Gauge Size Research Articles

Impact of Needle Design and Suture Gauge on Tissue Tearing During Skin Suturing: A Comparative Analysis.

Surgeons face numerous choices in selecting sutures for skin closure, with potential adverse effects such as tissue tearing. To investigate the influence of needle design and suture gauge on tissue tearing during suturing procedures. The authors tested the tear-through force in Newtons for 3 needle types and 3 suture gauges using an artificial skin model and a professional-grade tensiometer. Suture material was secured into the skin model, and force was applied to the suture at a constant rate, resulting in tearing. Force-displacement and force-time curves were generated. Evaluation included conventional cutting (PC-3), reverse cutting (PS-3), and taper point (BB) needles with a 5-0 polypropylene suture. In addition, nylon sutures with a reverse cutting needle (PS-2) were tested at 3 suture gauges (5-0, 4-0, 3-0). The mean tear-through forces for PC-3, PS-3, and BB were 3.26 N, 3.75 N, and 4.07 N, respectively. For the 5-0, 4-0, and 3-0 nylon sutures, the mean tear-through forces were 3.44 N, 3.81 N, and 4.04 N, respectively. Statistical analysis revealed a significant impact of suture gauge size (p < .001) and needle geometry (p < .001) on tear-through force. Larger suture diameter and taper needles minimize tissue tearing.

Comparative Analysis of Taper Point and Reverse Cutting Needles on Skin Puncture Force.

Reverse cutting needles are commonly used in cutaneous surgery due to their perceived ease of use. Despite this, there is limited research evaluating the force required to puncture skin using contemporary needles. This study aims to compare the puncture forces required for two different needle geometries across various gauge sizes. The authors assessed the force necessary to penetrate samples of human abdominal skin samples using taper needles of three different United States Pharmacopeia gauge sizes with their respective reverse cutting needle counterparts. Taper point needles tested were RB-1 (3-0), TF (4-0), and C-1 (5-0), while reverse cutting needles included PS-2 (3-0) and P-3 (4-0, 5-0). An electronic force meter was used to record the puncture force required by each needle type. The mean puncture force in newtons (N) for taper point needles was 1.00, 0.74, and 0.48 for RB-1, TF, and C-1, respectively. The mean puncture force for reverse cutting needles was 0.95 N, 0.60 N, and 0.51 N for PS-2, P-3 (4-0), and P-3 (5-0), respectively. There was a direct relationship between needle body diameter and puncture force for both needle geometries. There was no clinically significant difference in skin puncture force between needle geometries.

Tensile Specimen Circular Grid Pattern and AI-Based Strain Calculation Method

During tensile testing of materials, strain measurement is conducted using either contact or non-contact methods. Contact methods offer high accuracy and precision but are limited by the specimen’s thickness and dimensions, whereas non-contact methods minimize damage to thin specimens and allow measurements in various environments, though they require longer preparation and calculation times. This paper proposes a circular grid marking pattern and a strain prediction algorithm using artificial intelligence (AI), which simplifies the preparation process and allows strain prediction without additional equipment. The circular grid pattern can be arranged in various configurations from 1 × 5 to 5 × 7, and a laser marker, which requires minimal time, was used to engrave the pattern on the specimen to shorten the preparation time. The AI model, trained on image-based data, enables strain calculation regardless of the specimen’s gauge length and size, and allows measurement of local strain as well as gauge-length strain. The reliability of this concept was verified by applying it to tensile testing.

