Reconstruction Plate Research Articles

The assembly of Pangaea: geodynamic conundrums revisited

Geodynamic models for Pangaea assembly require knowledge of Paleozoic mantle convection patterns. Application of basic geodynamic principles to Neoproterozoic–Paleozoic plate reconstructions yields Pangaea in the incorrect configuration (predicting that it should have formed by consumption of the exterior palaeo-Pacific Ocean instead of the Iapetus, Rheic and Proto-Tethys oceans). We contend that the mantle legacy of Late Neoproterozoic–Cambrian amalgamation of Gondwana must be factored into models for Pangaea amalgamation. Proxy data suggest that the mantle downwelling driving Pan-African collisions and Gondwana assembly evolved into a mantle upwelling as evidenced by the interplay between subduction-related and plume-related tectonics around the periphery of Gondwana. Orthoversion theory, whereby a supercontinent assembles c . 90° away from the centre of the previous supercontinent, suggests that Gondwana amalgamated above an intense downwelling along a meridional subduction girdle that bisected two antipodal sub-equatorial upwellings. Several processes beneath and around Gondwana reduced the intensity of the original downwelling, as evidenced by plume-related activity along its margins, initiation of subduction zone rollback, and the export of terranes from Gondwana that collided with the margin of Laurentia–Baltica. As upwelling beneath it intensified, Gondwana migrated along the girdle until it collided with Laurentia–Baltica, resulting in the final assembly of Pangaea.

Risk Factors for Plate Infection, Exposure, and Removal in Mandibular Reconstruction.

Mandibular plate reconstruction (MPR) is often indicated after tumor ablation, osteoradionecrosis excision, and traumatic bone loss to restore oral functionality and facial cosmetics. There are limited analyses identifying risk factors that lead to plate infection (PIn), exposure, and removal ("plate complications"). Retrospective cohort study. Academic tertiary medical center. Patients who underwent MPR from 2013 to 2022 were identified. Risk factors for plate complications were analyzed based on demographic, clinical, intraoperative, and postoperative factors. Multivariable analysis was conducted with logistic regression. Survival analysis was conducted with a Cox model. Of the 188 patients analyzed, 48 (25.5%) had a plate complication [infection: 22 (11.7%); exposure: 23 (12.2%); removal: 35 (18.6%)]. Multivariate analysis revealed predictive associations between at least 1 plate complication and the following variables: smoking status, soft tissue defect size, number of plates, average screw length, and various postoperative complications. Other associations approached the threshold for significance. Prior and adjuvant radiation therapy, type of free flap, stock versus custom plates, and perioperative antibiotic prophylaxis regimens were not associated with plate complications. No plate complication was independently associated with lower overall survival. PIn (hazard ratio, HR: 7.99, confidence interval, CI [4.11, 15.54]) and exposure (HR: 3.56, CI [1.79, 7.08]) were independently associated with higher rates of plate removal. Plate complications are relatively common after MPR. Smoking history, specific disease characteristics, hardware used during surgery, and postoperative complications may help identify higher-risk patients, but additional larger-scale studies are needed to validate our findings and resolve discrepancies in the current literature.

The role of plume-lithosphere interaction in Hawaii-Emperor chain formation

Paleolatitudes of volcanic rocks reveal that prominent changes in volcanic trend of the Hawaii-Emperor hotspot chain represent meridional migration of the magma source. However, models assuming latitudinal plume migration fail to explain the observed age distribution, rock composition, and erratic paleolatitude changes of the oldest Emperor seamounts. Here we use data-assimilation models to better reproduce the Hawaii-Emperor hotspot track by systematically considering plate reconstruction, plume-lithosphere interaction, and simplified melt generation and migration. Our results show that plate drag and plume-ridge interaction are both important in explaining the observed seamount ages. These shallow dynamic processes could account for 50% of the observed paleolatitude’s secular reduction and erratic variations over time, where the necessary southward migration of the Hawaiian plume root is significantly less than previously thought. We conclude that plume-lithosphere interaction represents a common mechanism in affecting hotspot track, and has important implications in understanding mantle dynamics and plate reference frames.

