Tip Apex Research Articles

Numerical and Physical Modeling of the Effect of the Cone Apex Angle on the Penetration Resistance in Coarse-Grained Soils

The tip shape of penetrometers and piles has an important influence on the soil resistance mobilized during penetration. Blunt or flat tips typically generate greater penetration resistances, which can lead to refusal during in-situ testing and pile driving in the field. Results are presented from numerical and experimental investigations on probes with conical tips of varying apex angles to quantify the effect of the apex angle on the mobilized penetration resistance and associated failure mechanisms. Discrete element modeling (DEM) simulations were performed in unconfined and confined (i.e., stress-controlled) specimens to model shallow and deep penetration conditions, respectively. Centrifuge penetration tests were performed by quasi-statically advancing an instrumented probe to a depth-to-probe-diameter ratio of 16.7. The numerical and experimental results indicate that at shallow depths, the sharper tips mobilize smaller penetration resistances. In deep penetration conditions, the changes in penetration resistance with tip apex angle are less pronounced. Based on the results of the two investigations and values reported in the literature, a relationship characterizing the functional form between tip apex angle and normalized penetration resistance is proposed. A mesoscale analysis of the DEM simulation shows differences in the failure mechanisms induced by sharp and blunt tips: the zone where large particle displacements and stress changes occur is large and located below the tip for penetration with blunt tips, whereas the zone is smaller and located both laterally and below the tip for sharp tips.

ESR-STM on diamagnetic molecule: C60 on graphene

Electron Spin Resonance-Scanning Tunneling Microscopy (ESR-STM) of C60 radical ion on graphene is a first demonstration of ESR-STM on diamagnetic molecules. ESR-STM signal at gaverage=2.0±0.1 was measured in accordance with macroscopic ESR of C60 radical ion. The ESR-STM signal was bias voltage dependent, as it reflects the charge state of the molecule. The signal appears in the bias voltage which enables the ionization of the lowest unoccupied molecular orbital (LUMO) – creation of radical anion, and the highest occupied molecular orbital (HOMO) – creation of a radical cation of the C60 molecule when it deposited on graphene. In parallel, ESR-STM signal at gaverage=1.7±0.1 was ascribed to Tungsten oxide (WO3) at the tip apex. In several experiments, triplet spectrum was observed, and we ascribed their origin to zero-field splitting of doubly ionized C120O-2 dimer, as argued in previous ESR experiments of C60 samples. Second possibility is hyperfine coupling with two 13C nuclei. In addition, we further validate the interference mechanism previously suggested for ESR-STM noise spectroscopy. The ability of ESR-STM to observe ESR of diamagnetic molecules in parallel with observing their electronic structure, provides a general single molecule identification technique.

Intramolecular Force Mapping at Room Temperature.

Acquisition of dense, three-dimensional, force fields with intramolecular resolution via noncontact atomic force microscopy (NC-AFM) has yielded enormous progress in our ability to characterize molecular and two-dimensional materials at the atomic scale. To date, intramolecular force mapping has been performed exclusively at cryogenic temperatures, due to the stability afforded by low temperature operation, and as the carbon monoxide functionalization of the metallic scanning probe tip, normally required for submolecular resolution, is only stable at low temperature. In this paper we show that high-resolution, three-dimensional force mapping of a single organic molecule is possible even at room temperature. The physical limitations of room temperature operation are overcome using semiconducting materials to inhibit molecular diffusion and create robust tip apexes, while challenges due to thermal drift are overcome with atom tracking based feedforward correction. Three-dimensional force maps comparable in spatial and force resolution to those acquired at low temperature are demonstrated, permitting a quantitative analysis of the adsorption induced changes in the geometry of the molecule at the picometer level.

