45 results found
Akinnola O, Vardakastani V, Kedgley A, 2020, The effect of planar constraint on the definition of the wrist axes of rotation, Journal of Biomechanics, ISSN: 0021-9290
Instantaneous helical axes (IHAs) and screw displacement axes (SDAs) are commonly used to investigate joint functional axes of rotation. In the wrist, these have often been obtained through in vitro motion analysis. These definitions are then employed for in vivo applications, such as the design of implants or the development of musculoskeletal models. However, functional unguided joint motions are, by definition, affected by the activity of muscles. Previously published data has disagreed on the relative position and orientation of the two primary axes of rotation of the wrist, i.e. the radioulnar deviation (RUD) axes with respect to the flexion-extension (FE) axis. An in vivo study comparing the FE and RUD IHAs and SDAs of guided motions, to replicate in vitro conditions, and unguided motions of 23 healthy participants was conducted using optical motion capture. Guided motions were performed with the hand and forearm flush against a flat surface. The relative position and orientation of the RUD SDAs with respect to the FE SDAs differed (p = 0.019, p = 0.001) between unguided FE and guided RUD (0.1 ± 4.3 mm, 93.5 ±16.0°) and guided FE and RUD (1.6 ± 4.0 mm, 107.8 ±17.7°). This indicates that the use of different constraints, and not physiological differences, is the cause for differences in the relative positions and orientations of the FE and RUD axes in the literature. Thus, the practice of using in vitro definitions of the axes of rotation of the wrist for in vivo applications, especially involving FE, may be inappropriate and care must be taken to account for any constraint on wrist motion. It is recommended that investigators define the axes of rotation specifically for their study or refer to literature featuring the desired levels of constraint.
Akinnola OO, Vardakastani V, Kedgley AE, 2020, Identifying tasks to elicit maximum voluntary contraction in the muscles of the forearm, Journal of Electromyography and Kinesiology, Vol: 55, Pages: 1-4, ISSN: 1050-6411
Maximum voluntary contractions (MVCs) are often used for the normalisation of electromyography data to enable comparison of signal patterns within and between study participants. Recommendations regarding the types of tasks that are needed to collect MVCs for the muscles of the forearm have been made, specifically advocating the use of resisted moment tasks to get better estimates of forearm MVCs. However, a protocol detailing which specific tasks to employ has yet to be published. Furthermore, the effects of limb dominance on the collection of MVCs have not been considered previously. Muscle activity was monitored while 23 participants performed nine isometric, resisted tasks. The tasks that are likely to elicit MVC in the flexor carpi ulnaris, flexor carpi radialis, flexor digitorum superficialis, extensor carpi ulnaris, extensor carpi radialis, extensor digitorum communis, and pronator teres were identified. Thus, targeted protocols can be designed to mitigate against fatigue. Hand dominance had limited effect, with differences being found only in the finger flexors and extensors (p< 0.03). Thus, use of the contralateral flexor digitorum superficialis and extensor digitorum communis muscles to obtain baselines for activation levels and patterns may not be appropriate.
Rusli W, Kedgley A, 2020, Statistical shape modelling of the first carpometacarpal joint reveals high variation in morphology, Biomechanics and Modeling in Mechanobiology, Vol: 19, Pages: 1203-1210, ISSN: 1617-7940
The first carpometacarpal (CMC) joint, located at the base of the thumb and formed by the junction between the first metacarpal and trapezium, is a common site for osteoarthritis of the hand. The shape of both the first metacarpal and trapezium contributes to the intrinsic bony stability of the jointandvariability in the morphology of both these bones can affect the joint’s function. The objectivesof this study wereto quantify the morphological variation of the complete metacarpal and trapeziumand determine anycorrelation between anatomical features ofthese two components of the first CMC joint. A multi-object statistical shape modelling pipeline, consisting of scaling, hierarchical rigid registration, non-rigid registration and projection pursuit principal component analysis, was implemented. Four anatomical measureswere quantified from the shape model, namely the first metacarpal articular tilt and torsion angles and the trapeziumlength and width.Variationsin the first metacarpal articulartilt angle (-6.3°<θ<12.3°) and trapezium width (10.28mm <𝓌<11.13mm)wereidentified in the firstprincipal component. In the second principal component, variationsin the first metacarpal14torsion angle (0.2°<α<14.2°), first metacarpal articular tilt angle (1.0°<θ<6.4°) and trapezium length (12.25mm <ℓ<17.33mm)weredetermined. Due to their implications for joint stability, the first metacarpal articular tilt angle and trapezium width maybe important anatomical features which couldbe used toadvance early detectionand treatment offirst CMC joint osteoarthritis.