Yield and Complications of Endobronchial Ultrasound Using the Expect Endobronchial Ultrasound Needle

Background: Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) stands as the gold standard for sampling the mediastinum and possesses the capability to detect a diverse range of disease processes. The EBUS needle industry has been experiencing rapid advancement, characterized by numerous companies either enhancing existing needles or introducing innovative ones. The majority of EBUS studies to date have predominantly utilized the OlympusTM Vizishot needles, which are constructed from stainless steel. In this paper, we focus on the evaluation of a cobalt chromium needle, namely the ExpectTM EBUS needle, with a specific emphasis on its diagnostic efficacy and any associated complications. It is important to note that our investigation is conducted independently, and we do not provide a comparative analysis with other needle types available in the market. Methods: This is an institutional review board-approved retrospective analysis of all patients who have undergone an EBUS-TBNA lymph node sampling using the ExpectTM needle between August 2016 and September 2017 at the IU Health University Hospital. Comparisons of clinical characteristics by complications, diagnosis, needle gauge, and lymph node size were performed using chi-square test and Fisher’s exact test. Results: 75% of the 102 included patients had their procedures done with the 22-gauge needle which were majorly performed in the setting of suspected intrathoracic malignancy followed by sarcoidosis and lymphoma. 99% of the patients had no complications after their procedures which were almost all diagnostic with two cases of bronchoscope damage. Mutational analysis was successful with both the 22 and 25-Gauge needles. Conclusion: In this paper, we demonstrate that the ExpectTM 22 and 25-gauge needles are safe and effective when used for EBUS-TBNAs through the OlympusTM EBUS bronchoscope for the evaluation of intrathoracic lymphadenopathy.

Venipuncture Site Influences Blood-drop Volume in C57BL/6 Mice.

Many experiments require the collection of serial blood samples from mice. However, the size of mice limits the volume of blood that can be safely collected as a survival procedure. In IACUC protocols, investigators may report the amount of blood they collect from mice as a number of drops. Many institutions, including ours, use an anecdotal conversion factor (1drop of mouse blood = 25μL) to ensure that blood-collection volumes are compliant with institutional guidelines. To our knowledge, previous work has not experimentally determined the volume of a drop of mouse blood. In this 10-wk crossover experiment, 2 phlebotomists bled 30 C57BL/6J mice from 3 sites (facial, saphenous, and tail) using one or 2 different needle gauge sizes per site. Male and female mice were weighed weekly and divided among 5 groups (n = 6): left and right tail vein, left and right saphenous vein, and facial vein. A single blood drop from each site was weighed, and the volume of each drop was calculated using the average blood density determined from 8 mice terminally bled at the end of the study. Venipuncture site and side significantly influenced blood-drop weight and thus calculated volume. Facial vein puncture produced the largest drop volume (mean: 21.7μL), followed by the saphenous vein (mean: 9.97μL) and tail vein (mean: 4.96μL). Collection from the facial vein was associated with more hemorrhage and morbidity. Left-sided venipuncture was associated with slightly larger-volume blood drops, though the effect size of side was small. The results of this study may be useful in more accurately estimating blood loss via conversion of drops to volume. Our data indicate that blood collection from saphenous and tail veins minimizes blood loss relative to facial vein puncture and may optimize both serial collection of small-volume blood samples and animal welfare.

Relevance of Adalimumab Product Attributes to Patient Experience in the Biosimilar Era: A Narrative Review.

Adalimumab (ADL, Humira®, reference product), an anti-TNF-α biologic, has transformed the treatment of chronic, immune-mediated inflammatory diseases. However, the high cost of ADL therapy has driven the development of more affordable ADL biosimilars, agents with no clinically meaningful differences from the reference product. This review summarizes the product attributes of reference ADL and the nine ADL biosimilars approved and available in the USA in relation to patient experience of injection-site pain (ISP). Product formulation, delivery volume and device features (e.g., type and needle gauge size) influence patient experience of ISP with potential clinical consequences. Citrate-free formulations generally cause less ISP; injection volumes of > 1.5ml may be associated with increased ISP. Reference ADL and all ADL biosimilars offer a citrate-free formulation, and reference ADL and four ADL biosimilars offer a high-concentration solution that allows a smaller injection volume. All available ADL products are injected subcutaneously using either a pre-filled pen (PFP) or pre-filled syringe (PFS). Patients prefer the PFP, but the PFS permits better control over the speed and duration of injection. Smaller (29-gauge) needle outer diameter is associated with less ISP; reference ADL and seven ADL biosimilars offer a device with a 29-gauge needle. In the USA, an approved biosimilar can be designated "interchangeable," allowing pharmacy-level substitution, where state law permits. In the USA, two ADL biosimilars have received interchangeability designation; others are seeking interchangeability designation from the Food and Drug Administration (n = 2), are being evaluated in clinical studies to support interchangeability (n = 2), or do not have/are not seeking interchangeability designation (n = 3). Product-related attributes influence patient experience of ISP caused by subcutaneous ADL injection. Reference ADL and ADL biosimilar products differ in their attributes, so discussion with patients about treatment options is essential to optimize adherence and outcomes.

