Screw Type Research Articles

Biomechanical comparison of a new undercut thread design vs the V-shape thread design for pedicle screws

BACKGROUND CONTEXTThread shape is regarded as an important factor influencing the fixation strength and osseointegration of bone screws. However, commercial pedicle screws with a V-shaped thread are prone to generating stress concentration at the bone-screw interface, thereby increasing the risk of screw loosening. Thus, modification of the pedicle-screw thread is imperative. PURPOSEThis study aimed to investigate the fixation stability of pedicle screws with the new undercut thread design in comparison to pedicle screws with a V-shaped thread. STUDY DESIGNIn vitro cadaveric biomechanical test and finite element analysis (FEA). METHODSPedicle screws with the undercut thread (characterized by a flat crest feature and a tip-facing undercut feature) were custom-manufactured, whereas those with the V-shaped thread were procured from a commercial supplier. Fixation stability was assessed by the cyclic nonpullout compressive biomechanical testing on cadaveric female osteoporotic vertebrae. The vertical displacement and rotation angle of the 2 types of pedicle screws were calculated every 100 cycles to evaluate their resistance to migration and rotation. FEA was conducted to investigate the stress distribution and bone damage at the bone-screw interface for both types of pedicle screws. RESULTSBiomechanical testing revealed that the pedicle screws with the undercut thread exhibited significantly lower vertical displacement and rotation angles than the pedicle screws with the V-shape thread (p<0.05). FEA results demonstrated a more uniform stress distribution in the bone surrounding the thread in the undercut design than in the V-shape design. Additionally, bone damage resulting from the pedicle screw was lower in the undercut design than in the V-shape design. CONCLUSIONSPedicle screws with an undercut thread are less prone to migration and rotation and thus more stable in the bone than those with a V-shape thread. CLINICAL SIGNIFICANCEThe undercut thread design may reduce the incidence of pedicle-screw loosening.

Analysis of load distribution after transpedicular stabilization of burst fractures in the thoracolumbar junction

Background. In the structure of all traumatic spine injuries, the thoracolumbar junction is predominant, accounting for over 53 % of all vertebral fractures. One of the most clinically significant types of injuries in this area are burst fractures. The purpose was to study the stress-strain state of the thoracolumbar spine model with a burst fracture of the Th12 vertebra in various transpedicular fixation options under compression load. Materials and methods. The study developed and investigated a finite element model of the thoracolumbar spine with a burst fracture of the Th12 vertebra. The burst fracture was modeled by dividing the vertebral body of the Th12 into several planes, transforming it into separate fragments. The gaps between these fragments were filled with a material that simulated the interfragmentary regenerate. Variants of transpedicular stabilization using different types of screws, mono- or bicortical, and with or without cross-links, were examined. The model was analyzed under compression load. Results. The maximum level of stress among the bone structures directly involved in fixation was registered in the L2 vertebral body. It amounted to 19.9, 15.6, 19.4, and 15.1 MPa, respectively, for models with monocortical screws without cross-links, bicortical screws without cross-links, monocortical screws with cross-links, bicortical screws with cross-links. Simultaneously, the zone of screw entry into the arch of this vertebra shows values of 10.1, 15, 10.2, and 14.3 MPa for these models, respectively. Peak loads on the metal structure elements are observed on the rods, amounting to 212.5, 159.6, 203.7, 142.8 MPa, respectively, for the considered models. Conclusions. The results of the study showed that under the influence of compression load when modeling a burst fracture of the thoracolumbar junction, the use of long screws leads to a reduction in stress levels, both in the elements of the metal structure and in the bone elements of the model, while the use of cross-links has a negligible effect.

RESEARCH ON THE APPLICATION OF ROTARY COMPRESSORS IN GAS TRANSMISSION SYSTEMS

The article provides an analysis of the operating conditions of compressors used for gas transportation in the Azerbaijani gas industry and explores ways to effectively utilize them. It discusses primarily the types, technical specifications, constructions, and application areas of rotary compressors employed in the gas industry. Additionally, information is provided about various types of rotary compressors, including rotary-vane, screw, twin-screw, and scroll compressors. Keywords: gas, vane, screw, rotor, scroll, compressor, cylinder, pressure, piston.

