Pin Configuration Research Articles

Prospective, surgeon-randomized evaluation of crossed pins versus lateral pins for unstable supracondylar humerus fractures in children

Controversy exists concerning pin placement for supracondylar humerus fractures in children. Both crossed pin and lateral only pin configurations have shown good results; however, prospective studies are lacking. We present a prospective, surgeon-randomized study comparing crossed pin (group A, n = 20) versus preferential lateral only pin (group B, n = 20) fixation for displaced supracondylar humerus fractures. There was no difference in Baumann's angle (P>0.75), the humerotrochlear angle (P>0.85), or final elbow range of motion (P>0.25). Both groups had stable reductions and clinically normal alignment. The only complication in both groups was a transient ulnar nerve irritation, despite no intraoperative evidence of nerve violation with a nerve stimulator. One patient in each group required modification of the operative plan. In group B, one patient had a medial pin inserted because of medial comminution extending proximally limiting available lateral pin placement. In group A, the surgeon elected to use lateral pins only because of an obviously subluxating ulnar nerve. In conclusion, we recommend orthopedic surgeons treating unstable pediatric supracondylar humerus fractures be facile with both medial and lateral pin placement.

Suppression of Edge Recombination in InAs/InGaAs DWELL Solar Cells

AbstractThe InAs/InGaAs DWELL solar cell grown by MBE is a standard pin diode structure with six layers of InAs QDs embedded in InGaAs quantum wells placed within a 200-nm intrinsic GaAs region. The GaAs control wafer consists of the same pin configuration but without the DWELL structure. The typical DWELL solar cell exhibits higher short current density while maintaining nearly the same open-circuit voltage for different scales, and the advantage of higher short current density is more obvious in the smaller cells. In contrast, the smaller size cells, which have a higher perimeter to area ratio, make edge recombination current dominant in the GaAs control cells, and thus their open circuit voltage and efficiency severely degrade. The open-circuit voltage and efficiency under AM1.5G of the GaAs control cell decrease from 0.914V and 8.85% to 0.834V and 7.41%, respectively, as the size shrinks from 5*5mm2 to 2*2mm2, compared to the increase from 0.665V and 7.04% to 0.675V and 8.17%, respectively, in the DWELL solar cells. The lower open-circuit voltage in the smaller GaAs control cells is caused by strong Shockley-Read-Hall (SRH) recombination on the perimeter, which leads to a shoulder in the semi-logarithmic dark IV curve. However, despite the fact that the DWELL and GaAs control cells were processed simultaneously, the shoulders on the dark IV curve disappear in all the DWELL cells over the whole processed wafer. As has been discussed in previous research on transport in QDs, it is believed that the DWELL cells inhibit lateral diffusion current and thus edge recombination by collection first in the InGaAs quantum well and then trapping in the embedded InAs dots. This conclusion is further supported by the almost constant current densities of the different area DWELL devices as a function of voltage.

ＤＥＭによる媒体撹拌ミル撹拌ロータのピン形状が媒体運動に及ぼす影響の解析

Beads motion in a stirred mill filled with a slurry was simulated by the Discrete Element Method (DEM), enabling to calculate the impact energy of beads. Since the specific impact energy of beads is known to be well correlated with the grinding rate constant, it was monitored as an effective index of grinding performance in the simulation work. The present work is to investigate effect of the pin configuration, particularly, the number of pins attached on the agitator and their length on the beads motion as well as the impact energy. The pins were attached on the axis of the agitator equi-interval in the circumference direction and 3-line in the horizontal axis in the mill. We have found that the beads motion is dependent on the number of pins, and the specific impact energy reaches the maximum value at 8 in number of pins under the present condition. In addition, the maximum value under the specific impact energy is shifted towards large number of pins as the beads filling ratio increases. The specific impact energy of beads is increased with an increase in pin length.

Biomechanical Analysis of Supracondylar Humerus Fracture Pinning for Slightly Malreduced Fractures

