Traction Angle Research Articles

Surgical skill analysis focused on tissue traction in laparoscopic wet lab training

BackgroundTissue handling is one of the pivotal parts of surgical procedures. We aimed to elucidate the characteristics of experts' left-hand during laparoscopic tissue dissection. MethodsParticipants performed tissue dissection around the porcine aorta. The grasping force/point of the grasping forceps were measured using custom-made sensor forceps, and the forceps location was also recorded by motion capture system (Mocap). According to the global operative assessment of laparoscopic skills (GOALS), two experts scored the recorded movies, and based on the mean scores, participants were divided into three groups: novice (<10), intermediate (10≤ to <20), and expert (≤20). Force-based metrics were compared among the three groups using the Kruskal-Wallis test. Principal component analysis (PCA) using significant metrics was also performed. ResultsA total of 42 trainings were successfully recorded. The statistical test revealed that novices frequently regrasped a tissue (median total number of grasps, novices: 268.0 times, intermediates: 89.5, experts: 52.0, p < 0.0001), the traction angle became stable against the aorta (median weighted standard deviation of traction angle, novices: 30.74°, intermediates: 26.80, experts: 23.75, p = 0.0285), and the grasping point moved away from the aorta according to skill competency [median percentage of grasping force applied in close zone (0 to 2.0 cm from aorta), novices: 34.96 %, intermediates: 21.61 %, experts: 10.91 %, p = 0.0032]. PCA showed that the efficiency-related (total number of grasps) and effective tissue traction-related (weighted average grasping position in Y-axis and distribution of grasping area) metrics mainly contributed to the skill difference (proportion of variance of first principal component: 60.83 %). ConclusionThe present results revealed experts' left-hand characteristics, including correct tissue grasping, sufficient tissue traction from the aorta, and stable traction angle. Our next challenge is the provision of immediate and visual feedback onsite after the present wet-lab training, and shortening the learning curve of trainees.

A comparative study of a two-stage surgical approach combining coronectomy with microimplant anchorage traction for extraction of impacted mandibular third molars with different traction angles

Objective: To establish a two-stage surgical procedure of impacted mandibular third molars (IMTMs) extractions assisted by coronectomy and microimplant anchorage traction and to investigate the influencing factors of root movement and the effects of different traction angles on the clinical outcomes. Methods: Fifty-three IMTM in contact with inferior alveolar nerve (IAN) that underwent tooth extraction in the Peking University School of Stomatology from January 2022 to June 2023 were included, with coronectomy and microimplant anchorage implantation in the first stage of the surgery, root traction was achieved with orthodontic elastic and microimplant anchorages by about 600 g of force, when the IMTM root was detached from IAN, a second surgery was performed to extract the residual root. The basic information of patients and M3M, data on the microimplant anchorage implantation and traction, imaging measurements, and complications were recorded and analyzed. Results: The movement distance of the residual roots was (1.80±0.92) mm, and the duration of traction was (32.9±7.9) d. Multiple linear regression analysis showed that the residual root movement distance was significantly correlated with age, gender, number of roots, traction angle, and depth of the distal bone defect of the second molar (P<0.05). The smaller the traction angle, the more significant the movement of the residual roots (P=0.044). In one case (1.9%, 1/53), the patient experienced abnormal sensation in the lower lip 16 days after traction. Conclusions: The two-stage surgical method of combined coronectomy with rapid traction technique to extract the IMTM allows for rapid movement of the residual root and reduces the risk of IAN injury. The efficiency of root movement can be accelerated by appropriately reducing the traction angle during surgery. The traction effect can be predicted based on indicators such as age, gender, number of roots and depth of distal bone defects of second molar.

Utility of visualization and quantification of surgical techniques using motion analysis software for thoracoscopic surgery.

