443 results found
Merican AM, Iranpour F, Amis AA, 2016, Iliotibial band tension reduces patellar lateral stability, J Orthop Res
Sopher R, Amis A, Davies D, et al., 2016, 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
Data about a muscle’s fibre pennation angle and physiological cross-sectional area are used in musculoskeletal modelling to estimate muscle forces, which are used to calculate joint contact forces. For the leg, muscle architecture data are derived from studies that measured pennation angle at the muscle surface, but not deep within it. Musculoskeletal models developed to estimate joint contact loads have usually been based on the mean values of pennation angle and physiological cross-sectional area.Therefore, the first aim of this study was to investigate differences between superficial and deep pennation angles within each muscle acting over the ankle and predict how differences may influence muscle forces calculated in musculoskeletal modelling. The second aim was to investigate how inter-subject variability in physiological cross-sectional area and pennation angle affects calculated ankle contact forces.Eight cadaveric legs were dissected to excise the muscles acting over the ankle. The mean surface and deep pennation angles, fibre length and physiological cross-sectional area were measured. Cluster analysis was applied to group the muscles according to their architectural characteristics. A previously validated OpenSim model was used to estimate ankle muscle forces and contact loads using architecture data from all eight limbs.The mean surface pennation angle for soleus was significantly greater (54%) than the mean deep pennation angle. Cluster analysis revealed three groups of muscles with similar architecture and function: deep plantarflexors and peroneals, superficial plantarflexors and dorsiflexors. Peak ankle contact force was predicted to occur before toe-off, with magnitude greater than five times bodyweight. Inter-specimen variability in contact force was smallest at peak force.These findings will help improve the development of experimental and computational musculoskeletal models by providing data to estimate force based on both surface and deep
Lord BR, El-Daou H, Sabnis BM, et al., 2016, Biomechanical comparison of graft structures in anterior cruciate ligament reconstruction, Knee Surgery Sports Traumatology Arthroscopy, Vol: 25, Pages: 559-568, ISSN: 1433-7347
PURPOSE: Double-bundle (DB) anterior cruciate ligament (ACL) reconstruction may offer kinematic restoration superior to anatomic single bundle (SB), but it remains technically challenging. The femoral attachment site has the most effect on ACL graft isometry, so a simplified three-socket (3S) construct which still uses two sockets to cover the femoral ACL attachment is attractive. It was hypothesised that ACL reconstruction using three- and four-socket techniques would more closely restore native knee kinematics compared to anatomic two-socket (SB) surgery. METHODS: Nine cadaveric knees were used to evaluate the kinematics of ACL-intact, ACL-deficient, anatomic SB, three-socket, and DB arthroscopic ACL reconstructions. Suspensory fixation was used, and grafts were tensioned to match the anterior draw of the intact knee at 20°. A six-degree-of-freedom robotic system measured knee laxity under 90 N anterior tibial force and rotational laxity under 5 N-m torque. Combined moments were applied to simulate the pivot-shift subluxation: 4 N-m internal rotation and 8 N-m valgus. RESULTS: Significant differences between reconstructions were not found during anterior tibial loading, apart from SB being more lax than DB at 60° flexion. All reconstructions produced comparable laxity to the intact state, apart from SB at 60°. Significant differences between reconstructions were not found at any flexion angle during tibial internal/external applied torques. Under combined loading, DB produced significantly less laxity than SB constructs apart from anterior tibial translation at 0° and internal rotation at 45°. 3S and DB were comparable to the native knee throughout. CONCLUSION: Although 3S restored laxities to a similar extent to DB, significant superiority over SB surgery was not observed. Although statistically significant differences were found between SB and DB surgery during anterior tibial and simulated pivot-shift loading, both remain
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
Kittl C, El-Daou H, Athwal KK, et al., 2016, The Role of the Anterolateral Structures and the ACL in Controlling Laxity of the Intact and ACL-Deficient Knee: Response., American Journal of Sports Medicine, Vol: 44, Pages: NP15-NP18, ISSN: 1552-3365
Athwal KK, El Daou H, Inderhaug E, et al., 2016, An in vitro analysis of medial structures and a medial soft tissue reconstruction in a constrained condylar total knee arthroplasty, Knee Surgery, Sports Traumatology, Arthroscopy, Vol: 25, Pages: 2646-2655, ISSN: 0942-2056
PurposeThe aim of this study was to quantify the medial soft tissue contributions to stability following constrained condylar (CC) total knee arthroplasty (TKA) and determine whether a medial reconstruction could restore stability to a soft tissue-deficient, CC-TKA knee.MethodsEight cadaveric knees were mounted in a robotic system and tested at 0°, 30°, 60°, and 90° of flexion with ±50 N anterior–posterior force, ±8 Nm varus–valgus, and ±5 Nm internal–external torque. The deep and superficial medial collateral ligaments (dMCL, sMCL) and posteromedial capsule (PMC) were transected and their relative contributions to stabilising the applied loads were quantified. After complete medial soft tissue transection, a reconstruction using a semitendinosus tendon graft was performed, and the effect on kinematic behaviour under equivocal conditions was measured.ResultsIn the CC-TKA knee, the sMCL was the major medial restraint in anterior drawer, internal–external, and valgus rotation. No significant differences were found between the rotational laxities of the reconstructed knee to the pre-deficient state for the arc of motion examined. The relative contribution of the reconstruction was higher in valgus rotation at 60° than the sMCL; otherwise, the contribution of the reconstruction was similar to that of the sMCL.ConclusionThere is contention whether a CC-TKA can function with medial deficiency or more constraint is required. This work has shown that a CC-TKA may not provide enough stability with an absent sMCL. However, in such cases, combining the CC-TKA with a medial soft tissue reconstruction may be considered as an alternative to a hinged implant.