Intertrochanteric femur fractures: a current concepts review

Intertrochanteric fractures are common injuries around the hip, especially among the elderly. With the rising incidence of these injuries, they are expected to double by 2050. Incidence rates are higher in females than males and in white patients than black African patients. Osteoporosis weakens the local trochanteric anatomic support leading to an increased susceptibility to fractures. Disruption of the posteromedial calcar region results in fracture instability. Optimal lag screw position and fracture reduction are significant determinants for postoperative outcomes. The tip apex distance and reduction criteria determine lag screw cut-out risk and fracture reduction quality, respectively. A calcar-referenced tip apex distance is comparable if not better than the tip apex distance in predicting cut-out risk. Optimal reduction is in slight valgus, a positive medial cortex apposition and smooth anterior cortex apposition. High mortality rates are observed with non-surgical treatment. Surgical management is therefore the gold standard for intertrochanteric fractures. Treatment options are categorised into extramedullary fixation, intramedullary fixation and proximal femur replacement. They include the dynamic hip screw (DHS), cephalomedullary nails (CMN) and arthroplasty. Although still in use, the proximal femur locking plate is falling out of favour due to high complication rates. Fracture stability and pattern influence the treatment choice. There is, however, a growing use of CMNs which has been attributed to surgical training background. Modification of older CMN designs has improved treatment outcomes. Systematic meta-analyses of randomised controlled trials (RCTs) do not show superiority of one treatment option over another; therefore, there is no consensus on the best treatment choice. The proximal femur nail antirotation (PFNA) has better outcomes compared to other fixation options with respect to intraoperative blood loss and Harris hip scores. As a group, CMNs have a better 120-day postoperative quality of life compared to the DHS. No significant difference in complications has been found between treatment options. In light of the anticipated increased incidence of intertrochanteric fracture, more work is needed in planning national resource allocation, devising preventative methods and improving clinical interventions in South Africa. Level of evidence: Level 5

Shape optimization of a meniscus-adherent nanotip.

A soluble tip can dissolve into a tip with curvature when partially immersed in a liquid. This process has been used in the manufacture of sophisticated tips. However, it is difficult to observe the dissolution process in the laboratory, and the dissolution mechanisms at the nanoscale still need to be better understood. Here we utilize molecular dynamics simulations to study the dissolution process of a meniscus-adherent nanotip. The tip apex curvature radius reaches its minimum in the intermediate state. The shape of this state is defined as the optimized shape, which can be used as the termination criterion in applications. In addition, the shape of one optimized tip can be well-fitted to a double-Boltzmann function. The upper Boltzmann curve of this function forms via the competition between the chemical potential influence and the intermolecular forces, while the formation of the lower Boltzmann curve is controlled by the chemical potential influence. The parameters of the double-Boltzmann function are strongly correlated with the nanotip's initial configuration and dissolubility. A shape factor ξ is proposed to characterize the sharpness of optimized tips. Theory and simulations show that optimized tips possess a greater ability to shield the capillary effect than common tips. Our findings elucidate the meniscus-adherent nanotip's dissolution process and provide theoretical support for nano-instrument manufacture.

Proposal of a modified tip apex distance for prediction of lag screw cut-out in trochanteric hip fractures.

Lag screw cut-out is a serious complication of dynamic hip screw fixation of trochanteric hip fractures. The lag screw position has been acknowledged as one of the important factors affecting the lag screw cut-out. We propose a modification of the Tip Apex Distance (TAD) and hypothesise that it could improve the reliability of predicting lag screws cut-out in these injuries. A retrospective study was conducted for hip fracture entries in the period from Jan 2018 to July 2022. A hundred and nine patients were suitable for the final analysis. The modified TAD was measured in millimetres based on the sum of the traditional TAD in the lateral view and the net value of two distances in the AP view, the first distance is from the tip of the lag screw to the opposite point on the femoral head along the axis of the lag screw while the second distance is from that point to the femoral head apex. The first distance is a positive value, whereas the second distance is positive if the lag screw is superior and negative if inferior. A receiver operating characteristic curve was used to evaluate the reliability of the different parameters assessing the lag screw position within the femoral head. Reduction quality, fracture pattern as per the AO/OTA classification, TAD, Calcar Referenced TAD, Axis Blade Angle, Parker's ration in the AP view, Cleveland Zone 1, and modified TAD were statistically associated with lag screw cut-out. Among the tested parameters, the modified TAD had 90.1% sensitivity and 90.9% specificity for lag screw cut-out at a cut-off value of 25mm with a P-value<0.001. The modified TAD had the highest reliability in the prediction of lag screw cut-out. A value ≤25mm could potentially protect against lag screw cut-out in trochanteric hip fractures.

Nanoscale probing of local dielectric changes at the interface between solids and aqueous saline solutions.

