Iodinated contrast media: effect of osmolarity and injection temperature on erythrocyte morphology in vitro.

BACKGROUND: Some side effects of intravenously injected iodinated contrast media are thought to be linked to the biological properties of the various agents and their effect on blood components. PURPOSE: To assess the effect of osmolarity and injection temperature of iodinated contrast media on erythrocyte (RBC) morphology in vitro. MATERIAL AND METHODS: Blood from 20 volunteers was incubated with three different contrast media (320 mg I/ml iso-osmolar iodixanol, 300 mg I/ml low-osmolar iopromide, 300 mg I/ml low-osmolar iopamidol) injected at 37 degrees C, 43 degrees C, and 48 degrees C, and in two different volumes corresponding to the estimated concentration at the site of venous injection and after systemic distribution. After 10 min incubation, aliquots were removed for complete blood count analysis and blood smears. Two hematologists blindedly and independently reviewed all smears, and determined the grade of morphological RBC changes compared to a blank sample. RESULTS: There was excellent (kappa = 0.98) inter-reader correlation for grading RBC changes. At systemic concentration at 37 degrees C, the grade of RBC changes was significantly (P<0.05) less in blood samples exposed to iso-osmolar iodixanol (mean 0.21) as compared to low-osmolar iopromide (mean 0.26) and low-osmolar iopamidol (mean 0.58). These differences became more significant at higher volumes, corresponding to concentrations at the site of injection and higher injection temperatures. CONCLUSION: In vitro, RBC morphology is less affected by iso-osmolar as compared to low-osmolar contrast media. These differences become more significant at higher injection temperatures that are proposed to improve flow dynamics for high-speed injection.

Self-electroporation as a model for fusion pore formation.

The creation of a small opening called the fusion pore is a necessary prerequisite for neurotransmitter release from synaptic vesicles. It is known that high intensity electric fields can create pores in vesicles by a process called electroporation. Due to the presence of charged phosphatidylserine (PS) molecules on the inner leaflet of the cell membrane, an electric field that is strong enough to cause electroporation of a synaptic vesicle might be present. It was shown by K. Rosenheck [K. Rosenheck. Biophys J 75, 1237-1243 (1998)] that in a planar geometry, fields sufficient to cause electroporation can occur at intermembrane separations of less than approximately 3 nm. It is frequently found, however, that the cell membrane is not planar but caves inward at the locations where a vesicle is close to it. Indentation of the cell membrane in the fusion region was modelled as a hemisphere and a theoretical study of the electric field in the vicinity of the cell membrane taking into account the screening effect of dissolved ions in the cytoplasm was performed. It was discovered that fields crossing the electroporation threshold occurred at a distance of 2 nm or less, supporting the claim that electroporation could be a possible mechanism for fusion pore formation.

Cerebral concussion in athletes: evaluation and neuropsychological testing.

OBJECTIVE: To conduct a topic review of studies related to cerebral concussion in athletes, as an aid to improving decision-making and outcomes. METHODS: We review the literature to provide an historical perspective on the incidence and definition of and the management guidelines for mild traumatic brain injury in sports. In addition, metabolic changes resulting from cerebral concussion and the second-impact syndrome are reviewed, to provide additional principles for decision-making. Neuropsychological testing, as it applies to athletes, is discussed in detail, to delineate baseline assessments, the characteristics of the neuropsychological evaluation, the neuropsychological tests used, and the methods for in-season identification of cerebral concussion. Future directions in the management of concussions are presented. RESULTS: The incidence of cerebral concussions has been reduced from approximately 19 per 100 participants in football per season to approximately 4 per 100, i.e., 40,000 to 50,000 concussions per year in football alone. The most commonly used definitions of concussion are those proposed by Cantu and the American Academy of Neurology. Each has associated management guidelines. Concussion or loss of consciousness occurs when the extracellular potassium concentration increases beyond the upper normal limit of approximately 4 to 5 mmol/L, to levels of 20 to 50 mmol/L, inhibiting the action potential and leading to loss of consciousness. This phenomenon helps to explain the delayed effects of symptoms after trauma. CONCLUSION: Neuropsychological testing seems to be an effective way to obtain useful data on the short-term and long-term effects of mild traumatic brain injury. Moreover, knowledge of the various definitions and management strategies, as well as the utility of neuropsychological testing, is essential for those involved in decision-making with athletes with mild traumatic brain injuries.

Sex-related injury patterns among selected high school sports.

