The cis-2-Dodecenoic Acid (BDSF) Quorum Sensing System in Burkholderia cenocepacia.

It has been demonstrated that quorum sensing (QS) is widely employed by bacterial cells to coordinately regulate various group behaviors. Diffusible signal factor (DSF)-type signals have emerged as a growing family of conserved cell-cell communication signals. In addition to the DSF signal initially identified in Xanthomonas campestris pv. campestris, Burkholderiadiffusible signal factor (BDSF) (cis-2-dodecenoic acid) has been recognized as a conserved DSF-type signal with specific characteristics in both signal perception and transduction from DSF signals. Here, we review the history and current progress of the research on this type of signal, especially focusing on its biosynthesis, signaling pathways, and biological functions. We also discuss and explore the huge potential of targeting this kind of QS system as a new therapeutic strategy to control bacterial infections and diseases.

BDSF Is a Degradation-Prone Quorum-Sensing Signal Detected by the Histidine Kinase RpfC of Xanthomonas campestris pv. campestris.

Diffusible signal factors (DSFs) are medium-chain fatty acids that induce bacterial quorum sensing. Among these compounds, BDSF is a structural analog of DSF that is commonly detected in bacterial species, and it is the predominant in planta quorum-sensing signal in Xanthomonas campestris. How BDSF is sensed in Xanthomonas spp. and the functional diversity between BDSF and DSF remain unclear. In this study, we generated genetic and biochemical evidence that BDSF is a low-active regulator of X. campestris pv. campestris quorum sensing, whereas trans-BDSF does not seem to be a signaling compound. BDSF is detected by the sensor histidine kinase RpfC. Although BDSF has relatively low physiological activities, it binds to the RpfC sensor with a high affinity and activates RpfC autophosphorylation to a level that is similar to that induced by DSF in vitro. The inconsistency in the physiological and biochemical activities of BDSF is not due to RpfC-RpfG phosphorylation or RpfG hydrolase. Neither BDSF nor DSF controls the phosphotransferase and phosphatase activities of RpfC or the ability of RpfG hydrolase activity to degrade the bacterial second messenger cyclic di-GMP. We demonstrated that BDSF is prone to degradation by RpfB, a critical fatty acyl coenzyme A ligase involved in the turnover of DSF-family signals. rpfB mutations lead to substantial increases in BDSF-induced quorum sensing. Although DSF and BDSF are similarly detected by RpfC, our data suggest that their differential degradation in cells is the major factor responsible for the diversity in their physiological effects. IMPORTANCE The diffusible signal factor (DSF) family consists of quorum-sensing signals employed by Gram-negative bacteria. These signals are a group of cis-2-unsaturated fatty acids, such as DSF, BDSF, IDSF, CDSF, and SDSF. However, the functional divergence of various DSF signals remains unclear. The present study demonstrates that though BDSF is a low active quorum-sensing signal, it binds histidine kinase RpfC with a higher affinity and activates RpfC autophosphorylation to the similar level as DSF. Rather than regulation of enzymatic activities of RpfC and its cognate response regulator RpfG encoding a c-di-GMP hydrolase, BDSF is prone to degradation in bacterial cells by RpfB, which effectively avoided the inhibition of bacterial growth by accumulating high concentrations of BDSF. Therefore, our study sheds new light on the functional differences of quorum-sensing signals and shows that bacteria balance quorum sensing and growth by fine-tuning concentrations of signaling chemicals.

Burkholderia cenocepacia integrates cis-2-dodecenoic acid and cyclic dimeric guanosine monophosphate signals to control virulence.

Quorum sensing (QS) signals are used by bacteria to regulate biological functions in response to cell population densities. Cyclic diguanosine monophosphate (c-di-GMP) regulates cell functions in response to diverse environmental chemical and physical signals that bacteria perceive. In Burkholderia cenocepacia, the QS signal receptor RpfR degrades intracellular c-di-GMP when it senses the QS signal cis-2-dodecenoic acid, also called Burkholderia diffusible signal factor (BDSF), as a proxy for high cell density. However, it was unclear how this resulted in control of BDSF-regulated phenotypes. Here, we found that RpfR forms a complex with a regulator named GtrR (BCAL1536) to enhance its binding to target gene promoters under circumstances where the BDSF signal binds to RpfR to stimulate its c-di-GMP phosphodiesterase activity. In the absence of BDSF, c-di-GMP binds to the RpfR-GtrR complex and inhibits its ability to control gene expression. Mutations in rpfR and gtrR had overlapping effects on both the B. cenocepacia transcriptome and BDSF-regulated phenotypes, including motility, biofilm formation, and virulence. These results show that RpfR is a QS signal receptor that also functions as a c-di-GMP sensor. This protein thus allows B. cenocepacia to integrate information about its physical and chemical surroundings as well as its population density to control diverse biological functions including virulence. This type of QS system appears to be widely distributed in beta and gamma proteobacteria.

