Screw Diameter Research Articles

Outcome of Transbuccal and Transoral Technique in Open Reduction and Internal Fixation of Mandibular Angle Fractures

Background: Angle fractures have the highest percentage among mandibular fractures. It has many reasons like thinner cross section area, presence of third molar, muscle forces acting at the angle area and abrupt change of shape from horizontal to vertical rami. Aim: To determine the outcomes of trans-buccal and trans-oral technique in open reduction and internal fixation of mandibular angle fractures. Study Design: Randomized control trial. Methodology: Total of 194 patients were recruited and divided in two groups. All patients underwent general anesthesia. In trans-oral group incision line was on external oblique ridge, exposing the ridge, the 5 holes mono-cortical plate were twisted and adapted to the ridge contour and fixed with 4 mono-cortical 2mm diameter screws. While in transbuccal approach, the angle region was exposed trans-orally. Statistical analysis: The collected data was analyzed by using SPSS version 25. Chi square was applied with p-value of less than 0.05 as significant. Results: The result showed infection in trans-buccal group was 5.4% and in transoral group was 17.4%. Wound dehiscence in trans-buccal group was 2.2% while in transoral group was 10.9%. Plate or screw loosening in trans-buccal group was 1.1% and transoral group was 7.6%. Mal-union in trans-buccal group was 1.1% and in trans-oral group, it was 7.6%. Conclusion: It was concluded that the trans-buccal is an effective procedure in terms of infection, wound dehiscence, mal-union and plate/screw loosening in comparison to trans-oral approach. Keywords: Trans-buccal, Trans-oral, Infection and Wound Dehiscence.

A Biomechanical Comparison of Fixation Techniques in Metacarpal Shaft Fractures.

Background Typically, metacarpal shaft fractures are treated with closed reduction percutaneous pinning, intramedullary nails, or plate fixation. Recently some surgeons have begun using intramedullary headless compression screws. Questions/Purposes The purpose of this study was to compare intramedullary screw fixation to K-wire fixation, which is the standard of care in a transverse metacarpal midshaft fracture, using a cadaveric model. Our hypothesis was that intramedullary screw fixation would have a biomechanical advantage (higher stiffness and peak load to failure) when compared with dual Kirschner wire fixation of transverse metacarpal shaft fractures. Methods Four-point bend testing was performed to compare stiffness and failure load values of seven paired 2nd and 3rd metacarpals instrumented with headless intramedullary compression screw fixation or Kirschner wire fixation. Similar testing was performed on 14 unpaired 4th metacarpals. Results There was no significant difference in peak load ( p = 0.60) or stiffness ( p = 0.85) between fixation groups for the 2nd and 3rd instrumented metacarpals. For the instrumented 4th metacarpals, there was no significant difference in peak load ( p = 0.14), but the stiffness was significantly greater ( p = 0.01) for the compression screw group compared with the Kirschner wire fixation. Conclusions/Clinical Relevance In this study, the load to failure was not different between the two fixation methods and likely both techniques can sustain physiologic loads needed for rehabilitation. The greater stiffness in the 4th metacarpal compression screw group may be related to the smaller canal morphology than in the 2nd and 3rd metacarpals. Larger diameter screws may be needed to obtain a better fit particularly in the 2nd and 3rd metacarpals.

Study on withdrawal load resistance of screw in wood-based materials: experimental and numerical

ABSTRACT The effects of screw diameter, pilot hole, and material type on withdrawal load resistance (WLR) of screw driven in medium density fibreboard (MDF) and particleboard (PB) were investigated through using experimental and numerical methods. Meanwhile, the results of experimental tests and numerical analysis were compared with the empirical equations. The results showed that (1) the material type and the diameter of screw had significant effects on the WLR, but the pilot hole was not; (2) the equations proposed in Eurocode 5 had better performance in predicting WLRs of screw in both MDF and PB than the other equations; (3) density distributions of wood-based materials affected the mechanical behaviours of WLR of screw; (4) finite element model (FE-model) established could be used to simulate the WLR of screw in wood-based samples; (5) the complex FE-model considering threads of screw can reflect the stress distributions on threads in detail, which contributes to optimal design of threads geometry of screws. And the simplified FE-model without considering threads of screw had advantages in predicting the WLR with higher accuracy.

