Imperial College London

Angela Kedgley

Faculty of EngineeringDepartment of Bioengineering

Reader in Orthopaedic Biomechanics



+44 (0)20 7594 0747a.kedgley Website




514BSir Michael Uren HubWhite City Campus





Publication Type

64 results found

Devanand DB, Kedgley A, 2023, Objective methods of monitoring usage of orthotic devices for the extremities: a systematic review, Sensors, Vol: 23, Pages: 1-26, ISSN: 1424-8220

Orthoses are commonly prescribed to relieve symptoms for musculoskeletal and neurological conditions; however, patients stop wearing orthoses as recommended for many reasons. When considering the effectiveness of orthoses, there needs to be an objective way to monitor whether participants wear the orthosis as instructed, because if this is not followed, the orthoses will not work as intended. This review aimed to identify, summarise, and compare objective methods used to measure compliance with orthoses applied to the extremities. Databases (Scopus, Web of Science, Embase, CINAHL, and MEDLINE) were searched for eligible studies. Twenty-three studies were accepted in the final review, including five studies that employed upper limb orthoses, two that employed hip orthoses, and fifteen that employed lower limb orthoses. To measure compliance objectively, studies utilised temperature sensors, pressure sensors, accelerometers, a step counter, or a combination of sensors. All sensor types have their own advantages and disadvantages and should be chosen based on study-specific parameters. Sensor-derived monitoring provides quantitative, objective data that are beneficial in both clinical and research settings. The ideal solution to monitoring compliance would consist of both objective and user-reported aspects that, in combination, would provide an all-encompassing picture of the orthotic treatment prescribed.

Journal article

McMenemy L, Mondini V, Roberts DC, Kedgley A, Clasper JC, Stapley SAet al., 2023, Pattern of upper limb amputation associated with lower limb amputation: the UK military experience from Iraq and Afghanistan, BMJ MILITARY HEALTH, Vol: 169, Pages: E20-E23, ISSN: 2633-3767

Journal article

Sehjal R, Rusli W, Kedgley A, Sagmeister M, Williamson M, Smith Aet al., 2023, Biomechanical comparison of 5 different fixation constructs in a trapeziometacarpal joint arthrodesis model, The Journal of Hand Surgery, ISSN: 0363-5023

Purpose:Trapeziometacarpal joint (TMC) arthrodesis has a high rate of nonunion. This biomechanical analysis sought to determine the stiffness of 5 fixation methods in a TMC joint arthrodesis model.Methods:Five fixation constructs were tested in a validated porcine model: crossed 1.1-mm K-wires, crossed 1.6-mm K-wires, crossed headless compression screws (HCSs), compression plating (CP), and locked compression plating (LCP). The cantilever bending stiffness was measured in abduction, adduction, flexion, and extension. Samples were loaded to failure in extension, and the mode of failure was examined.Results:The crossed HCSs performed consistently well in all tests. Loading to failure resulted in screw pullout. In abduction and adduction, HCS and 1.6-mm K-wires were significantly stiffer than the other constructs. The mean load to failure in extension was similar in the HCS, CP, and LCP groups (304 N/mm, 311 N/mm, and 293 N/mm, respectively). There were no differences between CP and LCP in any biomechanical tests, and the mode of failure was through plate bending. The crossed 1.1-mm K-wires performed poorly in all tests.Conclusions:Crossed HCS displayed the greatest overall stability. Standard plating in compression mode and LCP had a similar biomechanical performance.Clinical relevance:The ideal construct stiffness required for the successful union after TMC joint arthrodesis is unknown, but HCS has the best overall biomechanical performance and, therefore, might be considered the best choice for this clinical setting.

