Reconstruction Plate Research Articles

Actinomycosis osteomyelitis of the mandible in a 71-year-old patient: A Case Report

We herein present the treatment of an actinomycosis osteomyelitis case. A 71-year-old female with a dental history of multiple tooth extractions two years prior who subsequently developed chronic osteomyelitis. Previous treatment included 10 sessions of hyperbaric oxygen and pentoxifylline tocopherol protocol as well as debridement of the lesion that had resulted in a subsequent midline pathological fracture of the mandible. The fracture was treated by intra-bony wiring. The clinical extra-oral presentation was that of severe pain, recurrent swelling of the submandibular areas bilaterally and draining fistulae. Our treatment included antibiotic therapy: guided by Microscopy Culture and Sensitivity and a segmental mandibulectomy with the placement of a reconstruction plate. The outcome of the therapeutic management was successful. Histopathology results confirmed chronic osteomyelitis with bacterial colonies in keeping with actinomycosis. At the six-week post-operative appointment, the patient was healing well.

Short-term effectiveness of reconstruction plate internal fixation via improved Stoppa approach combined with iliac fossa approach and Kocher-Langenbeck approach for complex acetabular fractures

To investigate the short-term effectiveness of reconstruction plate internal fixation via improved Stoppa approach combined with iliac fossa approach and Kocher-Langenbeck approach for complex acetabular fractures. Between January 2015 and January 2020, 30 patients with complex acetabular fractures were treated with reconstruction plate internal fixation via improved Stoppa approach combined with iliac fossa approach and Kocher-Langenbeck approach. There were 20 males and 10 females with an average age of 52.1 years (range, 25-71 years). The cause of injury included traffic accident in 17 cases and falling from height in 13 cases. Among them, 14 cases were left acetabular fractures and 16 cases were right acetabular fractures. According to Letournel classification, there were 16 cases of double column fractures, 2 cases of transverse fracture with posterior wall fracture, 4 cases of anterior column and posterior hemi-transverse fractures, 8 cases of T-shaped fracture. The displacement distance of fracture ranged from 6 to 30 mm (mean, 11.6 mm). The time from injury to operation was 6-14 days (mean, 8.7 days). The operation time was 2.0-4.5 hours (mean, 3.0 hours). The intraoperative blood loss was 200-800 mL (mean, 450.0 mL). All patients were treated with autologous blood transfusion during operation. All incisions healed by first intention after operation, and no infection occurred. All patients were followed up 12-15 months (mean, 13.4 months). The drainage tube was removed at 2-3 days after operation. After extubation, X-ray film and three-dimensional CT were performed to recheck the fracture reduction. According to Matta score system, 20 cases were excellent, 5 were good, and 5 were poor, the excellent and good rate was 83.3%. All fractures healed with the healing time of 16-25 weeks (mean, 17.7 weeks). According to Merle d'Aubigne-Postel score system, the hip function at 1 year after operation was rated as excellent in 18 cases, good in 6 cases, and fair in 6 cases, and the excellent and good rate was 80.0%. Two cases suffered from sciatic nerve injury due to traction during operation, 7 cases had heterotopic ossification, 2 cases had traumatic hip arthritis, and no other complications occurred. For complex acetabular fractures, the reconstruction plate internal fixation via improved Stoppa approach combined with iliac fossa approach and Kocher-Langenbeck approach can obtain good short-term effectiveness with good reduction and hip joint function, and less complications.

Endoscopic Reconstruction of the Anterior Skull Base Following Tumor Resection: Application of a Novel Bioabsorbable Plate.