PENGARUH SUDUT KEMIRINGAN TERHADAP PUTARAN DAN DAYA HIDROLISIS PADA TURBIN ARCHIMEDES SCREW PORTABLE

Picohydro Power Plant is one of the renewable energy sources which utilizes water or irrigation channels with a small head and flow rate. Many factors can affect the hydrolysis power and also the power on the rotation of the screw turbine, one of which is the turbine design. The existing turbine design needs to be evaluated by several factors such as inner and outer screw diameters, slope, screw pitch, number of blades and condition of inlet and outlet as well as head and water flow. Moreover, if the turbine is designed for a portable one with a length of approximately only 1 meter. These factors indicate that the design of each screw turbine design needs to be optimized through data analysis to find the optimal hydraulic power and turbine rotation. This study aims to determine the effect of the tilt angle of the Archimedes screw turbine on the turbine rotation and also the hydraulic power of the picohydro power plant with variations of the turbine tilt angle (K) 20°, 30° and 40°. The method used in this research is to use a Performance Experiment Study by making an Archimedes screw turbine as a picohydro power plant. From the test results using a discharge of 2 ltr/sec, the largest turbine rotation is 144.3 at a 30° turbine tilt angle with 10.77 Watt of produced hydraulic power (P).

Influence of Pedicle Screw Insertion Depth on Posterior Lumbar Interbody Fusion: Radiological Significance of Deeper Screw Placement.

Retrospective case series. To investigate the influence of screw size on achieving bone fusion in posterior lumbar interbody fusion (PLIF). In total, 137 consecutive patients with L4 degenerative spondylolisthesis who underwent single-level PLIF at L4-L5 were evaluated. Factors investigated for their contribution to bone fusion included: 1) age, 2) sex, 3) body mass index, 4) bone mineral density, 5) intervertebral mobility, 6) screw diameter, 7) screw length, 8) screw fitness in the pedicle (%fill), 9) screw depth in the vertebra (%depth), 10) screw angle, 11) facetectomy, 12) crosslink connector, and 13) cage material. Bone fusion was confirmed in 88.2% of patients. The comparison between fusion (+) and fusion (-) groups showed no significant differences in screw size. The %fill and %length were significantly greater in the fusion (+) group than in the fusion (-) group (%fill: 58.5% ± 7.5% vs 52.3% ± 7.3%, respectively, P = .005; %depth: 59.8% ± 9.7% vs 50.3% ± 13.8%, respectively, P = .025). Multivariate logistic regression analysis revealed that %fill (odds ratio [OR]= 1.11, P = .025) and %depth (OR = 1.09, P = .003) were significant independent factors affecting bone fusion. Receiver operating characteristic curve analyses identified a %fill of 60.0% and a %depth of 54.2% as optimal cutoff values for achieving bone fusion. Screw size should be determined based on the screw fitness in the pedicle (%fill > 60%) and screw insertion depth in the vertebral body (%depth > 54.2%) according to individual vertebral anatomy in L4-L5 PLIF.

Novel Dual-Threaded Pedicle Screws Provide Fixation Stability That Is Comparable to That of Traditional Screws with Relative Bone Preservation: An In Vitro Biomechanical Study