Shaerf DA, Chae WJ, Sharif-Razavian R, et al., 2020, Do "Anatomic" Distal Ulna Plating Systems Fit the Distal Ulna Without Causing Soft Tissue Impingement?, Hand (N Y), Pages: 1558944720930302-1558944720930302
Background: Distal ulna fracture fixation plates commonly cause irritation, necessitating removal, due to the narrow area between the ulna articular cartilage and the extensor carpi ulnaris. This study defines the safe zone for plate application and determines whether wrist position affects risk of impingement. Methods: Four different distal ulna anatomic plates (Acumed, Medartis, Skeletal Dynamics, and Synthes) were applied to 12 cadaveric specimens. Safe zone size was measured in circumferential distance and angular arc. Impingement was examined in flexion and extension in neutral, pronation, and supination. Results: The distal ulna safe zone has dimensions of a 92° arc and perimeter circumference of 15 mm. Cumulative extensor carpi ulnaris (ECU) impingement occurred in 0% of the 6 simulated wrist/forearm positions for the Acumed plate, 22% for the Synthes plate, 31% for the Skeletal Dynamics plate, and 68% for the Medartis plate. Impingement was most common in supination. Likelihood of ECU impingement significantly decreased in the following order; Medartis > Skeletal Dynamics > Synthes > Acumed. Conclusion: The ECU tendon's mobility can cause impingement on ulnarly placed distal ulna plates. Intra-operative testing should be performed in supination. Take home points regarding each plate from the 4 different manufacturers: contouring of Medartis plates, when placed ulnarly, is mandatory. The Acumed plate impinged the least but is not designed for far-distal fractures. The Synthes plate is least bulky but not suitable for proximal fractures. The Skeletal Dynamics plate appeared the most versatile with a reduced incidence of impingement compared to other ulnarly based plates.
Shah D, Horwitz M, Kedgley A, 2020, Extensor retinaculum excision does not affect wrist tendon forces: a cadaveric simulator study, Journal of Hand Surgery (European Volume), ISSN: 0266-7681
The extensor retinaculum is often compromised during trauma or elective wrist surgery and can be used as an autograft in reconstructive procedures of the digits. The aim of this study was to observe alterations in wrist muscle forces following retinaculum resection and surgical repair. A validated physiological wrist simulator was used to replicate cyclic wrist motions in nine cadaveric specimens by applying tensile loads to six wrist tendons. No differences were observed in mean and peak muscle forces following retinaculum resection and reconstruction. Post-surgical force reduction of extensor carpi radialis brevis in extension and ulnar deviation was suggestive of tendon bowstringing. However, bowstringing did not result in clinically relevant alterations to the distribution of muscle forces in the wrist.
Shah D, Middleton C, Gurdezi S, et al., 2020, The effect of surgical treatments for trapeziometacarpal osteoarthritis on wrist biomechanics: a cadaver study, Journal of Hand Surgery (American Volume), Vol: 45, Pages: 389-398, ISSN: 0363-5023
Purpose: Studies have shown the effects of surgical treatments for trapeziometacarpal osteoarthritis on thumb biomechanics; however, the biomechanical effects on the wrist have not been reported. This study aimed to quantifyalterations in wrist muscle forces following trapeziectomy with or withoutligament reconstruction and replacement. Methods: A validated physiological wrist simulator replicatedcyclic wrist motions in cadaveric specimens by applying tensile loads to six muscles. Muscle forces required to move the intact wrist were compared to those required after performing trapeziectomy, suture suspension arthroplasty, prosthetic replacement and ligament reconstruction with tendon interposition (LRTI). Results: Trapeziectomy requiredhigher abductor pollicis longusforcesinflexion, and higher flex or carpi radialis forces coupled with lower extensor carpi ulnaris forces in radial deviation. Of the three surgical reconstructions tested post-trapeziectomy, wrist muscle forces following LRTI were closest to those observed in the intact case, throughout the range of all simulated motions. Conclusions: This study shows that wrist biomechanics weresignificantly altered following trapeziectomy, and of the reconstructions tested, LRTI most closely resembled the intact biomechanics in this cadaveric model.