In this era of endoscopic surgery, feedback from recorded surgical videos is useful and efficient; therefore, effective methods of obtaining this feedback are needed. We analyzed surgical videos using motion analysis software and verified the usefulness of visualizing and objectively evaluating surgical procedures. We measured the grasping and traction angles of the vascular sheath when using forceps and the trajectory of the forceps tip for the upper pulmonary vein during right upper lobectomy during video-assisted thoracoscopic surgery performed by three trainers and trainees. Compared with the trainers, the trainees exhibited insufficient traction of the vascular sheath, performed many slow and unnecessary manipulations, and sometimes performed sudden and fast movements. By visualizing the surgical procedures, the trainee will be better able to identify dangerous or futile movements. It may also make it easier to objectively recognize improvements in one's technique. Motion analysis software could allow for efficient surgical education and self-learning.

Optimization of traction parameters for lumbar scoliosis

BackgroundScoliosis is a high incidence disease that endangers the physical and mental health of adolescents. Traction therapy, as a conservative treatment plan, is helpful to improve the recovery speed of patients by studying the influence of different traction factors on the therapeutic effect.MethodsBased on the thin layer CT data of the lumbar spine of a 16-year-old patient with scoliosis, Mimics21.0 was used to extract the 3D digital model, and Geomagic Wrap2021 was used to perform the smooth surface. After that, SolidWorks was used to manually construct the structures, such as the intervertebral disc, and Ansys17.0 was used to add constraints, ligaments, and other features. Three-factor ANOVA was carried out after an orthogonal experiment that considered traction mode, traction angle, and traction force was finished.Results① A three-dimensional biomechanical model of lumbar scoliosis was created. ② The model’s correctness was confirmed by comparing it to the corpse and other finite element models, as well as by verifying it under a range of working settings. ③ Traction force (P = 0.000), traction angle (P = 0.000), the interaction between traction force and traction angle (P = 0.000), and the interaction between traction mode and traction angle (P = 0.045) were all significant. ④ The interaction between traction force and traction angle has the most significant effect on Cobb, and traction with a certain angle is better than traditional axial traction. ⑤ Traction mode is not significant, but the interaction between traction mode and traction angle is significant.ConclusionsA certain angle of traction can aid in improving outcomes and the traction force can be suitably decreased in the clinical formulation of the traction plan. The uniformity of correcting effect is more favorable when higher fixation techniques like positive suspension or traction bed traction are used, as opposed to overhanging traction.

The Simulation and Parameter Optimization of the Hole-Forming Process of a Duckbilled Hole-Forming Device

This paper addresses the hole-forming process of a duckbilled hole-forming device. Based on a coupled simulation using the multi-body dynamics software RecurDyn and the discrete element software EDEM, the hole-forming mechanism of a duckbilled hole-forming device and the influence of control parameters on the hole-forming performance of the hole-forming device were studied. In this paper, we analyze the direction and speed of soil particles transported under soil disturbance by a hole-forming device through the simulation and study of the hole-forming mechanism of the hole-forming device. By controlling parameters such as the traction angle, forward speed, and mass of the hole-forming device, the influence of the control parameters on the hole-forming trajectory of the duckbilled hole-forming device was investigated. Orthogonal tests determined the optimal combination of control parameters. The results show that the hole-forming process of the hole-forming device mainly comprises squeezing and shearing the soil to form holes, and the hole-forming performance of the hole-forming device was optimal when the traction angle was 17.3°, the forward speed was 1.11 m/s, and the mass of the hole-forming device was 17.9 kg.

