Number Of Screws Research Articles

Experimental study of flexural behavior of glulam Douglas Fir beams spliced with engineered bamboo cover plates and inclined self-tapping screws

Due to the limitation of transportation and installation, long-span timber structural components need to be extended through multiple spliced joints. Among the common spliced joints, spliced beam joints with self-tapping screws have the advantages of low cross-section weakening, beautiful appearance, and convenient construction. However, the beam joints spliced by self-tapping screws have limitations in terms of bearing capacity and stiffness. To overcome these limitations, this paper proposes inclined self-tapping screw-engineered bamboo joints. In this novel joint, the high-strength engineered bamboo connection plates are used to improve the mechanical properties of spliced glulam beams. A total of thirteen glulam beams were designed. The effects of the layout and number of self-tapping screws, types of connection plates, and spliced gaps on the flexural performance of novel glulam beams were experimentally investigated through four-point bending tests. The results show that the mechanical properties of the spliced beam with parallel self-tapping screws are better than those with staggered self-tapping screws. The bending capacity of the glulam beams spliced with bamboo scrimber plates arranged in parallel increases with the increase of the number of self-tapping screws. The average bending capacity and stiffness can reach 97.3 % and 93.3 % of the intact beams, respectively. The bending capacity and stiffness of glulam beams with the same number of self-tapping screws arranged in parallel and spliced with plybamboo are lower than those of glulam beams spliced with bamboo scrimber. The gap between the spliced cross-sections of glulam beams significantly reduces the flexural mechanical properties of spliced beams, especially the stiffness.

Four-screw compression plate fixation for diaphyseal humerus fractures.

While many humeral shaft fractures can be successfully treated with nonoperative management, compression plating techniques using at least three or four screws on either side of the fracture are the current gold standard. We hypothesized that a less rigid construct using compression with only two screws on either side of the fracture can provide adequate strength for uneventful fracture union. This is a retrospective review of all the patients who underwent open reduction and compression plate fixation for acute diaphyseal humerus fractures (ADHFs) at an academic Level-1 urban trauma center between 2018 and 2023. Patients treated with compression plating using only two screws and three or four plate-holes on either side of the fracture (Group 1) were matched one-to-one with patients treated using the conventional number of screws (three or more on either side of the fracture - Group 2). The incidence of nonunion/malunion, infection, and implant failure was compared among the two groups. There were eleven matched patients in both groups. The nonunion, infection complications, and hardware failure rates were 0% and 9.1% for the control group (Group 2) and four-screw group (Group 1) respectively. This difference was not statistically significant (p = 1.00). Although convention dictates the use of six or more bicortical screws (at least three bicortical screws on each side of the fracture), four-screw bicortical fixation may be a feasible option for ADHFs treated with large fragment compression plating techniques.

Analysis of Out-of-Plane Displacements of a Light Steel Keel Fireproof Exterior Wall and Its Connection with the Steel Frame

Light steel keel fireproof exterior walls are one of the new composite walls that have been widely used in recent years. This paper analyzes the factors affecting the displacements of the connectors and wall panels and modifies the corresponding displacement model. ABAQUS was used to establish the simulation analysis of the L-shaped and special-shaped steel angle component, and the results were compared with the experimental model to verify the rationality. The effect of vertical keel spacing and layout, the number of special-shaped steel angles, the L-shaped steel angle thickness, and the number of self-tapping screws for L-shaped steel angles to steel beams were explored based on the validated finite element model. The calculation model was modified based on the results of the simulation. The results showed that the simulation results fit well with the experimental results, which verified the reliability of the finite element model. The number of connectors and the number of self-tapping screws are the main factors affecting the special-shaped and L-shaped steel angle components, respectively. By modifying the rotation constraint factor of the L-shaped steel angle and adding a discount factor for the wall panel, the accuracy of the associated displacement calculation model could be improved.