Endoscopic repair of skull base defects is required following resection of intracranial pathology via the endoscopic endonasal approach (EEA). Many closure techniques have been described, but choosing between techniques remains controversial. We report outcomes of 560 EEA procedures of skull base reconstruction performed on 508 patients over a 15-year-period. Halfway through this period, we adopted the use of a rigid, bioabsorbable extrasellar plate for reconstruction, enabling a comparison between this technique and those used previously. All patients undergoing EEA from 2005 to 2019 at our institution were retrospectively reviewed. Demographic information, surgical pathology, tumor dimensions and radiographic features, reconstructive technique, and patient-related outcomes were collected and analyzed with univariate and multivariate statistical modeling. Five-hundred sixty procedures were performed on 508 patients. The series complication rate was 8.2%. Overall, cerebrospinal fluid (CSF) leak rate was 5.0% but varied significantly across closure techniques (p < 0.001). Critically, the CSF leak rate in the 272 cases prior to our 2013 adoption of the Resorb-X Plate (RXP) was 8.5%, whereas leak rate in the subsequent 288 cases was 1.7%. RXP was protective against CSF leak (p=0.001), whereas gross total resection (GTR) correlated with increased leak rate (p=0.001). Patient BMI was significantly associated with risk of leak (p=0.047). Other variables did not impact leak risk. Reconstructive technique, extent of resection, and patient BMI significantly contributed to CSF leak rate. GTR was associated with increased leak risk while the RXP was protective. The bioabsorbable RXP is an effective option for rigid skull base repair with comparatively few complications. 3 Laryngoscope, 133:1092-1098, 2023.

Long-term global sea-level change due to dynamic topography since 410 Ma

Sedimentary studies at continental boundary show that the global sea level has hundreds of meters of change since the late Paleozoic. Long-term global sea-level change is closely related to the mantle convection. The deflection of the ocean basins caused by dynamic topography can change the container volume of the basin, thus inducing global sea-level change. However, the influence of dynamic topography on the global sea-level change during supercontinent cycles is not well understood. Based on dynamic topography from mantle convection models and past seafloor age from plate reconstructions, I studied the influence of dynamic topography on global sea-level change since 410 Ma. Model results show that the present-day dynamic topography contributes to ∼120 m of positive global sea level. Dynamic topography raises the sea level during the dispersal, assembly, and transition phases, and drops the sea level during period of supercontinent stability. Global sea-level change caused by the seafloor age distribution is the main factor that controls the long-term global sea-level change. Different methods to define the ocean basin have only a small influence on global sea level change due to the combined effects of seafloor age and dynamic topography. The combined effects of dynamic topography and seafloor age uplift the sea-level during Pangea dispersal and assembly phases, and decrease sea-level during stability and the transition phases.

Анализ применения оригинальных металлоконструкций для фиксации переднего отдела тазового кольца

Introduction Stabilization of chronic injuries of the pelvic ring with standard methods may result in plate breach, destabilization of the implant and the need for repeated operations. Therefore, it has become necessary to use special tactical approaches in surgical treatment of chronic injuries for fixing traumatic foci and searching for adapted implant designs for such cases. Thus, an original plate has been developed. Purpose To study the features of fixation of chronic injuries of the pelvic ring using an original plate in comparison with the standard approach. Materials and methods We conducted a retrospective analysis of the surgical treatment performed using the developed plate (Group 2) and a group of patients who underwent fixation of the anterior pelvic ring with two reconstruction plates (Group 1). Results In group 1, four patients (16.7 %) had failed osteosynthesis within two weeks to two months after the operation. In group 2, thirty patients underwent surgical treatment using the developed design, and destabilization of the metal construct was detected only in 2 patients (6.6 %). In one case, migration of plate screws was detected after 3 years during routine X-ray study while the patient was not bothered by pain and did not feel any instability. Discussion Analyzing the positive and negative aspects of the methods used, we made a choice in favor of internal plating. Due to cases of destabilization of fixation using one or two plates, an original metal structure was developed and applied to strengthen fixation. Conclusion Changing the standard approaches to the treatment of chronic injuries (after 3 weeks since injury) of the anterior pelvic ring enables to create conditions for stable fixation, using the original monolithic plate, despite the rigidity of the pelvic ring in chronic injuries.

Current Evidence for the Management of Edentulous Atrophic Mandible Fractures: A PRISMA-SWiM Guided Review.