Outcome Evaluation of Three-Dimensionally Printed Patient-Specific Surgical Plates for Mandibular Reconstruction

Outcome Evaluation of Three-Dimensionally Printed Patient-Specific Surgical Plates for Mandibular Reconstruction

The Different Surgical Approaches to Maxillofacial Reconstruction after Ballistic Trauma.

Ballistic trauma to the face is a challenge, combining complex bone injury with severe soft tissue loss. The various surgical methods available are influenced by the extent of injuries. This study compares different operative modalities and their outcomes with different variables, aiming to define the ideal therapeutic approach. We retrospectively compared reconstructive modalities used to treat facial ballistic trauma cases at Hôtel-Dieu de France Hospital, Beirut, Lebanon, for a 12-year span. Statistical analysis was used to determine correlation between several factors and satisfactory results. Eighteen patients were included, with varying degrees of bone and soft tissue loss. After conservative debridement, fractures were treated by different modalities: open reduction and internal fixation, maxillomandibular fixation, and osteosynthesis with a reconstruction plate. Although primary closure was sufficient in 10 cases, severe loss of tissues was reconstructed with a fibular free flap in five cases, radial free forearm flap in two cases, and free parascapular flap in one case. Two others received an iliac bone graft as secondary reconstruction. The average follow-up was 2.45 years. Most cases achieved good aesthetic and functional results after several secondary operations, with few late complications. Early reconstruction and younger patients were associated with better outcomes. We favor early debridement and reconstruction. Free flaps were ideal for extensive tissue loss. Bone grafting was needed secondarily. A single surgical procedure seldom led to satisfactory functional and aesthetic outcomes, and secondary operations were inevitable.

A new technique for percutaneous screw fixation for treating FFP IIIa and IIIb fragility fractures of the pelvis

To determine the presence of a consistent osseous corridor from the lateral-posterior aspect of the anterior inferior iliac spine to the sacral wing that could be used for safe trans percutaneous screw fixation for pelvic fragility fractures of the iliac wing and fracture dislocations of the sacroiliac joint (FFP types IIIa and IIIb). Computed tomography (CT) scans were obtained from 100 patients and imported to Mimics software for 3D reconstruction. Then, a cylinder was drawn to imitate the modified LC-II screw and adjusted to a maximum radius and length to obtain the feasible region. Thirteen parameters of the osseous corridor of the modified LC-II screw were measured. Differences between sex groups were compared, and significant statistical correlations were carefully studied to determine potentially important clinical relationships. The records of patients with FFP type IIIa and IIIb fragility fractures of the pelvis were extracted from our hospital. Patients who underwent modified LC-II screw fixation, LC-II screw fixation or reconstruction plate fixation were included. Patients’ operative characteristics and complications were recorded at follow-up. Fracture reduction quality was assessed using the Matta standard. Functional outcomes were evaluated using the Majeed grading system. The mean maximum diameters of the osseous corridors of the modified LC-II screw in males and females were 12.73 and 10.83 mm, respectively. The mean maximum lengths of the osseous corridors of the modified LC-II screw in males and females were 96.37 and 93.37 mm, respectively. In the treatment of patients with FFP IIIa and FFP IIIb fractures, the group of treatment by the modified LC-II screws fixation was shown significantly shorter operative time and fewer intraoperative blood loss in comparison to that by the reconstruction plates. In the present study, all the males and females had a complete osseous corridor of the modified LC-II screw. The clinical results of the patients who were treated with modified LC-II screw fixation suggest that the novel method has a good preliminary outcome.