Journal article

Wai G, Rusli W, Ghouse S, Kieser DC, Kedgley A, Newell Net al., 2023, Statistical shape modelling of the thoracic spine for the development of pedicle screw insertion guides, Biomechanics and Modeling in Mechanobiology, Vol: 22, Pages: 123-132, ISSN: 1617-7940

Spinal fixation and fusion are surgical procedures undertaken to restore stability in the spine and restrict painful or degenerative motion. Malpositioning of pedicle screws during these procedures can result in major neurological and vascular damage. Patient-specific surgical guides offer clear benefits, reducing malposition rates by up to 25%. However, they suffer from long lead times and the manufacturing process is dependent on third-party specialists. The development of a standard set of surgical guides may eliminate the issues with the manufacturing process. To evaluate the feasibility of this option, a statistical shape model (SSM) was created and used to analyse the morphological variations of the T4–T6 vertebrae in a population of 90 specimens from the Visible Korean Human dataset (50 females and 40 males). The first three principal components, representing 39.7% of the variance within the population, were analysed. The model showed high variability in the transverse process (~ 4 mm) and spinous process (~ 4 mm) and relatively low variation (< 1 mm) in the vertebral lamina. For a Korean population, a standardised set of surgical guides would likely need to align with the lamina where the variance in the population is lower. It is recommended that this standard set of surgical guides should accommodate pedicle screw diameters of 3.5–6 mm and transverse pedicle screw angles of 3.5°–12.4°.

Journal article

Li LX, Kedgley AE, Horwitz MD, 2023, A review of the use of 3D printing technology in treatment of scaphoid fractures., The Journal of Hand Surgery, Vol: 28, Pages: 22-33, ISSN: 1793-6535

Background: Three-dimensional (3D) printing technology is increasingly commercially viable for pre-surgical planning, intraoperative templating, jig creation and customised implant manufacture. The challenging nature of scaphoid fracture and nonunion surgery make it an obvious target. The aim of this review is to determine the use of 3D printed technologies in the treatment of scaphoid fractures. Methods: This is a review of the Medline, Embase and Cochrane Library databases examining studies aimed at therapeutic use of 3D printing, also known as rapid prototyping or additive technology, in the treatment of scaphoid fractures. All studies published up to and including November 2020 were included in the search. Relevant data extracted included modality of use (as template/model/guide/prosthesis), operative time, accuracy of reduction, radiation exposure, follow-up duration, time to union, complications and study quality. Results: A total of 649 articles were identified, of which 12 met the full inclusion criteria. Analysis of the articles showed that 3D printing techniques can be utilised in myriad ways to aid planning and delivery of scaphoid surgery. Percutaneous guides for Kirschner-wire (K-wire) fixation of non-displaced fractures can be created; custom guides can be printed to aid reduction of displaced or non-united fractures; patient-specific total prostheses may recreate near-normal carpal biomechanics and a simple model may help graft harvesting and positioning. Conclusions: This review found that the use of 3D printed patient-specific models and templates in scaphoid surgery can improve accuracy and speed, and reduce radiation exposure. 3D printed prostheses may also restore near-normal carpal biomechanics without burning bridges for potential future procedures. Level of Evidence: Level III (Therapeutic).

Journal article

Katakura M, Kedgley AE, Shaw JW, Mattiussi AM, Kelly S, Clark R, Allen N, Calder JDFet al., 2023, Epidemiological characteristics of foot and ankle injuries in 2 professional ballet companies: A 3-season cohort study of 588 medical attention injuries and 255 time-loss injuries, Orthopaedic Journal of Sports Medicine, Vol: 11, Pages: 1-8, ISSN: 2325-9671

