Publications
113 results found
Hansen UN, 2016, Dynamic three-dimensional shoulder MRI during active motion for investigation of rotator cuff diseases, PLOS One, Vol: 11, ISSN: 1932-6203
BackgroundMRI is the standard methodology in diagnosis of rotator cuff diseases. However, many patients continue to have pain despite treatment, and MRI of a static unloaded shoulder seems insufficient for best diagnosis and treatment. This study evaluated if Dynamic MRI provides novel kinematic data that can be used to improve the understanding, diagnosis and best treatment of rotator cuff diseases.MethodsDynamic MRI provided real-time 3D image series and was used to measure changes in the width of subacromial space, superior-inferior translation and anterior-posterior translation of the humeral head relative to the glenoid during active abduction. These measures were investigated for consistency with the rotator cuff diseases classifications from standard MRI.ResultsThe study included: 4 shoulders with massive rotator cuff tears, 5 shoulders with an isolated full-thickness supraspinatus tear, 5 shoulders with tendinopathy and 6 normal shoulders. A change in the width of subacromial space greater than 4mm differentiated between rotator cuff diseases with tendon tears (massive cuff tears and supraspinatus tear) and without tears (tendinopathy) (p = 0.012). The range of the superior-inferior translation was higher in the massive cuff tears group (6.4mm) than in normals (3.4mm) (p = 0.02). The range of the anterior-posterior translation was higher in the massive cuff tears (9.2 mm) and supraspinatus tear (9.3 mm) shoulders compared to normals (3.5mm) and tendinopathy (4.8mm) shoulders (p = 0.05).ConclusionThe Dynamic MRI enabled a novel measure; ‘Looseness’, i.e. the translation of the humeral head on the glenoid during an abduction cycle. Looseness was better able at differentiating different forms of rotator cuff disease than a simple static measure of relative glenohumeral position.
Geraldes D, Hansen U, Jeffers J, et al., 2016, Interference fit optimisation for small press-fitted pegs, International Society for Technology in Arthroplasty 2015, Publisher: BRITISH EDITORIAL SOCIETY OF BONE & JOINT SURGERY, Pages: 150-150, ISSN: 2049-4416
Shah SIMRANA, Jin ANDI, Wilson HANNAHCP, et al., 2015, Novel Computed Tomography-based Metric Reliably Estimates bone Strength, Offering Potentially Meaningful Enhancement in Clinical Fracture Risk Prediction, European Journal of Medicine, Vol: 10, Pages: 214-220, ISSN: 2310-3434
Osteoporosis with resultant fractures is a major global health problem with huge socioeconomicimplications for patients, families and healthcare services. Areal (2D bone mineraldensity (BMD) assessment is commonly used for predicting such fracture risk, but is unreliable,estimating only about 50% of bone strength. By contrast, computed tomography (CT) basedtechniques could provide improved metrics for estimating bone strength such as bone volumefraction (BVF; a 3D volumetric measure of mineralised bone), enabling cheap, safe and reliablestrategies for clinical application, and to help divert resources to patients identified as most likelyto benefit, meeting an unmet need.Here we describe a novel method for measuring BVF at clinical-CT like low-resolution(550µm voxel size). Femoral heads (n=8) were micro-CT scanned ex-vivo. Micro-CT data weredowngraded in resolution from 30µm to 550µm voxel size and BVF calculated at high and lowresolution. Experimental mechanical testing was applied to measure ex vivo bone strength ofsamples. BVF measures collected at high-resolution showed high correlation (correlationcoefficient r2=0.95) with low-resolution data. Low-resolution BVF metrics showed high correlation(r2=0.96) with calculated sample strength. These results demonstrate that measuring BVF at lowresolution is feasible, which also predicts bone strength. Measures of BVF should be useful for clinically estimating bone strength and fracture risk. The method needs to be validated using clinical CT scans.