Feasibility and safety report on robotic assistance for cervical pedicle screw fixation: a cadaveric study

This cadaveric study aimed to evaluate the safety and usability of a novel robotic system for posterior cervical pedicle screw fixation. Three human cadaveric specimens and C2-T3 were included. Freshly frozen human cadaver specimens were prepared and subjected to robot-assisted posterior cervical pedicle screw fixation using the robotic system. The accuracy of screw placement, breach rate, and critical structure violations were evaluated. The results were statistically compared with those of previous studies that used different robotic systems for cervical pedicle screw fixation. The robotic system demonstrated a high accuracy rate in screw placement. A significant number of screws were placed within predetermined safe zones. The total entry offset was 1.08 ± 0.83 mm, the target offset was 1.86 ± 0.50 mm, and the angle offset was 2.14 ± 0.77°. Accuracy rates comparable with those of previous studies using different robotic systems were achieved. The system was also feasible, allowing precise navigation and real-time feedback during the procedure. This cadaveric study validated the safety and usability of the novel robotic system for posterior cervical pedicle screw fixation. The system exhibited high precision in screw placement, and the results support the extension of the indications for robot-assisted pedicle screw fixation from the lumbar spine to the cervical spine.

Comparison of No Tap (two-step) and tapping robotic assisted cortical bone trajectory screw insertion.

Workflow for cortical bone trajectory (CBT) screws includes tapping line-to-line or under tapping by 1mm. We describe a non-tapping, two-step workflow for CBT screw placement, and compare the safety profile and time savings to the Tap (three-step) workflow. Patients undergoing robotic assisted 1-3 level posterior fusion with CBT screws for degenerative conditions were identified and separated into either a No-Tap or Tap workflow. Number of total screws, screw-related complications, estimated blood loss, operative time, robotic time, and return to the operating room were collected and analyzed. There were 91 cases (458 screws) in the No-Tap and 88 cases (466 screws) in the Tap groups, with no difference in demographics, revision status, ASA grade, approach, number of levels fused or diagnosis between cohorts. Total robotic time was lower in the No-Tap (26.7min) versus the Tap group (30.3min, p = 0.053). There was no difference in the number of malpositioned screws identified intraoperatively (10 vs 6, p = 0.427), screws converted to freehand (3 vs 3, p = 0.699), or screws abandoned (3 vs 2, p = 1.000). No pedicle/pars fracture or fixation failure was seen in the No-Tap cohort and one in the Tap cohort (p = 1.00). No patients in either cohort were returned to OR for malpositioned screws. This study showed that the No-Tap screw insertion workflow for robot-assisted CBT reduces robotic time without increasing complications.

Impact of bone density and integrated screw configuration on standalone anterior lumbar interbody construct strength

BackgroundIn anterior lumbar interbody fusion (ALIF), the use of integrated screws is attractive to surgeons because of the ease of implantation and no additional profile. However, the number and length of screws necessary for safe and stable implantation in various bone densities is not yet fully understood. The current study aims to determine how important both length and number of screws are for stability of ALIFs. MethodsThree bone models with densities of 10, 15, and 20 pounds per cubic foot (PCF) were chosen as surrogates. These were instrumented using the Z-Link lumbar interbody system with either 2, 3, or 4 integrated 4.5 × 20 mm screws or 4.5 × 25 mm screws (Zavation, LLC, Flowood, MS). The bone surrogates were tested with loading conditions resulting in spine extension to measure construct stiffness and peak force. ResultsThe failure load of the construct was influenced by the length of screws (p=.01) and density of the bone surrogate (p<.01). There was no difference in failure load between using 2 screws and 3 screws (p=.32) or when using four 20 mm screws versus three 25 mm screws (p=.295). ConclusionIn our study, both bone density and length of screws significantly affected the construct's load to failure. In certain cases where a greater number of screws are unable to be implanted, the same stability can potentially be conferred with use of longer screws. Future clinical studies should be performed to test these biomechanical results.

