Posterior Plate Research Articles

Hmmr mediates anterior neural tube closure and morphogenesis in the frog Xenopus

Development of the central nervous system requires orchestration of morphogenetic processes which drive elevation and apposition of the neural folds and their fusion into a neural tube. The newly formed tube gives rise to the brain in anterior regions and continues to develop into the spinal cord posteriorly. Conspicuous differences between the anterior and posterior neural tube become visible already during neural tube closure (NTC). Planar cell polarity (PCP)-mediated convergent extension (CE) movements are restricted to the posterior neural plate, i.e. hindbrain and spinal cord, where they propagate neural fold apposition. The lack of CE in the anterior neural plate correlates with a much slower mode of neural fold apposition anteriorly. The morphogenetic processes driving anterior NTC have not been addressed in detail. Here, we report a novel role for the breast cancer susceptibility gene and microtubule (MT) binding protein Hmmr (Hyaluronan-mediated motility receptor, RHAMM) in anterior neurulation and forebrain development in Xenopus laevis. Loss of hmmr function resulted in a lack of telencephalic hemisphere separation, arising from defective roof plate formation, which in turn was caused by impaired neural tissue narrowing. hmmr regulated polarization of neural cells, a function which was dependent on the MT binding domains. hmmr cooperated with the core PCP component vangl2 in regulating cell polarity and neural morphogenesis. Disrupted cell polarization and elongation in hmmr and vangl2 morphants prevented radial intercalation (RI), a cell behavior essential for neural morphogenesis. Our results pinpoint a novel role of hmmr in anterior neural development and support the notion that RI is a major driving force for anterior neurulation and forebrain morphogenesis.

Curative effect analysis of 15 cases of cervical intra-and extra-spinal tumors by microsurgical resection

Objective: To explore the curative effect of microsurgical treatment of cervical intra- and extra-spinal tumors. Methods: The clinical data of 15 patients with cervical intra-and extra-spinal tumors in Department of Neurosurgery, the First Affiliated Hospital of Bengbu Medical College from January 2013 to February 2017 were retrospectively analyzed. According to Shaw's tumor stage: 6 cases in stage Ⅰ, 5 cases in stage Ⅱ, 3 cases in stage Ⅲ, and 1 case in stage Ⅳ. About the surgical methods: 9 cases were treated via posterior median semi-laminectomy approach, of which were internal fixation in 2 cases, and via posterior median approach spinous process and vertebral plate complex orthotopic replantation to spinal canal plasty in 3 cases, other 3 cases were operated via anterior cervical approach, including internal fixation in 1 case. After the surgery, vertebral canal MRI was adopted to evaluate the tumor, and CT three-dimensional reconstruction or X-ray of the spine was used for assessing the stability of spinal column, and Frankel grading standard was employed to evaluate the recovery of spinal cord function. Results: The tumors were totally resected in the first stage with the help of a microscope. Histological types of the tumors included schwannoma in 14 cases, gangliocytoma in 1 case. There was no leakage of cerebrospinal fluid and infection of incisional wound after operations. After the surgery, Frankel grading standard was adopted to assess the recovery of the spinal cord function, and the results showed grade D in 4 patients and grade E in 11 patients. All patients were followed-up for 1 to 24 months with an average of 13 months without tumor recurrence and spinal instability. Conclusion: Appropriate surgical approach should be selected to treat the cervical intra- and extra-spinal tumors, totally resection of the tumor could be achieved under the microscope, and the corresponding vertebral reconstruction and spinal fixation should be used to maintain spinal stability if necessary.

