Torsional Measurements Research Articles

A New Error Model and Compensation Strategy of Angle Encoder in Torsional Characteristic Measurement System.

For systems of measurement, geometric errors such as manufacturing and assembly errors could have a significant impact on the accuracy of the angle encoders of the system. In this study, an error model of angular measurement with geometric errors of a torsional characteristic measurement system was developed based on multibody system theory, the aim of which was to reveal the impact of geometric errors on angular measurement and to compensate the measurement error. According to the principle of spatial error transfer, the decomposition of geometric errors is illustrated and the error matrix of geometric errors is constructed by the Denavit–Hartenberg (DH) method. Subsequently, an error compensation function can be obtained and the impact of geometric error on angular measurement is discussed. Finally, we demonstrate by the experimental results of an ultra-autocollimator that the proposed error compensation method reduced the angular measurement error from 3.7% to 0.7%, which shows that the proposed error model can effectively predict the angular measurement error. In addition, it can be seen from the measurement results of the RV reducer that the error of the torsional characteristic measurement system decreased significantly.

Fiber Ring Laser Directional Torsion Sensor with Ultra-Wide Linear Response.

In this paper, a comprehensive passive torsion measurement is performed firstly in a 40-cm-long polarization maintaining fiber-based Sagnac interferometer (PMF-SI), and the non-linear torsion response is found and investigated. Then, a fiber laser torsion sensor (FLTS) with a dual-ring-cavity structure is proposed and experimentally demonstrated, in which the PMF-SI is utilized as the optical filter as well as the sensing unit. In particular, the highly sensitive linear range is adjusted through fine phase modulation, and owing to the flat-top feature of fringes, an ~83.6% sensitivity difference is effectively compressed by the generated lasing. The experimental results show that, without any pre-twisting, the ultra-wide linear response from –175 to 175 rad/m is gained, and the torsion sensitivities are 2.46 and 1.55 nm/rad with high linearity (>0.99) in the clockwise and anti-clockwise directions, respectively. Additionally, a high extinction ratio (>42 dB) and small line-width (~0.14 nm) are obtained in the proposed FLTS, and the corresponding detection limit reaches 0.015 rad/m.

Directional torsion and strain discrimination based on Mach-Zehnder interferometer with off-axis twisted deformations

An all-fiber sensor based on a Mach-Zehnder interferometer (MZI) is proposed and experimentally demonstrated to measure directional torsion and strain simultaneously. The MZI employing a pair of off-axis twisted deformations (OATDs) on single mode fiber (SMF) is fabricated by continuous arc discharge method. It performs OATDs causing permanent twisted distortion to form light beam splitter and combiner of the MZI. The transmission spectrum of the OATDs-MZI has multiple resonance wavelength dips, which correspond to different cladding modes. The torsion and strain measurement can be simultaneously achieved by monitoring changes in the dips of wavelength. Due to the OATDs, the proposed sensor has the ability to distinguish torsional direction, and a strain sensitivity as high as −0.0285 nm/με was obtained. The proposed sensor exhibits excellent torsion and strain resolution of ±0.0611 rad/m and ±0.8232 με. The device has the advantages of low cost, small size, simple preparation steps, short preparation cycle, etc. Due to its excellent performance, it has the potential to become an excellent universal directional torsion and strain sensor.

Analysis of the effect of tibial torsion on tibial osteotomy in knee arthroplasty using a three-dimensional computed tomography-based modelling technique

BackgroundExtramedullary systems are commonly used in knee arthroplasty, with the rod location being determined from the tibial torsion line during surgery. The traditional method for tibial torsion measurement is not in accordance with clinical practice. This study aimed to evaluate proximal and distal tibial torsion using 3-dimensional (3D) computed technology to establish a new evaluation method, as well as to investigate the association between tibial torsion and postoperative alignment deviation.MethodsFifty-five osteoarthritis tibias with >10°varus preoperatively were divided into valgus, neutral, and varus groups based on their postoperative alignment deviation. A new method based on clinical practice was built using a 3D tibial model. Proximal and distal tibial torsions were measured by both the new and traditional methods. In addition, tibial osteotomy that followed the intramedullary osteotomy system was simulated on the 3D model in the varus and valgus groups to investigate the association between tibial torsion and alignment deviation.ResultsProximal tibial torsion was smaller and distal torsion was greater in the valgus group than the other two groups, according to the new method (p = 0.03 and p = 0.02, respectively). No significant difference was found when comparing these torsions by the traditional method (p = 0.782 and p = 0.753, respectively). In the valgus group, the postoperative alignment deviation improved after simulated osteotomy guided by the intramedullary system, while no significant improvement was found in the varus group.ConclusionAccording to this new tibial-rotation evaluation method, valgus deviation in knee arthroplasty was identified as the main cause for knees in which the proximal tibial internal torsion is too small and the distal external torsion is too great. The use of an intramedullary system may help reduce this deviation.Trial registrationProspectively registered.

