Imperial College London

Dr Jonathan Jeffers

Faculty of EngineeringDepartment of Mechanical Engineering

Reader in Mechanical Engineering
 
 
 
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Contact

 

+44 (0)20 7594 5471j.jeffers

 
 
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Location

 

715City and Guilds BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

49 results found

Munford M, Ng KCG, Jeffers J, 2020, Mapping the Multi-Directional Mechanical Properties of Bone in the Proximal Tibia, Advanced Functional Materials, ISSN: 1616-301X

The remodeling behavior of bone is influenced by its mechanical environment. By mapping bone's mechanical properties in detail, orthopedic implants with respect to its mechanical properties could stimulate and harness remodeling to improve patient outcomes. In this study, multiaxial apparent modulus and strength of cadaveric proximal tibial bone are mapped and predicted from computed tomography (CT) derived apparent density. Group differences are identified from testing order, subchondral depth, condyle, and sub‐meniscal bone with covariates; age and gender. Axial modulus is 50% greater than the transverse modulus. Medial axial modulus is 30% greater than the lateral side. On the lateral side, axial modulus decreases by 50% from proximal to 25 mm distal. On the medial side, axial modulus remains relatively constant. Differences are quantified for density and multiaxial modulus across all subchondral depths, and different power law relationships are provided for each location. Density explains 75% of variation when grouped by subchondral depth and condyle. Yield strength is well‐predicted across all test directions, with density predicting 81% of axial strength variation and no differences over subchondral depth. Quantified mapping of bone multiaxial modulus based on condyle and subchondral depth is shown for the first time in a clinically viable protocol using conventional CT.

Journal article

Parkes M, Tallia F, Young G, Cann P, Jones J, Jeffers Jet al., 2020, Tribological evaluation of a novel hybrid for repair of articular cartilage defects, Materials Science and Engineering C: Materials for Biological Applications, ISSN: 0928-4931

The friction and wear properties of silica/poly(tetrahydrofuran)/poly(ε-caprolactone) (SiO2/PTHF/PCL-diCOOH) hybrid materials that are proposed as cartilage tissue engineering materials were investigated against living articular cartilage. A testing rig was designed to allow testing against fresh bovine cartilage. The friction force and wear were compared for five compositions of the hybrid biomaterial articulating against freshly harvested bovine cartilage in diluted bovine calf serum. Under a non-migrating contact, the friction force increased and hence shear force applied to the opposing articular cartilage also increased, resulting in minor damage to the cartilage surface. This worse case testing scenario was used to discriminate between material formulations and revealed the increase in friction and damaged area was lowest for the hybrid containing the most silica. Further friction and wear tests on one hybrid formulation with an elastic modulus closest to that of cartilage were then conducted in a custom incubator system. This demonstrated that over a five day period the friction force, cell viability and glucosaminoglycan (GAG) release into the lubricant were similar between a cartilage-cartilage interface and the hybrid-cartilage interface, supporting the use of these materials for cartilage repair. These results demonstrate how tribology testing can play a part in the development of new materials for chondral tissue engineering.

Journal article

Clark J, Heyraud A, Tavana S, Al-Jabri T, Tallia F, Clark B, Blunn G, Cobb J, Hansen U, Jones J, Jeffers Jet al., 2020, Exploratory full-field mechanical analysis across the osteochondral tissue– biomaterial interface in an ovine model, Materials, Vol: 13, ISSN: 1996-1944

Osteochondral injuries are increasingly prevalent, yet success in articular cartilage regeneration remains elusive, necessitating the development of new surgical interventions and novel medical devices. As part of device development, animal models are an important milestone in illustrating functionality of novel implants. Inspection of the tissue-biomaterial system is vital to understand and predict load-sharing capacity, fixation mechanics and micromotion, none of which are directly captured by traditional post-mortem techniques. This study aims to characterize the localised mechanics of an ex vivo ovine osteochondral tissue–biomaterial system extracted following six weeks in vivo testing, utilising laboratory micro-computed tomography, in situ loading and digital volume correlation. Herein, the full-field displacement and strain distributions were visualised across the interface of the system components, including newly formed tissue. The results from this exploratory study suggest that implant micromotion in respect to the surrounding tissue could be visualised in 3D across multiple loading steps. The methodology provides a non-destructive means to assess device performance holistically, informing device design to improve osteochondral regeneration strategies.

