Spinal injury rates and specific causation in motor vehicle collisions.

Motor vehicle collisions (MVCs) are a leading cause of acute spinal injuries. Chronic spinal pathologies are common in the population. Thus, determining the incidence of different types of spinal injuries due to MVCs and understanding biomechanical mechanism of these injuries is important for distinguishing acute injuries from chronic degenerative disease. This paper describes methods for determining causation of spinal pathologies from MVCs based on rates of injury and analysis of the biomechanics require to produce these injuries. Rates of spinal injuries in MVCs were determined using two distinct methodologies and interpreted using a focused review of salient biomechanical literature. One methodology used incidence data from the Nationwide Emergency Department Sample and exposure data from the Crash Report Sample System supplemented with a telephone survey to estimate total national exposure to MVC. The other used incidence and exposure data from the Crash Investigation Sampling System. Linking the clinical and biomechanical findings yielded several conclusions. First, spinal injuries caused by an MVC are relatively rare (511 injured occupants per 10,000 exposed to an MVC), which is consistent with the biomechanical forces required to generate injury. Second, spinal injury rates increase as impact severity increases, and fractures are more common in higher-severity exposures. Third, the rate of sprain/strain in the cervical spine is greater than in the lumbar spine. Fourth, spinal disc injuries are extremely rare in MVCs (0.01 occupants per 10,000 exposed) and typically occur with concomitant trauma, which is consistent with the biomechanical findings 1) that disc herniations are fatigue injuries caused by cyclic loading, 2) the disc is almost never the first structure to be injured in impact loading unless it is highly flexed and compressed, and 3) that most crashes involve predominantly tensile loading in the spine, which does not cause isolated disc herniations. These biomechanical findings illustrate that determining causation when an MVC occupant presents with disc pathology must be based on the specifics of that presentation and the crash circumstances and, more broadly, that any causation determination must be informed by competent biomechanical analysis.

Ice hockey shoulder pad design and the effect on head response during shoulder-to-head impacts.

Ice hockey body checks involving direct shoulder-to-head contact frequently result in head injury. In the current study, we examined the effect of shoulder pad style on the likelihood of head injury from a shoulder-to-head check. Shoulder-to-head body checks were simulated by swinging a modified Hybrid-III anthropomorphic test device (ATD) with and without shoulder pads into a stationary Hybrid-III ATD at 21 km/h. Tests were conducted with three different styles of shoulder pads (traditional, integrated and tethered) and without shoulder pads for the purpose of control. Head response kinematics for the stationary ATD were measured. Compared to the case of no shoulder pads, the three different pad styles significantly (p < 0.05) reduced peak resultant linear head accelerations of the stationary ATD by 35-56%. The integrated shoulder pads reduced linear head accelerations by an additional 18-21% beyond the other two styles of shoulder pads. The data presented here suggest that shoulder pads can be designed to help protect the head of the struck player in a shoulder-to-head check.

The tolerance of the femoral shaft in combined axial compression and bending loading.

The likelihood of a front seat occupant sustaining a femoral shaft fracture in a frontal crash has traditionally been assessed by an injury criterion relying solely on the axial force in the femur. However, recently published analyses of real world data indicate that femoral shaft fracture occurs at axial loads levels below those found experimentally. One hypothesis attempting to explain this discrepancy suggests that femoral shaft fracture tends to occur as a result of combined axial compression and applied bending. The current study aims to evaluate this hypothesis by investigating how these two loading components interact. Femoral shafts harvested from human cadavers were loaded to failure in axial compression, sagittal plane bending, and combined axial compression and sagittal plane bending. All specimens subjected to bending and combined loading fractured midshaft, whereas the specimens loaded in axial compression demonstrated a variety of failure locations including midshaft and distal end. The interaction between the recorded levels of applied moment and axial compression force at fracture were evaluated using two different analysis methods: fitting of an analytical model to the experimental data and multiple regression analysis. The two analysis methods yielded very similar relationships between applied moment and axial compression force at midshaft fracture. The results indicate that posteroanterior bending reduces the tolerance of the femoral shaft to axial compression and that that this type of combined loading therefore may contribute to the high prevalence of femoral shaft fracture in frontal crashes.

Injury tolerance and moment response of the knee joint to combined valgus bending and shear loading.