Some aspects of biomechanics of the operated thoracolumbar junction following two-level corpectomy

Traumatic spinal injuries pose a significant medico-social challenge, with about 60% of all spine fractures occurring at the thoracolumbar junction. Optimizing care for these patients remains a critical issue, despite the development of numerous surgical and conservative treatment methods, with outcomes still far from ideal. A key factor contributing to the consistently high rate of unsuccessful surgical interventions, which lead to stabilization failures in both the early and late postoperative periods, is the disregard of the biomechanical characteristics of the thoracolumbar junction area. Clinical protocols often regulate intervention methods based on the degree and nature of damage to the thoracolumbar spine as a whole. Enhancing the reliability of fixation, while maintaining the number of transpedicular screws, can be significantly achieved by using cross-links and adjusting screw length. The purpose of our study was to investigate the distribution of loads on the metal construct elements and bone structures in the thoracolumbar junction after extensive decompressive-stabilizing interventions. The load was modeled with a backward tilt. A mathematical finite element model of the human thoracolumbar spine segment was developed, incorporating vertebrae Th9-Th11, L2-L5, with Th12-L1 vertebrae removed, as well as elements of the metal construct—interbody support and a transpedicular system. We modeled four variants of transpedicular fixation using both short and long screws that penetrate the anterior surface of the vertebral body, with and without the use of two cross-links. Stress parameters were monitored at 20 control points in the models. Comparative analysis of the results revealed that models including long bicortical screws and two cross-links demonstrated the best biomechanical performance when the torso was tilted backward, effectively reducing stress in critical areas and enhancing the durability and effectiveness of the fixation.

AAHKS Surgical Techniques & Technologies Award: Inferior Screw Fixation Decreases Acetabular Component Failure Following Revision Total Hip Arthroplasty

BackgroundAdjunctive screw fixation has been shown to be reliable in achieving acetabular component stability in revision total hip arthroplasty (THA). The purpose of this study was to assess the effect of inferior screw placement on acetabular component failure following revision THA. We hypothesized that inferior screw fixation would decrease acetabular failure rates. MethodsWe reviewed 250 patients who had Paprosky Type II or III defects who underwent acetabular revision between 2001 and 2021 across three institutions. Demographic factors, the number of screws, location of screw placement (superior versus inferior), use of augments and/or cup-cage constructs, Paprosky classification, and presence of discontinuity were documented. Multivariate regression was performed to identify the independent effect of inferior screw fixation on the primary outcome of aseptic rerevision of the acetabular component. ResultsAt a mean follow-up of 53.4 months (range, 12 to 261), 16 patients (6.4%) required re-revision for acetabular loosening. There were 140 patients (56.0%) who had inferior screw fixation, all of whom did not have neurovascular complications during screw placement. Patients who had inferior screws had a lower rate of acetabular rerevision than those who only had superior screw fixation (2.1 versus 11.8%, P = .0030). Multivariate regression demonstrates that inferior screw fixation decreased the likelihood of rerevision for acetabular loosening when compared to superior screw fixation alone (odds ratio: 0.1, confidence interval: 0.03 to 0.5; P = .0071). No other risk factors were identified. ConclusionsInferior screw fixation is a safe and reliable technique to reduce acetabular component failure following revision THA in cases of severe acetabular bone loss.

Determination of the ideal plate for medial femoral condyle fracture fixation: an anatomical fit and biomechanical study

BackgroundThe aim of this study is to determine the best plate to use as a substitute to fix a medial femoral condyle fracture.Materials and methodsThe first part is to measure the best fit between several anatomical plates including the Proximal Tibia Anterolateral Plate (PT AL LCP), the Proximal Tibia Medial Plate (PT M LCP), the Distal Tibia Medial Locking Plate (DT M LCP) and the Proximal Humerus (PHILOS) plate against 28 freshly embalmed cadaveric distal femurs. Measurements such as plate offset and number of screws in the condyle and shaft shall be obtained. The subsequent part is to determine the compressive force at which the plate fails. After creating an iatrogenic medial condyle fracture, the cadavers will be fixed with the two plates with the best anatomical fit and subjected to a compression force using a hydraulic press.ResultsThe PT AL LCP offered the best anatomical fit whereas the PHILOS plate offered the maximal number of screws inserted. The force required to create 2 mm of fracture displacement between the two is not statistically significant (LCP 889 N, PHILOS 947 N, p = 0.39). The PT AL LCP can withstand a larger fracture displacement than the PHILOS (LCP 24.4 mm, PHILOS 17.4 mm, p = 0.004).Discussion and conclusionBoth the PT AL LCP and the PHILOS remain good options in fixing a medial femoral condyle fracture. Between the two, we would recommend the PT AL LCP as the slightly superior option.