The mobility of dissolved ions and charged molecules at interfaces underpins countless processes in science and technology. Experimentally, this is typically measured from the averaged response of the charges to an electrical potential. High-resolution Atomic Force Microscopy (AFM) can image single adsorbed ions and molecules at solid-liquid interfaces, but probing the associated dynamics remains highly challenging. One possible strategy is to investigate the response of the species of interest to a highly localized AC electric field in an approach analogous to dielectric spectroscopy. The dielectric force experienced by the AFM tip apex is modulated by the dielectric properties of the sample probed, itself sensitive to the mobilities of solvated charges and dipoles. Previous work successfully used this approach to quantify the dielectric constant of thin samples, but with limited spatial resolution. Here we propose a strategy to simultaneously map the nanoscale topography and local dielectric variations across a range of interfaces by conducting high-resolution AFM imaging concomitantly with electrical AC measurements in a multifrequency approach. The strategy is tested over a 500 MHz bandwidth in pure liquids with different dielectric constants and in saline aqueous solutions. In liquids with higher dielectric constants, the system behaves as inductive-resistive-capacitive but the adjunction of ions removes the inductive resonances and precludes measurements at higher frequencies. High-resolution imaging is demonstrated over single graphene oxide (GrO) flakes with simultaneous but decoupled dielectric measurements. The dielectric constant is consistent and reproducible across liquids, except at higher salt concentrations where frequency-dependent effects occur. The results suggest the strategy is suitable for nanometre-level mapping of the dielectric properties of solid-liquid interfaces, but more work is needed to fully understand the different physical effects underpinning the measurements.

Functional Outcome of Tip Apex Distance in Predicting Implant Failure in Intertrochanteric Fracture Femur Treated with Dynamic Hip Screw

Objective: To evaluate the importance of tip apex distance in implant failure in intertrochanteric fracture femur treated with Dynamic hip screw, so that optimum tip apex distance should maintain to decrease the implant failure in intertrochanteric fracture femur treated with DHS. Study Design: It was a descriptive cross sectional study. Study Setting and Duration: Patients were selected from orthopedic unit of Nishtar Hospital, Multan, from July 2020 to June 2021. Methodology: All patients meeting the inclusion criteria who presented with a femur fracture were included in the analysis. SPSS version 24.0 was used to analyse the data. Quantitative data analysis was done using means and standard deviations like age and tip apex distance. Categorical variables like gender, functional outcome and implant failure was calculated and presented as frequency and percentage. Results: A total of 81 patients with mean age of male patients were 38.51 and SD was 11.79, similarly in female patients mean age was 41.87 and SD 11.60. Mean tip apex distance in male was 16.08 and SD 8.49, in female mean tip apex distance was 15.40 and SD 9.368. Tip Apex distance was ≤ 25 cm in 61 (75.3%) patients and &gt;25 cm in 12 (24.7%) patients. As concern to the outcome variable (implant failure) 12 (14.8%) patients were having implant failure and 69 (85.2%) patients were having successful outcomes. Practical implication: The use of Dynamic Hip Screw in Intertrochanteric Fracture Femur treated would show improved clinical results and fewer hardware failures Conclusion: Tip Apex distance is a valuable measurement in dynamic hip screw fixation of Intertrochanteric fracture femur. Keywords: Fracture, Femur, Tip Apex Distance, Dynamic Hip Screw, Implant Failure, Orthopedic

Does matching degree matter for proximal femoral intramedullary nail on reoperation rate in intertrochanteric fractures?

IntroductionPrevious articles reported on the tip–apex distance, lag screw placement, fracture pattern, reduction quality, osteoporosis and other factors associated with second surgery. The current study focused on investigating the association of the matching degree between proximal femoral intramedullary nail and femoral medullary cavity on reoperation rate.Patients and methodsA retrospective cohort study was conducted. It included patients with intertrochanteric fracture who were treated with proximal femoral anti-rotatory intramedullary nail (PFNA) between January 2016 and April 2021. The gap between the intramedullary nail and the femoral medullary cavity was equal to the difference in diameter between the two. According to the gap size, all patients were divided into three groups, as follows: high-matching group: gap ≤ 2 mm; middle-matching group: 2 < gap < 4 mm; and low-matching group: gap ≥ 4 mm. The mean gap was measured through standard images. The primary observational index was whether the reoperation was needed, and secondary observational indexes included operative time, length of hospital stay. Patient characteristics were recorded, as follows: age, sex, follow-up time, fracture pattern, reduction grade and length of intramedullary nail.ResultsA total of 203 eligible patients were recorded, including 78 males (38.4%) and 125 females (61.6%). They had a mean age of 77.8 ± 9.9 years old and an average follow-up time of 58.1 ± 24.0 weeks. Twenty-seven patients (13.3%) needed a second operation. Coxa varus combined with screw cutting was the most common reason for reoperation (11 cases). Unstable fracture pattern with poor reduction grade tended to contribute to reoperation, whose odds ratio (OR) was 6.61 (95% confidence interval [CI], 1.98–22.09; P = 0.002). The three groups had 11 cases (13.7%), 12 cases (13.8%) and 4 cases (11.1%) of reoperation, respectively, and logistic regression showed no significant association was noted between matching degree of intramedullary nail and reoperation rate.ConclusionsThe matching degree between proximal femoral intramedullary nail and femoral medullary cavity did not seem to be an important factor for reoperation, which offered more options of intramedullary nail size intraoperatively and reduced implants stock from inventory.