This cohort observational study was undertaken to test the hypothesis that the incidence of injuries for girls participating in high school sports is greater than that for boys. From 1995 through 1997, players were included in our study if they were listed on the school's varsity team roster for boys' or girls' basketball, boys' or girls' soccer, boys' baseball, or girls' softball. Injuries and opportunities for injury were recorded daily. Certified athletic trainers reported injury and exposure data. Based on 39,032 player-seasons and 8988 reported injuries, the injury rates per 100 players for softball (16.7) and for girls' soccer (26.7) were higher than for baseball (13.2) and boys' soccer (23.4). The knee injury rates per 100 players for girls' basketball (4.5) and girls' soccer (5.2) were higher than for their male counterparts. Major injuries occurred more often in girls' basketball (12.4%) and soccer (12.1%) than in boys' basketball (9.9%) and soccer (10.4%). Baseball players (12.5%) had more major injuries than softball players (7.8%). There was a higher number of surgeries, particularly knee and anterior cruciate ligament surgeries, for female basketball and soccer players than for boys or girls in other sports.

Groin and abdominal strain injuries in the National Hockey League.

OBJECTIVE: To analyze groin and abdominal strain injuries retrospectively among elite male hockey players in the National Hockey League (NHL) over six seasons of play (1991/92 to 1996/97). DESIGN: Retrospective case series design. SETTING: The NHL. PARTICIPANTS: The NHL participants were an inclusive sample of 7,050 NHL hockey players who played in the NHL from the 1991/92 to the 1996/97 seasons. A subset of 2,600 NHL hockey players who played from the 1995/96 to the 1996/97 seasons was further analyzed. MAIN OUTCOME MEASURES: The injury definition for groin/abdominal strain injury included any injury recorded as a muscle strain injury involving a muscle in any of the abdominal, hip flexor, or hip adductor muscle groups. Femoral, abdominal, and inguinal hernias were also included. Cumulative incidence rates over six seasons of play in the NHL and incidence densities over two seasons of play in the NHL are reported. Specific injury parameters examined included muscle region, time in season, type of session, reinjury, time period in session, position of play, player's experience, mechanism of injury, and time loss. RESULTS: A total of 617 groin/abdominal strain injuries were reported in the NHL over six seasons of play. The cumulative incidence rate in the NHL increased over 6 years of play from 12.99 injuries/100 players/year in the 1991/92 season to 19.87 injuries/100 players/year in the 1996/97 season. The rate of increase was 1.32 (95% confidence interval -0.58, 3.21) injuries/100 players/year. The incidence density of groin/abdominal injury during NHL training camp was five times that during the regular season and 20 times that during the postseason. The incidence density in the NHL during games was six times that during practice. The majority of injuries reported were adductor groin muscle strains. The proportion of injuries reported that were recurrent was 23.5%. There was no significant difference in proportion of injuries reported by time period within a session. The mechanism of injury recorded was noncontact in nature in >90% of injuries reported. Mean time loss due to injury was significantly greater for abdominal injuries (10.59 sessions) than for groin injuries (6.59 sessions). A conservative estimate of the impact of groin/abdominal injury on each NHL team is a game loss of 25 player games/year. CONCLUSION: The impact of groin and abdominal strain injury at an elite level of play in hockey is significant and increasing. Future research in this area is needed to identify risk factors and potentially implement prevention strategies to reduce groin and abdominal strain injury at all levels of play.

Traumatic brain injury in high school athletes.

CONTEXT: The potential seriousness of mild traumatic brain injury (MTBI) is increasingly recognized; however, information on the frequency of MTBI among high school athletes is limited. OBJECTIVE: To identify the type, frequency, and severity of MTBI in selected high school sports activities. DESIGN: Observational cohort study. SETTING AND PARTICIPANTS: Two hundred forty-six certified athletic trainers recorded injury and exposure data for high school varsity athletes participating in boys' football, wrestling, baseball and field hockey, girls' volleyball and softball, boys' and girls' basketball, and boys' and girls' soccer at 235 US high schools during 1 or more of the 1995-1997 academic years. MAIN OUTCOME MEASURES: Rates of reported MTBI, defined as a head-injured player who was removed from participation and evaluated by an athletic trainer or physician prior to returning to participation. National incidence figures for MTBI also were estimated. RESULTS: Of 23566 reported injuries in the 10 sports during the 3-year study period, 1219 (5.5%) were MTBIs. Of the MTBIs, football accounted for 773 (63.4%) of cases; wrestling, 128 (10.5%); girls' soccer, 76 (6.2%); boys' soccer, 69 (5.7%); girls' basketball, 63 (5.2%); boys' basketball, 51 (4.2%); softball, 25 (2.1%); baseball, 15 (1.2%); field hockey, 13 (1.1%); and volleyball, 6 (0.5%). The injury rates per 100 player-seasons were 3.66 for football, 1.58 for wrestling, 1.14 for girls' soccer, 1.04 for girls' basketball, 0.92 for boys' soccer, 0.75 for boys' basketball, 0.46 for softball, 0.46 for field hockey, 0.23 for baseball, and 0.14 for volleyball. The median time lost from participation for all MTBIs was 3 days. There were 6 cases of subdural hematoma and intracranial injury reported in football. Based on these data, an estimated 62816 cases of MTBI occur annually among high school varsity athletes participating in these sports, with football accounting for about 63% of cases. CONCLUSIONS: Rates of MTBI vary among sports and none of the 10 popular high school sports we studied is without the occurrence of an MTBI. Continued involvement of high school sports sponsors, researchers, medical professionals, coaches, and sports participants is essential to help minimize the risk of MTBI.