Reconstruction plate In the Substance of Pectoralis Major Myocutaneous Flap for Reconstruction of the Mandibular Arch Defects: a Novel Technique (RISP Technique)

Reconstruction plate In the Substance of Pectoralis Major Myocutaneous Flap for Reconstruction of the Mandibular Arch Defects: a Novel Technique (RISP Technique)

Finite element analysis of the treatment of a minimally invasive approach combined with a novel anatomical locking plate for scapular body fractures

BackgroundThe minimally invasive approach for the treatment of displaced scapular neck or body fractures has the advantages of less trauma and minimal muscle dissection. In clinical practice, the minimally invasive approach combined with an anatomical locking plate has been used to treat scapular body fractures. In addition, we have made minor modifications to the minimally invasive approach. However, the biomechanical study about the approach combined with an anatomical locking plate in treating scapular body fractures was limited.MethodsFinite element analysis (FEA) was used to conduct the biomechanical comparison between the anatomical locking plate (AP model) and reconstructive plate (RP model) in the treatment of scapular body fractures through the modified minimally invasive approach. A healthy male volunteer with no history of scapula or systemic diseases was recruited. High-resolution computed tomography images of his right scapula were obtained. Two scapula models were constructed and analyzed by the software of Mimics 21.0, Geomagic Wrap 2021, SolidWorks 2021, and ANSYS Workbench 2022, respectively.ResultsThrough static structural analysis, in terms of equivalent von Mises stress, equivalent elastic strain, and total deformation, the AP model exhibited superior safety characteristics, enhanced flexibility, and anticipated stability compared with the RP model. This was evidenced by lower maximum stress, lower maximum strain and displacement.ConclusionThe minimally invasive approach combined with an anatomical locking plate for scapular body fractures had better biomechanical stability. The study provided a biomechanical basis to guide the clinical treatment of scapular body fractures.

Surgical treatment of mobile planovalgus deformation of feet using calcaneal osteotomy based on preoperative computer modeling in adolescent: a retrospective cohort study

Background: Evans calcaneal osteotomy is one of the recognized surgical techniques for the treatment of flat-valgus foot deformity in children over 12 years of age, which allows simultaneous multiplanar correction. Preoperative planning of the formed diastasis parameters to reduce the number of cases of hypo- and hypercorrection remains an urgent issue. AIM: To evaluate the results of Evans calcaneal osteotomy using the developed method of preoperative planning and fixation with the individual H-shaped reconstructive plate. MATERIALS AND METHODS: This study included 64 children aged 12–17 years with symptomatic planovalgus deformity, who were divided into two groups: in the main group, preoperative planning was used according to the developed method; in the control group for intraoperative control of correction was used only fluoroscopy and visual assessment. To study the effectiveness of the developed method, we used dynamic assessment of radiometric parameters and AOFAS questionnaire results before and after surgery. We also took into account the changes in the Foot Posture Index 6 and the Chippaux-Smirak and Stasheli podometric indices. RESULTS: In comparison with the control group, the main group showed a reduction in the swelling period after surgery, as well as the timing of the onset of full limb support, and a significant decrease in the incomplete correction. Similar dynamics was observed when studying the groups according to the Foot Posture Index 6 scale and podometric indices. CONCLUSION: The use of the developed method of preoperative planning during the Evans operation has shown its effectiveness for the treatment of flexible flatfoot deformity of the feet in adolescence.

Is eight-plate more effective than reconstruction plate in pediatric guided growth? A systematic review and meta-analysis

Is eight-plate more effective than reconstruction plate in pediatric guided growth? A systematic review and meta-analysis

Plate fixation of inferior ramus in pubis-ischium ramus improves mechanical stability in Tile B pelvic injures: a cadaveric biomechanical analysis and early clinical experience