Comparing Different Surgical Techniques for Addressing the Posterior Malleolus in Supination External Rotation Ankle Fractures and the Need for Syndesmotic Screw Fixation

Trimalleolar ankle fractures are unstable injuries with possible syndesmotic disruption. Recent data have described inherent morbidity associated with screw fixation of the syndesmosis, including the potential for malreduction, hardware irritation, and post-traumatic arthritis. The posterior malleolus is an important soft tissue attachment for the posterior inferior syndesmosis ligament. We hypothesized that fixation of a sizable posterior malleolar (PM) fracture in supination external rotation type IV (SER IV) ankle fractures would act to stabilize the syndesmosis and minimize or eliminate the need for trans-syndesmotic fixation. A retrospective review of trimalleolar ankle fractures surgically treated from October 2006 to April of 2011 was performed. A total of 143 trimalleolar ankle fractures were identified, and 97 were classified as SER IV. Of the 97 patients, 74 (76.3%) had a sizable PM fragment. Syndesmotic fixation was required in 7 of 34 (20%) and 27 of 40 (68%), respectively, when the PM was fixed versus not fixed (p = .0002). When the PM was indirectly reduced using an anterior to posterior screw, 7 of 15 patients (46.7%) required syndesmotic fixation compared with none of 19 patients when the PM fragment was fixated with direct posterior lateral plate fixation (p = .0012). Fixation of the PM fracture in SER IV ankle fractures can restore syndesmotic stability and, thus, lower the rate of syndesmotic fixation. We found that fixation of a sizable PM fragment in SER IV or equivalent injuries through posterolateral plating can eliminate the need for syndesmotic screw fixation.

Plate Osteosynthesis of Proximal Ulna Fractures—A Biomechanical Micromotion Analysis

Double plating has been promoted, in recent years, as an alternative treatment method for proximal ulna fractures. This study aimed to compare the biomechanical properties of double-plate osteosynthesis with posterior plate fixation using a novel investigational design utilizing a 3-dimensional camera system to analyze fracture micromotion. Fourteen fresh-frozen specimens were available for this study. Mayo type IIA fractures of the olecranon were created and internal fixation was performed with either an angular stable posterior plate or angular stable double plates. Fracture micromotion was evaluated by means of digital image correlation with a 3-dimensional camera system before and after dynamic cyclic loading from 15° to 90° of elbow flexion with a pulling force of 25 N to 80 N. Micromotion of fragments was less pronounced in double-plate osteosynthesis when compared with single plates before and after cyclic loading. However, overall results were similar. Two of the single plates failed during cyclic loading but there were no failures in the double plates. This biomechanical analysis shows that single and double plating results in comparable stability of fixation. Although the double-plating technique tends to provide more stable fixation, relevant differences were not observed. Double plating potentially represents an efficient option for fixation of proximal ulna fractures. It could decrease the risk of soft tissue complications owing to their low profile and the superior soft tissue coverage.

An ultrastructural study of the surface and attachment structures of Paradiplozoon homoion (Bychowsky & Nagibina, 1959) (Monogenea: Diplozoidae)

BackgroundSpecies of Diplozoon Palombi, 1949 (Monogenea: Diplozoidae) are blood-feeding ectoparasites mainly parasitising the gills of cyprinid fishes. Although these parasites have been the subject of numerous taxonomic, phylogenetic and ecological studies, the ultrastructure of the surface and haptor attachment structures remains almost unknown. In this study, we used transmission electron microscopy to examine the ultrastructure of attachment clamps and neodermal surface of Paradiplozoon homoion (Bychowsky & Nagibina, 1959), family Diplozoidae Palombi, 1949, thereby broadening our knowledge of platyhelminth biology.ResultsThe hindbody surface of P. homoion is distinctly ridged, each ridge being supported by several muscle fibers and equipped with scales on the surface plasma membrane. Such structures have not been recorded previously in species of the family Diplozoidae. Comparisons of the surface structure of different body parts revealed slight differences in the thickness and number of organelles. Each of the clamps has a flattened bowl-like structure composed of sclerites, movable skeletal-like structures that are anchored by robust, radially oriented muscle bundles. The base of the posterior median plate sclerites is equipped with glandular cells possessing secretory vesicles.ConclusionThis study brings detailed ultrastructural data for the surface and haptoral attachment clamps of P. homoion and provides new insights into the ultrastructure of Diplozoidae. Glandular cells at the base of the attachment clamps responsible for sclerite development in diplozoid species were observed for the first time. Our findings support the hypothesis that the structure of particular neodermal compartments is similar within the Platyhelminthes. On the other hand, the diplozoid glandular system and the mechanism of sclerite development clearly merits further attention.