Replacement with larger diameter screws is always used in pedicle screw loosening but carries a risk of pedicle wall violation. A pedicle screw with more preserved bone stock is the preferred primary fixation choice. The purpose of this study was to evaluate whether a newly designed proximal-conical dual-thread screw with less bone occupancy provides fixation strength comparable to that of a traditional screw. Six types of pedicle screws based on three different shapes (cylindrical, conical, and proximal-conical) and two thread profiles (single-thread and dual-thread) were grouped. Conical and proximal-conical screws differed mainly in the slope of the outer diameter from the hub to the tip. Conical screws had an outer diameter (6.5 mm) that differed from the hub and tapered by 30% to an outer diameter (4.5 mm) at the tip and proximal-conical screws had the same outer diameter from the hub and tapered by 30% (4.5 mm) at 20 mm from the hub and then maintained the outer diameter (45 mm) to the tip. A total of 36 L4 Sawbones® vertebrae were used in the study and six trials for each screw group. The results of the imaging, screw volume in bone, insertion torque, and pullout force were analyzed. For screws with the same shape, insertion torque and pullout force were significantly higher for those in the dual-thread groups than for those in the single-thread groups (p < 0.05). For screws with the same thread profile, there was no significant difference in either biomechanical test between the different screw shapes (p > 0.05). Our results demonstrated that these proximal-conical dual-thread screws, with the property of relative bone stock preservation, display a comparable biomechanical performance to traditional dual-thread screws and a better performance than single-thread screws. This screw design could serve as the primary pedicle screw choice to reduce revision difficulty.

Identification of safe channels for screws in the anterior pelvic ring fixation system

BackgroundMinimally invasive surgery for pelvic fracture using anterior ring internal fixator system is increasing gradually, and the way to insert the fixation screws in the fixation system is the key technical points of the method. However, there have been few studies on insertion of fixation screws for the anterior pelvic ring internal fixator system.ObjectiveTo identify safe channels for fixation screws in the anterior pelvic fixator system and provide the anatomical basis for insertion of fixation screws in clinical operation.MethodsScrew insertion was simulated into a total of 40 pelvic finite element models as well as 16 fresh pelvic specimens, and the channel parameters were measured.ResultsFinite elements (male, female) include: screws in ilium: length 114.4 ± 4.1 and 107.6 ± 8.3 mm, respectively; diameter 11.7 ± 0.5 and 10.0 ± 0.6 mm, distance between screw and anterior inferior iliac spine: 5.5 ± 1.0 and 5.6 ± 1.0 mm, angle of coronal plane 55.8° ± 2.4° and 50.6° ± 3.1°, angle of sagittal plane 26.6° ± 1.0° and 24.5° ± 1.9° and angle of horizontal plane 64.9 ± 3.7 and 58.1 ± 3.1; screws in pubis: length 47.0 ± 2.0 and 39.8 ± 3.9 mm, diameter 7.1 ± 0.4 and 6.1 ± 0.4 mm. Specimens (male, female) include: distance between screw and anterior inferior iliac spine: 5.5 ± 0.5 and 5.6 ± 0.7 mm, angle of coronal plane 55.9° ± 1.3° and 50.7° ± 1.5°, angle of sagittal plane 26.7° ± 0.5° and 24.1° ± 0.9° and angle of horizontal plane 64.8° ± 0.6° and 58.8° ± 0.8°. In the comparison between female and male in each group, differences in distances between screws and anterior inferior iliac spine and median line of symphysis pubis (P > 0.05) were not statistically significant; differences in the remaining parameters were statistically significant (P < 0.05).ConclusionsIf surgeons paid attention to sex differences, select screws of appropriate diameter and length and hold the insertion position and direction, screws in the anterior pelvic ring fixation system could be safely inserted.

The role of orthopedic screws threads properties on the success of femoral fracture fixation

Stress shielding is created following a reduction in bone density due to the reduction or elimination of mechanical stimuli and the resultant stresses around the implant site in bone tissue. Increased stress shielding can cause the implant or screw to detach or loosen over time, which in turn can lead to severe side effects such as pain, infection, necrosis, and dysfunction. The geometric shape and characteristics of the screws are among the most important factors involved in creating the stress shielding. Hence, the current study aimed to evaluate the influence of bone screw design parameters (i.e., thread profile, thread pitch, screw diameter, and elastic modulus) on stress shielding around the standard screws after implantation in the proximal femur using a viscoelastic finite element modelling. Stress transfer parameters (STP) and strain energy density transfer parameters (SEDTP) were used to evaluate the stress shielding and the risk of screw loosening using the finite element method. This study was performed on screws with titanium and beta-titanium alloy materials as well as HB, HC, and HD ISO threads that are considered as implants for fracture fixation. The results indicated that the HB ISO thread has the least stress shielding and looseness. It was also found that reducing the modulus of elasticity of the screws, increasing the number of threads per screw, reducing the pitch of the screws and the diameter of the screws shaft reduce the amount of the stress shielding and loosening of the screws. This study can provide surgeons with valuable quantitative data for selecting the effective types of screws for bone fracture fixations towards enhanced clinical outcomes.

