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Cardiac Biomechanics
Published in Joseph D. Bronzino, Donald R. Peterson, Biomedical Engineering Fundamentals, 2019
Andrew D. McCulloch and Roy C. P. Kerckhof
e most basic mechanical parameters of the cardiac pump are blood pressure and volume ow rate, especially in the major pumping chambers, the ventricles. From the point of view of wall mechanics, the ventricular pressure is the most important boundary condition. Schematic representations of the time courses of pressure and volume in the le ventricle are shown in Figure 15.4. Ventricular lling immediately following mitral valve opening (MVO) is initially rapid because the ventricle produces a diastolic suction as the relaxing myocardium recoils elastically from its compressed systolic conguration below the resting chamber volume. e later slow phase of ventricular lling (diastasis) is followed nally by atrial contraction. e deceleration of the inowing blood reverses the pressure gradient across the mitral valve leaets and causes them to close (MVC). Valve closure may not, however, be completely passive because the atrial side of the mitral valve leaets, which, unlike the pulmonic and aortic valves, are cardiac in embryological origin, have muscle [35] and nerve cells, and are electrically coupled to atrial conduction [36].
Potential of Polyhydroxyalkanoates for Bone Defect Repair
Published in Tatiana G. Volova, Yuri S. Vinnik, Ekaterina I. Shishatskaya, Nadejda M. Markelova, Gennady E. Zaikov, Natural-Based Polymers for Biomedical Applications, 2017
Tatiana G. Volova, Yuri S. Vinnik, Ekaterina I. Shishatskaya, Nadejda M. Markelova, Gennady E. Zaikov
X-ray examination of the rabbits’ limbs after surgical intervention showed that in the group with P3HB 3D porous implants, at Day 30, in the middle third of the femoral bone, there was a 2.5-mm round cavity, which was considerably smaller than the initial defect and the defect observed at Day 30 in Group 2 (Colapol) (Figure 6.10). The cavity had well-defined boundaries, without a sclerotic rim. The periosteum was not changed, and there was no periosteal reaction. In Group 2, with Colapol used to fill the defect, the survey radiograph taken at Day 30 showed a 3-mm round cavity in the middle third of the femoral bone. The cavity had well-defined boundaries, without a sclerotic rim. In 2 animals of Group 3, the survey radiograph taken at Day 30 showed a pathologic fracture in the middle third of the femoral bone (where the bone tissue defect had been created), with bone fragments displaced transversely and angularly, with diastasis of the terminal 3–4 mm. The radiograph showed periosteal reaction of bone fragments, local foci of bone tissue destruction, and osteolysis. At Day 90, partial consolidation was observed. The formation of the false joint at the fracture site, chronic periosteal inflammation, and local foci of bone tissue destruction were observed in 2 animals.
Biomechanics of spinal trauma
Published in Youlian Hong, Roger Bartlett, Routledge Handbook of Biomechanics and Human Movement Science, 2008
Brian D. Stemper, Narayan Yoganandan
Although uncommon, these injuries are attributed to the bending of the neck in the coronal plane and side impact loading in vehicular environments is an example (Allen et al., 1982). Thoracic and lumbar columns are even less involved. Because the cervical spine demonstrates coupling, these injuries are associated with bending in the axial plane (Sherk et al., 1989; Yoganandan et al., 2007). Because the weight of the head always acts on the neck and its center of gravity/mass is eccentrically located with respect to the cervical column, compression and flexion are also associated. Odontoid fractures stemming from the combined lateral bending and compression mechanism have been identified in modern motor vehicle environments and supported by laboratory studies (Mouradian et al., 1978; Yoganandan et al., 1986, 2005). Although rare, unilateral facet trauma in the form of pillar fractures can occur because of ipsilateral compression; diastasis of the contralateral facet joint is also possible.