A new Early Devonian (Emsian) arthrodire from the Northwest Territories, Canada, and its significance for paleogeographic reconstruction

An heterostiid arthrodire, Herasmius dayi sp. nov., is described from upper Lower Devonian marine deposits of the Bear Rock Formation along the Anderson River, Northwest Territories, Canada. New elements described for the genus for the first time include the suborbital, submarginal (also new for the family Heterostiidae), the lateral shoulder girdle with posterior lateral, anterior dorso-lateral, and posterior dorso-lateral plates and possible infragnathal plate. We present a new reconstruction of the cranial region of Herasmius, previously known only from supposedly freshwater – shallow marine deposits of roughly the same age in the Wood Bay Group of Spitsbergen. The late Early Devonian fishes that are common to the Arctic region of northwestern Canada and the island of Spitsbergen in the Svalbard archipelago of Norway, the porolepiform Heimenia and the arthrodire Herasmius described here, demonstrate the existence of a barrier-free paleogeographic connection between those continental blocks by the late Early Devonian. Comparison of the entire Anderson River vertebrate fauna with other boreal faunas of similar age indicates additional paleogeographic connections north of and around the Old Red Sandstone Continent to the Baltic region, central Europe, and even to the New Siberian Islands and South China, in contrast to most current published paleogeographical reconstructions.

Efficacy evaluation of limited internal fixation with posterior titanium plates for unstable atlas fractures

Objective To determine the clinical efficacy of limited internal fixation with posterior titanium plates for unstable atlas fractures. Methods A retrospective case series analysis was performed for 29 patients with unstable atlas fractures immobilized using the posterior titanium plate from January 2011 to November 2014. There were 22 males and seven females, with a mean age of 41.5 years (range, 17-68 years). Ten patients were diagnosed with 1/2 ring Jefferson fractures, 12 anterior 1/2 Jefferson fractures and seven patients posterior 3/4 Jefferson fractures. Frankel neurological performance scale was grade E in all patients. Operation time, amount of bleeding during operation and postoperative complications were recorded. X-ray and CT were performed to identify the fusion, internal fixation location and atlantoaxial stability. Visual Analogue Scale (VAS) for craniocervical pain and cervical range of motion were evaluated. Results Mean duration of procedure was (86.6±7.8)min (range, 68-122 min) and mean blood loss was (120.0±25.3)ml (range, 90-400 ml). No vascular and neurologic complications were noted. All patients were followed up for (22.5±18.0)months (range, 12-32 months). CT scans confirmed bony union in all patients 6 months after operation. No plate-related complications, implant lessening and implant breakage occurred during the follow-up. Postoperative VAS[(1.9±1.1)points] was significantly lower than that before operation [(7.2±1.4)points] (P<0.05). At the last follow-up, the ranges of cervical flexion-extension [(81.3±22.2)°] androtation [(152.4±38.7)°] were close to the normal range. Conclusion Limited internal fixation with posterior titanium plates is a safe and effective surgical method that contributes to good reduction and maximal preservation of cervical physiological motion. Key words: Atlanto-axial joint; Joint instability; Fracture fixation, internal

Plate fixation for Letenneur type I Hoffa fracture: a biomechanical study

BackgroundA coronal fracture of the posterior femoral condyle, also known as a Hoffa fracture, is an unusual injury, and there are only a handful of case reports or series exploring it. The optimal fixation method of these intraarticular fractures remains controversial; improper or unstable fixation usually lead to an unsatisfactory prognosis. The use of posterior–anterior or reversed lag screw fixation is still a popular method. Additional buttress plating is also recommended for fixation of these difficult fractures. The purpose of this study was to compare the mechanical strength of four different fixation patterns for this uncommon fracture. Material and methodsSixteen sawbone simulated models of Letenneur type I Hoffa fractures were created with one of four fixation patterns: two screws implanted in the anterior–posterior (AP) direction or posterior–anterior (PA) direction; one screw in the PA direction with a plate implanted in the posterior position of the distal femoral condyle or with a plate in the lateral position. Biomechanical testing was performed to determine the post-fixation axial stiffness, the maximum load to failure and the fragment vertical displacement for each of the four constructs. ResultsThe plate fixation patterns whether implanted in the posterior or lateral position were shown to provide higher overall axial stiffness and load to failure, and less vertical displacement than the other two patterns of pure screw fixation. Among these constructs, the lateral plate fixation was found to provide the highest stiffness and load to failure and the least displacement for the posterior condylar fragments, followed by the posterior plate fixation. The lowest overall stiffness and load to failure and the largest vertical displacement were found in the construct with the AP direction placed screws. ConclusionIt was concluded that the lateral position implanted plate is biomechanically the strongest fixation method for Letenneur type I Hoffa fractures. However, this plate fixation is not recommended for all cases. The choice of internal fixation pattern depends on the surgeons.