Optimum pinhole size determination in pinhole pupilloplasty for higher-order aberrations.

To determine optimal pinhole size (OPS) and establish a relationship with visual acuity (VA) and RMS (root mean square) values in cases with higher-order aberrations (HOAs) undergoing pinhole pupilloplasty (PPP). Private practice, India. Prospective, interventional study. RMS value for 6-mm-diameter optical zone was determined by Scheimpflug imaging (Pentacam). Patients with RMS value >0.3 μm were included. Preoperatively, a hand-held pinhole gauge with varied apertures determined the OPS, and single-pass four-throw technique was used to perform pupilloplasty with Purkinje-1 reflex as a marker for centration. VA with OPS, correlation of RMS values with OPS and pupil size, and Strehl ratio were the main outcome measures. 29 eyes with HOAs were analyzed; all patients chose 1.0 or 1.5 mm as OPS. The mean preoperative and postoperative pupil size was 3.25 ± 0.81 mm and 1.8 ± 0.54 mm ( P = .000), respectively. Postoperative mean pupil size when compared with OPS denoted that 14 eyes had a difference of <0.1 mm, 8 eyes ranged from 0.2 to 0.45 mm, and 7 eyes had ≥0.6 mm (range from 0.6 to 1.8 mm) difference from OPS. Eyes with higher RMS values needed smaller pupil gauge to achieve better VA. Preoperatively, vision with OPS correlated well with preoperative 6-mm RMS HOAs ( r = 0.728; P = .00). Postoperative UDVA correlated well with VA measured with OPS ( r = 0.847; P = .00). The preoperative and postoperative mean Strehl ratio was 0.109 ± 0.07 and 0.195 ± 0.11 ( P = .001), respectively. Higher RMS values required a smaller pupil to achieve optimum VA. PPP can help achieve pinhole size in accordance with patient's optimum pinhole requirement.

Clinical Perspectives on the Injectability of Cross-Linked Hyaluronic Acid Dermal Fillers: A Standardized Methodology for Commercial Product Benchmarking with Inter-Injector Assessments.

The injectability of cross-linked hyaluronic acid (HA) dermal fillers is influenced by polymer concentration, polymer cross-linking type and degree, the presence of lidocaine or other functional excipients, types of syringes, and injection techniques. Finished product injectability constitutes a critical quality attribute for clinical injectors, as it strongly influences product applicability and ease of use in aesthetic medicine. While injectable product extrusion force specifications are provided by the respective device manufacturers, the qualitative informative value of such datasets is low for injectors wishing to compare product brands and technologies from an injectability standpoint. Therefore, the present study comparatively assessed 28 cross-linked HA dermal fillers (JUVÉDERM®, Restylane®, BELOTERO®, TEOSYAL RHA®, and STYLAGE® brands) using various injectability benchmarking setups for enhanced clinical-oriented relevance. Manual product injections were performed by three specialized and experienced clinicians, whereas automatic product extrusion was performed using a Texture Analyzer instrument. The various hydrogel products were injected into ex vivo human skin and into SimSkin® cutaneous equivalents to appropriately account for injection-related counterpressure. The injectability results revealed important variability between and within product brands, with a strong influence of the local anesthetic lidocaine, HA contents, and needle gauge size. Critical appraisals of the investigated products were performed, notably from manufacturing process-based and clinical ease of application-based standpoints, centered on respective experimental injectability quality levels. Generally, it was confirmed that each HA-based dermal filler product requires specific expertise for optimal injection, mainly due to differing viscoelastic characteristics and injectability attributes. Overall, the present study set forth evidence-based and clinical-oriented rationale elements confirming the importance for injectors to work with injectable products with which they are experienced and comfortable to optimize clinical results.

