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OBJECTIVE To simulate horizontally aligned head-first impacts with initial head protrusion using a human cadaveric neck model and to determine biomechanical responses, injuries, and injury severity. DESIGN Head-first impacts with initial head protrusion were simulated at 2.4 m/s using a human cadaver neck model (n = 10) mounted horizontally to a torso-equivalent mass on a sled and carrying a surrogate head. Macroscopic neck injuries were determined, and ligamentous injuries were quantified using fluoroscopy and visual inspection after the impacts. Representative time-history responses for injured specimens were determined during impact using load cell data and analyses of high-speed video. SETTING Biomechanics research laboratory. PARTICIPANTS Cervical spines of 10 human cadavers. MAIN OUTCOME MEASURES Injury severity at the middle and lower cervical spine was statistically compared using a 2-sample t test (P < 0.05). RESULTS Neck buckling consisted of hyperflexion at C6/7 and C7/T1 and hyperextension at superior spinal levels. Noncontiguous neck injuries included forward dislocation at C7/T1, spinous process fracture and compression-extension injuries at the middle cervical spine, and atlas and odontoid fractures. Ligamentous injury severity at C7/T1 was significantly greater than at the middle cervical spine. CONCLUSIONS Distinct injury mechanisms were observed throughout the neck, consisting of extension-compression and posterior shear at the upper and middle cervical spine and flexion-compression and anterior shear at C6/7 and C7/T1. Our experimental results highlight the importance of clinical awareness of potential noncontiguous cervical spine injuries due to head-first sports impacts.

Two case studies are presented involving fatal falls of adult females from a height. One involved a launch at low speed from a balcony, and one involved a launch at high speed from the top of a cliff. Crime scene evidence obtained on the balcony itself provided a strong indication of homicide, but subsequent investigation showed that the fall was accidental. No crime scene evidence was obtained for the cliff fall since the fall initially appeared to be just another suicide from a popular suicide spot. Subsequent investigations indicated homicide based on measurements of cliff height, horizontal distance to the impact, and available runup distance, plus measurements of possible run, jump, and throw speeds. It was found that a female weighing 61 kg (134 lb) can be thrown at speeds up to 4.85 m/s by a strong male, more than enough to account for the estimated launch speed (4.5 m/s). Given the available 4.0 m runup distance, it was found that women of better than average rather than elite athletic ability can dive at speeds of about 3.5 m/s or jump feet first at speeds of about 4.0 m/s, both being less than the estimated launch speed. The decedent had no athletic ability and landed head first after falling through a height of 29 m.

If mine were merely a mild head injury, which it was according to Scottish Intercollegiate Guidelines Network guidelines,1 I dare not think what a moderate or severe head injury must feel like. In May 2010, I was on Richard Roberts’ new sailing boat, returning from our triumph in the Scottish Islands Peaks Race, which combines sailing 140 miles with three mountain marathons (fastest monohull, third overall, top of our class). We were about to enter the Crinan Canal, the short cut from the Clyde to the west coast. It was raining, slippery on deck and there were ropes lying about. Presumably I slipped or tripped, no one is sure, but I definitely fell head first into the cockpit, hitting the left side of my head and ear, and shoulder. I was completely unconscious for about a minute, much to Richard's consternation, who thought I was dead. I came round with a sore head, a bleeding cut behind my ear and pretraumatic amnesia of seconds, comfortably above the ceiling of 15 on the Glasgow Coma Scale (GCS). I was really not too bad, able to go down into the cabin, and with help get my waterproofs and boots off, and lie down on a bunk. Within an hour I was reading the newspaper and regretting whatever stupidity had caused the fall. My left ear was a mess, bruised and bleeding from the cut inflicted by my glasses. After motoring along the Crinan Canal for a couple of hours, we had another think. We did not need a neurologist, we had two already—me and Richard. In any event, UK neurologists know little if anything about head injury and even less about ear injury (alas, the recent “The Bare Essentials of Head Injury” in Practical Neurology was not in the ship's library). …