Journal article

Clark J, Tavana S, Heyraud A, Tallia F, Jones J, Hansen U, Jeffers Jet al., 2020, Quantifying 3D strain in scaffold implants for regenerative medicine, Materials, Vol: 13, ISSN: 1996-1944

Regenerative medicine solutions require thoughtful design to elicit the intended biological response. This includes the biomechanical stimulus to generate an appropriate strain in the scaffold and surrounding tissue to drive cell lineage to the desired tissue. To provide appropriate strain on a local level, new generations of scaffolds often involve anisotropic spatially graded mechanical properties that cannot be characterised with traditional materials testing equipment. Volumetric examination is possible with three-dimensional (3D) imaging, in situ loading and digital volume correlation (DVC). Micro-CT and DVC were utilised in this study on two sizes of 3D-printed inorganic/organic hybrid scaffolds (n = 2 and n = 4) with a repeating homogenous structure intended for cartilage regeneration. Deformation was observed with a spatial resolution of under 200 µm whilst maintaining displacement random errors of 0.97 µm, strain systematic errors of 0.17% and strain random errors of 0.031%. Digital image correlation (DIC) provided an analysis of the external surfaces whilst DVC enabled localised strain concentrations to be examined throughout the full 3D volume. Strain values derived using DVC correlated well against manually calculated ground-truth measurements (R2 = 0.98, n = 8). The technique ensures the full 3D micro-mechanical environment experienced by cells is intimately considered, enabling future studies to further examine scaffold designs for regenerative medicine.

Journal article

Ng KCG, Bankes M, El Daou H, Rodriguez y Baena F, Jeffers Jet al., 2020, Cam osteochondroplasty for femoroacetabular impingement increases microinstability in deep flexion: A cadaveric study, Arthroscopy: The Journal of Arthroscopy and Related Surgery, ISSN: 0749-8063

Purpose: The purpose of this in vitro cadaveric study was to examine the contributions of each surgical stage during cam femoroacetabular impingement (FAI) surgery (i.e., intact cam hip, T8 capsulotomy, cam resection, capsular repair) towards hip range of motion, translations, and microinstability.Methods: Twelve cadaveric cam hips were denuded to the capsule and mounted onto a robotic tester. Hips were positioned in several flexion positions: Full Extension, Neutral 0°, Flexion 30°, and Flexion 90°; and performed internal-external rotations to 5-Nm torque in each position. Hips underwent a series of surgical stages (T-capsulotomy, cam resection, capsular repair) and was retested after each stage. Changes in range of motion, translation, and microinstability (overall translation normalized by femoral head radius) were measured after each stage.Results: For range of motion, cam resection increased internal rotation at Flexion 90° (ΔIR = +6°, P = .001), but did not affect external rotation. Capsular repairs restrained external rotations compared to the cam resection stage (ΔER = –4 to –8°, P ≤ .04). For translations, the hip translated after cam resection at Flexion 90° in the medial-lateral plane (ΔT = +1.9 mm, P = .04), relative to the intact and capsulotomy stages. For microinstability, capsulotomy increased microinstability in Flexion 30° (ΔM = +0.05; P = .003), but did not further increase after cam resection. At Flexion 90°, microinstability did not increase after capsulotomy (ΔM = +0.03; P = .2, d = .24), but substantially increased after cam resection (ΔM = +0.08; P = .03), accounting for a 31% change with respect to the intact stage.Conclusions: Cam resection increased microinstability by 31% during deep hip flexion relative to the intact hip. This suggests that iatrogenic microinstability may be due to separation of the labral seal and resected contour of the femoral head.

Journal article

Doyle R, van Arkel RJ, Muirhead-Allwood S, Jeffers JRTet al., 2020, Impaction technique influences implant stability in low-density bone model, Bone & Joint Research, Vol: 9, Pages: 386-393

