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

42 results found

Munford M, Hossain U, Ghouse S, Jeffers Jet al., 2020, Prediction of Anisotropic Mechanical Properties for Lattice Structures, Additive Manufacturing, ISSN: 2214-8604

Journal article

Clark J, Garbout A, Rodrigues Mendes Ferreira S, Javaheri B, Pitsillides A, Rankin S, Jeffers J, 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

ObjectiveHigh-resolution non-invasive three-dimensional (3D) imaging of chondrocytes in articular cartilage remains elusive. The aim of this study was to explore whether laboratory micro-computed tomography (micro-CT) permits imaging cells within articular cartilage.DesignBovine osteochondral plugs were prepared four ways: in phosphate-buffered saline (PBS) or 70% ethanol (EtOH), both with or without phosphotungstic acid (PTA) staining. Specimens were imaged with micro-CT following two protocols: 1) absorption contrast (AC) imaging 2) propagation phase-contrast (PPC) imaging. All samples were scanned in liquid. The contrast to noise ratio (C/N) of cellular features quantified scan quality and were statistically analysed. Cellular features resolved by micro-CT were validated by standard histology.ResultsThe highest quality images were obtained using propagation phase-contrast imaging and PTA-staining in 70% EtOH. Cellular features were also visualised when stained in PBS and unstained in EtOH. Under all conditions PPC resulted in greater contrast than AC (p < 0.0001 to p = 0.038). Simultaneous imaging of cartilage and subchondral bone did not impede image quality. Corresponding features were located in both histology and micro-CT and followed the same distribution with similar density and roundness values.ConclusionsThree-dimensional visualisation and quantification of the chondrocyte population within articular cartilage can be achieved across a field of view of several millimetres using laboratory-based micro-CT. The ability to map chondrocytes in 3D opens possibilities for research in fields from skeletal development through to medical device design and treatment of cartilage degeneration.

Journal article

Ng KC, Jeffers J, Beaule P, 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

Doyle R, van Arkel R, Jeffers J, 2019, The 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

Seating a cementless acetabular cup via impaction is a balancing act; good cup fixation must be obtained to ensure adequate bone in‐growth and cup apposition, while acetabular fracture must be avoided. Good impaction technique is essential to the success of hip arthroplasty. Yet little guidance exists in the literature to inform surgeons on ‘how hard’ to hit. A drop rig and synthetic bone model were used to vary the energy of impaction strikes in low and high density synthetic bone, while key parameters such as dynamic strain (quantifying fracture risk), implant fixation and polar gap were measured. For high energy impaction (15 J) in low density synthetic bone a peak tensile strain was observed during impaction that was up to 3.4x as large as post‐strike strain, indicating a high fracture risk. Diminishing returns were observed for pushout fixation with increasing energy. 85% of the pushout fixation achieved using a 15 J impaction strike was attained by using a 7.5 J strike energy. Similarly polar gap was only minimally reduced at high impaction energies. Therefore it is suggested that higher energy strikes increase fracture risk, but do not offer large improvements to fixation or implant‐bone apposition. It may difficult be for surgeons to accurately deliver specific impaction energies, suggesting there is scope for operative tools to manage implant seating.

Journal article

Barnes S, Clasper J, Bull A, Jeffers Jet 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

In comparison to through knee amputees the outcomes for above‐the‐knee amputees are relatively poor; based on this novel techniques have been developed. Most current percutaneous implant based solutions for transfemoral amputees make use of high stiffness intramedullary rods for skeletal fixation which can have risks including infection, femoral fractures and bone resorption due to stress shielding. This work details the cadaveric testing of a short, cortical bone stiffness matched subcutaneous implant, produced using additive manufacture, to determine bone implant micromotion and push out load. The results for the micromotions were all less than 20 microns and the mean push out load was 2099 Newtons. In comparison to a solid control, the stiffness matched implant exhibited significantly higher micromotion distributions and no significant difference in terms of push out load. These results suggest that, for the stiffness matched implant at time zero, osseointegration would be facilitated and that the implant would be securely anchored. For these metrics, this provides justification for the use of a short stem implant for transfemoral amputees in this subcutaneous application.

Journal article

Ghouse S, Reznikov N, Boughton O, Babu S, Ng KCG, Blunn G, Cobb J, Stevens M, Jeffers Jet 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

An increasing volume of work supports utilising the mechanobiology of bone for bone ingrowth into a porous scaffold. However, typically during in vivo testing of implants, the mechanical properties of the bone being replaced are not quantified. Consequently there remains inconsistencies in the literature regarding ‘optimum’ pore size and porosity for bone ingrowth. It is also difficult to compare ingrowth results between studies and to translate in vivo animal testing to human subjects without understanding the mechanical environment. This study presents a clinically applicable approach to determining local bone mechanical properties and design of a scaffold with similar properties. The performance of the scaffold was investigated in vivo in an ovine model.The density, modulus and strength of trabecular bone from the medial femoral condyle from ovine bones was characterised and power-law relationships were established. A porous titanium scaffold, intended to maintain bone mechanical homeostasis, was additively manufactured and implanted into the medial femoral condyle of 6 ewes. The stiffness of the scaffold varied throughout the heterogeneous structure and matched the stiffness variation of bone at the surgical site. Bone ingrowth into the scaffold was 10.73 ± 2.97% after 6 weeks. Fine woven bone, in the interior of the scaffold, and intense formations of more developed woven bone overlaid with lamellar bone at the implant periphery were observed. The workflow presented will allow future in vivo testing to test specific bone strains on bone ingrowth in response to a scaffold and allow for better translation from in vivo testing to commercial implants.