Flexural performance of cold-formed square tube splice joints connected by self-tapping screws

Experimental studies and numerical simulations are performed to investigate flexural performance of cold-formed square tube (CFST) splice joints connected by self-tapping screws. Seven specimens were fabricated from the external steel plate and inner sleeve using self-tapping screws and underwent variations in screw quantity. Refined finite element models were developed and calibrated using a dataset of test results from cold-formed square tube splice joints. Subsequently, an extensive parametric study was undertaken to expand the CFST splice joints data pool, covering the CFST strength, thickness, screw diameter, spacing, as well as the number of rows and columns screws. Finally, a dependable design method for the flexural bearing capacity of CFST splice joints was derived from the experimental and finite element analysis results. The conclusions are as follows: (1) The flexural performance of inner sleeve specimens surpasses that of external steel plate specimens significantly. (2) Variations in steel strength and thickness minimally impacted the flexural bearing capacity of the specimens. Alterations in screw diameter, longitudinal spacing, rows and columns notably influenced the flexural performance of the specimens. (3) A comparison revealed that the proposed design method exhibited higher accuracy and safety in calculating the flexural bearing capacity of CFST splice joints.

Lengthening in congenital posteromedial bowing of tibia: a follow-up series at skeletal maturity.

Congenital posteromedial bowing (CPMB) of tibia is a rare, usually self-resolving condition that is present at birth. The data on the long-term outcome of lengthening, choice of fixator, outcome in early and late age groups, and complications is sparse, hence the need for this study. This retrospective study included 93 patients with 94 affected legs from 1991 to 2023. The patients were categorized into early (under 10years) and late (10years or above) intervention groups. Eighteen patients with nineteen lengthening episodes who attained skeletal maturity made the basis of this study and will be discussed in detail. The outcome for the lengthening group at maturity was satisfactory, with 5.53cm of average length gained per lengthening episode, a mean LLD of 0.31cm at final follow-up, a mean age of 23.63years (range 14-38years), and an average follow-up of 12.51years (range 3-28years) post-lengthening, but the procedure was associated with difficulties like ankle stiffness, tibial valgus, pin tract infections, and fractures through regenerate. This study represents a large single-centre series on CPMB. We recommend that surgery for lengthening should be done at an older age, close to skeletal maturity, wherever possible to reduce the risk of repeat lengthening procedures. Based on our experience, we recommend the use of a circular fixator. Uniplanar distractors should have an adequate number and spread of Schanz screws in each segment to reduce the risk of valgus malalignment of distracting segments of bone.

Variables Associated With Loss of Fixation of Retrograde Rami Screws in Minimally Displaced Lateral Compression Type 1 Pelvic Ring Injuries.

To evaluate variables associated with loss of fixation of retrograde rami screws in the treatment of stress-positive minimally displaced lateral compression type 1 (LC1) injuries. Retrospective comparative study. Level 1 trauma center. Stress-positive minimally displaced (<1 cm) LC1 pelvic ring injuries treated with retrograde rami screws. Loss of fixation, defined as >5 mm of pelvic fracture displacement based on the radiographic tear-drop distance or >5 mm of implant displacement on follow-up radiographs; revision surgery for loss of fixation. Thirty-eight patients with 40 retrograde rami screws were analyzed. Median patient age was 64 years (interquartile range 42.5-73.3 years), 71.1% (n = 27/38) were female, and 52.6% (n = 20/38) of injuries were secondary to low-energy mechanisms. Loss of fixation occurred in 17.5% (n = 7/40) of screws with 10% (n = 4/40) requiring revision surgery. On univariate analysis, patients who had a loss of fixation were more likely to have greater dynamic displacement on stress radiographs (22.0 vs. 15.2 mm; median difference 5.6 mm, confidence interval [CI] -19.2 to 10.3; P = 0.04), unicortical rami screws (71.4% vs. 9.1%; proportional difference 62.3%, CI 8.8%-22.6%; P = 0.001), and partially threaded rami screws (71.4% vs. 21.2%; proportional difference 50.2%, CI 10.0%-77.6%; P = 0.01). The remaining variables had no observed association ( P ≥ 0.05) with loss of fixation, including age, sex, body mass index, energy of injury mechanism, tobacco use, American Society of Anesthesiologist score, sacral fracture type, distal rami fractures, rami comminution, number of sacral screws, fully threaded sacral screws, transsacral screws, or rami screw diameter. On multivariate analysis, only unicortical rami screws ( P = 0.01) remained associated with loss of fixation. Retrograde rami screws had a high rate of loss of fixation in minimally displaced LC1 pelvic ring injuries, and this was associated with unicortical screws. These screws should be avoided when possible. Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Experimental and theoretical investigation into flexural performance of thin-walled steel-laminated bamboo lumber truss beam