Disruption of Quorum Sensing and Virulence in Burkholderia cenocepacia by a Structural Analogue of the cis-2-Dodecenoic Acid Signal.

Quorum sensing (QS) signals are widely used by bacterial pathogens to control biological functions and virulence in response to changes in cell population densities. Burkholderia cenocepacia employs a molecular mechanism in which the cis-2-dodecenoic acid (named Burkholderiadiffusible signal factor [BDSF]) QS system regulates N-acyl homoserine lactone (AHL) signal production and virulence by modulating intracellular levels of cyclic diguanosine monophosphate (c-di-GMP). Thus, inhibition of BDSF signaling may offer a non-antibiotic-based therapeutic strategy against BDSF-regulated bacterial infections. In this study, we report the synthesis of small-molecule mimics of the BDSF signal and evaluate their ability to inhibit BDSF QS signaling in B. cenocepacia A novel structural analogue of BDSF, 14-Me-C16:Δ2 (cis-14-methylpentadec-2-enoic acid), was observed to inhibit BDSF production and impair BDSF-regulated phenotypes in B. cenocepacia, including motility, biofilm formation, and virulence, while it did not inhibit the growth rate of this pathogen. 14-Me-C16:Δ2 also reduced AHL signal production. Genetic and biochemical analyses showed that 14-Me-C16:Δ2 inhibited the production of the BDSF and AHL signals by decreasing the expression of their synthase-encoding genes. Notably, 14-Me-C16:Δ2 attenuated BDSF-regulated phenotypes in various Burkholderia species. These findings suggest that 14-Me-C16:Δ2 could potentially be developed as a new therapeutic agent against pathogenic Burkholderia species by interfering with their QS signaling.IMPORTANCEBurkholderia cenocepacia is an important opportunistic pathogen which can cause life-threatening infections in susceptible individuals, particularly in cystic fibrosis and immunocompromised patients. It usually employs two types of quorum sensing (QS) systems, including the cis-2-dodecenoic acid (BDSF) system and N-acyl homoserine lactone (AHL) system, to regulate virulence. In this study, we have designed and identified an unsaturated fatty acid compound (cis-14-methylpentadec-2-enoic acid [14-Me-C16:Δ2]) that is capable of interfering with B. cenocepacia QS signaling and virulence. We demonstrate that 14-Me-C16:Δ2 reduced BDSF and AHL signal production in B. cenocepacia It also impaired QS-regulated phenotypes in various Burkholderia species. These results suggest that 14-Me-C16:Δ2 could interfere with QS signaling in many Burkholderia species and might be developed as a new antibacterial agent.

Femoral neck fracture osteosynthesis by the biplane double-supported screw fixation method (BDSF) reduces the risk of fixation failure: clinical outcomes in 207 patients.

INTRODUCTION: Osteosynthesis of femoral neck fractures is related up to 46% rate of complications. The novel method of biplane double-supported screw fixation (BDSF; Filipov's method) offers better stability using three medially diverging cannulated screws with two of them buttressed on the calcar. Biomechanically, the most effective component is the distal screw placed at steeper angle and supported on a large area along the distal and posterior cortex of the femoral neck following its spiral anterior curve. Thereby, BDSF achieves the strongest possible distal-posterior cortical support for the fixation construct, which allows for immediate full weight-bearing. The aim of this study was to evaluate the outcomes from the first 5-year period of BDSF clinical application. MATERIALS AND METHODS: Subject of this retrospective study were 207 patients with displaced Garden III-IV femoral neck fractures treated with BDSF. Three 7.3-mm cannulated screws were laid in two medially diverging oblique planes. The distal and the middle screws were supported on the calcar. The distal screw had additional support on the posterior neck cortex. RESULTS: The outcomes in 207 patients were analysed in 29.6 ± 16.8 months follow-up. Bone union occurred in 96.6% of the cases (males 97.6%, females 96.4%, P = 0.99). Rate of nonunion was 3.4%, including fixation failure (2.4%), pseudoarthrosis (0.5%) and nonunion with AVN (0.5%). Rate of AVN was 12.1% (males 4.8%, females 13.9%, P = 0.12). Modified Harris hip score was 86.2 ± 18.9 (range 10-100), with no significant difference between genders, P = 0.07. Older patients were admitted with significantly more comorbidities (P = 0.001), and on follow-up they were significantly less mobile (P = 0.005) and had significantly more difficulties to put socks and shoes on (P < 0.001). CONCLUSIONS: By providing additional cortical support, the novel BDSF method enhances femoral neck fracture fixation strength.