Valgus bending and shearing of the knee have been identified as primary mechanisms of injuries in a lateral loading environment applicable to pedestrian-car collisions. Previous studies have reported on the structural response of the knee joint to pure valgus bending and lateral shearing, as well as the estimated injury thresholds for the knee bending angle and shear displacement based on experimental tests. However, epidemiological studies indicate that most knee injuries are due to the combined effects of bending and shear loading. Therefore, characterization of knee stiffness for combined loading and the associated injury tolerances is necessary for developing vehicle countermeasures to mitigate pedestrian injuries. Isolated knee joint specimens (n=40) from postmortem human subjects were tested in valgus bending at a loading rate representative of a pedestrian-car impact. The effect of lateral shear force combined with the bending moment on the stiffness response and the injury tolerances of the knee was concurrently evaluated. In addition to the knee moment-angle response, the bending angle and shear displacement corresponding to the first instance of primary ligament failure were determined in each test. The failure displacements were subsequently used to estimate an injury threshold function based on a simplified analytical model of the knee. The validity of the determined injury threshold function was subsequently verified using a finite element model. Post-test necropsy of the knees indicated medial collateral ligament injury consistent with the clinical injuries observed in pedestrian victims. The moment-angle response in valgus bending was determined at quasistatic and dynamic loading rates and compared to previously published test data. The peak bending moment values scaled to an average adult male showed no significant change with variation in the superimposed shear load. An injury threshold function for the knee in terms of bending angle and shear displacement was determined by performing regression analysis on the experimental data. The threshold values of the bending angle (16.2 deg) and shear displacement (25.2 mm) estimated from the injury threshold function were in agreement with previously published knee injury threshold data. The continuous knee injury function expressed in terms of bending angle and shear displacement enabled injury prediction for combined loading conditions such as those observed in pedestrian-car collisions.

Site, type, and local mechanism of tibial shaft fracture in drivers in frontal automobile crashes.

The location, type, and local mechanism of tibial shaft fracture were determined for 66 drivers injured in frontal automobile crashes. The results from the analyses showed that the distal third is the most common fracture location (p<0.05) and that bending is responsible for the majority of these fractures regardless of the fracture site. These findings indicate that the current injury criterion for predicting the occurrence of tibial shaft fracture in crash tests with anthropometric test devices is appropriate in terms of accounting for the primary mechanism of fracture but that increased protective effectiveness could be achieved by redefining the criterion for the distal third shaft section instead of the currently specified mid-shaft section of the tibia.

Influence of age-related stature on the frequency of body region injury and overall injury severity in child pedestrian casualties.

OBJECTIVE: The current study aims to evaluate the influence of age-related stature on the frequency of body region injury and overall injury severity in children involved in pedestrian versus motor vehicle collisions (PMVCs). METHODS: A trauma registry including the coded injuries sustained by 1,590 1- to 15-year-old pedestrian casualties treated at a level-one trauma center was categorized by stature-related age (1-3, 4-6, 7-9, 10-12, and 13-15 years) and body region (head and face, neck, thorax, abdomen and pelvic content, thoracic and lumbar spine, upper extremities, pelvis, and lower extremities). The lower extremity category was further divided into three sub-structures (thigh, leg, and knee). For each age group and body region/sub-structure the proportion of casualties with at least one injury was then determined at given Abbreviated Injury Scale (AIS) severity levels. In addition, the average and distribution of the Maximum Abbreviated Injury Score (MAIS) and the average Injury Severity Score (ISS) were determined for each age group. The calculated proportions, averages, and distributions were then compared between age groups using appropriate significance tests. RESULTS: The overall outcome showed relatively minor variation between age groups, with the average +/- SD MAIS and ISS ranging from 2.3 +/- 0.9 to 2.5 +/- 1.0 and 8.2 +/- 7.2 to 9.4 +/- 8.9, respectively. The subjects in the 1- to 3-year-old age group were more likely to sustain injury to the head, face, and torso regions than the older subjects. The frequency of AIS 2+ lower extremity injury was approximately 20% in the 1- to 3-year-old group, but was twice as high in the 4- to 12-years age range and 2.5 times as high in the oldest age group. The frequency of femur fracture increased from 10% in the youngest group to 26% in the 4- to 6-year-old group and then declined to 14% in the 10- to 15-years age range. The frequency of tibia/fibula fracture increased monotonically with group age from 8% in the 1- to 3-year-old group to 31% in the 13- to 15-year-old group. CONCLUSIONS: While the overall outcome of child pedestrian casualties appears to be relatively constant across the pediatric stature range considered ( approximately 74-170 cm), subject height seems to affect the frequency of injury to individual body regions, including the thorax and lower extremities. This suggests that vehicle safety designers need not only account for the difference in injury patterns between adult and pediatric pedestrian casualties, but also for the variation within the pediatric group.

Nonlinear viscoelastic behavior of human knee ligaments subjected to complex loading histories.

