Madelen Fahlstedt

Correlation between Injury Pattern and Finite Element Analysis in Biomechanical Reconstructions of Traumatic Brain Injuries

At present, Finite Element (FE) analyses are often used as a tool to better understand the mechanisms of head injury. Previously, these models have been compared to cadaver experiments, with the next step under development being accident reconstructions. Thus far, the main focus has been on deriving an injury threshold and little effort has been put into correlating the documented injury location with the response displayed by the FE model. Therefore, the purpose of this study was to introduce a novel image correlation method that compares the response of the FE model with medical images. The injuries shown on the medical images were compared to the strain pattern in the FE model and evaluated by two indices; the Overlap Index (OI) and the Location Index (LI). As the name suggests, OI measures the area which indicates both injury in the medical images and high strain values in the FE images. LI evaluates the difference in center of mass in the medical and FE images. A perfect match would give an OI and LI equal to 1. This method was applied to three bicycle accident reconstructions. The reconstructions gave an average OI between 0.01 and 0.19 for the three cases and between 0.39 and 0.88 for LI. Performing injury reconstructions are a challenge as the information from the accidents often is uncertain. The suggested method evaluates the response in an objective way which can be used in future injury reconstruction studies.

The protective effect of a helmet in three bicycle accidents—A finite element study

There is some controversy regarding the effectiveness of helmets in preventing head injuries among cyclists. Epidemiological, experimental and computer simulation studies have suggested that helmets do indeed have a protective effect, whereas other studies based on epidemiological data have argued that there is no evidence that the helmet protects the brain. The objective of this study was to evaluate the protective effect of a helmet in single bicycle accident reconstructions using detailed finite element simulations. Strain in the brain tissue, which is associated with brain injuries, was reduced by up to 43% for the accident cases studied when a helmet was included. This resulted in a reduction of the risk of concussion of up to 54%. The stress to the skull bone went from fracture level of 80 MPa down to 13-16 MPa when a helmet was included and the skull fracture risk was reduced by up to 98% based on linear acceleration. Even with a 10% increased riding velocity for the helmeted impacts, to take into account possible increased risk taking, the risk of concussion was still reduced by up to 46% when compared with the unhelmeted impacts with original velocity. The results of this study show that the brain injury risk and risk of skull fracture could have been reduced in these three cases if a helmet had been worn.

A national survey of traumatic brain injuries admitted to hospitals in Sweden from 1987 to 2010

Background: With an increasing and aging population, there is a global demand for improving the primary prevention strategies aimed at reducing traumatic brain injuries (TBIs). The objective of the present epidemiological study was to evaluate the pattern of TBI in Sweden over a 24 years period (1987-2010). Methods: The Swedish Hospital Discharge Register was used, where in-patient care with a main diagnosis of TBI according to ICD9/10 was included. External factors, age and gender distribution was evaluated. Results: A decreasing number of annual incidence was observed, that is, from 230 to 156 per 100,000 inhabitants. A steady decrease of concussion was observed while other intracranial injuries increased especially traumatic subdural hemorrhage and subarachnoid hemorrhage. The study identified 3 groups of patients - young, adults and elderly. The highest incidence and the largest increase of incidence were seen in the oldest age group (85+ years) while the population under 65 years had a decreasing incidence of TBI. The most frequent etiology was fall accidents (57%) with a relative constant trend over the study period. Conclusions: More effort should be focused on different strategies for different age groups, especially the elderly group. A well-planned strategy for primary prevention guidelines for different age groups will have the chance to further reduce not only the health-care costs but also complications among elderly care.

Comparison of Multibody and Finite Element Human Body Models in Pedestrian Accidents with the Focus on Head Kinematics

ABSTRACT Objective: The objective of this study was to compare and evaluate the difference in head kinematics between the TNO and THUMS models in pedestrian accident situations. Methods: The TNO pedestrian model (version 7.4.2) and the THUMS pedestrian model (version 1.4) were compared in one experiment setup and 14 different accident scenarios where the vehicle velocity, leg posture, pedestrian velocity, and pedestrians initial orientation were altered. In all simulations, the pedestrian model was impacted by a sedan. The head trajectory, head rotation, and head impact velocity were compared, as was the trend when various different parameters were altered. Results: The multibody model had a larger head wrap-around distance for all accident scenarios. The maximum differences of the heads center of gravity between the models in the global x-, y-, and z-directions at impact were 13.9, 5.8, and 5.6 cm, respectively. The maximum difference between the models in head rotation around the heads inferior–superior axis at head impact was 36°. The head impact velocity differed up to 2.4 m/s between the models. The 2 models showed similar trends for the head trajectory when the various parameters were altered. Conclusions: There are differences in kinematics between the THUMS and TNO pedestrian models. However, these model differences are of the same magnitude as those induced by other uncertainties in the accident reconstructions, such as initial leg posture and pedestrian velocity.