Nolte D, Ko S-T, Bull AMJ, et al., 2020, Reconstruction of the lower limb bones from digitised anatomical landmarks using statistical shape modelling, Gait & Posture, Vol: 77, Pages: 269-275, ISSN: 0966-6362
BackgroundBone shapes strongly influence force and moment predictions of kinematic and musculoskeletal models used in motion analysis. The precise determination of joint reference frames is essential for accurate predictions. Since clinical motion analysis typically does not include medical imaging, from which bone shapes may be obtained, scaling methods using reference subjects to create subject-specific bone geometries are widely used.Research questionThis study investigated if lower limb bone shape predictions from skin-based measurements, utilising an underlying statistical shape model (SSM) that corrects for soft tissue artefacts in digitisation, can be used to improve conventional linear scaling methods of bone geometries.MethodsSSMs created from 35 healthy adult femurs and tibiae/fibulae were used to reconstruct bone shapes by minimising the distance between anatomical landmarks on the models and those digitised in the motion laboratory or on medical images. Soft tissue artefacts were quantified from magnetic resonance images and then used to predict distances between landmarks digitised on the skin surface and bone. Reconstruction results were compared to linearly scaled models by measuring root mean squared distances to segmented surfaces, calculating differences of commonly used anatomical measures and the errors in the prediction of the hip joint centre.ResultsSSM reconstructed surface predictions from varying landmark sets from skin and bone landmarks were more accurate compared to linear scaling methods (2.60–2.95 mm vs. 3.66–3.87 mm median error; p < 0.05). No significant differences were found between SSM reconstructions from bony landmarks and SSM reconstructions from digitised landmarks obtained in the motion lab and therefore reconstructions using skin landmarks are as accurate as reconstructions from landmarks obtained from medical images.SignificanceThese results indicate that SSM reconstructions can be used to increase the accurac
Jones D, Wang L, Ghanbari A, et al., 2020, Design and evaluation of magnetic hall effect tactile sensors for use in sensorized splints, Sensors, Vol: 20, Pages: 1-13, ISSN: 1424-8220
Splinting techniques are widely used in medicine to inhibit the movement of arthritic joints. Studies into the effectiveness of splinting as a method of pain reduction have generally yielded positive results, however, no significant difference has been found in clinical outcomes between splinting types. Tactile sensing has shown great promise for the integration into splinting devices and may offer further information into applied forces to find the most effective methods of splinting. Hall effect-based tactile sensors are of particular interest in this application owing to their low-cost, small size, and high robustness. One complexity of the sensors is the relationship between the elastomer geometry and the measurement range. This paper investigates the design parameters of Hall effect tactile sensors for use in hand splinting. Finite element simulations are used to locate the areas in which sensitivity is high in order to optimise the deflection range of the sensor. Further simulations then investigate the mechanical response and force ranges of the elastomer layer under loading which are validated with experimental data. A 4 mm radius, 3 mm-thick sensor is identified as meeting defined sensing requirements for range and sensitivity. A prototype sensor is produced which exhibits a pressure range of 45 kPa normal and 6 kPa shear. A proof of principle prototype demonstrates how this can be integrated to form an instrumented splint with multi-axis sensing capability and has the potential to inform clinical practice for improved splinting.
Ding Z, Tsang C, Nolte D, et al., 2019, Improving musculoskeletal model scaling using an anatomical atlas: the importance of gender and anthropometric similarity to quantify joint reaction forces, IEEE Transactions on Biomedical Engineering, Vol: 66, Pages: 3444-3456, ISSN: 0018-9294
Objective: The accuracy of a musculoskeletal model relies heavily on the implementation of the underlying anatomical dataset. Linear scaling of a generic model, despite being time and cost-efficient, produces substantial errors as it does not account for gender differences and inter-individual anatomical variations. The hypothesis of this study is that linear scaling to a musculoskeletal model with gender and anthropometric similarity to the individual subject produces similar results to the ones that can be obtained from a subject-specific model. Methods: A lower limb musculoskeletal anatomical atlas was developed consisting of ten datasets derived from magnetic resonance imaging of healthy subjects and an additional generic dataset from the literature. Predicted muscle activation and joint reaction force were compared with electromyography and literature data. Regressions based on gender and anthropometry were used to identify the use of atlas. Results: Primary predictors of differences for the joint reaction force predictions were mass difference for the ankle (p<0.001) and length difference for the knee and hip (p≤0.017) . Gender difference accounted for an additional 3% of the variance (p≤0.039) . Joint reaction force differences at the ankle, knee and hip were reduced by between 50% and 67% (p=0.005) when using a musculoskeletal model with the same gender and similar anthropometry in comparison with a generic model. Conclusion: Linear scaling with gender and anthropometric similarity can improve joint reaction force predictions in comparison with a scaled generic model. Significance: The scaling approach and atlas presented can improve the fidelity and utility of musculoskeletal models for subject-specific applications.