Background: The foot and ankle are often reported as the most common sites of injury in professional ballet dancers; however, epidemiological research focusing on foot and ankle injuries in isolation and investigating specific diagnoses is limited. Purpose: To investigate the incidence rate, severity, burden, and mechanisms of foot and ankle injuries that (1) required visiting a medical team (medical attention foot and ankle injuries; MA-FAIs) and (2) prevented a dancer from fully participating in all dance-related activities for at least 24 hours after the injury (time-loss foot and ankle injuries; TL-FAIs) in 2 professional ballet companies. Study Design: Descriptive epidemiological study. Methods: Foot and ankle injury data across 3 seasons (2016-2017 to 2018-2019) were extracted from the medical databases of 2 professional ballet companies. Injury-incidence rate (per dancer-season), severity, and burden were calculated and reported with reference to the mechanism of injury. Results: A total of 588 MA-FAIs and 255 TL-FAIs were observed across 455 dancer-seasons. The incidence rates of MA-FAIs and TL-FAIs were significantly higher in women (1.20 MA-FAIs and 0.55 TL-FAIs per dancer-season) than in men (0.83 MA-FAIs and 0.35 TL-FAIs per dancer-season) (MA-FAIs, P =.002; TL-FAIs, P =.008). The highest incidence rates for any specific injury pathology were ankle impingement syndrome and synovitis for MA-FAIs (women 0.27 and men 0.25 MA-FAIs per dancer-season) and ankle sprain for TL-FAIs (women 0.15 and men 0.08 TL-FAIs per dancer-season). Pointe work and jumping actions in women and jumping actions in men were the most common mechanisms of injury. The primary mechanism of injury of ankle sprains was jumping activities, but the primary mechanisms of ankle synovitis and impingement in women were related to dancing en pointe. Conclusion: The results of this study highlight the importance of further investigation of injury prevention strategies targeting pointe work and

Journal article

Gionfrida L, Rusli WMRB, Bharath A, Kedgley Aet al., 2022, Validation of two-dimensional video-based inference of finger kinematics with pose estimation, PLoS One, Vol: 17, ISSN: 1932-6203

Accurate capture finger of movements for biomechanical assessments has typically been achieved within laboratory environments through the use of physical markers attached to a participant’s hands. However, such requirements can narrow the broader adoption of movement tracking for kinematic assessment outside these laboratory settings, such as in the home. Thus, there is the need for markerless hand motion capture techniques that are easy to use and accurate enough to evaluate the complex movements of the human hand. Several recent studies have validated lower-limb kinematics obtained with a marker-free technique, OpenPose. This investigation examines the accuracy of OpenPose, when applied to images from single RGB cameras, against a ‘gold standard’ marker-based optical motion capture system that is commonly used for hand kinematics estimation. Participants completed four single-handed activities with right and left hands, including hand abduction and adduction, radial walking, metacarpophalangeal (MCP) joint flexion, and thumb opposition. The accuracy of finger kinematics was assessed using the root mean square error. Mean total active flexion was compared using the Bland–Altman approach, and the coefficient of determination of linear regression. Results showed good agreement for abduction and adduction and thumb opposition activities. Lower agreement between the two methods was observed for radial walking (mean difference between the methods of 5.03°) and MCP flexion (mean difference of 6.82°) activities, due to occlusion. This investigation demonstrated that OpenPose, applied to videos captured with monocular cameras, can be used for markerless motion capture for finger tracking with an error below 11° and on the order of that which is accepted clinically.

Journal article

Gionfrida L, Bharath A, Kedgley A, Rusli Wet al., 2022, Validation of two-dimensional video-based inference of finger kinematics with pose estimation., PLoS One, ISSN: 1932-6203

Journal article

Gionfrida L, Rusli W, Kedgley A, Bharath Aet al., 2022, A 3DCNN-LSTM multi-class temporal segmentation for hand gesture recognition, Electronics, Vol: 11, ISSN: 2079-9292

This paper introduces a multi-class hand gesture recognition model developed to identify a set of hand gesture sequences from two-dimensional RGB video recordings, using both the appearance and spatiotemporal parameters of consecutive frames. The classifier utilizes a convolutional-based network combined with a long-short-term memory unit. To leverage the need for a large-scale dataset, the model deploys training on a public dataset, adopting a technique known as transfer learning to fine-tune the architecture on the hand gestures of relevance. Validation curves performed over a batch size of 64 indicate an accuracy of 93.95% (±0.37) with a mean Jaccard index of 0.812 (±0.105) for 22 participants. The fine-tuned architecture illustrates the possibility of refining a model with a small set of data (113,410 fully labelled image frames) to cover previously unknown hand gestures. The main contribution of this work includes a custom hand gesture recognition network driven by monocular RGB video sequences that outperform previous temporal segmentation models, embracing a small-sized architecture that facilitates wide adoption.