Antibiotic adjuvant activities of quorum sensing signal molecules DSF and BDSF against mature biofilms of Staphylococci.

Among promising antibiofilm compounds, quorum-sensing (QS) molecules that regulate biological processes such as biofilm formation and intra- or interspecies communication appear to be good candidates. The invitro antibiotic-adjuvant effects of QS molecules diffusible signal factor (DSF) and B. cenocepacia producing-DSF (BDSF) were investigated against mature Staphylococcal biofilms. Broth microdilution methods were used for the determinations of MIC, MBC, MBIC, and MBEC, and bactericidal activities were determined by TKC method. The lowest MICs were obtained with ciprofloxacin and gentamicin, and MBECs with ciprofloxacin. DSF and BDSF at 0.5 µM decreased the MICs as 2-8, and 2-32 fold, respectively. In TKC studies, -cidal activities were achieved by BDSF + gentamycin, or ciprofloxacin, and DSF + daptomycin, vancomycin, meropenem or gentamycin combinations. Synergistic effects were generally obtained with BDSF + gentamicin combinations, followed by DSF + daptomycin against most S. aureus; while BDSF + gentamicin or ciprofloxacin, and DSF + vancomycin or meropenem were synergist against some S. epidermidis biofilms. Also, the antagonist effects were observed with BDSF + meropenem or ciprofloxacin against each MSSE and MSSA. It is estimated that these QS molecules, although it was strain dependent, generally enhanced the antibiotic activity, and would be a new and effective treatment strategy for biofilm control, either alone or as an antibiotic adjuvant.

Biomechanical study of a biplanar double support screw (BDSF) technique based on Pauwels angle in femoral neck fractures: finite element analysis.

Objective: The objective of the present study is to conduct a comparative analysis of the biomechanical advantages and disadvantages associated with a biplanar double support screw (BDSF) internal fixation device. Methods: Two distinct femoral neck fracture models, one with a 30° angle and the other with a 70° angle, were created using a verified and effective finite element model. Accordingly, a total of eight groups of finite element models were utilized, each implanted with different configurations of fixation devices, including distal screw 150° BDSF, distal screw 165° BDSF, 3 CLS arranged in an inverted triangle configuration, and 4 CLS arranged in a "α" configuration. Subsequently, the displacement and distribution of Von Mises stress (VMS) in the femur and internal fixation device were assessed in each fracture group under an axial load of 2100 N. Results: At Pauwels 30° Angle, the femur with a 150°-BDSF orientation exhibited a maximum displacement of 3.17 mm, while the femur with a 165°-BDSF orientation displayed a maximum displacement of 3.13 mm. When compared with the femoral neck fracture model characterized by a Pauwels Angle of 70°, the shear force observed in the 70° model was significantly higher than that in the 30° model. Conversely, the stability of the 30° model was significantly superior to that of the 70° model. Furthermore, in the 70° model, the BDSF group exhibited a maximum femur displacement that was lower than both the 3CCS (3.46 mm) and 4CCS (3.43 mm) thresholds. Conclusion: The biomechanical properties of the BDSF internal fixation device are superior to the other two hollow screw internal fixation devices. Correspondingly, superior biomechanical outcomes can be achieved through the implementation of distal screw insertion at an angle of 165°. Thus, the BDSF internal fixation technique can be considered as a viable closed reduction internal fixation technique for managing femoral neck fractures at varying Pauwels angles.

Evaluating three internal fixation techniques for Pauwels III femoral neck fractures via finite element analysis.

