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  • Journal article
    Junaid S, Gregory T, Fetherston S, Emery R, Amis AA, Hansen Uet al., 2018,

    Cadaveric study validating in vitro monitoring techniques to measure the failure mechanism of glenoid implants against clinical CT

    , Journal of Orthopaedic Research, Vol: 36, Pages: 2524-2532, ISSN: 0736-0266

    Definite glenoid implant loosening is identifiable on radiographs, however, identifying early loosening still eludes clinicians. Methods to monitor glenoid loosening in vitro have not been validated to clinical imaging. This study investigates the correlation between in vitro measures and CT images. Ten cadaveric scapulae were implanted with a pegged glenoid implant and fatigue tested to failure. Each scapulae were cyclically loaded superiorly and CT scanned every 20,000 cycles until failure to monitor progressive radiolucent lines. Superior and inferior rim displacements were also measured. A finite element (FE) model of one scapula was used to analyze the interfacial stresses at the implant/cement and cement/bone interfaces. All ten implants failed inferiorly at the implant-cement interface, two also failed at the cement-bone interface inferiorly, and three showed superior failure. Failure occurred at of 80,966 ± 53,729 (mean ± SD) cycles. CT scans confirmed failure of the fixation, and in most cases, was observed either before or with visual failure. Significant correlations were found between inferior rim displacement, vertical head displacement and failure of the glenoid implant. The FE model showed peak tensile stresses inferiorly and high compressive stresses superiorly, corroborating experimental findings. In vitro monitoring methods correlated to failure progression in clinical CT images possibly indicating its capacity to detect loosening earlier for earlier clinical intervention if needed. Its use in detecting failure non-destructively for implant development and testing is also valuable. The study highlights failure at the implant-cement interface and early signs of failure are identifiable in CT images. © 2018 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of the Orthopaedic Research Society. J Orthop Res 9999:XX-XX, 2018.

  • Journal article
    Zhao S, Arnold M, Ma S, Abel R, Cobb J, Hansen U, Boughton ORet al., 2018,

    Standardising compression testing for measuring the stiffness of human bone: a systematic review

    , Bone and Joint Research, Vol: 7, Pages: 524-538, ISSN: 2046-3758

    Objectives: The ability to determine human bone stiffness is of clinical relevance in many fields, including bone quality assessment and orthopaedic prosthesis design. Stiffness can be measured using compression testing; an experimental technique commonly used to test bone specimens in vitro. This systematic review aims to determine how best to perform compression testing of human bone. Methods: A keyword search of all English language articles up until December 2017 of compression testing of bone was undertaken in Medline, Embase, PubMed and Scopus databases. Studies using bulk tissue, animal tissue, whole bone or testing techniques other than compression testing were excluded. Results: 4712 abstracts were retrieved with a total of 177 papers included in the analysis. 20 studies directly analysed the compression testing technique to improve the accuracy of the testing technique. Several influencing factors should be considered when testing bone samples in compression. These include the method of data analysis, specimen storage, specimen preparation, testing configuration and loading protocol. Conclusions: Compression testing is a widely used technique for measuring the stiffness of bone but there is a great deal of inter-study variation in experimental techniques across the literature. Based on best evidence from the literature, suggestions for bone compression testing are made in this review, though further studies are needed to help establish standardised bone testing techniques to increase the comparability and reliability of bone stiffness studies.

  • Journal article
    Lord BR, Colaco HB, Gupte CM, Wilson AJ, Amis AAet al., 2018,

    ACL graft compression: a method to allow reduced tunnel sizes in ACL reconstruction

    , Knee Surgery, Sports Traumatology, Arthroscopy, Vol: 26, Pages: 2430-2437, ISSN: 0942-2056