<jats:sec><jats:title>Aims</jats:title><jats:p> Cementless acetabular components rely on press-fit fixation for initial stability. In certain cases, initial stability is more difficult to obtain (such as during revision). No current study evaluates how a surgeon’s impaction technique (mallet mass, mallet velocity, and number of strikes) may affect component fixation. This study seeks to answer the following research questions: 1) how does impaction technique affect a) bone strain generation and deterioration (and hence implant stability) and b) seating in different density bones?; and 2) can an impaction technique be recommended to minimize risk of implant loosening while ensuring seating of the acetabular component? </jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p> A custom drop tower was used to simulate surgical strikes seating acetabular components into synthetic bone. Strike velocity and drop mass were varied. Synthetic bone strain was measured using strain gauges and stability was assessed via push-out tests. Polar gap was measured using optical trackers. </jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p> A phenomenon of strain deterioration was identified if an excessive number of strikes was used to seat a component. This effect was most pronounced in low-density bone at high strike velocities. Polar gap was reduced with increasing strike mass and velocity. </jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p> A high mallet mass with low strike velocity resulted in satisfactory implant stability and polar gap, while minimizing the risk of losing stability due to over-striking. Extreme caution not to over-strike must be exercised when using high velocity strikes in low-density bone for any mallet mass. Cite this article: Bone Joint Res 2020;9(7):386–393. <

Journal article

Ruiz de Galarreta S, Jeffers JRT, Ghouse S, 2020, A validated finite element analysis procedure for porous structures, MATERIALS & DESIGN, Vol: 189, ISSN: 0264-1275

Journal article

Munford M, Hossain U, Ghouse S, Jeffers JRTet al., 2020, Prediction of anisotropic mechanical properties for lattice structures, ADDITIVE MANUFACTURING, Vol: 32, ISSN: 2214-8604

Journal article

Clark JN, Garbout A, Ferreira SA, Javaheri B, Pitsillides AA, Rankin SM, Jeffers JRT, Hansen Uet al., 2020, Propagation phase-contrast micro-computed tomography allows laboratory-based three-dimensional imaging of articular cartilage down to the cellular level, OSTEOARTHRITIS AND CARTILAGE, Vol: 28, Pages: 102-111, ISSN: 1063-4584

Journal article

Ng KCG, Jeffers JRT, Beaule PE, 2019, Hip Joint Capsular Anatomy, Mechanics, and Surgical Management, JOURNAL OF BONE AND JOINT SURGERY-AMERICAN VOLUME, Vol: 101, Pages: 2141-2151, ISSN: 0021-9355

Journal article

Barnes SC, Clasper JC, Bull AMJ, Jeffers JRTet al., 2019, Micromotion and Push-Out Evaluation of an Additive Manufactured Implant for Above-the-Knee Amputees, JOURNAL OF ORTHOPAEDIC RESEARCH, Vol: 37, Pages: 2104-2111, ISSN: 0736-0266

Journal article

Doyle R, van Arkel RJ, Jeffers JRT, 2019, Effect of impaction energy on dynamic bone strains, fixation strength, and seating of cementless acetabular cups, JOURNAL OF ORTHOPAEDIC RESEARCH, Vol: 37, Pages: 2367-2375, ISSN: 0736-0266

Journal article

Ghouse S, Reznikov N, Boughton OR, Babu S, Ng KCG, Blunn G, Cobb JP, Stevens MM, Jeffers JRTet al., 2019, The design and in vivo testing of a locally stiffness-matched porous scaffold, APPLIED MATERIALS TODAY, Vol: 15, Pages: 377-388, ISSN: 2352-9407

Journal article

Logishetty K, van Arkel RJ, Ng KCG, Muirhead-Allwood SK, Cobb JP, Jeffers JRTet al., 2019, Hip capsule biomechanics after arthroplasty THE EFFECT OF IMPLANT, APPROACH, AND SURGICAL REPAIR, BONE & JOINT JOURNAL, Vol: 101B, Pages: 426-434, ISSN: 2049-4394

Journal article

Reznikov N, Boughton OR, Ghouse S, Weston AE, Collinson L, Blunn GW, Jeffers JRT, Cobb JP, Stevens MMet al., 2019, Individual response variations in scaffold-guided bone regeneration are determined by independent strain- and injury-induced mechanisms, BIOMATERIALS, Vol: 194, Pages: 183-194, ISSN: 0142-9612

Journal article

Ng KCG, Daou HE, Bankes MJK, Rodriguez y Baena F, Jeffers JRTet al., 2019, Hip Joint Torsional Loading Before and After Cam Femoroacetabular Impingement Surgery, AMERICAN JOURNAL OF SPORTS MEDICINE, Vol: 47, Pages: 420-430, ISSN: 0363-5465