Measurement of torsion in running shoes – a pilot study

The torsional behavior between rearfoot and forefoot is of great importance for the degree of stabilization of running shoes. However, it is difficult to determine the torsional behavior in the sho...

Commercial Footwear with Lateral Torsional Stiffness that May Reduce Injury Risk in Army Basic Trainees

Musculoskeletal injuries place a burden on the U.S. Military with estimates that 25% of men and 50% of women experience an injury in Army Basic Training. In 2016, 18% of Cadet basic trainees at the U.S. Military Academy (USMA) sustained a lower-extremity (LE) injury. In that sample, Cadets wearing shoes with mild to moderate lateral torsional stiffness (1.30 - 2.29 Newton [N] meters[m]) were 49% less likely to incur any type of LE injury and 52% less likely to incur an overuse LE injury than Cadets wearing shoes with minimal (<.0130 Nm) or extreme (>.0230 Nm) lateral torsional stiffness. PURPOSE: To identify athletic footwear, commercially available at West Point, NY, with mild to moderate lateral torsional stiffness characteristics. METHODS: Twenty (10 shoes men’s size 10, 10 shoes women’s size 8) new shoes of varying brands were included in this analysis. The Shoe Stiffness in Torsion Measurements device and methods of data collection described by Zifchock, were used to quantify lateral torsional stiffness. Each shoe was measured twice by a single rater and averaged for the overall analysis. Rater reliability analyses suggest the SySTM device is useful for repeatable measurements of lateral torsional stiffness. RESULTS: Six out of 20 shoes (2 men’s, 4 women’s) demonstrated mild to moderate lateral torsional stiffness to include; Men’s New Balance Minimus MT10GG, and Nike Flex 2017 RN; Women’s Sketchers Go Run 3, Asics Gel-Fit Sana 3, Nike Free TR 7 Selfie, and Nike Flex Trainer 7. Fourteen out of 20 shoes (8 men’s, 6 women’s) did not demonstrate mild to moderate lateral torsional stiffness. Of those 14 shoes, 13 demonstrated extreme lateral torsional stiffness; Men’s Nike Lunar Fingertap TR, Nike Retaliation TR, Nike Air Zoom Pegasus 34, Asics FuseX Rush, Asics Gel-Contend 4, Brooks Adrenaline GTS 18, and New Balance Trufuse 860v7; Women’s Under Armour Micro G Assert 7; Asics RoadHawk FF, Asics GT 1000-6, Brooks Ghost 10, Adidas Cosmic 2, and New Balance W940GP3. One demonstrated minimal lateral torsional stiffness; Women’s Asics Metrolyte Gem. CONCLUSION: We identified 6 shoes commercially available at West Point, NY, with mild to moderate lateral torsional stiffness. These shoe recommendations can inform Cadet basic trainees on footwear that may be protective of LE injury during USMA Army Basic Combat Training.

Phonons, rotons, and localized Bose-Einstein condensation in liquid He4 confined in nanoporous FSM-16

