Angle Off Research Articles

Link Between Geometrical and Physical Property Changes Along Nankai Trough With Slow Earthquake Activity Revealed by Dense Reflection Survey

AbstractWe examined the possible factors affecting the spatial distribution of very low frequency earthquakes and tremors in the shallow megathrust of Nankai Trough (<30 km) using a dense network of prestack depth migrated profiles at the frontal wedge. Geometrical parameters examined were decollement roughness, taper angle, and underthrust thickness. Physical properties such as effective basal friction (μb) and pore pressure ratio (λ*) were calculated from the taper angle and p‐wave velocity. Regions of low λ* (0.39 ± 0.08) and smooth decollement showed no slow earthquake activity. In contrast, high activity of slow earthquakes was observed in areas with a rough decollement due to the presence of subducted seamounts or bathymetric highs. The low taper angle (3.8°) off Muroto where slow earthquakes also occur translates to a wide zone of low μb (0.21 ± 0.06) and high λ* (0.66 ± 0.06). However, our results also show that slow earthquakes don't always occur in areas with high λ*.

Noncollinear magnetic order in epitaxial thin films of the centrosymmetric MnPtGa hard magnet

Magnetic systems exhibiting spin-canted states have garnered much attention recently for their promising rich exotic properties driven by the real-space spin textures and competing magnetic orders. In this study, we present the structural and magnetic properties of hexagonal 60 nm MnPtGa epitaxial thin films grown by magnetron sputtering on Al2O3(0001) single-crystalline substrates. The MnPtGa film crystallizes in the centrosymmetric P63/mmc (No. 194) space group, showing perpendicular magnetic anisotropy along the c-axis, with a Curie temperature TC = 263 K. In addition, the MnPtGa film undergoes a spin reorientation transition at Tsr = 160 K. We investigated the MnPtGa magnetic ground states using single-crystal neutron diffraction. A structurally forbidden (001) magnetic Bragg reflection emerges below Tsr, indicating the existence of a spin-canted state, where the magnetic moments align ferromagnetically perpendicular to the basal plane, and a non-zero in-plane component exhibits an antiferromagnetic ordering along the c-axis. At 2 K, the refined magnetic moments of Mn are μz = 4.2(4) μB and μx = 1.5(3) μB, projected onto the c-axis and basal plane, respectively. Hence, we determined a 20° Mn spin canting angle off from the c-axis.

The relation between in-plane fiber waviness severity and first ply failure in thermoplastic composite laminates

The influence of in-plane fiber waviness on the first ply failure of quasi-isotropic thermoplastic composite laminates was investigated. The failure mode and stress at first failure were studied by using a four-point bending test and an end-loaded bending (ELB) test. The experimental results confirm that no undesirable stress concentration due to load introduction occurred in the ELB test, thereby supporting the use of this test as an alternative method to measure stress at failure. The experiments demonstrated that waviness severity affects stress at first failure and compressive damage development. The stress at first failure initially decreases with increasing maximum waviness angle and levels off as the angle starts exceeding 20°. These results reinforce the hypothesis from previous research which suggests that wavy ply compressive strength is less sensitive to changes in severity at larger angles. Furthermore, it was found that kinking failure was the dominant failure mode for maximum waviness angle up to about 45°. No kink band was observed in wavy regions with maximum angles above 45° when there was another wavy region with a lower maximum angle in the same specimen. This means that failure is not necessarily initiated at the location where waviness is most severe.

Computed Tomographic Evaluation of Mid-thoracic Vertebral Corridors in Normal French Bulldogs

Objectives: (1) To report internal measurements of thoracic vertebral bone morphology and (2) identify safe and clinically applicable surgical implant corridors in the T7-T9 thoracic vertebrae of French Bulldogs. 
 Study Design: Observational, cross‐sectional, descriptive study.
 Sample Population: Seven client-owned French Bulldogs with normal thoracic vertebrae.
 Methods: Computed tomographic (CT) studies of normal French Bulldogs were reviewed. Multiplanar reconstruction of the CT images was used to determine thoracic vertebral corridors. Corridor measurements included the width, length, insertion distance off midline, and angle off midline (sagittal) for each thoracic vertebra. One‐way analysis of variance was used to detect differences between groups.
 Results: Measurements of vertebral corridor width (p>0.9848), length (p>0.8113), implant center (p>0.9282) and angle (p>0.3609) did not differ between each vertebra. The average vertebral corridor width was 4.5 ± 0.7 mm. The average corridor length was 17.2 ± 2.5 mm. The average corridor angle was 22.3 ± 1.9 °. The mean distance the proposed implant center was from the vertebral midline was 8.2 ± 1.1 mm. Inter-observer agreement of corridor length and implant center was good but poor for corridor angle and width.
 Conclusion: Based on average corridor width and length, commercially available cortical screws or pins can be utilized for implants in this region of the thoracic spine. The angle of corridor trajectory from a dorsal approach seems most applicable for T7-T9.
 Clinical Significance: Vertebral corridors can be measured using CT-MPR, and implant specifications and angles derived. Surgical guides can also be created to guide implant placement. This approach provides a simple and accurate method to guide the placement of thoracic vertebral implants.

