End Of Screw Research Articles

Arthrodesis of the Equine Proximal Interphalangeal Joint: A Biomechanical Comparison of Two Parallel Headless, Tapered, Variable‐Pitched, Titanium Compression Screws and Two Parallel 5.5 mm Stainless‐Steel Cortical Screws

To compare the biomechanical characteristics, failure mode, and effects of side (left or right limb) and end (forelimb or hindlimb) of different screws in 2-screw, parallel-screw proximal interphalangeal joint arthrodesis constructs in horses. In vitro experimental study. Twenty limbs from 6 cadavers (4 complete limb sets, 2 partial sets-total of 4 forelimb and 6 hindlimb pairs). Two parallel 5.5 mm cortical (AO) screws were inserted in lag fashion in 1 randomly allocated limb of a pair, and 2 parallel headless, tapered, variable-pitched, titanium compression screws (Acutrak-Plus) were inserted in the contralateral limb. Constructs were tested in 3-point bending in a dorsopalmar (plantar) direction using a materials-testing machine at a loading rate of 5.83 mm/s. Maximal bending moment at failure and composite stiffness were calculated from data generated on load-displacement curves. Data were analyzed using a Friedman 2-way analysis of variance and Wilcoxon's signed-rank tests. No significant difference was detected for bending moment or stiffness values in proximal interphalangeal joint arthrodesis constructs using 2 parallel Acutrak-Plus or AO screws for fixation. Mean stiffness values were significantly different between forelimb and hindlimb constructs. Performance of 2 parallel Acutrak-Plus screws was biomechanically comparable with 2 parallel AO 5.5 mm cortical screws in in vitro pastern arthrodesis constructs. Acutrak-Plus screws may provide an alternative means of fixation for proximal interphalangeal joint arthrodesis.

In vivo measurement of 3-dimensional movement of the iliosacral joint

The purpose of this study was to quantify in vivo the three-dimensional motion patterns of the sacroiliac joint during passive manipulations as the opinions about the extent of motion of this joint are varied. 12 sacroiliac joints of 6 patients with clinically and radiologically normal joints were investigated. All patients were treated with an external fixator for diagnostic purposes of low back pain unrelated of this study. The motion of the sacroiliac joint was measured continuously with a three-dimensional goniometric system, which was mounted at the end of Schanz screws implanted in S1 and the ilium. All measurements showed relatively small rotation angles around the three main axis to the body between the ilium and the sacrum (< 2 degrees) and very small translations between the screw entry points into the bones (< 1 mm). The maximum rotation angle in the sagittal plane was 1.3 degrees on the right joint and 1.6 degrees on the left joint for flexion plus extension. It is questionable whether this motion can be quantified during manual manipulation. Extension of the hip always produced the largest motion in the sacroiliac joint.

Validation of a continuous granulation process using a twin-screw extruder

Using twin-screw granulation as particle size enlargement technique, the effect of modifying the screw configuration (number of mixing zones, configuration of kneading block) on granule quality, tablet properties and mixing efficiency was investigated. The amount of oversized agglomerates and yield was significantly influenced by the presence of an extra conveying element at the screw end. Changing the staggering angle of the kneading block significantly affected yield and granule friability. The 90° configuration resulted in a lower yield and granule friability. Disintegration time was the only tablet property significantly influenced by the screw configuration as disintegration was significantly faster when an extra conveying element was placed at the screw end. The influence of tracer addition method (wet vs. dry) on mixing efficiency inside the extruder barrel was investigated by means of different tracers: riboflavin (0.05%) suspended in the granulation liquid and hydrochlorothiazide (2.5%) added separately as powder. Mixing efficiency in function of time and granule size (above and below 1400 μm) was tested using riboflavine sodium phosphate (0.05%) dissolved in the granulation liquid. Since a good mixing efficiency was obtained independent of tracer addition method, tracer solubility, granulation time and granule size, continuous granulation using a twin-screw extruder was identified as a robust process.