Precise atom manipulation through deep reinforcement learning

Atomic-scale manipulation in scanning tunneling microscopy has enabled the creation of quantum states of matter based on artificial structures and extreme miniaturization of computational circuitry based on individual atoms. The ability to autonomously arrange atomic structures with precision will enable the scaling up of nanoscale fabrication and expand the range of artificial structures hosting exotic quantum states. However, the a priori unknown manipulation parameters, the possibility of spontaneous tip apex changes, and the difficulty of modeling tip-atom interactions make it challenging to select manipulation parameters that can achieve atomic precision throughout extended operations. Here we use deep reinforcement learning (DRL) to control the real-world atom manipulation process. Several state-of-the-art reinforcement learning (RL) techniques are used jointly to boost data efficiency. The DRL agent learns to manipulate Ag adatoms on Ag(111) surfaces with optimal precision and is integrated with path planning algorithms to complete an autonomous atomic assembly system. The results demonstrate that state-of-the-art DRL can offer effective solutions to real-world challenges in nanofabrication and powerful approaches to increasingly complex scientific experiments at the atomic scale.

Fabrication of tungsten tips with controllable shape by a two-step rapid reciprocating electrochemical etching method.

Traditional electrochemical etching methods for the needle of a liquid metal ion source (LMIS) easily produce an exponential profile with an uncontrollable tip length and apex radius. Meanwhile, a ledge forms between the needle tip and the needle rod under the etching of the meniscus, which becomes an obstacle for the flow and replenishment of the liquid metal. This paper proposed a two-step rapid reciprocating etching method, which aims to fabricate LMIS tungsten needles with controllable tip length and apex radius, and also with a smooth transition region between the needle tip and the needle rod. In the first step of rough machining, the needle rapidly reciprocates up and down in the electrolyte and rotates to produce a uniform conical profile. However, an ellipsoidal residual portion is generated concomitantly at the needle tip. In the second step of finish machining, the needle shifts down for a given distance and continues to reciprocate until the sharp tip is formed. The tip length fabricated varied from 0.59 to 5.53mm at different reciprocating strokes. The apex radius ranged from 0.3 to 0.7 µm, and can also be increased to 2 µm by extra reciprocate etching in the electrolyte to meet the LMIS working requirement. A variable named transitivity was defined to quantitatively describe the smoothness of the region between the tip and rod during the etching process. The experimental results showed that a rotation speed of 600 rpm combined with a reciprocating speed of 0.5 mm/s can significantly improve the transitivity of the needle. Those fabricated needle tips have been tested for the indium LMIS and the maximum emission current of the needle tip reached 12 µA.

Unveiling the Decisive Factor for the Sharp Transition in the Scanning Tunneling Spectroscopy of a Single Nickelocene Molecule.

Scanning tunneling microscopy (STM) has been utilized to realize the precise measurement and control of local spin states. Experiments have demonstrated that when a nickelocene (Nc) molecule is attached to the apex of an STM tip, the dI/dV spectra exhibit a sharp or a smooth transition when the tip is displaced toward the substrate. However, what leads to the two distinct types of transitions remains unclear, and more intriguingly, the physical origin of the abrupt change in the line shape of dI/dV spectra remains unclear. To clarify these intriguing issues, we perform first-principles-based simulations on the STM tip control process for the Cu tip/Nc/Cu(100) junction. In particular, we find that the suddenly enhanced hybridization between the d orbitals on the Ni ion and the metallic bands in the substrate leads to Kondo correlation overwhelming spin excitation, which is the main cause of the sharp transition in the dI/dV spectra observed experimentally.