BackgroundManagement of inferior ramus of the pubis-ischium ramus remains controversial, and related research is sparse. The main intention of this study is to describe the biomechanical and clinical outcomes of pubis-ischium ramus fractures in Tile B pelvic injuries and to identify the feasibility and necessity of fixation of the inferior ramus of the pubis-ischium ramus.MethodsThis study comprised two parts: a biomechanical test and a retrospective clinical study. For the biomechanical tests, Tile B-type pelvic injuries were modeled in six cadaver specimens by performing pubis-ischium osteotomies and disruption of the anterior and interosseous sacroiliac ligaments. The superior and/or inferior rami of the pubis-ischium ramus were repaired with reconstruction plates and separated into three groups (A, B, and C). Specimens were placed in the standing position and were loaded axially with two-leg support for three cycles at 500 N. The displacements of sacroiliac joints at osteotomy were measured with Vernier calipers and compared using statistical software. To investigate the clinical outcomes of this technique, 26 patients were retrospectively analyzed and divided into a superior ramus fixation group (Group D) and a combined superior and inferior ramus of the pubis-ischium ramus fixation group (Group E). The main outcome measures were time of operation, blood loss, postoperative radiographic reduction grading, and functional outcomes.ResultsIn the vertical loading test, Group E showed better pelvic ring stability than Group D (P < 0.05). However, the shift of the sacroiliac joints was almost identical among the three groups. In our clinical case series, all fractures in Group E achieved bony union. Group E demonstrated earlier weight-bearing functional exercise (2.54 ± 1.45 vs 4.77 ± 2.09; P = 0.004), earlier bony union (13.23 ± 2.89 vs 16.55 ± 3.11; P = 0.013), and better functional outcomes (89.77 ± 7.27 vs 82.38 ± 8.81; P = 0.028) than Group D. The incidence of sexual dysfunction was significantly lower in Group E than that in Group D (2/13 vs 7/13; P = 0.039). Bone nonunion occurred in two patients in Group D, and two patients in Group E had heterotopic ossification. None of the patients exhibited wound complications, infections, implant failures, or bone–implant interface failures.ConclusionsFixation of the inferior ramus of a pubis-ischium ramus fracture based on conventional fixation of the anterior pelvic ring is mechanically superior in cadaveric Tile B pelvic injury and shows rapid recovery, good functional outcomes, and low incidence of complications.

Does a Point-of-Care 3-Dimensional Printer Result in a Decreased Length of Surgery for Orbital Fractures?

Utilization of point-of-care 3-dimensional printing (3DP) has decreased length of surgery in facial trauma. Little is known regarding 3DP's impact on length of surgery in orbital fracture. The purpose of this study was to compare length of surgery between 3DP/preadapted (3DPPA) orbital plates and intraoperative adapted plates (IOAP) for orbital fracture reconstruction. This was a prospective, non-blinded, randomized clinical study of consecutive subjects with orbital fractures presented to Grady Memorial Hospital in Atlanta, Georgia, between January 2018 and June 2021. Subjects ≥ 18years, unilateral fracture, no previous orbital surgery, and/or congenital craniofacial anomaly were included. We excluded subjects <18years and bilateral fractures. Primary predictor variable was the treatment approach. Randomization software was used, and subjects were randomized to 3DPPA or IOAP groups. Primary outcome variable was length of surgery in minutes. Secondary outcomes were the time required for plate insertion and fixation in minutes, operating room (OR) charges, and orbital volume (OV) calculation. Age, sex, race, etiology, laterality, location, dimension, indication for surgery, postoperative enophthalmos, and diplopia. Univariate and bivariate analyses were calculated. Statistical significance was P<.05. Twenty-five subjects met the inclusion criteria. Mean ages in 3DPPA and conventional IOAP groups were 41.5 (±9) and 38.2 (±10, P=.31), respectively. The mean length of surgery was 32.6 (±13.7) in 3DPPA and 53.3 (±12.8, P<.001) in conventional IOAP. The mean time required for plate insertion and fixation was 15.8n (±14.4) in 3DPPA and 41.4 (±9.4, P<.001) in conventional IOAP. The mean OR charges were $1,072.5 (±524.6) in 3DPPA and $1,757.3 (±422.6, P ≤ 0.001) in conventional IOAP. The mean calculated OV of uninjured and reconstructed orbit for the 3DPPA was 23.5 (±3.2)cm3 and 23 (±3.5, P=.37)cm3, respectively. The mean calculated OV of uninjured and reconstructed orbit for conventional IOAP was 28.6 (±3.6)cm3 and 22.8 (±2.6, P<.001)cm3, respectively. Using 3DP to produce a model that enables preoperative plate bending/adaptation reduces the length of surgery, decreases OR charges, and results in predictable OV.