Learning through a virtual patient vs. recorded lecture : a comparison of knowledge retention in a trauma case

Objectives To compare medical students’ and residents’ knowledge retention of assessment, diagnosis and treatment procedures, as well as a learning experience, of patients with spinal trauma after training with either a Virtual Patient case or a video-recorded traditional lecture. Methods A total of 170 volunteers (85 medical students and 85 residents in orthopedic surgery) were randomly allocated (stratified for student/resident and gender) to either a video-recorded standard lecture or a Virtual Patient-based training session where they interactively assessed a clinical case portraying a motorcycle accident. The knowledge retention was assessed by a test immediately following the educational intervention and repeated after a minimum of 2 months. Participants’ learning experiences were evaluated with exit questionnaires. A repeated-measures analysis of variance was applied on knowledge scores. A total of 81% (n = 138) of the participants completed both tests. Results There was a small but significant decline in first and second test results for both groups (F(1, 135) = 18.154, p = 0.00). However, no significant differences in short-term and long-term knowledge retention were observed between the two teaching methods. The Virtual Patient group reported higher learning experience levels in engagement, stimulation, general perception, and expectations. Conclusions Participants’ levels engagement were reported in favor of the VP format. Similar knowledge retention was achieved through either a Virtual Patient or a recorded lecture.

Finite Element Analysis of Long Posterior Transpedicular Instrumentation for Cervicothoracic Fractures Related to Ankylosing Spondylitis

Study Design: Biomechanical finite element model analysis. Objectives: Spinal fractures related to ankylosing spondylitis (AS) are often treated by long posterior stabilization. The objective of this study is to develop a finite element model (FEM) for spinal fractures related to AS and to establish a biomechanical foundation for long posterior stabilization of cervicothoracic fractures related to AS. Methods: An existing FEM (consisting of 2 separately developed models) including the cervical and thoracic spine were adapted to the conditions of AS (all discs fused, C0-C1 and C1-C2 mobile). A fracture at the level C6-C7 was simulated. Besides a normal spine (no AS, no fracture) and the uninstrumented fractured spine 4 different posterior transpedicular instrumentations were tested. Three loads (1.5g, 3.0g, 4.5g) were applied according to a specific load curve. Results: All posterior stabilization methods could normalize the axial stability at the fracture site as measured with gap distance. The maximum stress at the cranial instrumentation end (C3-C4) was slightly greater if every level was instrumented, than in the skipped level model. The skipped level instrumentation achieved similar rotatory stability as the long multilevel instrumentation. Conclusions: Skipping instrumentation levels without giving up instrumentation length reduced stresses in the ossified tissue within the range of the instrumentation and did not decrease the stability in a FEM of a cervicothoracic fracture related to AS. Considering the risks associated with every additional screw placed, the skipped level instrumentation has advantages regarding patient safety.

A pilot evaluation of an educational program that offers visualizations of cervical spine injuries : medical students' self-efficacy increases by training

In this pilot study, a new method for visualization through imaging and simulation (VIS-Ed) for teaching diagnosis and treatment of cervical spine trauma was formatively evaluated. The aims were to examine if medical students’ self-efficacy would change by training using VIS-Ed, and if so these changes were related to how they evaluated the session, and the user interface (UI) of this program. Using a one-group, pre–post course test design 43 Swedish medical students (4th year, 17 males, 26 females) practiced in groups of three participants. Overall the practice and the UI were considered as positive experiences. They judged VIS-Ed as a good interactive scenario-based educational tool. All students’ self-efficacy increased significantly by training (p < 0.001). Spearman’s rank correlation tests revealed that increased self-efficacy was only associated with: how the session was compared to as expected (p < 0.007). Students’ self-efficacy increased significantly by training, but replication studies should determine if this training effect is gender-related.

Training diagnosis and treatment of cervical spine trauma using a new educational program for visualization through imaging and simulation (VIS): a first evaluation by medical students.

In this pilot study we investigated how medical students evaluated a VIS practice session. Immediately after training 43 students answered a questionnaire on the training session. They evaluated VIS as a good interactive scenario based educational tool.