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 KC, van Arkel R, Jeffers J, Rodriguez y Baena Fet al., 2019, Robotic hip joint testing: Development and experimental protocols, Medical Engineering and Physics, Vol: 63, Pages: 57-62, ISSN: 1350-4533

The use of robotic systems combined with force sensing is emerging as the gold standard for in vitro biomechanical joint testing, due to the advantage of controlling all six degrees of freedom independently of one another. This paper describes a novel robotic platform and the experimental protocol used for hip joint testing. An experimental protocol implemented optical tracking and registration techniques in order to define the position of the hip joint centre of rotation (COR) in the coordinate system of the robot's end effector. The COR coordinates defined the origin of the task-related coordinate system used to control the robot, with a hybrid force/position law to simulate standard clinical tests. The axes of this frame were defined using the International Society of Biomechanics (ISB) anatomical coordinate system.Experiments were carried out on two cadaveric hip joint specimens using the robotic testing platform and a mechanical testing rig previously developed and described by our group. Simulated internal-external and adduction/abduction laxity tests were carried out with both systems and the resulting peak range of motion (ROM) was measured. Similarities and differences were observed in these experiments, which were used to highlight some of the limitations of conventional systems and the corresponding advantages of robotics, further emphasising their added value in vitro testing.

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

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

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

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

van Arkel RJ, Jeffers JRT, Amis AA, 2017, Editorial Commentary: Anatomical Vandalism of the Hip? Hip Capsular Repair Seems a Sound Adjunct to Hip Arthroscopic Surgery, ARTHROSCOPY-THE JOURNAL OF ARTHROSCOPIC AND RELATED SURGERY, Vol: 33, Pages: 314-316, ISSN: 0749-8063

Journal article

Sopher RS, Amis AA, Davies DC, Jeffers JRTet al., 2017, The influence of muscle pennation angle and cross-sectional area on contact forces in the ankle joint, JOURNAL OF STRAIN ANALYSIS FOR ENGINEERING DESIGN, Vol: 52, Pages: 12-23, ISSN: 0309-3247

Journal article

van Arkel RJ, Jeffers JRT, 2016, In vitro hip testing in the International Society of Biomechanics coordinate system, JOURNAL OF BIOMECHANICS, Vol: 49, Pages: 4154-4158, ISSN: 0021-9290

Journal article

van Arkel RJ, Amis AA, Jeffers JRT, 2015, The envelope of passive motion allowed by the capsular ligaments of the hip, JOURNAL OF BIOMECHANICS, Vol: 48, Pages: 3803-3809, ISSN: 0021-9290

Journal article

Aqil A, Sheikh HQ, Masjedi M, Jeffers J, Cobb Jet al., 2015, Birmingham Mid-Head Resection Periprosthetic Fracture., Clin Orthop Surg, Vol: 7, Pages: 402-405

Total hip arthroplasty in the young leads to difficult choices in implant selection. Until recently bone conserving options were not available for younger patients with deficient femoral head bone stock. The novel Birmingham Mid-Head Resection (BMHR) device offers the option of bone conserving arthroplasty in spite of deficient femoral head bone stock. Femoral neck fracture is a known complication of standard resurfacing arthroplasty and is the most common reason for revision. It is unknown whether this remains to be the case for the BMHR neck preserving implants. We report a case of a 57-year-old male, who sustained a periprosthetic fracture following surgery with a BMHR arthroplasty. This paper illustrates the first reported case of a BMHR periprosthetic fracture. The fracture pattern is spiral in nature and reaches to the subtrochanteric area. This fracture pattern is different from published cadaveric studies, and clinicians using this implant should be aware of this as revision is likely to require a distally fitting, rather than a metaphyseal fitting stem. We have illustrated the surgical technique to manage this rare complication.

Journal article

van Arkel RJ, Amis AA, Cobb JP, Jeffers JRTet al., 2015, The capsular ligaments provide more hip rotational restraint than the acetabular labrum and the ligamentum teres, BONE & JOINT JOURNAL, Vol: 97B, Pages: 484-491, ISSN: 2049-4394

Journal article

Puthumanapully PK, Harris SJ, Leong A, Cobb JP, Amis AA, Jeffers Jet al., 2014, A morphometric study of normal and varus knees, KNEE SURGERY SPORTS TRAUMATOLOGY ARTHROSCOPY, Vol: 22, Pages: 2891-2899, ISSN: 0942-2056

Journal article

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