Robot-assisted approach to 'W'-configuration urinary diversion: a step-by-step technique.

To describe a detailed step-by-step approach of our technique for robot-assisted intracorporeal 'W'-configuration orthotopic ileal neobladder. Five patients underwent robot-assisted radical cystectomy (RARC), extended pelvic lymph node dissection and intracorporeal neobladder (ICNB). ICNB was divided into six key steps to facilitate and enable a detailed analysis and auditing of the technique. No conversion to open surgery was required. Timing for each step was noted. All patients had at least 3 months of follow-up. The mean age was 57 years. The mean overall console and diversion times were 357 and 193 min, respectively. None of the patients had any evidence of residual disease after RARC. Four of the five patients had complications; three developed fevers due to urinary tract infections (one required readmission), and one developed myocardial infarction and required coronary angiography and stenting. Looking at the timing for the individual steps, bowel detubularisation and construction of the posterior plate were consistently the longest among the key steps (average 46 min, 13% of the overall operative time), followed by uretero-ileal anastomosis (37 min, 10%), neobladder-urethral anastomosis (23 min, 6%), and identification and fixation of the bowel (26 min, 7%). We described our step-by-step technique and initial perioperative outcomes of our first five ICNBs with 'W' configuration.

Comparison of cannulated lag screw versus buttress plate fixation for posterior malleolar fractures

Objective To compare the clinical outcomes of percutaneous cannulated lag screws versus posterior buttress plate in the fixation for posterior malleolar fractures. Methods We reviewed the 167 patients who had been treated between January 2010 and December 2014 for ankle fracture involving larger than 25% of the articular surface of the posterior malleolus. They received posterior malleolus fixation with percutaneous cannulated lag screws or with a buttress plate. In the cannulated screw group (84 patients), there were 47 males and 37 females, aged from 23 to 72 years (average, 49.7±9.1 years), and 39 cases of type B and 45 ones of type C according to the Dennis-Webber classification. In the buttress plate group (83 patients), there were 38 males and 45 females, aged from 31 to 69 years (average, 52.3±8.3 years), and 45 cases of type B and 38 ones of type C according to the Dennis-Webber classification. At 6 and 12 months postoperation and the final follow-up, the ankle motion was evaluated using American Orthopaedic Foot and Ankle Society (AOFAS) score and range of motion (ROM). Results The average operation time for the cannulated screw group was significantly shorter than for the buttress plate group (Z=-9.145, P 0.05); the AOFAS scores at the final follow-up for all the patients were significantly different from those at 6 and 12 months postoperation (P 0.05). Conclusions As there are no significant differences between the percutaneous cannulated lag screws and posterior buttress plate in AOFAS score and ROM of the ankle after fixation for posterior malleolar fractures, the 2 fixation methods can both achieve good clinical outcomes. Fixation with cannulated lag screws has advantages of indirect reduction and minimal invasion but also a disadvantage of uncertain quality of reduction; fixation with buttress plates has an advantage of anatomical reduction under direct vision but also shortcomings of relatively large invasion and high cost. Key words: Ankle; Fractures fixation, internal; Bone nails; Bone plates; Posterior malleolus

Ultrastructure and molecular phylogenetic position of a new marine sand-dwelling dinoflagellate from British Columbia, Canada: Pseudadenoides polypyrenoides sp. nov. (Dinophyceae)