Retrospective Comparison of Titanium Hybrid Locking Plate with Stainless Steel Hybrid Dynamic Compression Plate for Pancarpal Arthrodesis: 23 Dogs

The aim of this study was to evaluate outcomes and complications of dogs that had pancarpal arthrodesis (PCA) using a titanium hybrid advanced locking plate system (ALPS) and stainless steel hybrid dynamic compression plate (HDCP). Retrospective observational study. Medical records (2007-2020) were reviewed for cases that had PCA performed using ALPS or HDCP. Implant characteristics including metacarpal coverage (MCov), metacarpal width occupied by screw diameter percentage and carpal arthrodesis angle (CAA), complications and outcomes were recorded. Pancarpal arthrodesis was performed with ALPS on 15 limbs from 12 dogs, and HDCP on 14 limbs from 11dogs. Median follow-up time was 1,157 days (range: 62-1,902 days) for ALPS group and 340 days (range: 43-1,465 days) for HDCP. Median MCov for ALPS group was 74% (range: 60-87.5%) compared with 56.5% (range: 49.7-91.3%) for HDCP (p = 0.001). There was no difference in CAA and metacarpal width to screw diameter percentage between ALPS and HDCP group. Major and minor complications and surgical site infection rates were not statistically different between the two groups. Plate fracture occurred in 2/15 ALPS PCA and screw loosening occurred in 4/14 HDCP PCA. Full function was achieved in 8/12 AND 8/11 OF ALPS AND HDCP: cases, respectively, which was not statistically different (p = 0.76). The use of ALPS offers comparable performance to HDCP for PCA.

A Computed Tomography-Based Assessment of the Anatomical Parameters Concerning S2-Alar Iliac Screw Insertion Using "Safe Trajectory Method" in Indian Population.

A retrospective computed tomography (CT)-based radiological analysis. To obtain CT-based morphometric data for the S2 alar iliac (S2AI) screw in the Indian population presenting to School of Medical Sciences and Research, Greater Noida, we used the concept of "safe trajectory" by Pontes and his colleagues in a recent study. Although previous CT-based morphometric studies on the S2AI screw have been published for a variety of ethnic groups, morphometric data specifically for the Indian population are scarce. We used the three-dimensional multiplanar reformatting software to conduct a retrospective CT analysis of 112 consecutive patients who met our exclusion criteria for various abdominal and pelvic pathologies. CT imaging planes were rotated between the S1 and S2 foramen until they matched the ideal S2AI screw trajectory, which was represented by the longest and widest iliac osseous channel observed in the axial CT section. Following the concept of a safe trajectory, S2AI screw morphometric parameters were measured on both sides of the pelvis using corresponding axial and sagittal CT images. In the sagittal and transverse planes on both sides of the pelvis, females had significantly higher screw trajectory angulation than males (p<0.001). On both sides of the pelvis, males had significantly greater iliac width, maximum screw trajectory length, and intrascrotal length than females (p<0.001). On both sides of the pelvis, the S2AI screw entry point in females was significantly deeper than in males from the skin margin (p<0.001). Based on our methodology, we discovered that the S2AI screw trajectory is significantly more caudal and lateral in females, the maximum screw length is sufficient for use in clinical practice regardless of gender, and that 8.5 mm or even larger screw diameters are feasible in the majority of the Indian population.

