Impact of further injury on participation in work and activities among those previously injured: results from a New Zealand prospective cohort study.

PURPOSE: To examine participation in paid work, unpaid work and activities 12 months after a sentinel (initial) injury, and to determine the impact of sustaining a subsequent injury (SI) on these participation outcomes. METHODS: Participants were recruited to the Prospective Outcomes of Injury Study following an Accident Compensation Corporation (ACC; New Zealand's no-fault injury insurer) entitlement claim injury. Outcomes were whether participants reported reduced paid work hours, reduced unpaid work (e.g. housework, gardening) or reduced activities (e.g. socialising, leisure pursuits) at 12 months compared to before the sentinel injury event. SIs were ACC claims of any type. Using multivariable models, characteristics of SIs were examined as potential predictors of reduced participation. RESULTS: At 12 months, 30% had reduced paid work hours, 12% had reduced unpaid work and 25% had reduced activities. Sustaining a SI predicted reduced paid work (RR 1.5; 95% CI 1.2, 1.8), but not unpaid work or activities. Participants who had sustained intracranial SIs were at highest risk of reduced paid work (RR 3.2, 95% CI 1.9, 5.2). Those sustaining SIs at work were less likely to have reduced paid work (RR 0.7; 95% CI 0.6, 1.0) than those with only non-work SIs. Participants sustaining assaultive SIs had higher risk of reduced unpaid work (RR 2.6, 95% CI 1.0, 6.8). CONCLUSIONS: Reduced participation is prevalent after a substantive sentinel injury, and sustaining a SI impacts on return to paid work. Identification of SI characteristics that put people at high risk of participation restriction may be useful for focusing on rehabilitative attention.

Two years after injury: prevalence and early post-injury predictors of ongoing injury-related problems.

PURPOSE: To determine, in a cohort with injuries classified anatomically as mainly minor or moderate and for which only 25% were hospitalised acutely, the prevalence of ongoing problems attributed by participants to their injury 2 years prior, and to examine whether three-month post-injury experiences and expectations predict such problems. METHODS: Participants (N = 2231; 18-64 years at injury) were those in the Prospective Outcomes of Injury Study who completed the initial three-month and final two-year interviews. The outcome measure was whether participants reported ongoing injury-related problems at 2 years. Possible early post-injury predictors were identified from the first interview; pre-injury and injury-related potential confounders from the first interview, insurer records and hospital discharge records. Multivariable models estimated relative risks. RESULTS: Almost half the participants reported injury-related problems at 2 years. Participants reporting non-recovery at 3 months were more likely than those reporting recovery to have ongoing problems at 2 years, ranging from participants expecting to get better soon [adjusted RR 2.2, 95% CI (1.7,2.8)) to those expecting to never get better (aRR 3.1, 95% CI (2.4,4.0)]. Several three-month post-injury experiences also predicted ongoing problems at 2 years. Participants at highest risk included those with extreme pain [aRR 2.1, 95% CI (1.7,2.5)], and less involvement in usual activities [aRR 1.7, 95% CI (1.5,1.9)]. CONCLUSIONS: Findings indicate that early post-injury characteristics predict longer-term recovery among this cohort, most of who were not classified as seriously injured, and provide guidance for future studies on interventions to reduce poor outcome prevalence, particularly focussing on pain management and enabling return to independence and social participation.

Prevalence of poor outcomes soon after injury and their association with the severity of the injury.

Little is known of injury outcomes among non-hospitalised injured populations. This study examined the occurrence of poor outcomes 3 months after injury among the 2856 participants in the Prospective Outcomes of Injury Study, most of whom had sustained injuries considered of minor severity (by injury severity scoring) and had not received treatment at a hospital facility. The prevalence of poor outcomes was high across all health, physical functioning and social functioning domains and expectation characteristics examined, including for those participants with the 'least severe' injuries. Approximately half of the cohort reported experiencing moderate to high pain or psychological distress and reduced social participation, and three-quarters did not consider themselves recovered. Our findings demonstrate that, to obtain an accurate understanding of injury burden, injury outcome research should not focus only on those injured persons who are hospitalised.

Analysis of energy flow during playground surface impacts.

The amount of energy dissipated away from or returned to a child falling onto a surface will influence fracture risk but is not considered in current standards for playground impact-attenuating surfaces. A two-mass rheological computer simulation was used to model energy flow within the wrist and surface during hand impact with playground surfaces, and the potential of this approach to provide insights into such impacts and predict injury risk examined. Acceleration data collected on-site from typical playground surfaces and previously obtained data from children performing an exercise involving freefalling with a fully extended arm provided input. The model identified differences in energy flow properties between playground surfaces and two potentially harmful surface characteristics: more energy was absorbed by (work done on) the wrist during both impact and rebound on rubber surfaces than on bark, and rubber surfaces started to rebound (return energy to the wrist) while the upper limb was still moving downward. Energy flow analysis thus provides information on playground surface characteristics and the impact process, and has the potential to identify fracture risks, inform the development of safer impact-attenuating surfaces, and contribute to development of new energy-based arm fracture injury criteria and tests for use in conjunction with current methods.