An experimental study of a novel external fixator based on universal joints for the rapid initial stabilization of mandibular comminuted fractures

PurposeShaping and assembling contemporary external fixators rapidly for the severe mandibular fractures remains a challenge, especially in emergency circumstance. We designed a novel external fixator that incorporates universal joints to provide the stabilization for mandibular comminuted fractures. This study aims to confirm the efficacy of this novel external fixator through biomechanical tests in vitro and animal experiments. MethodsIn vitro biomechanical tests were conducted using 6 fresh canine with mandibular defect to simulate critical comminuted fractures. Three mandibles were stabilized by the novel external fixator and other mandibles were fixed by 2.5 mm reconstruction plates. All fixed mandibles were subjected to loads of 350 N on the anterior regions of teeth and 550 N on the first molar of the unaffected side. The stability was evaluated based on the maximum displacement and the slope of the load-displacement curve. In animal experiments, 9 beagles with comminuted mandibular fractures were divided into 3 groups, which were treated with the novel external fixation, reconstruction plate, and dental arch bar, respectively. The general observation, the changes in animals’ weight, and the surgical duration were recorded and compared among 3 groups. The CT scans were performed at various intervals of 0 day (immediately after the surgery), 3 days, 7 days, 14 days, 21 days, and 28 days to analyze the displacement of feature points on the canine mandible and situation of fracture healing at 28 days. The statistical significance was assessed by the two-way analysis of variance test followed by the Bonferroni test, enabling multiple comparisons for all tests using GraphPad Prism10.1.0 (GraphPad Inc, USA). ResultsThe outcomes of the biomechanical tests indicated that no statistically significant differences were found in terms of the maximum displacement (p = 0.496, 0.079) and the slope of load displacement curves (p = 0.374, 0.349) under 2 load modes between the external and internal fixation groups. The animal experiment data showed that there were minor displacements of feature points between the external and internal fixation groups without statistic difference, while the arch bar group demonstrated inferior stability. The CT analysis revealed that the best fracture healing happened in the internal fixation group, followed by the external fixation and arch baring at 28 days after fixation. The external fixation group had the shortest fixation duration (25.67 ± 3.79) min compared to internal fixation ((70.67 ± 4.51) min, p < 0.001) and arch baring ((42.00 ± 3.00) min, p = 0.046). ConclusionThe conclusion of this study highlighted the efficacy and reliability of this novel external fixator in managing mandibular fractures rapidly, offering a viable option for the initial stabilization of comminuted mandibular fractures in the setting of emergency rescue.

Finite element analysis and biomechanical study of "sandwich" fixation in the treatment of elderly proximal humerus fractures.

Proximal humerus fractures (PHFs) are common in the elderly and usually involve defects in the medial column.The current standard for medial column reconstruction is a lateral locking plate (LLP) in combination with either an intramedullary fibula support or an autogenous fibula graft. However, autogenous fibula graft can lead to additional trauma for patients and allogeneic fibular graft can increase patients' economic burden and pose risks of infection and disease transmission. The primary objective of this study was to introduce and assess a novel "Sandwich" fixation technique and compare its biomechanical properties to the traditional fixation methods for PHFs. In this study, we established finite element models of two different internal fixation methods: LLP-intramedullary reconstruction plate with bone cement (LLP-IRPBC) and LLP-intramedullary fibula segment (LLP-IFS). The biomechanical properties of the two fixation methods were evaluated by applying axial, adduction, abduction, torsional loads and screw extraction tests to the models. These FEA results were subsequently validated through a series of biomechanical experiments. Under various loading conditions such as axial, adduction, abduction, and rotation, the LLP-IRPBC group consistently demonstrated higher structural stiffness and less displacement compared to the LLP-IFS group, regardless of whether the bone was in a normal (Nor) or osteoporotic (Ost) state. Under axial, abduction and torsional loads, the maximum stress on LLPs of LLP-IRPBC group was lower than that of LLP-IFS group, while under adduction load, the maximum stress on LLPs of LLP-IRPBC group was higher than that of LLP-IFS group under Ost condition, and almost the same under Nor condition. The screw-pulling force in the LLP-IRPBC group was 1.85 times greater than that of the LLP-IFS group in Nor conditions and 1.36 times greater in Ost conditions. Importantly, the results of the biomechanical experiments closely mirrored those obtained through FEA, confirming the accuracy and reliability of FEA. The novel "Sandwich" fixation technique appears to offer stable medial support and rotational stability while significantly enhancing the strength of the fixation screws. This innovative approach represents a promising strategy for clinical treatment of PHFs.