PRISMA-SWiM guided systematic review. 1. Provide consistent evidence regarding the management of atrophic mandible fractures; 2. To search, evaluate and validate existing guidelines if any for the management; 3. Provide evidence regarding specific management of condylar fractures in the atrophic mandible; 4. To address the clinical applicability of bone grafts. A systematic review was conducted using the PRISMA-SWiM protocol. PROSPERO ID: CRD42021235111. Studies with adequate data on outcome, treatment methods were selected. Isolated case reports, case series, and non-human studies were excluded. Quality assessment was done using Newcastle -Ottawa scale. The level of evidence was assessed using Oxford Level of Evidence. Mandibular body was the most common type of fracture. Self falls and RTA were the most common etiologies. Condylar fracture was most commonly managed conservatively with ORIF employed in few studies. For the mandible compression and non-compression osteosynthesis were used. Bone grafts were used in cases with segmental defects or cases requiring augmentation. There is lack of proper evidence to definitely conclude any single treatment modality. However, the consensus is towards ORIF. Reconstruction plates are preferred by many authors. However, unilateral fractures may be managed by miniplates. Bilateral fractures require more rigid fixations. Open reduction and internal fixation of condylar fracture is indicated in cases with displacement or low-level fractures.

Discovery of Ultra‐Depleted Melt Inclusion in Late Cretaceous Intracontinental Basaltic Andesites in South China: Implications for Recycling of Lower Oceanic Crust

AbstractIncompatible element ultra‐depleted melt (UDM) has occasionally been found as olivine‐hosted inclusion in plume‐related oceanic island basalts and mid‐oceanic ridge basalts and is genetically linked with the involvement of lower oceanic gabbroic crust. However, it has rarely been reported in intracontinental magmatism, and the contribution of such a recycled component to the origin of intracontinental magmas remains unclear. Here, we first report UDM inclusions hosted in olivine from Late Cretaceous intracontinental basaltic andesites in South China. These UDM inclusions are characterized by low SiO2 (46.4–47.9 wt%) and extremely high Al2O3 (18.47–21.79 wt%) contents, positive Sr‐Eu anomalies, and low 207Pb/206Pb and 208Pb/206Pb ratios. Such geochemical features resemble those of high‐pressure melts derived from young lower oceanic gabbro. These results, in combination with geochemical modeling, plate reconstruction, and seismic topography, suggest that tearing or fragmentation of the subducted paleo‐Pacific slab during Late Cretaceous may trigger melting of the refractory lower oceanic cumulates. Our results demonstrate that lower oceanic gabbroic crust could also play an important role in the generation of intracontinental magmatism, which may previously have been underestimated.

Clinical analysis of extended PFNA combined with MIPPO plate for reconstruction of lateral wall in treatment of AO-A3.3 intertrochanteric fracture

To compare the clinical efficacy of lengthened proximal femoral nail anti-rotation(PFNA) combined with minimally invasive percutaneous plate osteosynthesis(MIPPO) and common PFNA in the treatment of AO-A3.3 intertrochanteric fracture. The clinical data of 58 patients with AO-A3.3 intertrochanteric fracture treated from January 2015 to April 2020 were retrospectively analyzed. Among them, 27 patients were treated with extended PFNA + MIPPO plate to reconstruct the lateral wall (group A), and 31 patients were treated with closed reduction and PFNA fixation (group B). The bleeding volume, operation time, femoral neck length and tip apex distance(TAD), fracture healing time and postoperative complications were observed and compared between two groups. Harris score was used to evaluate hip joint function 10 months after operation. All patients were followed up for 12 to 28 months. The incision healed well after operation. The bleeding volume and operation time of group A were significantly more than that of group B (P<0.05), and the fracture healing time of group A was significantly less than that of group B(P<0.05). There was no significant difference in the length of femoral neck between two groups at 2 days after operation(P>0.05). The length of femoral neck at 6 months after operation in each group was shorter than that at 2 days after operation(P<0.05), and the shortening of femoral neck at 6 months after operation in group B was significantly shorter than that in group A(P<0.05). There was no significant difference in TAD values between two groups at the same time point(P>0.05) at 2 days and 6 months after operation. There was no significant difference in TAD values between 2 days and 6 months after operation(P>0.05). The incidence of complications in group B was significantly higher than that in group A(P<0.05). The Harris scores of hip joint function in group A were higher than those in group B 10 months after operation (P<0.05). Compared with the treatment of AO-A3 femoral intertrochanteric fracture with closed reduction and PFNA fixation, the lengthened PFNA combined with MIPPO small plate for reconstruction and fixation of the lateral wall can promote the fracture healing, improve the patient's functional recovery, and significantly reduce the complications.