Chong DYR, Hansen UN, Amis AA, 2015, CEMENTLESS MIS MINI-KEEL PROSTHESIS REDUCES INTERFACE MICROMOTION VERSUS STANDARD STEMMED TIBIAL COMPONENTS, Journal of Mechanics in Medicine and Biology, Vol: 16, ISSN: 0219-5194
Fixation strength of the cementless knee prostheses is dependent on the initial stability of the fixation and minimal relative motion across the prosthesis–bone interface. Broad mini-keels have been developed for tibial components to allow minimally invasive knee arthroplasty, but the effect of the change in fixation design is unknown. In this study, bone–prosthesis interface micromotions of the mini-keel tibial components (consisting of two designs; one is stemless and another with a stem extension of 45mm) induced by walking and stair climbing were investigated by finite element modeling and compared with standard stemmed design. The prosthesis surface area amenable for bone ingrowth for the mini-keel tibial components (both stemmed and unstemmed) was predicted to be at least 67% larger than the standard stemmed implant, thereby reducing the risk of long-term aseptic loosening. It was also found that while different load patterns may have led to diverse predictions of the magnitude of the interface micromotions and the extent of osseointegration onto the prosthesis, the outcome of design change evaluation in cementless tibial fixations remains unchanged. The mini-keel tibial components were predicted to anchor onto the periprosthetic bone better than the standard stemmed design under all loading conditions investigated.
Geraldes D, Hansen U, Amis A, 2015, Parametric analysis of glenoid implant design, International Society of Biomechanics 2015
Simpson RL, Nazhat SN, Blaker JJ, et al., 2015, A comparative study of the effects of different bioactive fillers in PLGA matrix composites and their suitability as bone substitute materials: a thermo-mechanical and in vitro investigation, Journal of The Mechanical Behavior of Biomedical Materials, Vol: 50, Pages: 277-289, ISSN: 1751-6161
Bone substitute composite materials with poly(L-lactide-co-glycolide) (PLGA) matrices and four different bioactive fillers: CaCO3, hydroxyapatite (HA), 45S5 Bioglass(®) (45S5 BG), and ICIE4 bioactive glass (a lower sodium glass than 45S5 BG) were produced via melt blending, extrusion and moulding. The viscoelastic, mechanical and thermal properties, and the molecular weight of the matrix were measured. Thermogravimetric analysis evaluated the effect of filler composition on the thermal degradation of the matrix. Bioactive glasses caused premature degradation of the matrix during processing, whereas CaCO3 or HA did not. All composites, except those with 45S5 BG, had similar mechanical strength and were stiffer than PLGA alone in compression, whilst all had a lower tensile strength. Dynamic mechanical analysis demonstrated an increased storage modulus (E') in the composites (other than the 45S5 BG filled PLGA). The effect of water uptake and early degradation was investigated by short-term in vitro aging in simulated body fluid, which indicated enhanced water uptake over the neat polymer; bioactive glass had the greatest water uptake, causing matrix plasticization. These results enable a direct comparison between bioactive filler type in poly(α-hydroxyester) composites, and have implications when selecting a composite material for eventual application in bone substitution.
Sukjamsri C, Amis A, Hansen UN, et al., 2015, Digital volume correlation and micro-CT: an in-vitro technique for measuring full-field interface micromotion around polyethylene implants, Journal of Biomechanics, Vol: 48, Pages: 3447-3454, ISSN: 0021-9290
Micromotion around implants is commonly measured using displacement-sensor techniques. Due to the limitations of these techniques, an alternative approach (DVC-μCT) using digital volume correlation (DVC) and micro-CT (μCT) was developed in this study. The validation consisted of evaluating DVC-μCT based micromotion against known micromotions (40, 100 and 150 μm) in a simplified experiment. Subsequently, a more clinically realistic experiment in which a glenoid component was implanted into a porcine scapula was carried out and the DVC-μCT measurements during a single load cycle (duration 20 min due to scanning time) was correlated with the manual tracking of micromotion at 12 discrete points across the implant interface. In this same experiment the full-field DVC-μCT micromotion was compared to the full-field micromotion predicted by a parallel finite element analysis (FEA). It was found that DVC-μCT micromotion matched the known micromotion of the simplified experiment (average/peak error=1.4/1.7 μm, regression line slope=0.999) and correlated with the micromotion at the 12 points tracked manually during the realistic experiment (R2=0.96). The DVC-μCT full-field micromotion matched the pattern of the full-field FEA predicted micromotion. This study showed that the DVC-μCT technique provides sensible estimates of micromotion. The main advantages of this technique are that it does not damage important parts of the specimen to gain access to the bone–implant interface, and it provides a full-field evaluation of micromotion as opposed to the micromotion at just a few discrete points. In conclusion the DVC-μCT technique provides a useful tool for investigations of micromotion around plastic implants.