Journal article

Doyle R, Boughton O, Plant D, Desoutter G, Cobb JP, Jeffers JRTet al., 2019, An in vitro model of impaction during hip arthroplasty, JOURNAL OF BIOMECHANICS, Vol: 82, Pages: 220-227, ISSN: 0021-9290

Journal article

El Daou H, Ng KCG, Van Arkel R, Jeffers JRT, Rodriguez y Baena Fet al., 2019, Robotic hip joint testing: Development and experimental protocols, MEDICAL ENGINEERING & PHYSICS, Vol: 63, Pages: 57-62, ISSN: 1350-4533

Journal article

Ghouse S, Babu S, Nai K, Hooper PA, Jeffers JRTet al., 2018, The influence of laser parameters, scanning strategies and material on the fatigue strength of a stochastic porous structure, ADDITIVE MANUFACTURING, Vol: 22, Pages: 290-301, ISSN: 2214-8604

Journal article

van Arkel RJ, Ng KCG, Muirhead-Allwood SK, Jeffers JRTet al., 2018, Capsular Ligament Function After Total Hip Arthroplasty, JOURNAL OF BONE AND JOINT SURGERY-AMERICAN VOLUME, Vol: 100, ISSN: 0021-9355

Journal article

van Arkel RJ, Ghouse S, Milner PE, Jeffers JRTet al., 2018, Additive manufactured push-fit implant fixation with screw-strength pull out, JOURNAL OF ORTHOPAEDIC RESEARCH, Vol: 36, Pages: 1508-1518, ISSN: 0736-0266

Journal article

Han S, Alexander JW, Thomas VS, Choi J, Harris JD, Doherty DB, Jeffers JRT, Noble PCet al., 2018, Does Capsular Laxity Lead to Microinstability of the Native Hip?, AMERICAN JOURNAL OF SPORTS MEDICINE, Vol: 46, Pages: 1315-1323, ISSN: 0363-5465

Journal article

Ng KCG, Lamontagne M, Jeffers JRT, Grammatopoulos G, Beaule PEet al., 2018, Anatomic Predictors of Sagittal Hip and Pelvic Motions in Patients With a Cam Deformity, AMERICAN JOURNAL OF SPORTS MEDICINE, Vol: 46, Pages: 1331-1342, ISSN: 0363-5465

Journal article

Milner PE, Parkes M, Puetzer JL, Chapman R, Stevens MM, Cann P, Jeffers JRTet al., 2018, A low friction, biphasic and boundary lubricating hydrogel for cartilage replacement, ACTA BIOMATERIALIA, Vol: 65, Pages: 102-111, ISSN: 1742-7061

Journal article

Geraldes DM, Hansen U, Jeffers J, Amis AAet al., 2017, Stability of small pegs for cementless implant fixation, JOURNAL OF ORTHOPAEDIC RESEARCH, Vol: 35, Pages: 2765-2772, ISSN: 0736-0266

Journal article

Parkes M, Sayer K, Goldhofer M, Cann P, Walter WL, Jeffers Jet al., 2017, Zirconia phase transformation in retrieved, wear simulated, and artificially aged ceramic femoral heads, JOURNAL OF ORTHOPAEDIC RESEARCH, Vol: 35, Pages: 2781-2789, ISSN: 0736-0266

Journal article

Ghouse S, Babu S, Van Arkel RJ, Nai K, Hooper PA, Jeffers JRTet al., 2017, The influence of laser parameters and scanning strategies on the mechanical properties of a stochastic porous material, MATERIALS & DESIGN, Vol: 131, Pages: 498-508, ISSN: 0264-1275

Journal article

Alidousti H, Giles JW, Emery RJH, Jeffers Jet al., 2017, Spatial mapping of humeral head bone density, JOURNAL OF SHOULDER AND ELBOW SURGERY, Vol: 26, Pages: 1653-1661, ISSN: 1058-2746

Journal article

Parkes M, Cann P, Jeffers J, 2017, Real-time observation of fluid flows in tissue during stress relaxation using Raman spectroscopy, JOURNAL OF BIOMECHANICS, Vol: 60, Pages: 261-265, ISSN: 0021-9290

Journal article

Sopher RS, Amis AA, Calder JD, Jeffers JRTet al., 2017, Total ankle replacement design and positioning affect implant-bone micromotion and bone strains, MEDICAL ENGINEERING & PHYSICS, Vol: 42, Pages: 80-90, ISSN: 1350-4533

Journal article

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