We present neutron scattering measurements of the phonon-roton and layer modes of liquid helium confined in 28 \AA{} diameter nanopores of FSM-16. The goal is to determine the energy, lifetime, and intensity of the modes as a function of temperature. It is particularly to determine the highest temperature, denoted ${T}_{PR}$, at which well-defined phonon-roton modes are observed at higher wave vector ($Qg0.8$ ${\AA{}}^{\ensuremath{-}1}$) in the nanopores. The temperature ${T}_{PR}$, which can be identified with loss of Bose-Einstein condensation (BEC), can be compared with the superfluid to normal liquid transition temperature, ${T}_{O}$, and other transition temperatures of $^{4}\mathrm{He}$ in the nanopores. The aim is to identify the nature of BEC in a narrow nanopore. Two pressures are investigated, saturated vapor pressure (SVP) and $p=26$ bars. We find that well-defined P-R modes are observed up to temperatures much higher than the conventional superfluid to normal liquid transition temperature, ${T}_{O}$, observed in torsional oscillator measurements, i.e., ${T}_{PR}g{T}_{O}$. At SVP, ${T}_{PR}=1.8$ K and ${T}_{O}=0.9$ K. This supports the interpretation that BEC exists in a localized or partially localized form in the temperature range ${T}_{O}lTl{T}_{PR}$; i.e., there is a localized BEC region lying between the superfluid and fully normal liquid phase, as observed in some other porous media. At close to full filling, the P-R mode energies in FSM-16 are similar to those in bulk liquid $^{4}\mathrm{He}$. However, a substantial P-R mode width at $T\ensuremath{\rightarrow}0$ K and at higher temperatures is observed.

Drillstring Failure—Identification, Modeling, and Experimental Characterization

Abstract Drilling is one of the costliest and risky activities in oil and gas industry due to complexity of interactions with downhole formation. Under such conditions, the uncertainty of drillstring behavior increases, and hence, it becomes difficult to predict the causes, occurrences, and types of failures. Lateral and torsional vibrations often cause failure of bottom hole assembly (BHA), drillstring failure, drill bit, and wall borehole damages. In this work, a model is presented to determine the impact of lateral and torsional vibrations on a drillstring during the drilling operation. The model aims to mimic real drillstring behavior inside a wellbore with regards to its dynamic movements due to multiple real situations such as eccentricity of collars, drill pipe sections, and stick-slip phenomena occurring due to the interaction of the bit and the drillstring with the well formation. The work aims to develop a basis for determining critical operating speeds and design parameters to provide safe drilling procedures and reduce drillstring fatigue failure. Lagrangian approach is used in this study to attain drillstring lateral and torsional vibration coupling equations. The nonlinear equations are solved numerically to obtain the response of the system. In this work, we also present a brief description of an in-house constructed experimental setup. The setup has the capability to imitate the downhole lateral and torsional vibration modes. Parameters from the experimental investigations are incorporated for validation of the mathematical models and for prediction of the drillstring fatigue life. Such investigations are essential for oil/gas industries as they provide solutions as well as recommendations about operating speed, lateral and torsional amplitudes measurements and corrections, and the conditions for avoiding occurrence of natural frequency(ies) of the system.

Polarimetric Sensitivity to Torsion in Spun Highly Birefringent Fibers.

We report on experimental studies of polarimetric sensitivity to torsion in spun highly birefringent fibers. Two classes of spun fibers were examined, namely spun side-hole fibers and birefringent microstructured fibers with different birefringence dispersion, spin pitches, and spin directions. The polarimetric sensitivity to torsion was determined by monitoring a displacement of the spectral interference fringes arising in the output signal because of interference of polarization modes and induced by an additional fiber twist. Both the experimental results and the analytical predictions showed that the sensitivity to torsion normalized to the fringe width in the spun highly birefringent fibers increased asymptotically with the twist rate to the value of 1/ π rad−1. We have also studied the polarimetric response to temperature in the spun side-hole fibers. We have found that, in contrast to the torsional sensitivity, the temperature sensitivity decays asymptotically to zero with increasing fiber twist rate. Therefore, the spun fibers with short spin pitches are especially well suited for torsion measurements because the torsional sensitivity and the range of linear response are both enhanced in such fibers, while at the same time, the cross-sensitivity to temperature is reduced.

주시 상태에서 홍채 이미지에 의한 안구 회선 측정

주시 상태에서 홍채 이미지에 의한 안구 회선 측정

Standardization of torsional CT measurements of the lower limbs with threshold values for corrective osteotomy.