Mean Tip Apex Distance in Patients undergoing Dynamic Hip Screw Fixation for Pertrochanteric Fractures without using Traction Table: A Descriptive Cross-sectional Study.

Dynamic Hip Screw fixation has shown to be equally effective compared to cephalomedullary nailing. The effectiveness of dynamic hip screw fixation for pertrochanteric fractures without using traction table is not well investigated. This study aimed to find out the mean tip apex distance in patients undergoing dynamic hip screw fixation for pertrochanteric fractures without using traction table. A descriptive cross-sectional study was conducted among patients undergoing dynamic hip screw fixation for pertrochanteric fractures without using traction table between 1 September 2021 and 30 June 2022, after getting approval from institutional review committee (Reference number: IRC-2021-08-23-02). All patients undergoing dynamic hip screw fixation for pertrochanteric fractures without using traction table were included in the study. Patients with pre-existing ipsilateral or contralateral hip deformity, contra-lateral hip prosthesis, bilateral hip fractures, and history of prior ipsilateral hip surgeries were excluded. Point estimate and 95% confidence interval were calculated. Among 45 patients, the mean tip apex distance was 20.45±6.13 mm (18.66-22.24 mm, 95% Confidence Interval). Among 45 patients, 24 (53.33%) were males and 21 (46.66%) were females. The average age of the participants was 67.75±21.33 years. The mean tip apex distance in patients undergoing dynamic hip Screw fixation for pertrochanteric fractures without using traction table was similar to that reported in other international studies. fracture fixation; hip fractures; operating tables.

Outcomes of Suturing Triangular Shaped Trabeculectomy Flap Using Single Versus Double Suture Techniques

Background: A gold standard surgical technique, trabeculectomy is used in the management of glaucoma which is not controlled medically to lower the intraocular pressure (IOP) by creating a conduit via the sclera via which aqueous humor passes into the subconjunctival space through the anterior chamber. Objective: This study assesses the reduction in intraocular pressure (IOP) with two suturing techniques during trabeculectomy with a triangular shaped scleral flap. Method: This study was carried out from January 2019 to June 2019 at BHY Hospital, Karachi and engaged patients belonging to either gender between 40 to 60 years of age. Patients included had primary open angle glaucoma with IOP &gt; 24 mmHg despite full medical treatment. Patients having other types of glaucoma or previous history of undergoing trabeculectomy were excluded from the study. Trabeculectomy with triangular shaped scleral flap was performed on patients of both the groups with the difference being the number of sutures placed and their site. In group A, flap was approximated using a single suture, applied at the apex of the triangular tip, whereas two sutures were passed in group B on each side of the triangle close to the flap apex. Results: The study comprised a total of twenty-four patients divided in two equal groups. Mean age was 49.3±3.61 years. Mean pre-operative IOP in all the patients was 26.9±1.48 mmHg whereas post-operative mean IOP at the end of follow up was 14.0±2.08mmHg in group A and 15.1±1.67mmHg in group B patients (p = 0.181). Two patients of group A reported&#x0D; hypotony in the immediate postoperative period which was managed conservatively where as one patient from group A and one patient from group B required revision surgery owing to episcleral fibrosis. Conclusion: Both techniques were found to be equally effective for lowering the IOP with similar minimal risk profile.

Clinical analysis of extended PFNA combined with MIPPO plate for reconstruction of lateral wall in treatment of AO-A3.3 intertrochanteric fracture

