Adjustable Length Research Articles

Novel electrosurgical knife with adjustable sheath length for colorectal endoscopic submucosal dissection.

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Injection-seeded Q-switched laser based on a double corner cube retroreflector ring cavity

An injection-seeded Q-switched Er:YAG laser with a double-corner-cube-retroreflector (DCCR) ring cavity has been demonstrated for the first time. The output coupling tuning range of the DCCR ring cavity was calculated to be 2.4% ∼ 97.5%. By tuning the output coupling, the injection-seeded Q-switched Er:YAG laser outputs a 1645 nm single-frequency laser pulse with optimum efficiency at pump powers of 23.2, 24.2, 25.2, and 26.2 W. The corresponding measured output coupling ratios are 1.6, 2.4, 2.4, and 2.4%, respectively. The pulse repetition rate is 143 Hz, and the pulse width varies from 100 ns to 200 ns as the pump power changes. In designing this laser, a new cavity length adjustment configuration of a double optical wedge was employed, achieving a maximum adjustment length of ΔL = 3.62 μm; the procedures for injecting the seed laser and detecting the resonance signal were analyzed, proving the feasibility of applying a DCCR ring cavity to an injection-seeded Q-switched laser.

Comparación de la corrección del offset femoral tras el empleo de un vástago monobloque y un vástago con cuello modular en la artroplastia total de cadera primaria

Introduction and objectiveDual modularity stems were introduced with the theoretical advantage of restoring hip anatomy more precisely through femoral offset and limb length adjustment. Interchangeable necks allow for intraoperative angulation, anteversion and length changes. Our objective is to study whether a better femoral offset correction is achieved with the H MAX-M® prosthesis (Limacorporate, San Daniele, Italy) compared to its monoblock counterpart. Material and methodsA prospective cohort study was conducted by means of consecutive sampling on adult patients undergoing total hip arthroplasty with the diagnosis of coxarthrosis between January 2011 and December 2015. This cohort has two arms, one arm included patients who underwent modular neck arthroplasty and the other included patients who underwent monoblock total hip arthroplasty. Radiographic offset measurement of the operated hip and the contralateral hip was performed, and the difference between both values was calculated. The mean of the measurements obtained for each arm of the cohort were compared with each other. ResultsNo statistically significant differences were observed in the difference in offset between the operated hip and the contralateral hip (P=.323). No statistically significant differences were observed in the correction of the femoral offset, determined as the difference between the operated hip and the contralateral hip (P=.323). Nor were differences observed in the postoperative offset values (P=.097). It should be noted that for both designs, the majority group is the one with restored offset (P=.001).

P075 IS INTER-RECTI DISTANCE (IRD) A RELIABLE PROXY FOR EVALUATION OF FUNCTIONAL IMPAIRMENTS ASSOCIATED WITH DIASTASIS RECTI ABDOMINIS (DRA)?

Abstract Aim Diastasis recti abdominis (DRA) following pregnancy is associated with functional impairment such as back pain, abdominal core instability, urinary incontinence, and abdominal bulging. Several studies have reported functional improvements after surgical repair of the DRA. The aim of this study was to investigate the association between the inter-recti distance (IRD) and self-reported functional disabilities measured with the Disability Rating Index questionnaire (DRI), with the hypothesis that inter-recti distance could serve as a proxy for core instability symptoms. Material and Methods A retrospective study based on a consecutive cohort of patients with core instability symptoms combined with DRA. The IRD was measured with ultrasonography among women with symptomatic post-partum DRA and functional impairments were registered with the self-report DRI questionnaire that covers twelve unspecific daily activities. IRD results were analysed against the DRI score with uni- and multivariable regression analyses. Results A total of 222 women were included in this study. Univariable regression analyses showed a significant positive correlation between the heavier activities running, heavy work, lifting heavy objects and exercise/sports and IRD, which failed to reach significance in the multivariable regression analysis with adjustments for length, weight, and BMI. Conclusions This study could not show any significant correlation between self-reported functional impairments and DRA isolated in the multivariable analysis, even though there is a tendency towards an association between DRA and heavy activities. The post-partum core instability situation is complex and probably origins from more components than solely the inter-recti distance.

Effect of childhood obesity on admissions for respiratory disease.

