High-frequency, long-duration intracortical microstimulation (HFLD-ICMS) applied to motor cortex is recognized as a useful and informative method for corticomotor mapping by evoking natural-appearing movements of the limb to consistent stable end-point positions. An important feature of these movements is that stimulation of a specific site in motor cortex evokes movement to the same spatial end point regardless of the starting position of the limb. The goal of this study was to delineate effective stimulus parameters for evoking forelimb movements to stable spatial end points from HFLD-ICMS applied to primary motor cortex (M1) in awake monkeys. We investigated stimulation of M1 as combinations of frequency (30-400 Hz), amplitude (30-200 μA), and duration (0.5-2 s) while concurrently recording electromyographic (EMG) activity from 24 forelimb muscles and movement kinematics with a motion capture system. Our results suggest a range of parameters (80-140 Hz, 80-140 μA, and 1,000-ms train duration) that are effective and safe for evoking forelimb translocation with subsequent stabilization at a spatial end point. The mean time for stimulation to elicit successful movement of the forelimb to a stable spatial end point was 475.8 ± 170.9 ms. Median successful frequency and amplitude were 110 Hz and 110 μA, respectively. Attenuated parameters resulted in inconsistent, truncated, or undetectable movements, while intensified parameters yielded no change to movement end points and increased potential for large-scale physiological spread and adverse focal motor effects. Establishing cortical stimulation parameters yielding consistent forelimb movements to stable spatial end points forms the basis for a systematic and comprehensive mapping of M1 in terms of evoked movements and associated muscle synergies. Additionally, the results increase our understanding of how the central nervous system may encode movement.

High-frequency, long-duration intracortical microstimulation (HFLD-ICMS) is increasingly being used to deduce how the brain encodes coordinated muscle activity and movement. However, the full movement repertoire that can be elicited from the forelimb representation of primary motor cortex (M1) using this method has not been systematically determined. Our goal was to acquire a comprehensive M1 forelimb representational map of movement endpoints elicited with HFLD-ICMS, using stimulus parameters optimal for evoking stable forelimb spatial endpoints. The data reveal a 3D forelimb movement endpoint workspace that is represented in a patchwork fashion on the 2D M1 cortical surface. Although cortical maps of movement endpoints appear quite disorderly with respect to movement space, we show that the endpoint locations in the workspace evoked with HFLD-ICMS of two adjacent cortical points are closer together than would be expected if the organization were random. Although there were few obvious consistencies in the endpoint maps across the two monkeys tested, one notable exception was endpoints bringing the hand to the mouth, which was located at the boundary between the hand and face representation. Endpoints at the extremes of the monkey's workspace and locations above the head were largely absent. Our movement endpoints are best explained as resulting from coactivation of agonist and antagonist muscles driving the joints toward equilibrium positions determined by the length-tension relationships of the muscles.

Purpose: To compare publicly available rehabilitation protocols designated for meniscal repairs published online to determine the variability in meniscus repair protocols including different types of tears (radial vs nonradial repairs). Methods: From the Fellowship and Residency Electronic Interactive Database Access System (FREIDA), a list of publicly available academic residency programs and orthopaedic sports medicine fellowships was obtained. With this list, an electronic search using Google was performed looking for meniscal repair rehabilitation protocols. In addition to academic institutions, private practice organizations with published meniscus repair rehabilitation protocols found during the search also were examined. Results: Of 189 academic institutions, a total of 30 academic institutions had protocols that were included. Another 29 private practice programs were subsequently found and included. In total, 59 rehabilitation protocols fit the inclusion criteria. Six of the 59 specified radial repair and 53 did not. For return to full range of motion, nonradial protocols averaged 6.7 weeks and radial protocols averaged 7.3 weeks. For return to full weight-bearing, nonradial protocols averaged 6.2 weeks and radial protocols averaged 7.5 weeks. For return to sport, nonradial protocols averaged 17.8 weeks and radial protocols averaged 23.3 weeks. For time spent in a brace, nonradial protocols averaged 5.7 weeks and radial protocols averaged 6.7 weeks. Conclusions: Of publicly available meniscal repair rehabilitation protocols, a small percentage (10.2%) changed their protocol in relation to tear type and there was a wide range of timeframes for each rehabilitation component. Protocols for radial tears tended to brace patients longer, limit their range of motion longer, delay full weight-bearing, and delay return to sport. However, it is recognized that some surgeons could be modifying their protocols in relation to tear type without publishing that information online. Clinical Relevance: As stated in the purpose, the point of this study was to access only the protocols that would be available to the public. If anything, awareness should be raised for surgeons to look at their existing protocols and update them if they are truly incomplete and outdated. More research needs to be done to structure a rehabilitation protocol that is specific to the meniscal tear type, as the current protocols have a wide range of variance.

While a large body of evidence supports the view that ipsilateral motor cortex may make an important contribution to normal movements and to recovery of function following cortical injury (Chollet et al. 1991; Fisher 1992; Caramia et al. 2000; Feydy et al. 2002), relatively little is known about the properties of output from motor cortex to ipsilateral muscles. Our aim in this study was to characterize the organization of output effects on hindlimb muscles from ipsilateral motor cortex using stimulus-triggered averaging of EMG activity. Stimulus-triggered averages of EMG activity were computed from microstimuli applied at 60-120 μA to sites in both contralateral and ipsilateral M1 of macaque monkeys during the performance of a hindlimb push-pull task. Although the poststimulus effects (PStEs) from ipsilateral M1 were fewer in number and substantially weaker, clear and consistent effects were obtained at an intensity of 120 μA. The mean onset latency of ipsilateral poststimulus facilitation was longer than contralateral effects by an average of 0.7 ms. However, the shortest latency effects in ipsilateral muscles were as short as the shortest latency effects in the corresponding contralateral muscles suggesting a minimal synaptic linkage that is equally direct in both cases.

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