The effect of additional staple in the tibial fixation of anterior cruciate ligament reconstruction: a biomechanical study in sheep tibia

Objectives: The aim of this study was to evaluate the necessity of staple use and the importance of screw diameter in the anterior cruciate ligament (ACL) reconstruction. Methods: Twenty-eight sheep hind legs were divided into four groups in terms of tibial side fixation type as 7 mm bioabsorbable screw (Group 1), 7 mm bioabsorbable screw and staple (Group 2), 8 mm screw (Group 3), and 8 mm screw and staple (Group 4). The maximum force causing insufficiency in the graft, and the fixation strength between the groups were recorded. The results were compared among the groups. Results: As a result of the statistical analysis regarding the necessity of using staple, group 2, with 7 mm screws and staple, was found to be significantly more resistant than group 1 (p = 0.018). In consequence of the biostatistics study, staple use was found not to create a statistically significant difference between group 3 in which an 8 mm bioabsorbable screw was used and group 4 (p = 0.805). In the statistical study to understand the significance of screw diameter, the samples of group 1 and group 3, in which no staple was used, were compared. It was found that group 3 samples with 8 mm screws had higher strength than those with 7 mm screws (p = 0.011). Between group 2 and group 4 in which a staple was used, despite the increase in screw diameter, the value of maximum strength had no remarkable difference statistically (p = 1.00). Conclusions: Fixation strength is higher when fixation was done with a screw 1 mm larger than tibial tunnel diameter. However, using either a screw with 1 mm wider than tibial tunnel diameter and the screw in the same diameter with the tibial tunnel and additional staple have similar fixation strength on the tibial side. Therefore, we conclude that screw width is more important in maintaining stability of the graft fixation.

Ultrasound-based navigated pedicle screw insertion without intraoperative radiation: feasibility study on porcine cadavers

BACKGROUNDNavigation systems for spinal fusion surgery rely on intraoperative computed tomography (CT) or fluoroscopy imaging. Both expose patient, surgeons and operating room staff to significant amounts of radiation. Alternative methods involving intraoperative ultrasound (iUS) imaging have recently shown promise for image-to-patient registration. Yet, the feasibility and safety of iUS navigation in spinal fusion have not been demonstrated. PURPOSETo evaluate the accuracy of pedicle screw insertion in lumbar and thoracolumbar spinal fusion using a fully automated iUS navigation system. STUDY DESIGNProspective porcine cadaver study. METHODSFive porcine cadavers were used to instrument the lumbar and thoracolumbar spine using posterior open surgery. During the procedure, iUS images were acquired and used to establish automatic registration between the anatomy and preoperative CT images. Navigation was performed with the preoperative CT using tracked instruments. The accuracy of the system was measured as the distance of manually collected points to the preoperative CT vertebral surface and compared against fiducial-based registration. A postoperative CT was acquired, and screw placements were manually verified. We report breach rates, as well as axial and sagittal screw deviations. RESULTSA total of 56 screws were inserted (5.50 mm diameter n=50, and 6.50 mm diameter n=6). Fifty-two screws were inserted safely without breach. Four screws (7.14%) presented a medial breach with an average deviation of 1.35±0.37 mm (all <2 mm). Two breaches were caused by 6.50 mm diameter screws, and two by 5.50 mm screws. For vertebrae instrumented with 5.50 mm screws, the average axial diameter of the pedicle was 9.29 mm leaving a 1.89 mm margin in the left and right pedicle. For vertebrae instrumented with 6.50 mm screws, the average axial diameter of the pedicle was 8.99 mm leaving a 1.24 mm error margin in the left and right pedicle. The average distance to the vertebral surface was 0.96 mm using iUS registration and 0.97 mm using fiducial-based registration. CONCLUSIONSWe successfully implanted all pedicle screws in the thoracolumbar spine using the ultrasound-based navigation system. All breaches recorded were minor (<2 mm) and the breach rate (7.14%) was comparable to existing literature. More investigation is needed to evaluate consistency, reproducibility, and performance in surgical context. CLINICAL SIGNIFICANCEIntraoperative US-based navigation is feasible and practical for pedicle screw insertion in a porcine model. It might be used as a low-cost and radiation-free alternative to intraoperative CT and fluoroscopy in the future.