Re-establishing anatomic rotational alignment of shaft fractures of the lower extremities remains challenging. Clinical evaluation in combination with radiological measurements is important in pre- and post-surgical assessment. Based on computed tomography (CT), a range of reference values for femoral torsion (FT) and tibial torsion (TT) have historically been reported, which require standardization to optimize the significant intra- and inter-observer variability. The aims of this study were (re-)evaluation of the reference FT and TT angles, determination of the normal intra-individual side-to-side torsional differences to aid the surgical decision-making process for reoperation, and development of a novel 3D measurement method for FT. In this retrospective study, we included 55 patients, without any known torsional deformities of the lower extremities. Two radiologists, independently, measured the rotational profile of the femora using the Hernandez and Weiner CT methods for FT, and the tibiae using the bimalleolar method for TT. The intra-individual side-to-side difference in paired femora and paired tibiae was determined. A 3D technique for FT assessment using InSpace® was designed. FT and TT demographic values were lower than previously reported, with mean FT values of 5.1°-8.8° and mean TT values of 25.5°-27.7°. Maximal side-to-side differences were 12°-13° for FT and 12° for TT. The Weiner method for FT was less variable than the Hernandez method. The new 3D method was equivocal to the conventional CT measurements. The results from this study showed that the maximal side-to-side tolerance in asymptomatic normal adult lower extremities is 12°-13° for FT and 12° for TT, which could be a useful threshold for surgeons as indication for revision surgery (e.g., derotational osteotomy). We developed a new 3D CT method for FT measurement which is similar to 2D and could be used in the future for virtual 3D planning.

Drillstring Failure: Analytical and Experimental Approach

Drilling is one of the costliest activities in oil and gas industry due to the complexity of interactions with downhole rock formation. Under such conditions, the uncertainty of drillstring behaviour increase and hence it becomes difficult to predict the causes, occurrences, and types of failures. Lateral and torsional vibrations often cause failure of Bottom Hole Assembly (BHA), drillstring failure, drill bit and wall borehole damages. In this work, a model is presented to determine the impact of lateral and torsional vibrations on a drillstring during the drilling operation. The model aims to mimic real drillstring behaviour inside a wellbore with regards to its dynamic movements due to multiple real situations such as eccentricity of collars, drill pipe sections, and stick-slip phenomena occurring due to the interaction of the bit and the drillstring with the well formation. The work aims to develop a basis for determining critical operating speeds and design parameters to provide safe drilling procedures and reduce drill string fatigue failure. Lagrangian approach is used in this study to attain drillstring lateral and torsional vibration coupling equations. The nonlinear equations are solved numerically to obtain the response of the system. In this work, we also present a brief description of an in-house constructed experimental setup. The setup has the capability to imitate the downhole lateral and torsional vibration modes. Parameters from the experimental investigations are incorporated for validation of the mathematical models and for prediction of the drillstring fatigue life. Such investigations are essential for oil and gas industries as they provide solutions and recommendations about operational speed, lateral and torsional amplitudes measurements and corrections, and the conditions for avoiding occurrence of natural frequencies of the system.

Reliability of objective ocular torsion assessment using fundus photography in infantile esotropia

To evaluate the interobserver reproducibility of objective ocular torsion measurements in infantile esotropia using fundus photography analysis. This retrospective observational study was conducted in our ophthalmology department at the University Hospital in Tours from 2009 to 2015. Ocular torsion was assessed using fundus photography and analysed on Adobe Photoshop software within a population of children with infantile esotropia. Two observers, an orthoptist and an ophthalmologist, carried out the evaluation separately. The interobserver agreement was calculated for quantitative measurement by the interclass correlation coefficient (ICC) and by Cohen's Kappa coefficient for qualitative assessment. A total of 200 eyes (100 subjects, mean age: 6.88 years) were assessed. Statistical analyses for quantitative measurements resulted in an ICC of 0.98 (95% CI, 0.97-0.99) for right eyes, 0.96 (95% CI, 0.95-0.97) for left eyes, 0.98 (CI 95%, 0.97-0.98) for pre- operative eyes and 0.96 (95% CI, 0.95-0.97) for postoperative eyes. The ICC calculated on all four hundred fundus photographs was 0.97 (95% CI, 0.97-0.98). The interobserver agreement for qualitative measurements resulted in a Kappa coefficient of 0.91 for right eyes, 0.85 for left eyes, 0.90 for preoperative eyes and 0.86 for postoperative eyes. The analysis of all four hundred eyes returned a Kappa coefficient of 0.88. Objective ocular torsion assessment using our procedure, whether by an orthoptist or ophthalmologist, is a reliable and reproducible method for the management of infantile esotropia.