Jan Mayen Microcontinent Composite Tectono-Sedimentary Element and Jan Mayen Prograded Margin Tectono-Sedimentary Element, Greenland Sea

The Jan Mayen Micro-Continent (JMMC) is the result of two Cainozoic phases of continental breakup, and subsequent seafloor spreading. The first established a spreading ridge system consisting of the Reykjanes, Ægir, and Mohn spreading ridges between Norway and Greenland in early Eocene. The second phase established the Kolbeinsey Ridge in Oligocene/Miocene separating the JMMC form Greenland. Two major stratigraphic elements are established accordingly, the Jan Mayen Micro-Continent Composite Tectono-Sedimentary Element (JMMC CTSE) for the Middle Devonian to Miocene succession, and the Jan Mayen Prograded Margin Tectono-Sedimentary Element (JMPM TSE) for the Miocene to Holocene succession. OBS refraction data show that the JMMC is underlain by a generally thickened crust. Plate reconstructions show that this crust most likely is a remnant of continental crust rifted off East Greenland, and thereby, consist of rocks that correlates with the Late Palaeozoic and Mesozoic strata stratigraphy of the conjugate margins of East Greenland and Norway known to be hydrocarbon. The arrival of the Iceland hot spot and the breakup magmatism greatly influenced the historic and current heat flow. Published maturation models and play analysis, show that there is a potential for oil and gas in the Jan Mayen Ridge within the JMMC.

Independent volumetric internal fixation reduces posterior column acetabular fracture site motion as compared to plate/screw construct: A biomechanical analysis

Aims & objectivesTo establish whether a suprapectineal pelvic reconstruction plate and posterior column screw (P&S) construct or a single 6.5-mm cannulated posterior column screw (PCS) construct demonstrates greater mechanical stability for fixation of acetabulum fractures involving the posterior column (PC). We hypothesized that the PCS construct would result in less fracture site motion. Materials & methodsTwelve fourth-generation composite hemipelvi were utilized, 6 for each construct. The P&S construct consisted of a suprapectineal pelvic reconstruction plate with two 3.5-mm posterior column screws crossing the fracture site in lag-by-technique fashion and two screws anchoring the plate to the sciatic buttress. The PCS construct consisted of a single 6.5-mm partially threaded cannulated screw placed in an antegrade fashion. Both fixation models were cyclically loaded at 0.5 cycles/second at 400N and 800N, first in a sit-to-stand position that is expected during recovery, and subsequently in a squat-to-stand position to test overload conditions. ResultsUnder sit-to-stand loading, the PCS construct resulted in less motion at the fracture site than the P&S construct (0.06 ± 0.02 mm vs 0.1 ± 0.02 mm at 400N, p = 0.02; 0.13 ± 0.03 mm vs 0.19 ± 0.04 mm at 800N, p = 0.03). The PCS construct also demonstrated less fracture site motion under squat-to-stand loading (0.22 ± 0.13 mm vs 1.9 ± 0.5 mm at 400N, p = < 0.001; 1.48 ± 0.44 mm vs 4.77 ± 0.3 mm at 800N, p = < 0.001). At 800 N, half of the repairs failed during squat-to-stand loading (2 PCS, 4 P&S). ConclusionFixation of the posterior column of the acetabulum with a 6.5-mm cannulated screw demonstrated comparable fracture motion upon loading compared to the plate and screw construct.