Comparative Analysis of Monoaxial and Polyaxial Pedicle Screws in the Surgical Correction of Adolescent Idiopathic Scoliosis.

Background: Although several biomechanical studies have been reported, few clinical studies have compared the efficacy of monoaxial and polyaxial pedicle screws in the surgical treatment of adolescent idiopathic scoliosis (AIS). This study aims to compare the radiological and clinical outcomes of mono- and polyaxial pedicle screws in the surgical treatment of AIS. Methods: A total of 46 AIS patients who underwent surgery to treat scoliosis using pedicle screw instrumentation (PSI) and rod derotation (RD) were divided into two groups according to the use of pedicle screws: the monoaxial group (n = 23) and polyaxial group (n = 23). Results: The correction rate of the main Cobb's angle was higher in the monoaxial group (70.2%) than in the polyaxial group (65.3%) (p = 0.040). No differences in the rotational correction of the apical vertebra were evident between the two groups. SRS-22 scores showed no significant differences according to the type of pedicle screws used. Conclusions: The use of polyaxial pedicle screws resulted in coronal, sagittal, and rotational correction outcomes comparable to those associated with the use of monoaxial pedicle screws for surgical treatment using PSI and RD to treat moderate cases of AIS.

Design and radiological confirmation of 3-column cortical bone trajectory in the lumbar spine.

The aim of this study was to design a novel lumbar cortical bone trajectory (CBT) penetrating the anterior, middle, and posterior vertebral area using imaging; measure the relevant parameters to find theoretical parameters and screw placement possibilities; and investigate the optimal implantation trajectory of the CBT in patients with osteoporosis. Three types of CBTs with appropriate lengths were selected to simulate screw placement using Mimics software. These CBTs were classified as the leading tip of the trajectory pointing to the posterior quarter area (original CBT [CBT-O]) and middle (novel CBT A [CBT-A]) and anterior quarter (novel CBT B [CBT-B]) of the superior endplate. The authors then measured the maximum screw diameter (MSD) and length (MSL), cephalad (CA) and lateral (LA) angles, and bone mineral density (Hounsfield unit [HU] values) of the planned novel 3-column CBT screw placements. The differences in the parameters of the novel CBTs, the percentages of successfully planned CBT screws, and the factors that influenced the successful planning of 3-column CBT screws were analyzed. Three-column CBT screws were successfully designed in all segments of the lumbar spine. The success rate of the 3-column CBT planned screws was 72.25% (83.25% for CBT-A and 61.25% for CBT-B). From the CBT-O type, to the CBT-A type, to the CBT-B type, the LA, CA, and MSD of the novel CBT screws decreased with increasing trajectory length. The HU values of the three types of trajectories were all significantly higher than that of the traditional pedicle screw trajectory (p < 0.001). The main factor affecting successful planning of the 3-column CBT screw was pedicle width. Moderating adjustment of the original screw parameters by reducing LAs and CAs to penetrate the anterior, middle, and posterior columns of the vertebral body using the 3-column CBT screw is feasible, especially in the lower lumbar spine.

Towards robotic disassembly: A comparison of coarse-to-fine and multimodal fusion screw detection methods