Evaluation on the use of plate positioning guide (PPG) on the placement accuracy of post-hemimandibulectomy plate reconstruction

Improper placement of the reconstruction plate can lead to postoperative complications. Placing reconstruction plates that have arch for operation is made easier with the plate positioning guide (PPG) as a transfer method of reconstruction plate. This study aimed to assess the impact of PPG on the placement accuracy of reconstruction plate as determined by the symmetrical breadth of the mandibular arch and the consistent placement of reconstruction plate following hemimandibulectomy. According to the inclusion criteria, this was a retrospective cross-sectional study with 12 participants (n = 12) after hemimandibulectomy. Subjects were divided into PPG (n = 6) and Non-PPG (n = 6) groups. Measurement of the difference in the width of the mandibular arch and the height of the placement of the reconstruction plate between the reconstructed and non-resected sides in three positions (anterior, posterior, and angulus) was conducted using submentovertex radiographs and orthopantomogram (OPG) through the RadiAnt DICOM Viewer software. The placement accuracy of the reconstruction plates was analyzed using a one-sample t-test with p-value 0.05. The results showed that the placement accuracy of the reconstruction plate in the PPG group were accurate (p = 0.590), and the Non-PPG group was inaccurate (p = 0.000); with the independent sample test. There was a significant difference between the two groups (p = 0.000). Plate positioning guide provides better symmetry of the mandibular arch width post-hemimandibulectomy.

Significance of a late neoproterozoic – Early Cambrian southern Baltica active margin in late-stage Rodinian and early Gondwanan reconstructions

New whole-rock geochemical data indicate changing provenance of sedimentary rocks deposited on the southern margin of Baltica in the late Neoproterozoic to early Paleozoic. The oldest part of the sequence is characterized by highly weathered detritus sourced from a mafic igneous source, inferred to be the nearby Volyn Large Igneous Province (L.I.P.), in an intracontinental rift (aulacogen) setting. Neoproterozoic–Cambrian boundary sequences are weakly weathered and sourced from intermediate to felsic rocks in an active margin setting whereas the youngest parts of the sequence exhibit significant quartz accumulation consistent with deposition of recycled material in a passive margin setting. These data support published U-Pb and Lu-Hf zircon data from the same sedimentary sequence where the Neoproterozoic-Cambrian boundary strata are characterized by anomalously high Ediacaran–Cambrian zircon contribution with juvenile isotopic composition. Taken together, these data indicate a cryptic late Neoproterozoic–early Cambrian active margin along the periphery of southern Baltica. Based on a correlation of similarly aged foreland basin and accretionary complexes, and links to paleomagnetically constrained plate reconstructions it is hypothesized that this detritus was sourced from the Avalonian micro-continent and a Cambrian arc terrane that is today preserved in high-grade metamorphic complexes of the European Variscides. These findings have potentially profound implications for our understanding of the supercontinent cycle that links the Rodinia to Pangea supercontinents, in particular the role played by Baltica-derived terranes in Paleozoic collisional orogeny.

Towards mechanobiologically optimized mandible reconstruction: CAD/CAM miniplates vs. reconstruction plates for fibula free flap fixation: A finite element study.