Abusive head trauma in India: imaging raises the curtain
Published in International Journal of Injury Control and Safety Promotion, 2022
Hima Pendharkar, Shumyla Jabeen, Nupur Pruthi, K. V. L. N Narasinga Rao, Dhaval Shukla, Nitish Kamble, Kavita V. Jangam, John Vijay Sagar Kommu, Thennarasu Kandavel, Senthil Amudhan
Imaging revealed SDH in 42/48 (87.5%), and SDE in 5/48 (10.41%) cases; 1/48 (2.08%) case had only hypoxia. Convexity SDH was noted in 36/42 (85.7%) cases, it was bilateral in 11/36 (30.5%) cases and unilateral in 25/36 (69.4%) cases - where it was on the right in 14/25 (56%) and on the left in 11/25 (44%) cases. SDH was noted in the posterior interhemispheric fissure (PIHF) in 35/42 (83.3%) cases, tentorial in 24/42 (57.1%) cases, in the posterior fossa in 16/42 (38.1%) cases and in the anterior interhemispheric fissure (AIHF) in 11/42 (26.2%) cases. Hypoxia underlying SDH was seen in 13/42 (31%) cases, hypoxia underlying SDH and contralateral to SDH was noted in 9/42 (21.4%) cases of which 6/9 (67%) cases showed white cerebellum sign; isolated infarcts were noted in 7/48 (14.5%) cases. SAH was noted in 14/48 (29.16%) cases, parenchymal hematoma in 9/48 (18.75%) cases and IVH in 2/48 (4.2%) cases. A skeletal survey and chest x-ray were available for 7/48 (14.5%) and 29/48 (60%) cases respectively. Skull fractures were noted in 9/48 (18.75%) cases and sutural diastasis in 3/48 (6.25%) cases. One of the forty eight cases had C2 fracture (2.1%), and 1/48 (2.1%) had C4–C5 dislocation, one child had an epidural hematoma (2.1%). Among other injuries, rib fractures were noted in 2/48 (4.2%) patients, 1/48 (2.1%) cases had a tibial fracture, and 1/48 (2.1%) case had a radial fracture. The imaging features are summarized in Table 2. Findings of fundus evaluation were available in 10/48 (20.83%) of our cases and have been summarized in Table 3.
Hybrid triad provides fracture plane stability in a computational model of a Pauwels Type III hip fracture
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2020
M. Cordeiro, S. Caskey, C. Frank, S. Martin, A. Srivastava, T. Atkinson
In general, the diastasis (opening at the superior margin of the fracture) decreased from low to high angle fracture simulations, which is consistent with how the load is oriented relative to the fracture plane. As the loading vector and fracture plane become more parallel, the shear load across the fracture increases, thus increasing likelihood of shear displacement. This is different from the lower angle which resulted in a levering open of the fracture plane, thereby creating diastasis. The largest magnitude for diastasis was seen in the SHS which was ∼2.3 times the diastasis seen in the Hybrid and Triad constructs for the high angle fracture. In the mal-reduced models the Triad had similar diastasis to the Hybrid construct (both providing a tension band effect to the superior margin of the fracture). Compression is important in direct bone healing (Perren 1979) and diastasis at the superior aspect of the fracture represents loss of compression under load. Based on this and the shear displacement results, the SHS alone provides poor stability.
Mechanisms of cervical spine injury and coupling response with initial head rotated posture – implications for AIS coding
Published in Traffic Injury Prevention, 2022
Narayan Yoganandan, Jamie Baisden, John Humm, Vicky Varghese
The AIS scores for all injured specimens were at a severity level of 2. The severity level was downgraded from the previous 3 level (65022.3) in the AIS 1990-1998 update presumably due to the stable nature of the bony pathology and changes in patient treatment modalities that have changed over time. The issue of the diastasis is, however, not addressed in the recent AIS 2015 version. While this may not always result in immediate instability and require surgical intervention, it may be necessary to revisit this issue in the future. Upper cervical fractures with diastasis and or transverse atlantal ligament involvement are factors for AIS consideration.