To accelerate the transition towards a more circular economy it is believed essential to increase the economic viability and hence the adoption of de- and remanufacturing processes. For this, industry 4.0 technologies, including robotization, computer vision and artificial intelligence, are commonly considered as the main enablers to reduce costs while boosting performances of de- and remanufacturing processes. However, the essential step in de- and remanufacturing of screw detection for robotic disassembly is still confronted with various challenges, such as false negatives due to deep screw holes and false positives caused by similar patterns and colors, e.g. letters in labels. Previous studies improved the detection accuracy by capturing images of only a fine part of the product and neglected the negative impact of this imaging approach on the overall time efficiency of the disassembly process. Therefore, two of the most distinct approaches are evaluated in the presented research: 1. A Coarse-to-Fine detection method, where potential screws across the entire product are detected by an area camera in the coarse stage to generate an optimal unscrewing path and screw types and locations are further refined in a second instance, the fine stage. 2. A multimodal fusion detection method, where a combination of a high-resolution color line and 3D triangulation line camera system captures full-product images allowing a single run screw detection in the RGB, Intensity and Depth (RGBID) images. Furthermore, a pooling-based aligned fusion module (PAlign) is introduced to improve the feature representation and mitigate the encountered spatial misalignment of different modality branches. Two industrially representative datasets comprising images of laptops and hard disk drives are collected for the training and evaluation of the screw detection and unscrewing task. Experimental results show that the RGBID fusion method with PAlign module achieves an unscrewing success rate of 80.4 % with an average detection and unscrewing speed of 2.27 s per screw, which is almost double the speed when compared to the Coarse-to-Fine approach. Through a detailed analysis comparing these most distinct screw detection methods in terms of imaging approach, lighting and camera hardware (1/2, area/line, low/high resolution, RGB/RGBID, 600/25.000€), this study provides concrete insights and recommendations aimed at enhancing the efficiency of disassembly systems for sustainable demanufacturing.

RESEARCH ON THE APPLICATION OF ROTARY COMPRESSORS IN GAS TRANSMISSION SYSTEMS

The article provides an analysis of the operating conditions of compressors used for gas transportation in the Azerbaijani gas industry and explores ways to effectively utilize them. It discusses primarily the types, technical specifications, constructions, and application areas of rotary compressors employed in the gas industry. Additionally, information is provided about various types of rotary compressors, including rotary-vane, screw, twin-screw, and scroll compressors. Keywords: gas, vane, screw, rotor, scroll, compressor, cylinder, pressure, piston.

The Attallah screw: Where safety meets robustness in posterior subaxial cervical instrumentation.

Posterior fixation of the subaxial cervical spine (SCS) commonly relies on the application of lateral mass screws (LMS), with pedicle screws being a less prevalent alternative. The present study provides another option: A recently introduced novel approach, the Attallah screw, intended to ensure a safety profile comparable to that of LMS, combined with a strength profile similar to that of pedicle screws. The focus of the present study is the comparative analysis of peak insertion torques for these three screw types. Employing standard surgical techniques and instruments, Attallah screws were scheduled for insertion on the right side of the SCS in 15 cadavers, pedicle screws on the left side in 8 cadavers, and LMS on the left side in the remaining 7 cadavers. The peak insertion torque was recorded using an electronic torque screwdriver. The results revealed that the peak insertion torques were similar in the pedicle and the Attallah screw at C3, C4 and C7, but differed at C5 (mean ± SD; pedicle, 79.5±19.6 cNm; Attallah, 56.7±18.5 cNm; P=0.029) and C6 (pedicle, 85.4±28.7 cNm; Attallah, 49.8±17.9 cNm; P=0.004) in favor of the superior pedicle screw measurements. The peak insertion torques of the pedicle screw were superior to the corresponding data from the LMS from C4 to C7. By contrast, the peak insertion torques of the Attallah screw were only superior to those of the LMS at C7 (Attallah, 69.5±24.5 cNm; lateral mass, 40.5±21.4 cNm; P=0.030), although similar trends were observed at the other cervical levels. On the whole, the findings presented herein indicate the level-dependent superior robustness of the Attallah screw as a posterior cervical fixation method compared to the LMS. However, from a biomechanical perspective, the pedicle screw remains the preeminent choice for fixation within the C5-C6 range.

The effect of C2 screw type on perioperative outcomes and long-term stability after C2-T2 posterior cervical decompression and fusion.