Due to their advantages in applicability, patient-specific (CAD/CAM) reconstruction plates are increasingly used in fibula free flap mandible reconstruction. In addition, recently, CAD/CAM miniplates, with further advantages in postoperative management, have been introduced. However, biomechanical conditions induced by CAD/CAM systems remain partially unknown. This study aimed to evaluate the primary fixation stability of CAD/CAM fixators. For a patient-specific scenario, the biomechanical conditions induced in a one segmental fibula free flap stabilized using either a CAD/CAM reconstruction plate or CAD/CAM miniplates were determined using finite element analysis. The main output parameters were the strains between intersegmental bone surfaces and stresses in the fixation systems due to different biting scenarios. CAD/CAM miniplates resulted in higher mechanical strains in the mesial interosseous gap, whereas CAD/CAM reconstruction plate fixation resulted in higher strains in the distal interosseous gap. For all investigated fixation systems, stresses in the fixation systems were below the material yield stress and thus material failure would not be expected. While the use of CAD/CAM miniplates resulted in strain values considered adequate to promote bone healing in the mesial interosseous gap, in the distal interosseous gap CAD/CAM reconstruction plate fixation might result in more beneficial tissue straining. A mechanical failure of the fixation systems would not be expected.

Surgical correction of the pelvis after malunited pelvic fracture.

Mal-union and non-union of the pelvic bones is a complicationof the treatment of its injuries, which mostly occur with 61C fracturesaccording to the AO/OTA classification. Objective. To analyzethe results of surgical treatment of a female patient with a pelvic fracturethat has healed with residual deformity (shortening, posteriordisplacement, internal rotation to the right and external rotation tothe left) and to demonstrate the importance of careful planning withthe involvement of 3D modeling in cases of reconstructive surgeryafter a pelvic fracture. Methods. The study has the form of a clinicalcase description. The results of the treatment were evaluated accordingto the IPS score. During the examination, multiple fracturesof the pelvic bones and dislocations corresponding to type 61 C3 accordingto the AO/OTA classification were revealed. After a CT scanof the pelvis with 3D reconstruction, a 3-stage surgical interventionwas planned and performed. The first stage: 2 K-wires were percutaneouslyinserted through the left sacroiliac joint at the SI-SII level tothe area of the planned osteotomy of the sacrum; through a paramedianaccess, a longitudinal osteotomy of the sacrum was performedon the right through the area of the previous fracture with mobilizationof the lateral fragment. The second: transection of the symphysis,osteotomy of the pubic bone at the site of improper fusion, repositioning,fixation with a simulated reconstructive plate and standardscrews; reposition of the right pelvic semiring. The third: adequateclosure of the posterior wound. For control, a CT scan of the pelvisand a comparative evaluation of the main projections and images on3D reconstruction and frontal sections were performed. 4 months afterthe operation, the patient carries out a full axial load with no painsyndrome and continues rehabilitation aimed at returning the correctstereotype of gait. The functional result was estimated at 90 pointson the IPS scale. Conclusions. Late surgical correction is difficultto perform and is associated with a large number of possible severecomplications. Careful preoperative planning is the key for the pelvicfractures treatment and their consequences. The best method of preventionof late reconstructions is the correct initial definitive treatment.This requires the presence of specialized medical centers withexperts specializing in the treatment of pelvic fractures, the necessaryequipment and a defined protocol

Accuracy and outcomes of virtual surgical planning and 3D-printed guides for osseous free flap reconstruction of mandibular osteoradionecrosis

