An evaluation of occupant dynamics during moderate-to-high speed side impacts

The present study examined trends in occupant dynamics during side impact testing in vehicle models over the past decade. "Moderate-to-high" speed side impacts (delta-V ≥15 km/h) were analyzed. The Insurance Institute for Highway Safety (IIHS) side impact crash data was examined (N = 126). The test procedure involved a moving deformable barrier (MDB) impacting the sides of stationary vehicles at 50.0 km/h. Instrumented 5th-percentile female SID IIs dummies were positioned in the driver and left rear passenger seats. Occupant head, neck, shoulder, torso, spine, and pelvis/femur responses (times histories, peaks, and time-to-peak values) were evaluated and compared to injury assessment reference values (IARVs). The effects of delta-V, vehicle model year, vehicle body type, and occupant seating position on dynamic responses were examined. The vehicle lateral delta-Vs ranged from 15.9 to 34.5 km/h. The MY2018-2020 demonstrated lower peak dynamics than MY2010-2013, for the driver head acceleration (53.7 ± 11.3g vs 46.4 ± 11.6g), shoulder lateral forces (1.7 ± 0.7 kN vs 1.5 ± 0.2 kN), average rib deflection (29.8 ± 8.3 mm vs 28.4 ± 6.2 mm), spine accelerations at T4 (51.4 ± 23.4g vs 39.6 ± 5.9g) and T12 (56.3 ± 18.5g vs 45.2 ± 9.6g), iliac forces (1.9 ± 1.0 kN vs 1.2 ± 0.9 kN), and acetabular forces (1.9 ± 0.8 kN vs 1.3 ± 0.5 kN). The driver indicated statistically higher dynamic responses than the left rear passenger. Higher wheelbase vehicles generally showed lower occupant loading than the smaller vehicles. In conclusion, a reduction in occupant loading and risks for injury was observed in vehicle models over the past decade. This provides further insight into injury mechanisms, occupant dynamics simulations, and seat/restraint design.

Analysis of change in gait in the ovine stifle: normal, injured, and anterior cruciate ligament reconstructed

Background

Many patients who undergo anterior cruciate ligament (ACL) reconstructive surgery develop post-traumatic osteoarthritis (PTOA). ACL reconstructive surgery may not fully restore pre-injury joint biomechanics, thereby resulting in further joint damage and contributing to the development of PTOA. In an ovine model of idealized ACL reconstruction (ACL-R), it has been shown that signs of PTOA develop within surgical joints by 20 weeks post-surgery. The aim of the present study was to investigate whether altered kinematics contribute to early PTOA development within ACL-R joints of the ovine injury model by comparing the gait of these surgical animals to the gait of a stable normal control group, and an unstable injury group in which the ACL and medial collateral ligament (MCL) had been transected.

Methods

Fifteen skeletally mature female sheep were allocated evenly into 3 treatment groups: normal control, ACL-R, and ACL/MCL Tx (each group n = 5). Each animal’s gait was recorded at baseline, 4 weeks post injury, and 20 weeks post injury. Principal component analysis (PCA) was used to identify the kinematic patterns that may be discriminant between treatment groups. Results from previous studies were referenced to present the amount of gross PTOA-like changes that occurred in the joints.

Results

ACL-R and ACL/MCL transected (Tx) animals developed a similar amount of early PTOA-like changes within the surgical joints, but differed significantly in the amount of kinematic change present at 20 weeks post-surgery. We showed that the stifle joint kinematics of ACL/MCL Tx differed significantly from those of CTRL and the majority of ACL-R animals, while no significant differences in joint kinematic changes were found between ACL-R and CTRL animals.

Conclusions

These results suggest that the early PTOA-like changes reported in the ACL-R model cannot be attributed exclusively to post-surgical kinematic changes, and therefore biologic components in the post-injury environment must be contributing significantly to PTOA development.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-017-1576-3) contains supplementary material, which is available to authorized users.

Use of pre-clinical surgically induced models to understand biomechanical and biological consequences of PTOA development

Post-traumatic osteoarthritis (PTOA) development is often observed following traumatic knee injuries involving key stabilising structures such as the cruciate ligaments or the menisci. Both biomechanical and biological alterations that follow knee injuries have been implicated in PTOA development, although it has not been possible to differentiate clearly between the two causal factors. This review critically examines the outcomes from pre-clinical lapine and ovine injury models arising in the authors' laboratories and differing in severity of PTOA development and progression. Specifically, we focus on how varying severity of knee injuries influence the subsequent alterations in kinematics, kinetics, and biological outcomes. The immediate impact of injury on the lubrication capacity of the joint is examined in the context of its influence on biomechanical alterations, thus linking the biological changes to abnormal kinematics, leading to a focus on the potential areas for interventions to inhibit or prevent development of the disease. We believe that PTOA results from altered cartilage surface interactions where biological and biomechanical factors intersect, and mitigating acute joint inflammation may be critical to prolonging PTOA development. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:454-465, 2017.