Injury patterns in selected high school sports: a review of the 1995-1997 seasons.

OBJECTIVE: To characterize the risk of injury associated with 10 popular high school sports by comparing the relative frequency of injury and selected injury rates among sports, as well as the participation conditions within each sport. DESIGN AND SETTING: A cohort observational study of high school athletes using a surveillance protocol whereby certified athletic trainers recorded data during the 1995-1997 academic years. SUBJECTS: Players listed on the school's varsity team rosters for football, wrestling, baseball, field hockey, softball, girls' volleyball, boys' or girls' basketball, and boys' or girls' soccer. MEASUREMENTS: Injuries and opportunities for injury (exposures) were recorded daily. The definition of reportable injury used in the study required that certified athletic trainers evaluate the injured players and subsequently restrict them from participation. RESULTS: Football had the highest injury rate per 1000 athlete- exposures at 8.1, and volleyball had the lowest rate at 1.7. Only boys' (59.3%) and girls' (57.0%) soccer showed a larger proportion of reported injuries for games than practices, while volleyball was the only sport to demonstrate a higher injury rate per 1000 athlete-exposures for practices than for games. More than 73% of the injuries restricted players for fewer than 8 days. The proportion of knee injuries was highest for girls' soccer (19.4%) and lowest for baseball (10.5%). Among the studied sports, sprains and strains accounted for more than 50% of the injuries, except in field hockey (45.7%). Of the injuries requiring surgery, 60.3% were to the knee. CONCLUSIONS: An inherent risk of injury is associated with participation in high school sports based on the nature of the game and the activities of the players. Therefore, injury prevention programs should be in place for both practices and games. Preventing reinjury through daily injury management is a critical component of an injury prevention program. Although sports injuries cannot be entirely eliminated, consistent and professional evaluation of yearly injury patterns can provide focus for the development and evaluation of injury prevention strategies.

Cumulative sleepiness, mood disturbance, and psychomotor vigilance performance decrements during a week of sleep restricted to 4-5 hours per night.

To determine whether a cumulative sleep debt (in a range commonly experienced) would result in cumulative changes in measures of waking neurobehavioral alertness, 16 healthy young adults had their sleep restricted 33% below habitual sleep duration, to an average 4.98 hours per night [standard deviation (SD) = 0.57] for seven consecutive nights. Subjects slept in the laboratory, and sleep and waking were monitored by staff and actigraphy. Three times each day (1000, 1600, and 2200 hours) subjects were assessed for subjective sleepiness (SSS) and mood (POMS) and were evaluated on a brief performance battery that included psychomotor vigilance (PVT), probed memory (PRM), and serial-addition testing, Once each day they completed a series of visual analog scales (VAS) and reported sleepiness and somatic and cognitive/emotional problems. Sleep restriction resulted in statistically robust cumulative effects on waking functions. SSS ratings, subscale scores for fatigue, confusion, tension, and total mood disturbance from the POMS and VAS ratings of mental exhaustion and stress were evaluated across days of restricted sleep (p = 0.009 to p = 0.0001). PVT performance parameters, including the frequency and duration of lapses, were also significantly increased by restriction (p = 0.018 to p = 0.0001). Significant time-of-day effects were evident in SSS and PVT data, but time-of-day did not interact with the effects of sleep restriction across days. The temporal profiles of cumulative changes in neurobehavioral measures of alertness as a function of sleep restriction were generally consistent. Subjective changes tended to precede performance changes by 1 day, but overall changes in both classes of measure were greatest during the first 2 days (P1, P2) and last 2 days (P6, P7) of sleep restriction. Data from subsets of subjects also showed: 1) that significant decreases in the MSLT occurred during sleep restriction, 2) that the elevated sleepiness and performance deficits continued beyond day 7 of restriction, and 3) that recovery from these deficits appeared to require two full nights of sleep. The cumulative increase in performance lapses across days of sleep restriction correlated closely with MSLT results (r = -0.95) from an earlier comparable experiment by Carskadon and Dement (1). These findings suggest that cumulative nocturnal sleep debt had a dynamic and escalating analog in cumulative daytime sleepiness and that asymptotic or steady-state sleepiness was not achieved in response to sleep restriction.

