Frequent mild head injury promotes trigeminal sensitivity concomitant with microglial proliferation, astrocytosis, and increased neuropeptide levels in the trigeminal pain system.

BACKGROUND: Frequent mild head injuries or concussion along with the presence of headache may contribute to the persistence of concussion symptoms. METHODS: In this study, the acute effects of recovery between mild head injuries and the frequency of injuries on a headache behavior, trigeminal allodynia, was assessed using von Frey testing up to one week after injury, while histopathological changes in the trigeminal pain pathway were evaluated using western blot, ELISA and immunohistochemistry. RESULTS: A decreased recovery time combined with an increased mild closed head injury (CHI) frequency results in reduced trigeminal allodynia thresholds compared to controls. The repetitive CHI group with the highest injury frequency showed the greatest reduction in trigeminal thresholds along with greatest increased levels of calcitonin gene-related peptide (CGRP) in the trigeminal nucleus caudalis. Repetitive CHI resulted in astrogliosis in the central trigeminal system, increased GFAP protein levels in the sensory barrel cortex, and an increased number of microglia cells in the trigeminal nucleus caudalis. CONCLUSIONS: Headache behavior in rats is dependent on the injury frequency and recovery interval between mild head injuries. A worsening of headache behavior after repetitive mild head injuries was concomitant with increases in CGRP levels, the presence of astrocytosis, and microglia proliferation in the central trigeminal pathway. Signaling between neurons and proliferating microglia in the trigeminal pain system may contribute to the initiation of acute headache after concussion or other traumatic brain injuries

Use of High-Speed X ray and Video to Analyze Distal Radius Fracture Pathomechanics.

The purpose of this study is to investigate the failure sequence of the distal radius during a simulated fall onto an outstretched hand using cadaver forearms and high-speed X ray and video systems. This apparatus records the beginning and propagation of bony failure, ultimately resulting in distal radius or forearm fracture. The effects of 3 different wrist guard designs are investigated using this system. Serving as a proof-of-concept analysis, this study supports this imaging technique to be used in larger studies of orthopedic trauma and protective devices and specifically for distal radius fractures

Pressure Oscillation Tests of Porcine Aorta

ABSTRACT This paper addresses the problem of Traumatic Aorta Rupture (TAR) that is one of the causes of fatality in motor vehicle accidents. The mechanisms that have been suggested for TAR are speculative and inconclusive and a lot of the tests performed have not been repeatable. One of the reasons for these speculations is an incomplete understanding of the material properties of the aorta. The goal of this research is to study the response of the aorta to the oscillating pressure inputs in order to identify the structural properties of the aorta. The results of this study show that aorta stiffens as the rate of the loading increases, which is a characteristic of viscoelastic materials

Radiographic Comparison of Forearm Symmetry in Healthy Individuals and its Importance in the Diagnosis of Longitudinal Radioulnar Dissociation.

PURPOSE: Longitudinal radioulnar dissociation (LRD) is an injury often missed upon initial presentation. A recent study examined a radiographic screening test in cadavers that showed increased interosseous distance when the interosseous ligament (IOL) was divided. For this test to be clinically useful, it is necessary for uninjured forearms to have similar interosseous spaces. The purpose of this study was to determine the typical differences between right and left interosseous spaces of healthy individuals. METHODS: Anterior-posterior x-rays of bilateral forearms in maximum supination of 28 surgical residents with no history of injury were obtained. These images were uploaded into a picture archiving and communication system and then digitized. The length of the radius was measured (Xr). The maximum interosseous distance (Dmax) between the radius and ulna as well as the interosseous distance at a location 0.3 Xr from the distal radioulnar joint was measured. The right and left arm distances were compared. Also, an outlier analysis was used to evaluate forearm rotational asymmetry between right and left arms. RESULTS: The outlier analysis revealed two sets of forearm x-rays were rotationally different compared to the rest of the group due to asymmetric arm positioning; these data were excluded from the analysis. The average difference in Dmax was 1.7 mm (standard deviation [SD] 1.5) between right and left arms, and this was found at a position of 0.28 Xr on average. The difference in interosseous distance measured at a fixed location 0.3 Xr was 1.6 mm (SD 1.5). No significant difference was found between the paired right and left arms for Dmax or at 0.3 Xr. CONCLUSIONS: There does not appear to be any significant difference between the maximum interosseous distance of right and left arms in healthy individuals. Therefore, analyzing bilateral forearm x-rays may be a simple LRD screening test. CLINICAL RELEVANCE: Understanding the degree of normal variation in the forearm bone spacing might inform evaluation of abnormal forearm bone alignment resulting from LRD