How to Optimize Pedicle Screw Parameters for the Thoracic Spine? A Biomechanical and Finite Element Method Study.

Pedicle screw study. The selection of pedicle screw parameters usually involves the surgeon's analysis of preoperative CT imaging along with anatomical landmarks and tactile examination. However, there is minimal consensus on a standardized guideline for selection methods on pedicle screws. We aimed to determine the effects of thoracic screw diameter to pedicle width on pullout strength determined by cortical bone purchase. Biomechanical study performed with human cadaveric thoracic vertebrae and experimentally validated three-dimensional finite element model instrumented with pedicle screws of various diameters. We used a variable (SD/PW) ratio to express the screw selection. We hypothesized a positive correlation between the pullout load determined by the bone purchase and the SD/PW. This relationship was first investigated in a validated finite element model considering bone purchase related to the strength of an upper thoracic vertebra. Then, the correlation to the entire spine is evaluated. The failure load ranged from 371.3 to 1601.0N, respectively, for 3 and 6mm screws. The determinant coefficient was increased to R2=.421 when a linear relationship between pullout load and the SD/PW ratio was used. The peak loads of 1216 and 1288N were found for an SD/PW ratio of .83. We have found that the screw pullout load is more correlated to SD/PW than other pedicle measures for a maximized SD/PW ratio of .83. This particular value should be considered the upper limit of the indicated SD/PW ratio and a means to determine the optimal screw diameter to enhance pullout strength.

Degradation of internal fixation materials based on antibacterial and absorbable silk containing different gentamicin concentrations.

Adding gentamicin to silk fibroin enhances both the antibacterial performance and degradation rate of silk-based materials. The increased material degradation rate can affect the strength of early internal fixation, resulting in internal fixation failure. This study sought to adjust the gentamicin concentration to control the material degradation rate, thereby better meeting clinical application requirements. The in vitro degradation, water absorption rate, and expansion rate of silk-based materials containing different gentamicin concentrations were studied. A gentamicin-loaded silk-based screw was implanted into the femurs of New Zealand rabbits. Micro-computed tomography was used to measure the screw diameter, which was then used to calculate the degradation rate. The specimens were stained with hematoxylin and eosin and Masson's trichrome. The in vitro results revealed increasing material degradation rates with increasing gentamicin concentration but no significant differences in water absorption rates with different gentamicin concentrations. The degradation rates of gentamicin-loaded (4mg/g) silk-based rod-like materials were approximately 11.08% at three months in vitro and 9.4% in the animal experiment. The time for complete degradation was predicted from the fitting curve to be approximately 16months. No inflammatory hyperplasia was observed in bone or soft tissue. The degradation and biocompatibility of the material containing 4mg/g gentamicin meet clinical application requirements, and previous experimental results demonstrate good antibacterial performance of materials containing this gentamicin concentration.

Effect of different angulation of forces on mini implant and abutment at various levels

The objective of the study was to evaluate the effect of varying loads of forces at different angulation at various levels of orthodontic mini implant system by using finite element analysis. A 3-dimensional model of the mini implant was constructed to simulate force magnitudes and directions, screw diameters and lengths, and implanted depths of mini implants. Finite element study was conducted with horizontal forces of 100, 150, and 200 g were applied to the mini implant and abutment at angulations 90° and 120. Von Mises stress, strain and displacement values were then evaluated using the ANSYS software. Both stress and displacement increased with increasing the amount of loading force. These 2 indexes were linearly proportional to the force magnitude and produced the highest values when the force was 200 g applied at 120° to the long axis of the miniimplant. The peak deformation and von Mises stress was concentrated on the miniscrew at the cervical level under 200 g at 120°. A wider screw diameter provided superior mechanical advantages. No remarkable differences in the strain distribution were observed at both angulations. However, the stress distribution of the abutment models showed a remarkable difference as compared with the models of mini implant. The high-level area (shown in orange) was localized to the head of the implant and the abutment (cervical part). Compared with 90° group, the orange coloured area was easily observed more in the cervical part of abutment. The von Mises stress values in the MI, were found to be lowest under 100 g force at 90°. Higher initial loading on the mini implant should be avoided and horizontal force on the cervical level of MI should be prevented or minimized for better stability. The abutment has maximum stress concentration which is significantly useful in decreasing the stress concentration on the bone, and has a buffering action on MI. Force range used is within clinically recommended levels; however, the increase in load causes a proportional increase in the stress values.