Halewood C, Amis AA, 2016, Physiology: Biomechanics, Surgery of the Meniscus, Pages: 35-45, ISBN: 9783662491867
Stephen JM, Kittl C, Williams A, et al., 2016, Effect of medial patellofemoral ligament reconstruction method on patellofemoral contact pressures and kinematics., American Journal of Sports Medicine, Vol: 44, Pages: 1186-1194, ISSN: 1552-3365
BACKGROUND: There remains a lack of evidence regarding the optimal method when reconstructing the medial patellofemoral ligament (MPFL) and whether some graft constructs can be more forgiving to surgical errors, such as overtensioning or tunnel malpositioning, than others. HYPOTHESIS: The null hypothesis was that there would not be a significant difference between reconstruction methods (eg, graft type and fixation) in the adverse biomechanical effects (eg, patellar maltracking or elevated articular contact pressure) resulting from surgical errors such as tunnel malpositioning or graft overtensioning. STUDY DESIGN: Controlled laboratory study. METHODS: Nine fresh-frozen cadaveric knees were placed on a customized testing rig, where the femur was fixed but the tibia could be moved freely from 0° to 90° of flexion. Individual quadriceps heads and the iliotibial tract were separated and loaded to 205 N of tension using a weighted pulley system. Patellofemoral contact pressures and patellar tracking were measured at 0°, 10°, 20°, 30°, 60°, and 90° of flexion using pressure-sensitive film inserted between the patella and trochlea, in conjunction with an optical tracking system. The MPFL was transected and then reconstructed in a randomized order using a (1) double-strand gracilis tendon, (2) quadriceps tendon, and (3) tensor fasciae latae allograft. Pressure maps and tracking measurements were recorded for each reconstruction method in 2 N and 10 N of tension and with the graft positioned in the anatomic, proximal, and distal femoral tunnel positions. Statistical analysis was undertaken using repeated-measures analyses of variance, Bonferroni post hoc analyses, and paired t tests. RESULTS: Anatomically placed grafts during MPFL reconstruction tensioned to 2 N resulted in the restoration of intact medial joint contact pressures and patellar tracking for all 3 graft types investigated (P > .050). However, femoral tunnels positioned proxim
Ghosh KM, Manning WA, Blain AP, et al., 2016, Influence of increasing construct constraint in the presence of posterolateral deficiency at knee replacement: A biomechanical study, JOURNAL OF ORTHOPAEDIC RESEARCH, Vol: 34, Pages: 427-434, ISSN: 0736-0266
Stephen JM, Kader D, Lumpaopong P, et al., 2016, The effect of femoral tunnel position and graft tension on patellar contact mechanics and kinematics after medial patellofemoral ligament reconstruction (vol 42, pg 364, 2014), AMERICAN JOURNAL OF SPORTS MEDICINE, Vol: 44, Pages: NP11-NP11, ISSN: 0363-5465
Kittl C, El-Daou H, Athwal KK, et al., 2016, The Role of the Anterolateral Structures and the ACL in Controlling Laxity of the Intact and ACL-Deficient Knee, AMERICAN JOURNAL OF SPORTS MEDICINE, Vol: 44, Pages: 345-354, ISSN: 0363-5465
Background:Anterolateral rotatory instability (ALRI) may result from combined anterior cruciate ligament (ACL) and lateral extra-articular lesions, but the roles of the anterolateral structures remain controversial.Purpose:To determine the contribution of each anterolateral structure and the ACL in restraining simulated clinical laxity in both the intact and ACL-deficient knee.Study Design:Controlled laboratory study.Methods:A total of 16 knees were tested using a 6 degrees of freedom robot with a universal force-moment sensor. The system automatically defined the path of unloaded flexion/extension. At different flexion angles, anterior-posterior, internal-external, and internal rotational laxity in response to a simulated pivot shift were tested. Eight ACL-intact and 8 ACL-deficient knees were tested. The kinematics of the intact/deficient knee was replayed after transecting/resecting each structure of interest; therefore, the decrease in force/torque reflected the contribution of the transected/resected structure in restraining laxity. Data