Ligament and meniscus loading in the ovine stifle joint during normal gait

BACKGROUND

The ovine stifle joint is an ideal preclinical model to study knee joint biomechanics. Knowledge of the ovine ligamentous and meniscal loading during normal gait is currently limited.

METHODS

The in vivo kinematics of the ovine stifle joint (N=4) were measured during "normal" gait using a highly accurate instrumented spatial linkage (ISL, 0.3±0.2mm). These motions were reproduced in vitro using a unique robotic testing platform and the loads carried by the anterior/posterior cruciate ligaments (ACL/PCL), medial/lateral collateral ligaments (MCL/LCL), and medial/lateral menisci (MM/LM) during gait were determined.

RESULTS

Considerable inter-subject variability in tissue loads was observed. The load in the ACL was near zero at hoof-strike (0% gait) and reached a peak (100 to 300N) during early-stance (~10% gait). The PCL reached a peak load (200 to 500N) just after hoof-strike (~5% gait) and was mostly unloaded throughout the remainder of stance. Load in the MCL was substantially lower than the cruciate ligaments, reaching a maximum of 50 to 100N near the beginning of stance. The LCL carried a negligible amount of load through the entire gait cycle. There was also a major contribution of the MM and LM to load transfer from the femur to the tibia during normal gait. The total meniscal load reached a maximum average between 350 and 550N during gait.

CONCLUSION

Knowledge of joint function during normal motion is essential for understanding normal and pathologic joint states. The considerable variability in the magnitudes and patterns of tissue loads among animals simulates clinical variability in humans.

LEVEL OF EVIDENCE

III.

Cartilage boundary lubrication of ovine synovial fluid following anterior cruciate ligament transection: a longitudinal study

OBJECTIVE

To assess ovine synovial fluid (oSF) from different post-injury time points for (1) proteoglycan-4 (PRG4) and hyaluronan (HA) concentration, (2) HA molecular weight (MW) distribution, (3) cartilage boundary lubrication function, and (4) lubricant composition-function relationships. The association between cartilage boundary lubrication and gross cartilage changes after injury was also examined.

METHODS

oSF was collected 2, 4, 10, and 20 weeks post anterior cruciate ligament (ACL) transection in five skeletally mature sheep. PRG4 and HA concentrations were measured using sandwich enzyme-linked immunosorbent assay, and HA MW distribution by agarose gel electrophoresis. Cartilage boundary lubrication of oSF was assessed using a cartilage-cartilage friction test. Gross damage to articular cartilage was also quantified at 20 weeks using modified Drez scoring protocol.

RESULTS

Early (2-4 weeks) after ACL injury, PRG4 concentrations were significantly higher (P = 0.045, P = 0.037), and HA concentrations were substantially lower (P = 0.005, P = 0.005) compared to 20 weeks. The HA MW distribution also shifted towards lower ranges in the early post-injury stage. The kinetic friction coefficients were significantly higher 2-4 weeks post injury (P = 0.008 and P = 0.049) compared to 20 weeks. Poor cartilage boundary lubricating ability early after injury was associated with cartilage damage at 20 weeks.

CONCLUSION

Altered composition and diminished boundary lubrication of oSF early after ACL transection may pre-dispose the articular cartilage to degenerative changes and initiate osteoarthritis (OA). These observations also provide potential motivation for biotherapeutic interventions at earlier time points post injury.

Increased meniscal loading after anterior cruciate ligament transection in vivo: a longitudinal study in sheep

INTRODUCTION

Meniscal injury has been well documented as a frequent consequence of both acute and chronic ACL deficiency. The purpose of this study was to evaluate the effect of ACL deficiency on meniscal loads in vivo and determine how these loads would change over time after ACL injury.

METHODS

The in vivo kinematics of the stifle joint of five sheep were measured during normal gait, as well as 4 and 20 weeks after ACL transection. A unique robotic testing platform was then programmed to reproduce all the previously recorded kinematics and the loads carried by medial and lateral menisci during gait were estimated.

RESULTS

The results demonstrated a significant increase in both medial and lateral meniscal loads 20 weeks following ACL transection, mainly during mid-stance phase of gait (p = 0.007 and p = 0.003, respectively), with interesting inter-subject variability. A moderate correlation (R(2) ≥ 0.5) between in situ meniscal loads and anterior tibial translations was also detected over time after injury, increased translations post injury generally corresponded to larger meniscal loads.

CONCLUSION

The dramatic increase in meniscal loads long term post ACL transection probably explains the meniscal changes or injuries reported clinically in many chronic ACL-deficient knees.