Current understanding of the biomechanics of cervical spine injuries in head-first impact is based on decades of epidemiology, mathematical models, and in vitro experimental studies. Recent mathematical modeling suggests that muscle activation and muscle forces influence injury risk and mechanics in head-first impact. It is also known that muscle forces are central to the overall physiologic stability of the cervical spine. Despite this knowledge, the vast majority of in vitro head-first impact models do not incorporate musculature. We hypothesize that the simulation of the stabilizing mechanisms of musculature during head-first osteoligamentous cervical spine experiments will influence the resulting kinematics and injury mechanisms. Therefore, the objective of this study was to document differences in the kinematics, kinetics, and injuries of ex vivo osteoligamentous human cervical spine and surrogate head complexes that were instrumented with simulated musculature relative to specimens that were not instrumented with musculature. We simulated a head-first impact (3 m/s impact speed) using cervical spines and surrogate head specimens (n = 12). Six spines were instrumented with a follower load to simulate in vivo compressive muscle forces, while six were not. The principal finding was that the axial coupling of the cervical column between the head and the base of the cervical spine (T1) was increased in specimens with follower load. Increased axial coupling was indicated by a significantly reduced time between head impact and peak neck reaction force (p = 0.004) (and time to injury (p = 0.009)) in complexes with follower load relative to complexes without follower load. Kinematic reconstruction of vertebral motions indicated that all specimens experienced hyperextension and the spectrum of injuries in all specimens were consistent with a primary hyperextension injury mechanism. These preliminary results suggest that simulating follower load that may be similar to in vivo muscle forces results in significantly different impact kinetics than in similar biomechanical tests where musculature is not simulated.

An in vitro biomechanical study.To investigate atlas injury mechanisms due to horizontally aligned head-first impacts of a cadaveric neck model and to document atlas fracture patterns and associated injuries.Experimental atlas injuries have been created by applying compression or radial forces to isolated C1 vertebrae, dropping weight or applying sagittal moments to the upper cervical spine segments, or vertical drop testing of head-neck specimens or whole cadavers. Atlas injuries that commonly occur due to horizontally aligned head-first impacts have not been previously investigated.Horizontally aligned head-first impacts into a padded barrier were simulated at 4.1 m/s, using a human cadaver neck model mounted horizontally to a torso-equivalent mass on a sled and carrying a surrogate head. Atlantal radial force was computed using head and neck load cell data. Postimpact dissection documented atlas and associated injuries. Average atlantal radial force peaks and their occurrence times were statistically compared (P0.05) among the first local and global peaks using paired t tests.The first average local peak in radial atlantal force was significantly smaller (1240 vs. 2747 N) and occurred significantly earlier (24 ms vs. 46 ms) than the global force peak. Atlas injuries consisted of either 3- or 4-part burst fractures or incomplete lateral mass fracture unilaterally. Associated injuries included bony avulsion of the transverse ligament unilaterally and fractures of the occipital condyles, superior facets of the axis, or odontoid.The results indicated that the varied atlas fracture patterns were due primarily to radial forces causing outward lateral expansion of its lateral masses. Anterior and posterior arch fracture locations are dependent, in part, upon the cross-sectional arch dimensions. Transverse ligament rupture or bony avulsion is likely associated with real-life atlantal burst fractures.

Sperm competition favours an increase in sperm swimming velocity that maximises the chances that sperm will reach the ova before rival sperm and fertilise. Comparative studies have shown that the increase in sperm swimming speed is associated with an increase in total sperm size. However, it is not known which are the first evolutionary steps that lead to increases in sperm swimming velocity. Using a group of closely related muroid rodents that differ in levels of sperm competition, we here test the hypothesis that subtle changes in sperm design may represent early evolutionary changes that could make sperm swim faster. Our findings show that as sperm competition increases so does sperm swimming speed. Sperm swimming velocity is associated with the size of all sperm components. However, levels of sperm competition are only related to an increase in sperm head area. Such increase is a consequence of an increase in the length of the sperm head, and also of the presence of an apical hook in some of the species studied. These findings suggest that the presence of a hook may modify the sperm head in such a way that would help sperm swim faster and may also be advantageous if sperm with larger heads are better able to attach to the epithelial cells lining the lower isthmus of the oviduct where sperm remain quiescent before the final race to reach the site of fertilisation. © 2011 Society for Reproduction and Fertility.