Carpanen D, Kedgley A, Shah D, et al., 2019, Injury risk of interphalangeal and metacarpophalangeal joints under impact loading, Journal of the Mechanical Behavior of Biomedical Materials, Vol: 97, Pages: 306-311, ISSN: 1751-6161
Injuries to the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints of the hand are particularly disabling. However, current standards for hand protection from blunt impact are not based on quantitative measures of the likelihood of damage to the tissues. The aim of this study was to evaluate the probability of injury of the MCP and PIP joints of the human hand due to blunt impact.Impact testing was conducted on 21 fresh-frozen cadaveric hands. Unconstrained motion at every joint was allowed. All hands were imaged with computed tomography and dissected post-impact to quantify injury. An injury-risk curve was developed for each joint using a Weibull distribution with dorsal impact force as the predictive variable.The injury risks for PIP joints were similar, as were those for MCP joints. The risk of injury of the MCP joints from a given applied force was significantly greater than that of the PIP joints (p = 0.0006). The axial forces with a 50% injury risk for the MCP and PIP joints were 3.0 and 4.2 kN, respectively.This is the first study to have investigated the injury tolerance of the MCP and PIP joints. The proposed injury curves can be used for assessing the likelihood of tissue damage, for designing targeted protective solutions such as gloves, and for developing more biofidelic standards for assessing these solutions.
Kedgley AE, Saw TH, Segal NA, et al., 2019, Predicting meniscal tear stability across knee-joint flexion using finite-element analysis, Knee Surgery, Sports Traumatology, Arthroscopy, Vol: 27, Pages: 206-214, ISSN: 0942-2056
Purpose: To analyse the stress distribution through longitudinal and radial meniscal tears in three tear locations in weight-bearing conditions and use it to ascertain the impact of tear location and type on the potential for healing of meniscal tears. Methods: Subject-specific finite-element models of a healthy knee under static loading at 0°, 20°, and 30° knee flexion were developed from unloaded magnetic resonance images and weight-bearing, contrast-enhanced computed tomography images. Simulations were then run after introducing tears into the anterior, posterior, and midsections of the menisci. Results: Absolute differences between the displacements of anterior and posterior segments modelled in the intact state and those quantified from in vivo weight-bearing images were less than 0.5 mm. There were tear-location-dependent differences between hoop stress distributions along the inner and outer surfaces of longitudinal tears; the longitudinal tear surfaces were compressed together to the greatest degree in the lateral meniscus and were most consistently in compression on the midsections of both menisci. Radial tears resulted in an increase in stress at the tear apex and in a consistent small compression of the tear surfaces throughout the flexion range when in the posterior segment of the lateral meniscus. Conclusions: Both the type of meniscal tear and its location within the meniscus influenced the stresses on the tear surfaces under weight bearing. Results agree with clinical observations and suggest reasons for the inverse correlation between longitudinal tear length and healing, the inferior healing ability of medial compared with lateral menisci, and the superior healing ability of radial tears in the posterior segment of the lateral meniscus compared with other radial tears. This study has shown that meniscal tear location in addition to type likely plays a crucial role in dictating the success of non-operative treatment of the menisci. T
Shah D, Middleton C, Gurdezi S, et al., 2018, Alterations to wrist tendon forces following flexor carpi radialis or ulnaris sacrifice: a cadaveric simulator study, Journal of Hand Surgery (European Volume), Vol: 43, Pages: 886-888, ISSN: 1753-1934
Tenotomies, tendon transfers or nerve injuries can result in partial or complete loss of the flexor carpi radialis (FCR) or flexor carpi ulnaris (FCU) function. The aim of this study was to observe alterations in the distribution of muscle forces at the wrist due to the absence of each of these flexors. Cyclic planar and complex wrist motions were actively simulated in cadaveric specimens by applying tensile loads to six muscle tendons using a validated physiological wrist simulator. The absence of FCR or FCU resulted in higher forces in synergists, coupled with lower forces in antagonists, and an overall decrease in the total force of all tendons. Thus, alterations in wrist tendon forces following reconstructive procedures utilising a tendon may have clinical implications, such as muscle fatigue or reduced strength.
Vardakastani V, Bell H, Mee S, et al., 2018, Clinical measurement of dart throwing motion of the wrist: variability, accuracy and correction, Journal of Hand Surgery (European Volume), Vol: 43, Pages: 723-731, ISSN: 1753-1934
Despite being functionally important, dart throwing motion is difficult to assess accurately through goniometry. The objectives of this study were to describe a method for reliably quantifying the dart throwing motion using goniometric measurements within a healthy population. Wrist kinematics of 24 healthy participants were assessed using goniometry and optical motion tracking. Three wrist angles were measured at the starting and ending points of the motion: flexion-extension, radial-ulnar deviation and dart throwing motion angle. The orientation of the dart throwing motionplane relative to the flexion-extension axis ranged between 28° and 57° among the tested population. Plane orientations derived from optical motion capture differed from those calculated through goniometry by 25°. An equation to correct the estimation of the plane from goniometry measurements was derived. This was applied and differences in the orientation of the plane were reduced to non-significant levels, enabling dart throwing motion to be measured using goniometry alone.