Computational Bayesian inference of range and depth of a mobile scatterer in a refractive ocean waveguide with a limited vertical aperture array

A computational Bayesian method is presented for inference from a limited vertical aperture regarding the range, depth and speed of a submerged large mobile object. Closely spaced multipath arrivals in Doppler and vertical angle off of the target in a refractive environment are addressed in the presence of uncertainty in the ambient acoustic noise power. Vertical angles and Doppler frequencies of the arrival structure are jointly inferred and their posterior density is mapped to the object’s range, depth, and speed through acoustic ray interpolation. A case study with the classic Munk sound speed profile is presented to lend credence to the approach.

Pengaruh Double Chamfer terhadap Distribusi Suhu dan Daerah Zpl pada Sambungan Las Gesek AL6061 dengan Simulasi Komputer

Welding is one of the metal joining processes in manufacturing. CDFW (continuous drive friction welding) is a welding process to join two workpieces by applying pressure at one end of the object and rotating another one where the friction action applies at interface. The purpose of this study is to study temperature distribution on the surface of the welding area and the heat-affected zone represented by a fully plasticized zone (Zpl) and to get an insight of a friction welding process. The variables of CDFW used were double chamfer angle, upset pressure, and burn off length. The initial area of friction was equal that is at a diameter of 14 mm. The method of modeling the CDFW friction welding is via computer simulations using ANSYS 18.1 software. This research uses aluminum material type Al6061. The Taguchi method was applied in designing the simulations. In this modeling, the model with the double chamfer of 15 °, the upset pressure of 120 MPa, and the burn-off length of 9 mm has a small ZPl area of 10.256 mm2. Whilst the specimen model, with a double chamfer angle of 45 °, the upset pressure of 240 MPa, and the burn-off length of 7 mm has a large Zpl area of 56.55mm2. The area of a narrow fully plasticized area caused by small chamfer angle and an upset pressure of 240 MPa. The area of fully plasticized zone shows how much material can be integrated during the friction welding process and how much strength of the weld metal. The model with the chamfer angle of 15 º, the upset pressure of 240 MPa, and the burn-off length of 9 mm has the widest temperature distribution and the highest maximum temperature. Meanwhile, the model with the chamfer angle of 30º, the upset pressure of 120 MPa, and the burn-off length of 9 mm has the narrowest temperature distribution and the lowest maximum temperature. The smaller chamfer angle increased upset pressure and burn-off length result in the wider temperature distribution, higher maximum temperature, and smaller Zpl.

Computed tomography evaluation of proposed implant corridors in canine thoracic vertebrae.

Identify acceptable implant corridors in the normal canine thoracic vertebrae (T) from T1 to T9. Retrospective study. Computed tomographic (CT) studies of normal canine thoracic spines (n=39). CT imaging studies of normal T1-T9 canine spines were evaluated by five independent observers. Each identified a proposed corridor, measured the width, length, and angle off mid-sagittal that the corridor occupied. CT studies were from 39 dogs weighing 3.19-60 kg (mean 10.72, SD 9.9 kg). Vertebral corridors ranged in average width from 3.8 to 5.2 mm, the widest being located at T1. They ranged in average length from 13.3 to 17.5 mm, shortest being T1 and longest being T6. The angle of corridors varied the most between individual vertebrae at T1-T3. The average corridor angles were: T1=38°, T2=32°, T3=27°, T4=26°. T5-T9 angle ranged from 23° to 24°. The average dimensions of corridors measured in dogs weighing 3.1-60 kg were consistent with those of commercially available cortical screws and pins. Corridor trajectories identified in this population can be achieved from a dorsal approach between T5 and T9. A dorsal approach for implant placement would be challenging for T1-T4 due to the variability found in these vertebrae as well as regional anatomical constraints.

