Screw Design Research Articles

Single-screw extrusion performance for LLDPE resin as a function of compression ratio

High-quality polyethylene film and sheet must be free of solid polymer fragments and degraded resin. Moreover, the products must be produced at high rates to minimize conversion costs. Thus, the extruder must produce a homogenous extrudate at the proper discharge temperature and pressure. The screw design and process operating parameters are key. A key screw design parameter is the compression ratio. This paper experimentally studies how the compression ratio affects a linear low-density polyethylene (LLDPE) resin extrusion process. A 2.8 compression ratio screw was optimal for LLDPE resin. Significant solid polymer fragments were observed in the extrudate for 2.8 to 3.6 compression ratio screws at 110 rpm and higher. For 2.0 and 2.4 compression ratio screws at less than 50 rpm, the internal pressures in the extruder were relatively low. At screw speeds 50 rpm and higher, the specific rates for all screws were higher than the calculated specific rotational rate, creating negative axial pressure gradients in the metering sections.

A novel pedicle screw design to maximize screw-bone interface strength using finite element analysis and design of experiment techniques.

Basic study. This study aimed to utilize finite element (FE) analysis and design of experiment (DoE) techniques to propose and optimize a novel pedicle screw design and compare its pull-out force with that of a control device. Pedicle screw-based fixation is the gold-standard treatment for spine diseases, particularly in fusion procedures. However, pedicle screw loosening and breakage still occur in osteoporotic and non-osteoporotic patients. This research investigates screw design modifications to enhance screw-bone interface strength and reduce the likelihood of loosening. We conceptualized a novel pedicle screw considering vertebral bone morphology and strength differences. A validated FE model was developed and used in conjunction with DoE to determine the screw՚s optimum geometrical parameters. The FE model was validated through simulation and laboratory experiments using the control device. The optimized thread profiles for cortical bone and cancellous bone were determined, with pull-out force as the primary factor for screw design evaluation. FE analysis results for the control device closely matched experimental results, with less than 5% difference. The chosen unique pitch/depth ratio showed maximum pull-out force for cortical bone, while DoE enabled the optimization of design parameters for cancellous bone. The optimized pedicle screw exhibited a 15% increase in pull-out force compared to the control device. The study proposes a novel pedicle screw design with better pull-out strength than the control device. Combining FE analysis with DoE is an effective approach for screw design optimization, reducing the need for extensive prototyping tests. A two-variable analysis suffices for optimizing cortical bone design parameters, while a multi-variable analysis is more effective for optimizing cancellous bone design parameters.

Exploring cortical trajectory of the lumbar vertebrae: a morphometric study in dry skeletons: a retrospective study in Thailand.

Retrospective cohort study. This study aimed to explore the morphometry of the Thai lumbar vertebrae. The cortical bone trajectory (CBT) is a novel approach for vertebral screw fixation aimed at addressing spinal instability associated with spinal disorders. The morphometry of the lumbar vertebrae is crucial in tailoring screw design for each CBT application, given the significant variations in optimal screw sizes, lengths, and angles among populations. A total of 300 dried lumbar columns were used to measure the pedicle height (PH) and width (PW), length for cortical bone trajectory (LCT), cephalad screw angle (CSA), axial cortical bone trajectory angle (ACA), and possible cortical zones for the CBT. The following average values were calculated: PH in L1, 15.09±1.44 mm; PW in L5, 16.96±2.42 mm; LCT in L3, 35.75±2.61 mm; CSA in L1, 20.85°±2.30°; and ACA in L5, 21.83°±2.49°. Women generally had shorter PH and PW than men, with significant differences across lumbar levels. The LCT was significantly shorter in women and was notably different between the left and right sides. The CSA and ACA varied significantly between sexes and sides, with specific lumbar levels showing wider angles in one sex over the other. The most common cortical zones for screw tips were Z3 and Z10, with high incidences across all lumbar levels. This study presents detailed lumbar vertebral morphometry data specific to the Thai population. The results are essential for CBT application in screw fixation procedures. This information will contribute to the production of optimally designed screws for Thai patients in the future.