Treatment of Femoral Shaft Aseptic Nonunion Associated With Broken Distal Locked Screws and Shortening

This retrospective study investigated the treatment of femoral shaft aseptic nonunions associated with broken distal locked screws and shortening. In this study, 11 femoral shaft aseptic nonunions associated with both broken distal locked screws and shortening in 11 consecutive adult patients were treated. All nonunions were associated with at least 1.5 cm (range, 1.5-3.5 cm) shortening. These nonunions were treated by removal of locked nails, one-stage femoral lengthening, static locked nail stabilization, and corticocancellous bone graft supplementation. Postoperatively, ambulation with protected weightbearing was encouraged as early as possible. Ten nonunions were followed up for a median of 4.1 years (range, 1.8-5.5 years), and nine fractures healed at a median of 4 months (range, 3-6 months). The nonunion case had broken locked screws again at 5 months and was treated with exchange nailing. The fracture healed uneventfully at 4 months. No other complications occurred. The key to removal of broken screws is withdrawal of the nail slightly to release the incarcerated broken screw end. The screw end then is pushed out with a used Knowles' pin or a smaller screwdriver under image intensifier guidance. Concomitant one-stage femoral lengthening to treat nonunion with shortening has a high success rate.

THE POSITION OF THE AORTA RELATIVE TO THE SPINE

There is little information documenting the relationship of the aorta to the thoracic scoliotic spine. Recent studies have suggested that the ends of screws placed during an anterior spinal arthrodesis, and pedicle screws used for the treatment of right thoracic scoliosis, may be in proximity to the aorta. The purpose of this study was to analyze the anatomical relationship between the aorta and the spine in a comparison of patients with idiopathic right thoracic scoliosis and patients with a normal spine. Thirty-six patients with adolescent idiopathic scoliosis with a right thoracic curve and forty-three with a normal straight spine were studied. Radiographs were analyzed to determine the Cobb angle, the apex of the curve, and the apical vertebral rotation for the patients with scoliosis. Axial magnetic resonance images from the fourth thoracic vertebra to the third lumbar vertebra at the midvertebral body level were used to measure the distance from the aorta to the closest point of the vertebral body cortex, the distance from the posterior edge of the aorta to the spinal canal, and the aorta-vertebral angle. No differences were found between the groups with respect to age or sex distribution. For the scoliosis and normal groups, boys had greater average vertebral body width and depth for all levels than did girls (p < 0.05). For the scoliosis group, the most common apical vertebra was the eighth thoracic vertebra, the average coronal curve measurement was 55.2 degrees, and the average apical rotation was 17.3 degrees. The average distance from the aortic wall to the vertebral body cortex at the apex of the curve was greater in the patients with scoliosis (4.0 mm) than at similar levels in the normal group (2.5 mm) (p < 0.05). The distance from the posterior aspect of the aorta to the anterior aspect of the spinal canal was less in the scoliosis group (11.1 mm) than in the normal group (19.2 mm) for the fifth to the twelfth thoracic level (p < 0.05). The aorta was positioned more laterally and posteriorly adjacent to the vertebral body at the fifth to the twelfth thoracic level in patients with scoliosis compared with that in normal patients as reflected in a smaller aorta-vertebral angle (p < 0.05). With an increasing coronal Cobb angle in the thoracic curve and apical vertebral rotation, the aorta was positioned more laterally and posteriorly (p < 0.05). In patients with right thoracic idiopathic scoliosis, the aorta is positioned more laterally and posteriorly relative to the vertebral body compared with that in patients without spinal deformity.

Destruction of acetabular bone caused by early failure of a constrained acetabular component

Use of a constrained acetabular component is 1 option for the treatment of dislocation after total hip arthroplasty. We report a case of a constrained acetabular component that resulted in postoperative early fixation loss and required revision 12 days after primary surgery. The superoposterior wall of the acetabulum was destroyed by the migrated acetabular component. Sharp ends of screws with a metal shell may have plowed up acetabular bone gradually after fixation loss of the component. This failure illustrates the potential risk of using a constrained acetabular component for total hip arthroplasty.