Three-dimensional wind profiles using a stabilized shipborne cloud radar in wind profiler mode

Abstract. In this study, a shipborne 95 GHz Doppler cloud radar mounted on a stabilized platform is used to retrieve vertical profiles of three-dimensional (3D) winds by sequentially pointing the stabilized platform in different directions. A specific challenge is that the maximum angle off zenith is 8∘, which implies that the projection of the horizontal wind components onto the radar beam directions is a small component of Doppler velocity in most cases. A variational 3D wind retrieval technique is then described, allowing for 1 min 3D wind profiles to be retrieved. Statistical comparisons with 3-hourly radiosonde launches from the ship indicate that horizontal wind profiles can be obtained from such cloud radar observations at small off-zenith angles with biases less than 0.2 m s−1 and standard deviations of differences with radiosonde winds less than 2.5 m s−1.

Does BetterBack Lumbar Support and Posture Trainer Decrease Back Pain and Improve Posture?

Background: The incidence of Low Back Pain (LBP) in the United States is a common occurrence. One proposed cause is poor posture characterized by reduced lumbar lordosis while sitting. Proper retraining of seated posture could potentially increase lumbar lordosis and therefore reduce LBP. Various lumbar support devices, such as the BetterBack device, have been designed to decrease pain and improve posture, however, there is limited evidence to support these claims. Methods: 18 subjects participated in a two-week study during which they wore the BetterBack device for 15 minutes per day for 14 days. Posture was analyzed using the PostureScreen® and SitScreen® mobile application. Participants rated pain with a Visual Analog Scale (VAS) each day before and after wearing the device. Results: Average daily pain scores for all subjects after wearing the device were significantly less (p<0.05) than before wearing the device, with a mean decrease of 1.56 cm on the VAS. Pain scores were decreased on day 15 compared to initial scores, but these changes were not significant. Several postural measurements showed significant mean improvements, including the initial sitting thorax angle and forward head shift off of vertical in standing. The trunk thigh angle while sitting with the device on also improved. Conclusion: The BetterBack device provided effective lumbar support immediately reducing LBP, but did not carryover without the device. Significant improvements were found in some of the postural measurements, however, the interpretation of the effectiveness of the device is limited by a small effect size.

Analysis on iron loss of switched reluctance motor under PWM mode

PurposeThis paper aims to establish a modified variable coefficient calculation model to analyse the control parameter effect on the iron loss of switched reluctance motor under pulse width modulation (PWM) mode.Design/methodology/approachThe finite element model is solved to get the flux density by python language. Due to non-sinusoidal flux density feature and the effect of PWM excitation, the Fourier transform is applied in consideration of harmonic components. To improve the accuracy of iron loss computation, the effect of minor loops is considered by using the rain-flow counting method.FindingsWhen the speed fluctuates around the set speed and the fluctuations are relatively small, it is useful to reduce the iron loss with smaller duty ratio and turn-on angle or greater duty ratio and smaller turn-off angle. The iron loss is less affected by chopping frequency, while the iron loss increases obviously with higher conduction angles. The iron loss under non-energy-returnable-voltage-chop mode is greater than energy-returnable-voltage-chop mode.Originality/valueThe modified variable coefficient MIEM5 iron loss model is proposed to improve the accuracy of iron loss calculation. Then the control parameters such as duty ratio, chopping frequency, turn on angle and turn off angle are analysed under PWM mode.

Experimental study of Castellated Steel Beams

In this study an investigation of castellated beam are presented. The experimental and analytical results of seven simple castellated beams and other one has webbed section are summarized in this study. The target of the search was to study the structural behavior and mode of failure of castellated beams which have different geometric shape of hole and varies lengths span of beams, and attempt to find out the possibility of Biodgett equation and Halleux equation to determine ultimate and limit load respectively. Four angle off cutting were used to achieve the change in the geometry of hole (45, 50, 60 and 90 degree). The specimens were made from IB 203x133x25 and were expanded to 1.5 times the standard depth. Ultimate and limit load, load-deflection relation shapes and mode of failure were presented and discussed. The experimental results showed that the ultimate and limit load of castellated beams decreases with increasing the angle of cutting and Biodgett equation gives acceptable results for estimating ultimate load when the angle of cutting 50° or less. Also it is found that the limit load of castellated beam by Haleux equation is incorrect when the angle of cutting greater than 50°. As well as ANSYS-12 was used to analysis these beams by nonlinear finite element method. Four- nodes shell element (SHELL 181) was used to represent the castellated and webbed beams. This model was validated by comparison of the experimental and numerical results of ultimate load and their corresponding modes of failure.