Influence of Twin Screw Extrusion Conditions on MWCNT Length and Dispersion and Resulting Electrical and Mechanical Properties of Polycarbonate Composites

The processing conditions were varied during the production of polycarbonate-based composites with the multiwalled carbon nanotubes (MWCNTs) Baytubes® C150 P (Bayer MaterialScience AG, Leverkusen, Germany), by melt mixing with an extruder on a laboratory scale. These included the screw design, rotation speed, throughput, feeding position and MWCNT content. Particular attention was paid to the shortening of the MWCNT length as a function of the conditions mentioned. It was found that there is a correlation between the applied specific mechanical energy (SME) during the melt mixing process and MWCNT dispersion, which was quantified by the agglomerate area ratio of the non-dispersed nanotubes based on optical microscopic analysis. The higher the SME value, the lower this ratio, which indicates better dispersion. Above an SME value of about 0.4 kWh/kg, no further improvement in dispersion was achieved. The MWCNT length, as measured by the quantitative analysis of TEM images of the MWCNTs dissolved from the composites, decreased with the SME value down to values of 44% of the original MWCNT length. At a constant loading of 3 wt.%, the tensile strength and tensile modulus were almost independent of the SME, while the elongation at break and notched impact strength showed an increasing trend. The variation in the feeding position showed that feeding the MWCNTs into a side feeder led to slightly better electrical and mechanical properties for both types of MWCNTs studied (Baytubes® C150 P and Nanocyl™ NC7000 (Nanocyl S.A., Sambreville, Belgium)). However, feeding into the hopper led to better CNT dispersion with Baytubes® C150 P, while this was the case with Nanocyl™ NC7000 when feeding into the side feeder. The screw profile had an influence on the dispersion, the MWCNT length and the electrical resistance, but only to a small extent. Distributive screws led to a greater shortening of the MWCNT length than dispersive screws. By varying the MWCNT content, it was shown that a greater MWCNT shortening occurred at higher loadings. Two-stage masterbatch dilution leads to stronger shortening than composite production with direct MWCNT incorporation.

Mixing screw design and high density polyethylene toughening modification for recycled polypropylene based on screw 3D printing

AbstractThe recycling of waste plastics primarily involves physical modification and the addition of modifiers, often utilizing equipment such as twin‐screw extruders for miscible modification. Considering the widespread use of single‐screw 3D printing, improving the mixing efficiency of the single‐screw is crucial to achieve a “one‐stop” recycling modification that is suitable for 3D printing. This paper introduces a 3D printer equipped with a mixing screw (MS) and compares it with a conventional screw (CS). We conduct numerical simulations to investigate the pressure build‐up capacity, velocity streamline distribution, and the mixing effect of the MS. The mechanical properties, thermal characteristics, and molecular orientation of the recycled Polypropylene (rPP) and high density polyethylene (HDPE) mixture are investigated through experiments. The results show that the MS provides more effective elongational flows compared to the CS by breaking down the reinforcing materials into smaller particles. Additionally, toughening and modification experiments are performed on rPP and HDPE. The composites treated with the MS showed improved elongation at break (increased by ~111%), a stable melt crystallization temperature, and an enhanced mixing effect. This study on single‐screw 3D printers lays the groundwork for streamlining the plastic recycling process and increasing the reuse rate of recycled plastics.

Seeded granulation process in twin-screw granulators: A DEM approach

Twin-screw granulation is a promising continuous manufacturing technique for producing granules with tailored properties. This study investigates the impact of screw configuration and speed on seeded granule formation using discrete element method (DEM) simulations. The aim is to identify optimal screw designs and operating conditions that yield desirable granule characteristics, such as high coordination, fine particle coverage, and throughput. DEM simulations were performed using Altair's EDEM software, employing Hertz-Mindlin and JKR contact models to capture particle-particle interactions and binder liquid effects. Five screw configurations (C1, C2, C3, C4, and CI) with varying conveying zone lengths and kneading elements were investigated, and screw speed was varied from 300 to 800 RPM. The Results show that screw configuration plays a crucial role in determining seeded granule characteristics. Increasing screw speed had a detrimental effect on granule properties, with lower speeds of 300 RPM yielding the granules with the greatest coordination number with the highest fine coverage. The study highlights the complex interplay between screw configuration, conveying zone length, kneading elements, and residence time in determining granule properties. Recommendations are provided for selecting suitable screw configurations and operating conditions for specific applications. Further research is suggested to investigate granule size distribution and morphology at different liquid properties screw speeds, and liquid-to-solid ratios.