This study presents a novel truss beam called thin-walled steel-laminated bamboo lumber truss beam (SBTB). The SBTB is composed of cold-formed thin-walled steel chords and laminated bamboo lumber web members. A total of 24 SBTBs were divided into eight groups, each group containing 3 specimens, to investigate various parameters, including bamboo web member thickness and laminated direction, number of self-drilling screws, shear span ratio, and truss beam height and width. The flexural performance of SBTBs was evaluated through a four-point bending test, analyzing the failure mode, deflection, bearing capacity, and bending stiffness. The impact of different parameters on the flexural performance was thoroughly examined and discussed. In addition, a theoretical model and simplified prediction approach for the bending stiffness of SBTBs were developed. The results identified five failure modes during the flexural tests and demonstrated the linear elastic and nonlinear stages of the SBTB working process. Increasing the width and height of the beam, the number of self-drilling screws, and adopting plain pressed laminated bamboo lumber web members significantly improved the bending resistance of the composite truss beam. Notably, the theoretical model accurately predicted the stiffness of SBTBs, with a maximum discrepancy of less than 12.3 % between experimental and theoretical results.

Impact of intraoperative imaging on decision-making during spine surgery: a survey among spine surgeons using simulated intraoperative images

PurposeTo assess whether the intention to intraoperatively reposition pedicle screws differs when spine surgeons evaluate the same screws with 2D imaging or 3D imaging.MethodsIn this online survey study, 21 spine surgeons evaluated eight pedicle screws from patients who had undergone posterior spinal fixation. In a simulated intraoperative setting, surgeons had to decide if they would reposition a marked pedicle screw based on its position in the provided radiologic imaging. The eight assessed pedicle screws varied in radiologic position, including two screws positioned within the pedicle, two breaching the pedicle cortex < 2 mm, two breaching the pedicle cortex 2–4 mm, and two positioned completely outside the pedicle. Surgeons assessed each pedicle screw twice without knowing and in random order: once with a scrollable three-dimensional (3D) image and once with two oblique fluoroscopic two-dimensional (2D) images.ResultsAlmost all surgeons (19/21) intended to reposition more pedicle screws based on 3D imaging than on 2D imaging, with a mean number of pedicle screws to be repositioned of, respectively, 4.1 (± 1.3) and 2.0 (± 1.3; p < 0.001). Surgeons intended to reposition two screws placed completely outside the pedicle, one breaching 2-4mm, and one breaching < 2 mm more often based on 3D imaging.ConclusionWhen provided with 3D imaging, spine surgeons not only intend to intraoperatively reposition pedicle screws at risk of causing postoperative complications more often but also screws with acceptable positions. This study highlights the potential of intraoperative 3D imaging as well as the need for consensus on how to act on intraoperative 3D information.

Patterns of Metatarsal Explosion After New Modern Minimally Invasive Bunion Surgery. A Retrospective Review and Case Series of 16 Feet.