To compare the clinical efficacy of lengthened proximal femoral nail anti-rotation(PFNA) combined with minimally invasive percutaneous plate osteosynthesis(MIPPO) and common PFNA in the treatment of AO-A3.3 intertrochanteric fracture. The clinical data of 58 patients with AO-A3.3 intertrochanteric fracture treated from January 2015 to April 2020 were retrospectively analyzed. Among them, 27 patients were treated with extended PFNA + MIPPO plate to reconstruct the lateral wall (group A), and 31 patients were treated with closed reduction and PFNA fixation (group B). The bleeding volume, operation time, femoral neck length and tip apex distance(TAD), fracture healing time and postoperative complications were observed and compared between two groups. Harris score was used to evaluate hip joint function 10 months after operation. All patients were followed up for 12 to 28 months. The incision healed well after operation. The bleeding volume and operation time of group A were significantly more than that of group B (P<0.05), and the fracture healing time of group A was significantly less than that of group B(P<0.05). There was no significant difference in the length of femoral neck between two groups at 2 days after operation(P>0.05). The length of femoral neck at 6 months after operation in each group was shorter than that at 2 days after operation(P<0.05), and the shortening of femoral neck at 6 months after operation in group B was significantly shorter than that in group A(P<0.05). There was no significant difference in TAD values between two groups at the same time point(P>0.05) at 2 days and 6 months after operation. There was no significant difference in TAD values between 2 days and 6 months after operation(P>0.05). The incidence of complications in group B was significantly higher than that in group A(P<0.05). The Harris scores of hip joint function in group A were higher than those in group B 10 months after operation (P<0.05). Compared with the treatment of AO-A3 femoral intertrochanteric fracture with closed reduction and PFNA fixation, the lengthened PFNA combined with MIPPO small plate for reconstruction and fixation of the lateral wall can promote the fracture healing, improve the patient's functional recovery, and significantly reduce the complications.

U-blade gamma 3 vs. gamma 3 nails for intertrochanteric hip fracture: Meta-analysis.

Intertrochanteric fracture is a growing problem in the traumatology department. The use of intramedullary devices has increased, representing the first treatment option in intertrochanteric fractures. U-Blade devices appeared to avoid rotation of the femoral head over the femoral neck. The aim of this study was to conduct a meta-analysis of the surgical treatment of intertrochanteric fractures comparing in terms of safety and efficacy the U-Blade Gamma 3 nail vs. the conventional Gamma 3 nail. A literature search for intertrochanteric fracture 31A1-31A3 according to the AO foundation/orthopaedic trauma association (AO/OTA) classification was performed. Baseline characteristics of each article were obtained; radiological outcomes were tip apex distance (TAD), sliding distance (mm), cut-out rate, and lateralization rate. Surgery time (min) was also recorded. A meta-analysis was performed with ReviewManager 5.4. Five retrospective studies (n = 993 patients) were included. With respect to TAD and sliding distance, there were no differences between two groups [mean difference (MD) 0.47, 95% confidence interval (CI), -0.46 to 1.40] and (MD 0.39, 95% CI, 0.13-0.66). The cut-out rate and lateralization rate did not show differences between two groups (p > 0.05). Finally, surgery time was significantly higher in the U-Blade Gamma 3 group (MD -4.84, 95% CI, -7.22 to -2.46). The use of U-Blade Gamma 3 did not show significant differences in the radiological results compared with the conventional Gamma 3 nail.

An innovative scoring system for predicting an excellent Harris hip score after proximal femoral nail anti-rotation in elderly patients with intertrochanteric fracture

Typically, intramedullary and extramedullary devices are used to treat elderly with intertrochanteric fractures. The majority of previous research has focused on the association between surgical factors and mechanical failure after internal fixation. There is, however, limited evidence to demonstrate the association between functional outcomes after proximal femoral nail anti-rotation (PFNA) fixation and the non-surgical factors such as patient’s comorbidities. The aim of this study is to determine the predictive factors associated with excellent outcome, as well as to develop an integrated scoring system to predict the outcome after PFNA fixation in elderly patients with an intertrochanteric fracture. A retrospective study was conducted between January 2012 and December 2018. Elderly patients with low-energy intertrochanteric fractures who underwent PFNA fixation and at least a year of follow-up were recruited. Demographics, comorbidities, cognitive status, time to operation, and surgical parameters of the patients were all identified. Excellent and non-excellent outcomes were assessed by Harris Hip Score (HHS) after a one-year follow up. Regression analysis was used to determine the predictors for an excellent functional outcome. A new integrated scoring system (ISSI; Integrate Scoring System in elderly patients with Intertrochanteric fracture) was developed and validated. 450 elderly patients were randomly divided into two cohorts: a development (N = 225) and validation cohorts (N = 225). In this study, age < 85 years, normal weight/overweight, Charlson comorbidity index (CCI) < 6, no cognitive impairment, a modified AO/OTA 31A1.3, time to operation < 6 days, and Tip Apex Distance between 20 and 30 mm were significantly associated with an excellent outcome after PFNA fixation. The range of ISSI score was between 0 to 16 and the cut-off score of 13 was found to have the highest discriminatory power to determine the excellent functional outcome where the area of ROC was 0.85. In regards to the validation cohort, the sensitivity and specificity of ISSI score was 69% and 87%, respectively, and the AUC was 0.81. The ISSI score is effortless and practical for orthopedic surgeons for predicting an outcome after PFNA fixation in elderly patients with an intertrochanteric fracture.