Shah D, Middleton C, Gurdezi S, et al., 2018, The importance of abductor pollicis longus in wrist motions: a physiological wrist simulator study, Journal of Biomechanics, Vol: 77, Pages: 218-222, ISSN: 0021-9290
The abductor pollicis longus (APL) is one of the primary radial deviators of the wrist, owing to its insertion at the base of the first metacarpal and its large moment arm about the radioulnar deviation axis. Although it plays a vital role in surgical reconstructions of the wrist and hand, it is often neglected while simulating wrist motions in vitro. The aim of this study was to observe the effects of the absence of APL on the distribution of muscle forces during wrist motions. A validated physiological wrist simulator was used to replicate cyclic planar and complex wrist motions in cadaveric specimens by applying tensile loads to six wrist muscles – flexor carpi radialis (FCR), flexor carpi ulnaris, extensor carpi radialis longus (ECRL), extensor carpi radialis brevis, extensor carpi ulnaris (ECU) and APL. Resultant muscle forces for active wrist motions with and without actuating the APL were compared. The absence of APL resulted in higher forces in FCR and ECRL – the synergists of APL – and lower forces in ECU – the antagonist of APL. The altered distribution of wrist muscle forces observed in the absence of active APL control could significantly alter the efficacy of in vitro experiments conducted on wrist simulators, in particular when investigating those surgical reconstructions or rehabilitation of the wrist heavily reliant on the APL, such as treatments for basal thumb osteoarthritis.
Taylor SAF, Kedgley AE, Humphries A, et al., 2018, Simulated activities of daily living do not replicate functional upper limb movement or reduce movement variability, Journal of Biomechanics, Vol: 76, Pages: 119-128, ISSN: 0021-9290
Kinematic assessments of the upper limb during activities of daily living (ADLs) are used as an objective measure of upper limb function. The implementation of ADLs varies between studies; whilst some make use of props and define a functional target, others use simplified tasks to simulate the movements in ADLs. Simulated tasks have been used as an attempt to reduce the large movement variability associated with the upper limb. However, it is not known whether simulated tasks replicate the movements required to complete ADLs or reduce movement variability. The aim of this study is to evaluate the use of simulated tasks in upper limb assessments in comparison to functional movements. Therefore answering the following questions: Do simulated tasks replicate the movements required of the upper limb to perform functional activities? Do simulated tasks reduce intra- and inter-subject movement variability? Fourteen participants were asked to perform five functional tasks (eat, wash, retrieve from shelf, comb and perineal care) using two approaches: a functional and a simulated approach. Joint rotations were measured using an optoelectronic system. Differences in movement and movement variability between functional and simulated tasks were evaluated for the thorax, shoulder, elbow/forearm and wrist rotations. Simulated tasks did not accurately replicate the movements required for ADLs and there were minimal differences in movement variability between the two approaches. The study recommends the use of functional tasks with props for future assessments of the upper limb.
Edwards DS, Arshad MS, Luokkala T, et al., 2018, The contribution of the posterolateral capsule to elbow joint stability: a cadaveric biomechanical investigation., Journal of Shoulder and Elbow Surgery, Vol: 27, Pages: 1178-1184, ISSN: 1058-2746
BACKGROUND: Elbow posterolateral rotatory instability occurs after an injury to the lateral collateral ligament complex (LCLC) in isolation or in association with an osteochondral fracture of the posterolateral margin of the capitellum (Osborne-Cotterill lesion [OCL]). The contribution to elbow stability of the posterolateral capsule, attached to this lesion, is unknown. This study quantified the displacement of the radial head on simulated posterior draw with sectioning of the posterior capsule (a simulated OCL) or LCLC. METHODS: Biomechanical testing of the elbow was performed in 8 upper limb cadavers. With the elbow 0°, 30°, 60°, and 90° degrees of flexion, posterior displacement of the radius was measured at increments of a load of 5 N up to 50 N. A simulated OCL and LCLC injury was then performed. RESULTS: A simulated OCL results in significantly more displacement of the radial head compared with the intact elbow at 30° to 60° of elbow flexion. LCLC resection confers significantly more displacement. An OCL after LCLC resection does not create further displacement. CONCLUSIONS: The degree of radial head displacement is greater after a simulated OCL at 30° to 60° of flexion compared with the intact elbow with the same load but not as great as seen with sectioning of the LCLC. This study suggests that the posterior capsule attaching to the back of the capitellum is important to elbow stability and should be identified as the Osborne-Cotterill ligament. Clinical studies are required to determine the importance of these biomechanical findings.