    PURPOSE: A common problem during ACL reconstruction is asymmetry of proximal-distal graft diameter leading to tunnel upsizing and graft-tunnel mismatch. Compression downsizing provides a graft of uniform size, allowing easy passage into a smaller tunnel. The purpose of this study was to quantify the graft compression technique and its effects on graft biomechanics and stability. It was hypothesised that compression downsizing would significantly reduce cross-sectional area (CSA); that no significant changes in graft biomechanics would occur; graft fixation stability would be improved. METHOD: Sixty-eight non-irradiated peroneus longus (PL) tendons were investigated. Twenty were halved and paired into ten four-strand grafts, 20 strands were compressed by 0.5-1 mm diameter and changes in CSA recorded using an alginate mould technique. The following properties were compared with 20 control strands: cyclic strain when loaded 70-220 N for 1000 cycles; stiffness; ultimate tensile load and stress; Young's modulus. 24 PL tendons were quadrupled into grafts, 12 were compressed and all 24 were submerged in Ringer's solution at 37 °C and the CSA recorded over 12 h. Twelve compressed and 12 control quadrupled grafts were mounted in porcine femurs, placed in Ringer's solution for 12 h at 37 °C and graft displacement at the bone tunnel aperture recorded under cyclic loading. RESULTS: Mean decreases in CSA of 31% under a stress of 471 kPa and 21% under a stress of 447 kPa were observed for doubled and quadrupled grafts, respectively. Compressed grafts re-expanded by 19% over 12 h compared to 2% for controls. No significant differences were observed between compressed and control grafts in the biomechanical properties and graft stability; mean cyclic displacements were 0.3 mm for both groups. CONCLUSIONS: No detrimental biomechanical effects of graft compression on allograft PL tendons were observed. Following compression, t

  • Journal article
    Heilpern G, Stephen J, Ball S, Amis A, Williams Aet al., 2018,

    It is safe and effective to use all inside meniscal repair devices for posteromedial meniscal 'ramp' lesions

    , Knee Surgery, Sports Traumatology, Arthroscopy, Vol: 26, Pages: 2310-2316, ISSN: 0942-2056

    PURPOSE: Recently, it has been recognized that meniscocapsular ('ramp') lesions of the posterior one-third of the medial meniscus frequently occur during injuries causing ACL rupture, and that these lesions are easily missed at arthroscopy. Furthermore, it is clear that these lesions are biomechanically significant, adding to the deficits caused by ACL rupture, and that their repair can reverse this. The efficacy of an all inside repair technique has been questioned by some authors and by those who advocate a suture shuttle technique via an accessory posteromedial portal. The use of Ultra FastFix and FastFix 360 meniscal repair devices to repair posteromedial meniscocapsular separations was investigated in terms of safe deployment and the effectiveness. Author: Affiliations: Journal instruction requires a country for affiliations; however, these are missing in affiliations [1, 2]. Please verify if the provided country is correct and amend if necessary. METHODS: Twenty cadaveric fresh frozen knees were used-ten in each of two groups. A ramp lesion was created using a Beaver knife. The lesion was then repaired with either 4 Ultra FastFix (Smith and Nephew) or 4 FastFix 360 (Smith and Nephew) meniscal repair devices. The knees were put through a standardized loading cycle consisting of 10 Lachman's tests and ten maximum loading manual anterior drawer tests at 90° of flexion. Each knee was then flexed and extended fully ten times. The specimens were sectioned just proximal to the menisci and each suture anchor identified and its position recorded and photographed. Author: Author details: Kindly check and confirm whether the corresponding author mail id is correctly identified and amend if necessary. RESULTS: In the Ultra FastFix group, a single anchor was found to be in an intra-articular position-a failure rate of 2.5%. In the FastFix 360 group, 5 anchors failed-a 12.5% failure rate. In all cases, the anchors were attached to their suture and so not truly loose wit

  • 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 article
    Boughton OR, Ma S, Zhao S, Arnold M, Lewis A, Hansen U, Cobb J, Giuliani F, Abel Ret al., 2018,