The selection of implants for fixing unstable femoral neck fractures (FNF) remains contentious. This study employs finite element analysis to examine the biomechanics of treating Pauwels type III femoral neck fractures using cannulated compression screws (3CS), biplane double-supported screw fixation (BDSF), and the femoral neck system (FNS). A three-dimensional model of the proximal femur was developed using computed tomography scans. Fracture models of the femoral neck were created with 3CS, BDSF, and FNS fixations. Von Mises stress on the proximal femur, fracture ends, internal fixators, and model displacements were assessed and compared across the three fixation methods (3CS, BDSF, and FNS) during the heel strike of normal walking. The maximum Von Mises stress in the proximal fragment was significantly higher with 3CS fixation compared to BDSF and FNS fixations (120.45 MPa vs. 82.44 MPa and 84.54 MPa, respectively). Regarding Von Mises stress distribution at the fracture ends, the highest stress in the 3CS group was 57.32 MPa, while BDSF and FNS groups showed 51.39 MPa and 49.23 MPa, respectively. Concerning implant stress, the FNS model exhibited greater Von Mises stress compared to the 3CS and BDSF models (236.67 MPa vs. 134.86 MPa and 140.69 MPa, respectively). Moreover, BDSF displayed slightly lower total displacement than 3CS fixation (7.19 mm vs. 7.66 mm), but slightly higher displacement than FNS (7.19 mm vs. 7.03 mm). This study concludes that BDSF outperforms 3CS fixation in terms of biomechanical efficacy and demonstrates similar performance to the FNS approach. As a result, BDSF stands as a dependable alternative for treating Pauwels type III femoral neck fractures.

BDSF inhibits Candida albicans adherence to urinary catheters.

Cis-2-dodecenoic acid (BDSF) is a quorum-sensing signal molecule produced by the opportunistic pathogen Burkholderia cenocepacia and suppresses germ tube formation of Candida albicans. An in vitro model for biofilm formation evaluated the influence of BDSF on C. albicans. Biofilm morphology was observed using scanning electron microscopy, cell adherence was determined using polystyrene plates and siliconized urinary catheters, and the levels of expression of genes involved in adhesion were determined using Real-time Reverse-Transcriptase Polymerase Chain Reaction. BDSF inhibited initial biofilm formation by a clinical isolate of C. albicans and reduced its capability to adhere to the polystyrene surface. BDSF at concentrations up to 120 µM did not significantly affect the viability of C. albicans. BDSF (90 µM) inhibited cell adherence to plates and catheters by 4- and 25-fold. Compared with untreated yeasts, the level of expression of genes involved in adhesion, ALS1 and EAP1, were reduced by 4- and 0.25-fold, whereas that of YWP1 was increased at a 4-fold higher level. Here we show that BDSF effectively inhibited biofilm development as indicated by its ability to inhibit adherence. Thus, BDSF should be considered as a potential therapeutic agent to prevent disease caused by Candida species.

Role of Biplane Double-Supported Screw Fixation (BDSF) in Management of Fracture Neck Femur and Its Comparison with Conventional CC Screw Fixation.

Background: The aim of this study is to evaluate comparative biomechanical fixation provided with the BDSF method with the conventional CC screw fixation for treatment of femoral neck fractures with three parallel cannulated screws. Methods: This is a prospective cohort study. There were two teams of surgeons out of which one team operated the patients with BDSF technique and second with conventional CC screw fixation technique; thus, the patients were randomly distributed into two groups. Patients were included in the study as per the following inclusion and exclusion criteria. Results: Union was achieved in 15 (83.33%) patients managed by conventional CC screw technique, while union was achieved in 11 (91.67%) patients managed by BDSF technique in the present study. The average Harris hip score in present study was 90 score in patients managed by BDSF technique, while the average Harris hip score in present study was 80 score in patients managed by BDSF technique. Conclusion: Both BDSF and conventional CC screw fixation are good fixation methods for fracture neck of femur. But functional outcome and fracture union rates are better with BDSF Technique. Although, there are some minor problems noted in BDSF technique such as outer cortical fracture at the entry point of beam screw and opening up of anterior cortex of oblique fracture patterns. Thus, BDSF method provides reliable fixation in which early mobilization and partial weight bearing of the patient may be allowed.

Outcomes of BDSF technique for osteosynthesis of femoral neck fractures.