Journal article

Gionfrida L, Rusli WMR, Kedgley AE, Bharath Aet al., 2022, A 3DCNN-LSTM Multi-Class Temporal Segmentation for Hand Gesture Recognition, Electronics, Vol: 11, Pages: 2427-2427

<jats:p>This paper introduces a multi-class hand gesture recognition model developed to identify a set of hand gesture sequences from two-dimensional RGB video recordings, using both the appearance and spatiotemporal parameters of consecutive frames. The classifier utilizes a convolutional-based network combined with a long-short-term memory unit. To leverage the need for a large-scale dataset, the model deploys training on a public dataset, adopting a technique known as transfer learning to fine-tune the architecture on the hand gestures of relevance. Validation curves performed over a batch size of 64 indicate an accuracy of 93.95% (±0.37) with a mean Jaccard index of 0.812 (±0.105) for 22 participants. The fine-tuned architecture illustrates the possibility of refining a model with a small set of data (113,410 fully labelled image frames) to cover previously unknown hand gestures. The main contribution of this work includes a custom hand gesture recognition network driven by monocular RGB video sequences that outperform previous temporal segmentation models, embracing a small-sized architecture that facilitates wide adoption.</jats:p>

Journal article

Jones D, Vardakastani V, Kedgley AE, Gardiner MD, Vincent TL, Culmer P, Alazmani Aet 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.

Journal article

Sharif Razavian R, Dreyfuss D, Katakura M, Horwitz M, Kedgley Aet 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.

Journal article

Vissers G, Rusli WMR, Scarborough A, Horwitz MD, McArthur GJ, Kedgley AEet 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.

Journal article

Rusli WMR, Mirza E, Tolerton S, Yong S, Johnson R, Horwitz MD, Kedgley AEet al., 2021, Ligamentous constraint of the first carpometacarpal joint, Journal of Biomechanics, Vol: 128, Pages: 1-6, ISSN: 0021-9290

To examine the role of the ligaments in maintaining stability of the first carpometacarpal (CMC) joint, a sequential ligament sectioning study of sixteen specimens was performed. While a small compressive force was maintained, loads were applied to displace each specimen in four directions – volar, dorsal, radial, and ulnar. Translations of the specimen in both dorsal-volar and radial-ulnar axes were measured. Initially, the tests were conducted with the specimen intact. These tests were then repeated following sectioning of the CMC anterior oblique ligament (AOL), ulnar collateral ligament (UCL), intermetacarpal ligament (IML) and dorsal radial ligament (DRL). The first CMC joint translation was increased in the absence of IML and DRL (p < 0.05). Both IML and DRL were important in constraining the first CMC joint translation against external applied loads. Potential applications of these findings include the treatment of joint hypermobility and the reduction or delay of onset or progression of first CMC joint osteoarthritis.

Journal article

Yeh C, Calder J, Antflick J, Bull A, Kedgley Aet 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.

Journal article

Kelani T, Lee A, Walker M, Koizia L, Dani M, Fertleman M, Kedgley Aet 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.

Journal article

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.

Journal article

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.

Book chapter

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.

Journal article

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.

Journal article

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.

Journal article

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.

Journal article

Shaerf DA, Chae WJ, Sharif-Razavian R, Vardakastani V, Kedgley AE, Horwitz MDet al., 2020, Do "anatomic" distal ulna plating systems fit the distal ulna without causing soft tissue impingement?, Hand, Vol: 17, Pages: 506-511, 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.

Journal article

Shah D, Middleton C, Gurdezi S, Horwitz M, Kedgley Aet 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.

Journal article

Nolte D, Ko S-T, Bull AMJ, Kedgley AEet 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

Journal article

Jones D, Wang L, Ghanbari A, Vardakastani V, Kedgley AE, Gardiner MD, Vincent TL, Culmer PR, Alazmani Aet 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.

Journal article

Ding Z, Tsang C, Nolte D, Kedgley A, Bull Aet 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.

Journal article

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

Conference paper

Carpanen D, Kedgley A, Shah D, Edwards D, Plant D, Masouros Set 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.

Journal article

Kedgley AE, Saw TH, Segal NA, Hansen UN, Bull AMJ, Masouros SDet 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

Journal article

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