Tuncer M, Patel R, Cobb JP, et al., 2015, Variable bone mineral density reductions post-unicompartmental knee arthroplasty, KNEE SURGERY SPORTS TRAUMATOLOGY ARTHROSCOPY, Vol: 23, Pages: 2230-2236, ISSN: 0942-2056
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- Citations: 6
Geraldes D, Hansen U, Amis A, 2015, Parametric analysis of glenoid implant design, European Society of Biomechanics 2015
Geraldes D, Hansen U, Amis A, 2014, A framework for parametric analysis of glenoid implant design, MECBioengineering 2014
Sukjamsri C, Geraldes D, Gregory T, et al., 2014, Micro computed tomography and digital volume correlation techniques to determine micromotion in cementless arthroplasty, World Congress of Biomechanics 2014
Geraldes D, Hansen U, Jeffers J, et al., 2014, A framework for parametric analysis of glenoid implant design, International Society for Technology in Arthroplasty 2014
Tuncer M, Hansen UN, Amis AA, 2014, Prediction of structural failure of tibial bone models under physiological loads: Effect of CT density-modulus relationships, MEDICAL ENGINEERING & PHYSICS, Vol: 36, Pages: 991-997, ISSN: 1350-4533
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- Citations: 28
Gregory T, Hansen U, Khanna M, et al., 2014, A CT scan protocol for the detection of radiographic loosening of the glenoid component after total shoulder arthroplasty, Acta Orthopaedica, Vol: 85, Pages: 91-96, ISSN: 0001-6470
Background and purpose It is difficult to evaluate glenoid component periprosthetic radiolucencies in total shoulder arthroplasties (TSAs) using plain radiographs. This study was performed to evaluate whether computed tomography (CT) using a specific patient position in the CT scanner provides a better method for assessing radiolucencies in TSA.Methods Following TSA, 11 patients were CT scanned in a lateral decubitus position with maximum forward flexion, which aligns the glenoid orientation with the axis of the CT scanner. Follow-up CT scanning is part of our routine patient care. Glenoid component periprosthetic lucency was assessed according to the Molé score and it was compared to routine plain radiographs by 5 observers.Results The protocol almost completely eliminated metal artifacts in the CT images and allowed accurate assessment of periprosthetic lucency of the glenoid fixation. Positioning of the patient within the CT scanner as described was possible for all 11 patients. A radiolucent line was identified in 54 of the 55 observed CT scans and osteolysis was identified in 25 observations. The average radiolucent line Molé score was 3.4 (SD 2.7) points with plain radiographs and 9.5 (SD 0.8) points with CT scans(p = 0.001). The mean intra-observer variance was lower in the CT scan group than in the plain radiograph group (p = 0.001).Interpretation The CT scan protocol we used is of clinical value in routine assessment of glenoid periprosthetic lucency after TSA. The technique improves the ability to detect and monitor radiolucent lines and, therefore, possibly implant loosening also.