Magnetic field assisted droplet manipulation on a soot-wax coated superhydrophobic surface of a PDMS-iron particle composite substrate

We report controlled motion of aqueous droplets on soot-wax coated superhydrophobic surface of a PDMS-iron particle composite substrate. The surface profile around a droplet is altered due to magnetic force acting on the iron particles embedded in the substrate, which leads to droplet motion. The contact angle and roll off angle depend on the soot deposit time and particle distribution. Endurance test is performed to confirm stability of the surface. The deformation behaviour of the substrate is studied with particle size, surface to magnet gap and the cone angle of the magnet. The proposed surface could find applications in the manipulation of sample drops in biological and chemical assays.

Visualization research on spray atomization, evaporation and combustion processes of ethanol–diesel blend under LTC conditions

Utilization of ethanol in diesel engines has been widely studied by means of engine experiments and emission detection. However, pertinent studies on the spray combustion process of ethanol–diesel blends are scarce. In order to verify the effect of ethanol in modern diesel engines, an experiment is conducted to visualize the spray combustion process of ethanol–diesel blend under LTC conditions. Stages including atomization, evaporation and combustion, are investigated individually to realize synergistic analysis. Meanwhile, considering the long time scale of combustion after fuel injection finishes, characteristics during and after injection period are both targeted in this paper. Moreover, measurement of macroscopic characteristics, such as spray tip penetration, spray spreading cone angle and flame lift off length, provides a quantitative profile of the spray structure. Results show that, evaporation, different from atomization, has little influence on spray penetration, but promotes the spray spreading angle and spray projected area. So does combustion, which enlarges the spray projected area further. Ignition takes place on the periphery behind the spray tip, then quickly extends to the whole head of the spray and forms a U-shape diffusion structure. After the injection period, the residual spray tail develops into wavelike structures due to absence of subsequent entrainment force. Also, the penetration speed falls greatly to an extent much slower than flame propagation, which frees the flame from the lift-off effect. Subsequently, the flame propagates upstream towards the nozzle orifice. After consumed all fuel in the spray tail, flame retreats downstream to the far end and combusts for a time much longer than the injection duration.

Analysis and Characterization of a Wide-Angle Impedance Matching Metasurface for Dipole Phased Arrays

The effects of mutual coupling impact the performance of phased arrays as the beam is scanned off broadside. Wide-angle impedance matching (WAIM) alleviates this problem from a transmission-line impedance matching viewpoint, increasing the useable scan range of the array. Traditionally, a dielectric slab is placed at some distance above the array, resulting in a match at some given angle off broadside. We propose a simpler and more effective solution, replacing the dielectric slab with an ultra-thin metasurface composed of a sheet of split-ring resonators (SRRs) to improve the scanning characteristics of a dipole phased array. It is shown that the presence of the metasurface results in significant improvements in multiple scan planes. A generalized equivalent transmission-line model is introduced for the classical WAIM configuration and adapted for the metasurface. A quasi-analytical model based on the equivalent transmission-line model and the extracted scattering parameters of the metasurface properly predicts the scan range of the full structure, and allows for an accelerated design process.

The Pre-Schwarzian Norm Estimate for Analytic Concave Functions

LetDdenote the open unit disk and letSdenote the class of normalized univalent functions which are analytic inD. LetCo(α)be the class of concave functionsf∈S, which have the condition that the opening angle off(D)at infinity is less than or equal toπα,α∈(1,2]. In this paper, we find a sufficient condition for the Gaussian hypergeometric functions to be in the classCo(α). And we define a classCo(α,A,B),(-1≤B&lt;A≤1), which is a subclass ofCo(α)and we find the set of variabilities for the functional(1-|z|2)(f″(z)/f′(z))forf∈Co(α,A,B). This gives sharp upper and lower estimates for the pre-Schwarzian norm of functions inCo(α,A,B). We also give a characterization for functions inCo(α,A,B)in terms of Hadamard product.