    Measuring bone stiffness using spherical indentation

    , PLoS ONE, Vol: 13, ISSN: 1932-6203

    ObjectivesBone material properties are a major determinant of bone health in older age, both in terms of fracture risk and implant fixation, in orthopaedics and dentistry. Bone is an anisotropic and hierarchical material so its measured material properties depend upon the scale of metric used. The scale used should reflect the clinical problem, whether it is fracture risk, a whole bone problem, or implant stability, at the millimetre-scale. Indentation, an engineering technique involving pressing a hard-tipped material into another material with a known force, may be able to assess bone stiffness at the millimetre-scale (the apparent elastic modulus). We aimed to investigate whether spherical-tip indentation could reliably measure the apparent elastic modulus of human cortical bone.Materials and methodsCortical bone samples were retrieved from the femoral necks of nineteen patients undergoing total hip replacement surgery (10 females, 9 males, mean age: 69 years). The samples underwent indentation using a 1.5 mm diameter, ruby, spherical indenter tip, with sixty indentations per patient sample, across six locations on the bone surfaces, with ten repeated indentations at each of the six locations. The samples then underwent mechanical compression testing. The repeatability of indentation measurements of elastic modulus was assessed using the co-efficient of repeatability and the correlation between the bone elastic modulus measured by indentation and compression testing was analysed by least-squares regression.ResultsIn total, 1140 indentations in total were performed. Indentation was found to be repeatable for indentations performed at the same locations on the bone samples with a mean co-efficient of repeatability of 0.4 GigaPascals (GPa), confidence interval (C.I): 0.33–0.42 GPa. There was variation in the indentation modulus results between different locations on the bone samples (mean co-efficient of repeatability: 3.1 GPa, C.I: 2.2–3.90 GPa). No cle

  • Journal article
    Marsland D, Stephen JM, Calder T, Amis AA, Calder JDFet al., 2018,

    Strength of Interference Screw Fixation to Cuboid vs Pulvertaft Weave to Peroneus Brevis for Tibialis Posterior Tendon Transfer for Foot Drop.

    , Foot and Ankle International, Vol: 39, Pages: 858-864, ISSN: 1071-1007

    BACKGROUND: Tibialis posterior (TP) tendon transfer is an effective treatment for foot drop. Currently, standard practice is to immobilize the ankle in a cast for 6 weeks nonweightbearing, risking postoperative stiffness. To assess whether early active dorsiflexion and protected weightbearing could be safe, the current study assessed tendon displacement under cyclic loading and load to failure, comparing the Pulvertaft weave (PW) to interference screw fixation (ISF) in a cadaveric foot model. METHODS: Twenty-four cadaveric ankles had TP tendon transfer performed, 12 with the PW technique and 12 with ISF to the cuboid. The TP tendon was cycled 1000 times at 50 to 150 N and then loaded to failure in a materials testing machine. Tendon displacement at the insertion site was recorded every 100 cycles. An independent t test and 2-way analysis of variance were performed to compare techniques, with a significance level of P < .05. RESULTS: Mean tendon displacement was similar in the PW group (2.9 ± 2.5 mm [mean ± SD]) compared with the ISF group (2.4 ± 1.1 mm), P = .35. One specimen in the ISF group failed early by tendon pullout. None of the PW group failed early, although displacement of 8.9 mm was observed in 1 specimen. Mean load to failure was 419.1 ± 82.6 N in the PW group in comparison to 499.4 ± 109.6 N in the ISF group, P = .06. CONCLUSION: For TP tendon transfer, ISF and PW techniques were comparable, with no differences in tendon displacement after cyclical loading or load to failure. Greater variability was observed in the PW group, suggesting it may be a less reliable technique. CLINICAL RELEVANCE: The results indicate that early active dorsiflexion and protected weightbearing may be safe for clinical evaluation, with potential benefits for the patient compared with cast immobilization.