Vibrational normal modes and dynamical stability of DNA triplex poly(dA). 2poly(dT): S-type structure is more stable and in better agreement with observations in solution.

A normal-mode and statistical mechanical calculation was carried out to determine the vibrational normal modes, contribution of internal fluctuations to the free energy, and hydrogen bond disruption of DNA triplex poly(dA).2poly(dT). The calculation was performed on both the x-ray fiber diffraction model with a N-type sugar conformation, and a newly proposed model with a S-type sugar conformation. Our calculated normal modes for the S-type structure are in better agreement with observed IR spectra for samples in D2O solution. We also find that the contribution of internal fluctuations to free energy, premelting hydrogen bond disruption probability, and hydrogen bond melting temperatures for the Hoogsteen and Watson-Crick hydrogen bonds all show that the S-type structure is dynamically more stable than the N-type structure in a nominal solution environment. Therefore our calculation supports experimental findings that the triplex d(T)n.d(A)nd(T)n most likely adopts a S-type sugar conformation in solution or at high humidity. Our calculations, however, do not preclude the possibility of an N-type conformation at lower humidities.

Vibrational analysis of phosphorothioate DNA: II. The POS group in the model compound dimethyl phosphorothioate [(CH3O)2(POS)]-.

The results of Raman and Infrared (IR) spectroscopic investigations on the vibrational modes of dimethyl phosphorothioate (DMPS) anion, [(CH3O)2(POS)]-, are reported. Ab initio calculations of the vibrational modes, the IR and Raman spectra and the interatomic force constants of DMPS were performed. A normal mode calculation was performed and the results were used to calculate the potential energy distribution for the vibrational modes. This analysis shows that in DMPS the P-S stretching mode has a frequency of about 630 cm-1 and an angle bending mode involving the sulfur atom has a frequency of about 440 cm-1. The proposed vibrational mode assignments will serve as marker bands in the conformational studies of phosphorothioate oligonucleotides which play a central role in the novel antisense therapeutic paradigm.

A new self-report scale for assessment of adolescent psychopathology: factor structure, reliability, validity, and diagnostic sensitivity.

This paper describes four studies on self-reported problems in 2,243 adolescent males and females, 12 to 17 years of age. In Study 1, principal-axis factoring of 102 items covering 11 problem domains revealed six factors comprising 49.5% of the variance. Study 2 used confirmatory factor analysis of a 64-item reduced set on a new sample of 408 adolescents. Goodness-of-fit indicators suggested that the six-factor model had excellent fit to the data. Study 3 used data from the 2,157 adolescents used in the first two studies. Coefficient alphas ranged from .83 to .92. Median test-retest reliability for the six factors was .86. There was a consistent structure of the correlation matrix across age and gender. Study 4 was a study of criterion validity, using an additional sample of 86 children with attention-deficit hyperactivity disorder (ADHD). Sensitivity and specificity were high, with an overall diagnostic efficiency of 83%. This new self-report scale, the Conners/Wells Adolescent Self-Report of Symptoms (CASS), may provide a useful component of a multimodal assessment of adolescent psychopathology.

A review of selected noncontact anterior cruciate ligament injuries in the National Football League.

During five football seasons, from 1989 through 1993, 61 surgically proven, noncontact, anterior cruciate ligament injuries, were identified from among 22 National Football League teams. The variables of surface, shoe type, playing conditions, and whether or not the shoe was spatted were identified for each reported injury. Forty noncontact injuries occurred in conventional cleated shoes on natural grass, and 21 occurred on an artificial surface. Almost half of all injuries (47.5%) occurred during game-day exposures despite the fact that the practice versus game-day exposure rate was 5:1. Of these injuries, 95.2% (N = 58) occurred on a dry field. The factors of cleat and shoe type, type of surface (natural versus artificial), surface conditions (wet/dry), and the effect of "spatting" a shoe are presented. The significance of these factors and their likelihood to be associated with injury is analyzed by use of a statistical tool, the incidence density ratio.