Introduction First metatarsal explosion is a new serious postoperative complication that occurs with new minimally invasive bunion surgery and has yet to be reported or analyzed. This retrospective study investigated associated factors. We present a classification system (3 Types), mechanism and treatment paradigm. Methods A case review was performed between January 2018 to May 2022 and we identified 16 feet (15 patients) with metatarsal explosion. We evaluated age, sex, BMI, laterality, preoperative intermetatarsal angle, medical comorbidities, screw placement, number of screws and patterns of fracture. Results The median age was 61.6 years and 80% of patients were females. Forty percent were obese. Forty percent had thyroid disorders. One patient had bilateral explosion. The metatarsal explosion distributions were Type I 50%, Type II 31% and Type III 19%. Twelve feet (75%) of metatarsal explosions occurred in a region we coin the Cortical Purchase Zone (CPZ). Forty three percent of metatarsal explosions had screws starting distal/dorsal in the metatarsal base, a region we coin the Cancellous Anchor Zone (CAZ). Metatarsal explosion distribution was not significantly associated with age, gender, laterality, preoperative intermetatarsal angle, screw placement and all medical comorbidities. Worse metatarsal explosions were more likely with two metatarsal screws (p &lt; 0.05). Treatment was non-surgical for 12 feet (75%) and open reduction internal fixation for 4 feet (25%). Conclusion Metatarsal explosion has three distinct types and we present a new classification system. Two screw fixation was more likely to have a metatarsal explosion. Etiologic observations suggest screw placement as a contributing cause. Treatment was mainly non-operative and surgery was utilized for unstable displaced explosions.

Research progress on distal interlocking screws of cephalomedullary nails in intertrochanteric fractures

To summarize the new research progress in distal interlocking screws of cephalomedullary nails for the treatment of intertrochanteric fractures. Relevant domestic and foreign literature was extensively reviewed to summarize the static/dynamic types of distal interlocking screw holes, biomechanical studies, clinical studies and application principles, effects on toggling in the cavity, and related complications of distal interlocking screws. The mode of the distal interlocking screw holes can be divided into static and dynamic. Distal interlocking screws play the role of anti-rotation, maintaining femur length, resisting compression stress, increasing torque stiffness, resisting varus stress, etc. The number of the screws directly affects the toggling of the main nail in the cavity. At present, regardless of whether long or short nails are used, distal interlocking screws are routinely inserted in clinical practice. However, using distal interlocking screws can significantly increase the duration of anesthesia and operation, increase fluoroscopy exposure time, surgical blood loss, and incision length. There is a trend of trying not to use distal interlocking screws in recent years. No significant difference is found in some studies between the effectiveness of dynamic and static interlocking for AO/Orthopaedic Trauma Association (AO/OTA) 31-A1/2 fractures. At present, the selection of the number and mode of distal interlocking screws is still controversial. When inserting distal interlocking screws, orthopedists should endeavor to minimize the occurrence of complications concerning miss shot, vascular injuries, local stress stimulation, and peri-implant fractures. Distal interlocking screws are mainly used to prevent rotation. For stable fractures with intact lateral walls, long cephalomedullary nails can be used without distal interlocking screws. For any type of intertrochanteric fractures, distal interlocking screws are required when using short cephalomedullary nails for fixation. Different interlocking modes, the number of interlocking screws, and the application prospects of absorbable interlocking screws may be future research directions.

Exceptional Cases Demand Exceptional Personalized Solutions: The Next Level in Dental Rehabilitation.

Defects and bone loss in the maxilla and mandible pose significant challenges for dental rehabilitation. This paper focuses on complex cases of bimaxillary dental rehabilitation, where traditional dental implant protocols were not feasible in at least one jaw. Four patients were examined conceptually, where conventional dental implant placement (n = 20) was combined in either the same or opposite jaw with a patient-specific subperiosteal implant (n = 5). This study evaluates aspects such as primary stability, prosthodontic restoration, complications, and soft tissue management over the observation period. None of the five patient-specific subperiosteal implants (IPS Implants® Preprosthetic; KLS-Martin Group, Tuttlingen, Germany) experienced failure or showed any loosening of screws, with the longest observation period extending to 68 months. These implants were securely fixated away from the posts, without any biomechanical restrictions on loading from the time of insertion. Planning and manufacturing, including the initial suprastructure, followed a fully digital workflow. The number of screws required for multivector fixation ranged from 13 to 22. All dental implants placed remain functional, definitive prosthodontic restoration has been performed, and no stability loss or peri-implantitis has been observed. The IPS Implants® Preprosthetic emerges as a valuable consideration when conventional implant dentistry protocols encounter limitations.