Impact of screw tip design on screw anchorage: mechanical testing and numerical simulation

BackgroundScrew loosening is a commonly reported issue following spinal screw fixation and can lead to various complications. The initial cause of screw loosening is biomechanical deterioration. Previous studies have demonstrated that modifications in screw design can impact the local biomechanical environment, specifically the stress distribution on bone-screw interfaces. There are several different designs of screw tips available for clinically used pedicle screws; however, it remains unclear whether these variations affect the local stress distribution and subsequent screw anchorage ability.MethodsThis study conducted comprehensive biomechanical research using polyurethane foam mechanical tests and corresponding numerical simulations to investigate this topic. Models of pedicle screw-fixed osteoporotic polyurethane foam were created with two different clinically used screw tip designs (flat and steep) featuring varying tip lengths, taper angles, and diameters, as well as identical flank overlap areas and thread designs. The anchorage ability of the different models was assessed through toggle and pull-out test. Additionally, numerical mechanical models were utilized to compute the stress distributions at the screw and bone-screw interfaces in the different models.ResultsMechanical tests revealed superior anchorage ability in models utilizing flat-tipped screws. Furthermore, numerical modeling indicated improved anchorage ability and reduced stress concentration tendency in these models.ConclusionChanges in screw tip design can significantly impact the biomechanical anchoring capability of screws. Specifically, flatter tip pedicle screws may mitigate the risk of screw loosening by alleviating stress concentration on bone-screw interfaces.

CT Anatomical Analysis of C4 Pedicle and Lateral Mass in Children Aged 0-14 in Southern China.

The C4 is the transition point between the upper and lower cervical vertebrae and plays a pivotal role in the middle of the cervical spine. Currently, there are limited reports on large-scale sample studies regarding C4 anatomy in children, and a scarcity of experience exists in pediatric cervical spine surgery. The current study addresses the dearth of anatomical measurements of the C4 vertebral arch and lateral mass in a substantial sample of children. This study aims to measure the imaging anatomy of the C4 vertebral arch and lateral mass in children under 14 years of age across various age groups, investigate the growth and development of these structures. We measured 12 indicators, including the size (D1, D2, D3, D4, D5, D6, D7, and D8) and angle (A, C, D, and E) of the C4 vertebral arch and lateral mass, in 513 children who underwent cervical CT examinations at our hospital. We employed the aggregate function for statistical analysis, conducted t-tests for difference statistics, and utilized the least squares method for regression analysis. Overall, as age increased, there was a gradual increase in the size of the vertebral arch and lateral mass. Additionally, the medial inclination angle of the vertebral arch decreased, and the lateral mass flattened gradually. The rate of change decreased gradually with age. The mean value of D1 increased from 2.31 mm to 3.88 mm, of D2 from 16.75 mm to 29.2 mm, of D3 from 2.21 mm to 4.92 mm, and of D4 from 7.34 mm to 11.84 mm. Meanwhile, the mean value of D5 increased from 5.2 mm to 9.71 mm, of D6 from 10.19 mm to 16.16 mm, of D7 from 2.53 mm to 5.67 mm, and of D8 from 6.11 mm to 11.45 mm. Angle A ranged from 49.12° to 54.97°, angle C from 15.28° to 19.83°, angle D from 39.91° to 53.7°, and angle E from 18.63° to 28.08°. Prior to cervical spine surgery in children, meticulous CT imaging anatomical measurements is essential. The imaging data serves as a reference for posterior C4 internal fixation, aids in designing posterior cervical screws for pediatric patients, and offer morphological anatomical references for posterior cervical spine surgery and screw design in pediatric patients.