Design of class III intermaxillary traction titanium plate for boneanchorage based on finite element analysis

The purpose of this article is to investigate the effect of different bending angles and traction directions of the traction arm on the stability of the titanium plate for bone-anchored maxillary protraction (BAMP). The titanium plate models with different bending angles of the upper and lower jaws were modelled in three dimensions, where the bending angles were 90°, 120°, 135°, 150°, 180° and recorded as U1-U5 and L1-L5 respectively. Finite element analysis was performed on the titanium plates with different structural parameters to complete the structural design selection study of the titanium plates. The displacement limit was defined and different angular tensile forces were applied to record the equivalent stress and displacement of the titanium plates under each working condition. A total of 120 sets of orthogonal simulation tests were designed, which showed that the stress values at U2, U3 and U4 are smaller at traction angles of 135° (66.152 MPa), 155° (59.015 MPa) and 175° (55.589 MPa) respectively. The displacement is correspondingly smaller at tensile angles of 135° (0.0073 mm), 150° (0.0056 mm) and 160° (0.0058 mm). L2 has the smallest stress value (50.491 MPa) and displacement (0.0062 mm) at a tension angle of 120°. Therefore, it is recommended to design a titanium plate with a mandibular traction arm bending angle of 120° for BAMP, and the traction arm bending angle of the maxillary titanium plate can be flexibly designed according to the clinical traction direction.

Effects of Voluntary Quadriceps-Hamstring Cocontraction on Tibiofemoral Force During Isometric Knee Extension and Knee Flexion Exercises With Constant External Resistance.

A biomechanical model has been developed to assess the effects of a voluntary effort of quadriceps-hamstring cocontraction on tibiofemoral force during isometric knee flexion and knee extension exercises with constant external resistance. The model establishes the analytic condition in the moment arms and traction angles of the quadriceps and hamstring muscles that determines the direction (anterior/posterior) of the tibiofemoral shear force developed by the cocontraction. This model also establishes the mechanical effect (loading/unloading) on the anterior cruciate ligament (ACL). At about 15° of knee flexion (where the ACL experiences its maximum quadriceps-induced strain) a voluntary quadriceps-hamstring cocontraction effort yields: (1)nearly the same enhancement in hamstring and quadriceps activation, (2)an increase in hamstring force about 1.5 times higher than that of the quadriceps, and (3)posterior (ACL unloading) tibial pull and compressive tibiofemoral force that increase linearly with the level of quadriceps and hamstring activation. The sensitivity of the results to intersubject variability in the posterior slope of the tibial plateau and muscle moment arms has been estimated with the use of anatomic data available in the literature. An anterior (ACL loading) tibial pull is actually developed at 15° of knee flexion by a voluntary effort of quadriceps-hamstring cocontraction as the posterior tibial slope exceeds 14°.

Traction for the treatment of traumatic atlantoaxial subluxation in adults

To observe the application of modified traction therapy in traumatic atlantoaxial subluxation in adults. The clinical data of 31 patients with atlantoaxial subluxation treated from March 2018 to June 2019 were restropectively analyzed. There were 15 males and 16 females, aged from 18 to 68 years old with an average of 39 years old, including 10 cases of 18-40 years, 15 cases of 41-60 years, 6 cases of 51-68 years. The main manifestations of the patients were limited neck movement, pain, and atlantoaxial CT scan showed different degrees of atlantoaxial subluxation. Three dimensional multifunctional traction bed was used for traction for 2 min, relaxation for 10 s. The traction angle starts from the rearward extension of 5°-10° and weight from 3-6 kg. The weight increased by 1 kg every two days until the symptoms were improved. Traction time was 30 min twice a day and 10 days for a course of treatment. One course of treatment was performed in patients with 1-2 mm left and right equal width of atlantoaxial space, and two courses of treatment were performed in patients with 3-4 mm left and right equal width of atlantoaxial space, and the course of treatment could be increased to 3 months in especially patients with serious problems, such as 4 mm left and right equal width of atlantoaxial space and no improvement after conventional treatment. The criteria to evaluate the clinical effect was cure:no pain in the neck, normal range of neck movement, CT showed normal atlantoaxial space and odontoid process was in the middle, patients with normal neck movement were followed up 1 month after the end of treatment;improvement:neck pain was significantly improved and CT showed that the left and right atlantoaxial space was less than 1 mm in equal width. Among the 31 patients, 17 cases were cured by one course of treatment, 11 cases were cured by 2 courses of treatment, and 2 caseswere improved. The modified traction therapy has obvious effect on adult traumatic atlantoaxial subluxation, especially the subluxation of 3-4 mm equal width in left and right atlantoaxial space, and this method is safe and reliable with good efficacy and the patients without discomfort.