A Detailed Reconstruction of the Woodlark Basin

AbstractAn animated 100,000‐year‐interval tectonic reconstruction of the Woodlark Basin in the southwest Pacific illustrates how, at intermediate initial spreading rates, orogenic continents break up (dyke model), spreading segments nucleate, transform faults initiate and ocean basins evolve. We refine the location/timing of initial seafloor spreading and Euler poles of rotation back to 6.2 Ma. In the easternmost basin, where spreading younger than 2.6 Ma is not co‐polar with that to the west, we recognize the formation of a Ghizo microplate and Ranongga Transform Fault at ∼2.6 Ma and a 3‐degree rotational opening of the Itina Trough from 2.6 to 1.0 Ma. Allowing for that motion, we show that the 5.2–2.6 Ma seafloor in the easternmost basin formed co‐polar with that to the west. We also identify a ridge jump reorientation at ∼1.0 Ma that formed the NE‐trending Simbo Spreading Segment, whose neovolcanic zone includes Simbo Island and a submarine edifice to its south. Proposed deterministic models of ridge propagation (due to topographic gradients, mantle flow away from hotspots and/or changing plate motion) are not consistent with those observed; mantle chemical heterogeneities and melting anomalies are a potential cause that remains to be tested. We reconstruct the northern conjugate of the oldest extant oceanic crust and estimate the initiation of its subduction at ∼2.6 Ma, concomitant with observed changes in plate motion and segmentation. Where subducted, the young oceanic lithosphere between the conjugate rifted margins appears to be resorbed into the mantle, leaving a slab window where the Pacific subducted slab remains attached.

Present day mantle structure from global mantle convection models since the Cretaceous

SUMMARY Using forward mantle convection models starting at 140 Ma, and assimilating plate reconstructions as surface velocity boundary condition, we predict present-day mantle structure and compare them with tomography models, using geoid as an additional constraint. We explore a wide model parameter space, such as different values of Clapeyron slope and density change across 660 km, density and viscosity of the thermochemical piles at the core–mantle boundary (CMB), internal heat generation rate, and model initiation age. We also investigate the effects of different strengths of a weak layer below 660 km and weaker asthenosphere and slabs. Our results suggest that slab structures at different subduction zones are sensitive to the viscosity of the asthenosphere, strength of slabs, values of Clapeyron slope and the density and viscosity of the thermochemical piles, while different internal heat generation rates do not affect the slab structures. We find that with a moderately weak asthenosphere ($10^{20}$ Pa·s) and strong slabs, the predicted slab structures are consistent with the tomography models, and the observed geoid is also matched well. Moreover, our models successfully reproduce the degree-2 structure of the lower mantle beneath Africa and the Pacific, also known as Large Low Shear Velocity provinces (LLSVPs). A moderate Clapeyron slope of −2.5 MPa K−1 at 660 km aids in slab stagnation while higher values result in massive slab accumulation at that depth, ultimately leading to slab avalanches. We also find that the convective patterns in the thermal and thermochemical cases with slightly denser LLSVPs are similar, although the geoid amplitudes are lower for the latter. However, with more dense LLSVPs, the slabs cannot perturb them and no plumes are generated. Plumes arise as thermal instabilities from the edges of the LLSVPs, when cold and viscous slabs perturb them. While our predicted plume locations are consistent with the observed hotspot locations, matching the plume structures in tomography models is difficult. These plumes are essential in fitting the finer features of the observed geoid. In longer-duration models, more voluminous subducted material reaches the CMB, which tends to erode the LLSVPs significantly, and yields a poor fit to the observed geoid. Our results suggest that with the presence of a thin, moderately weak layer below 660 km, a slightly dense LLSVP, and Clapeyron slope of −2.5 MPa K−1, the velocity anomalies in seismic tomography and the long-wavelength geoid can be matched well. One of the limitations of our models is that the assimilated plate motion history may be too short to overcome arbitrary initial conditions effects. Also, assimilated true plate velocities in our models may not represent the true convective vigour of the Earth.