The most common position of malreduced type III supracondylar humerus (SCH) fractures is internal rotation and medial collapse of the distal fragment. The purpose of this study was to determine the effect of SCH fracture rotational deformity on stability with various pin configurations. Specifically, is the biomechanical stability lost when an SCH fracture is pinned in slight malreduction (compared with anatomical pinning) improved by adding a third pin? Sixty-four synthetic humeri were sectioned in the mid-olecranon fossa to simulate an SCH fracture. Specimens were randomized to an anatomically reduced group or a group with 20 degrees of distal fragment internal rotation (n = 32 per group). Each was randomized to one of 4 pin configurations: 2 laterally divergent pins, 2 crossed pins, 3 laterally divergent pins, or 2 lateral with 1 medial pin (n = 8 per group). All fractures were stabilized with 1.6 mm (0.062 in) Kirschner wires. Models were tested in extension, varus, and valgus for 10 cycles between 5 N and 50 N. Internal and external rotations were tested between +/-1 Nm. Data for fragment stiffness (newtons per millimeter or newton millimeters per degree) were analyzed with a 2-way analysis of variance (p < 0.05). Internally rotated fractures were significantly less stable than the anatomically reduced group for external rotation, internal rotation, and varus loading regardless of pin configuration. Within the malreduced group, 3-pin configurations were more stable than 2-pin configurations in internal rotation, varus, and extension loading. Two lateral divergent pins were similar to 2 crossed pins, except in extension, where 2 lateral pins had greater stiffness. Construct stiffness for malreduced specimens after pinning was less than those pinned with an anatomical reduction when loaded in varus, internal rotation, and external rotation. For simulated fractures with residual internal rotation, the addition of a third Kirschner wire compared with an anatomically reduced 2-crossed-pin configuration resulted in increased stiffness of the model for all loading directions. Consider a 3-pin pattern, either 3 laterally divergent pins or 2 lateral pins and 1 medial pin, for SCH fractures when a less than complete anatomical reduction is obtained.

Journal Scan: Journal of Pediatric Orthopaedics

Here is my view of the top-10 most potentially influential papers from the Journal of Pediatric Orthopaedics from 2007. Included are the papers that were thought to provide the most useful examinations of treatments and outcomes.

Vibration damping for a cue stick

In an embodiment of the invention, a vibration damping shaft of a cue stick comprises a shaft that is configured to form an axially rigid ensemble by mating with another segment of a cue stick. The shaft includes damping material that reduces the vibration of the shaft when a ball strikes the shaft. The damping material may have a density greater than wood. The damping material may be configured as an annular region in the shaft, or in any other configuration that reduces shaft vibration. Damping materials include composites, such as piezoelectric materials, with fibers that are generally aligned to reduce shaft vibration. Another embodiment of the invention utilizes a universal shaft insert, allowing the shaft to fit another segment of a cue stick having a particular joint pin configuration. Features of the a vibration damping shaft may also be incorporated into a cue stick that is not collapsible.

Cross pinning of supracondylar fractures from a lateral approach. Stabilization achieved with safety

Various pin configurations are possible to stabilize a supracondylar fracture. While cross pinning gives the best stabilty the disadvantage is the risk of iatrogenic ulnar nerve injury. We combine a cross pin fixation with a lateral approach. The aim of the study was to prove our method retrospectively to show the advantage of lateral cross-pinning achieving stabilty and avoiding ulnar nerve injury. Between 1 January 2001 and 31 December 2002, 84 supracondylar fractures were treated with invasive surgical procedure. The intention was a primary closed reduction. Following closed reduction under general anaesthesia, two K-wires were introduced from the lateral side, one ascending and the other descending. If it was not possible to perform a closed reduction, an open reduction was performed by medial-lateral crossed K-wire fixation. After either an open or closed reduction, the pins were buried under the skin. The results were evaluated using Flynn's score. The mean time of follow-up was 18.9 months. Seventy-seven percent of the patients were treated with a closed reduction, while 23% needed an open reduction. A clinical follow-up examination was done at an average of 18.9 months following the trauma. Of those treated with a closed reduction alone, 93% had an excellent or good functional result. Of those requiring an open reduction, 88% had excellent or good result. None of our patients exhibited secondary dislocation or iatrogenic ulnar palsies. Closed reduction and lateral crossed pin fixation with ascending and descending K-wires buried under the skin is an effective method to treat type II and III supracondylar fractures in children. The method gives stability and avoids iatrogenic ulnar nerve injuries.

Prevention of ulnar nerve injury during fixation of supracondylar fractures in children by ‘flexion–extension cross-pinning’ technique

No consensus exists concerning the best pin configuration for displaced supracondylar fractures of the humerus in children. Although cross-pinning is the most stable biomechanically, this configuration may cause iatrogenic ulnar nerve palsy. For the last 7 years, we have been using a three-pin fixation technique with insertion of two K wires from the lateral side (elbow in full flexion) and the third wire through the medial side (elbow in full extension). We used this technique in 67 displaced supracondylar fractures without any complications related to the ulnar nerve. The technique provides excellent stability and eliminates the risk of iatrogenic ulnar nerve palsy.