A potential factor in the pathophysiology of lateral epicondylitis: The long sarcomere length of the extensor carpi radialis brevis muscle and implications for physiotherapy

Lateral epicondylitis is a chronic angiofibroblastic degeneration of the origins of the wrist extensor muscles and is characterized by diffuse elbow pain. Although it is the most common syndrome of the elbow joint, the most affected structure is the tendon of the extensor carpi radialis brevis (ECRB) muscle. Several theories have been proposed to explain the pathophysiology of lateral epicondylitis, however, there is no evidence to show that the sarcomere length and microanatomical features of the ECRB muscle can be affected by the elongated position of the muscle. We hypothesized that the tensile response may be the responsible mechanism in the pathophysiology of lateral epicondylitis due to the microanatomy of the ECRB muscle and its functioning in the elongated position. Elongated position leads to elongation of the sarcomere length by forming a functional traction angle in the ECRB muscle. The elongated sarcomere length negatively affects muscular microcirculation. Poor microcirculation triggers ischemia in the muscle and tendon and leads to an increase in immature Type III collagen synthesis. Disruption of the collagen continuity and the loss of load-bearing capacity initiate the neovascularization process. This situation accelerates the degeneration process in the tendon and prevents healing. Furthermore, based on our hypothesis, we recommend new physiotherapy approaches that may contribute to reducing the increased incidence of tendinopathy and to the healing process.

A multi-body model for comparative study of cervical traction simulation – comparison between inclined and sitting traction

A computer simulation model was developed to compare the result of cervical traction therapy in inclined and sitting traction positions. The behavior of the model was shown to match with the intervertebral changes in the upper and lower spine from the data of a radiographic experiment. Both the results of the experiment and the simulation also showed that in the inclined position, the amount of posterior separations in the upper cervical spine remains constant regardless of traction angle, while the posterior separations at lower cervical spine increases along with traction angles. Using the simulation model, parametric studies were conducted to investigate the intervertebral space changes in response to different traction angles in the inclined and sitting positions. When using the sitting position, the subject’s hip joint stiffness was shown to cause larger variations in the intervertebral space than in the inclined position. In addition, variations in the tension/compression stiffness was shown to cause the largest changes in the resulting separations in both positions but the variations in anterior space changes were larger in the sitting position. Our study suggests that the inclined position is less sensitive to variations in the subject's body parameters and is able to provide a more reliable and predictable traction result than the sitting position.

Effect of the positional relationship between the interference screw and the tendon graft in the bone tunnel in ligament reconstruction

To reveal the effects of the positional and length relationships between the interference screws (ISs) and the tendon graft in the bone tunnel on the fixation strength in ligament reconstruction. We compared three IS positions on the anterior (the Anterior group) or posterior (the Posterior group) or side (the Side group) of the tendon graft in relation to the pullout direction. The tendon graft was pulled at 0°, 30°, 60°, and 90° to the bone tunnel, and the maximum pullout load at each angle was compared among the groups. We also investigated the relationship between the length of the tendon graft and the length of the IS in the bone tunnel. The direction of the pullout force was the same as that of the Anterior group, and the maximum load was compared between groups in which the tendon graft was longer or shorter than the IS. The maximum loads of the Anterior group were significantly greater than those of the Posterior and Side groups at the traction angles of 30° and 60°, respectively. An IS shorter than the tendon graft was found to provide significantly superior fixation strength compared to an IS longer than the tendon graft. Better fixation strength was achieved when the IS was placed on the side of the anchorage tunnel on which the tendon graft was loaded and the IS was shorter than the tendon graft.