To determine if C2 pedicle versus pars screw type predicts change in fusion status, C2 screw loosening, cervical alignment, and patient-reported outcomes measures (PROMs) after C2-T2 posterior cervical decompression and fusion (PDCF). All adult patients who underwent C2-T2 PCDF for myelopathy or myeloradiculopathy between 2013-2020 were retrospectively identified. Patients were dichotomized by C2 screw type into bilateral C2 pedicle and bilateral C2 pars screw groups. Preoperative and short- and long-term postoperative radiographic outcomes and PROMs were collected. Univariate and multivariate analysis compared patient factors, fusion status, radiographic measures, and PROMs across groups. A total of 159 patients met the inclusion/exclusion criteria (76 bilateral pedicle screws, 83 bilateral pars screws). Patients in the C2 pars relative to C2 pedicle screw group were on average more likely to have bone morphogenic protein (p = 0.001) and four-millimeter diameter rods utilized intraoperatively (p = 0.033). There were no significant differences in total construct and C2-3 fusion rate, C2 screw loosening, or complication and revision rates between C2 screw groups in univariate and regression analysis. Changes in C2 tilt, C2-3 segmental lordosis, C0-2 Cobb angle, proximal junctional kyphosis, atlanto-dens interval, C1 lamina-occiput distance, C2 sagittal vertical axis, C2-7 lordosis, and PROMs at all follow-up intervals did not vary significantly by C2 screw type. There were no significant differences in fusion status, hardware complications, and radiographic and clinical outcomes based on C2 screw type following C2-T2 PCDF. Accordingly, intraoperative usage criteria can be flexible based on patient vertebral artery positioning and surgeon comfort level.

Comparison of Graft Type and Fixation Method in Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-analysis Based on Randomized Control Studies.

The anterior cruciate ligament (ACL) is the most commonly injured ligament in the knee. ACL reconstruction (ACLR) proves the standard for treating this injury. However, graft choice and method of fixation remain a heavily debated topic. This study investigates the following: bone-patellar tendon-bone (BPTB) vs. hamstring tendon (HT) autograft, single-bundle vs. double-bundle hamstring graft, and metal vs. bioabsorbable screws in ACLR. A systematic review was performed on PubMed and Google Scholar according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Data were collected on patient demographics, complications, and functionality scores including International Knee Documentation Committee (IKDC) and Lysholm scores. A systematic review and meta-analysis were conducted with Review Manager. Outcome measurements were determined using forest plots with significant differences considered p < 0.05. Twenty-five studies were included, accounting for 2,170 patients. No statistically significant difference was appreciated when comparing BPTB to hamstring autografts. Patients who received a double bundle HT autograft exhibited significantly superior outcomes in terms of revision (p = 0.05), failure (p = 0.002), normal pivot shift tests (p = 0.04), and normal IKDC (p = 0.008). When comparing screw types, bioabsorbable screws had a greater Lysholm score (p = 0.01) and lower failure rates for copolymer screws (p = 0.03). Overall, the data collected suggested that BPTB and HT autografts display similar postoperative results. However, if an HT autograft is used, the data suggest a double-bundle graft improves both functionality and decreases the possible complications. Finally, bioabsorbable screws prove superior to metal screws when looking at both functionality and failure rates. Further research into the superior graft type is still needed. Level II. See Instructions for Authors for a complete description of levels of evidence.

Optimizing percutaneous reduction and fixation with guidewire modification in pelvic and acetabular fractures: surgical technique and case series.

Minimally invasive percutaneous screw fixation for pelvic ring and acetabular fractures has become increasingly popular due to its numerous benefits. However, the precise placement of the screw remains a critical challenge, necessitating a modification of the current techniques. This paper introduces a refined technique employing a modified guidewire to enhance the precision and efficiency of percutaneous fixation in pelvic and acetabular fractures. This study details the surgical techniques implemented for correcting guidewire misdirection in percutaneous screw fixation and includes a retrospective analysis of patients treated with this modified approach over a three-year period. In this study, 25 patients with pelvic ring and acetabular fractures underwent percutaneous screw fixation. The cohort, predominantly male (23 out of 25), had an average age of 38years. The majority of injuries were due to traffic accidents (18 out of 25). Types of injuries included pelvic ring (6 cases), acetabular fractures (8 cases), and combined injuries (11 cases). Various screw types, including antegrade and retrograde anterior column screws, retrograde posterior column screws, and lateral compression screws, were used, tailored to each case. Over an average follow-up of 18months, there were no additional procedures or complications, such as neurovascular injury or hardware failure, indicating successful outcomes in all cases. This study introduces a simple yet effective method to address guidewire misdirection during percutaneous fixation for pelvic and acetabular fractures, offering enhanced precision and potentially better patient outcomes. Further research with a larger patient cohort is required for a more comprehensive understanding of its efficacy compared to traditional methods. IV. Therapeutic Study (Surgical technique and Cases-series).