The purpose of this study was to assess for an association between higher body mass index and disease severity, morbidity and mortality in children admitted for an acute respiratory distress and failure. A single-institution retrospective cross-sectional study performed in the United States evaluating paediatric patients, 2-20years of age, admitted for diagnoses related to acute respiratory distress and acute respiratory failure. Main outcomes include disease severity as assessed using the respiratory component of the Paediatric Early Warning Score (PEWS) with adjustment for altered mental status (Resp-PEWS+AMS), hospital or intensive care length of stay (LOS) and death. Children with obesity made up 42/334 (13%) of the cohort. There was no significant difference in Resp-PEWS+AMS between obese and non-obese cohorts (mean of 0.93, {standard deviation 1.11} vs. 1.13 {1.35}, range 0-6, rank sum p=0.46). There was no significant difference in overall hospital LOS or intensive care LOS. Multivariate analysis including diagnosis as a control variable did not change the results. We found that body habitus was not an independent factor for illness severity or clinical outcomes.

Customizable Sophisticated Three-Dimensional Shape Changes of Large-Size Liquid Crystal Elastomer Actuators.

Stimuli-responsive liquid crystal elastomers (LCEs), which exhibit sophisticated and versatile shape variations and functions upon stimulations, have constantly interested material science researchers. To date, many challenges still exist in scaling up orientated LCEs with sophisticated physical shapes and multi-functions. Herein, LCEs with various customizable conventional and exotic three-dimensional (3D) shapes and with sizes larger than those previously reported have been prepared by combining magnetic field alignment and soft lithography technology. These LCEs have film, cylinder, ellipsoid, hemispheroid, tube, pyramid, triangle and rectangle frame, grid pattern, cubic frame, and spring shapes. Meanwhile, diversified deformation behaviors such as contraction, expansion, bending, and twisting have been achieved by effectively controlling the alignment directions. Finally, the LCE actuator with hemispheroid shape has been explored for its possible applications in dynamic Braille displays or lenses with adjustable focal length. The simple strategy reported here provides a convenient way to customize multimorphological large-size 3D LCE actuators and their stimuli-responsive deformations. These systems will considerably enlarge the potential applications of LCEs and benefit the development of LCE soft robots and the future special bionic systems.

Time Spent at Home Among Older Adults with AML Treated with Hypomethylating Agents and Venetoclax