Simultaneous Measurement of Axial Strain, Bending and Torsion With a Single Fiber Bragg Grating in CYTOP Fiber

This paper presents the development of a three-dimensional (3-D) displacement sensor based on one fiber Bragg grating (FBG). In order to obtain higher sensitivity and dynamic range, the FBG is inscribed in low-loss, multimode, cyclic transparent amorphous fluoropolymers using the direct-write, plane-by-plane femtosecond laser inscription method. The proposed sensor is based on the influence of each displacement condition, namely, axial strain, torsion, and bending on the FBG reflection spectrum. Such influence is analyzed with respect to the FBG wavelength shift, reflectivity, and full width half maximum. The operation principle and theoretical background of the proposed approach is numerically analyzed by means of finite element analysis for the strain along the grating length and coupled-mode theory with a modified transfer matrix formulation for the FBG spectrum. The sensor is experimentally characterized and validated in which the results show good agreement between the applied axial strain, bending, and torsion with relative errors below 5.5%. Thus, the proposed sensor is an interesting alternative for measuring displacements in 3-D applications, such as movement analysis and the instrumentation of novel soft robots.

Permeability and seismic-frequency elasticity of cracked glass

With the objective of improved understanding of frequency-dependent properties of cracked and fluid-saturated media, permeability and forced oscillation measurements are being undertaken on dry and fluid-saturated cracked glass media. In particular, we address some of the issues outstanding from a prior intensive study across a wide range of frequency. Our preliminary results demonstrate the potential of improved methods for the measurement of the very low permeabilities of such cracked glass media, the feasibility of torsional forced oscillation measurements at longer oscillation periods and lower differential pressures, and the benefits of improved alignment of our specimen assembly for complementary flexural oscillation tests. Such complementary flexural oscillation tests on glass-rod specimens are expected to provide further insight into the relevant fluid-flow regimes.

Theoretical and Experimental Investigations on Transient Run-Up Procedures of Journal Bearings Including Mixed Friction Conditions

This paper focuses on the operating behavior of journal bearings for industrial machinery application during run-ups. For this purpose, a numerical simulation code that is based on a two-dimensional extended and generalized Reynolds equation and a full three-dimensional energy equation, was advanced by a theoretical model considering the effects of mixed friction and warming of journal components during start-up. The mixed friction routine contained the elastic half-spaces model proposed by Boussinesq, which considers the influence of rough surfaces by implementing flow factors and calculates additional stiffness and dissipation in areas with solid interactions. Furthermore, a transient term was added in the energy equation to consider the thermal inertia of journal, and bearing to ensure a realistic heating during run-ups. Results of the prediction were compared to experimental data taken from a special test rig built up for validation procedures. Besides the conventional sensors for temperature, oil flow, and relative motion between shaft and stator, a contact voltage measurement was installed to determine the intensity of mixed friction. The evaluation of experimental data by Stribeck curves, based on a shaft torsion measurement, indicated a significant influence of run-up time on frictional moment. The friction coefficient of the rotor bearing system was strongly influenced by the run-up time. A short run-up time reduced the frictional coefficient in the mixed lubrication regime while the opposite behavior was observed in the hydrodynamic lubrication regime. The numerical code predicted these tendencies in good agreement with experimental data, however, only if the transient energy model was applied.

Flexural-torsional buckling behaviour of fixed-ended hot-rolled austenitic stainless steel equal-leg angle section columns

The present paper shows an experimental and numerical modelling investigation of the flexural-torsional buckling behaviour and load-carrying capacities of fixed-ended hot-rolled austenitic stainless steel equal-leg angle section columns. The testing programme was conducted on four austenitic stainless steel angle sections and involved material testing, initial global and torsional imperfection measurements and sixteen fixed-ended column tests. This was followed by a numerical simulation study, where the numerical models were firstly developed to validate against the experimental data and then utilised to perform numerical parametric studies to generate additional results over a broader range of member lengths and cross-section geometric dimensions. The derived test and finite element results were carefully analysed and then utilised to evaluate the accuracy of the established design rules in Europe, America and Australia/New Zealand. Comparisons of the failure loads derived from the experimental and numerical studies with the corresponding codified flexural-torsional buckling strength predictions revealed an unduly high level of conservatism and scatter. Extension of the direct strength method to carbon steel equal-leg angle section columns has been recently made, and the applicability of the approach to fixed-ended hot-rolled austenitic stainless equal-leg steel angle section columns was also assessed. The new approach was generally shown to yield more precise flexural-torsional buckling resistance predictions than the existing design standards, but a large portion of the predictions were unsafe, indicating that further improvements are required.