Loss of Pin Fixation in Displaced Supracondylar Humeral Fractures in Children

Although the results are generally good following pin fixation of supracondylar humeral fractures in children, occasionally there is postoperative displacement. The purposes of the present study were to identify the causes leading to loss of fixation after pin fixation and to present methods for prevention. We evaluated 322 displaced supracondylar humeral fractures that had been treated with percutaneous pin fixation. We examined fracture classification, pin configuration, intraoperative alignment after fixation, change in alignment after fixation, details of additional procedures, and final radiographic and clinical outcomes. Adequate radiographs were available for 279 of the 322 fractures. Eight (2.9%) of the 279 fractures were associated with postoperative loss of fixation; all eight were Gartland type-III fractures. Seven of these eight fractures initially had been treated with two lateral-entry pins, and one had been treated with two crossed pins. In patients with Gartland type-III fractures, loss of fixation was successfully avoided more often when three pins were used (with fixation being maintained in thirty-seven of thirty-seven patients) as opposed to when two lateral-entry pins were used (with fixation being maintained in thirty-five of forty-two patients) (p = 0.01). In all cases, loss of fixation was due to technical errors that were identifiable on the intraoperative fluoroscopic images and that could have been prevented with proper technique. We identified three types of pin-fixation errors: (1) failure to engage both fragments with two pins or more, (2) failure to achieve bicortical fixation with two pins or more, and (3) failure to achieve adequate pin separation (>2 mm) at the fracture site. Postoperative displacement following pin fixation of supracondylar humeral fractures in children is uncommon. In the present series, loss of fixation was most likely to occur when Gartland type-III fractures were treated with two lateral-entry pins. There were no failures when three pins were used. In all cases of failure, there were identifiable technical errors in pin placement. Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.

Biomechanical comparison of different pin configurations during percutaneous pinning for the treatment of proximal humeral fractures

We investigate the influence on fracture stability of different pin configurations during percutaneous pinning for the treatment of proximal humeral fractures. We performed a matched-paired study of 18 pairs of adult fresh-frozen humeri (36 humeri), which were divided into 4 groups. A 2-part surgical neck fracture model was used in all humeri, and 4 terminal threaded pins (2.5 mm in diameter) were used for fixation. Parallel-type pinning (box type) was carried out in 2 groups, and convergent-type pinning (fan-shaped type) was used in the other 2 groups. For each specimen, both anti-shear ultimate load and anti-torsion ultimate load were measured. There was no statistical difference between the parallel pin construct and convergent construct with regard to anti-shear resistance (P = .73). However, the parallel pin construct had a significant advantage over the convergent construct regarding anti-torsion resistance. The parallel pin construct has better torsional stability when 1 cm is used for the pin-to-pin distance. We suggest that parallel pin fixation should be applied whenever possible.

Genetic Algorithm Application for Burnable Poison Placement in PWRs with Optimized UO2/Gd2O3 Fuel Pin Configurations

In this paper, an efficient genetic algorithm has placed burnable poisons (BPs) into all of the fresh fuel positions in the core employing the optimized BP configurations and techniques developed in two previous papers. Of importance was the previous development of a Kinf filter, which greatly reduced the computational time. The Kinf filter eliminated many of the invalid genotypes/phenotypes before making a precise core depletion analysis. An extensive BP library was generated by the CASMO-4/TABLES-3 codes. The process was automated with a user-friendly program developed for this purpose. The BPs were vendor UO2/Gd2O3 fuel assembly designs used in a reference Three Mile Island Unit 1 core. The optimized UO2/Gd2O3 fuel pin configurations have small residual binding at end of cycle (EOC), and BP loading optimization results with 97.2 ppm soluble boron at EOC while it was 94.4 ppm with the available vendor designs. The result was that optimized UO2/Gd2O3 fuel pin configurations were developed with unique self-shielding properties and residual binding that also provided a 6.89% reduction in the total required Gd amount, providing extra savings in fuel cost.

Biomechanical Analysis of Pinning Techniques for Pediatric Supracondylar Humerus Fractures