Plantar Plate Reconstruction for Stage IV Plantar Plate Tear Using Flexor Tendon Tenodesis

Category: Lesser Toes Introduction/Purpose: Outcomes of the surgical treatment of dislocated lesser toes have improved significantly over the past few years due to the development of techniques to repair plantar plate tears through a dorsal incision. However, treatment of stage 4 tears with no reparable plantar plate can be challenging. The current treatment involves flexor to extensor tendon transfer, requiring multiple incisions and surgical time. An alternative approach is presented, using the same modern techniques of plantar plate repair, but reconstructing the plantar plate using a flexor tendon tenodesis to the plantar base of the proximal phalanx. Methods: Four fresh frozen cadaver foot and ankle specimens were used to determine the stability of this new technique. A simulated Lachman’s test was performed on the 2nd, 3 rd, and 4th metatarsophalangeal joints utilizing a force measurement instrument with displacement control on specimens with an intact plantar plate, an excised plantar plate, and following a flexor tenodesis reconstruction. Results: The intact plantar plate force was 9.0+2.6kN for 2 mm displacement, and following excision of the plantar plate, the force reduced to 1.3+0.4kN. The flexor tenodesis reconstruction improved the force to 6.0+1.9kN. Conclusion: Plantar plate reconstruction with a flexor tenodesis to the proximal phalanx resulted in stability equal to 53% of the intact plantar plate, for the shear displacements between 2 to 6 mm. This procedure may be an alternative treatment option in patients with Stage 4 irreparable plantar plate tears

Evaluating the Subtalar Joint in Tibiotalocalcaneal Nail

Category: Hindfoot Introduction/Purpose: In tibiotalocalcaneal nails for arthrodesis, the path of the nail through the subtalar joint has not been well documented. Ideally, the defect caused by reaming and the nail does not pass through the joint surface so that the amount of bony contact between the talus and calcaneus is maintained in order to optimize fusion. Our hypothesis is that the TTC nail does not destroy a significant amount contact area between the talus and calcaneus. However, using larger diameter nails (which are inherently stronger) will have more of an effect on the contact surface. Methods: Five cadaveric below the knee specimens were obtained. The ankle was disarticulated on each specimen. Subsequently, a guidepin was drilled from the central dome of the talus down to the calcaneus. The 11 mm reamer was then passed over the guidepin through the calcaneus to simulate retrograde reaming of a TTC nail. Then, the subtalar joint was dissected open and the articular surface was documented in comparison with the area that was reamed out. Measurements were then made, using software that calculated two dimensional surface area to determine the percentage of actual subtalar joint area that was reamed out. The mean percentage of articular area that was removed with the reamer was then calculated. Results: Among the five specimens, in the calcaneus, the mean total articular area was 599mm2±113 and the mean drilled articular area was 21mm2±16. The percentage of the calcaneal articular surface that was removed with the reamer was 3.4%±1.9. In the talus, the mean total articular area was 782mm2±130 and the mean drilled articular area was 39mm2±18. The percentage of the talar articular surface that was removed with the reamer was 5.0%±2.3. Additionally, an 11 mm reamer makes a circular surface area of 95mm2, and the statistics above indicate that a significant portion of the reamed area is nonarticular, within the calcaneal sulcus or the talar sulcus. Conclusion: In a tibiotalocalcaneal nail the subtalar joint is typically incompletely visualized, however this anatomic study demonstrates that the 11 mm reamer eliminates about 3.4% of the calcaneal articular surface and about 5% of the talar articular surface. Therefore, the majority of the articular surface is left intact, which is ideal in optimizing arthrodesis outcomes. Furthermore, this study could extrapolate the effects of a larger nail on the availability of joint surface. It could also be used to argue for cartilage stripping of the affected joint surfaces in arthrodesis preparation, because the majority of the articular surface is, in fact, left intact