Damage evolution modeling of CFRP/Al single-lap screw type blind riveted joints during realistic installation process

As studies on the damage behaviors of composites during screw type blind riveting are notably absent, this paper seeks to fill this gap by combining experimental tests and numerical simulation methods. A three-dimensional finite element model was proposed, and the simulation results were obtained and validated by experimental data. The light microscope and scanning electron microscope were used to observe the stress state, axial deformation, damage modes, and damage distribution in two load-bearing regions at the initial contact and after installation. The results demonstrated that the preload showed a four-step “zero -steep rise -decline -steep rise” development during installation. The stress and deformation were concentrated in two circular zones, with the maximum axial stress component and deformation of 321 MPa and 0.046 mm, respectively. In two pressed zones, there were three failure modes, with out-plane matrix crushing being the most severe. In-plane matrix cracking damage is seen at a 45° direction in the first layer, with a damage index of 0.745. In addition, the effect of two geometric parameters of the sleeve on the blind head shape, load-bearing regions, and CFRP damage was investigated. The results would build confidence in reducing CFRP damage and enhancing joint integrity.

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.

Maintenance of acetabular correction following PAO: a multicenter study comparing stainless-steel and titanium screws.

Stainless-steel screws are commonly used for fragment fixation during periacetabular osteotomy (PAO) at our institutions. Titanium is reserved for patients with documented nickel allergies. Titanium screws possess a significantly lower Young's modulus than stainless steel and, therefore, potentially less resistance to physiologic loading. Thus, we hypothesized that the use of titanium screws might be associated with changes in acetabular correction prior to healing. The aim of this study was to compare the maintenance of acetabular correction following PAO using stainless-steel or titanium screws. A documented nickel allergy was confirmed with an allergy specialist. Patients' age at surgery, gender and BMI were collected. The lateral center-edge angle of Wiberg (LCEA), medial center-edge angle (MCEA), anterior wall index (AWI), posterior wall index (PWI) and Tönnis angle were measured. The delta value for radiographic parameters was calculated as the difference between values immediately post-operation and at 6 months post-operation. Only age at surgery (P < 0.001) and the pre-operative LCEA (P = 0.013) were significantly different between groups (Tables I and II). The remaining pre- and post-operative radiological measurements were similar (Table II). Comparison of delta values at 6 months follow-up indicated no significant differences between screw types (Table III). No patients in the titanium group had a trans-iliac retrograde screw included in their construct (P = 0.003). All patients healed from their osteotomies. The use of titanium screws in patients with an allergy to nickel was not associated with differences in acetabular correction or the rate of osseous union rates despite its lower inherent mechanical properties.

Comparison of cement-augmented pedicle screw and conventional pedicle screw for the treatment of lumbar degenerative patients with osteoporosis.

