430 results found
Lord B, Amis AA, 2016, The envelope of laxity of the pivot shift test, Rotatory Knee Instability: An Evidence Based Approach, Pages: 223-234, ISBN: 9783319320694
© Springer International Publishing Switzerland 2017. The pivot shift is a dynamic test of knee laxity which correlates with subjective sensations of knee instability. As the knee flexes from full extension, the tibia subluxes, both in anterior translation and internal rotation, so that the lateral femoral condyle moves ‘downhill’ to the posterior edge of the tibial plateau under the influence of the compressive joint load. With further knee flexion, the tension in the iliotibial tract eventually overcomes the load which has maintained the subluxation and then the tibia is suddenly reduced to its anatomical articulation. Thus, the envelope of laxity of the pivot shift shows a pattern of simultaneous gradual pathological anterior translation and internal rotation, occurring over approximately 35° of knee flexion, followed by a relatively sudden reduction, which is a falling back posteriorly and externally to the anatomical position. It is desirable to measure both tibial translations and rotations to understand each injured knee, because differing patterns of injury may explain the wide range of tibiofemoral movements, such as the relative amount of tibial translation versus rotation, that have been reported during the pivot shift.
Barcellona MG, Morrissey MC, Milligan P, et al., 2015, The effect of knee extensor open kinetic chain resistance training in the ACL-injured knee, KNEE SURGERY SPORTS TRAUMATOLOGY ARTHROSCOPY, Vol: 23, Pages: 3168-3177, ISSN: 0942-2056
Athwal KK, Daou HE, Kittl C, et al., 2015, The superficial medial collateral ligament is the primary medial restraint to knee laxity after cruciate-retaining or posterior-stabilised total knee arthroplasty: effects of implant type and partial release., Knee Surgery, Sports Traumatology, Arthroscopy, Vol: 24, Pages: 2646-2655, ISSN: 0942-2056
PURPOSE: The aim of this study was to quantify the contributions of medial soft tissues to stability following cruciate-retaining (CR) or posterior-stabilised (PS) total knee arthroplasty (TKA). METHODS: Using a robotic system, eight cadaveric knees were subjected to ±90-N anterior-posterior force, ±5-Nm internal-external and ±8-Nm varus-valgus torques at various flexion angles. The knees were tested intact and then with CR and PS implants, and successive cuts of the deep and superficial medial collateral ligaments (dMCL, sMCL) and posteromedial capsule (PMC) quantified the percentage contributions of each structure to restraining the applied loads. RESULTS: In implanted knees, the sMCL restrained valgus rotation (62 % across flexion angles), anterior-posterior drawer (24 and 10 %, respectively) and internal-external rotation (22 and 37 %). Changing from CR TKA to PS TKA increased the load on the sMCL when resisting valgus loads. The dMCL restrained 11 % of external and 13 % of valgus rotations, and the PMC was significant at low flexion angles. CONCLUSIONS: This work has shown that medial release in the varus knee should be minimised, as it may inadvertently result in a combined laxity pattern. There is increasing interest in preserving constitutional varus in TKA, and this work argues for preservation of the sMCL to afford the surgeon consistent restraint and maintain a balanced knee for the patient.
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.
Masouros S, Halewood C, Bull A, et al., 2015, Biomechanics, Expertise orthopadie und unfallchirurgie: Knie, Editors: Kohn, ISBN: 978-3-1317500-1-3
Geraldes D, Hansen U, Amis A, 2015, Parametric analysis of glenoid implant design, International Society of Biomechanics 2015
Geraldes D, Hansen U, Amis A, 2015, An automated framework for parametric analysis glenoid implant design, Bath Biomechanics Symposium 2015
van Arkel R, Amis A, Jeffers J, 2015, The envelope of passive motion allowed by the capsular ligaments of the hip, Journal of Biomechanics, Vol: 48, Pages: 3803-3809, ISSN: 1873-2380
Laboratory data indicate the hip capsular ligaments prevent excessive range of motion, mayprotect the joint against adverse edge loading and contribute to synovial fluid replenishmentat the cartilage surfaces of the joint. However, their repair after joint preserving orarthroplasty surgery is not routine. In order to restore their biomechanical function after hipsurgery, the positions of the hip at which the ligaments engage, together with their tensionswhen they engage is required. Nine cadaveric left hips without pathology were skeletonisedexcept for the hip joint capsule and mounted in a six-degrees-of-freedom testing rig. A 5Nmtorque was applied to all rotational degrees-of-freedom separately to quantify the passiverestraint envelope throughout the available range of motion with the hip functionally loaded.The capsular ligaments allowed the hip to internally/externally rotate with a large range ofun-resisted rotation (up to 50±10°) in mid-flexion and mid-ab/adduction but this was reducedtowards the limits of flexion/extension and ab/adduction such that there was a near-zeroslack region in some positions (p<0.014). The slack region was not symmetrical; the midslackpoint was found with internal rotation in extension and external rotation in flexion(p<0.001). The torsional stiffness of the capsular ligamentous restraint averaged0.8±0.3Nm/° and was greater in positions where there were large slack regions. These dataprovide a target for restoration of normal capsular ligament tensions after joint preserving hipsurgery. Ligament repair is technically demanding, particularly for arthroscopic procedures,but failing to restore their function may increase the risk of osteoarthritic degeneration.