Goislard de Monsabert B, Edwards T, Shah DS, et al., 2018, Importance of consistent datasets in musculoskeletal modelling: a study of the hand and wrist, Annals of Biomedical Engineering, Vol: 46, Pages: 71-85, ISSN: 0090-6964
Hand musculoskeletal models provide a valuable insight into the loads withstood by the upper limb; however, their development remains challenging because there are few datasets describing both the musculoskeletal geometry and muscle morphology from the elbow to the finger tips. Clinical imaging, optical motion capture and microscopy were used to create a dataset from a single specimen. Subsequently, a musculoskeletal model of the wrist was developed based on these data to estimate muscle tensions and to demonstrate the potential of the provided parameters. Tendon excursions and moment arms predicted by this model were in agreement with previously reported experimental data. When simulating a flexion-extension motion, muscle forces reached 90 N among extensors and a co-contraction of flexors, amounting to 62.6 N, was estimated by the model. Two alternative musculoskeletal models were also created based on anatomical data available in the literature to illustrate the effect of combining incomplete datasets. Compared to the initial model, the intensities and load sharing of the muscles estimated by the two alternative models differed by up to 180% for a single muscle. This confirms the importance of using a single source of anatomical data when developing such models.
Garland A, Shah D, Kedgley A, 2017, Wrist tendon moment arms: Quantification by imaging and experimental techniques, Journal of Biomechanics, Vol: 68, Pages: 136-140, ISSN: 0021-9290
Subject-specific musculoskeletal models require accurate values of muscle moment arms. The aim of this study was to compare moment arms of wrist tendons obtained from non-invasive magnetic resonance imaging (MRI) to those obtained from an in vitro experimental approach. MRI was performed on ten upper limb cadaveric specimens to obtain the centrelines for the flexor carpi radialis (FCR), flexor carpi ulnaris (FCU), extensor carpi radialis longus (ECRL), extensor carpi radialis brevis (ECRB), extensor carpi ulnaris (ECU), and abductor pollicis longus (APL) tendons. From these, the anatomical moment arms about each of the flexion-extension (FE) and radioulnar deviation (RUD) axes of the wrist were calculated. Specimens were mounted on a physiologic wrist simulator to obtain functional measurements of the moment arms using the tendon excursion method. No differences were observed between anatomical and functional values of the FE and RUD moment arms of FCR, ECRL and ECRB, and the RUD moment arm of ECU (p>0.075). Scaling the anatomical moment arms relative to ECRB in FE and ECU in RUD reduced differences in the FE moment arm of FCU and the RUD moment arm of APL to less than 15% (p>0.139). However, differences persisted in moment arms of FCU in RUD, and ECU and APL in FE (p<0.008). This study shows that while measurements of moment arms of wrist tendons using imaging do not always conform to values obtained using in vitro experimental approaches, a stricter protocol could result in the acquisition of subject-specific moment arms to personalise musculoskeletal models.
Shah DS, Middleton C, Gurdezi S, et al., 2017, The effects of wrist motion and hand orientation on muscle forces: a physiologic wrist simulator study, Journal of Biomechanics, Vol: 60, Pages: 232-237, ISSN: 1873-2380
Although the orientations of the hand and forearm vary for different wrist rehabilitation protocols, their effect on muscle forces has not been quantified. Physiologic simulators enable a biomechanical evaluation of the joint by recreating functional motions in cadaveric specimens. Control strategies used to actuate joints in 5 physiologic simulators usually employ position or force feedback alone to achieve optimum load distribution across the muscles. After successful tests on a phantom limb, unique combinations of position and force feedback – hybrid control and cascade control – were used to simulate multiple cyclic wrist motions of flexion-extension, radioulnar deviation, dart thrower’s motion, and 10 circumduction using six muscles in ten cadaveric specimens. Low kinematic errors and coefficients of variation of muscle forces were observed for planar and complex wrist motions using both novel control strategies. The effect of gravity was most pronounced when the hand was in the horizontal orientation, resulting in higher extensor forces (p<0.017) and higher out-of-plane kinematic errors (p<0.007), as compared to the vertically 15 upward or downward orientations. Muscle forces were also affected by the direction of rotation during circumduction. The peak force of flexor carpi radialis was higher in clockwise circumduction (p=0.017), while that of flexor carpi ulnaris was higher in anticlockwise circumduction (p=0.013). Thus, the physiologic wrist simulator accurately replicated cyclic planar and complex motions in cadaveric specimens. Moreover, the dependence of muscle 20 forces on the hand orientation and the direction of circumduction could be vital in the specification of such parameters during wrist rehabilitation.