Toward a better modulus at shallow indentations-Enhanced tip and sample characterization for quantitative atomic force microscopy.

Approximations of the geometry of indenting probes, particularly when using shallow indentations on soft materials, can lead to the erroneous reporting of mechanical data in atomic force microscopy (AFM). Scanning electron microscopy (SEM) identified a marked change in geometry toward the tip apex where the conical probe assumes a near linear flat-punch geometry. Polydimethylsiloxane (PDMS) is a ubiquitous elastomer within the materials and biological sciences. Its elastic modulus is widely characterized but the data are dispersed and can display orders of magnitude disparity. Herein, we compare the moduli gathered from a range of analytical techniques and relate these to the molecular architecture identified with AFM. We present a simple method that considers sub-100 nm indentations of PDMS using the Hertz and Sneddon contact mechanics models, and how this could be used to improve the output of shallow indentations on similarly soft materials, such as polymers or cells.

Outcome of unstable intertrochanteric fractures managed with Proximal Femoral Nail Anti-rotation-II: A study in elderly Nepalese population.

Introduction: The ideal implant for treating unstable intertrochanteric fracture has been controversial. Studies have shown good results with various intra-medullary nails. Likewise, Proximal Femoral Anti-rotation-II (PFNA-II) has been designed for the Asian population. But the knowledge about the outcomes of PFNA II in our particular region has been lacking. Objectives : To evaluate the radiological and functional outcome of unstable intertrochanteric fractures in elderly patients managed with PFNA-II. Methodology: This is a prospective clinical study conducted at Nobel Medical College between February 2019 and March 2021. Patients above 65 years of age with unilateral unstable intertrochanteric fracture were managed with PFNA-II. Radiological union and complications were recorded. Functional outcome was assessed on the basis of modified Harris Hip Score. Results: Twenty-nine patients were included in the final evaluation and had at least one year follow-up. Two patients (6.8%) had superficial infection. The average Tip Apex Distance (TAD) was 22.28 mm (range, 18- 28 mm). Mean modified Harris Hip Score at one year was 82.59 with good outcome in 23(79.3%) patients. Conclusion: This study showed that good clinical outcome can be obtained when radiological parameters are restored. Good intra-operative fracture reduction, and optimal positioning and length of helical blade are crucial. We believe that PFNA-II is an excellent implant to treat unstable intertrochanteric fractures in elderly patients.

Fixation stability scoring in inter-trochanteric femur fractures treated with osteosynthesis: A retrospective observational study

To find out the validity of a newly proposed fixation stability scoring system in IT fractures treated with osteosynthesis and its limitations if any.: Retrospective analysis of hospital records of patients with various types of intertrochanteric fractures treated surgically at Sri Siddhartha medical college, Tumkur from January 2021 till August 2022. The exclusion criteria were non-ambulatory patients prior to fall, non surgically treated patients, patients loosing follow up or patients who are not alive at the time of study. The scoring was done by three different observers for each patient’s immediate post operative x-ray, repeated at 1 month interval. Radiographs at the final follow up were assessed for fracture union or fixation failure. Parameters of the scoring system: 1) cortical buttress in AP view radiograph, 2) cortical buttress in lateral view radiograph, 3) Tip apex distance (TAD) of principle lag screw, 4) Entry point (in case of IM nail), 5) Location of tip of principle screw in the desired Cleveland zone. 6) Placement of Richard screw in the inferior half of neck (in case of DHS), 7) Use of additional derotation screw (DRS) (in case of DHS). Scores of all the observers showed statistically significant correlation with fixation failure rates. Results were good with the score of 7.5 and above, fair with 6.5 and above and poor when the score was below 6.5. The minimum acceptable score was 6.5 for extra-medullary devices and 7 for intra-medullary devices.: The newly proposed scoring system appears to be valid and promising intra operative guide for fixation of intertrochanteric fractures with a few limitations. Large scale multi centre prospective studies are needed in the future to support the current study or to further simplify this scoring system.