Vertebral Level-dependent Kinematics of Female and Male Necks Under G+x Loading

ABSTRACT Introduction Size-matched volunteer studies report gender-dependent variations in spine morphology, and head mass and inertia properties. The objective of this study was to determine the influence of these properties on upper and lower cervical spine temporal kinematics during G+x loading. Methods Parametrized three-dimensional head-neck finite element models were used, and impacts were applied at 1.8 and 2.6 m/s at the distal end. Details are given in the article. Contributions of population-based variations in morphological and mass-related variables on temporal kinematics were evaluated using sensitivity analysis. Influence of variations on time to maximum nonphysiological curve formation, and flexion of upper and extension of the lower spines were analyzed for male-like and female-like spines. Results Upper and lower spines responded with initial flexion and extension, resulting in a nonphysiological curve. Time to maximum nonphysiological curve and range of motions (ROMs) of the cervical column ranged from 45 to 66 ms, and 30 to 42 deg. Vertebral depth and location of the head center of gravity (cg) along anteroposterior axis were most influential variables for the upper spine flexion. Location of head cg along anteroposterior axis had the greatest influence on the time of the curve. Both anteroposterior and vertical locations of head cg, disc height, vertebral depth, head mass, and size were influential for the lower spine extension kinematics. Conclusions Models with lesser vertebral depth, that is, female-like spines, experienced greater range of motions and pronounced nonphysiological curves. This results in greater distraction/stretch of the posterior upper spine complex, a phenomenon attributed to suboccipital headaches. Forward location of head cg along anteroposterior axis had the greatest influence on upper and lower spine motions and time of formation of the curve. Any increased anteroposterior location of cg attributable to head supported mass may induce greater risk of injuries/neck pain in women during G+x loading.

The Relationship Between Cardiorespiratory and Accelerometer-Derived Measures in Trail Running and the Influence of Sensor Location

Purpose: To examine the relationship between cardiorespiratory and accelerometer-derived measures of exercise during trail running and determine the influence of accelerometer location. Methods: Eight trail runners (7 males and 1 female; age 26 [5] y; maximal oxygen consumption [] 70 [6] mL·kg−1·min−1) completed a 7-km trail run (elevation gain: 486 m), with concurrent measurements of , heart rate, and accelerations recorded from 3 triaxial accelerometers attached at the upper spine, lower spine, and pelvis. External exercise intensity was quantified from the accelerometers using PlayerLoad™ per minute and accelerometry-derived average net force. External exercise volume was calculated using accumulated PlayerLoad and the product of average net force and duration (impulse). Internal intensity was calculated using heart rate and -metrics; internal volume was calculated from total energy expenditure (work). All metrics were analyzed during both uphill (UH) and downhill (DH) sections of the trail run. Results: PlayerLoad and average net force were greater during DH compared with UH for all sensor locations (P ≤ .004). For all accelerometer metrics, there was a sensor position × gradient interaction (F2,1429.003; P <.001). The upper spine was lower compared with both pelvis (P ≤ .003) and lower spine (P ≤ .002) for all accelerometer metrics during both UH and DH running. Relationships between accelerometer and cardiorespiratory measures during UH running ranged from moderate negative to moderate positive (r = −.31 to .41). Relationships were stronger during DH running where there was a nearly perfect correlation between work and impulse (r = .91; P < .001). Conclusions: Simultaneous monitoring of cardiorespiratory and accelerometer-derived measures during trail running is suggested because of the disparity between internal and external intensities during changes in gradient. Sensor positioning close to the center of mass is recommended.

900. Retrospective Review of Microbiological profile in Post Surgical Spine Infections and Assess the Appropriateness of Current Pre-Op Antibiotic Prophylaxis Policy