Enhancing dynamic mixing and heat transfer of polymer by inducing ductile flow applying field synergy principle

An innovative and effective approach for screw design and optimization has been proposed, derived from multi-field synergy to address a growing challenge affected by the inadequate mixing and thermal management in plasticizing process of extrusion or injection. Dimensionless field synergy equations for incompressible non-Newtonian viscous polymers were established, and subsequently, two new types of screw structures—field synergy torsion element (FST) and field synergy elongation element (FSE)—were designed, fabricated, and validated through both simulation and experiment. Spiral and elongational flows were established in the newly designed screws owing to their unique structures of torsion channel and convergent channel, promoting the shear and stretch ductile deformations of polymer melt, documented to be a meaningful progress on flow patterns generated by conventional screw. A comparative investigation in this work of the newly designed screw with a conventional one showed that the newly proposed screws equipped with FSTs or FSEs performed better mixing and improved heat transfer and thermal uniformity. Multi-field synergy analysis revealed that the spiral and elongational flow enhanced the radial convection, improved the dependence of velocity and velocity gradient fields to facilitate melt stretching deformation as well as the dependence of velocity and temperature gradient fields to achieve heat transfer enhancement.

Convolutional neural network for assisting accuracy of personalized clavicle bone implant designs

<span lang="EN-US">The clavicle is a long bone that tends to be frequently fractured in the midshaft region. The plate and screw fixing method is mainly applied to address this issue. This study aims to construct a clavicle bone implant design with a consideration to achieve a high accuracy and high-quality surface between the plate and the clavicle surface. The computational tomography scanning (CT-scan) image series data were processed using a convolutional neural network (CNN) to classify the clavicle image. The CNN outcomes were gathered as three-dimensional (3D) volume data of clavicle bone. This 3D model was then proposed for the plate design. The CNN testing results of 97.4% for the image clavicle bones classification, whereas the prints of the 3D model from clavicle bone and its plate and screw design reveal compatibility between the bone surface and the plate surface. Overall, the CNN application to the series of CT images could ease the classification of clavicle bone images that would precisely construct the 3D model of clavicle bone and its suitable clavicle bone plate design. This study could contribute as a guideline for other bone plate areas that need to fit the patient’s bone geometry.</span>

Influence of Screw Design and Process Parameters on the Product Quality of PEO:LiTFSI Solid Electrolytes Using Solvent-Free Melt Extrusion

All-solid-state battery (ASSB) technology is a new energy system that reduces the safety concerns and improves the battery performance of conventional lithium-ion batteries (LIB). The increasing demand for such new energy systems makes the transition from laboratory scale production of ASSB components to larger scale essential. Therefore, this study investigates the dry extrusion of poly(ethylene oxide):lithium bis (trifluoromethylsulfonyl)imide (PEO:LiTFSI) all-solid-state electrolytes at a ratio of 20:1 (EO:Li). We investigated the influence of different extruder setups on the product quality. For this purpose, different screw designs consisting of conveying, kneading and mixing elements are evaluated. To do so, a completely dry and solvent-free production of PEO:LiTFSI electrolytes using a co-rotating, intermeshing, twin-screw extruder under an inert condition was successfully carried out. The experiments showed that the screw design consisting of kneading elements gives the best results in terms of process stability and homogeneous mixing of the electrolyte components. Electrochemical impedance spectroscopy was used to determine the lithium-ion conductivity. All electrolytes produced had an ionic conductivity (σionic) of (1.1–1.8) × 10−4 S cm−1 at 80 °C.

CEPHALOMEDULLARY NAILING FOR SUBTROCHANTERIC FEMORAL SHAFT FRACTURES: A COMPARISON OF SINGLE LAG SCREW DEVICE WITH AN INTERCALATED DUAL SCREW DEVICE