ABSTRACT Two monospecific genera of marine benthic dinoflagellates, Adenoides and Pseudadenoides, have unusual thecal tabulation patterns (lack of cingular plates in the former; and no precingular plates and a complete posterior intercalary plate series in the latter) and are thus difficult to place within a phylogenetic framework. Although both genera share morphological similarities, they have not formed sister taxa in previous molecular phylogenetic analyses. We discovered and characterized a new species of Pseudadenoides, P. polypyrenoides sp. nov., at both the ultrastructural and molecular phylogenetic levels. Molecular phylogenetic analyses of SSU and LSU rDNA sequences demonstrated a close relationship between P. polypyrenoides sp. nov. and Pseudadenoides kofoidii, and Adenoides and Pseudadenoides formed sister taxa in phylogenetic trees inferred from LSU rDNA sequences. Comparisons of morphological traits, such as the apical pore complex (APC), demonstrated similarities between Adenoides, Pseudadenoides and several planktonic genera (e.g. Heterocapsa, Azadinium and Amphidoma). Molecular phylogenetic analyses of SSU and LSU rDNA sequences also demonstrated an undescribed species within Adenoides.

Clinical analysis of cervical posterior internal fixation titanium plate and silk suspension internal fixation cervical spondylosis

Objective: To evaluate the clinical effect and imaging evaluation of cervical spine myelopathy treated with Centerpiece. Methods: A retrospective study of 60 patients underwent posterior cervical spine surgery because of cervical myelopathy in Spinal Department of Peking University People's Hospital from July 2011 to January 2013.According to the different fixation methods, all patients were divided into cervical posterior open-door Centerpiece fixation group (group A) and cervical posterior open-door silk suspension fixation group (group B). There were 40 patients in group A, including 25 males and 15 females, mean age (59.7±11.9) years old, average course of disease before surgery (53.6±61.5) months, average follow-up time (28.5±3.1) months after operation.There were 20 patients in group B, including 15 males and 5 females, mean age (58.3±9.6) years old, average course of disease before surgery (50.4±14.9) months, average follow-up time (28.3±1.9) months after operation.The operation time, intraoperative blood loss, postoperative drainage, preoperative and postoperative Japanese Orthopaedic Association(JOA) score, the neck disability index(NDI) score, visual analog scale (VAS) score, postoperative axial pain, C(5) nerve root palsy, postoperative "re-closing" and other related complications were observed.Imaging assessment projects include: before and after surgery of cervical curvature, range of motion(ROM), spinal anteroposterior diameter, spinal canal expansion rate, the whole spinal cord backward shift distance and area of the spinal canal and the opening angle. Results: There was no significant difference in general data between the two groups (P>0.05). Group A the average operation time was(117.7±23.4)min, the average amount of operative bleeding was (152.0±122.7) ml, and the postoperative drainage volume was (268.7±222.1) ml.The average operation time of group B was (141.7±23.9) min, the average amount of operative bleeding was (166.7±42.5) ml, and the postoperative drainage volume of group B was (255.3±47.0) ml.There was no significant difference between the two groups in the amount of operative bleeding and postoperative drainage volume (both P>0.05), the operation time between the two groups was statistically significant (P<0.05). At the end of the follow-up, the JOA score, NDI score, and VAS score were significantly improved (P<0.05) in both group A and group B and there was no significant difference between the two groups (P>0.05). C(5) nerve root paralysis was not occurred in both two groups after operation.There were 1 case of axial pain in the group A and 7 cases in the group B and there were significant differences between the two groups (P<0.05). The group A was not found "re-closing" during the follow-up and 12 patients of group B found to be "re-closing" phenomenon, there were statistically different between the two groups (P<0.05). Comparison of preoperative and postoperative, there were no significant differences in cervical curvature and ROM in both groups (P>0.05). Butthe spinal canal diameter and the vertebral canal area were statistically different after surgery (P<0.05). There was no statistical difference between the two groups of cervical curvature and ROM (P>0.05). There was no statistical difference between the two groups of spinal canal diameter, spinal canal area and spinal canal diameter enlargement rate(P>0.05). There was no statistical difference between the two groups of the whole spinal cord backward shift distance(P>0.05). There were significant differences between the two groups at the angle of the open door (P<0.05). Conclusion: Centerpiece cervical posterior titanium plate can achieve good clinical efficacy in the treatment of multi segmental spinal cervical spondylosis.