ObjectivesVirtual surgical planning, 3D-printed osteotomy guides and preoperatively-bent or custom-milled mandibular reconstruction plate (VSP/3Dprinted-guide/plate) have been shown to ease intraoperative decision making and reduce operative time. Few studies have examined outcomes of VSP/3Dprinted-guide/plate specifically for mandibular osteoradionecrosis (mORN) cases, which pose unique challenges. We aimed to examine reconstruction accuracy, functional outcomes, and postoperative complications following osseous-free-flap reconstruction with VSP/3Dprinted-guide/plate for mORN. Materials and methodsSingle academic medical center retrospective case series of ORN-related osseous-free-flap mandibular reconstructions with VSP/3Dprinted-guide/plate between January 2015 and March 2021. Most cases were performed by the same two-surgeon team. Outcomes include reconstruction accuracy (assessed by 3D-overlay computer models with cephalometric and donor-bone segment length measurements), complications and function. ResultsTwenty-six cases were identified with a mean follow-up of 85 weeks. Most patients were male (69 %); mean age was 64 years. 3D-model-overlay demonstrated minimal deviation between planned and actual reconstruction among 18 evaluable cases: intercondylar distance = 1.46 mm (SD 2.4); intergonial distance = 1.82 mm (SD 2.0); anterior-posterior distance = 2.14 mm (SD 1.9); gonial angle = 3.33 degrees (SD 2.4). Mean change donor-bone segment length inferiorly 4.39 mm (SD 4.3) and superiorly 3.43 mm (SD 4.0). Complications: returned to operating room (N = 2), minor primary/neck site infection/dehiscence (N = 11). Function improved postoperatively: 20/21 (95 %) cases with preoperative pain, resolved; 13/20 (65 %) with preoperative trismus, improved; 21/24 (87 %) with preoperative malocclusion/jaw malignment, improved. ConclusionsThis is the largest series of VSP/3Dprinted-guide/plate surgery for mORN to date. Mandibular reconstruction for ORN is aided by VSP/3Dprinted-guide/plate with accurate results, acceptable complications, and improved function.

Late Mesozoic multi-plate convergence in East Asia: Insights from 3-D global mantle flow models

Due to the Mesozoic multi-plate convergence, prominent continental marginal tectonic belts were formed in East Asia. The significant intra-continental magmatic events in the interior of East Asia were also closely related to the subduction of the surrounding oceans. Therefore, clarifying the subduction-related mantle dynamics during the Mesozoic super-convergence in East Asia is critical in understanding the crust-mantle interactions and the episodic tectono-magmatism. In this study, we obtain the subduction-related dynamic topography by coupling global mantle flow and plate reconstruction motions to capture the evolution scenarios in 200–90 Ma. Our modeling results are as follows: (1) In the Early Jurassic, the East Asian continental margin breakup is closely related to the mantle-driven dynamic topography. The offshore dynamic subsidence dominates the continental breakup. (2) The closure of the Paleo-Tethys Ocean and the subduction of the Bangonghu-Nujiang Ocean contribute to the southward migration of the dynamic topography. Concurrently, the continuous subduction of the Paleo-Pacific Plate leads to the onshore dynamic uplift, which results in subduction-related orogenesis in eastern East Asia. The dynamic uplift does not massively progress westward in Mainland China, suggesting that extensive intra-continental compressional deformation results from tectonic uplift rather than mantle-induced dynamic uplift. (3) The regression of the dynamic subsidence zone since 130 Ma marks the start of the topographic collapse in the East Asian continental margin through the back-arc extension. (4) The alternating compression-extension scenarios are identified in the main compressional and extensional stages, respectively, showing that dynamic topography is closely related to the evolution of the marginal tectonic belts in eastern East Asia. In conclusion, the subduction-related dynamic topography systematically reveals the deep dynamics involved in the formation, evolution, and collapse of the marginal tectonic belts in East Asia and is of great significance in understanding the related mantle dynamics during the Late Mesozoic.

High complication rate with titanium plates for chest wall reconstruction following tumour resection.

