Hybrid Equation/Agent-Based Model of Ischemia-Induced Hyperemia and Pressure Ulcer Formation Predicts Greater Propensity to Ulcerate in Subjects with Spinal Cord Injury

Pressure ulcers are costly and life-threatening complications for people with spinal cord injury (SCI). People with SCI also exhibit differential blood flow properties in non-ulcerated skin. We hypothesized that a computer simulation of the pressure ulcer formation process, informed by data regarding skin blood flow and reactive hyperemia in response to pressure, could provide insights into the pathogenesis and effective treatment of post-SCI pressure ulcers. Agent-Based Models (ABM) are useful in settings such as pressure ulcers, in which spatial realism is important. Ordinary Differential Equation-based (ODE) models are useful when modeling physiological phenomena such as reactive hyperemia. Accordingly, we constructed a hybrid model that combines ODEs related to blood flow along with an ABM of skin injury, inflammation, and ulcer formation. The relationship between pressure and the course of ulcer formation, as well as several other important characteristic patterns of pressure ulcer formation, was demonstrated in this model. The ODE portion of this model was calibrated to data related to blood flow following experimental pressure responses in non-injured human subjects or to data from people with SCI. This model predicted a higher propensity to form ulcers in response to pressure in people with SCI vs. non-injured control subjects, and thus may serve as novel diagnostic platform for post-SCI ulcer formation. © 2013 Solovyev et al

Plantar loading during jumping while wearing a rigid carbon graphite footplate

Fifth metatarsal stress fractures are common in sports and often result in delayed and non-union. The purpose of this study was to examine the effect of a rigid carbon graphite footplate (CGF) on plantar loading during take-off and landing from a jump. Nineteen recreational male athletes with no history of lower extremity injury in the past 6 months and no foot or ankle surgery in the past 3 years participated in this study. Subjects completed 7 jumping tasks while wearing a standard running shoe and then the shoe plus the CGF while plantar loading data was recorded. A series of paired t-tests were used to examine differences between the two footwear conditions independently for both takeoff and landing (α=0.05). The contact area in the medial midfoot (p<.001) and forefoot (p=.010) statistically decreased when wearing the CGFP. The force-time integral was significantly greater when wearing the CGFP in the middle (p<.001) and lateral forefoot (p=.019). Maximum force was significantly greater beneath the middle (p<.001) and lateral forefoot (p<.001) when wearing the CGFP, while it was decreased beneath the medial midfoot (p<.001). During landing, the contact area beneath the medial (p=.017) and lateral midfoot (p=.004) were significantly decreased when wearing the CGFP. The force-time integral was significantly decrease beneath the medial midfoot (p<.001) when wearing the CGFP. The maximum force was significantly greater beneath the medial (p=.047) and middle forefoot (p=.001) when the subject was wearing the CGFP. The maximum force beneath the medial midfoot (p<.001) was significantly reduced when wearing the carbon graphite footplate. The results of the study indicate that the CGF is ineffective at reducing plantar loading during jumping and landing. © 2013 Elsevier B.V

Quality of Residual Neuromuscular Control and Functional Deficits in Patients with Spinal Cord Injury

Study Design: Prospective cohort study. Objective: This study examined the relationship between motor control and clinical function outcomes after spinal cord injury (SCI). Setting: University of Louisville, Louisville, KY, USA. Materials: Eleven persons with SCI and 5 non-injured subjects were included in this study. Methods: The ASIA Impairment Scale (AIS) was used to categorize injury level and severity. Multi-muscle, surface EMG (sEMG) recording, was carried out using a protocol of reflex and volitional motor tasks and was analyzed using a vector-based tool that calculates index values that relate a distribution of multi-muscle activation pattern of each SCI subject to the prototype obtained from non-injured subject group and presents overall magnitude as a separate value. Functional Independence Measure motor sub-scale, Spinal Cord Injury Independence Measure (SCIM-III), and Walking Index for Spinal Cord Injury (WISCI) scale scores were compared to neurophysiological parameters. Results: AIS category and injury level correlated significantly with the WISCI and SCIM mobility sub-scales. sEMG-derived parameters were significantly correlated with SCIM and WISCI scores but only for examinations carried out 48 or more days post-injury. Conclusion: These results supported the hypothesis that clinically relevant function after SCI is related to the degree to which functional organization within the central nervous system is disrupted. Further, due likely to the constraints placed on the expression of functional ability by early post-injury immobilization and hospitalization, neurophysiological assessment of motor function may provide better sensitivity and reliability than can be obtained using the clinical function scales examined here within the early period after injury

Functional Electric Stimulation Cycle Ergometry Training Effect on Lower Limb Muscles in Acute SCI Individuals

The purpose of this study was to compare three different intervals for a between sets rest period during a common isokinetic knee extension strength-testing protocol of twenty older Brazilian men (66.30 ± 3.92 yrs). The volunteers underwent unilateral knee extension (Biodex System 3) testing to determine their individual isokinetic peak torque at 60, 90, and 120° ·s-1. The contraction speeds and the rest periods between sets (30, 60 and 90 s) were randomly performed in three different days with a minimum rest period of 48 hours. Significant differences between and within sets were analyzed using a One Way Analysis of Variance (ANOVA) with repeated measures. Although, at angular velocity of 60°·s-1 produced a higher peak torque, there were no significant differences in peak torque among any of the rest periods. Likewise, there were no significant differences between mean peak torque among all resting periods (30, 60 and 90s) at angular velocities of 90 and 120°·s-1. The results showed that during a common isokinetic strength testing protocol a between set rest period of at least 30 s is sufficient for recovery before the next test set in older men