Anterior Plate-Supported Cannulated Screw Surgery for Ankle Arthrodesis: Clinical and Radiologic Results in Patients with Trauma-Related End-Stage Ankle Osteoarthritis.

BACKGROUND This retrospective study included 31 patients from 2 centers in Türkiye with posttraumatic ankle osteoarthritis treated with anterior tibiotalar arthrodesis using an anterior plate and cannulated screw fixation, with 6 months of follow-up. MATERIAL AND METHODS In this bi-center study, conducted between January 2018 and July 2022, we retrospectively reviewed the digital records of 31 patients with end-stage posttraumatic ankle osteoarthritis who were treated with anterior tibiotalar arthrodesis surgery using 2 or 3 cannulated screws and the anterior plating technique. Data on age, gender, comorbidities, and smoking were recorded, as were operative technique and graft use. Union characteristics, complications, visual analog scale (VAS) results, and Maryland functional scoring were assessed preoperatively and at the 6-month follow-up visit. RESULTS The mean age of the 31 (n=13 male, n=18 female) patients was 55.5 (19-82) years. The union findings were good in 26 (83.9%) of the patients and late in 3 (9.7%) of them. Nonunion was seen in 2 (6.5%) patients. Complications were observed in 7 (22.6%) patients. Union formation was statistically significantly prolonged among the cases with complications (P=0.002). The smoking rate was significantly higher in patients encountering complications (P=0.001). Among cases with complications, the VAS and Maryland scores recorded in the postoperative sixth month were significantly higher (P=0.027, P=0.018, respectively). The mean union time was 13.5±6.5 weeks among all of the patients. CONCLUSIONS Our study showed that cannulated screw fixation, strengthened with the common and easy-to-supply anterior reconstruction plating technique, had high fixation power and good functional results in patients with end-stage posttraumatic ankle osteoarthritis.

Comparative Evaluation of Clinical Outcome Including Neurosensory Deficit and Pain Score Variables Using Rigid Internal Fixation with Three-Dimensional Miniplate Internal Fixation in Simultaneous Angle and Contralateral Body/Parasymphysis Fractures of the Mandible: A Prospective, Randomized Controlled Study.

Purpose There have been numerous advancements in the strategies used for treating mandibular fractures in the present times, while open reduction and internal fixation is still accepted as the most preferred treatment option for such fractures despite numerous drawbacks. The aim of the present prospective, randomized controlled study was to evaluate the clinical outcome including neurosensory deficit and pain score variables in mandibular fractures that were treated using rigid internal fixation with three-dimensional (3D) miniplate internal fixation. Materials and Methods For the present study, a total of 20 patients of either sex in an age range of 18 to 55 years with simultaneous angle and contralateral body/parasymphysis fractures of the mandible were included, while the clinical outcome was compared in relation to the two groups wherein different treatment options were used including using rigid internal fixation in one as against 3D miniplate internal fixation in the other. Results Pairwise comparison of pain scores in Group I and Group II patients by the Mann-Whitney U-test at different time zones revealed the results to be statistically significant for all pairs except when the findings were compared between 1 month and 3 months after the procedure in Group II patients. Also, significant recovery was observed in both Group I and II patients during healing when assessed preoperatively to 1 month and then 3 months after the procedure with the results being statistically highly significant in case of the variations observed in relation to the neurosensory deficit observed at different time zones for both Group I and II patients ( p = 0.0001). Conclusion Based on the results obtained, it can be concluded that 3D miniplate-led osteosynthesis was found comparable to the osteosynthesis accomplished using reconstruction plates during fixation of unfavorable body/parasymphysis fractures of mandible in study, providing optimal stability, while satisfactorily meeting the biomechanical requirements for occlusal loading, and an early return to normal function.