The reconstruction of the chest wall defect after tumour resection presents a challenge. Titanium rib plates were presented as a reconstruction option due to its biocompatibility, flexibility and pliability. The aim of this study was to evaluate the outcome of single-centre cohort treated with chest wall reconstruction after tumour resections, with a focus on the titanium rib plates reconstruction. We retrospectively reviewed the data of 26 patients who underwent wide resection for malignancies of the chest wall, where reconstruction was performed using polypropylene mesh, porcine dermal collagen mesh with or without titanium rib plates, operated on between 2012 and 2019. Events being associated with the surgery requiring revision were rated as complications. Most of the patients had primary tumours (n = 19; 73%). A mean of 3.7 ribs (range: 1-7) was resected. Reconstruction was performed with titanium rib plates (13 patients, 50%), of these 11 were performed with additional mesh grafts. The remaining 13 patients (50%) underwent reconstruction with mesh grafts only. Fourteen patients (54%) developed a complication requiring surgical revision, after a median of 5.5 months. The most common complication was wound healing deficit (n = 4), plate fracture (n = 2), mesh rupture (n = 2), infection (n = 2) and local recurrence (n = 2). The only factor being associated with the development of complications was the usage of a plate (P = 0.015), irrespective of defect size (P = 0.29). The high complication rate is found when using titanium plates for chest wall reconstruction after tumour resection. A high caution is recommended in choosing the chest wall reconstruction method.

Straight-segment mandibulectomy: a reproducible porcine mandibular critical-size defect model

Porcine mandibular defect models are commonly used for the preclinical evaluation of reconstruction techniques. Existing studies vary in technique, complexity, and postoperative outcomes. The procedures are complex and often described without sufficient detail. We describe in detail a simple and reproducible method for creating a critical-size mandibular defect in a porcine model. Seven hemimandibular critical size defects were created in five male Yorkshire-Landrace pigs, three with unilateral defects and two with bilateral defects. A transverse incision was made over the mandibular body. Periosteum was incised and elevated to expose the mandibular body and a critical-size defect of 30 × 20 mm created using an oscillating saw. The implant was inserted and fixed with a titanium reconstruction plate and bicortical locking screws, and the wound closed in layers with resorbable sutures. Intraoral contamination was avoided. Dentition was retained and the mental nerve and its branches preserved. The marginal mandibular nerve was not encountered during dissection. All pigs retained normal masticatory function, and there were no cases of infection, wound breakdown, haematoma, salivary leak, or implant-related complications. The procedure can be performed bilaterally on both hemimandibles without affecting load-bearing function. All pigs survived until the end point of three months. Postoperative computed tomographic scans and histology showed new bone formation, and a three-point bend test showed the restoration of biomechanical strength. Straight-segment mandibulectomy is a simple and reproducible method for the creation of critical-size mandibular defects in a porcine model, simulating a load-bearing situation.

A Complex Mantle Plume Head Below East Africa‐Arabia Shaped by the Lithosphere‐Asthenosphere Boundary Topography

AbstractHot plumes rising from Earth's deep mantle are thought to cause uplift, rifting and large igneous province (LIP) emplacement. LIP volcanism in continents often spans tens of Ma and scatters unevenly over broad areas. This has been attributed to lateral flow of hot plume material, but observational evidence on such flow is scarce. New waveform tomography with massive data sets reveals detailed seismic velocity structure beneath the East Africa‐Arabia region, where these processes occur at present. It shows interconnected sub‐lithospheric corridors of hot, partially molten rock, fed by three mantle upwellings beneath Kenya, Afar, and Levant. The spatio‐temporal distribution of the volcanism suggests that we are witnessing an integral plume head, which morphed into a three‐pointed star by ponding and channeling within thin‐lithosphere corridors. Plate reconstructions indicate that it spread south‐to‐north since ∼45 Ma. These results suggest that complex‐shape plume heads can explain the enigmatic, scattered LIP volcanism and are, probably, an inherent feature of plume‐continent interaction.

NW Pacific‐Panthalassa Intra‐Oceanic Subduction During Mesozoic Times From Mantle Convection and Geoid Models

AbstractPacific‐Panthalassa plate tectonics are the most challenging on Earth to reconstruct during the Mesozoic and Cenozoic eras due to extensive subduction, which has resulted in large (&gt;9,000 km length) unconstrained gaps between the Pacific and Laurasia (now NE Asia) back to the Early Jurassic. We build four contrasted NW Pacific‐Panthalassa global plate reconstructions and assimilate their velocity fields into global geodynamic models. We compare our predicted present mantle structure, synthetic geoid and dynamic topography to Earth observations. P‐wave tomographic filtering of predicted mantle structures allows for more explicit comparisons to global tomography. Plate reconstructions that include intra‐oceanic subduction in NW Pacific‐Panthalassa fit better to the observed geoid and residual topography, challenging popular models of Andean‐style subduction along East Asia. Our geodynamic models predict significant SE‐ward lateral slab advections within the NW Pacific basin lower mantle (∼2,500 km from Mesozoic times to present) that would confound “vertical slab sinking”‐style restorations of imaged slabs and past subduction zone locations.