A retrospective cohort study. To compare the safety and clinical efficacy between using cement-augmented pedicle screws (CAPS) and conventional pedicle screws (CPS) for the treatment of lumbar degenerative patients with osteoporosis. Management of lumbar degenerative patients with osteoporosis undergoing spine surgery is challenging. The clinical efficacy and potential complications of the mid-term performance of the CAPS technique in the treatment of lumbar degenerative patients with osteoporosis remain to be evaluated. The data of 131 lumbar degenerative patients with osteoporosis who were treated with screw fixation from May 2016 to December 2019 were retrospectively analyzed in this study. The patients were divided into the following two groups according to the type of screw used: (I) the CAPS group (n = 85); and (II) the CPS group (n = 46). Relevant data were compared between two groups, including the demographics data, clinical results and complications. The difference in the VAS, ODI and JOA scores at three and 6months after the operation between the two groups was statistically significant (P < 0.05). At 12months after surgery and the final follow-up, a significant difference in the fusion rate was found between the two groups (P < 0.05). Four cemented screws loosening were observed in the CAPS group (loosening rate 4/384, 1.04%) and 15 screws loosening were observed in the CPS group (loosening rate 15/214, 7.01%). In the CAPS group, a total of 384 augmented screws were used, and cement leakage was observed in 25 screws (25/384, 6.51%), but no obvious clinical symptoms or serious complications were observed. Adjacent vertebral fractures occurred in six patients in the CAPS group and one in the CPS group. CAPS technique is an effective strategy for the treatment of lumbar degenerative patients with osteoporosis, with a higher fusion rate and lower screw loosening rate than CPS.

Dislocation structure evolution during room temperature dwell loading of a Ti-6Al-4 V alloy

The current work examines the evolution of the dislocation structure, within both the α and β phases, of a Ti-6Al-4 V alloy subjected to room temperature dwell loading performed at about 96% of the macroscopic yield stress level for several durations, as part of a synchrotron in-situ deformation experiment. The obtained findings represent a vital contribution to creating a scientific basis for improving lifing predictions for aero-propulsion components. The dislocation configuration, type and density were examined post-mortem using transmission electron microscopy (TEM). Despite the relatively low applied stress level, well-developed dislocation structures were already formed within the α phase at a dwell duration of 10 min and changed only modestly up to 60 min. The plastic deformation of the above phase took place solely via dislocation slip. To facilitate a comparison between different dwell durations, the TEM investigation focused on the regions oriented for the prismatic glide that represented the main deformation mode due to the starting crystallographic texture. After deformation, the regions oriented for the prismatic slip contained planar slip bands largely consisting of dislocations of a screw type. There was rather limited interaction between different bands, as the dislocation arrays passed through the slip band intersections with only minor difficulty. The screw-type dislocations seemed to preferentially form during straining. Dislocation Burgers vectors experimentally determined within the β phase occasionally departed from the Schmid rule and such dislocations typically showed a prevalent screw component. Some deformation banding and {112} 〈111〉 − type mechanical twin formation were locally detected within the β phase.

Spinal Robotics in Adult Spinal Deformity Surgery: A Systematic Review.

Spinal robotics have the potential to improve the consistency of outcomes in adult spinal deformity (ASD) surgery. The objective of this paper is to assess the accuracy of pedicle and S2 alar-iliac (S2AI) screws placed with robotic guidance in ASD patients. PubMed Central, Google Scholar, and an institutional library database were queried until May 2023. Articles were included if they described ASD correction via robotic guidance and pedicle and/or S2AI screw accuracy. Articles were excluded if they described pediatric/adolescent spinal deformity or included outcomes for both ASD and non-ASD patients without separating the data. Methodological quality was assessed using the Newcastle-Ottawa scale. Primary endpoints were pedicle screw accuracy based on the Gertzbein-Robbins Scale and self-reported accuracy percentages for S2AI screws. Data were extracted for patient demographics, operative details, and perioperative outcomes and assessed using descriptive statistics. Five studies comprising 138 patients were included (mean age 66.0 years; 85 females). A total of 1,508 screws were inserted using robotic assistance (51 S2AI screws). Two studies assessing pedicle screws reported clinically acceptable trajectory rates of 98.7% and 96.0%, respectively. Another study reported a pedicle screw accuracy rate of 95.5%. Three studies reported 100% accuracy across 51 total S2AI screws. Eight total complications and 4 reoperations were reported. Current evidence supports the application of robotics in ASD surgery as safe and effective for placement of both screw types. However, due to the paucity of data, a comprehensive assessment of its incremental benefit over other techniques cannot be made. Further work using expanded cohorts is merited.