Patient-Specific Restoration of Biomechanics in Total Hip Arthroplasty.

Restoration of biomechanics is crucial in total hip arthroplasty, in order to ensure a free postoperative range of motion for activities of daily life. Failure may result in impingement and thus instability, limping and finally patient dissatisfaction. In daily practice, preoperative templating is usually performed on magnification-corrected, plain radiographs of the hip. Due to the divergence of the X-ray beams and the position of the pelvis in relation to the film, measurements on plain radiographs are susceptible to error. Whereas leg length measurements are highly accurate, femoral offset is frequently underestimated on plain radiographs. The benchmark for acceptable postoperative leg length and offset differences is still under debate in the literature. However, discrepancies of 1 cm in relation to the non-affected, contralateral side should not be exceeded. Gait analysis is able to detect even differences in leg length and offset above 5 mm due to altered gait kinematics. For intraoperative control of leg length and offset, a variety of different methods have been described in the literature. Beside alignment guides, rulers and other tools, intraoperative fluoroscopy and computer-guided navigation allow the surgeon to intraoperatively analyse leg length and offset changes. Both techniques show high accuracy, although the precision is higher for navigation with a reduced number of outliers. For measurement of stem torsion, computed tomography is the gold standard. However, stem torsion can also be evaluated on plain hip radiographs by measuring the projected prosthetic neck-stem angle. Native femoral anteversion can be assessed by the size of the lesser trochanter. Since the version of the femoral stem can highly vary from the native femoral anteversion, the Isthmus Ratio (iRatio) - the relationship between canal isthmus and calcar isthmus in the anteroposterior and Lauenstein view - helps to predict the torsion of the final intraoperative stem.

A Fiber Bragg Grating Based Torsional Vibration Sensor for Rotating Machinery.

This paper proposes a new type of torsional vibration sensor based on fiber Bragg grating (FBG). The sensor has two mass ball optical fiber systems. The optical fiber is directly treated as an elastomer and a mass ball is fixed in the middle of the fiber in each mass ball fiber system, which is advantageously small, lightweight, and has anti-electromagnetic interference properties. The torsional vibration signal can be calculated by the four FBGs’ wavelength shifts, which are caused by mass balls. The difference in the two sets of mass ball optical fiber systems achieves anti-horizontal vibration and anti-temperature interference. The principle and model of the sensor, as well as numerical analysis and structural parameter design, are introduced. The experimental conclusions show that the minimum torsional natural frequency of the sensor is 27.35 Hz and the torsional vibration measurement sensitivity is 0.3603 pm/(rad/s2).

Bilateral Low-Dose Computed Tomography Assessment for Post-Operative Rotational Malalignment After Intramedullary Nailing for Tibial Shaft Fractures: Reliability of a Practical Imaging Technique

IntroductionThe purpose of this study is to evaluate the intra- and inter-observer reliability of low-dose protocolled bilateral postoperative Computed Tomography (CT)-assessment of rotational malalignment after intramedullary nailing (IMN) of tibial shaft fractures. Materials and methods156 patients were prospectively included with tibial shaft fractures that were treated with IMN in a Level-I Trauma Centre. All patients underwent post-operative bilateral low-dose CT-assessment (effective dose of 0.03784 – 0.05768 mGy) as per hospital protocol. Four observers performed the validated reproducible measurements of tibial torsion in degrees, based on standardized techniques. The Intra-Class Coefficient (ICC) was calculated to evaluate intra- and inter-observer reliability. The intra- and inter-observer reliability was categorized according to Landis and Koch. ResultsIntra-observer reliability for quantification of rotational malalignment on post-operative CT after IMN of tibial shaft fractures was excellent with 0.95 (95% CI = 0.92-0.97).The overall inter-observer reliability was 0.90 (95% CI = 0.87-0.92), also excellent according Landis and Koch. ConclusionFirstly, bilateral post-operative low-dose –similar radiation exposure as plain chest radiographs– CT assessment of tibial rotational alignment is a reliable diagnostic imaging modality to assess rotational malalignment in patients following IMN of tibial shaft fractures and it allows for early revision surgery. Secondly, it may contribute to our understanding of the incidence-, predictors- and clinical relevance of post-operative tibial rotational malalignment in patients treated with IMN for a tibial shaft fracture, and facilitates future studies on this topic.