Background SSI is a devastating complication of spine surgery that results in significant morbidity as it requires prolonged antibiotic courses and multiple surgical debridements. It also increases the economic burden on the health care system. So, it becomes important to learn the microbiological profile and assess the current pro-op antibiotic prophylaxis policy. Methods All cases reported by the hospital infection control surveillance program based on CDC/NHSN Surveillance definitions between January 2017 and July 2019 were retrospectively reviewed for microbiological data and surgical characteristics using electronic medical record, and non-parametric test was used to assess the difference in proportional distribution of gram-negative organisms between upper and lower spine groups. Results Between January 2017 and July 2019, 3561 spine surgeries were performed, 51 cases of SSI were reported, and 50 patients have microbiological data available. The most commonly isolated organism was Staphylococcus aureus (38%), followed by Escherichia coli (12%). There was no statistical difference for the distribution of gram-negative organisms in upper spine (17) and lower spine (33) surgeries (29.4% vs 48.4%, P Value = 0.24). However total gram-negative organisms accounted for 42% cases and lower spine surgical procedures were more likely to be associated with mixed infections including both gram negative and gram-positive organisms (15.1% vs 0%). Cefazolin resistant gram-negative organisms accounted for 22% of all gram-negative infections. Our current pre-op antibiotic policy recommends cefazolin plus or minus vancomycin (If MRSA screen positive) and clindamycin plus vancomycin in patients with severe penicillin allergy. Table 1: Characteristics of the cultures Table: 2 Microorganisms isolated from 50 patients with post-surgical spine infections Figure 1: Proportional distribution of Micro-organisms between lower and upper spine (Percentage on left side and No. of positive cultures on right side) Conclusion Although gram-positive organism predominated, there was a substantial portion of gram-negative organisms in post-surgical spine infections. Cefazolin would cover at least half of the gram-negative organisms identified based on our antibiogram susceptibility pattern. However, in patients with penicillin allergy, our current recommended pre-operative antibiotic prophylaxis does not provide gram-negative coverage. We will therefore explore the value of adding an agent with gram negative coverage based on our institutional antibiogram. Disclosures All Authors: No reported disclosures

Assessment of Head Impacts and Muscle Activity in Soccer Using a T3 Inertial Sensor and a Portable Electromyography (EMG) System: A Preliminary Study

Heading the ball is an important skill in soccer. Head impacts are of concern because of the potential adverse health effects. Many elite players now wear GPS (that include inertial monitoring units) on the upper spine for location tracking and workload measurement. By measuring the maximum acceleration of the head and the upper spine, we calculated the acceleration ratio as an attenuation index for participants (n = 8) of different skill levels during a front heading activity. This would allow for in-field estimates of head impacts to be made and concussive events detected. For novice participants, the ratio was as high as 8.3 (mean value 5.0 ± 1.8), whereas, for experienced players, the mean ratio was 3.2 ± 1.5. Elite players stiffen the neck muscles to increase the ball velocity and so the torso acts as a support structure. Electromyography (EMG) signals that were recorded from the neck and shoulder before and after a training intervention showed a major increase in mean average muscle activity (146%, p = 3.39 × 10−6). This was accompanied by a major decrease in acceleration ratio (34.41%, p = 0.008). The average head-ball impact velocity was 1.95 ± 0.53 m/s determined while using optical motion capture. For this low velocity, the impact force was 102 ± 19 N, 13% of the published concussive force. The voluntary action of neck muscles decreases isolated head movements during heading. Coaches and trainers may use this evidence in their development of junior players.

Man with a Movie Camera: Economy of Movement and ASMR Videos on Youtube

The article examines the ASMR phenomena through the perspective of early USSR philosophy of technic, especially, of the constructivist movement (Gan, Ginzburg) and of works of film director Dziga Vertov. Autonomous sensory meridian response (ASMR) is a tingling sensation that typically begins on the scalp and moves down the back of the neck and upper spine. The aim of research is to reconstruct the notion of «movement», «machine» and «technique» in constructivist writings and to transfer this notion on contemporary media culture. For the analysis authors use ASMR videos on Youtube in order to discover new possible connotations of the term «movement» in a constructivist perspective. The ASMR phenomena could be considered as a merge of Haraway’s cyborg metaphor and the constructivist conception of domestic life, movement and technique.

Anterior Skull Base Reconstruction following Ablative Surgery for Osteoradionecrosis: Case Report and Review of Literature

Introduction: Osteoradionecrosis is one of many potentially severe complications of radiotherapy for nasopharyngeal carcinoma. Osteoradionecrosis of the skull base is life-threatening due to the critical proximity of the pathological process to vital structures, for example, the intracranial cavity, the upper spine, and major blood vessels. Reconstructive options following surgical debridement of the anterior skull base and upper spine osteonecrosis have been scarcely described in the literature. Case presentation and management: We present a rare case of osteoradionecrosis of the clivus and cervical vertebrae C1-C2 in a patient previously treated with chemoradiotherapy for nasopharyngeal carcinoma, presenting as severe soft tissue infection of the neck. Aggressive surgical debridement and reconstruction with a two-paddle free anterolateral thigh flap was performed using a combination of transcervical and transnasal endoscopic approaches. A novel endoscopic procedure in the sphenoid sinus enabled flap anchoring in this complex area. Discussion: Surgical modalities for osteoradionecrosis of the skull base and upper spine are discussed and review of the literature is presented. Conclusion: Reconstruction of the anterior skull base with a well-vascularized free flap following ablative surgery should be considered in management of life-threatening osteoradionecrosis of the area. Endoscopic opening of the sphenoid sinus and creating a funnel-shaped stem is a newly described technique that guarantees precise placement of the flap and is a valuable adjunct to the reconstructive armamentarium.