factors, angiogenic factors, and metalloproteases. The strength of EPI-NCSC thus is that they can exert a combination of pertinent functions in the contused spinal cord, including cell replacement, neuroprotection, angiogenesis and modulation of scar formation. EPI-NCSC are uniquely qualified for cell-based therapy in spinal cord injury, as neural crest cells and neural tube stem cells share a higher order stem cell and are thus ontologically closely related

Alteration of load sharing of anterior cervical implants with change in cervical sagittal alignment

Anterior cervical discectomy and fusion (ACDF) is often supplemented with the application of an anterior plate to improve the stability of the fusion segment. While plate design has been shown to influence stress shielding of the graft, little is known about how the kyphotic alignment of a fused cervical segment affects the load sharing between the anterior plate and the osteoligamentous structures of the spine. The aim of this study was to characterize load sharing between an anterior plate and the osteoligamentous structures of the cervical motion segments in kyphotic versus normal lordotic alignment following single-level ACDF using fresh ovine cervical spines (C3-C6). The loading protocol involved preloading the spine with a 20 N compressive force and applying quasi-static moments (up to 2.1 Nm) in the sagittal plane to simulate flexion and extension. Stiffness of the fusion segment was measured from the moment-rotation plot. Normal lordotic alignment was replicated by insertion of a fibular allograft 2 mm taller than the interbody space. Kyphotic alignment was simulated by removing the graft and reapplying a shorter anterior cervical plate. The average segmental sagittal angulation at C4-C5 was 5.2 ± 1.6° of lordosis for the normal lordotic group and 6.8 ± 2.3° of kyphosis for the kyphotic group. With flexion, the plate shared 52.8% of the applied load in the normal lordotic group, and 70.1% in the kyphotic group (p \u3c 0.03). In extension, the amount of load-share by the plate in the normal lordotic group was comparable to that of the kyphotic group (52.7% vs. 40.7%, p = 0.16). This study shows that kyphotic alignment of the cervical fusion segment increases the load sharing of the anterior plate under flexion loading. © 2007 IPEM

The effect of platelet-rich plasma and bone marrow on murine posterolateral lumbar spine arthrodesis with bone morphogenetic protein

Background: Recombinant human bone morphogenetic protein-2 (rhBMP-2) has had limited success in stimulating osteogenesis at the site of posterolateral lumbar spine arthrodesis when used at the currently approved human dose for anterior lumbar interbody arthrodesis. The objective of the present study was to investigate the effect of co-administration of fresh harvested autologous bone marrow aspirate and platelet-rich plasma on rhBMP-2-mediated in vivo murine posterolateral lumbar spine arthrodesis. Methods: Forty adult male mice underwent posterolateral intertransverse process arthrodesis from L4 to L6. In three experimental groups, a collagen sponge was placed on each side, overlaying the decorticated transverse processes. Each collagen sponge was presoaked for fifteen minutes with 31 mg of rhBMP-2 in a 100-μL solution containing either saline solution (n = 10), platelet-rich plasma (n = 10), or donor bone-marrow cells (n = 10). Control mice underwent decortication alone (n = 10). The lumbar spine was harvested four weeks after surgery, and spinal fusion was evaluated on the basis of radiographs, computed tomography, and histological analysis. Results: Control mice showed no evidence of spinal fusion. The rate of fusion was radiographically and histologically similar in all three experimental groups. The area, volume, and density of the fusion mass were significantly greater (p \u3c 0.05) for the group treated with rhBMP-2 and bone marrow as compared with the group treated with rhBMP-2 alone. The group treated with rhBMP-2 and platelet-rich plasma had intermediate fusion area and density. Histologically, the spines treated with rhBMP-2 alone consistently showed the presence of cortical bone between the two transverse processes but fewer trabeculae within the fusion mass; bone marrow co-augmentation resulted in more trabeculae within the fusion mass and a thicker cortical perimeter. Conclusions: The present study quantitatively confirmed a synergistic effect of bone marrow cells when added to rhBMP-2 in an in vivo mouse posterolateral lumbar spine fusion model. The volume, area, and density of the fusion mass were significantly increased by augmentation with bone marrow cells. Clinical Relevance: Increasing the success of rhBMP-2 augmented posterolateral lumbar spine fusion needs to be further explored in the context of its synergistic mechanisms with other locally available osteoprogenitor cells and growth factors. Additional studies involving higher animals and clinical trials involving humans will be required before this synergistic activity is used clinically. Copyright © 2009 by The Journal of Bone and Joint Surgery, Incorporated

Autograft containment in posterolateral spine fusion

Background context: Pseudoarthrosis rates in lumbar intertransverse fusion remain high. Compression and displacement of the developing fusion mass by the paraspinal musculature may be a contributory factor. Biocontainment devices have been clinically used in the skull and mandible to guide bone regeneration. The role of a mechanical device in containing graft material in the developing posterolateral lumbar spine fusion is unclear. Purpose: To determine the benefits of using a bioabsorbable graft-containment device for lumbar intertransverse fusion, and to evaluate the biocompatibility of this implant by histological analysis of the host tissue reaction. Study design: A rabbit intertransverse spine fusion model was used to evaluate a bioabsorbable graft-containment implant. Study and control groups were compared with regard to the rate, volume, and quality of fusion, as well as host tissue reaction to the graft and implant. Methods: Fourteen adult male New Zealand White rabbits underwent bilateral posterolateral intertransverse spine arthrodesis at L3-L4. The control group (n=7) received autograft alone, and the study group received autografts placed in open meshed hemicylinders fashioned from LactoSorb sheets (LactoSorb; Biomet Orthopedics Inc., Warsaw, IN). Spines were harvested at 6 weeks and imaged. Radiographs and computed tomography (CT) images were used to calculate the rate, area, and volume of fusion mass. Sections were fixed and stained with hematoxylin-eosin and Mallory trichrome for histological analysis of fusion and host tissue response. The Mann-Whitney nonparametric statistical test was used for the radiographic and CT qualitative assessments. The CT volume quantitation was analyzed using the Student t test. A p value of \u3c.05 was used to assign statistical significance. Results: The fusion rates on radiographs and CT imaging did not show a significant difference (p\u3e.05) between the biocontainment and control groups. The volume of fusion revealed a significant increase with biocontainment (mean±standard error; total left+right fusion sides=2.88±0.30 cc) compared with controls (2.12±0.15 cc) (p\u3c.05). Histology revealed no difference in the maturity or the quality of the fusion mass between the two groups. Inflammatory response around the developing fusion mass and muscle necrosis were slightly increased in the study group. The LactoSorb biocontainment material led to variable inflammatory reaction, with some areas showing little or no response and other showing an inflammatory response with fibrous connective tissue, lymphocyte infiltration, and focal foreign body giant cell reaction. Conclusions: The incidence of fusion was similar with or without a containment device for onlay bone graft. A significant increase in the volume of the fusion suggests that a biocontainment device does play a role in protecting the developing fusion mass from the mechanical effects of the paraspinal musculature. The clinical use of this device cannot be justified at this time, and further studies will determine whether this increase in fusion volume will translate into a better incidence and volume of fusion in primate and human models. © 2008 Elsevier Inc. All rights reserved