The nonlinear viscoelastic structural response of the major human knee ligaments when subjected to complex loading histories is investigated, with emphasis on the collateral ligaments. Bone-ligament-bone specimens are tested in knee distraction loading, where the ligaments are in the anatomical position corresponding to a fully extended knee. Temporal nonlinearities for time scales in the range of 1

Significance of adult pedestrian torso injury.

The current paper uses data from two trauma registries to evaluate the significance of adult pedestrian torso injury relative to head and lower extremity injuries and to determine the relative importance of injuries to individual torso organs/structures. Analyses are conducted with and without adjusting for striking vehicle body type (car versus LTV). Although the incidence of torso injury is approximately 50% higher in pedestrians struck by LTVs than in those struck by cars, torso injury appears to be as an important contributor to the overall cost of pedestrian morbidity as is lower extremity injury. The most frequently injured torso organs/structures include the rib cage, lung & pleura, and liver. The results indicate a need for an increased focus on the prevention of torso injury in the design of pedestrian safety countermeasures.

Pedestrian injuries: viscoelastic properties of human knee ligaments at high loading rates.

OBJECTIVE: Accidents involving pedestrians are very common, and often lead to severe injuries to the lower extremities. In a large portion of pedestrian-automobile collisions, knee ligament injuries are sustained. In this study, the viscoelastic properties of the four major human knee ligaments were investigated at loading rates representative for pedestrian-automobile collisions. METHODS: Bone-ligament-bone specimens were tested in knee distraction loading. The collateral ligaments and the separate functional bundles of the cruciate ligaments were tested in the anatomical position corresponding to a fully extended knee. A series of step-and-hold tests and ramp tests at different rates were conducted to characterize the time-dependent behavior of the knee ligaments for deformation rates associated with the pedestrian impact loading environment. The quasi linear viscoelastic (QLV) theory was used to describe the structural response of the knee ligaments and averaged parameters for this model were determined. RESULTS: The QLV theory was found to be applicable for the time range that is relevant for pedestrian-automobile collisions. The structural behavior of the knee ligaments was found to be particularly rate-sensitive for high elongation rates, as occur during these collisions. The ligament stiffness was found to increase with age for both the collateral ligaments and with weight for the medial collateral ligament. CONCLUSIONS: For the loading conditions that are relevant for pedestrian-automobile collisions, the use of the QLV model for the description of the mechanical behavior of knee ligaments is appropriate. The rate-sensitivity is particularly important for these extreme loading conditions. The relaxation behavior was found to be consistent between different ligament types and samples. Variations due to donor anthropometry were found predominantly for the instantaneous elastic behavior.

Integrated care in schizophrenia: a 2-year randomized controlled study of two community-based treatment programs.

OBJECTIVE: To evaluate the efficacy of two community-based programs that combined antipsychotic medication, family interventions and social skills training. METHOD: A randomized controlled trial with 2 years follow-up. The study included 84 patients with schizophrenic disorders, continuously managed in terms of care and treatment, and regularly assessed. Analysis was by intention-to-treat. RESULTS: Between-program comparisons showed significantly improved social function and consumer satisfaction in favour of the program 'Integrated Care' (IC) at the 2-year follow-up. The main clinically important differences between the two treatment programs studied were the procedures for shared decision making and patient empowerment in IC. CONCLUSION: The implementation of IC in clinical practice can improve social recovery and increase consumer satisfaction for patients with schizophrenic disorders. We identified specific procedures that might be added to improve the effectiveness of any program for severely mental ill people.

Impact of completion angiography on operative conduct and results of carotid endarterectomy.

OBJECTIVE: This study assessed the impact of operative completion angiography on conduct and results of carotid endarterectomy (CEA). SUMMARY BACKGROUND DATA: Completion imaging by angiography, ultrasound or angioscopy reveals occasional residual lesions after CEA. The importance and appropriate management of these lesions remain controversial with respect to operative morbidity and long-term restenosis. METHODS: Carotid endarterectomy was performed 410 times for transient ischemic attack (44%), amaurosis fugax (19%), prior stroke (10%), and asymptomatic carotid stenosis (27%). Routine intraoperative completion angiograms were obtained to exclude significant residual lesions. Postoperative ultrasound follow-up was obtained in 232 patients over a mean interval of 17.3 months. RESULTS: Angiography revealed 71 defects warranting correction in 66 cases (16.1%), including kinks (23), external carotid flaps (18), common carotid plaque (10), thrombus (10), distal internal carotid stenosis (8), intracranial occlusion (1), and spasm (1). Operative morbidity included seven ipsilateral strokes (1.7%) and operative mortality was 0.7%. During follow-up, restenosis > 80% was detected in 17 (7.3%) of 232 arteries, 9 (3.9%) of which underwent reoperation. Rates of restenosis of > 80% were similar between sexes and patched versus unpatched arteries. CONCLUSIONS: Routine completion angiography after CEA guides use of selective operative revision contributing to low rates of perioperative morbidity and restenosis.

