Effect of functional electrical stimulation (FES) combined with robotically assisted treadmill training on the EMG profile.

Functional electrical stimulation (FES) is used to assist spinal cord injury patients during walking. However, FES has yet to be shown to have lasting effects on the underlying neurophysiology which lead to long-term rehabilitation. A new approach to FES has been developed by which stimulation is timed to robotically controlled movements in an attempt to promote long-term rehabilitation of walking. This approach was tested in a rodent model of spinal cord injury. Rats who received this FES therapy during a 2-week training period exhibited peak EMG activity during the appropriate phase of the gait cycle; whereas, rats who received stimulation which was randomly timed with respect to their motor activity exhibited no clear pattern in their EMG profile. These results from our newly developed FES system serve as a launching point for many future studies to test and understand the long-term effect of FES on spinal cord rehabilitation.

An analytical comparison of the information in sorted and non-sorted cosine-tuned spike activity.

Spike sorting is a technologically expensive component of the signal processing chain required to interpret population spike activity acquired in a neuromotor prosthesis. No systematic analysis of the value of spike sorting has been carried out, and little is known about the effects of spike sorting error on the ability of a brain-machine interface (BMI) to decode intended motor commands. We developed a theoretical framework to examine the effects of spike processing on the information available to a BMI decoder. We computed the mutual information in neural activity in a simplified model of directional cosine tuning to compare the effects of pooling activity from up to four neurons to the effects of sorting with varying amounts of spike error. The results showed that information in a small population of cosine-tuned neurons is maximized when the responses are sorted and there is diverse tuning of units, but information was affected little when pooling units with similar preferred directions. Spike error had adverse effects on information, such that non-sorted population activity had 79-92% of the information in its sorted counterpart for reasonable amounts of detection and sorting error and for units with moderate differences in preferred direction. This quantification of information loss associated with pooling units and with spike detection and sorting error will help to guide the engineering decisions in designing a BMI spike processing system.

Spontaneous proximal thoracic curve correction after isolated fusion of the main thoracic curve in adolescent idiopathic scoliosis.

STUDY DESIGN: Retrospective clinical, radiographic, and patient outcome review of surgically treated adolescent idiopathic scoliosis. OBJECTIVES: To evaluate the spontaneous correction of the noninstrumented proximal thoracic (PT) curve after isolated correction of the main thoracic (MT) curve by either an anterior (ASF) or posterior (PSF) instrumentation and fusion. SUMMARY OF BACKGROUND DATA: There are no studies comparing the structural PT curve response after anterior versus posterior instrumented fusion of the MT curve in adolescent idiopathic scoliosis. METHODS: Eighty-five patients (single surgeon) with adolescent idiopathic scoliosis underwent operative instrumentation and fusion of their MT curve. All patients had a PT curve > or =20 degrees (average 29 degrees, range 20-49 degrees; average residual side-bending 18 degrees, range 3-42 degrees ) and were evaluated for preoperative PT curve flexibility and postoperative curve correction after PSF with the PT curve not instrumented (n = 44) and ASF with the PT curve not instrumented (n = 41). Minimum follow-up was 2 years (average, 3.6 years). Preoperative, 1 week postoperative, and latest follow-up (minimum 2-year) full-length radiographs were evaluated for the PT, MT, and thoracolumbar-lumbar coronal, side-bending, and sagittal Cobb measurements, as well as T1 tilt, clavicle angle, radiographic shoulder height, and the PT, MT, and thoracolumbar-lumbar apical vertical translation. A patient outcome questionnaire was also completed to correlate patient satisfaction with respect to their shoulder balance and overall appearance. RESULTS: The two groups were found to be statistically equivalent (P = 0.66) in terms of preoperative PT curve, MT curve, and MT side-bending curves, with the PT side benders slightly more flexible for the ASF (43%) versus the PSF group (31%) (P = 0.02). RADIOGRAPHIC: The spontaneous improvement in the PT curve was significant (P < 0.0001) in both groups. Additionally, this correction was maintained over time. However, the spontaneous PT curve correction was significantly greater after an ASF versus PSF correction of the MT curve on both the immediate postoperative (P =0.017) and minimum 2-year (P = 0.0024) evaluations, whereas the MT curve correction was the same in both groups (P = 0.45). There was no difference in the postoperative sagittal change in the PT curve (P = 0.12) between the two groups, and there was no difference in radiographic shoulder height (P = 0.5883). PATIENT OUTCOME: Both groups reported improvement in shoulder balance and clinical appearance, but there was no statistical difference between the two groups (P = 0.24). Additionally, no patients reported deterioration in either parameter. CONCLUSIONS: Spontaneous proximal thoracic curve correction consistently occurs after instrumented correction of the main thoracic curve. Furthermore, this spontaneous correction is as good as or slightly better after an ASF versus PSF of the MT curve. The preoperative side bender radiographs (PT curve flexibility) positively correlate with the postoperative spontaneous PT curve correction.