Applying the constrained minimum variance control theory on in-line viscosity control in the extrusion molding process

In this study, the constrained minimum variance (CMV) control strategy was applied on the extrusion process. An in-line viscometer was designed and used to measure the viscosity of the polymer melt between the screw end and the die. Under constant temperature, the screw speed was treated as the plant control input, and the viscosity of the polymer melt was treated as the output. The system transfer function and the disturbance dynamic model of the plant were obtained experimentally. Comparing the CMV control strategy with the open loop control method, the variance decreased 39.1% in the simulation, and it also decreased 24.3% in experimental results. This shows that the CMV control method is effective on reducing the fluctuation of viscosity in an extruder. Improved stabilization of the viscosity of the polymer melt in the barrel was thus achieved.

The study of Improvement on Dynamic Characteristics of Position Control System by Viscous Controllable Fluid Damper. 1st Report. Improvement of Dynamic Characteristics of Ball Screw Driving Mechanism by Auxiliary Mass Viscous Damper with Ferro Magnetic Fluid.

The damping capacity of driving mechanism is one of the important factor for the dynamic characteristics of position control system. Generally it is relatively low to realize the high gain position control system or to suppress the external vibration disturbances. But, there is no enough study on designing means to generate the suitable damping capacity intentionally. This study deals with the development and application of electrically viscous controllable dampers with Ferro Magnetic Fluid and Electro Rheological Fluid (ER fluid) to generate suitable damping capacity to feed driving mechanism. This report describes on the study of auxiliary mass viscous damper with FM fluid which only to fit driving ball screw end. After theoretical simulation with mathematical model and actual experiments, it can be verified that the damper is very effective to give suitable damping capacity intentionally to driving mechanism. Moreover, it also can be found design parameter tuning procedure which performs most effectively.

Screw optimization of a co‐rotating twin‐screw extruder for a binary immiscible blend

AbstractThe effect of the screw configuration of a closely intermeshing co‐rotating twin‐screw extruder on residence time and mixing efficiency was studied for an uncompatibilized immiscible PA6/PP (80:20) bend. Alternative screw configurations were investigated systematically. The residence time distribution (RTD) was found to be a poor indicator of the total mixing efficiency, whereas the mixing intensity function yielded considerably better information. High shear stress, sufficient residence time, and high fill ratio in the melting section of the screw were the most important factors in achieving good dispersion of the minor phase. The evolution of morphology along the screw axis depended strongly on the screw configuration. The downstream flow characteristics after the screw end determined the final morphology of the blend.

Foley catheter in removal of a foreign body from rectum.

<h3>To the Editor.—</h3> Foreign bodies in the rectum are of such variety that no single procedure for their removal can be mandated.¹Each case represents a special problem in its management. It must be remembered that careless removal is more likely to result in injury than that which resulted from its insertion. Recently, we have extracted a light bulb from the rectum using insertion of two Foley catheters and its success has prompted us to report this technique. <h3>Report of a Case.—</h3> A 50-year-old man was seen in the emergency room of French and Polyclinic Medical School and Health Center on July 30,1971, with discomfort in the rectum following insertion of a light bulb a few hours before. Rectal examination revealed a light bulb three inches above the anal verge with the screw end of the bulb projecting towards the examiner. The metallic screw part of the bulb was

Loosening by Repeated Impact of Threaded Fastenings

It is common experience that nuts and other threaded fasteners can be loosened by vibration or by impact even though they are initially tight. This report proves that a threaded fastener is hard to loosen when the angle of thread and the measurement of the screw end are properly chosen. The fastener with 60 deg. V thread is easy to loosen. Because the compressive stress waves, being propagated from the pressure falnk, are reflected at the free end of the screw, when they change into tensile stress waves, and they return to the pressure flank on the bolt side only. So a threaded fastener becomes hard to loosen, when the tensile stress waves don't return to the pressure falnk of the bolt thread. On the following two occasions, the tensile stress waves don't return to the pressure flank. (1) When the tensile stress waves are propagated towards the unthreaded part of the bolt. (2) When they are reflected back to the pressure falnk being changed into compressive stress weves.