Closed reduction and percutaneous pin fixation is the recommended treatment of displaced (Gartland types 2 and 3) supracondylar humerus fractures. The need for a medial pin for maximal stability remains controversial. The purpose of this study was to develop a model of supracondylar humerus fractures simulating medial column comminution and to evaluate the torsional stability of various pin configurations recommended in the current literature. Transverse cuts were made in synthetic humeri with a wedge taken from the medial aspect of the proximal fracture fragment in one half of the specimens to simulate medial column comminution. Each fracture was then reduced and fixed with 1 of 4 pin configurations using 0.062 in K-wires. The fixed specimens were then subjected to a torsional load producing internal rotation of the distal fragment. Rotation in degrees and the corresponding torque was recorded for statistical analysis. Specimens with the medial wedge removed demonstrated less torsional stability than their identically fixed counterparts with the intact medial column. In specimens with the intact medial column, the greatest torsional stability was achieved with the 2 lateral divergent and medial cross pin configuration followed by 3 lateral pins, then standard crossed pins with 2 lateral divergent pins demonstrating the least torsional stability. For the medial comminution group the 2 lateral, 1 medial pin construct again had the greatest torsional stability and 2 lateral pins the least. The standard crossed pin and 3 lateral pin constructs were not significantly different in the presence of medial comminution. In a synthetic humerus model of supracondylar humerus fractures, medial comminution was shown to reduce torsional stability significantly in all pin configurations. There was no statistical difference in torsional stability between 3 lateral pins and standard crossed pins in specimens with medial comminution.

Lateral versus crossed wire fixation for displaced extension supracondylar humeral fractures in children

Reduction and percutaneous pin fixation is widely accepted treatment for displaced humeral supracondylar fractures in children, but the best pin configuration is still debatable. This study examined the outcome for crossed and lateral pins placement in type IIB and III supracondylar humeral fractures. Clinical notes and radiographs of 131 children with an average age of 6 years were retrospectively reviewed. Lateral pins fixation was used in 66 children and crossed wires in 65. The groups were similar with regard to gender, age, follow-up, severity of displacement and number of closed/open reductions. There was no statistical difference between the two groups either clinically or radiologically in the quality of outcome. However, postoperative ulnar nerve injuries occurred in 6% of patients treated with crossed wire fixation, whilst none of the group with pins inserted laterally suffered this complication. We recommend fixation of displaced humeral supracondylar fractures with two or three lateral pins inserted parallel or in a divergent fashion. This method of fixation gives similar results to crossed wires but prevents iatrogenic ulnar nerve injuries.

Analysis of pin characteristics for a variable geometry mold

The sheet metal industry has considered the use of a variable geometry mold for years. Its application to the vacuum forming of plastic sheets, however, is rather new. One significant problem is the dimpling effect resulting from the discrete nature of the mold surface. The purpose of this research is to determine the most appropriate pin type and configuration for a viable variable geometry mold, considering the dimpling effect and other quality issues. Through analyzing the consequences of several pin types and configurations, we conclude that a flat top, square pin in a closed-pack configuration is the most appropriate option.

SimArray: a user-friendly and user-configurable microarray design tool

BackgroundMicroarrays were first developed to assess gene expression but are now also used to map protein-binding sites and to assess allelic variation between individuals. Regardless of the intended application, efficient production and appropriate array design are key determinants of experimental success. Inefficient production can make larger-scale studies prohibitively expensive, whereas poor array design makes normalisation and data analysis problematic.ResultsWe have developed a user-friendly tool, SimArray, which generates a randomised spot layout, computes a maximum meta-grid area, and estimates the print time, in response to user-specified design decisions. Selected parameters include: the number of probes to be printed; the microtitre plate format; the printing pin configuration, and the achievable spot density. SimArray is compatible with all current robotic spotters that employ 96-, 384- or 1536-well microtitre plates, and can be configured to reflect most production environments. Print time and maximum meta-grid area estimates facilitate evaluation of each array design for its suitability. Randomisation of the spot layout facilitates correction of systematic biases by normalisation.ConclusionSimArray is intended to help both established researchers and those new to the microarray field to develop microarray designs with randomised spot layouts that are compatible with their specific production environment. SimArray is an open-source program and is available from .

Development of enriched Gd-155 and Gd-157 burnable poison designs for a PWR core

In this study, a genetic algorithm developed by the authors was applied to design the optimal enriched Gd-155 and Gd-157 burnable poisons in a reference PWR TMI-1 core. The CASMO-4/TABLES/SIMULATE-3 package calculated the neutronic performance of the enriched UO 2/Gd 2O 3 fuel pin configurations. These configurations included different fractions of neutron absorbing isotopes Gd-155 and Gd-157, and 100 w/o enriched Gd-155 designs. Fuel cost analysis was performed to evaluate the economical benefits of these optimized enriched gadolinium designs. The break-even point for unit Gd-155 enrichment cost was determined to be around ∼$30/gram-Gd-155 with current unit cost scenario. The projected savings were 3.13% in gross and 2.08% in net compared to total fuel cycle cost of a reference TMI-1 core loading, if all of the 68 feed assemblies would be replaced with the optimized designs.