Designation and Validation of a Posterior Anatomical Plate for the Anterior Column of the Acetabulum.

BackgroundSurgical treatment of acetabular fractures is one of the greatest challenges for orthopedic surgeons. Fixation of most displaced fractures requires extensive exposure, which may lead to complications, including blood loss, neural or vascular injury, postoperative infection, wound healing problems, and heterotopic bone formation.Material/MethodsThis study was conducted to certify an anatomic plate with an anterior column lag screw guiding device to repair the posterior acetabulum. Complete pelvic spiral computed tomography (CT) scan data were collected from 56 patients. The posterior column of the acetabulum was simulated with a lag screw. The guiding device for the plate was designed by measuring the position of the screw point and the direction and maximum diameter of the screw.ResultsThe distance from the screw point to the apex of the greater sciatic notch was farther in women than in men. The distance from the screw point to the ischial spine was also farther in women than in men. The θ angle (front inclination angle) of the screw was lower in women than in men. The ϕ angle (camber screw angle) was greater in women than in men. The success rate when using the guided device was significantly higher than when using traditional pedicle screws.ConclusionsThe guided device was very useful for improving placement success and accuracy rates of the acetabular posterior anatomical anterior column plate using antegrade lag screws, and for reducing surgical risk and injury.

New information on Titanichthys (Placodermi, Arthrodira) from the Cleveland Shale (Upper Devonian) of Ohio, USA

AbstractThe placoderm Titanichthys from the Late Devonian (Famennian) is based on incomplete and fragmentary specimens that have hindered understanding of its overall anatomy and phylogenetic relationships. A new, nearly complete, articulated specimen from the Upper Devonian Cleveland Shale provides new information about the previously undescribed rostral, postmarginal, postsuborbital, submarginal, posterior superognathal plates, and the nasal capsule. A revised diagnosis is provided for the genus. Three new diagnostic characters are identified, including a transversely elliptical rostral plate that does not contact adjacent plates, a reduced posterior superognathal, and a median dorsal plate that inserts into the posterior dorsal lateral plate. The first comprehensive phylogenetic analysis of Titanichthys indicates that the genus is a basal aspinothoracid arthrodire closely related to the enigmatic taxa Bungartius and Tafilalichthys.

Finite element analysis of the three different posterior malleolus fixation strategies in relation to different fracture sizes

PurposeAppropriate fixation method for the posterior malleolar fractures (PMF) according to the fracture size is still not clear. Aim of this study was to evaluate the outcomes of the different fixation methods used for fixation of PMF by finite element analysis (FEA) and to compare the effect of fixation constructs on the size of the fracture computationally. Materials and methodsThree dimensional model of the tibia was reconstructed from computed tomography (CT) images. PMF of 30%, 40% and 50% fragment sizes were simulated through computational processing. Two antero-posterior (AP) lag screws, two postero-anterior (PA) lag screws and posterior buttress plate were analysed for three different fracture volumes. The simulated loads of 350N and 700N were applied to the proximal tibial end. Models were fixed distally in all degrees of freedom. ResultsIn single limb standing condition, the posterior plate group produced the lowest relative displacement (RD) among all the groups (0.01, 0.03 and 0.06mm). Further nodal analysis of the highest RD fracture group showed a higher mean displacement of 4.77mm and 4.23mm in AP and PA lag screws model (p=0.000). The amounts of stress subjected to these implants, 134.36MPa and 140.75MPa were also significantly lower (p=0.000). There was a negative correlation (p=0.021) between implant stress and the displacement which signifies a less stable fixation using AP and PA lag screws. ConclusionProgressively increasing fracture size demands more stable fixation construct because RD increases significantly. Posterior buttress plate produces superior stability and lowest RD in PMF models irrespective of the fragment size.