  • Journal article
    Willmott H, Al-Wattar Z, Halewood C, Dunning M, Amis Aet al., 2018,

    Evaluation of different shape-memory staple configurations against crossed screws for first metatarsophalangeal joint arthrodesis: A biomechanical study

    , Foot and Ankle Surgery, Vol: 24, Pages: 259-263, ISSN: 1268-7731

    BACKGROUND: The first metatarsophalangeal joint may be fused in order to treat arthritis or instability. The use of shape-memory staples for fixation is well recognised, but little work has been done into the optimal configuration of staples. METHODS: The structural behaviour of first metatarsophalangeal joint (MTPJ) arthrodeses using shape-memory staples or crossed screws was studied using cadaveric porcine joints. Five fixation configurations were tested: single vertical or horizontal staple, paired staples in dorsal-medial configuration (0-90° to the sagittal plane), paired staples in oblique orthogonal configuration (45-135°); or two crossed screws. Specimens were loaded in cyclical dorsiflexion for 1000 cycles. Plantar gapping and shearing were measured. Specimens were then loaded to failure. RESULTS: Cyclic testing caused more shear in the 45-135° staples than the crossed screws (1.0mm±0.5mm compared to 0.14mm±0.4mm, p<0.01). No significant difference was found in plantar gap formation. Single vertical and horizontal single staples failed at 15N and 19. CONCLUSIONS: N, respectively. Paired 0-90° staples failed at 43N±9N, significantly lower than the 45-135° staples (141N±25N; p<0.001) and crossed screws (180N±67N; p<0.001). There was no significant difference between the 45-135° staples and crossed screws. Screws failed by sudden cortical fracture; staples displayed gradual pull-out and shearing. First MTPJ arthrodeses fixed with single staples are not recommended. Arthrodeses fixed with staples at 0-90° to the sagittal plane were significantly less strong than two crossed screws. However, positioning oblique staples at 45-135° significantly improved stability, creating a construct as strong as, crossed screws. None of the constructs was strong enough for immediate weight bearing.

  • Journal article
    Kanca Y, Milner P, Dini D, Amis Aet al., 2018,

    Tribological evaluation of biomedical polycarbonate urethanes against articular cartilage

    , Journal of the Mechanical Behavior of Biomedical Materials, Vol: 82, Pages: 394-402, ISSN: 1751-6161

    This research investigated the in-vitro wear and friction performance of polycarbonate urethane (PCU) 80A as they interact with articular cartilage, using a customised multidirectional pin-on-plate tester. Condyles were articulated against PCU 80A discs (Bionate® I and Bionate® II) (configuration 1) and the results arising from these tests were compared to those recorded during the sliding of PCU pins against cartilage plates (configuration 2). Configuration 1 produced steadily increasing coefficient of friction (COF) (up to 0.64 ± 0.05) and had the same trend as the cartilage–on–stainless steel articulation (positive control). When synovial fluid rather than bovine calf serum was used as lubricant, average COF significantly decreased from 0.50 ± 0.02–0.38 ± 0.06 for condyle–on–Bionate® I (80AI) and from 0.41 ± 0.02–0.24 ± 0.04 for condyle–on–Bionate® II (80AII) test configurations (p < 0.05). After 15 h testing, the cartilage–on–cartilage articulation (negative control) tests showed no cartilage degeneration. However, different levels of cartilage volume loss were found on the condyles from the positive control (12.5 ± 4.2 mm3) and the PCUs (20.1 ± 3.6 mm3 for 80 AI and 19.0 ± 2.3 mm3 for 80AII) (p > 0.05). A good correlation (R2 =0.84) was found between the levels of average COF and the volume of cartilage lost during testing; increasing wear was found at higher levels of COF. Configuration 2 showed low and constant COF values (0.04 ± 0.01), which were closer to the negative control (0.03 ± 0.01) and significantly lower than configuration 1 (p < 0.05). The investigation showed that PCU is a good candidate for use in hemiarthroplasty components, where only one of the two articulating surfaces is replaced, as long as the synthetic material is implanted in a region where migrating cartilage contact is achieved. Bio