Stephen JM, Dodds AL, Lumpaopong P, et al., 2015, The Ability of Medial Patellofemoral Ligament Reconstruction to Correct Patellar Kinematics and Contact Mechanics in the Presence of a Lateralized Tibial Tubercle, AMERICAN JOURNAL OF SPORTS MEDICINE, Vol: 43, Pages: 2198-2207, ISSN: 0363-5465
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
Kittl C, Schmeling A, Amis AA, 2015, The patellofemoral joint. Anatomy, biomechanics, and surgical interventions, ARTHROSKOPIE, Vol: 28, Pages: 172-180, ISSN: 0933-7946
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.
Halewood C, Traynor A, Bellemans J, et al., 2015, Anteroposterior Laxity After Bicruciate-Retaining Total Knee Arthroplasty Is Closer to the Native Knee Than ACL-Resecting TKA: A Biomechanical Cadaver Study., Journal of Arthroplasty, ISSN: 1532-8406
The purpose of this study was to examine whether a bicruciate retaining (BCR) TKA would yield anteroposterior (AP) laxity closer to the native knee than a posterior cruciate ligament retaining (CR) TKA. A BCR TKA was designed and compared to CR TKA and the native knee using cadaver specimens. AP laxity with the CR TKA was greater than the native knee (P=0.006) and BCR TKA (P=0.039), but no difference was found between the BCR TKA and the native knee. No significant differences were found in rotations between the prostheses and the native knee. BCR TKA was shown to be surgically feasible, reduced AP laxity versus CR TKA, and may improve knee stability without using conforming geometry in the implant design.
Ghosh KM, Hunt N, Blain A, et al., 2015, Isolated popliteus tendon injury does not lead to abnormal laxity in posterior-stabilised total knee arthroplasty, KNEE SURGERY SPORTS TRAUMATOLOGY ARTHROSCOPY, Vol: 23, Pages: 1763-1769, ISSN: 0942-2056
Wiik AV, Aqil A, Tankard S, et al., 2015, Downhill walking gait pattern discriminates between types of knee arthroplasty: improved physiological knee functionality in UKA versus TKA, KNEE SURGERY SPORTS TRAUMATOLOGY ARTHROSCOPY, Vol: 23, Pages: 1748-1755, ISSN: 0942-2056
Hansen UN, sukjamsri, amis, 2015, Digital volumecorrelationandmicro-CT:Anin-vitrotechniquefor measuringfull-field interfacemicromotionaroundpolyethyleneimplants, Journal of Biomechanics, ISSN: 1873-2380
Sukjamsri, Amis, Hansen UN, 2015, Digital volume correlation and micro-CT: An in-vitro technique for measuring full-field interface micromotion around polyethylene implants, Journal of Biomechanics, ISSN: 1873-2380
Halewood C, Masouros S, Amis AA, 2015, Structure and function of the menisci, Meniscal Allograft Transplantation. A comprehensive review., Editors: Getgood, Spalding, Cole, Gersoff, Verdonk, ISBN: 978-0-9558873-5-2
Halewood C, Lumpaopong P, Stephen JM, et al., 2015, Functional Biomechanics with Cadaver Specimens, Experimental Research Methods in Orthopedics and Trauma, Editors: Simpson, Augat, Publisher: Thieme Medical Publishers, ISBN: 9783131731111
This book provides a comprehensive summary of all current research methodologies for translational and pre-clinical studies in biomechanics and orthopedic trauma surgery.