Pullout Strength of All-Suture Anchors: Effect of the Insertion and Traction Angle—A Biomechanical Study

To evaluate the pullout strength of the all-suture anchor (ASA), based on the angles of anchor insertion and traction. Synthetic saw bones of 2 densities (0.16 and 0.32g/cm3) with 3mm thick cortical bone models were used. ASAs were inserted at 45°, 60°, 75°, or 90° and pulled at 2 angles from the surface: 45° (simulating the physiological pull of the supraspinatus) and 90° (simulating pulling out during knot tying). Five consecutive pullout tests for each insertion and traction angle combination per saw bone were conducted to evaluate the ultimate load to failure and mode of failure (80 tests total). Thereafter, 9 matched pairs of human cadaveric humeri with 2 ASA types were used (insertion angles, 45°, 75°, 90°; traction angle, 90°). Nine consecutive tests were conducted for each insertion angle and anchor type (54 tests total). The pullout strength was significantly higher for high density- than for low-density saw bones (all P < .05). The pullout strength was higher at the 45°than at the 90° traction angle (all P < .05) and was significantly higher at the 90° and 75° than at the 45° insertion angle in both high-density saw bones and cadaveric humeri (all P < .05). However, the pullout strength was not significantly different by ASA type (all P > .05). ASA showed stronger pullout strength in higher density bones. Furthermore, it presented stronger pullout strength in the physiological traction direction of supraspinatus rather than in the knot-tying direction, consistent with the deadman theory. However, stronger pullout strength was observed in the vertically directed insertion angle, not 45°. Therefore, implanting the ASA vertically may be clinically more beneficial not only when performing knot tying during surgery, but also when the supraspinatus tendon loads the ASA postoperatively. The study provides biomechanical evidence that the optimal insertion angle for an ASA is more vertical than the 45°.

Calculation of equivalent friction coefficient for castor seed by single screw press

Based on the traction angle and transportation rate equation, castor beans were pressed by application of single screw under different cake diameter and different screw speed. The results showed that the greater the cake diameter and screw rotation speed, the greater the actual transmission rate was. The equivalent friction coefficient was defined and calculated as 0.4136, and the friction coefficients between press material and screw, bar cage were less than the equivalent friction coefficient value.

Idiopathic macular holes and direction of vitreomacular traction: structural changes and surgical outcomes.

PurposeTo compare the structural changes, clinical course, and treatment outcomes of vertical and horizontal vitreomacular traction (VMT) induced impending macular holes (IMHs) and full-thickness macular holes (FTMHs).MethodsIn this retrospective study, 23 and 32 cases of IMHs and FTMHs, respectively, were analyzed. The IMH cases were divided into two subgroups: IMH with and without foveal detachment. Vitreofoveal traction angles (TAs) between the inner retinal surface and posterior hyaloid were measured from horizontal and vertical optical coherence tomography (OCT) images by using the trigonometric function (the angle equals the arctangent of the height over the base) after adjustments for magnification factors. The largest angle was defined as the vitreomacular TA for the examined case. The critical angle-the TA differentiating cases with (vertical traction) or without (horizontal traction) foveal detachment (vertical traction)-was determined using regression analysis. Pretreatment and posttreatment OCT images, clinical courses, and treatment outcomes were compared between the two groups.ResultsThe critical angle was 27.2°. Cases of vertical traction had higher foveal height in the IMH group and wider bases in the FTMH group (P<0.05 respectively). IMHs with vertical traction had greater VM attachment than those with horizontal traction. In the FTMH group, postoperative visual improvement was lower (P=0.002); in the vertical traction group, inner segment:outer segment defects persisted longer (P=0.02).ConclusionsThe critical angle separating vertical from horizontal traction was 27.2°. Vertical VMT results in greater foveal structural changes in IMHs and possibly less favorable surgical outcomes in FTMHs.