Heparin fails to suppress intimal proliferation in experimental vein grafts.

Heparin has been shown to suppress both vascular smooth muscle cell proliferation in vitro and intimal hyperplasia in animal models of arterial injury. We investigated the effect of heparin on early postoperative smooth muscle cell proliferation and intimal thickening in vein grafts placed in the rat infrarenal aorta. Experimental animals (n = 6) received subcutaneous heparin (800 units/kg with levels monitored by activated factor X assay) every 12 hours for 3 days after surgery to coincide with the known period of maximal vascular wall DNA synthesis after injury. Control animals (n = 7) received identical vein grafts but no heparin. Grafts were harvested with perfusion fixation 14 days after insertion. Tritiated thymidine autoradiography was used to derive a mitotic index in regions of interest along the grafts, and computerized planimetric measurements of intimal and medial thickness were made in the same regions. Evans blue lumenal staining at harvesting revealed confluent endothelial coverage of both experimental and control grafts. The mitotic index of the vein graft's midsection and perianastomotic regions was significantly higher (p less than 0.005) than that of the native aorta in all animals, indicating cellular proliferation within all grafts, with no differences noted between heparinized and control animals. Similarly, both groups exhibited vein graft intimal and medial thickening at the anastomoses relative to the midsection of the vein graft (p less than 0.001). Heparin, administered in the equivalent of pharmacologic clinical doses, failed to suppress cellular proliferation and intimal hyperplasia in this model of vein grafting.

Real-time biospecific interaction analysis using surface plasmon resonance and a sensor chip technology.

We report here the development and application of a biosensor-based technology that employs surface plasmon resonance for label-free studies of molecular interactions in real time. The sensor chip interface, comprising a thin layer of gold deposited on a glass support, is derivatized with a flexible hydrophilic polymer to facilitate the attachment of specific ligands to the surface and to increase the dynamic range for surface concentration measurements. The sensor can be used to measure surface concentrations down to 10 pg/mm2. Typical coefficients of variation are from two to five percent. We anticipate that the ability to monitor multi-molecular complexes as they form will greatly contribute to the understanding of biorecognition and the structural basis of molecular function.

Fibronectin enhances early shear stress resistance of seeded adult human venous endothelial cells.

An in vitro parallel plate perfusion chamber was used to study the shear stress resistance of seeded adult human saphenous vein endothelial cells (AHSVECs) on glass surfaces coated with different substrates. Endothelial cells were seeded onto glass slides precoated with these substrates and then exposed to pulsatile flow with an average shear stress of 8 dyn/cm2 for 1 hr. After AHSVEC attachment periods of 15 min, 1 hr, and 2 hr, flow dislodged all but 1.4, 30.4, and 72.2%, respectively, of cells that had been seeded onto 1% gelatin. Control slides that were not exposed to flow retained 12.9% (P less than 0.03), 49.8% (NS), and 95.2% (NS) of seeded cells. Precoating the slides with 10 micrograms/ml fibronectin resulted in 69.4, 89.5, and 97.7% of cells remaining after flow, compared with 6.4% (P less than 0.03), 53.7% (NS), and 93.3% (NS), respectively, when using matched slides coated with 1% gelatin. Results with 20% fetal bovine serum as the substrate were not statistically different from those obtained with 1% gelatin. We conclude that fibronectin enhances the early attachment of AHSVECs to artificial surfaces and is, therefore, potentially useful for increasing attached cell yields on arterial prostheses prepared with immediate cell seeding techniques.

Recent experience with thoracoabdominal aneurysm repair.

Thoracoabdominal aneurysm repair was carried out in 55 patients during the period from January 1978 to June 1988. Considering the volume of experience and application of a routine for preoperative and intraoperative management, the experience was divided as follows: group 1 1978 to 1985 (26 patients) and group 2 1985 to 1988 (29 patients). Clinical features of the two groups differed only in the incidence of emergency operations (group 1 [6/18, 30%] vs group 2 [2/29, 8%]). Operative mortality in elective operations improved substantially in recent experience (group 1 [50%] vs group 2 [7.4%]). Significant reductions in total operative time, operative blood loss, and total aortic cross-clamping times paralleled and, in part, explained the improvement in overall surgical results seen in group 2 patients. Spinal cord injury occurred in 7.2% of the entire cohort. Nonfatal but major complications occurred in 25% of group 2 patients, with the most common being prolonged ventilatory assistance (12%). Current results with thoracoabdominal aneurysm repair both establish its safety and help to provide guidelines in selecting patients for elective repair.