SU-E-T-152: Error Sensitivity and Superiority of a Protocol for 3D IMRT Quality Assurance

Purpose: To test if the parameters included in our 3D QA protocol with current tolerance levels are able to detect certain errors and show the superiority of 3D QA method over single ion chamber measurements and 2D gamma test by detecting most of the introduced errors. The 3D QA protocol parameters are: TPS and measured average dose difference, 3D gamma test with 3mmDTA/3% test parameters, and structure volume for which the TPS predicted and measured absolute dose difference is greater than 6%. Methods: Two prostate and two thoracic step-and-shoot IMRT patients were investigated. The following errors were introduced to each original treatment plan: energy switched from 6MV to 10MV, linac jaws retracted to 15cmx15cm, 1,2,3 central MLC leaf pairs retracted behind the jaws, single central MLC leaf put in or out of the treatment field, Monitor Units (MU) increased and decreased by 1 and 3%, collimator off by 5 and 15 degrees, detector shifted by 5mm to the left and right, gantry treatment angle off by 5 and 15 degrees. QA was performed on each plan using single ion chamber, 2D ion chamber array for 2D gamma analysis and using IBA's COMPASS system for 3D QA. Results: Out of the three tested QA methods single ion chamber performs the worst not detecting subtle errors. 3D QA proves to be the superior out of the three methods detecting all of introduced errors, except 10MV and 1% MU change, and MLC rotated (those errors were not detected by any QA methods tested). Conclusion: As the way radiation is delivered evolves, so must the QA. We believe a diverse set of 3D statistical parameters applied both to OAR and target plan structures provides the highest level of QA.

Lumbar alignment and clinical outcome after single level asymmetrical transforaminal lumbar interbody fusion for degenerative spondylolisthesis with local coronal imbalance.

Transforaminal lumbar interbody fusion (TLIF) is widely accepted for the treatment of lumbar arthrodesis. However, the exact characteristics of TLIF depend on the number, location, shape, or materials of the interbody implants, and the type of posterior instrument. Clinical and biomechanical characteristics of each TLIF procedure are still unclear. The present study investigated the clinical and radiological improvements after single level asymmetrical TLIF, in which a single box-shaped spacer was obliquely inserted into the intervertebral space, for lumbar degenerative spondylolisthesis in patients with or without local coronal imbalance (LCI) at the operated level. The clinical records of 60 patients who underwent single level asymmetrical TLIF augmented with the pedicle screw fixation system from January 2005 to January 2011, were retrospectively reviewed. The patients were divided into the LCI group (n = 19) and non-LCI group (n = 41), based on segmental lateral translation or disc wedging at the operated site. Clinical recovery was significantly good in both groups at 2 years after surgery, but improvement of low back pain was significantly worse in the LCI group. Radiological examination revealed that the mean lumbar scoliotic angle was significantly worse in the LCI group postoperatively. Preoperative greater scoliotic angle and coronal off balance of the lumbar spine were related to unfavorable radiological outcomes. The present study showed that single level asymmetrical TLIF is an acceptable method for achieving good clinical and radiological outcomes for patients with symptomatic degenerative spondylolisthesis, however, the clinical benefits and realignment are limited if the patient has LCI at the operated site with greater scoliotic angle or coronal off balance of the lumbar spine.

Flow Feature Near Unswept and Swept Finit Span Wing with Smooth and Wavy Surface at Stall Angle of Attack

Incompressible flow feature at near stall angle off attack on classical and wavy surface wing with aspect ratio λ = 3,7 at Reynolds number 1,5 · 105 was investigated. Such kinds of the wings at the same Reynolds number are employing on micro air vehicle. Vitality of the small aircraft at near ground atmospheric condition flight depends from predictable wing behavior at near stall angle of attack. Separation and attached flow structure at lee surface of wavy and classical wing was shown by oil-film visualization at sweep and no sweep angle condition. It was shown the wavy wing at no sweep condition has the stall angle of attack lager than classical one. At post-stall angle of attack α = 9º for classical wing sweep angle increasing from 15º to 45º results to changing from separation flow regime to attached one. On wavy wing at the same angle of attack and sweep angle from 0º to 45º the attached flow is observed only. In practice, this means that micro air vehicle will easy controlling by automatic system and will fall in stall regime rarely

Growth kinetics and size-dependent wetting of Ag/α-Al2O3(0001) nanoparticles studied via the plasmonic response