Cluster Analysis of Dense GNSS Velocity Field Reveals Characteristics Associated With Regional Tectonics in New Zealand

AbstractNew Zealand is located in the converging zone between the Australian and Pacific Plates. The Pacific Plate is descending beneath the Australian Plate in the north of New Zealand, while the Australian Plate is descending beneath the Pacific Plate in the south. The contrastive tectonics is connected by the Alpine Fault, the transform fault with NE‐SW strike along most of the length of New Zealand. Recently, previous studies showed that a cluster analysis of dense Global Navigation Satellite System (GNSS) velocity field objectively yields major velocity discontinuities, which may reflect an important tectonic boundary. We applied two different types of clustering algorithms: hierarchical agglomerative clustering (HAC) and Euler pole clustering (EPC), to the dense GNSS horizontal velocity data in New Zealand. Both methods agree that the primary kinematic boundary lies from the northern Wairarapa region to the southwestern end of the Alpine Fault. The HAC introduces a cluster boundary along the North Island Dextral Fault Belt whereas EPC emphasizes the importance of the Taupo Volcanic Zone (TVZ). Since EPC fits the data reasonably well, it indicates the TVZ is an important boundary. This result displays the limitation of the flat earth assumption. The Chatham Islands is identified as an independent cluster by the HAC, but not by the EPC. Further cluster splits illustrate that the relative motion between the two plates is accommodated by distributed deformation in the Marlborough Fault Zone in the South Island whereas the North Island is characterized by local block rotations.

Virtual planning and 3D-printed guides for mandibular reconstruction: Factors impacting accuracy.

Examine accuracy and factors impacting accuracy for mandibular reconstruction with virtual surgical planning, 3D printed osteotomy guides and preoperatively bent mandibular reconstruction plate (VSP/3Dprinted-guide/plate). Retrospective review of osseous-free-flap mandibular reconstructions with VSP/3Dprinted-guide/plate between January 2015 and July 2020 at a single academic medical center.Patient demographics, disease, and treatment variables were extracted. Accuracy was assessed by 3D-model-overlay with cephalometric and donor-bone segment length measurements. Multivariate analyses were performed to determine factors impacting cephalometric accuracy. 60 cases met criteria: 41 (68%) cancer, 14 (23%) osteoradionecrosis (ORN), 5 (8%) secondary mandibular reconstruction. Thirteen cases (22%) were Brown class III or IV. Thirty-nine cases (65%) had ≥2 flap bone segments. Average donor-bone length was 82 mm (SD: 28). 3D-model-overlay accuracy demonstrated minimal deviation between planned and actual reconstruction: intercondylar distance=2.10 mm (SD: 2.2); intergonial distance=2.23 mm (SD: 1.9); anterior-posterior distance (APD)=1.76 mm (SD: 1.5); gonial angle (GA)=3.11 degrees (SD: 2.4). Mean change in donor-bone segment length inferiorly was 2.67 mm (SD: 2.6) and superiorly 3.27 mm (SD: 3.2). Higher number of donor-bone segments was associated with decreased accuracy in GA (p= .023) and longer donor-bone length was associated with decreased accuracy in APD (p= .031). To our knowledge this is the largest series assessing surgical accuracy of VSP/3Dprinted-guide/plate for osseous-free-flap mandibular reconstruction. We demonstrate highly accurate results, with increased number of donor-bone segments and donor-bone length associated with decreased accuracy. Our findings further support VSP/3Dprinted-guide/plate as a reliable and accurate tool for mandibular reconstruction. Level 4.