Thermo-mechanical analysis on shear behavior of grooved connectors for glulam-concrete composite beams under fire

This research analyzed the effects of fire duration, groove length, groove (beam) width, groove depth, screw diameter, and screw penetration length on the shear behavior of grooved connectors for glulam-concrete composite beams under fire. Three-dimensional non-linear finite element (FE) models were used to evaluate the thermo-mechanical behavior of grooved connectors under ISO fire. The model was confirmed by comparing load-slip curves with experimental results. Experimental and numerical results showed that when the failure mechanism shifted from the shear plane failure of the concrete groove to compression failure of the wood in front of the groove, the influence of groove length on shear capacity of connectors was no longer significant. Parametric analysis indicated that with the rise of groove depth, the shear capacity and slip modulus of connectors rose progressively. However, when the failure mode shifted from compression failure of wood in front of the groove to the shear plane failure of the concrete groove, the groove depth had no significant influence on the shear capacity of connectors. The groove (beam) width had a substantial influence on the shear capacity and slip modulus of grooved connectors under fire, whereas it was not the case for screw diameter and screw penetration length.

Rancang Bangun Mesin Ektrusi Pembuat Filamen dengan Sistem Screw Conveyor

Plastic extrusion machine is a tool to carry out the process of extrusion or formation by utilizing plastic blockage by using high temperatures for the process of melting and reshaping with mold into a certain form, where the drive used in the extrusion machine is a power thread formed in such a way as to be able to conduct or move the material. Extrusion machine made with the principle of horizontal shape and use screw conveyor as a material drive in the extrusion process. Extrusion Machine uses HDPE pellets as a test material to print filaments with a attached specification of 31.81 rpm of speed and 915 watt of element band heater power. The process of designing an extrusion machine with the screw conveyor was using standard flight or standard blade, on the grounds that the screw or thread only serves to move the material to the end of the nozzle. The screw conveyor size is 500 mm long, screw diameter is 50 mm and the distance between pitches is 25 mm followed by the dimensions of the machine is 800 x 400 x 600 mm. The test results were conducted using HDPE polyethylene pellet material with variable temperature variations consisting of 5 types of temperature, namely, 120 ° C, 110 ° C, 110 ° C, 95 ° C and 90 ° C, form the five variables above we conducted trials on each temperature. Then we got it and we concluded that the experiment using the temperature variable of 100 ° C has the most optimum output results, where the temperature of 120 ° C and 110 ° C has a liquid output result then the temperature of 90 ° C and 95 ° C has a condition where the material dries too quickly and make the nozzle clogged.

Hydrodynamics and mixing performance in a continuous miniature conical counter-rotating twin-screw extruder

Abstract The mixing performance in a miniature conical counter-rotating twin-screw extruder was investigated by means of experimental technique and computational fluid dynamics (CFD) simulation. An on-line experimental device based on the fluorescence detection was built to study the residence time distribution (RTD). Polypropylene was selected as the flow material and the blend of Polypropylene and anthracene was used as the tracer. This on-line detection device has good reproducibility. The hydrodynamics in the extruder was simulated by the finite element method (FEM) combined with the mesh superposition technique (MST). The particle tracking technique was carried out to evaluate the RTD and mixing efficiency. The effect of screw speed and feed rate on the hydrodynamics and mixing performance was investigated. The velocity magnitude and local shear rate tend to become smaller from inlet to outlet due to the decreasing diameters of screws. The mean length of stretch increases exponentially from inlet to outlet and the mean value of time averaged mixing efficiency remains positive along the axial direction.