Validity of using linked hospital and police traffic crash records to analyse motorcycle injury crash characteristics.

Linking hospital discharge and police traffic crash records has been used to provide information on causes and outcomes for hospitalised traffic crash cases. Motorcyclists are particularly vulnerable to injury in a traffic crash, but no published linkage studies have reported in detail on this road user group. The present study examined motorcycle traffic crash injury cases in New Zealand in 2000-2004 by probabilistically linking national hospital discharge records with police traffic crash reports. Injury cases had to have spent at least one night in hospital before being discharged and were defined as serious or moderate based on their International Classification of Disease Injury Severity Scores (ICISS). Despite a robust linkage process, only 46% of cases could be linked to a police record; 60% of the serious injuries and 41% of the moderate. The low linkage was most likely due to under-reporting of crashes to or by the police. While moderate injury cases were expected to be under-reported, the level of under-reporting of cases with serious threat-to-life injuries is concerning. To assess whether the linked dataset could provide valid information on the crash circumstances and injury outcomes of hospitalised motorcycle crash cases, the characteristics of the linked and unlinked hospital discharge cases were compared using chi-square tests and multivariate logistic regression. Serious injury cases were less likely to be linked if only one vehicle was involved, or the injured riders and passengers were younger than 20 years or spent less than one week in hospital. For moderate injury cases, there were also differences in linkage by injured body region and crash month. While these discrepancies need to taken into consideration when interpreting results, the linked hospital-police dataset has the potential to provide insights into motorcycle crash circumstances and outcomes not otherwise obtainable.

Physical components of soft-tissue ballistic wounding and their involvement in the generation of blood backspatter.

Gunshot backspatter comprises biological material expelled backward through bullet entry holes. Crime scene investigators analyze backspatter patterns to infer wounding circumstances. An understanding of the mechanism of backspatter generation, and the relationship between spatter patterns and bullet and tissue characteristics, would enhance the predictive value of such analysis. We examined soft-tissue ballistic wounding responses to determine the underlying components and how these might be relevant to the generation of backspatter. We identified five mechanistic components to ballistic wounding (elastic, viscous, crushing, cutting, and thermal), each related to mechanical disciplines (respectively, solid mechanics, fluid mechanics, fracture mechanics, rheology, and thermodynamics). We identified potential roles for these five components in backspatter formation and provide a scenario whereby a sequence of events incorporating these components could lead to backspatter generation and expulsion. This research provides a framework for the mathematical representation, and subsequent computational predictive modeling, of backspatter generation and pattern formation.

Tertiapin-Q removes a mechanosensitive component of muscarinic control of the sinoatrial pacemaker in the rat.

1. In an isolated right atrial preparation, an increase in right atrial pressure (RAP) produces an increase in atrial rate. This rate response is larger and occurs faster when there is background vagal or muscarinic stimulation. 2. We hypothesized that in the latter situation, an increase in RAP antagonizes the effect of muscarinic stimulation through stretch inactivation of the mechanosensitive muscarinic potassium current I(K,ACh). 3. In two groups of bath-mounted right atria isolated from male Wistar rats (control n = 12; 300 nmol/L tertiapin-Q treated (to block I(K,ACh)) n = 10), we examined the change in atrial rate when RAP was raised from 2 to 8 mmHg; oxotremorine-M (oxo-M; from 10 to 500 nmol/L) was added to incrementally activate muscarinic receptors. 4. In both control and tertiapin-Q-treated groups, oxo-M reduced atrial rate, but its effect was less ( approximately 40-50%) in the latter group (P < 0.001). In control preparations, responses to an increase in RAP became progressively larger and quicker as the concentration of oxo-M was increased, whereas in tertiapin-Q treated preparations oxo-M did not affect either the amplitude or the speed of the response (P < 0.0001 for both). 5. The results support the hypothesis that atrial stretch antagonizes muscarinic slowing by its effect on I(K,ACh). We suggest that through this mechanism, parasympathetic control of heart rate may be modulated continuously by RAP.

Energy analysis of wrist impact and surface rebound.

The mechanical interactions during impact of a falling human body onto a non-rigid surface are complex. Mechanical properties of both the impacting body and the impacted surface contribute to risk of injury. Increased understanding of these properties should provide insight into the process and how to reduce injury risk. We assessed whether modelling energy flows in the body during impact can provide useful information. As input, we used data from gymnastic tumbling mats and from children performing an exercise involving freefall onto an outstretched arm. Even basic energy transfer principles provided information not discerned by the mechanical approach traditionally used. The model identified differences between surfaces in how energy flowed through an arm and the strains imposed on the wrist during impact and rebound. Therefore, it shows promise for identifying potentially injurious human-surface interactions. Analysis of other human impact situations, and the relationship between the energy flow and injury risk, is planned.

Examination of interventions to prevent common lower-limb injuries in the New Zealand Defense Force.