IntroductionThe prognosis for older adults with acute myeloid leukemia (AML) is poor. Of approximately 12,000 adults age ≥ 60 diagnosed with AML in the U.S. annually, less than 40% survive 1 year from diagnosis. Prior research has shown that adults with AML feel time at home is a critical consideration in treatment selection. However, to date, no study has adequately described the amount of time older adults can expect to spend at home following initiation of AML therapy. In this study, we aimed to (1) quantify this time and (2) assess the impact of venetoclax (VEN) combination therapy on time at home for older adults with AML.MethodsWe queried records from University of North Carolina Health to identify individuals age ≥ 60 newly diagnosed with AML from 2015 to 2020. First-line AML therapy was identified, and those receiving azacitidine (AZA) and/or VEN were included. Dates of diagnosis, first remission, death, last follow up, and all oncology clinic / emergency department (ED) / inpatient encounters were captured. Patients with incomplete records were excluded.The primary outcome was proportion of days at home (PDH). PDH was calculated for each patient by subtracting the number of care days (days hospitalized or seen in an ED / oncology clinic / infusion center) from the total days of follow up, divided by total days of follow up. Overall survival (OS) was calculated via the Kaplan-Meier method. Covariates including demographics and disease risk (per European Leukemia Net 2017) were captured.PDH was evaluated via summary statistics for the full cohort and stratified by each categorical variable, both for the full follow up period and on a month-by-month basis among survivors. Associations between PDH and covariates were further assessed via linear regression with adjustment for length of follow up, with significance assessed via Wald Chi-square test.ResultsFrom 2015-2020, 137 older adults receiving first-line AZA and/or VEN were identified. 24 were excluded due to incomplete records. Among the remaining 113, mean age was 76 (range 60-99), 80.4% were white, and 43.4% were female. Most received AZA+VEN (51.3%) followed by AZA monotherapy (39.0%) and other VEN-containing combinations (9.7%). The majority had adverse-risk AML (61.3%). Baseline covariates including age and ELN risk were similar across therapy groups.Over the full follow up period, mean PDH was 0.58 (95% confidence interval 0.54-0.63) with a median of 0.63. PDH was similar among those with adverse-risk (mean 0.55, CI 0.49-0.61) and intermediate-risk AML (0.64, CI 0.56-0.72). PDH did not differ among therapy groups: AZA+VEN (0.60, CI 0.54-0.66), AZA alone (0.57, CI 0.49-0.66), and other VEN-containing regimens (0.54, CI 0.40-0.69). When adjusted for length of follow up, no covariate had a significant association with PDH (all p > 0.05).When evaluated month-by-month, the proportion of days at home rose over time among survivors. For example, of patients who survived the full month, mean PDH was 0.51 (CI 0.47-54, n = 105) in month 1 following diagnosis and 0.77 (CI 0.72-0.82, n = 57) in month 6. Figure 1 summarizes person-days at home or engaged in care for 12 months following diagnosis (including contributions from those who did not survive the full month).34.5% of patients achieved composite complete remission, with higher rates among those receiving AZA+VEN (51.7%) than AZA alone (13.6%) (OR 6.8, p = 0.0002). Median OS was 0.64 years (CI 0.32 - 0.91) and was similar across therapy groups.ConclusionBurden of care for older adults with AML treated with first-line AZA or VEN is high. These individuals spend nearly half (cohort mean 42%) of days following diagnosis engaged in oncology care. In randomized studies, the addition of VEN to AZA improves OS and increases remission rates though results in higher rates of neutropenic fever. Although this study may be underpowered to detect small differences, the superior remission rates with AZA+VEN did not translate to more days at home, perhaps due to increased admissions for neutropenic fever and office/infusion visits.Given the importance of time at home to older adults with AML identified in prior research, these data provide new information to support shared decision making regarding treatment options. Future prospective trials should evaluate burden of care, including time at home, as an endpoint. While awaiting these data, larger analyses of the impact of treatment regimen on burden of care would be useful. [Display omitted] DisclosuresBryant: Carevive: Consultancy, Research Funding; Jazz Pharmaceuticals: Consultancy, Research Funding; Servier Pharmaceuticals: Honoraria, Speakers Bureau. Coombs: Alexion Pharmaceuticals: Research Funding; Machaon Diagnostics: Research Funding. Foster: Macrogenics: Research Funding; Rafael Pharmaceuticals: Research Funding; Macrogenics: Consultancy; Daiichi Sankyo: Consultancy; Agios: Consultancy; Bellicum Pharmaceuticals: Research Funding.

Outcomes of staged reconstruction of Zone 2 flexor tendon injuries in recent wide-awake surgical settings and an earlier case series

We report outcomes of patients who were managed with two-stage tendon grafting for neglected Zone 2 flexor tendon injuries from 2012 until 2019. The patients were divided into two cohorts: recent series (Series 1) included patients treated with local anaesthesia and epinephrine (16 fingers, from 2015), and earlier series (Series 2) included patients treated with either general or local intravenous anaesthesia and tourniquet (12 fingers, before 2015). The patients in Series 1 achieved statistically better mean total active motion of the operated fingers and grip compared with the contralateral hand than the earlier series (p = 0.03, p = 0.01, respectively). With the Tang grading system, excellent and good results were achieved in 13 and six fingers of the patients in Series 1 and Series 2, respectively. We conclude that wide-awake second stage of staged flexor tendon grafting provides fine-tuned adjustment of length and tension of the graft, but we cannot conclude about comparative outcomes between two series because the sample size is small and the earlier series was operated by the same surgeons with lower expertise level.Level of evidence: IV.

Low-Cost Endoscope Camera System for Neurosurgical Cadaveric Laboratory Dissections

Many training institutions in low-income countries do not have the resources to purchase and maintain a clinical-grade endoscopy tower dedicated to the laboratory. This project aimed to create a low-cost endoscope camera system using online-sourced materials to allow the operators to practice endoscopic surgical techniques in a cadaver laboratory setting. A low-cost endoscope system was created using a 34MP camera with recording capabilities and direct streaming to high-definition multimedia interface in full high resolution, with an adjustable focal length coupler and a light-emitting diode light source. The system cost was $443, as the endoscope and the monitor were already in the laboratory. The system was successfully employed to practice endoscopic dissections in 3 cadaveric specimens with good visualization of relevant structures. This article demonstrated how to produce a low-cost endoscope camera system for laboratory training in neuroendoscopy.