Terminal chop: New technique for full thickness nuclear segmentation in mature hard cataract.

We describe an efficient technique, “Terminal Chop,” for full thickness nuclear segmentation in mature hard cataracts. Terminal chop utilizes the principle of secondary rock breakage system with stress concentration to break these hard nuclei. In this technique consonant to drag picks, a specially designed chopper “Terminator” is used to initiate a unique dispersive mechanical force to create a full thickness nuclear crack (crack formation) at the weakest soft and thin equator, which automatically traverses through the center and to the equator on the other side. Lateral separation of both the instruments placed at the equator, propagates the initial full thickness nuclear crack (crack propagation), breaking the entire nucleus into two complete pieces including the posterior plate. The direction of splitting follows the cleavage plane in a more direct manner, thus requiring least fracture force, least manipulation and stress, much lower than compressive stress, causing minimal trauma, and highly satisfactory postoperative results.

The posterior neural plate in axolotl gives rise to neural tube or turns anteriorly to form somites of the tail and posterior trunk

Classical grafting experiments in the Mexican axolotl had shown that the posterior neural plate of the neurula is no specified neuroectoderm but gives rise to somites of the tail and posterior trunk. The bipotentiality of this region with neuromesodermal progenitor cell populations was revealed more recently also in zebrafish, chick, and mouse. We reinvestigated the potency of the posterior plate in axolotl using grafts from transgenic embryos, immunohistochemistry, and in situ hybridization. The posterior plate is brachyury-positive except for its more anterior parts which express sox2. Between anterior and posterior regions of the posterior plate a small domain with sox2+ and bra+ cells exists. Lineage analysis of grafted GFP-labeled posterior plate tissue revealed that posterior GFP+ cells move from dorsal to ventral, form the posterior wall, turn anterior bilaterally, and join the gastrulated paraxial presomitic mesoderm. More anterior sox2+/GFP+ cells, however, are integrated into the developing spinal cord. Tail notochord is formed from axial mesoderm involuted already during gastrulation. Thus the posterior neural plate is a postgastrula source of paraxial mesoderm, which performs an anterior turn, a novel morphogenetic movement. More anterior plate cells, in contrast, do not turn anteriorly but become specified to form tail spinal cord.

Non-surgical treatment of anterior open bite using miniscrew implants with posterior bite plate

PurposeThis study describes the quantitative relations between the intrusion of posterior teeth and changes in overbite and lower anterior facial height after treatment of open bite patients with miniscrew implants and posterior bite plates. The study also assessed changes in masticatory muscular activity that may result from the use of bite plate. Materials and methodsFifteen patients (mean age±SD=20.6±4) with anterior open bite were treated with two miniscrew implants in each side of posterior maxillary dentoalveolar bone and fixed posterior bite plate. Changes in upper posterior dental height (UPDH), overbite (OB) and lower anterior facial height (LAFH) were measured using cephalographs. Activities of masseter and anterior temporalis muscles during clenching and swallowing were assessed before treatment, after placement of bite plate and after removal of the plate. Linear regressions were used to investigate the relationships between morphologic parameters, and paired t-test was used to test changes in muscular activity. ResultsLinear relationships were found between posterior teeth intrusion and the increase of overbite and reduction in LAFH. Each 1mm intrusion improves the open bite by 1mm and the LAFH by 0.7mm. The muscular activity decreased after placement of the plate but recovered immediately after its removal. ConclusionOutcomes after treatment with miniscrew implants and bite plate can be predicted by the amount of intrusion in posterior teeth. The bite plate seems not to affect the muscular activity after removal of the plate.