INTRODUCTION: Femoral neck fractures present a significant challenge for orthopedic surgeons, especially in young patients who want to preserve their natural femoral head. Conventional methods for fixing these fractures often lead to poor outcomes and high complication rates. The Biplane Double-supported Screw Fixation (BDSF) technique is a novel approach that involves placing screws in two planes simultaneously, creating a two-point support for the screws in the neck and head of the femur. METHODS: This study aimed to evaluate the effectiveness of the BDSF technique in treating femoral neck fractures in patients aged 20-60 years. A total of 28 patients with fresh femoral neck fractures (less than three weeks old) were treated with closed reduction and internal fixation using the BDSF method. The patients' functional outcomes were evaluated using the Harris hip score, and the radiographic outcomes of union, femoral neck shortening, screw back-out, and femoral head avascular necrosis (AVN) were also evaluated. RESULTS: The results showed that the BDSF technique is a safe and effective method for treating femoral neck fractures in young adults. Out of the 25 patients who were followed up for a mean time of 18 months (range 6-24 months), 20 (80%) achieved fracture union in a mean time of 5.2 months. Non-union occurred in five patients (20%), and AVN of the femoral head was observed in three patients (12%). Two patients experienced varus collapse, but their fractures united successfully. CONCLUSION: The BDSF technique offers several advantages over conventional methods, including increased stability and improved fixation strength. It can be considered as an alternative to conventional methods for managing femoral neck fractures in young adults, with a low incidence of non-union and avascular necrosis and no cases of fixation failure or varus collapse.

Oridonin Attenuates Burkholderia cenocepacia Virulence by Suppressing Quorum-Sensing Signaling.

Burkholderia cenocepacia is a human opportunistic pathogen that mostly employs two types of quorum-sensing (QS) systems to regulate its various biological functions and pathogenicity: the cis-2-dodecenoic acid (BDSF) system and the N-acyl homoserine lactone (AHL) system. In this study, we reported that oridonin, which was screened from a collection of natural products, disrupted important B. cenocepacia phenotypes, including motility, biofilm formation, protease production, and virulence. Genetic and biochemical analyses showed that oridonin inhibited the production of BDSF and AHL signals by decreasing the expression of their synthase-encoding genes. Furthermore, we revealed that oridonin directly binds to the regulator RqpR of the two-component system RqpSR that dominates the above-mentioned QS systems to inhibit the expression of the BDSF and AHL signal synthase-encoding genes. Oridonin also binds to the transcriptional regulator CepR of the cep AHL system to inhibit its binding to the promoter of bclACB. These findings suggest that oridonin could potentially be developed as a new QS inhibitor against pathogenic B. cenocepacia. IMPORTANCE Burkholderia cenocepacia is an important human opportunistic pathogen that can cause life-threatening infections in susceptible individuals. It employs quorum-sensing (QS) systems to regulate biological functions and virulence. In this study, we have identified a lead compound, oridonin, that is capable of interfering with B. cenocepacia QS signaling and physiology. We demonstrate that oridonin suppressed cis-2-dodecenoic acid (BDSF) and N-acyl homoserine lactone (AHL) signal production and attenuated virulence in B. cenocepacia. Oridonin also impaired QS-regulated phenotypes in various Burkholderia species. These results suggest that oridonin could interfere with QS signaling in many Burkholderia species and might be developed as a new antibacterial agent.

Biplane double supported screw fixation for femoral neck fracture in young adults: A prospective cohort study.

Introduction: Achieving accurate anatomic reduction and stable internal fixation is mandatory in the management of femoral neck fractures (FNF) in adults. The spatial configuration and direction of the screws have been reported to provide stability to the fracture. The study's goal is to analyse the clinico-radiological outcome of the newer biplane double-supported screw fixation (BDSF) technique in the Indian cohort. Materials and methods: Patients with isolated FNFs underwent osteo-synthesis by BDSF technique. Radiological outcome was evaluated by time to union and fracture healing on plain radiographs. Clinical outcome was measured using the Harris hip score (HHS) at 1, 3, 6, and 12 months after surgery. The pain reduction was measured using the VAS score. Results: Twenty-seven patients with a mean age of 37.33 ± 9.84 years (24-55 years) were followed up for at least 12 months (12-31 months). The mean HHS at 12 months was 94.81 ± 8.18 (range: 68-100). Twenty-five patients were able to achieve radiological union within a mean time of 14.60 ± 4.69 weeks (range: 8-28). The overall complication rate was found to be 18.51% (5 out of 27 patients). Individual complications were non-union (2 patients; 7.4%), AVN (3 patients; 11.11%), and screw back out with femoral neck shortening (4 patients; 14.81%). Conclusion: Screw configuration using the BDSF technique provides a good union rate with minimum complications. The majority of patients resulted in a good (HHS >80) to excellent functional outcome. Based on the clinico-radiological outcome obtained, we conclude that this technique is effective in the fixation of FNF in adults. Level of study: Level II.

