Projectile penetration into ballistic gelatin Swain, M.V.; Kieser, D.C.; Shah, S. ...
Journal of the mechanical behavior of biomedical materials,
January 2014, 2014-Jan, 2014-01-00, 20140101, Letnik:
29
Journal Article
Recenzirano
Ballistic gelatin is frequently used as a model for soft biological tissues that experience projectile impact. In this paper we investigate the response of a number of gelatin materials to the ...penetration of spherical steel projectiles (7 to 11mm diameter) with a range of lower impacting velocities (<120m/s). The results of sphere penetration depth versus projectile velocity are found to be linear for all systems above a certain threshold velocity required for initiating penetration. The data for a specific material impacted with different diameter spheres were able to be condensed to a single curve when the penetration depth was normalised by the projectile diameter. When the results are compared with a number of predictive relationships available in the literature, it is found that over the range of projectiles and compositions used, the results fit a simple relationship that takes into account the projectile diameter, the threshold velocity for penetration into the gelatin and a value of the shear modulus of the gelatin estimated from the threshold velocity for penetration. The normalised depth is found to fit the elastic Froude number when this is modified to allow for a threshold impact velocity. The normalised penetration data are found to best fit this modified elastic Froude number with a slope of 1/2 instead of 1/3 as suggested by Akers and Belmonte (2006). Possible explanations for this difference are discussed.
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The intra-articular administration of tranexamic acid (TXA) has been shown to be effective in reducing blood loss in unicompartmental knee arthroplasty and anterior cruciate reconstruction. The ...effects on human articular cartilage, however, remains unknown. Our aim, in this study, was to investigate any detrimental effect of TXA on chondrocytes, and to establish if there was a safe dose for its use in clinical practice. The hypothesis was that TXA would cause a dose-dependent damage to human articular cartilage.
The cellular morphology, adhesion, metabolic activity, and viability of human chondrocytes when increasing the concentration (0 mg/ml to 40 mg/ml) and length of exposure to TXA (0 to 12 hours) were analyzed in a 2D model. This was then repeated, excluding cellular adhesion, in a 3D model and confirmed in viable samples of articular cartilage.
Increasing concentrations above 20 mg/ml resulted in atypical morphology, reduced cellular adhesion and metabolic activity associated with increased chondrocyte death. However, the cell matrix was not affected by the concentration of TXA or the length of exposure, and offered cellular protection for concentrations below 20 mg/ml.
These results show that when in vitro chondrocytes are exposed to higher concentrations of TXA, such as that expected following recommended intra-articular administration, cytotoxicity is observed. This effect is dose-dependent, such that a tissue concentration of 10 mg/ml to 20 mg/ml could be expected to be safe. Cite this article: Bone Joint J 2018;100-B:404-12.
Both the plantaris tendon and the peroneus tertius tendon are used as auto- and allogenous graft materials to reconstruct the ankle ligament complex. However, it is unclear to what extent these graft ...materials resemble the load-deformation behavior of the ankle ligaments. A total of 34 human ankle ligaments and 35 tendons were assessed mechanically deploying a quasi-static tensile testing setup. Tendons were significantly stiffer (median elastic moduli: plantaris tendon = 465.7 MPa, peroneus tertius tendon = 338.5 MPa, medial ligament = 61.4 MPa, lateral ligament = 49.3 MPa; p ≤ 0.035), but more distensible (median strain at maximum force: plantaris tendon = 15.1%, peroneus tertius tendon = 15.3%, medial ligament = 9.3%, lateral ligament = 9.6%; p ≤ 0.008) and mechanically tougher (median ultimate tensile strength: plantaris tendon = 51.0 MPa, peroneus tertius tendon = 40.5 MPa, medial ligament = 4.1 MPa, lateral ligament = 3.5 MPa; p ≤ 0.033) when compared to medial and lateral ankle ligaments. The lateral ligaments of the right ankle were significantly tougher compared to the left side (p = 0.015). The elastic modulus of the medial ligament (r = 0.489, p = 0.045) and the peroneus tertius tendon (r = 0.517, p = 0.014) yielded an age-dependent increase. Both tendons seem biomechanically suitable graft materials to replace the medial and lateral ankle ligaments during physiological loading. The age-dependent increase in tissue elastic properties of the medial vs. lateral ankle ligaments, and differences in ultimate tensile strength between the lateral ligaments left vs. right, may reflect the complex asymmetric loading behavior of both ankle ligaments.