Spontaneous Middle Fossa Encephalocele

A 48-year old man presented with a unilateral right hearing loss of four months’ duration. A right middle ear effusion was noted on physical examination. Endoscopic examination of the nasopharynx was unremarkable. Due to the duration of the symptoms, myringotomy with ventilation tube insertion was offered as a treatment option. Upon myringotomy, clear pulsatile liquid flowed out of the incision. More than 5 cc of liquid was collected which continued to flow out despite active suctioning. Due to the realization that the liquid most likely represented cerebrospinal fluid, insertion of a ventilation tube was not performed. The ear canal was packed with sterile cotton, and the patient was given a short course of acetazolamide to decrease CSF production. Upon further questioning, the patient did not have any prior head trauma. The patient then underwent both computerized tomographic (CT) imaging and magnetic resonance imaging (MRI) of the temporal bone to look specifically for evidence of a dehiscence in the middle fossa plate (tegmen) or posterior fossa plate, as well as the presence of a meningoencephalocele.&#x0D; &#x0D; Computerized tomographic imaging of the temporal bone in the axial plane showed a soft tissue density completely occupying the air-containing spaces of the middle ear, epitypanum and mastoid air cells, without any evidence of bony erosion of the scutum, the ossicles, or the bony septations of the mastoid air cells. T2-weighted magnetic resonance imaging in the axial plane showed that the soft tissue densities in the middle ear, the epitympanum and mastoid air cells had a naturally high signal intensity characteristic of fluid. (Figure 1).&#x0D; On coronal CT imaging, a dehiscence of the middle fossa plate (tegmen) was noted lateral to the superior semicircular canal. Magnetic resonance imaging in the same plane revealed a soft tissue density in the region of the dehiscence that was contiguous with, and isointense with the temporal lobe. This soft tissue density appeared to originate from the temporal lobe, and extended downwards into the upper portion of the mastoid antrum. No enhancement was noted on gadolinium-enhanced T1-weighted imaging (Figure 2). With these imaging findings, a middle fossa encephalocele was considered. Exploratory mastoidectomy confirmed the diagnosis, and the patient subsequently underwent a transmastoid repair of the tegmen and dural dehiscence using both temporalis fascia and mastoid cortical bone, after the herniated brain tissue was amputated.&#x0D; A middle fossa encephalocele is a condition of the temporal bone that may arise as a complication of chronic otitis media, temporal bone fractures, or after surgery involving the temporal bone. Although rare, spontaneous middle fossa encephaloceles may also occur.1,2 One must maintain a high degree of clinical suspicion for this condition in an adult patient presenting with a unilateral middle ear effusion or watery otorrhea in the absence of an identifiable cause of otologic disease2 or nasopharyngeal pathology. It should definitely be highly considered if profuse, persistent clear otorrhea is encountered during a myringotomy for what may initially appear to be a chronic middle ear effusion. Surgical treatment of the encephalocele and repair of the skull base defect is generally recommended, as life threatening complications such as meningitis, brain abscess and temporal lobe seizures have been known to occur.2

Posterior Fossa Spontaneous Cerebrospinal Fluid Leaks.

Describe the diagnosis and management of spontaneous lateral skull base cerebrospinal fluid (CSF) leaks that originate from the posterior fossa. Retrospective case review. Tertiary university hospital. Adult patients from 2005 to 2015 who underwent surgical repair of a spontaneous lateral skull base CSF leak with intraoperative confirmation of a posterior fossa leak source. Surgical repair. CSF leak resolution. Five patients had CSF leaks from the posterior fossa. The mean age at presentation was 54 years old (range, 19-79), the mean body mass index (BMI) was 32.6 (standard deviation [SD], 8.4), and the mean follow-up length was 34.6 months (SD, 19.4). Presentations did not differ from CSF leaks through middle fossa defects, including three patients with a history of meningitis and all patients with clear otorrhea following tympanostomy tube placement. All patients had resolution of the leak after surgical repair, but two patients required revision surgery for persistent leaks and one patient had a postoperative infection. Surgical approaches included one middle fossa, two transmastoid, one combined middle fossa/transmastoid, and one transcanal. Radiographic studies suggested a posterior fossa source in all cases but findings were often subtle. Posterior fossa CSF leaks represent a rare subset of spontaneous lateral skull base leaks. Diligent radiographic review and intraoperative assessment of the posterior fossa plate are crucial. The size and location of the defect dictates the optimal surgical approach. Surgeons should consider a posterior fossa source in failed repairs or when the initial surgery did not fully evaluate the posterior fossa plate.