Simultaneous carotid and coronary disease: safety of the combined approach.

Invoking unacceptable operative risks, many institutions have adopted a conservative policy toward carotid stenosis in patients who require cardiopulmonary bypass (CPB). We have continued to apply simultaneous carotid endarterectomy/coronary artery bypass grafting (CEA/CABG) in selected patients, and in order to place operative risk in perspective, our experience with CEA/CABG was reviewed and contrasted with both CEA and CABG performed as isolated procedures. Seventy-one CEA/CABG were performed from 1978 to 1987, with the bulk of the experience (51/71) accumulated over the past 5 years. CEA/CABG was applied when the carotid lesion was severe (greater than or equal to 75% diameter stenosis). Clinical characteristics of patients with CEA/CABG (e.g., presence of unstable angina, left main coronary artery disease, and impairment of ventricular function) suggested these patients were at higher risk for complications when compared to patients with CABG alone. Yet, other factors influencing stroke risk during cardiopulmonary bypass (patient age, duration of CPB time) were similar between patients with CEA/CABG and patients with only CABG. Most complications in patients with CEA/CABG occurred in the early years of the study. Considering the recent (1983-87) patient cohorts of CEA/CABG and isolated CABG, respectively, there was no significant difference in either operative mortality (2.0% as compared to 2.2%) or perioperative stroke (2.0% as compared to 0.6%). Whereas precise patient selection criteria remain undefined, these findings verify the safety of the combined CEA/CABG approach for most patients who require treatment of both lesions.

Monoclonal antibodies to GFAP epitopes available in formaldehyde fixed tissue.

We have recently demonstrated that one of our monoclonal antibodies (MAB's) to glial fibrillary acidic protein (GFAP) recognizes an epitope on this molecule which is to a large degree blocked during fixation with formaldehyde or crosslinking with Dithiobis (Succinimidyl) Propionate (DTSP). This was shown to be due to the crossbinding of a single or a number of proteins to the GFAP and is not due to a change in the epitope on GFAP induced by the fixation itself. In an attempt to produce further MAB's capable of recognizing epitopes on the GFAP molecule available following formaldehyde fixation, we immunized BALB-C mice with cytoskeletal preparations of human glioma cells which contain GFAP where the blocking protein or proteins were crossbound by DTSP or formaldehyde to the GFAP. Following fusion of the spleen lymphocytes to Sp 2/0 myeloma cells we have cloned hybridomas which produce antibodies that recognize GFAP in formaldehyde fixed tissues. This method presents the antigen in its native "fixed" state for the mouse's immune system and avoids the production of MAB's which (although excellent for immunochemical studies) do not recognize any epitopes available on the molecule in question in formaldehyde fixed tissues. Antibodies so produced are of great interest in routine pathology where most tissues are still, unfortunately, undiscriminately fixed in formalin. The results also show that GFAP varies immunologically in different species (i.e. human v. rat/mouse) and confirm that the GFAP of the PNS is immunologically distinct and/or associated with different proteins from that found in the CNS.

Complement deposition from human sera on silicon surfaces studied in situ by ellipsometry. The influence of surface wettability.

Organic material deposition from human sera on silicon dioxide surfaces was studied in situ by means of ellipsometry, an optical method for quantification of thin organic films. The deposition of organic material from sera was followed continuously for 2 h on hydrophobic and hydrophilic silicon surfaces. Both types of surfaces adsorbed organic material and the additional incubation with anti-C3 resulted in further deposition of organic material indicating the presence of C3 in the organic layers. Addition of EDTA in serum or heat inactivation resulted in a decrease of the amount of organic material deposited on the hydrophobic surface as well as in a lack of subsequent anti-C3 deposition on both hydrophilic and hydrophobic surfaces. Preadsorption with immunoglobulin G on the surfaces caused a pronounced increase of the deposition of material from serum as well as of subsequent anti-C3 deposition. Both effects were absent if EDTA was present in the serum. Our results indicate that complement activation and deposition occur by incubation of human sera on hydrophobic and hydrophilic silicon dioxide surfaces, which are two surfaces with very simple and well-defined chemical composition. The degree of the reversibility of the deposition of immunoglobulin G was furthermore larger on hydrophilic silicon.