The biomechanical mechanisms of lower-limb injuries in the New Zealand Defense Force were identified from the circumstances of the injuries, and injury prevention strategies that addressed these mechanisms examined for their applicability to a military setting. Many of the injuries were the result of rolling or twisting movements and ankle instability was a common causal factor. Ankle bracing and stability training were identified as the strategies that address this factor and are most likely to be effective in preventing the injuries. A successful intervention strategy must also take into account the particular requirements of the user group. Concerns with ankle bracing included ongoing costs, individual fitting requirements, and the inability to remain effective under extremes of physical activity and external conditions. Stability training was considered more appropriate than ankle bracing for the defense force. Stability training is low cost and has the ability to address the biomechanical mechanisms of several lower-limb injuries. However, it requires trialing in a military setting to assess the logistics of implementation and whether the reported sport-specific programs should be adjusted for the varied physical activities undertaken by military forces.

An approach to modeling impact energy absorption by surfaces.

The energy return characteristics of an impacted surface are important for human impacts such as a child falling onto a play surface or an athlete landing on a gymnastic mat. The amount of energy dissipated or returned to the impacting body will contribute to the surface's injury-minimizing or performance-enhancing potential. We describe a simple approach for selecting a rheological computer model to simulate a human-surface impact. The situation analyzed was of a head form impact onto gymnastic tumbling mats. The approach can be used to characterize other surfaces and impacts. The force-time-displacement characteristics of the mats were determined from laboratory drop tests. Various spring-damper models were evaluated for their ability to reproduce the experimental acceleration-time and force-displacement impact curves. An exponential spring and depth damper combination was found to best replicate the surface characteristics of the mats tested here, and to demonstrate their energy flow and exchange properties. Rheological modeling is less complex than finite element modeling but still accounted for the depth, velocity, and energy characteristics of the impacted surfaces. This approach will be useful for reproducing the characteristics of surfaces when the impacting body cannot be instrumented, and for predicting force and energy flow in nonrigid impacts.

Estimating subject-specific body segment parameters using a 3-dimensional modeller program.

The estimation of body segment properties is important in the biomechanical analysis of movement. Current subject-specific estimation methods however can be expensive and time-consuming, while other methods do not adequately take into account individual or group variability. We describe a simple procedure for estimating subject-specific geometric properties, independent of joint centres. The method requires only a small number of anthropometric measurements and digital images of the segment or subject, a 3-dimensional modeller program and simple mathematical calculations to estimate segment volumes and centroids. Assuming that the segment is of uniform density, it's mass and moment of inertia can also be derived. Future work should include generating segment density profiles for particular populations, to increase the accuracy of the method, and comparing the accuracy of the results obtained with those produced by other techniques.

Slow axonal transport of the cytosolic chaperonin CCT with Hsc73 and actin in motor neurons.

Molecular chaperones are well known for their role in facilitating the folding of nascent and newly synthesized proteins, but have other roles, including the assembly, translocation and renaturation of intracellular proteins. Axons are convenient tissues for the study of some of these other roles because they lack the capacity for significant protein synthesis. We examine the axonal transport of the cytosolic chaperonin containing T- complex polypeptide 1 (CCT) by labeling lumbar motor neurons with [35S]methionine and examining sciatic nerve proteins by 2-D gel electrophoresis and immunoblotting. All CCT subunits identifiable with specific antibodies, namely CCTalpha, CCTbeta, CCTgamma and CCTepsilon/CCTtheta; (the latter two subunits colocalized in analyses of rat nerve samples), appeared to be labeled in "slow component b" of axonal transport along with the molecular chaperone Hsc73 and actin, a major folding substrate for CCT. Our results are consistent with molecular chaperones having a post-translational role in maintaining the native form of actin during its slow transport to the axon terminal and ensuring its correct assembly into microfilaments.

Do cardiac neurons play a role in the intrinsic control of heart rate in the rat?

Three experiments were performed to see whether cardiac neurons contribute to the intrinsic control of heart rate in right atria of adult rats. The intrinsic heart rate response (IRR) was examined by raising right atrial pressure from 2 to 8 mmHg for 3 min. In isolated preparations of the right atrium, the IRR was not significantly altered by the addition of either 1 microM atropine (n =6; control +19+/- 3 min(-1) ; atropine+18+/-3 min(-1); (mean /+/-S.E.M.)) or 1 microM propranolol (n = 5; control +22+/- 4 min(-1); ; propranolol +21+/-3 min(-1); ). Tetrodotoxin (0.5 microm) had no effect on the IRR (n = 6; control +37+/-5 min(-1); tetrodotoxin 38+/-5 min(-1); ). In another experiment, 2-day-old rat pups were injected with capsaicin (50 mg kg(-1); treated) or with vehicle(control). There was no difference in the IRR of right atrial preparations taken from control and treated animals after they reached adulthood (control (n = 7) and treated (n = 8): +30+/- 4 and +32+/- 4 min(-1)). The influence of right atrial pressure on the efficacy of vagal stimulation was examined. The rate response to vagal stimulation was reduced similarly in control and treated preparations when pressure was elevated from 2 to 4 mmHg (control and treated: -34+/- 5% and -33+/- 3%). The effectiveness of the capsaicin treatment was confirmed by the depletion of substance P-immunoreactive nerve fibres in cardiac tissues. Together, these results strongly suggest that cardiac neurons are not involved in intrinsic heart rate control.