Adjusting the length of supramolecular polymer bottlebrushes by top-down approaches.

Controlling the length of one-dimensional (1D) polymer nanostructures remains a key challenge on the way toward the applications of these structures. Here, we demonstrate that top-down processing facilitates a straightforward adjustment of the length of polyethylene oxide (PEO)-based supramolecular polymer bottlebrushes (SPBs) in aqueous solutions. These cylindrical structures self-assemble via directional hydrogen bonds formed by benzenetrisurea (BTU) or benzenetrispeptide (BTP) motifs located within the hydrophobic core of the fiber. A slow transition from different organic solvents to water leads first to the formation of µm-long fibers, which can subsequently be fragmented by ultrasonication or dual asymmetric centrifugation. The latter allows for a better adjustment of applied shear stresses, and thus enables access to differently sized fragments depending on time and rotation rate. Extended sonication and scission analysis further allowed an estimation of tensile strengths of around 16 MPa for both the BTU and BTP systems. In combination with the high kinetic stability of these SPBs, the applied top-down methods represent an easily implementable technique toward 1D polymer nanostructures with an adjustable length in the range of interest for perspective biomedical applications.

Accuracy of Intraocular Lens Calculation Formulas in Patients Undergoing Combined Phakic Intraocular Lens Removal and Cataract Surgery

To investigate the prediction accuracy of intraocular lens (IOL) calculation formulas, and the impact of anterior chamber depth (ACD) and lens thickness (LT) measurement errors on IOL power calculation in patients undergoing combined phakic IOL (PIOL) removal and cataract surgery. Retrospective, consecutive case series study. Thirty-six PIOL implanted eyes (12 anterior chamber PIOLs and 24 posterior chamber PIOLs [PC-PIOL]) undergoing cataract surgery were included. The prediction accuracy of new formulas (Barrett universal II, Emmetropia verifying optical, Kane, and Ladas super formula) and traditional formulas (Haigis, Hoffer Q, Holladay 1 and SRK/T) with or without Wang-Koch (WK) axial length (AL) adjustment was evaluated. The influence of ACD and LT measurement errors of IOLMaster 700 on refractive outcomes was also investigated. The Kane and traditional formulas with WK AL adjustment had no significant systematic prediction error and displayed a smaller median absolute error, whereas the other formulas showed significant hyperopia shift (P < .05) and relatively lower prediction accuracy. The accuracy rate of IOLMaster 700 in measuring the ACD and LT was 100% in eyes with anterior chamber PIOL implantation, and 37.50% in the PC-PIOL subgroup. No significant difference was observed in refractive outcomes of formulas using correct and wrong parameters in the PC-PIOL subgroup (P > .05). The Kane and traditional formulas with WK AL adjustment exhibited relatively higher prediction accuracy in patients who underwent combined PIOL removal and cataract surgery. The IOLMaster 700 displayed low accuracy in ACD and LT measurements for PC-PIOL implanted eyes, but showed negligible impact on IOL prediction accuracy.

A Flexible and Stretchable 12‐Lead Electrocardiogram System with Individually Deformable Interconnects

AbstractDynamic multilead monitoring of cardiovascular health conditions is challenging due to the complexity of constructing a flexible system that covers large surface areas and synchronizes measurement results from different leads. A flexible 12‐lead electrocardiography system that can simultaneously conduct electrocardiogram sensing and 3‐axis acceleration monitoring is developed. The system is fabricated through a modularized printing process, resulting in individual modules that can be assembled reversibly through magnetic connectors. Different levels of stretchability and adjustable length of interconnect can accommodate different body statures and deformations. A wireless flexible circuit with high adaptability can deform through individually deformable interconnectors. The system is used to monitor seven people for more than 2 h, offering comparable accuracy as the commercial system. The accuracy values of R‐peak detection at 12 leads during jogging are higher than 85%, showing improved stability and excellent tolerance to motion. The system is later employed for 24 h monitoring to judge the activities and heart health conditions. All experimental results indicate that the system can be readily applied to accommodate large‐scale manufacturing and large population health monitoring.