Gregory TM, Sankey A, Augereau B, et al., 2013, Accuracy of Glenoid Component Placement in Total Shoulder Arthroplasty and Its Effect on Clinical and Radiological Outcome in a Retrospective, Longitudinal, Monocentric Open Study, PLOS ONE, Vol: 8, ISSN: 1932-6203
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- Citations: 43
Geraldes D, Sukjamsri C, Gregory T, et al., 2013, A study of micromotion in cementless arthroplasty using digital volume correlation technique, Tomography for Scientific Advancement Symposium 2013
Tuncer M, Cobb JP, Hansen UN, et al., 2013, Validation of multiple subject-specific finite element models of unicompartmental knee replacement, MEDICAL ENGINEERING & PHYSICS, Vol: 35, Pages: 1457-1464, ISSN: 1350-4533
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- Citations: 18
Gregory T, Hansen U, Emery R, et al., 2012, Total shoulder arthroplasty does not correct the orientation of the eroded glenoid, ACTA ORTHOPAEDICA, Vol: 83, Pages: 529-535, ISSN: 1745-3674
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- Citations: 19
Chong DYR, Hansen UN, van der Venne R, et al., 2011, The influence of tibial component fixation techniques on resorption of supporting bone stock after total knee replacement, JOURNAL OF BIOMECHANICS, Vol: 44, Pages: 948-954, ISSN: 0021-9290
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- Citations: 52
Chong DYR, Hansen UN, Amis AA, 2011, THE INFLUENCE OF TIBIAL PROSTHESIS DESIGN FEATURES ON STRESSES RELATED TO ASEPTIC LOOSENING AND STRESS SHIELDING, JOURNAL OF MECHANICS IN MEDICINE AND BIOLOGY, Vol: 11, Pages: 55-72, ISSN: 0219-5194
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- Citations: 11
Stuckey DJ, Ishii H, Chen Q-Z, et al., 2010, Magnetic Resonance Imaging Evaluation of Remodeling by Cardiac Elastomeric Tissue Scaffold Biomaterials in a Rat Model of Myocardial Infarction, TISSUE ENGINEERING PART A, Vol: 16, Pages: 3395-3402, ISSN: 1937-3341
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- Citations: 65
Vandenbussche E, Saffarini M, Hansen U, et al., 2010, Measurement of femoral head penetration in polyethylene using a 3-dimensional CT-scan technique, ACTA ORTHOPAEDICA, Vol: 81, Pages: 563-569, ISSN: 1745-3674
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- Citations: 16
Chong DYR, Hansen UN, Amis AA, 2010, Analysis of bone-prosthesis interface micromotion for cementless tibial prosthesis fixation and the influence of loading conditions, JOURNAL OF BIOMECHANICS, Vol: 43, Pages: 1074-1080, ISSN: 0021-9290
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- Citations: 66
Junaid S, Gupta S, Sanghavi S, et al., 2010, Failure mechanism of the all-polyethylene glenoid implant, JOURNAL OF BIOMECHANICS, Vol: 43, Pages: 714-719, ISSN: 0021-9290
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- Citations: 30
Gregory T, Hansen U, Taillieu F, et al., 2009, Glenoid Loosening after Total Shoulder Arthroplasty: An In Vitro CT-Scan Study, JOURNAL OF ORTHOPAEDIC RESEARCH, Vol: 27, Pages: 1589-1595, ISSN: 0736-0266
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- Citations: 33
Amadi H O, Bull A M J, Hansen U, 2009, A numerical tool for the reconstruction of the physiological kinematics of the gienohumeral joint (GHJ), IMechE Conference on Engineering the Upper Limb, Publisher: SAGE, Pages: 833-837
The aim of this study was to develop and test a robust approach to apply a joint coordinate system (JCS) to imaging data sets of the glenohumeral joint and to reconstruct the kinematics with six degrees of freedom (6DOF) in order to investigate shoulder pathologies related to instability. Visible human data were used to reconstruct bony morphology. Landmarks were used to define axes for body-fixed Cartesian coordinate frames on the humerus and scapula. These were applied to a three-cylinder open-chain JCS upon which the humeral 6DOF motions relative to the scapula were implemented. Software was written that applies 6DOF input variables to rotate and translate the nodes of the surface geometry of the humerus relative to the scapula in a global coordinate frame. The instantaneous relative position and orientation of the humerus for a given set of variables were thus reconstructed on the bone models for graphical display. This tool can be used for graphical animation of shoulder kinematics, demonstrating clinical assessments, and allowing further analysis of the function of tissues within the joint.