Effect of Needle Gauge Size on Pain During Intravitreal Anti-VEGF Injection: A Systematic Review and Network Meta-Analysis.

Concerns related to pain from intravitreal injections are one of the key factors mentioned by patients when asked about therapy. In this systematic review and network meta-analysis, we evaluate the literature of comparative clinical trials on the relationship between needle gauge size and pain experience during intravitreal anti-vascular endothelial growth factor (anti-VEGF) therapy. We searched 12 literature databases on 14 October 2023 for comparative studies of gauge sizes for intravitreal anti-VEGF injections. The primary outcome of interest was the reported pain experience immediately after the injection. All outcomes of pain were transformed into standardized effect sizes using Cohen's d. Using a network meta-analysis approach, we were able to compare all gauge sizes and rank them according to the reported pain experience. We identified nine eligible studies with data on a total of 998 patients and 1004 eyes. Needle sizes studied were 26-gauge, 27-gauge, 29-gauge, 30-gauge, 32-gauge, 33-gauge, and 34-gauge. A complete network was present, which allowed for a network meta-analysis. We used the thickest (26-gauge) needle as the reference group and observed a clear trend of lower pain experience with thinner gauge sizes (d: -0.4, d: -2.7, d: -3.8, d: -4.8, d: -4.5, and d: -5.3; respectively, for 27-gauge, 29-gauge, 30-gauge, 32-gauge, 33-gauge, and 34-gauge). A gauge size of 30 or thinner may minimize patient discomfort related to intravitreal anti-VEGF therapy.

Strain Measurement with Optic Fibers for Structural Health Monitoring of Woven Composites: Comparison with Strain Gauges and Digital Image Correlation Measurements.

In this work, the strains measured with optic fibers and recorded during tensile tests performed on carbon/epoxy composite specimens were compared to those recorded by strain gauges and by Digital Image Correlation (DIC). The work aims at investigating the sensitivity of embedded and glued optic sensors for structural health monitoring applications in comparison with strain gauges and the full field strain map of the DIC. Acrylate, polyimide optic fibers, and three strain gauge sizes are considered to compare the three techniques. Results show hard polyimide-coated sensors are more sensitive to the material pattern than soft acrylate-coated fibers, which also require extensive adhesion length. The work shows a comparable size of strain gauges and material meso-structure is also critical for properly assessing material properties. The Young's modulus computed with the three different techniques is used to define a strategy that supports the selection and the proper size of the adopted strain measuring system for structural health monitoring of composite materials.

Development of 0.5 mm gauge size radial collimators for high-pressure neutron diffraction experiments at PLANET in J-PARC