Comprehensive analysis of pedicle screw implantation in the C7 vertebra using computed tomography-based three-dimensional models

BackgroundFrom a biomechanical point of view, pedicle screws (PS) are better than other kinds of screws for implantation in the seventh cervical vertebra (C7). However, the application of PS is limited because of the high risk of severe complications. It is essential to define the optimal entry point and trajectory. The aim of this study was to comprehensively analyze the starting point and trajectory for C7 PS insertion using three dimensional (3D) models.MethodsOverall, 60 subjects aged 18 to 67 years old were included. All CT images were used to construct 3D computer models of the C7 vertebrae. A new coordinate system was established for the next evaluation. The pedicle axis was calculated with respect to the entire pedicle; then, the ideal entry point, screw diameter and length, sagittal angle and lateral angle were assessed.ResultsAll the ideal entry points were located at the medial superior to lateral notch (LN), and the mean distance between the entry point and LN was 5.86 ± 1.67 mm in the horizontal direction and 3.47 ± 1.57 mm in the vertical direction. The mean distance between the entry point and the middle point of the inferior edge of the C6 articular process (MP) was 0.74 ± 1.83 mm in the horizontal direction. The mean sagittal angle of the pedicle axis was 90.42°, and the mean pedicle transverse angle was 30.70°. The average diameter and length of the PS were 6.51 ± 0.76 mm and 31.58 ± 4.40 mm, respectively.ConclusionsThis study provided a novel method to calculate the ideal starting point and trajectory for C7 PS insertion. These measurements may be helpful for preoperative planning. It is recommended that 3D CT imaging is used preoperatively to carefully evaluate the anatomy of each individual.

Tibial tunnel enlargement is affected by the tunnel diameter-screw ratio in tibial hybrid fixation for hamstring ACL reconstruction

IntroductionThere is no evidence on screw diameter with regards to tunnel size in anterior cruciate ligament reconstruction (ACLR) using hybrid fixation devices. The hypothesis was that an undersized tunnel coverage by the tibial screw leads to subsequent tunnel enlargement in ACLR in hybrid fixation technique.MethodsIn a retrospective case series, radiographs and clinical scores of 103 patients who underwent primary hamstring tendon ACLR with a hybrid fixation technique at the tibial site (interference screw and suspensory fixation) were obtained. Tunnel diameters in the frontal and sagittal planes were measured on radiographs 6 weeks and 12 months postoperatively. Tunnel enlargement of more than 10% between the two periods was defined as tunnel widening. Tunnel coverage ratio was calculated as the tunnel diameter covered by the screw in percentage.ResultsOverall, tunnel widening 12 months postoperatively was 23.1 ± 17.1% and 24.2 ± 18.2% in the frontal and sagittal plane, respectively. Linear regression analysis revealed the tunnel coverage ratio to be a negative predicting risk factor for tunnel widening (p = 0.001). The ROC curve analysis provided an ideal cut-off for tunnel enlargement of > 10% at a tunnel coverage ratio of 70% (sensitivity 60%, specificity 81%, AUC 75%, p < 0.001). Patients (n = 53/103) with a tunnel coverage ratio of < 70% showed significantly higher tibial tunnel enlargement of 15% in the frontal and sagittal planes. The binary logistic regression showed a significant OR of 6.9 (p = 0.02) for tunnel widening > 10% in the frontal plane if the tunnel coverage ratio was < 70% (sagittal plane: OR 14.7, p = 0.001). Clinical scores did not correlate to tunnel widening.ConclusionTibial tunnel widening was affected by the tunnel diameter coverage ratio. To minimize the likelihood of disadvantageous tunnel expansion—which is of importance in case of revision surgery—an interference screw should not undercut the tunnel diameter by more than 1 mm.