Purpose
To understand the typical presentation, risk factors, location and size, treatment, neurological recovery and survival of spontaneous spinal epidural haematomas (SSEH) in children.
Methods
A ...systematic review of the English literature from 1 January 1960 to 1 March 2018 was performed on children aged 18 years and younger. Individual patient data were extracted and collated. Outcome measures were mode of presentation, risk factors, initial neurological findings, initial presumed diagnosis, diagnostic investigations, site and size of the SSEH, treatment, neurological recovery and survival.
Results
Thirty-one publications and 36 patients were reviewed. All age groups were affected. 83% of patients did not have a known risk factor. Back pain was reported in 61% and neurological dysfunction in 97% of patients, although not all articles defined these parameters. Initially 28% of patients were suspected of having an alternative diagnosis. All patients had an MRI and/or CT scan confirming the diagnosis. The cervical-thoracic region was most commonly affected, and the average haematoma size extended across 6.3 vertebral levels. Surgical decompression was performed in 72% of patients. Neurological function improved in 83% of patients. Two patients died as a consequence of their SSEH.
Conclusions
SSEHs affect all paediatric age groups and typically present with neurological dysfunction and/or back pain. The initial diagnosis is incorrect in up to 28% of cases, but cross-sectional spinal imaging is diagnostic. Most SSEHs are located in the cervico-thoracic region and affect multiple spinal levels. The treatment depends on whether the patient has a bleeding disorder and their neurological status.
Graphical abstract
These slides can be retrieved under Electronic Supplementary Material.
A review of ballistic gelatin calibration standards has highlighted that data used from studies with different calibrations methods may not be able to be compared. Calibration of ballistic gelatin ...did not occur until the mid-1980s when Fackler recognised the deficiencies of uncalibrated gelatin. He determined that the calibration standard should be 85±5 mm of ball bearing penetration for a 180 m/s impact velocity. This study looks to improve on and optimise current ballistic gelatin calibration standards METHODS: Nine 0.177 cal (4.5 mm) spheres were fired using a Daisy Powerline air rifle at velocities between 134 m/s and 224 m/s at 25 gelatin blocks (n=225). Velocities were measured using an
Model 36 Chronograph with three Model 57 screens. Depth of penetration (DoP) was measured from the entry surface to the back end of the sphere via a Mitutoyo Absolute vernier calliper.
The R-squared regression model showed that all batches had a close fit to the regression line. Using the R-squared regression model, the equation y=0.584x - 20.02 (where x is the velocity) returned a DoP of 84.918 mm for a 180 m/s impact and therefore needed minimal adjustment to align with Fackler's 85 mm DoP. The equation can be adjusted to y=0.584x - 20.12 to return a DoP of 85 mm for 180 m/s.
We propose that the calibration standard of ballistic gelatin with 4.5 mm spheres is DoP=0.584x - 20.12 where DoP is the depth of penetration (mm) and x is the impact velocity (m/s), The measured DoP should be within 5% of the calculated DoP.
While tissue simulants are considered best practice for ballistic evaluations, there is an ongoing debate about the use of tissue simulant and their relevance and there are calls to improve models by ...making them more anatomically relevant by the introduction of bony structures and organs. Therefore; the aim of this study was to try and determine if sponges and/or ballistic gelatin may be a suitable proxy to porcine lungs using 5.56x45mm (MK262-MOD1). Four sample groups consisting of 10% ballistic gelatin blocks, lungs embedded in gelatin, kitchen sponges and car sponge in gelatin were evaluated. Analysis included determining the onset of yaw, time from impact to the onset of yaw, temporary and permanent cavity characteristics and energy deposition. The results indicated that the kitchen sponge and car sponge may be a suitable proxy to porcine lungs, however there were significant differences between the lung model and plain gelatin blocks and additional work should be carried out to investigate the suitability of sponges as a proxy to porcine lungs further.