Radial collimators with a 0.5 mm gauge size (GS) were specially designed for high-pressure neutron diffraction experiments. The performance and efficacy of these collimators, along with the 1.5 mm and 3.0 mm GS radial collimators, were investigated. The radial collimators with nominal GS of 0.75 mm, 1.5 mm, and 3.0 mm effectively exhibited GS of 0.50 mm, 1.07 mm, and 2.78 mm, respectively. The transmissions of all three radial collimators were deemed equivalent. The assessment using a Paris–Edinburgh (PE) press equipped with double-toroidal anvils and a diamond anvil cell (DAC) tailored for neutron diffraction revealed that the scattering intensity from the anvils was considerably minimized using the radial collimators and the sample-to-anvil signal ratio, as defined by the Bragg peak intensity ratio (IMgO220/IDiamond220), reached values of 0.5 and 2.0 for the PE press and DAC, respectively, when using the 0.5 mm GS radial collimators. These results indicate that the 0.5 mm GS radial collimators have been fabricated as intended and exhibit efficacy for the high-pressure-neutron diffraction experiments, specifically those exceeding 30 GPa, which cannot be reached with a PE press equipped with the standard double-toroidal anvils of a 1.5 mm cup diameter. Among those ever manufactured for neutron scattering experiments, the radial collimators display the smallest GS.

Enhanced Needle Visualization with Reflection Tuned Apodization based on the Radon Transform for Ultrasound Imaging.

In ultrasound (US) guided interventions, accurately tracking and visualizing needles during in-plane insertions is a significant challenge due to strong directional specular reflections. These reflections violate the geometrical delay and apodization estimations in the conventional delay and sum beamforming (DASB) degrading the visualization of needles. This study proposes a novel reflection tuned apodization to address this issue and facilitate needle enhancement through DASB. The method leverages both temporal and angular information derived from the Radon transforms of the RF data from plane-wave imaging to filter the specular reflections from the needle and their directivity. The directivity information is translated into apodization center maps through time-to-space mapping in the Radon domain which is subsequently integrated into DASB. We assess the influence of needle angulations, projection angles in the Radon transform, needle gauge sizes, and the presence of multiple specular interfaces on the approach. The analysis shows that the method surpasses conventional DASB in enhancing the image quality of needle interfaces while preserving the diffuse scattering from the surrounding tissues without significant computational overhead. The work offers promising prospects for improved outcomes in US guided interventions and better insights into characterizing US reflections with Radon transforms.

Diagnostic quality of ultrasound-guided fine-needle aspirates samples from the canine liver and spleen is not significantly affected by using 22-, 23-, and 25-gauge needles.

Ultrasound-guided fine-needle aspirates (FNA) of the liver and spleen for cytological analysis are a commonly performed procedure in canine veterinary practice. Based on our review of the literature, this is the first published study investigating whether needle size affects the diagnostic quality of hepatic and splenic samples. The aim of this prospective analytical study was to compare the diagnostic quality of ultrasound-guided FNA cytological samples of canine liver and spleen based on cellularity, blood contamination, and overall cell preservation between three different needle sizes (22-, 23-, and 25-gauge). A total of 282 splenic aspirates from 94 dogs and 348 hepatic aspirates from 116 dogs were enrolled in the study and examined by two board-certified veterinary clinical pathologists. In this study, no significant differences in diagnostic quality were identified between different needle gauge sizes when sampling canine liver and spleen. Blood contamination was higher using 22-gauge needles compared with 25-gauge needles (P=0.024) when sampling the liver.

Radial collimator performance and future collimator updates for the high-intensity total scattering diffractometer NOVA at J-PARC

The high-intensity neutron total scattering diffractometer NOVA at the Materials and Life Science Experimental Facility in the Japan Proton Accelerator Research Complex has a variety of sample environments. For background reduction, we manufactured and installed the radial collimator NOVARC with a gauge size of ∼32 mm. We evaluated its performance and succeeded in eliminating the unwanted scattering from the sample environment equipment and reducing the background signal to less than 4%. We also confirmed that G(r) data, which is important for pair distribution function analysis, is consistent with the one obtained at the sample environment with almost no background. In the future, we plan to combine NOVARC with a radial collimator manufactured using a 3D printer for measuring even smaller specimens or for extreme environments.