Hydration of single-stranded phosphodiester and phosphorothioate oligodeoxyribonucleotides.

Infrared spectroscopy was used to identify hydration-sensitive structural differences between single- stranded phosphorothioate (PS) and phosphodiester (PO) oligodeoxyribonucleotides. Spectra were recorded in the mid-infrared region, 500-1800 cm-1, at relative humidities between 0 and 98%; the PS and PO spectra are substantially different. The hydration effects on spectral bands in these single-stranded oligodeoxyribonucleotides is markedly different from such behavior in double- and triple-stranded oligodeoxyribonucleotides. A strong absorption occurs at 656 cm-1 in the phosphorothioate sample which is completely absent from the PO spectra. Gravimetric measurements were carried out on one PS and one PO sample to monitor and confirm hydration. The calculated BET adsorption constants [Brunauer, S., Emmett, RH. and Teller, E. (1938) J. Am. Chem. Soc., 60, 309-319] are 1.2 and 1.4 water molecules per nucleotide in the first hydration layer of PS and PO respectively. While the gravimetric data indicate that the single-stranded oligodeoxyribonucleotides hydrate very similarly to duplex DNA, the mid-infrared conformational marker bands are strikingly different from those observed for duplex DNA. In particular, the Vas of the phosphate group (PO2) at 1222 cm-1 in the single-stranded PO spectra is independent of relative humidity.

Adolescent depression: effects of mutuality in the mother-adolescent dyad and locus of control.

A group of 213 adolescents and their mothers participated in a study of the combined relationship between gender, locus of control, and perceived mutuality in the mother/adolescent dyad and self-rated adolescent depression. High mutuality and internal locus of control were significantly related to low levels of depression for both female and male adolescents. The study findings are considered in the context of current theoretical work on female relational psychology.

Observation of the hydration-dependent conformation of the (dG)20.(dG)20(dC)20 oligonucleotide triplex using FTIR spectroscopy.

The triple-helical oligonucleotide (dG)20.(dG)20(dC)20 was investigated using FTIR spectroscopy. Mid-infrared spectra were collected at nine relative humidities (RH) between 0% and 98%. The highest humidity spectrum agrees with the solution spectrum of a polynucleotide (dG)n.(dG)n(dC)n triplex [Quali, M., Letellier, R., Sun, J. S., Akhebat, A., Adnet, F., Liquier, J., & Taillandier, E. (1993) J. Am. Chem. Soc. 115, 4264-4270]. A dramatic transition in the vibrational state of the molecule has been observed between 88% and 92% RH. Theoretical predictions concerning the effects of hydration on a (dG).(dG)-(dC) oligonucleotide triplex [Laughton, C. A., & Neidle, S. (1992) Nucleic Acids Res. 20, 6535-6541; Mohan, V., Smith, P.E., & Pettitt, M.B. (1993) J. Am. Chem. Soc. 115, 9297-9298] have been considered and compared to our results. The infrared marker bands for the conformation of the glycosidic bond are absent below 92% RH, although dramatic hydration-dependent vibrational changes have been observed in the spectral regime traditionally associated with the glycosidic linkages. The effect of water in the Watson-Hoogsteen groove upon the vibrational state of the triplex has been observed for the first time. Hydration-induced changes in vibrational state have also been observed in the base residues, the phosphodiester backbone, and the furanose rings of the oligonucleotide sample.

Fractal-like patterns in DNA films, B form at 0% relative humidity, and antiheteronomous DNA: an IR study.

This report details the observation of (a) the intact double helix of DNA at 0% relative humidity in poly(dA).poly(dT) and poly(dA-dT).poly(dA-dT) films, (b) the fractal-like growth of DNA crystals in films of poly(dA).poly(dT), and (c) poly(dA).poly(dT) with adenines in the B form and thymines in the A form. Observation (a) is based on the behavior of the middle ir signature of double-helical base stacking, the 1714 cm-1 peak, at low water activity. This observation is modeled as a trapping of water in the polycrystalline part of these films. We interpret the glycosidic region of the middle ir spectra of the polycrystalline films of poly(dA).poly(dT) at 0% relative humidity to indicate that at least part of the adenine strand in is the B conformation and the thymine strand is in the A form, whereas previous assignments of poly(dA).poly(dT) films at 75% relative humidity indicated the opposite strand conformation assignment [E. Taillandier et al. (1987) Biochemistry, Vol. 26 p. 3361].

