Considering Pedicle Screw Resistance in Electromyography of the Spine

BACKGROUND Evoked electromyographic (EMG) monitoring of pedicle screws has been shown to be an effective adjuvant to image guidance or direct visualization of pedicle screw placement. Electrical stimulation is delivered to the head of the screw at various intensities until a muscle potential is evoked. This practice is based on the fact that an intact pedicle effectively shields nerve roots from electrical stimulus. Several factors have been debated that may affect the interpretation of results; however, to the best of our knowledge, the electrical resistance of modern manufactured pedicle screws and stimulation devices has not been studied. OBJECTIVE To determine if pedicle screw resistances affect triggered EMG. METHODS Samples of the most commonly implanted pedicle screws in Canada were obtained, with diameters ranging from 4.5 to 7 mm. The resistance between the screw head and thread and core at the midpoint and tip of the screw was recorded using a Multimeter in accordance with IEEE standards. For screws with variable threads, the midpoint was considered the point at which the thread pitch changed. RESULTS All screws had low impedances when tested at the point of the screw, but much higher when the cup is tested. The resistance of different manufactures' screws was significantly different, ranging from 0.514 to 2156 Ohms. CONCLUSION Despite differences in resistance, most screws had resistances in ranges that allow for triggered EMG pedicle integrity testing. Resistance from pedicle screws is an important consideration in EMG monitoring of the spine.

Effects of bicycle geometry and riding position on the potential of residual limb muscles to pedaling with a transfemoral prosthesis: a computer simulation study

We performed musculoskeletal simulations to provide information on the effects of riding position and bicycle geometry on pedaling with a transfemoral prosthesis. Sixty-four models and their corresponding kinematics in one pedaling cycle were generated from the baseline one-leg cycling model by varying one of the six variables (seat height, seat-tube angle, crank length, pelvic tilt, anteroposterior seating position, and thigh length relative to the leg). Induced acceleration analysis was performed to compute the potentials of the residual hip muscles for crank rotation in each model. The simulation results quantified the effects of each variable on the hip and knee kinematics and muscle potential during a pedaling cycle; seat height, crank length, and pelvic tilt were the primary candidates for bicycle fitting considering their accessibility and simple effects on the joint kinematics and muscle potential. The seat-tube angle (similar to pelvic tilt) and the anteroposterior seating position (similar to seat height and seat-tube angle) seemed to have an effect similar to the other variables and thus can be reserved for fine-tuning after gross fitting of the bicycle. Although not considered for adjustment, considering the effects of the thigh length could help as it affects hip kinematics and muscle potentials.

DIFFERENCES BETWEEN LOWER BODY MUSCLE POTENTIAL DURING UNLOADED AND LOADED SQUAT JUMP IN ELITE MALE SPRINT SWIMMERS

The primary purpose was to determine differences between lower body muscle potential during the unloaded and loaded squat jump (SJ) in elite male swimmers. The secondary purpose was to assess the load that would maximize power output in the SJ. Twenty-one elite male trained competitive swimmers, all members of the Central Serbia Swimming Team (Age = 20.7 ± 3.8 yrs., Height = 1.84 ± 0.56 m, Weight = 77.5 ± 7.3 kg, FINA points 2017 long course = 636 ± 80) performed two trials of the unloaded and loaded SJ (barbell loads equal to 25 and 35% body weight). Loaded SJ testing with free weights was done using the Smith machine. The Myotest performance measuring system was used to calculate absolute and relative values of average power (Pavg, PavgRel) and maximal power (Pmax, PmaxRel) achieved during the unloaded and loaded SJ. The one-way ANOVA method and POST HOC (Tukey HSD) test were used. The results showed significant interactions between the unloaded and loaded squat jump for relative values of maximal power (F= 12.95, p= 0.000) and average power (F= 12.20, p= 0.000) as well as absolute values (F= 7.66, p= 0.001; F= 7.40, p= 0.001). The instantaneous power output in the SJ at 0% additional load (body weight) was significantly greater than that at 25% and 35% in the elite male trained competitive swimmers. The practical application of this study suggests that for male sprint swimmers, the load that generates maximal power output in the squat jump is body weight, without any additional load.

Long non-coding RNAs (lncRNAs) in skeletal and cardiac muscle: potential therapeutic and diagnostic targets?

The recent discovery that thousands of RNAs are transcribed by the cell but are never translated into protein, highlights a significant void in our current understanding of how transcriptional networks regulate cellular function. This is particularly astounding when we consider that over 75% of the human genome is transcribed into RNA, but only approximately 2% of RNA is translated into known proteins. This raises the question as to what function the other so-called ‘non-coding RNAs’ (ncRNAs) are performing in the cell. Over the last decade, an enormous amount of research has identified several classes of ncRNAs, predominantly short ncRNAs (<200 nt) that have been confirmed to have functional significance. Recent advances in sequencing technology and bioinformatics have also allowed for the identification of a novel class of ncRNAs, termed long ncRNA (lncRNA) (>200 nt). Several studies have recently shown that long non-coding RNAs (lncRNAs) are associated with tissue development and disease, particularly in cell types that undergo differentiation such as stem cells, cancer cells and striated muscle (skeletal/cardiac). Therefore, understanding the function of these lncRNAs and designing strategies to detect and manipulate them, may present novel therapeutic and diagnostic opportunities. This review will explore the current literature on lncRNAs in skeletal and cardiac muscle and discuss their recent implication in development and disease. Lastly, we will also explore the possibility of using lncRNAs as therapeutic and diagnostic tools and discuss the opportunities and potential shortcomings to these applications.