Subtrochanteric femoral fractures are a subset of hip fractures generally treated with cephalomedullary nail fixation\[1\]. Single lag screw devices are most commonly-used, but integrated dual screw constructs have become increasingly popular\[2,3\]. The aim of this study was to compare outcomes of fixation of subtrochanteric femoral fractures using a single lag screw (Gamma3 nail, GN) with a dual screw device (InterTAN nail, IN). The primary outcome was mechanical failure, defined as lag screw cut-out, back-out, nail breakage or peri-implant fracture.Consecutive adult patients (18yrs) with subtrochanteric femoral fracture treated in a single centre were retrospectively identified using electronic records. Patients that underwent surgical fixation using either a long GN (2010–2017) or IN (2017–2022) were included. Medical records and radiographs were reviewed to identify complications of fixation. Cox regression analysis was used to determine the risk of mechanical failure and secondary outcomes by implant design. Multivariable regression models were used to identify predictors of mechanical failure.The study included 622 patients, 354 in the GN group (median age 82yrs, 72% female) and 268 in the IN group (median age 82yrs, 69% female). The risk of any mechanical failure was increased two-fold in the GN group (HR 2.44 \[95%CI 1.13 to 5.26\]; _p=0.024_). Mechanical failure comprising screw cut-out (_p=0.032_), back-out (_p=0.032_) and nail breakage (_p=0.26_) was only observed in the GN group. Technical predictors of failure included varus >5° for cut-out (OR 19.98 \[2.06 to 193.88\]; _p=0.01_), TAD;25mm for back-out (8.96 \[1.36 to 58.86\]; p=0.022) and shortening 1cm for peri-implant fracture (7.81 \[2.92 to 20.91\]; _p=<0.001_).Our results demonstrate that an intercalated screw construct is associated with a lower risk of mechanical failure compared with the a single lag screw device. Intercalated screw designs may reduce the risk of mechanical complications for patients with subtrochanteric femoral fractures.

ДОСЛІДЖЕННЯ ДЕФОРМАЦІЇ ВОЛОКОН ЕЛАСТИЧНИХ ЩІТКОПОДІБНИХ ШНЕКІВ ПРИ ТРАНСПОРТУВАННІ ЗЕРНОВОГО МАТЕРІАЛУ

A new design of an elastic brush-like screw for grain material transportation and mixing by screw conveyors with a lower degree of damage to some particles of the material has been presented in the paper under discussion. The theoretical calculation of the fiber displacement value of an elastic brush-like screw has been carried out on the basis of the deformation analysis of an idealized system with elastic elements. A differential equation of the mean line of deformation of several fibers of an elastic brush-like screw located in the same plane perpendicular to the distributed loading during grain material transportation has been derived. The solution of the differential equation was obtained by the numeric method and on its basis the curves of the middle line of deformed fibers of an elastic brush-like screw for different values of its structural parameters. The results of the experimental study of the maximum deformation value of the elastic fibers of a brush-like screw have been presented.

Continuous Anode Slurry Production in Twin-Screw Extruders: Effects of the Process Setup on the Dispersion

Screw design in the extrusion process has an important effect on the distribution of material through the extruder, resulting in partially filled sections in the processing zone. Accordingly, the local accumulation of material in the extruder leads to variations in material strain conditions and also influences the local residence time of the material in a given screw section. This work evaluates particle dispersion in anode slurry considering three different screw arrangements. The particle size distribution is considered as a quality parameter representing the microstructure of the battery slurry components and their distribution. Numerical simulation of the material flow behavior through a laboratory extruder was performed to investigate the filling ratios and resulting shear rates for different screw designs and process conditions. The importance of process parameters and a suitable screw configuration to achieve specific particle sizes in battery slurry is discussed.

Improved design of self-tapping screw (STS) for Korean larch and red pine cross laminated timber (CLT)

In this study, the finite element method (FEM) was used to determine the effect of the optimal angle of the thread and double thread application among self-tapping screw (STS) design information on the improvement of the withdrawal capacity of the connection. It was modeled by reflecting the design information of an Italian STS distributed in the domestic wooden building market, and the stress distribution of the connections was compared according to the change in the thread angle. A cross laminated timber (CLT) composed of five layers was modeled as a member. The STS modeling was centered on the threaded area, and two threaded angles were applied: 90° and 95°. Additionally, the stress changes were compared when double threads located in the middle of the thread pitch in the screw pitch were applied to improve the withdrawal capacity of the connection. The domestic STSs were manufactured using four materials and two shapes. The finite element analysis and strength performance tests of the STS types indicated that the material properties, angle of the screw thread, and shape of the screw thread affect the Korean CLT withdrawal capacity.