Intrinsic factors responsible for brittle versus ductile nature of refractory high-entropy alloys

Refractory high-entropy alloys (RHEAs) are of interest for ultrahigh-temperature applications. To overcome their drawbacks — low-temperature brittleness and poor creep strength at high temperatures — improved fundamental understanding is needed. Using experiments, theory, and modeling, we investigated prototypical body-centered cubic (BCC) RHEAs, TiZrHfNbTa and VNbMoTaW. The former is compressible to 77 K, whereas the latter is not below 298 K. Hexagonal close-packed (HCP) elements in TiZrHfNbTa lower its dislocation core energy, increase lattice distortion, and lower its shear modulus relative to VNbMoTaW whose elements are all BCC. Screw dislocations dominate TiZrHfNbTa plasticity, but equal numbers of edges and screws exist in VNbTaMoW. Dislocation cores are compact in VNbTaMoW and extended in TiZrHfNbTa, and different macroscopic slip planes are activated in the two RHEAs, which we attribute to the concentration of HCP elements. Our findings demonstrate how ductility and strength can be controlled through the ratio of HCP to BCC elements in RHEAs.

Biomechanical analysis of combi-hole locking compression plate during fracture healing: A numerical study of screw configuration.

Locking compression plates (LCPs) have become a widely used option for treating femur bone fractures. However, the optimal screw configuration with combi-holes remains a subject of debate. The study aims to create a time-dependent finite element (FE) model to assess the impacts of different screw configurations on LCP fixation stiffness and healing efficiency across four healing stages during a complete fracture healing process. To simulate the healing process, we integrated a time-dependent callus formation mechanism into a FE model of the LCP with combi-holes. Three screw configuration parameters, namely working length, screw number, and screw position, were investigated. Increasing the working length negatively affected axial stiffness and healing efficiency (p < 0.001), while screw number or position had no significant impact (p > 0.01). The time-dependent model displayed a moderate correlation with the conventional time-independent model for axial stiffness and healing efficiency (ρ ≥ 0.733, p ≤ 0.025). The highest healing efficiency (95.2%) was observed in screw configuration C125 during the 4-8-week period. The results provide insights into managing fractures using LCPs with combi-holes over an extended duration. Under axial compressive loading conditions, the use of the C125 screw configuration can enhance callus formation during the 4-12-week period for transverse fractures. When employing the C12345 configuration, it becomes crucial to avoid overconstraint during the 4-8-week period.

Pedicle screw placement accuracy in robot-assisted versus image-guided freehand surgery of thoraco-lumbar spine (ROBARTHRODESE): study protocol for a single-centre randomized controlled trial

BackgroundRobotic spinal surgery may result in better pedicle screw placement accuracy, and reduction in radiation exposure and length of stay, compared to freehand surgery. The purpose of this randomized controlled trial (RCT) is to compare screw placement accuracy of robot-assisted surgery with integrated 3D computer-assisted navigation versus freehand surgery with 2D fluoroscopy for arthrodesis of the thoraco-lumbar spine.MethodsThis is a single-centre evaluator-blinded RCT with a 1:1 allocation ratio. Participants (n = 300) will be randomized into two groups, robot-assisted (Mazor X Stealth Edition) versus freehand, after stratification based on the planned number of pedicle screws needed for surgery. The primary outcome is the proportion of pedicle screws placed with grade A accuracy (Gertzbein-Robbins classification) on postoperative computed tomography images. The secondary outcomes are intervention time, operation room occupancy time, length of stay, estimated blood loss, surgeon’s radiation exposure, screw fracture/loosening, superior-level facet joint violation, complication rate, reoperation rate on the same level or one level above, functional and clinical outcomes (Oswestry Disability Index, pain, Hospital Anxiety and Depression Scale, sensory and motor status) and cost-utility analysis.DiscussionThis RCT will provide insight into whether robot-assisted surgery with the newest generation spinal robot yields better pedicle screw placement accuracy than freehand surgery. Potential benefits of robot-assisted surgery include lower complication and revision rates, shorter length of stay, lower radiation exposure and reduction of economic cost of the overall care.Trial registrationClinicalTrials.gov NCT05553028. Registered on September 23, 2022