Carpanen D, Kedgley AE, Plant D, et al., 2016, The risk of injury of the metacarpophalangeal and interphalangeal joints of the hand, International Research Council on the Biomechanics of Injury, Pages: 902-903
Nolte D, Tsang CK, Zhang KY, et al., 2016, Non-linear scaling of a musculoskeletal model of the lower limb using statistical shape models, Journal of Biomechanics, Vol: 49, Pages: 3576-3581, ISSN: 1873-2380
Accurate muscle geometry for musculoskeletal models is important to enable accurate subject-specific simulations. Commonly, linear scaling is used to obtain individualised muscle geometry. More advanced methods include non-linear scaling using segmented bone surfaces and manual or semi-automatic digitisation of muscle paths from medical images. In this study, a new scaling method combining non-linear scaling with reconstructions of bone surfaces using statistical shape modelling is presented. Statistical Shape Models (SSMs) of femur and tibia/fibula were used to reconstruct bone surfaces of nine subjects. Reference models were created by morphing manually digitised muscle paths to mean shapes of the SSMs using non-linear transformations and inter-subject variability was calculated. Subject-specific models of muscle attachment and via points were created from three reference models. The accuracy was evaluated by calculating the differences between the scaled and manually digitised models. The points defining the muscle paths showed large inter-subject variability at the thigh and shank – up to 26 mm; this was found to limit the accuracy of all studied scaling methods. Errors for the subject-specific muscle point reconstructions of the thigh could be decreased by 9% to 20% by using the non-linear scaling compared to a typical linear scaling method. We conclude that the proposed non-linear scaling method is more accurate than linear scaling methods. Thus, when combined with the ability to reconstruct bone surfaces from incomplete or scattered geometry data using statistical shape models our proposed method is an alternative to linear scaling methods.
Shah D, Kedgley AE, 2016, Control of a wrist joint motion simulator: a phantom study, Journal of Biomechanics, Vol: 49, Pages: 3061-3068, ISSN: 1873-2380
The presence of muscle redundancy and co-activation of agonist-antagonist pairs in vivo makes the optimization of the load distribution between muscles in physiologic joint simulators vital. This optimization is usually achieved by employing different control strategies based on position and/or force feedback. A muscle activated physiologic wrist simulator was developed to test and iteratively refine such control strategies on a functional replica of a human arm. Motions of the wrist were recreated by applying tensile loads using electromechanical actuators. Load cells were used to monitor the force applied by each muscle and an optical motion capture system was used to track joint angles of the wrist in real-time. Four control strategies were evaluated based on their kinematic error, repeatability and ability to vary co-contraction. With kinematic errors of less than 1.5°, the ability to vary co-contraction, and without the need for predefined antagonistic forces or muscle force ratios, novel control strategies – hybrid control and cascade control – were preferred over standard control strategies – position control and force control. Muscle forces obtained from hybrid and cascade control corresponded well with in vivo EMG data and muscle force data from other wrist simulators in the literature. The decoupling of the wrist axes combined with the robustness of the control strategies resulted in complex motions, like dart thrower’s motion and circumduction, being accurate and repeatable. Thus, two novel strategies with repeatable kinematics and physiologically relevant muscle forces are introduced for the control of joint simulators.
Amabile C, Bull A, Kedgley A, 2016, The centre of rotation of the shoulder complex and the effect of normalisation, Journal of Biomechanics, Vol: 49, Pages: 1938-1943, ISSN: 1873-2380
Shoulder motions consist of a composite movement of three joints and one pseudo-joint, which together dictate the humerothoracic motion. The purpose of this work was to quantify the location of the centre of rotation (CoR) of the shoulder complex as a whole. Dynamic motion of 12 participants was recorded using optical motion tracking during coronal, scapular and sagittal plane elevation. The instantaneous CoR was found for each angle of elevation using helical axes projected onto the three planes of motion. The location of an average CoR for each plane was evaluated using digitised and anthropometric measures for normalisation. When conducting motion in the coronal, scapular, and sagittal planes respectively, the coefficients for locating the CoRs of the shoulder complex are −61%, −61%, and −65% of the anterior-posterior dimension – the vector between the midpoint of the incisura jugularis and the xiphoid process and the midpoint of the seventh cervical vertebra and the eighth thoracic vertebra; 0%, −1%, and −2% of the superior-inferior dimension – the vector between the midpoint of the acromioclavicular joints and the midpoint of the anterior superior iliac spines; and 57%, 57%, and 78% of the medial-lateral dimension −0.129 times the height of the participant. Knowing the location of the CoR of the shoulder complex as a whole enables improved participant positioning for evaluation and rehabilitation activities that involve movement of the hand with a fixed radius, such as those that employ isokinetic dynamometers.