The Effect of Traction Position in Cervical Traction Therapy Based on Dynamic Simulation Models

This study describes the development of a cervical traction therapy simulation model that evaluates two types of the traction positions, namely the sitting position and the inclined position. An anatomically correct human skeleton model and two mechanical traction device models were constructed in simulations using a physics engine. The anterior and posterior intervertebral separations were measured at both positions with a series of traction forces (60N to 200N) and traction angles (10° to 40° ). The result suggested that the sitting position caused the subject to lean forward and as a result led to excessive anterior compression when traction angle is over 20 degrees. The inclined position creates greater intervertebral separations on both the anterior and posterior sides than the sitting position. This suggests that the inclined position may be more effective in increasing intervertebral separation than the sitting position.

Experiment and Dynamic Simulation of Cervical Tractions in Inclined and Sitting Positions

This study aims to validate the accuracy of a cervical traction therapy simulation model by comparing the intervertebral separations of six asymptomatic male adults when traction was applied to their cervical spines. The subjects were tested on two mechanical traction devices, representing the inclined and sitting positions. A total of 55 radiographic images of their cervical spines were taken before and during traction. The result showed statistically significant intervertebral space changes in the inclined position but the changes in the sitting position were not statistically significant. The observed changes of the cervical spine were used to adjust parameters of the traction therapy model, which contains a human model with cervical spine built with springs and dampers and two traction devices in inclined and sitting positions. A series of traction forces and traction angles were applied to the model to simulate the actual parameters used in the experiment and the new model was used to evaluate the two traction positions. The result suggested that inclined position creates greater intervertebral separations on the posterior sides. Differences in separations due to age were not observed in both positions. The result also suggested that the inclined position provides better control in positioning the separations at different spinal segments than the sitting position.

Multimodal Treatment Program Comparing 2 Different Traction Approaches for Patients With Discogenic Cervical Radiculopathy: A Randomized Controlled Trial

ObjectiveThe purpose of this study was to investigate the immediate and long-term effects of a 1-year multimodal program with the addition of 2 different traction approaches on the pain, function, disability, and nerve root function in patients with discogenic cervical radiculopathy (CR). This study also attempted to identify the optimal traction angle based on the maximum recovery of the peak-to-peak amplitude of the flexor carpi radialis (FCR) H-reflex. MethodsThis randomized clinical trial with one-year follow-up included a total of 216 (101 female) patients with unilateral lower discogenic CR were randomly assigned to 1 of 3 groups. The standard care group (C) received the multimodal program (pain relief methods, muscle strengthening, and thoracic spine manipulation). The ventroflexion traction group (A) received the same multimodal program as group C, with added traditional ventroflexion traction. The novel traction group (B) received the same multimodal program as group C in addition to a flexor carpi radialis (FCR) H-reflex-based traction method. Primary outcomes were the Neck Disability Index (NDI) and secondary outcomes included neck pain, arm pain, and the amplitude and latency of the H-reflex. Patients were assessed at 3 intervals (pre-treatment, 4 weeks post-treatment, and the 1-year follow-up). ResultsThe mixed linear model with repeated measures indicated a significant group × time effect in favor of the novel cervical traction group (B) for measures of NDI (F = 412.6, P < .0005), neck pain (F = 108.9, P < .0005), arm pain (F = 91.3, P < .0005), H- reflex amplitude (F = 207.7, P < .0005), and H-reflex latency (F = 58.9 P < .0005). We found that the extension position of cervical spine (5° extension) was the position that achieved the maximum improvement in the novel cervical traction method. ConclusionsThis preliminary study showed that a multimodal program with a novel cervical traction method added improved NDI, neck pain, arm pain, and the amplitude and latency of FCR H-reflex for a group of patients with chronic discogenic CR.