This article describes the HEAD FIRST helmet safety program for preventing bicycling injuries in children. HEAD FIRST is an acronym for Helmet Education and Demonstration for Injury Reduction and Safety Training. The program includes 5 learning objectives, along with an outline of lesson content and teaching strategies. Information on the types of helmets and what to look for in a good helmet is covered. The proper fitting of a helmet is demonstrated on either the teacher or one of the students. Handouts distributed in class reinforce the messages of helmet safety. The authors report that bicycling accidents result in more than half a million visits to the emergency department for treatment of injuries each year. For children, the rate of injury is especially significant, with bicycles accounting for more injuries than any other mode of transportation except cars. The safety education program also teaches students how to identify safe and unsafe riding behavior by showing them brief video clips of bicyclists and helping them to clarify safe and unsafe practices. The program is designed for 8- to -10-year-olds.

International audience; Here presented is the case of a one-level jumping-fall with extensive skull fractures and brain expulsion. The body was found on the basement floor at the foot of the stairs. At the autopsy, the skull was extensively fractured, with about half of the brain expulsed several feet away from the body. The cause of death was established as a craniocerebral trauma with brain expulsion. The circumstances and manner of death were still unclear at that time. A low fall seemed very unlikely considering the severity of the skull and brain damage. The police investigation clearly revealed that the man, in a paranoid psychotic state, attacked his wife with a knife and then was witnessed by his children to have hit his head several times with a hammer. Afterwards, they saw him running to the top of the basement stairs and jumping to the bottom of the stairs head first.

Bungee jumping is a dangerous sport with increasing popularity in the western world. We report the case of a 28-yr-old man who sustained an orbital emphysema as a result of bungee jumping. He jumped head first from a 160-ft high bridge over a river. At the end of the jump he dived into the water with his head in a reclined position. The sudden dive into the water caused an increase of the air pressure in the nose and paranasal sinuses, which led to an emphysema of the right orbit resulting from a skull fracture not detectable by x-ray. The patient was treated with oral antibiotics. Five days later, he had no clinical complaints and the ophthalmologic examination was normal. This variation of bungee jumping may bear severe risk factors for health in addition to those known from the classic jumps. Language: en

The countermanding task requires subjects to cancel a planned movement on appearance of a stop signal, providing insights into response generation and suppression. Here, we studied human eye-head gaze shifts in a countermanding task with targets located beyond the horizontal oculomotor range. Consistent with head-restrained saccadic countermanding studies, the proportion of gaze shifts on stop trials increased the longer the stop signal was delayed after target presentation, and gaze shift stop-signal reaction times (SSRTs: a derived statistic measuring how long it takes to cancel a movement) averaged approximately 120 ms across seven subjects. We also observed a marked proportion of trials (13% of all stop trials) during which gaze remained stable but the head moved toward the target. Such head movements were more common at intermediate stop signal delays. We never observed the converse sequence wherein gaze moved while the head remained stable. SSRTs for head movements averaged approximately 190 ms or approximately 70-75 ms longer than gaze SSRTs. Although our findings are inconsistent with a single race to threshold as proposed for controlling saccadic eye movements, movement parameters on stop trials attested to interactions consistent with a race model architecture. To explain our data, we tested two extensions to the saccadic race model. The first assumed that gaze shifts and head movements are controlled by parallel but independent races. The second model assumed that gaze shifts and head movements are controlled by a single race, preceded by terminal ballistic intervals not under inhibitory control, and that the head-movement branch is activated at a lower threshold. Although simulations of both models produced acceptable fits to the empirical data, we favor the second alternative as it is more parsimonious with recent findings in the oculomotor system. Using the second model, estimates for gaze and head ballistic intervals were approximately 25 and 90 ms, respectively, consistent with the known physiology of the final motor paths. Further, the threshold of the head movement branch was estimated to be 85% of that required to activate gaze shifts. From these results, we conclude that a commitment to a head movement is made in advance of gaze shifts and that the comparative SSRT differences result primarily from biomechanical differences inherent to eye and head motion.