Ding Z, Nolte D, Tsang CK, et al., 2015, In Vivo Knee Contact Force Prediction Using Patient-Specific Musculoskeletal Geometry in a Segment-Based Computational Model., Journal of Biomechanical Engineering-Transactions of the ASME, Vol: 138, ISSN: 0148-0731
Segment-based musculoskeletal models allow the prediction of muscle, ligament and joint forces without making assumptions regarding joint degrees of freedom. The dataset published for the "Grand Challenge Competition to Predict In Vivo Knee Loads" provides directly-measured tibiofemoral contact forces for activities of daily living. For the "Sixth Grand Challenge Competition to Predict In Vivo Knee Loads", blinded results for "smooth" and "bouncy" gait trials were predicted using a customised patient-specific musculoskeletal model. For an unblinded comparison the following modifications were made to improve the predictions: • further customisations, including modifications to the knee centre of rotation; • reductions to the maximum allowable muscle forces to represent known loss of strength in knee arthroplasty patients; and • a kinematic constraint to the hip joint to address the sensitivity of the segment-based approach to motion tracking artefact. For validation, the improved model was applied to normal gait, squat and sit-to-stand for three subjects. Comparisons of the predictions with measured contact forces showed that segment-based musculoskeletal models using patient-specific input data can estimate tibiofemoral contact forces with root mean square errors (RMSEs) of 0.48-0.65 times body weight (BW) for normal gait trials. Tibiofemoral contact force patterns were estimated with an average coefficient of determination of 0.81 and with RMSEs of 0.46-1.01 times BW for squatting and 0.70-0.99 times BW for sit-to-stand tasks. This is comparable to the best validations in the literature using alternative models.
Kedgley AE, McWalter EJ, Wilson DR, 2015, The effect of coordinate system variation on in vivo patellofemoral kinematic measures, KNEE, Vol: 22, Pages: 88-94, ISSN: 0968-0160
Zhang KY, Kedgley AE, Donoghue CR, et al., 2014, The relationship between lateral meniscus shape and joint contact parameters in the knee: a study using data from the Osteoarthritis Initiative, ARTHRITIS RESEARCH & THERAPY, Vol: 16, ISSN: 1478-6354
Kedgley AE, Shore BJ, Athwal GS, et al., 2013, An in-vitro study of rotator cuff tear and repair kinematics using single- and double-row suture anchor fixation, INTERNATIONAL JOURNAL OF SHOULDER SURGERY, Vol: 7, Pages: 46-51, ISSN: 0973-6042
Kedgley AE, Fox A-MV, Jenkyn TR, 2012, Image intensifier distortion correction for fluoroscopic RSA: the need for independent accuracy assessment, JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS, Vol: 13, Pages: 197-204, ISSN: 1526-9914
Fluoroscopic images suffer from multiple modes of image distortion. Therefore, the purpose of this study was to compare the effects of correction using a range of two‐dimensional polynomials and a global approach. The primary measure of interest was the average error in the distances between four beads of an accuracy phantom, as measured using RSA. Secondary measures of interest were the root mean squared errors of the fit of the chosen polynomial to the grid of beads used for correction, and the errors in the corrected distances between the points of the grid in a second position. Based upon the two‐dimensional measures, a polynomial of order three in the axis of correction and two in the perpendicular axis was preferred. However, based upon the RSA reconstruction, a polynomial of order three in the axis of correction and one in the perpendicular axis was preferred. The use of a calibration frame for these three‐dimensional applications most likely tempers the effects of distortion. This study suggests that distortion correction should be validated for each of its applications with an independent “gold standard” phantom.
Fox A-MV, Kedgley AE, Lalone EA, et al., 2011, The effect of decreasing computed tomography dosage on radiostereometric analysis (RSA) accuracy at the glenohumeral joint, JOURNAL OF BIOMECHANICS, Vol: 44, Pages: 2847-2850, ISSN: 0021-9290
Lalone EA, Fox A-MV, Kedgley AE, et al., 2011, The effect of CT dose on glenohumeral joint congruency measurements using 3D reconstructed patient-specific bone models, PHYSICS IN MEDICINE AND BIOLOGY, Vol: 56, Pages: 6615-6624, ISSN: 0031-9155
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