Hopkins AR, Hansen UN, 2009, Primary stability in reversed-anatomy glenoid components., Proc Inst Mech Eng H, Vol: 223, Pages: 805-812, ISSN: 0954-4119
Reversed-anatomy shoulder replacement is advocated for patients with poor rotator cuff condition, for whom an anatomical reconstruction would provide little or no stability. Modern generations of this concept appear to be performing well in the short-term to midterm clinical follow-up. These designs are almost always non-cemented, requiring a high degree of primary stability to encourage bone on-growth and so to establish long-term fixation. Six different inverse-anatomy glenoid implants, currently on the market and encompassing a broad range of geometrical differences, were compared on the basis of their ability to impart primary stability through the minimization of interface micromotions. Fixing screws were only included in the supero-inferior direction in appropriate implants and were always inclined at the steepest available angle possible during surgery (up to a maximum of 30 degrees). The extent of predicted bony on-growth was, of course, highly dependent on the threshold for interface micromotion. In some instances an additional 30 per cent of the interface was predicted to promote bone on-growth when the threshold was raised from 20 microm to 50 microm. With maximum thresholds of micromotion for bone on-growth set to 30 microm, the Zimmer Anatomical device was found to be the most stable of the series of the six designs tested herein, achieving an additional 3 per cent (by surface area) of bone on-growth above the closest peer product (Biomet Verso). When this threshold was raised to 50 microm, the Biomet Verso design was most stable (3 per cent above the second-most stable design, the Zimmer Anatomical). Peak micromotions were not a good indicator of the predicted area of bone on-growth and could lead to some misinterpretation of the implant's overall performance. All but one of the implants tested herein provided primary stability sufficient to resist motions in excess of 150 microm at the interface.
Hopkins AR, Hansen UN, 2009, Primary stability in reversed-anatomy glenoid components, IMechE Conference on Engineering the Upper Limb, Publisher: SAGE PUBLICATIONS LTD, Pages: 805-812, ISSN: 0954-4119
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- Citations: 12
Southgate DF, Hill AM, Alexander S, et al., 2009, The range of axial rotation of the glenohumeral joint., J Biomech, Vol: 42, Pages: 1307-1312, ISSN: 1873-2380
There is a paucity of data in the literature on the restraining effects of the glenohumeral (GH) ligaments; cadaveric testing is one of the best methods for determining the function of these types of tissues. The aim of this work was to commission a custom-made six degrees of freedom (dof) joint loading apparatus and to establish a protocol for laxity testing of cadaveric shoulder specimens. Nine cadaveric shoulder specimens were used in this study and each specimen had all muscle resected leaving the scapula, humerus (transected at mid-shaft) and GH capsule. Specimens were mounted on the testing apparatus with the joint in the neutral position and at 30 degrees, 60 degrees and 90 degrees GH abduction in the coronal, scapula and 30 degrees forward flexion planes. For each orientation, 0-1 N m in 0.1 N m increments was applied in internal/external rotation and the angular displacement recorded. The toe-region of the moment-displacement curves ended at approximately +/-0.5 N m. The highest rotational range of motion for the joint was 140 degrees for +/-1.0 N m at 30 degrees GH abduction in the scapula plane. The range of motion shifted towards external rotation with increasing levels of abduction. The results provide the optimum loading regime to pre-condition shoulder specimens and minimise viscoelastic effects in the ligaments prior to laxity testing (>0.5 N m at 30 degrees GH abduction in any of the three planes). Knowledge of the mechanical properties of the GH capsuloligamentous complex has implications for modelling of the shoulder as well surgical planning and intervention.
Chong DYR, Hansen UN, Amis AA, 2009, COMPUTATIONAL BIOMECHANICAL ANALYSIS OF FIXATION PERFORMANCE AND BONE RESORPTION OF TIBIAL PROSTHESIS IMPLANTATION, ASME Summer Bioengineering Conference, Publisher: AMER SOC MECHANICAL ENGINEERS, Pages: 975-976
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