54 results found
Jones D, Vardakastani V, Kedgley AE, et al., 2022, HAILO: a sensorised hand splint for the exploration of interaction forces., IEEE Transactions on Biomedical Engineering, Vol: PP, ISSN: 0018-9294
This study presents the design and development of an instrumented splint for measuring the biomechanical effects of hand splinting, and for assessing interface loading characteristics for people with arthritis. Sixteen multi-axial soft load-sensing nodes were mounted on the splint-skin interface of a custom 3D printed thumb splint. The splint was used to measure the interface forces between splint and hand in 12 healthy participants in 6 everyday tasks. Forces were compared between a baseline relaxed hand position and during states of active use. These data were used to generate a measure of sensor activity across the splint surface. Through direct comparison with a commercial splint, the 3D printed splint was deemed to provide similar levels of support. Observation of the activity across the 16 sensors showed that active areas of the splint surface varied between tasks but were commonly focused at the base of the thumb. Our findings show promise in the ability to detect the changing forces imparted on the hand by the splint surface, objectively characterising their behaviour. This opens the opportunity for future study into the biomechanical effects of splints on arthritic thumbs to improve this important intervention and improve quality of life.
Sharif Razavian R, Dreyfuss D, Katakura M, et al., 2022, An in vitro hand simulator for simultaneous control of hand and wrist movements, IEEE Transactions on Biomedical Engineering, Vol: 69, Pages: 975-982, ISSN: 0018-9294
A human hand is a complex biomechanical system, in which bones, ligaments, and musculotendon units dynamically interact to produce seemingly simple motions. A new physiological hand simulator has been developed, in which electromechanical actuators apply load to the tendons of extrinsic hand and wrist muscles to recreate movements in cadaveric specimens in a biofidelic way. This novel simulator simultaneously and independently controls the movements of the wrist (flexion/extension and radio-ulnar deviation) and flexion/extension of the fingers and thumb. Control of these four degrees of freedom (DOF) is made possible by actuating eleven extrinsic muscles of the hand. The coupled dynamics of the wrist, fingers, and thumb, and the over-actuated nature of the human musculoskeletal system make feedback control of hand movements challenging. Two control algorithms were developed and tested. The optimal controller relies on an optimization algorithm to calculate the required tendon tensions using the collective error in all DOFs, and the action-based controller loads the tendons solely based on their actions on the controlled DOFs (e.g., activating all flexors if a f lexing moment is required). Both controllers resulted in hand movements with small errors from the reference trajectories (< 3.4◦); however, the optimal controller achieved this with 16% lower total force. Owing to its simpler structure, the actionbased controller was extended to enable feedback control of grip force. This simulator has been shown to be a highly repeatable tool (< 0.25 N and < 0.2◦ variations in force and kinematics, respectively) for in vitro analyses of human hand biomechanics.
Vissers G, Rusli WMR, Scarborough A, et al., 2021, A study to compare strengths of cadaveric tendon repairs with round-bodied and cutting needles, Journal of Hand Surgery (European Volume), Vol: 47, ISSN: 0266-7681
This human cadaver study investigated whether flexor tendon repairs performed with round-bodied needleshad a higher risk of pull-out compared with those performed with cutting needles. Forty human cadavertendons were repaired (20 with each type of needle), subjected to tensile traction testing and evaluated byfailure load and mode of failure. The average failure load was 50 N (SD 13 N) for tendons repaired with roundbodied needles, compared with 49 N (SD 16 N) for tendons repaired with cutting needles. Round-bodiedneedles resulted in more suture pull-out (18 out of 20 tendons) than cutting needles (6 out of 20 tendons).We found no differences in failure load, but significant differences in the mode of failure between roundbodied and cutting needles when used for cadaveric flexor tendon repair.
Rusli WMR, Mirza E, Tolerton S, et al., 2021, Ligamentous constraint of the first carpometacarpal joint, JOURNAL OF BIOMECHANICS, Vol: 128, ISSN: 0021-9290
Yeh C, Calder J, Antflick J, et al., 2021, Maximum dorsiflexion increases Achilles tendon force during exercise for midportion Achilles tendinopathy, Scandinavian Journal of Medicine and Science in Sports, Vol: 31, Pages: 1674-1682, ISSN: 0905-7188
Rehabilitation is an important treatment for non-insertional Achilles tendinopathy. To date, eccentric loading exercises (ECC) have been the predominant choice; however, mechanical evidence underlying their use remains unclear. Other protocols, such as heavy slow resistance loading (HSR), have shown comparable outcomes, but with less training time. This study aims to identify the effect of external loading and other variables that influence Achilles tendon (AT) force in ECC and HSR. Ground reaction force and kinematic data during ECC and HSR were collected from 18 healthy participants for four loading conditions. The moment arms of the AT were estimated from MRIs of each participant. AT force then was calculated using the ankle torque obtained from inverse dynamics. In the eccentric phase, the AT force was not larger than in the concentric phase in both ECC and HSR. Under the same external load, the force through the AT was larger in ECC with the knee bent than in HSR with the knee straight due to increased dorsiflexion angle of the ankle. Multivariate regression analysis showed that external load and maximum dorsiflexion angle were significant predictors of peak AT force in both standing and seated positions. Therefore, to increase the effectiveness of loading the AT, exercises should apply adequate external load and reach maximum dorsiflexion during the movement. Peak dorsiflexion angle affected the AT force in a standing position at twice the rate of a seated position, suggesting standing could prove more effective for the same external loading and peak dorsiflexion angle.