Preparation of Starch Coconut Fatty Acid Inclusion Complexes by Twin‐Screw Extrusion

AbstractStarch‐guest molecule amylose inclusion complexes (AIC) are of interest to industry as a means to encapsulate and deliver compounds. Coconut fatty acids (CFA) consist predominantly of medium chain fatty acids having useful food and nonfood applications. This article describes the formation of high amylose corn (HAC)‐ or waxy corn starch (WC)‐CFA AIC containing 0%, 2%, 7.5%, and 15% CFA using a continuous thermomechanical extrusion process at 20% feed moisture and a twin‐screw extruder with a unique screw design. The extrusion conditions completely destructure both the HAC and waxy starch granules and the resulting materials are evaluated using SEM, XRD, FT‐IR, FTIR‐m, and TGA. The HAC‐CFA materials are shown to contain AIC having 61 V type helical structure between amylose and the CFA that are confirmed by XRD and IR spectral analysis. By TGA, extruded HAC materials containing 15% CFA are shown to have excess CFA present in addition to formed AIC. In contrast, the WC is shown not to form AIC with the CFA and only trap the CFA within the starch matrix. The understanding gained from this study is helpful to design the processing of starch‐based biopolymers to prepare AIC having improved functional properties for potential commercial applications.

Establishing finite element model credibility of a pedicle screw system under compression-bending: An end-to-end example of the ASME V&V 40 standard

Computational modeling and simulation (CM&S) is a key tool in medical device design, development, and regulatory approval. For example, finite element analysis (FEA) is widely used to understand the mechanical integrity and durability of orthopaedic implants. The ASME V&V 40 standard and supporting FDA guidance provide a framework for establishing model credibility, enabling deeper reliance on CM&S throughout the total product lifecycle. Examples of how to apply the principles outlined in the ASME V&V 40 standard are important to facilitating greater adoption by the medical device community, but few published examples are available that demonstrate best practices. Therefore, this paper outlines an end-to-end (E2E) example of the ASME V&V 40 standard applied to an orthopaedic implant. The objective of this study was to illustrate how to establish the credibility of a computational model intended for use as part of regulatory evaluation. In particular, this study focused on whether a design change to a spinal pedicle screw construct (specifically, the addition of a cannulation to an existing non-cannulated pedicle screw) would compromise the rod-screw construct mechanical performance. This question of interest (?OI) was addressed by establishing model credibility requirements according to the ASME V&V 40 standard. Experimental testing to support model validation was performed using spinal rods and non-cannulated pedicle screw constructs made with medical grade titanium (Ti-6Al-4V ELI). FEA replicating the experimental tests was performed by three independent modelers and validated through comparisons of common mechanical properties such as stiffness and yield force. The validated model was then used to simulate F1717 compression-bending testing on the new cannulated pedicle screw design to answer the ?OI, without performing any additional experimental testing. This E2E example provides a realistic scenario for the application of the ASME V&V 40 standard to orthopedic medical device applications.

A magnesium screw with optimized geometry exhibits improved corrosion resistance and favors bone fracture healing