were analyzed using repeated-measures analyses of variance and paired t tests.Results:For anterior translation, the intact ACL was clearly the primary restraint. The iliotibial tract (ITT) resisted 31% ± 6% of the drawer force with the ACL cut at 30° of flexion; the anterolateral ligament (ALL) and anterolateral capsule resisted 4%. For internal rotation, the superficial layer of the ITT significantly restrained internal rotation at higher flexion angles: 56% ± 20% and 56% ± 16% at 90° for the ACL-intact and ACL-deficient groups, respectively. The deep layer of the ITT restrained internal rotation at lower flexion angles, with 26% ± 9% and 33% ± 12% at 30° for the ACL-intact and ACL-deficient groups, respectively. The other anterolateral structures provided no significant contribution. During the pivot-shift test, the ITT provided 72% ± 14% of the restraint at 45° for th
Stephen JM, Halewood C, Kittl C, et al., 2016, Posteromedial Meniscocapsular Lesions Increase Tibiofemoral Joint Laxity With Anterior Cruciate Ligament Deficiency, and Their Repair Reduces Laxity, American Journal of Sports Medicine, Vol: 44, Pages: 400-408, ISSN: 0363-5465
Background:Injury to the posteromedial meniscocapsular junction has been identified after anterior cruciate ligament (ACL) rupture; however, there is a lack of objective evidence investigating how this affects knee kinematics or whether increased laxity can be restored by repair. Such injury is often overlooked at surgery, with possible compromise to results.Hypotheses:(1) Sectioning the posteromedial meniscocapsular junction in an ACL-deficient knee will result in increased anterior tibial translation and rotation. (2) Isolated ACL reconstruction in the presence of a posteromedial meniscocapsular junction lesion will not restore intact knee laxity. (3) Repair of the posteromedial capsule at the time of ACL reconstruction will reduce tibial translation and rotation to normal. (4) These changes will be clinically detectable.Study Design:Controlled laboratory study.Methods:Nine cadaveric knees were mounted in a test rig where knee kinematics were recorded from 0° to 100° of flexion by use of an optical tracking system. Measurements were recorded with the following loads: 90-N anterior-posterior tibial forces, 5-N·m internal-external tibial rotation torques, and combined 90-N anterior force and 5-N·m external rotation torque. Manual Rolimeter readings of anterior translation were taken at 30° and 90°. The knees were tested in the following conditions: intact, ACL deficient, ACL deficient and posteromedial meniscocapsular junction sectioned, ACL deficient and posteromedial meniscocapsular junction repaired, ACL patellar tendon reconstruction with posteromedial meniscocapsular junction repair, and ACL reconstructed and capsular lesion re-created. Statistical analysis used repeated-measures analysis of variance and post hoc paired t tests with Bonferroni correction.Results:Tibial anterior translation and external rotation were both significantly increased compared with the ACL-deficient knee after posterior meniscocapsular sectioning (P <
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, An automated framework for parametric analysis glenoid implant design, Bath Biomechanics Symposium 2015
Geraldes D, Hansen U, Amis A, 2015, Parametric analysis of glenoid implant design, International Society of Biomechanics 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
Kittl C, Schmeling A, Amis AA, 2015, The patellofemoral joint. Anatomy, biomechanics, and surgical interventions, ARTHROSKOPIE, Vol: 28, Pages: 172-180, ISSN: 0933-7946
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
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.
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
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
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
Hansen UN, sukjamsri, amis, 2015, Digital volumecorrelationandmicro-CT:Anin-vitrotechniquefor measuringfull-field interfacemicromotionaroundpolyethyleneimplants, 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
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