Halewood C, Amis AA, 2015, Clinically relevant biomechanics of the knee capsule and ligaments, Knee Surgery, Sports Traumatology, Arthroscopy, Vol: 23, Pages: 2789-2796, ISSN: 0942-2056
The paper describes the concepts of primary and secondary restraints to knee joint stability and explains systematically how the tibia is stabilised against translational forces and rotational torques in different directions and axes, and how those vary across the arc of flexion–extension. It also shows how the menisci act to stabilise the knee, in addition to load carrying across the joint. It compares the properties of the natural stabilising structures with the strength and stiffness of autogenous tissue grafts and relates those strengths to the strength of graft fixation devices. A good understanding of the biomechanical behaviour of these various structures in the knee will help the surgeon in the assessment and treatment of single and multi-ligament injuries.
van Arkel RJ, Amis AA, Cobb JP, et 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
In this in vitro study of the hip joint we examined which soft tissues act as primary and secondary passive rotational restraints when the hip joint is functionally loaded. A total of nine cadaveric left hips were mounted in a testing rig that allowed the application of forces, torques and rotations in all six degrees of freedom. The hip was rotated throughout a complete range of movement (ROM) and the contributions of the iliofemoral (medial and lateral arms), pubofemoral and ischiofemoral ligaments and the ligamentum teres to rotational restraint was determined by resecting a ligament and measuring the reduced torque required to achieve the same angular position as before resection. The contribution from the acetabular labrum was also measured. Each of the capsular ligaments acted as the primary hip rotation restraint somewhere within the complete ROM, and the ligamentum teres acted as a secondary restraint in high flexion, adduction and external rotation. The iliofemoral lateral arm and the ischiofemoral ligaments were primary restraints in two-thirds of the positions tested. Appreciation of the importance of these structures in preventing excessive hip rotation and subsequent impingement/instability may be relevant for surgeons undertaking both hip joint preserving surgery and hip arthroplasty.
Stephen JM, Halewood C, Kittl C, et al., 2015, The influence of posterior medial meniscocapsular lesions on tibiofemoral joint laxity in ACL deficient and reconstructed knees, British Association of Surgery of the Knee
Kawaguchi Y, Kondo E, Takeda R, et al., 2015, The Role of Fibers in the Femoral Attachment of the Anterior Cruciate Ligament in Resisting Tibial Displacement, ARTHROSCOPY-THE JOURNAL OF ARTHROSCOPIC AND RELATED SURGERY, Vol: 31, Pages: 435-444, ISSN: 0749-8063
Kittl C, Halewood C, Stephen JM, et al., 2015, Length Change Patterns in the Lateral Extra-articular Structures of the Knee and Related Reconstructions, AMERICAN JOURNAL OF SPORTS MEDICINE, Vol: 43, Pages: 354-362, ISSN: 0363-5465
Stephen JM, Kittl C, Williams A, et al., The effect of graft type and femoral positioning on patellofemoral contact pressure and kinematics after medial patellofemoral ligament reconstruction, British Association for Surgery of the Knee
Geraldes D, Hansen U, Amis A, 2015, Parametric analysis of glenoid implant design, European Society of Biomechanics 2015
Bonner TJ, Newell N, Karunaratne A, et al., 2015, Strain-rate sensitivity of the lateral collateral ligament of the knee, JOURNAL OF THE MECHANICAL BEHAVIOR OF BIOMEDICAL MATERIALS, Vol: 41, Pages: 261-270, ISSN: 1751-6161
Gregory TM, Sukjamsri C, Hansen U, et al., 2015, Glenoid Aseptic Loosening After Anatomical Shoulder Replacement: a Systematic Review of the Radiolucent Line Significance and of the Loosening Mechanisms, E-MEMOIRES DE L ACADEMIE NATIONALE DE CHIRURGIE, Vol: 14, Pages: 7-12, ISSN: 1634-0647
Keller R, Amis AA, 2015, Anatomy and Biomechanics of the Natural Knee and After TKR, The Unhappy Total Knee Replacement, Editors: Hirschmann, Becker, Publisher: Springer, Pages: 3-15, ISBN: 978-3-319-08098-7
This book addresses the need for improved diagnostic and treatment guidelines for patients in whom total knee arthroplasty (TKA) has had an unsatisfactory outcome. It opens by discussing the basics of TKA and the various causes of failure and pain. Diagnostic aspects are considered in detail, with attention to advances in clinical investigation, laboratory analysis and in particular, imaging techniques. In addition, helpful state of the art diagnostic algorithms are presented. Specific pathology-related treatment options, including conservative approaches and salvage and revision TKA strategies, are then explained, with identification of pitfalls and key points. A series of illustrative cases cover clinical scenarios frequently encountered in daily clinical practice. The evidence-based, clinically focused guidance provided in this book, written by internationally renowned experts, will assist surgeons in achieving the most effective management of these challenging cases.
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