Stress-induced corrosion impairs the mechanical integrity of magnesium (Mg) and its alloys as potential orthopedic implants. Although there has been extensive work reporting the effects of stress on Mg corrosion in vitro, the geometric design principles of the Mg-based orthopedic devices still remain largely unknown. In this work, a numerical simulation model mimicking fractured bone fixation and surgical animal models were applied to investigate the effects of the geometric design of Mg screws on the stress distribution and the stress-induced degradation behavior. Finite element (FE) analysis was used for calculation of stress concentrations around the Mg screws, with different thread type, thread pitch, and thread width. Afterward, the Mg screws of the pre-optimization and post-optimization groups exhibiting the highest and lowest stress concentrations, respectively, were implanted in the fractured distal femora and back subcutaneous tissue of rabbits. Encouragingly, there was a significant difference between the pre-optimization and the post-optimization groups in the degradation rate of the stressed screw parts located around the fracture line. Interestingly, there was no significant difference between the two groups in the degradation rate of the non-stressed screw parts. Consistently, the Mg screw post-optimization exhibited a significantly lower degradation rate than that pre-optimization in the back subcutaneous implantation model, which generated stress in the whole screw body. The alteration in geometric design did not affect the corrosion rate of the Mg screws in an immersion test without load applied. Importantly, an accelerated new bone formation with less fibrous encapsulation around the screws was observed in the Mg group post-optimization relative to the Mg group pre-optimization and the poly (lactic acid) group. Geometry optimization may be a promising strategy to reduce stress-induced corrosion in Mg-based orthopedic devices. Statement of significanceStress concentrations influence corrosion characteristics of magnesium (Mg)-based implants. The geometric design parameters, including thread type, thread pitch, and thread width of the Mg screws, were optimized through finite element analysis to reduce stress concentrations in a fractured model. The Mg screws with triangular thread type, 2.25 mm pitch, and 0.3 mm thread width, exhibiting the lowest maximum von Mises stress, showed a significant decrease in the volume loss relative to the Mg screws pre-optimization. Compared with the Mg screw pre-optimization and the poly(lactic acid) screw, the Mg screw post-optimization favored new bone formation while inhibiting fibrous encapsulation. Collectively, optimization in the geometric design is a promising approach to reduce stress-induced corrosion in Mg-based implants.

Design of a new detachable pedicle screw based on medical optical imaging inspection to improve osteoporosis and enhance vertebral body revision effect

Osteoporosis is a common bone disease that often leads to difficulty in vertebrae revision. Traditional pedicle screws are often complicated to operate and have poor visibility during implantation. A new detachable pedicle screw is needed to improve the revision effect. The aim of this study was to design a new detachable pedicle screw based on medical optical imaging to improve the outcome of vertebral revision in osteoporosis, and to improve operational feasibility and visibility. In this study, the parameters related to the degree of osteoporosis were obtained by optical imaging detection of the osteoporotic vertebral body. Then a new detachable pedicle screw was designed according to the test results to improve the effect of vertebral body revision. By preparing and optimizing the material and structure of the screw, it is ensured that it has sufficient mechanical strength and stability. Finally, the visibility and operability of the improved screw during implantation were verified by medical optical imaging. Compared with traditional screws, the new detachable pedicle screw can improve the vertebral body revision in the case of osteoporosis. The optical imaging test results show that the new screw has good visibility and maneuverability, providing more accurate guidance and positioning for the vertebral body revision operation.

CEPHALOMEDULLARY NAILING FOR SUBTROCHANTERIC FEMORAL SHAFT FRACTURES: A COMPARISON OF SINGLE LAG SCREW WITH A DUAL LAG SCREW DEVICE

This study compares outcomes of fixation of subtrochanteric femoral fractures using a single lag screw (Gamma3 nail, GN) with a dual lag screw device (InterTAN nail, IN). The primary outcome was mechanical failure, defined as lag screw cut-out, back-out, nail breakage or peri-implant fracture. Technical factors associated with mechanical failure were also identified.All adult patients (>18yrs) with a subtrochanteric femoral fracture treated in a single centre were retrospectively identified using electronic records. Included patients underwent surgical fixation using either a long GN (2010–2017) or IN (2017–2022). Cox regression analysis was used to determine the risk of mechanical failure and technical predictors of failure.The study included 587 patients, 336 in the GN group (median age 82yrs, 73% female) and 251 in the IN group (median age 82yrs, 71% female). The IN group exhibited a higher prevalence of osteoporosis (p=0.002) and CKD□3 (p=0.007). There were no other baseline differences between groups. The risk of any mechanical failure was increased two-fold in the GN group (HR 2.51, p=0.020). Mechanical failure comprising screw cut-out (p=0.040), back-out (p=0.040) and nail breakage (p=0.51) was only observed in the GN group. The risk of peri-implant fracture was similar between the groups (HR 1.10, p=0.84). Technical predictors of mechanical included varus >5° for cut-out (HR 15.61, p=0.016), TAD>25mm for back-out (HR 9.41, p=0.020) and shortening >1cm for peri-implant fracture (HR 6.50, p=<0.001).Dual lag screw designs may reduce the risk of mechanical complications for patients with subtrochanteric femoral fractures.