Purpose
Objectives in scoliosis corrective surgery include restoration of normal sagittal and coronal parameters to achieve patient satisfaction. HRQLs improvements remain limited after corrective ...surgery. The aim of this study was to evaluate the HRQL subclass variability specific to the sagittal and coronal correction in adult scoliosis surgery.
Methods
This multi-centre prospective analysis of consecutive adult spinal deformity (ASD) patients, from five European centres, only included multilevel instrumentation for scoliosis. d-(delta) values for each parameter represented pre to post-operative changes. Parameters included demographics, baseline, 1- and 2-year. HRQL outcomes (Oswestry disability index (ODI), Scoliosis Research Society (SRS)-22 and Short Form (SF36)), sagittal correction including relative spinopelvic alignment (dRSA) and coronal correction including major Cobb (dCobb) angles.
Results
A total of 353 patients reached 1-year and 2-year follow up. All HRQL total scores significantly improved postoperatively, including ODI, SRS-22 and SF36. HRQL subclasses which displayed persistent improvements correlated to dRSA included sex-life, self-image, fatigue, vitality, social functioning. The only HRQL subclass improvement that correlated with dCobb was self-image.
Conclusion
Adult scoliosis surgery improves overall HRQL, having a minimal effect on each variable. Importantly, greater coronal deformity correction affects only greater self-image scores, whereas with greater sagittal correction there are many greater HRQL sub-class impacts. Correction and restoration of coronal balance is one of the surgical goals in adult scoliosis but the degree to which Cobb angle is corrected, apart from self-image, does not correlate with gains in sub-classes of HRQL. These results need to be taken into account when planning surgery.
Objective. To determine the effect on the need for transfusion when intravenous tranexamic acid (TXA) is administered intraoperatively in patients undergoing total hip arthroplasty (THA). Method. A ...prospective, double blinded, randomised control trial of 88 patients undergoing THA was randomly allocated to receive 1 g of intravenous TXA or normal saline on induction of anaesthesia. All patients received spinal anaesthesia. The primary outcome measure was transfusion rate, and the secondary outcomes were intraoperative blood loss, haemoglobin levels, length of hospital stay, functional scores, and thromboembolic complications. Results. 19.0% of patients given TXA required a blood transfusion, compared with 20.5% given placebo (p=0.87). Secondary outcomes included mean intraoperative blood loss, which was 536.5 ml in the TXA group and 469.8 ml in the placebo group (p=0.276). Day 1 haemoglobin levels were 108.9 g/l in the TXA group versus 104.3 g/l in the placebo group (p=0.114). Day 4 haemoglobin levels were 105.0 g/l and 99.8 g/l, respectively (p=0.130). The mean length of stay in those who received TXA was 4.3days, compared with 4.8days in those given placebo (p=0.20). The Oxford Hip Score showed a mean improvement over a 1-year period of 25.9 points in those who received TXA, compared with 26.7 points in those who received placebo (p=0.679). There were two treatment emergent adverse events: a pulmonary embolism (TXA) and a myocardial infarction (placebo). Conclusions. 1 g IV TXA administered on induction did not significantly reduce the need for blood transfusion, postoperative blood loss, functional scores, or the length of stay in patients undergoing THA. This trial is registered with ACTRN12610001065088.
Background
In the absence of cadaveric tissues, forensic simulation, trauma modelling, and cranial surgical training necessitates a surrogate for the human calvaria. This study investigates the ...validity of
Bos taurus
scapulae as a proxy for human frontal bones by comparing the laminar and cancellous bone thickness, as well as the bone mineral density (BMD) of cadaveric frontal bones and adult
Bos taurus
scapulae.
Results
This study aimed to validate the bovine scapulae as a valid proxy for forensic experiments, which benefit researchers and investigators who need to recreate forensic scenarios where synthetic proxies are found unsuitable due to their non-viscoelastic nature and cadaveric human models are unavailable due to ethical restrictions. Our results identified different total thicknesses of the relative bones, but non-different cortical measurements between human frontal bone and bovine scapulae. The bone mineral density is similar between both groups.
Conclusion
This study has found
Bos taurus
scapulae to be a suitable proxy for human frontal bones as it has a similar morphology with regard to thickness and structure as well as a comparable density. However, there is a significant difference between the cancellous bone, and therefore, the overall thickness.
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