Characterizing orthodontic mini-screws in the hard palate of pigs: An experimental and finite-element study

ObjectiveThis paper analyses the mechanical response of mini-implants under pull-out, push-in, and shear forces. Materials and methodsThe authors have devised a specialized testing apparatus, using a universal testing machine, for the mechanical characterisation of orthodontic mini-implants (OMI) installed in pig hard palate. The experimental investigation encompasses seven screw types, each subjected to pull-out, push-in, and shear forces. Each test was conducted three times to assess the inherent uncertainties, with three torque insertions, with a total of 189 tests. The resulting load-displacement curves provide information on the secant stiffness and ultimate capacity of the tested screws in all three loading scenarios.These findings were used to develop a 3D finite element model to assess the OMI mechanical performance. ResultsTorque is particularly influential in push-in tests for both dependent variables. At the same time, the length appears to be more critical in pull-out tests for the capacity. Diameter's influence is consistent across all tests but is especially significant for the secant stiffness in shear tests. ConclusionsPull-out tests displayed linear behaviour until failure, whereas push-in tests showed increasing stiffness with more significant deformation. Higher torque led to higher capacity with a minor effect on the stiffness. Clinical significanceThis paper provides insights into the mechanical behaviour of orthodontic mini-implants, offering guidance to orthodontic practitioners and researchers. Understanding how torque affects stability and performance under different loads informs the selection and design of mini-implants, potentially improving orthodontic treatments and patient outcomes.

Comparative Performance Evaluation of One-Stage and Two-Stage Object Detectors for Screw Head Detection and Classification in Disassembly Processes

The process of manually detecting and removing screws during disassembly can be time-consuming and demanding. Automated systems utilizing imaging and deep learning can rapidly and accurately identify screws based on features like head shape and size. Different deep learning methods have varying screw detection capabilities. Choosing the right method significantly impacts system effectiveness, robustness and efficiency. Several generic deep learning architectures have been proposed to address this problem. However, there is little guidance on their suitability for specific scenarios. This paper aims to provide qualified guidance for selecting suitable deep learning methods for screw head detection. The proposed approach involves researching existing object detection methods and choosing two representatives – one employing a one-stage approach, the other using two-stage. These selected methods will be implemented identically and their performance evaluated via rigorous analysis and comparison. The dataset comprises synthetic and real images of 6 screw types across 3 products. YOLOv5 was selected for one-stage detectors, Faster R-CNN for two-stage. Results show the one-stage YOLOv5 generally outperforms Faster R-CNN in precision, recall, speed and training times, while Faster R-CNN delivered superior recall with smaller training datasets.

Pull-Out Strength of Orthodontic Miniscrews in the Temporal Bone.

Minimally invasive cochlear implant surgery by using a microstereotactic frame demands solid connection to the bone. We aimed to determine the stability of commercially available orthodontic miniscrews to evaluate their feasibility for frame's fixation. In addition, which substitute material most closely resembles the mechanical properties of the human temporal bone was evaluated. Pull-out tests were carried out with five different types of orthodontic miniscrews in human temporal bone specimens. Furthermore, short fiber filled epoxy (SFFE), solid rigid polyurethane (SRPU50), bovine femur, and porcine iliac bone were evaluated as substitute materials. In total, 57 tests in human specimens and 180 tests in the substitute materials were performed. In human temporal bone, average pull-out forces ranged from 220 N to 285 N between screws. Joint stiffness in human temporal bone ranged between 14 N/mm and 358 N/mm. Statistically significant differences between the tested screws were measured in terms of stiffness and elastic energy. One screw type failed insertion due to tip breakage. No significant differences occurred between screws in maximum pull-out force. The average pull-out values of SFFE were 14.1 N higher compared to human specimen. Orthodontic miniscrews provided rigid fixation when partially inserted in human temporal bone, as evidenced by pull-out forces and joint stiffness. Average values exceeded requirements despite variations between screws. Differences in stiffness and elastic energy indicate screw-specific interface mechanics. With proper insertion, orthodontic miniscrews appear suitable for microstereotactic frame anchoring during minimally invasive cochlear implant surgery. However, testing under more complex loading is needed to better predict clinical performance. For further pull-out tests, the most suitable substitute material is SFFE.