Ageing does not affect the dynamic balance margins of gait

If an obstacle suddenly appears during walking, either the crossing step can be lengthened or the precrossing step shortened to avoid the obstacle. We investigated the effects of temporal constraints on dynamic stability during step adjustments. Twelve healthy young adults avoided a virtual white planar obstacle by lengthening or shortening their steps under free or constrained conditions. When constrained, participants had only one step to avoid the obstacle. The results indicated that center of mass (COM) displacement in the mediolateral (ML) direction and the COM velocity toward the swing-leg side during the crossing step were significantly increased in the long-constraint compared with the long-free condition. Consequently, the extrapolated COM (XcoM) position at the swing foot contact was also located further toward the swing-leg side. However, the distances between the XcoM and base of support (BOS) at the swing foot contact in the ML direction was unchanged because of greater lateral foot placement. In the anteriorposterior (AP) direction, temporal constraints led to greater AP COM displacement. The XcoM–BOS distance in the AP direction was unchanged in the long-constraint condition because of greater step length. However, the value became negative in the short-constraint condition, violating the conditions for dynamic stability, because step length adjustments were obstructed by the spatial constraints of the obstacles. These results suggest that temporal constraints affect postural stability in the AP and ML directions during step adjustments. AP and ML stability at swing foot contact are maintained through adjustments of step length and lateral foot placement, respectively.

Combined diffractive optical elements with adjustable optical properties controlled by a relative rotation: tutorial.

A pair of adjacent transmissive diffractive optical elements (DOEs) forms a combined DOE with tunable optical properties, as, for example, a diffractive lens with an adjustable focal length. The optical properties are controlled by a relative movement of the two DOEs, such as a translation or a rotation around the optical axis. Here we discuss various implementations of this principle, such as tunable diffractive lenses, axicons, vortex plates, and aberration correction devices. We discuss the limits of the tuning range and of diffraction efficiency. Furthermore, it is demonstrated how chromatic aberrations can be suppressed by using multi-order DOEs.

Design, modeling and evaluation of a millimeter-scale SMA bending actuator with variable length

Millimeter-scale continuum bending actuators are useful in minimally invasive surgery to allow distal visualization and manipulation outside the line of sight. This paper presents a new continuum bending actuator based on shape memory alloy (SMA) with variable bending length. It consists of two SMA wires antagonistically configured to produce bidirectional bending under Joule heating. A linearly actuated rigid tube along the longitudinal axis enables continuous bending length adjustment, thus enhancing its workspace and force range. The proposed fabrication method tackles the challenging assembly tasks of maintaining the antagonistic configuration of long SMA wires, and robust electrical and mechanical connection during actuation. A quasi-static model of the actuator based on beam model and SMA constitutive model is presented and verified. The bending actuator was evaluated comprehensively for its workspace, blocked force, and trajectory tracking capability at different bending lengths and under different cooling conditions. It is the first work that demonstrates real-time continuous bending length adjustment in SMA-based bending actuator, leading to the potential development of compact and compliant robotic end effectors with improved distal workspace and force.

Cooperative Self-Assembled Magnetic Micropaddles at Liquid Surfaces.

Cooperative controls of magnetic microswimmers are desired for complex micromanipulation and microassembly tasks. Self-assembled magnetic micropaddles as microswimmers that can locomote freely and cooperate at liquid surfaces are proposed inspired by the paddling motion. The micropaddles are self-assembled with metallic disks under a rotating magnetic field, and they are endowed with controlled propulsion in the precessing field. The micropaddles can locomote freely with a maximum speed of approximately 3.3 mm/s and manipulate objects at the liquid surface. It is found that the micropaddles reverse moving directions at high frequencies and that those with different lengths can locomote in opposite directions under the same precessing magnetic field. Based on the distinctive motion properties, not only could several micropaddles combine into the longer ones but a single micropaddle could also be disassembled into two cooperative partners. Assemblies of different parts based on their cooperation are realized in this study, which is challenging for other types of magnetic microswimmers. Micropaddles with adjustable length, flexible locomotion, and cooperative capability present a promising avenue for various micromanipulation applications.

Indirect markers for length adjustment in distal biceps tendon allograft reconstruction.