Kelani T, Lee A, Walker M, et al., 2021, The influence of cervical spine angulation on symptoms associated with wearing a rigid neck collar, Geriatric Orthopaedic Surgery and Rehabilitation, Vol: 12, Pages: 1-7, ISSN: 2151-4585
Introduction:Rigid cervical spine collars can be used to maintain the position of the cervical spine following injury or surgery. However, they have been associated with difficulty swallowing, pressure sores and pain, particularly in older patients. We aimed to investigate the relationship between cervical spine angulation, a rigid neck collar and neck pain in healthy young and older adults.Methods:Twenty healthy young adults aged 25 ± 3 years and 17 healthy older adults aged 80 ± 8 years were tested. Magnetic resonance imaging scans of their cervical spines were taken before and after the rigid neck collar was worn for 1 hour. Measurement of vertebral angulation involved digitization of the scans and joint angle calculations using image processing software. Pain was quantified before and after the collar was worn, using a visual analogue scale.Results:Pain scores increased in the young group after the collar was worn (p = 0.001). The older group showed no difference in pain score after the collar was worn. Statistical tests showed no significant correlations between the change in cervical angles and the change in pain scores after the collar was worn.Discussion:The aging process may contribute to the changing distribution of subcutaneous tissue and increase risk of symptoms associated with wearing a collar. Oesophageal compression is not a result of collar use.Conclusion:There is no correlation between cervical spine vertebrae angulation and symptoms associated with wearing a neck collar. Generally, older individuals have greater cervical lordosis angles, and more straight and lordotic neck shapes. Older individuals may be more prone to skin-interface pressures from the neck collar than younger individuals.
Akinnola O, Vardakastani V, Kedgley A, 2021, Development of a clinically adoptable joint coordinate system for the wrist, Journal of Biomechanics, Vol: 118, ISSN: 0021-9290
Kinematics play a vital role in answering both clinical and research questions regarding joint biomechanics. Standardisation of kinematic approaches is important; however, the method that is currently recommended for building the joint coordinate system (JCS) to measure kinematics of the wrist is difficult to implement in vivo. In this study, a series of JCSs were examined and compared to the International Society of Biomechanics (ISB) recommendations in terms of landmark digitisation repeatability, coordinate frame creation repeatability, and secondary rotations during planar motion. No differences were found between the ISB JCS and 338 of 408 of the JCSs proposed in the study, meaning that the proposed alternative can be used without affecting the measured joint angles or repeatability of the JCS. Forearm frames that used a vector between the epicondyles to define the YZ plane of the forearm were found to create JCSs that produced secondary rotations greater than that which would be clinically detectable and thus, they should be avoided when defining a JCS. The remaining 338 coordinate systems can be used interchangeably; consequently, should there be any clinical limitations that result in missing landmarks, alternative coordinate systems can be used.A joint coordinate system created using the radial styloid, ulnar styloid, medial epicondyle, lateral epicondyle, the heads of the second and fifth metacarpal, and the base of the third metacarpal is recommended for quantifying kinematics in vivo.
Kedgley AE, Johnson GR, 2021, Biomechanics for joint replacement, Joint Replacement Technology, Pages: 1-28, ISBN: 9780128210826
The objective of this chapter is to provide the reader with an introduction to the basic principles of mechanics followed by an overview of results from the application of these principles to the major joints in the human body. The first section considers the concepts of kinematics, kinetics, and mechanical properties of materials. The latter section consists of biomechanical overviews of the joints and is divided into four subsections: the upper and lower limbs, temporomandibular joint and intervertebral joints. A detailed presentation of the major candidates for joint replacement - hip, knee, shoulder and elbow - is included. This introductory material will allow the fuller descriptions of each individual joint in the later chapters.
Akinnola O, Vardakastani V, Kedgley A, 2020, The effect of planar constraint on the definition of the wrist axes of rotation, Journal of Biomechanics, Vol: 113, 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.
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), Vol: 45, Pages: 986-988, 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.
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, Pages: 1-6, ISSN: 1558-9447
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, 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.
Rusli WMRB, Kedgley AE, 2019, Relationship between morphological variability of the human first metacarpal and trapezium quantified using statistical shape modelling, Anatomical Society Winter Meeting, Publisher: Wiley, Pages: 193-194, ISSN: 0021-8782
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: 0266-7681
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: 0021-9290
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.
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