Mutation of the cyclic di-GMP phosphodiesterase gene in Burkholderia lata SK875 attenuates virulence and enhances biofilm formation.

Burkholderia sp. is a gram-negative bacterium that commonly exists in the environment, and can cause diseases in plants, animals, and humans. Here, a transposon mutant library of a Burkholderia lata isolate from a pig with swine respiratory disease in Korea was screened for strains showing attenuated virulence in Caenorhabditis elegans. One such mutant was obtained, and the Tn5 insertion junction was mapped to rpfR, a gene encoding a cyclic di-GMP phosphodiesterase that functions as a receptor. Mutation of rpfR caused a reduction in growth on CPG agar and swimming motility as well as a rough colony morphology on Congo red agar. TLC analysis showed reduced AHL secretion, which was in agreement with the results from plate-based and bioluminescence assays. The mutant strain produced significantly more biofilm detected by crystal violet staining than the parent strain. SEM of the mutant strain clearly showed that the overproduced biofilm contained a filamentous structure. These results suggest that the cyclic di-GMP phosphodiesterase RpfR plays an important role in quorum sensing modulation of the bacterial virulence and biofilm formation.

Efficient click chemistry towards fatty acids containing 1,2,3-triazole: Design and synthesis as potential antifungal drugs for Candida albicans.

Candida is an important opportunistic human fungal pathogen. The cis-2-dodecenoic acid (BDSF) showing in vitro activity of against C. albicans growth, germ-tube germination and biofilm formation has been a potential inhibitor for Candida and other fungi. In this study, facile synthetic strategies toward a novel family of BDSF analogue, 1-alkyl-1H-1,2,3-triazole-4-carboxylic acids (ATCs) was developed. The straightforward synthetic method including converting the commercial available alkyl bromide to alkyl azide, consequently with a typical click chemistry method, copper(II) sulfate and sodium ascorbate as catalyst in water to furnish ATCs with mild to good yields. According to antifungal assay, 1-decyl-4,5-dihydro-1H-1,2,3-triazole-4-carboxylic acid (5d) showed antifungal capability slightly better than BDSF. The 1,2,3-triazole unit played a crucial role for the bioactivity of ATCs was also confirmed when compared with two alkyl-aromatic carboxylic acids. Given its simplicity, high antifungal activity, and wide availability of compounds with halide atoms on the end part of the alkyl chains, the method can be extended to develop more excellent ATC drugs for accomplishing the challenges in future antifungal applications.

Unique stability of femoral neck fractures treated with the novel biplane double-supported screw fixation method: a biomechanical cadaver study.

UNLABELLED: Osteosynthesis of femoral neck fractures is related to 20-46% complication rate. Filipov's novel method for biplane double-supported screw fixation (BDSF), using three cannulated screws, has demonstrated excellent clinical results since 2007. Its two calcar-buttressed screws are oriented in different coronal inclinations with steeper angles to the diaphyseal axis and intended to provide constant fixation strength under different loading situations. The aim of this study was to biomechanically evaluate BDSF fixation strength and compare it with the conventional fixation (CFIX) using three parallel cannulated screws. METHODS: Eight fresh-frozen and six embalmed human femoral pairs with simulated AO/OTA31-B2.2 fracture were fixed applying either CFIX or BDSF. Quasistatic tests were performed in anteroposterior (AP) bending, followed by axial quasistatic, cyclic and destructive quasistatic tests run in 10° flexion with 7° or 16° varus specimen inclination. RESULTS: Initial axial stiffness was significantly higher for BDSF in comparison with CFIX at 7° inclination (p=0.02) and not significantly different between BDSF and CFIX at 16° inclination. Compared with the intact state, it decreased significantly at 7° inclination only for CFIX (p=0.01), but not for BDSF. Interfragmentary displacement during cyclic testing was significantly smaller for BDSF than CFIX at 7° inclination (p≤0.04) and not significantly different between BDSF and CFIX at 16° inclination. Failure load did not differ significantly between BDSF and CFIX at both inclinations. CONCLUSIONS: Femoral neck fracture stability can be substantially increased applying BDSF due to better cortical screw support and screw orientation. Having two calcar-buttressed screws oriented in different inclinations, BDSF can enhance constant stability during various patient activities. The more unstable the situation, the better BDSF stability is in comparison to CFIX.