DBEM and FEM analysis on non-linear multiple crack propagation in an aeronautic doubler-skin assembly

The performance of a riveted patch repair, applied on a cracked panel, is simulated by using both a commercially available boundary element code (BEASY) and a finite element code (ANSYS). A two-dimensional stress analysis on a single-sided repaired configuration is performed by both methodologies; consequently, the occurrence of out-of-plane bending and its effect on the through-thickness stress intensity factor (SIF) variation is neglected. The connection between the two layers (patch and panel) is realised by 32 rivets, with through-cracks initiated on the most loaded holes. Special elements are used to model the crack: discontinuous elements in the dual boundary element method (DBEM) approach or quarter point elements in the finite element method (FEM) approach. Different loading configurations are considered depending on the presence of a biaxial or uniaxial remote load and the non-linear hole/rivet contact is simulated by gap elements. The most stressed skin holes are highlighted, and the effect of a through crack from such holes is analysed in terms of SIFs and stress redistribution. The accuracy in SIFs assessment by DBEM and FEM and the respective computational and pre-processing efforts are determined. Such a two-dimensional analysis allows us a straightforward pre-processing phase, and very short run times are needed. A peculiar arrangement of the pin configuration in the DBEM analysis allows us to take into account the real in-plane plate stiffness and the transversal pin stiffness, even in a 2D analysis (this is straightforward by using FEM).

Two-part surgical neck fractures of the humerus: Mechanical analysis of the fixation with four Shanz-type threaded pins in four different assemblies

The configuration of percutaneous pinning may affect the stability of the fixation of 2-part surgical neck fractures of the humerus. In this investigation, the mechanical properties of four different pin configurations were analyzed by use of 36 fresh-frozen swine femora as an experimental model. The bones were selected according to previously established morphologic parameters. A transverse osteotomy was made in the proximal metaphyseal region of the bone, and the pins were inserted according to the selected configuration (group 1, four ascending parallel pins; group 2, three ascending parallel pins and one descending intersecting pin; group 3, two ascending parallel pins and two descending parallel intersecting pins; and group 4, two ascending parallel pins and two descending converging pins, on different planes [two by two]). The assemblies were subjected to an axial load of up to 1500 N in a universal testing machine, simulating a varus stress. The parameters studied were the maximum load supported and corresponding deformation, load and deformation at the limit of proportionality, rigidity, and resilience. The results showed that all configurations were sufficiently strong, but the maximum load and load at the limit of proportionality were significantly higher (P < .05) in groups 3 and 4 (1314 and 1377 N and 950 and 923 N, respectively) than in groups 1 and 2 (1104 and 1033 N and 738 and 777 N, respectively). Rigidity was significantly higher in group 3 than in groups 1 and 2 but not in group 4. Resilience, maximum deformation, and deformation at the limit of proportionality were not significantly different between groups. We conclude that the experimental model used was reliable for the purpose of the study and that any of the configurations studied would be adequate for the percutaneous fixation of 2-part surgical neck fractures of the humerus but group 3 configuration would be the most efficient.

Amorphous and ‘micromorph’ silicon tandem cells with high open-circuit voltage

Abstract For amorphous and ‘micromorph’ silicon multi-junction solar cells, we have developed tunnel recombination junctions consisting of two microcrystalline doped layers with a defect-rich interface. While the solar cells performed reasonably well under AM 1.5 light, we found in spectral response measurements that the first deposited cell of tandem structures in nip and pin configuration was apparently leaking under low light conditions. Insertion of a thin protection layer of n-type amorphous silicon solved this issue, and led to an increase in open-circuit voltage. Voltages as high as 1.76 V have been obtained for a-Si/a-Si pinpin tandem cells.

Complications and Timing of Follow-up After Closed Reduction and Percutaneous Pinning of Supracondylar Humerus Fractures

The purpose of this study was to evaluate the need for clinical evaluation with radiographs within 10 days of closed reduction and percutaneous pinning for the treatment of displaced supracondylar humerus fractures. Between May 1 and December 31, 2001, the authors evaluated the complications with closed reduction and percutaneous pinning of 104 displaced supracondylar humerus fractures. Fifty-two of the patients had the initial follow-up examination with radiographs 10 days or less after pinning; the other 52 patients had the initial follow-up examination with radiographs either after 10 days or on the day of pin removal. The overall complication rate for the series was 7.7% (8/104). All eight complications were in type III fractures. The early follow-up group had six complications; the late follow-up group had two complications. Baumann's angle, lateral humerocapitellar angle, and lateral rotational percentage were not significantly different between the two groups. The only variable tested that was associated with a complication was pin configuration. No association between late follow-up and complications was identified. The authors conclude that clinical and radiographic evaluation of routine displaced supracondylar humerus fractures requiring closed reduction and percutaneous pinning may be safely delayed until pin removal.