Study designs and potential biases in sports injury research. The case-control study.

Several different epidemiological study designs can be used for aetiological investigations of potential risk factors for the occurrence of sports injuries. The case-control study is an example of a retrospective design in which the investigator starts with the classification of injury status (case or control) and obtains information regarding prior exposure to risk factors. Several decisions need to be made when designing case-control studies. Firstly, the source of the study participants needs to be considered. Cases and controls need to be identified from the same source, i.e. same sport or clinic. Secondly, the same eligibility criteria need to be applied to potential cases and controls. Thirdly, when an injury occurred must be established. The fourth issue concerns the status of cases (incident or prevalent cases). Finally, the number and size of the control groups needs to be determined. Strengths of the case-control study design are the high level of information obtained, the relatively low cost and its usefulness for studying rare sports injuries. The higher susceptibility to bias is one of the limitations of case-control studies. Bias in a case-control study can lead to over or underestimation of the true association between an alleged risk factor and the occurrence of sports injuries. Three types of bias have been distinguished: (i) selection bias; (ii) information bias; and (iii) confounding. Furthermore, the applicability of this type of design is limited to risk factors that remain relatively stable after the occurrence of an injury. The effect of changeable risk factors, such as quadriceps strength and range of motion, is difficult to assess since in many cases data at the time of injury are unavailable.

Midfoot sprains in collegiate football players.

We studied midfoot sprains in collegiate football players to define and document incidence, mechanisms, injury patterns, and disabilities. Twenty-three athletes with 24 injuries from 1987 through 1991, with a mean followup of 30.8 months, were identified for the study. The injuries occurred in 4% of the football players per year with offensive linemen incurring 29.2% of the injuries. The location of maximal tenderness on physical examination was an important prognostic indicator such that injuries with medial and global midfoot tenderness to palpation had the longest time loss from participation and time until full healing. Lateral midfoot sprains required short periods of disability, and players were able to return to participation with the use of an orthosis. Nineteen athletes with 20 injuries responded to a questionnaire. Four players reported residual functional problems. Only 1 of these players had to modify his recreational activities because of pain. The other players remained very active with only mild complaints of pain after high-demand activities. Midfoot sprains were associated with acute disability that required prolonged restriction from competition, but for most players the long-term residual problems were minor.

Cervical spinal stenosis and stingers in collegiate football players.

We evaluated the relationship of cervical spinal stenosis with the occurrence of "stingers" in collegiate football players who participated at our institution from 1987 through 1991. Preparticipation cervical spine radiographs of 266 players were used to measure Torg ratio. Forty players with stingers were identified: 34 had an extension-compression mechanism; 6 had a brachial plexus stretch mechanism. Time-loss neck injuries occurred in 31 players; the remaining 195 players were asymptomatic. The mean Torg ratio was significantly smaller for the stinger group (P = 0.02). The Torg ratio was less than 0.8 at 1 or more levels in 47.5% of the stinger group, 32.3% of the time-loss neck pain group, and 25.1% of the asymptomatic group. No player with a brachial plexus stretch mechanism had a mean Torg ratio less than 0.8, but 20.6% of the players with an extension-compression mechanism had a mean Torg ratio less than 0.8. Players with a Torg ratio less than 0.8 had 3 times the risk of incurring stingers. We conclude that cervical spinal stenosis increases the risk for having stingers with complicated clinical courses.

Medial collateral ligament knee sprains in college football. Effectiveness of preventive braces.

This is the second of 2 articles on a 3-year investigation of medial collateral ligament sprains of the knee to assess the effectiveness of prophylactic knee braces in NCAA Division I college football players. Position, string, type of session, and daily brace wear were recorded. The injury rates for braced and unbraced knees were used to create an incidence density ratio. The data were stratified and simultaneously controlled for position, string, and session and evaluated for their statistical significance. The 987 Big Ten players generated 155,772 knee exposures over the study period (50% braced). Noticeable differences existed in the rates of injury for the braced and unbraced knees in almost every position during practices, depending on player or nonplayer status. When the influential factors of position, string, and session are considered, there is a consistent but not statistically significant tendency for the players wearing preventive knee braces to experience a lower injury rate than for their unbraced counterparts. For starters and substitutes in the line positions, as well as the linebackers and tight ends, there was a consistent trend toward a lower injury rate in both practices and games. The braced players in the skill positions (backs/kickers), at least during games, exhibited a higher injury rate.