Chronic musculotendinous retraction, shortening and fibrosis after distal biceps tendon tears makes a primary reconstruction often difficult or even impossible. Interposition reconstruction with allograft provides a solution, however there is no consensus about appropriate intraoperative graft length adjustment. Therefore, the purpose of this study was to find a practical reference value for distal biceps tendon length adjustment. Three-dimensional surface models of healthy distal biceps tendons were created based on 85 MRI scans. The tendon length was measured from the myotendinous junction to the insertion on the bicipital tuberosity. Inter-epicondylar distance (IED) and radial head diameter (RHD) were measured on antero-posterior radiographs as a surrogate for patient size. Correlations between the tendon length and IED, RHD and patient’s height (PH) were calculated. Mean length of the external part of the distal biceps tendon was 69mm (female 64mm, male 71mm). The tendon length in mm was on average 1.1 times of the IED (mm), 3 times of the RHD (mm) and 0.4 times of PH (cm). Herewith, the tendon length could be predicted within a narrow range of +/-1cm in 84% by using IED, 82% by using RHD and 80% by using PH. Intra- and inter-reader reliabililty of IED and RHD was excellent (R2 = 0.938–0.981). The distal biceps tendon length can be best predicted within 1cm with an accuracy of 82–84% using the IED and RHD with an excellent intra- and inter-reader reliability.

Defining Potential Overutilization of Physical Therapy Consults on Hospital Medicine Services.

Appropriate use of inpatient physical therapy services is important for preventing hospital-associated disability (HAD). We assessed potential overutilization of physical therapy consults on hospital medicine services using the Activity Measure-Post Acute Care (AM-PAC) score. Our sample included 3592 unique admissions (mean age, 66 years; 48% women) at a large academic medical center. Based on an AM-PAC cutoff of >43.63 (raw score, 18) in patients who were discharged to home, 38% of physical therapy consults were considered "potential overutilization." Combined with age <65 years, 18% of consults remained "potential overutilization." After adjustment for age, sex, and length of stay, patients admitted with high mobility scores were 5.38 times more likely to be discharged to home (95% CI, 4.36-2.89) compared with those with low mobility scores. Being more judicious with physical therapy consults and reserving skilled therapy for at-risk patients could help prevent HAD while also having a positive impact on healthcare systems.

Methodological considerations in measuring specific force in human single skinned muscle fibres.

Chemically skinned fibres allow the study of human muscle contractile function in vitro. A particularly important parameter is specific force (SF), that is, maximal isometric force divided by cross-sectional area, representing contractile quality. Although SF varies substantially between studies, the magnitude and cause of this variability remains puzzling. Here, we aimed to summarize and explore the cause of variability in SF between studies. A systematic search was conducted in Medline, Embase and Web of Science databases in June 2020, yielding 137 data sets from 61 publications which studied healthy, young adults. Five-fold differences in mean SF data were observed. Adjustments to the reported data for key methodological differences allowed between-study comparisons to be made. However, adjustment for fibre shape, swelling and sarcomere length failed to significantly reduce SF variance (I2 = 96%). Interestingly, grouping papers based on shared authorship did reveal consistency within research groups. In addition, lower SF was found to be associated with higher phosphocreatine concentrations in the fibre activating solution and with Triton X-100 being used as a skinning agent. Although the analysis showed variance across the literature, the ratio of SF in single fibres containing myosin heavy chain isoforms IIA or I was found to be consistent across research groups. In conclusion, whilst the skinned fibre technique is reliable for studying in vitro force generation of single fibres, the composition of the solution used to activate fibres, which differs between research groups, is likely to heavily influence SF values.

Low excitation spur gears with variable tip diameter

One important source of noise in drive trains are transmissions. In numerous applications, it is necessary to use helical instead of spur gear stages due to increased noise requirements. Besides a superior excitation behaviour, helical gears also show additional disadvantageous effects (e.g. axial forces and tilting moments), which have to be taken into account in the design process. Thus, a low noise spur gear stage could simplify design and meet the requirements of modern mechanical drive trains. The authors explore the possibility of combining the low noise properties of helical gears with the advantageous mechanical properties of spur gears by using spur gears with variable tip diameter along the tooth width. This allows the adjustment of the total length of active lines of action at the beginning and end of contact and acts as a mesh stiffness modification. For this reason, several spur gear designs are experimentally investigated and compared with regard to their excitation behaviour. The experiments are performed on a back-to-back test rig and include quasi-static transmission error measurements under load as well as dynamic torsional vibration measurements. The results show a significant improvement of the excitation behaviour for spur gears with variable tip diameter.