A resin gauge for performance testing of X-ray CT and its calibration by multiple orientation measurements

An accurate and traceable performance testing of the X-ray computed tomography (XCT) is crucial for the application of the XCT in various industrial fields. For the performance testing of the XCT, we proposed a novel gauge with spheres embedded in a cylindrical resin. The proposed gauge is free from the artifacts caused by the gauge structure, and the spheres can be arranged at any position of the gauge. Additionally, the gauge can be placed with different orientations and it can be produced at an economical price. We verified the feasibility of using the proposed gauge as a reference standard, in terms of the coefficient of thermal expansion and secular change of the resin. Furthermore, we developed the associated calibration method for the gauge through multiple orientation measurements using the XCT. From the results, the proposed gauge can be calibrated with an uncertainty of 1.9 μm when the gauge size is 30 mm.

A numerical assessment of local strain measurements on the attenuation and modulus dispersion in rocks with fluid heterogeneities

SUMMARY The forced oscillation method is widely used to investigate intrinsic seismic wave dispersion and attenuation in rock samples by measuring their dynamic stress–strain response. However, using strain gauges to locally measure the strains on samples surfaces can result in errors in determining the attenuation and moduli of rocks with mesoscopic scale heterogeneities. In this study, we developed a 3-D numerical model based on Biot's poroelastic theory to investigate the effect of strain gauge location, number and size on attenuation and dispersion in response to wave-induced fluid flow. Our results show that increasing the strain gauge length, number, and size can reduce the error between local and bulk responses. In a homogeneous and isotropic rock with a quasi-fractal fluid heterogeneity at 12 per cent gas saturation, the relative error between local and bulk responses stays below 6 per cent when the strain gauge length surpasses 8.6 times the correlation length. As the gas saturation becomes larger, the ratio minimally changes non-monotonically, initially increasing and then decreasing. We also used the Monte Carlo method to demonstrate that local laboratory measurements can approximate the reservoir-scale response with a minimum relative error of 1.5 per cent as the sample number increases. Our findings provide guidance for (i) interpreting local low-frequency measurements in terms of bulk properties of rock and (ii) upscaling lab measurements to reservoir-scale properties.

Pullout Behavior of Connections Using Self-Drilling Screws for Pultruded Fiber-Reinforced Polymer Composites in Construction

Self-drilling screws provide an efficient and cost-effective way of joining lightweight structural members. In this work, the performance of self-drilling screw connections for fiber-reinforced polymer (FRP) structural members is investigated, for use in joining panels or plates to square hollow sections (SHSs). To investigate the resistance to pullout loads, tensile tests were conducted on connection specimens consisting of an FRP plate joined to an FRP SHS at a right angle. The specimens were prepared in five configurations, with differences in pultrusion directions of the FRP plate, screw gauge size, and coarseness of the screw threads. The specimens having fibers oriented transversely in the FRP plate exhibited a flexural failure of the plate and the lowest connection strength. The specimens having fibers oriented longitudinally in the FRP plate failed by the screw being pulled out from the FRP SHS profiles; shearing out of the thread in the screw hole. An increase in screw gauge size and thread coarseness was found to be beneficial to the connection strength. Further analysis was carried out to estimate the initial stiffness and the connection strength, by finite-element and analytical modeling, respectively. In addition, these analyses are able to correlate the average shear stress at failure of the connection specimens to the screw gauge size, thread coarseness, and effective contact area of the screws.