  • Journal article
    Halewood C, Athwal KK, Amis A, 2018,

    Pre-clinical assessment of total knee replacement anterior-posterior constraint

    , Journal of Biomechanics, Vol: 73, Pages: 153-160, ISSN: 0021-9290

    Pre-clinical, bench-top assessment of Total Knee Replacements (TKR) can provide information about the inherent constraint provided by a TKR, which does not depend on the condition of the patient undergoing the arthroplasty. However little guidance is given by the ASTM standard on test configurations such as medial-lateral (M:L) loading distribution, flexion angle or restriction of secondary motions. Using a purpose built rig for a materials testing machine, four TKRs currently in widespread clinical use, including medial-pivot and symmetrical condyle types, were tested for anterior-posterior translational constraint. Compressive joint loads from 710 to 2000 N, and a range of medial-lateral (M:L) load distributions, from 70:30% to 30:70% M:L, were applied at different flexion angles with secondary motions unconstrained. It was found that TKA constraint was significantly less at 60 and 90° flexion than at 0°, whilst increasing the compressive joint load increased the force required to translate the tibia to limits of AP constraint at all flexion angles tested. Additionally when M:L load distribution was shifted medially, a coupled internal rotation was observed with anterior translation and external rotation with posterior translation. This paper includes some recommendations for future development of pre-clinical testing methods.

  • 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
    Musahl V, Getgood A, Neyret P, Claes S, Burnham JM, Batailler C, Sonnery-Cottet B, Williams A, Amis A, Zaffagnini S, Karlsson Jet al., 2018,

    Contributions of the anterolateral complex and the anterolateral ligament to rotatory knee stability in the setting of ACL Injury: a roundtable discussion

    , Knee Surgery, Sports Traumatology, Arthroscopy, Vol: 25, Pages: 997-1008, ISSN: 0942-2056

    Persistent rotatory knee laxity is increasingly recognized as a common finding after anterior cruciate ligament (ACL) reconstruction. While the reasons behind rotator knee laxity are multifactorial, the impact of the anterolateral knee structures is significant. As such, substantial focus has been directed toward better understanding these structures, including their anatomy, biomechanics, in vivo function, injury patterns, and the ideal procedures with which to address any rotatory knee laxity that results from damage to these structures. However, the complexity of lateral knee anatomy, varying dissection techniques, differing specimen preparation methods, inconsistent sectioning techniques in biomechanical studies, and confusing terminology have led to discrepancies in published studies on the topic. Furthermore, anatomical and functional descriptions have varied widely. As such, we have assembled a panel of expert surgeons and scientists to discuss the roles of the anterolateral structures in rotatory knee laxity, the healing potential of these structures, the most appropriate procedures to address rotatory knee laxity, and the indications for these procedures. In this round table discussion, KSSTA Editor-in-Chief Professor Jón Karlsson poses a variety of relevant and timely questions, and experts from around the world provide answers based on their personal experiences, scientific study, and interpretations of the literature. Level of evidence V.

  • 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
  • Book chapter
    Inderhaug E, Amis AA, 2018,

    Femoral Tunnel Placement to Restore Normal Knee Laxity after Anterior Cruciate Ligament Reconstruction

    , The Anterior Cruciate Ligament: Reconstruction and Basic Science: Second Edition, Pages: 188-193.e1, ISBN: 9780323389624
  • Journal article
    Williams A, Amis A, Zaffagnini S, Karlsson Jet al., 2018,

    Erratum to: Contributions of the anterolateral complex and the anterolateral ligament to rotatory knee stability in the setting of ACL Injury: a roundtable discussion (Knee Surgery, Sports Traumatology, Arthroscopy, (2017), 25, 4, (997-1008), 10.1007/s00167-017-4436-7)

    , Knee Surgery, Sports Traumatology, Arthroscopy, Vol: 26, Pages: 353-353, ISSN: 0942-2056

    © 2016, European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA). In the original article, one of the co-authors’ name has been published incorrectly. The correct name should be Jeremy M. Burnham. The original article has been updated accordingly.

  • 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
    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

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