Objective To determine the method of sliding that propels the baseball athlete to the desired base in the shortest amount of time. To assess the athlete's perception of the quickest, safest, and preferred sliding technique. Design A single occasion with repeated measures design was used. The independent variable was slide type, and the dependent variable was time. Setting The study was conducted in October 2000 at the University of Kentucky baseball complex. Participants Twenty collegiate baseball players. Interventions High-speed video (to 1/200th of second) analysis of 20 collegiate baseball players performing 3 trials each of both head-first and feet-first sliding techniques. Additionally, each participant was asked to complete a sliding survey. Main outcome measures The videotape of each slide performed was reviewed separately (using the same viewing equipment) by 2 of the study investigators. Slide type and time were recorded for each slide. Results There was no significant difference between head-first versus feet-first slide times (P = 0.357). The average time for feet-first slides was 3.67 seconds, while that for head-first was 3.65 seconds. Sixty-eight percent of the players felt that head-first slides were faster than feet-first slides. Seventy-four percent identified the feet-first slide as the technique they most used, while 90% of the athletes perceived the feet-first technique to be safer. Conclusions On average, head-first and feet-first sliding techniques employed at the end aspect of base running propel the baseball player to the base in similar times. The head-first sliding technique is perceived to be faster and more dangerous.

Background Two basic baseball sliding techniques, feet-first and head-first, are taught at all levels of play. Because of the risk for injury to the upper extremities and the cervical spine during head-first sliding, it is potentially more dangerous than feet-first sliding. There is an assumption among coaches that head-first sliding is more aggressive and faster, but there has been no scientific study to prove this claim. Purpose The purpose of this study was to determine which technique provides a faster slide into the base. Study Design Controlled field study. Methods A total of 60 players ranging from Little League to college level was analyzed. Each athlete was evaluated three times from a standing start at first base to either a head-first or feet-first touch of second base. Each athlete was also timed in a 40-yard sprint and his or her preferred sliding technique was recorded. Results We found no statistically significant difference in speed between head-first and feet-first sliding at all levels of play in this study.

Wrist and hand injuries are common in elite divers, as all correctly performed dives end with a head first entry into the water with the hands extended above the head. This case presentation was an Olympic level diver with 3 months of persistent dorsal wrist pain. MRI findings showed contiguous contusions to the lunate, capitate, hamate and distal radius and also a peripheral tear of the ulnar attachment of the triangular fibrocartilage complex (TFCC). The repeated dorsiflexion stress of entry into the water likely caused these injuries. Although the authors had suspected a TFCC injury and did find an isolated ulnar-sided peripheral tear, the complicating carpal contusions led us to choose a conservative treatment plan, which was the only intervention the patient ultimately required.

The spear tackle is a tackling method employed by Rugby League players. In order to put the ball-holding player on the ground, he is up-ended and driven head first into the pitch with obvious high risk of cervical spine injury. This tackling technique is illegal but still occurs in the amateur and professional game. We report two cases of players sustaining fractures of the posterior elements of C5 after being spear tackled and illustrate difficulties in diagnosing this type of fracture from plain radiographs. The value of CT in cases of cervical spine trauma is demonstrated.

The investigation of sixty-one rheumatoid patients relates their hand function to measured hand deformity. Certain deformities are related to a reduction in function; others are not. The dominant hand, used more frequently, deteriorates more quickly than the non-dominant. The benefit on hand function of synovectomy is limited in duration and should be accompanied by some procedure to defer or correct deformity.Study of the metacarpophalangeal joints by radiography and at operation shows that degeneration starts where the metacarpal head first loses articulation with the base of the phalanx, and spreads out from there across the metacarpal head as deformity increases.

This report records the investigation into a high-speed hydroplane accident in which the driver died. He was ejected head first into the water at 117 to 126 ft/sec (80 to 85 mph), suffering brain damage and a fractured skull. Suggestions are made to minimize the effects of these inevitable crashes. Language: en