983: PERIPHERAL VASOPRESSOR INFUSION FOR SHOCK: A QUALITY ASSESSMENT PROJECT IN A COMMUNITY ICU

Introduction: Vasopressor medications in shock are generally administered via central line but placement requires technical proficiency and in community ICU/ED settings, provider availability is not guaranteed around the clock. Evaluating the feasibility of peripheral vasopressor use in a real-world community hospital-based ICU allows us to explore alternative options. The primary objective was to assess the incidence of infiltration, skin necrosis, or limb loss resulting from peripheral vasopressor administration. A secondary objective was to assess the size and location of peripheral intravenous lines and the need for secondary central IV accesses. Institutional IRB approval was obtained. Methods: EMR records for all patients admitted with shock (any type) to a 12-bed community medical ICU receiving vasopressor support during 2018 were individually chart reviewed by a staff intensivist. The local sentinel event reporting system, and physician and nursing documentation were reviewed for any incidence of IV extravasation, or limb damage/loss. Pharmacy records of phentolamine/nitroglycerin paste orders ensured all cases of extravasation were captured. Results: There were 136 unique admissions requiring vasopressor support in 2018. 37.5 % of patients had central lines placed already while 44.9% of patients had vasopressors infused via peripheral IV. Of the 61 patients with peripheral IVs, 30 (49.2%) required placement of a central line. Vasopressors used included phenylephrine (47.1%), norepinephrine (41.9%), vasopressin (7.4%), dobutamine (2.9%) and epinephrine (0.7%). The average duration of vasopressor infusion through peripheral access was 592 mins. There were 8 episodes of infiltration amongst the peripheral IV group, with no episodes of skin damage or necrosis. The median IV size was 20 gauge, and the incidence of infiltration showed no significant association with gauge size (95%CI: -1.4, 0.61; P = 0.43). Conclusions: This dataset suggests that cutaneous infiltration of vasoactive medications is infrequent. Within this patient sample topical nitroglycerine or IV phentolamine, an antidote for cutaneous, drug-induced vasoconstriction, was rarely required. Gauge size in peripheral vasopressor administration appeared to make no difference.

Understanding syringeability and injectability of high molecular weight PEO solution through time-dependent force-distance profiles

Opioid medications play a vital role in treating moderate to severe pain. Unfortunately, many drug misusers and abusers attempt to alter the formulations or properties of these drugs by manipulation, (e.g., crushing, chewing, smoking, snorting, injecting). The intravenous (IV) route is most dangerous to abusers, as the drugs directly enter the circulatory system and produce intense euphoria. To obtain a full understanding of the impact of syringe factors (e.g., needle gauge size, needle length, syringe barrel size), on the ease of injection, we undertook a comprehensive assessment of syringeability and injectability of manipulated abuse-deterrent formulations (ADFs). A texture analyzer-based testing method was developed for the measurement of the resistance force of pulling, holding, and pushing phases of injections. Results showed that the finer needle gauge sizes required higher injection force to withdraw drug solutions. In addition, the syringed liquid volume was highly dependent on needle gauge size, holding time, and sample viscosity. In most cases, a lower needle gauge number and a longer holding time increased the syringed volume. Needle length was highly correlated to injection force (R2 = 0.99). Using longer needles to inject drug solution requires greater force. Furthermore, large barrel size was correlated to pushing force (R2 = 0.99); thus, increasing the difficulty of pushing the plunger of a large syringe with one hand. Finally, relationships between injection force, sample viscosity, and testing conditions were elucidated using a mathematical model, which could be used in the future to assess and predict injection force of solution samples.

Rat tail models for the assessment of injectable nucleus pulposus regeneration strategies.

Back pain is a global epidemiological and socioeconomic problem often associated with intervertebral disc degeneration; a condition believed to initiate in the nucleus pulposus (NP). There is considerable interest in developing early therapeutic interventions to target the NP and halt degeneration. Rat caudal models of disc degeneration have demonstrated significant utility in the study of disease progression and its impact on tissue structure, composition, and mechanical performance. One significant advantage of the caudal model is the ease of access and high throughput nature. However, considerable variability exists across the literature in terms of experimental setup and parameters. The objective of this article is to aid researchers in the design and development of caudal puncture models by providing details and insight into the most reported experimental parameters. Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) guidelines were employed to screen the existing literature and 80 manuscripts met the inclusion criteria. Disc geometry, surgical approaches, effect of needle gauge size to induce degeneration, therapeutic volume, outcome measures, and associated limitations are considered and discussed, and a range of recommendations based on different research questions are presented.