Stress distribution inside bone after suture anchor insertion: simulation using a three-dimensional finite element method

To define stress distribution patterns inside a bone around suture anchors inserted at different angles using a three-dimensional finite element (FE) method. An isotropic cube model (Young's modulus, 1,380MPa; Poisson's ratio, 0.3) was designed on a computer to standardize analysis conditions. A virtual Twinfix anchor was inserted into the cube at two different angles (45° and 90°) against the top surface. A traction force (100N) was applied to the anchor at six different angles (15°, 30°, 45°, 60°, 75° and 90°) against the top surface. Elastic analysis was performed, and the distribution of the von Mises equivalent stress inside the cube was calculated. The highest value of the equivalent stress at each traction angle was compared between the 45° and 90° anchor insertion settings. Stress concentration was most evident around proximal anchor threads, particularly on the traction side. Interestingly, stress gradually declined with an increase in traction angle only for the 90° insertion setting. At 15° and 90° traction angles, the equivalent stress was lower for the 45° insertion setting than for the 90° insertion setting. In contrast, the 90° insertion setting exhibited lower equivalent stress than the 45° insertion setting at 30°, 45° and 60° traction angles. Insertion of an anchor at 90° might reduce the stress concentration around the proximal anchor threads on the traction side and provide lower equivalent stress in the middle range of traction angles (30°-60°) than insertion at 45°. This could avoid early postoperative anchor failure.

Vectored Cranial-Cervical Traction Limits Facial Contact Pressure from Prone Positioning During Posterior Spinal Deformity Surgery

Prospective, two-way complete block design analyzing facial contact pressures during prone positioning with the use of cervical traction for spinal surgery. Level 2 evidence. To assess the effect of varying traction angle and traction weight to limit facial contact pressure. Posterior spine surgery has known hazards related to the prone positioning. Cervical traction is used to limit downward pressure exerted to the face to stabilize the head and neck and to aide in deformity correction. The effects of the traction angle and force on facial contact pressure have not been studied. Facial contact pressure was measured for 10 patients undergoing posterior spine surgery in the prone position with Gardner-Wells tongs applied for cervical traction. The facial contact pressure was measured with a force transducer at each of three angles from horizontal (0°, 30°, 45°) and each of four traction weights (0, 5, 10,15 lb), a total of 12 measurement parameters for each patient. An in-line tensiometer provided consistent application of force throughout the traction system. Ten patients, average age 15 ± 0.6 years, six female, BMI 21.3 ± 1.7, underwent facial pressure monitoring. Post hoc analysis showed that both higher traction weights and angles significantly limited facial pressure (P = 0.0001). The lowest overall average facial pressure of 0.51 lb (95% CI = 0.28-0.73) occurred with 15 lb of traction applied at 45° above the horizontal. This was significantly less facial pressure than found when traction was applied at all weights tested using the commonly employed 0° in-line traction angle (P < 0.0001). A combination of upward vectored 45° traction angle and 15 lb of weight significantly decreased facial contact pressure. The use of an "in-line tensiometer" assured an accurate force application.

Modeling the solids conveying zone of a novel extruder

AbstractOn the basis of the theory of relative motions, a novel nested screw extruder was invented in which one rotating outer screw acted as the barrel for an inner screw; the combination of the outer screw and outer barrel was the other extrusion system. It was realized that centrifugal force resulted in the difference between the forces acting on the solids by the screw and by the barrel, which further compacted the solid pellet or powder. These factors benefited the frictional drag of solids and the early melting. This was consistent with the fact that the solids conveying flow rate increased greatly when the barrel and screw rotated oppositely at the same time. Thus, centrifugal force and material compressibility were significant in the feeding zone. A mathematical model was developed to calculate the output, pressure, and velocity of the solids in the screw down‐channel with consideration of the centrifugal force and material compressibility. The predicted pressure distribution and output were better than those by previous models in fitting the experimental data. The simulations revealed that the maximum traction angle was close to 90° − the helix angle for maximum output in contrast to the maximum traction angle of 90° predicted by the Darnell–Mol theory. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008