The growth of vapour-deposited silver nanoparticles on α-Al2O3 was studied in situ from 190 to 675 K by surface differential reflectivity spectroscopy in the UV–visible range. Changes in size, shape and density were derived from the plasmonic response modelled in the framework of interface susceptibilities by assuming that supported clusters were in the form of truncated spheres. The sticking coefficient of silver on alumina is close to one up to T ≃ 575 K before entering a regime of incomplete condensation. The Arrhenius dependence of the saturation density indicates a nucleation on defects at low temperature (T ≤ 300 K) and detrapping above. The particle size D evolution follows temporal power laws, independent of temperature and flux, which characterize the growth (D ∼ t0.31) and coalescence (D ∼ t0.55) of the film. These are indicative of the growth of isolated particles at constant density and dynamic coalescence, respectively. The wetting angle of the silver clusters is shown to increase during the growth regime, which is assigned to a combination of surface stress and mismatch-induced strain, and to decrease upon coalescence, which is attributed to plastic relaxation. For particles larger than 10 nm in size, the values of contact angle and adhesion energy level off with asymptotic limits (θc = 127.5° ± 1° and 0.48 ± 0.02 J m−2) that nicely agree with tabulated data. This work highlights the ability of nanoplasmics to monitor in situ the growth kinetics of thin supported films.

Influence de la malposition rotatoire de l’implant condylien dans les échecs de prothèse unicompartimentale médiale du genou: Évaluation à l’aide d’un modèle géométrique dans une série de 276 interventions avec un récul de 7 à 15 ans

Purpose of the study Rotatory malposition of the femoral component of a unicompartmental knee arthroplasty (UKA) is a key element of mechanical failure despite proper alignment and position of the tibial implant. The purpose of this study was to describe a method for measuring femoral implant rotation on the anteroposterior x-ray using an original geometric model. Material and methods 276 medial UKA (227 non-cemented Uni Goeland, Depuy; Uni, AMP) and 49 cemented (Miller-Galante, Zimmer) were reviewed and analyzed at a mean 11 years (range 7 - 15) using the Knee Society Score. Mean objective and functional scores were 43 and 47 points preoperatively. Postoperative alignment and position of the femorotibial contact point were determined. The frontal and sagittal position of the tibial plateau was noted by the angle formed with the mechanical axis. Angles α and β of the femoral implant formed between the mechanical axis and the greater condylar axis and the inferior condylar line passing through the apex of the condylar convexity respectively were measured on the AP view. Frontal rotation (angle β) of the femoral implant reflected the orientation of the distal condylar cut. The frontal measurement (angle α) was validated using simple geometric formulas: knowing angles α and β and the size of the implant and the displacement of the point of contact was measured together with the true rotation of the femoral implant or anteroposterior divergence, function of the difference α−β which is its frontal projection and reflects the orientation of the posterior condylar cut. Results Mean alignment was 3° varus. At last follow-up, outcome was satisfactory in 81.2% of the knees (224 UKA). Mean objective and functional scores were 90 and 87 points. Angles α and β were parallel and orthogonal to the mechanical axis or off by less than 4̊ external rotation (+6° to -4°). The mean difference α−β (frontal projection of the femoral implant transverse rotation) was 1°. The point of contact was 4 mm or less from the middle of the tibia. Failures were observed in 18.8% of knees (52 UKA): 4 for diverse reasons and 48 for mechanical failure, including 3 with polyethylene wear without loosening (two by eccentric point of contact and neutral position and one by inverted misalignments). 45 UKA (16.3%) presented loosening of the tibial plateau alone with rotatory femoral malposition: mean a angle off 13% from the mechanical axis (+16° to -9°), mean β angle off 8° (+12° to -8°), mean α−β difference 5°, femoral implant in square position on polyethylene with a peripheral point of contact ≥ 5 mm from the middle of the tibial plateau. The tibial implant exhibited mean varus of 1.5°. Discussion The main cause of failure was rotatory malposition of the condylar implant often associating frontal with transversal rotation. This increased mediolateral translation of the point of contact during knee motion causing abrasion and excessive pressure on the medial portion of the plateau. Frontal malrotation externalizes the posterior cut on the condyle tilted by the varus position, without correcting the varus of the mechanical axis in flexion. To avoid such prosthetic malrotations, three corrections must be made before making the bone cuts: cancel the external rotation of the condyles in flexion by positioning the distal cut guide in extension; re-establish the mechanical axis by reducing the internal tilt of the condyles resulting from the varus position both in extension (distal cut) and flexion (posterior cut). Improved instrumentations and reproducible techniques are needed to re-establish the 3D anatomic orientation of the femoral component, a key element for longer life of unicompartmental prostheses. This method for measuring the rotation of the femoral implant and the displacement of the point of contact using a geometric model applied to the AP view is useful for better understanding UKA failures.