Neuropsychological, Psychosocial, and Mood Outcomes Following Mild Traumatic Brain Injury

Traumatic brain injury (TBI) in adolescents and adults can result in cognitive, emotional, behavioral and neurological deficits that can persist more than a year after an injury. The aim of the current preliminary study was to use a comprehensive neuropsychological assessment to determine the nature of cognitive impairments and their relationship with specific psychosocial factors, including coping skills and perceived quality of life, following mild TBI (mTBI). Neuropsychological tests administered measured intelligence, pre-morbid intelligence, executive functioning, verbal memory, complex visual construction and non-verbal memory, sustained attention distractibility, and vigilance, verbal learning and memory, fine motor speed, and novel problem solving and executive functioning. Psychological and life satisfaction measures assessed perceived quality of life, coping style, anxiety, and depression. MTBI subjects showed decreased attention, verbal and non-verbal memory, quality of life, and increased depression and anxiety when compared with healthy controls. Additionally, it was found that quality of life mediated the relationship between head injury and depression, anxiety, and attention. These findings may suggest that psychotherapy interventions may be able to improve quality of life and aspects of cognition following TBI

Plasma-based assays distinguish hyperfibrinolysis and shutdown subgroups in trauma-induced coagulopathy

BACKGROUND Trauma patients with abnormal fibrinolysis have increased morbidity and mortality. Knowledge of mechanisms differentiating fibrinolytic phenotypes is important to optimize treatment. We hypothesized that subjects with abnormal fibrinolysis identified by whole blood viscoelastometry can also be distinguished by plasma thrombin generation, clot structure, fibrin formation, and plasmin generation measurements. METHODS Platelet-poor plasma (PPP) from an observational cross-sectional trauma cohort with fibrinolysis shutdown (% lysis at 30 minutes [LY30] \u3c 0.9, n = 11) or hyperfibrinolysis (LY30 \u3e 3%, n = 9) defined by whole blood thromboelastography were studied. Noninjured control subjects provided comparative samples. Thrombin generation, fibrin structure and formation, and plasmin generation were measured by fluorescence, confocal microscopy, turbidity, and a fluorescence-calibrated plasmin assay, respectively, in the absence/presence of tissue factor or tissue plasminogen activator (tPA). RESULTS Whereas spontaneous thrombin generation was not detected in PPP from control subjects, PPP from hyperfibrinolysis or shutdown patients demonstrated spontaneous thrombin generation, and the lag time was shorter in hyperfibrinolysis versus shutdown. Addition of tissue factor masked this difference but revealed increased thrombin generation in hyperfibrinolysis samples. Compared with shutdown, hyperfibrinolysis PPP formed denser fibrin networks. In the absence of tPA, the fibrin formation rate was faster in shutdown than hyperfibrinolysis, but hyperfibrinolysis clots lysed spontaneously; these differences were masked by addition of tPA. Tissue plasminogen activator–stimulated plasmin generation was similar in hyperfibrinolysis and shutdown samples. Differences in LY30, fibrin structure, and lysis correlated with pH. CONCLUSION This exploratory study using PPP-based assays identified differences in thrombin generation, fibrin formation and structure, and lysis in hyperfibrinolysis and shutdown subgroups. These groups did not differ in their ability to promote tPA-triggered plasmin generation. The ability to characterize these activities in PPP facilitates studies to identify mechanisms that promote adverse outcomes in trauma

Cerebral Metabolic and Neuropsychological Outcomes Following Mild Traumatic Brain Injury

Traumatic brain injury (TBI) in adolescents and adults can result in cognitive, emotional, behavioral and neurological deficits that can persist more than a year after an injury. The current preliminary study used 3D magnetic resonance spectroscopic imaging (MRSI) and comprehensive neuropsychological assessment to determine if prolonged cerebral metabolic and cognitive alterations occur in individuals with persistent neurocognitive deficits following a mild TBI (mTBI). The current study evaluated the potential interactions between cerebral metabolism and neuropsychological performance, coping style, mood, and perceived quality of life in mTBI subjects with chronic post-concussive symptoms. The mTBI subjects performed worse than controls on neuropsychological measures, endorsed poorer mood and reported significantly poorer perceived quality of life than healthy controls. Additionally, cerebral metabolic differences were found between groups as well as significant interactions between neuropsychological performance and cerebral metabolism. The current findings may potentially guide future research to more eagerly strive to understand possible ways to alter cerebral metabolism, possibly through medication, diet, or other behavioural changes

Comparison of the case-time-control and the case-crossover design in estimating risk of injury for prescription medications using population databases

L'objectif de l'étude était de comparer les analyses de cas chassé-croisé (CCO) et de cas-contrôle du temps (CCT) afin d'évaluer la relation entre l'usage de prescriptions et le risque de blessures traumatiques en utilisant des bases de données populationnelles incluant les données du Registre de Traumatisme de Québec, d'hospitalisation du MED-ECHO et la RAMQ. Les cas ayant rapporté une blessure entre janvier-2000 et décembre-2000 ont été inclus dans l'analyse. Pour chaque cas, un contrôle a été apparié sur l'âge, le sexe, le niveau du centre de traumatologie et la date de sortie de l'hôpital. 2,417 cas et 2,417 contrôles ont été appariés dans l'étude. Les résultats ont démontré que l'analyse de CCO est 1,5 fois plus susceptible de produire une association négative pour le risque de blessure comparativement à l'analyse CCT. Un faible niveau d'accord (62.4%) sur les estimations des risques a également été évalué par les deux méthodes

Biomarkers, Concussions, and the Duty of Care

Article published in the Michigan State Law Review