Decreased posterior cruciate and altered collateral ligament loading following ACL transection: a longitudinal study in the ovine model

Although ACL deficiency is shown to lead to joint degeneration, few quantitative data are reported on its effect on soft tissue structures surrounding the knee joint, specifically, the posterior cruciate and collateral ligaments. The kinematics of the stifle joint of sheep (N = 5) were measured during "normal" gait, as well as 4 and 20 weeks after ACL transection. These motions were reproduced using a unique robotic manipulator and the loads borne by PCL, MCL, and LCL during gait were determined. Our results demonstrated a significant decrease in mean PCL loads 20 weeks post-ACL injury, at hoof-strike (0% of gait, p = 0.034), hoof-off (66% of gait, p = 0.006), peak-swing (85% of gait, p = 0.026), and extension-before-hoof-strike (95% of gait, p = 0.028). Mean MCL loads did not significantly increase following ACL transection, maybe due to large between-animal variation. Finally, mean LCL loads indicated a significant decrease (p < 0.047) at 20 weeks across the entire gait cycle. From a clinical perspective, the load redistributions observed in cruciate and collateral ligaments following ACL injury indicate that these tissues can carry/adapt to the altered mechanical environment of the joint. The considerable variability in the magnitudes of change following ACL injury among animals also simulates clinical variability in humans after trauma.

A methodology for prediction of acute hypotensive episodes in ICU via a risk scoring model including analysis of ST-segment variations

The aim of this study is to detect Acute Hypotensive Episodes (AHE) and Mean Arterial Pressure Dropping Regimes (MAPDRs) using ECG signal and Arterial Blood Pressure waveforms. To meet this end, the QRS complexes and end-systolic end-diastolic pulses are first extracted using two innovative Modified Hilbert Transform-Based algorithms namely as ECGMHT and BPMHT. A new smoothing algorithm is next developed based on piecewise polynomial fitting to smooth the fast fluctuations observed in RR-tachogram, systolic blood pressure (SBP) and diastolic blood pressure (DBP) trends. Afterwards, in order to consider the mutual influence of parameters on the evaluation of shock probability, a Sugeno Adaptive Network-based Fuzzy Inference System-ANFIS is trained using Hasdai et al. (J Am Coll Cardiol, 35: 136–143, 2000) parameters as input, with appropriate membership functions for each parameter. Using this network, it will be possible to incorporate the possible mutual influences between risk parameters such as heart rate, SBP, DBP, ST-segment episodes, age, gender, weight and some miscellaneous factors to the calculation of shock occurrence probability. In the next step, the proposed algorithm is applied to 15 subjects of the MIMIC II Database and AHE and MAPDRs (MAP ≤ 60 mmHg with a period of 30 min or more) are identified. As a result of this study, for a sequence of MAPDRs as long as 20 min or more, there will exist a consequent high peak with the duration of 3–4 min in the corresponding probability of cardiogenic shock diagram.

Parallel processing of ECG and blood pressure waveforms for detection of acute hypotensive episodes: a simulation study using a risk scoring model

The aim of this study is to detect acute hypotensive episodes (AHE) and mean arterial pressure dropping regimes (MAPDRs) using electrocardiographic (ECG) signals and arterial blood pressure waveforms. To meet this end, the QRS complexes and end-systolic end-diastolic pulses are first extracted using two innovative modified Hilbert transform-based algorithms, namely ECGMHT and BPMHT. The resulting systolic and diastolic blood pressure pulses are then used to calculate the MAP trend. A new smoothing algorithm is developed, next based on piecewise polynomial fitting (PPF) to smooth the fast fluctuations observed in RR-tachogram and MAP trends. PPF algorithm operates by sequentially fitting N number of polynomials to the original signal and calculating the corresponding coefficients using the best linear unbiased estimation approach. In the next step, the proposed algorithm is applied to 15 subjects of the MIMIC II Database and AHE and MAPDRs (MAP ≤ 60 mmHg with a period of 30 min or more) are identified. As a result of this study, MAPDR is realised as a specific marker of cardiogenic shock, in that for a sequence of MAPDRs as long as 20 min or more, there will exist a consequent high peak with a duration of 3-4 min in the corresponding probability of cardiogenic shock diagram.

Characterization of the location and extent of myocardial infarction using heart vector analysis

An innovative method was proposed on the basis of vectorcardiography to characterize the location and extent of moderate to large, relatively compact infarcts using ECG evidence. It is assumed that heart vector is proportional to relevant active depolarization area(s). The normal VCG was then used to examine our ideas based on the information of location, amplitude, and direction of heart vector at any instant that is included in it. The model-based comparison of cases under study and relevant normal VCGs gives region and extent of myocardial infarction. Three criteria were finally defined to evaluate the presented method based on Physionet database. EPD, which is the percentage discrepancy between the extent of the infarct as estimated from our proposed method and as determined from the gold standard. SO, which was defined as the overlap between the sets of infarct segments as estimated and as determined from the gold standard. And CED, which is the distance between the centroid (geometrical center) of the infarct as estimated from our method and as determined from the gold standard. Finally, we gained the values of EPD equal to 32, SO equal to 0.933 and CED equal to 1. The presented method is not applicable in cases of hypertrophy, Bundle Branch Block (BBB) and arrhythmia which can be a plan for future work.