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  • Journal article
    Iranpour F, Merican AM, Rodriguez y Baena F, Cobb JP, Amis AAet al., 2010,

    Patellofemoral Joint Kinematics: The Circular Path of the Patella around the Trochlear Axis

    , J Orthop Res, Vol: 28, Pages: 589-594, ISSN: 0736-0266

    Differing descriptions of patellar motion relative to the femur have resulted from previous studies. We hypothesized that patellar kinematics would correlate to the trochlear geometry and that differing descriptions could be reconciled by accounting for differing alignments of measurement axes. Seven normal fresh-frozen knees were CT scanned, and their kinematics with quadriceps loading was measured by an optical tracker system. Kinematics was calculated in relation to the femoral epicondylar, anatomic, and mechanical axes. A novel trochlear axis was defined, between the centers of spheres best fitted to the medial and lateral trochlear articular surfaces. The path of the center of the patella was circular and uniplanar (root-mean-square error 0.3 mm) above 16 +/- 3 degrees (mean +/- SD) knee flexion. In the coronal plane, this circle was aligned 6 +/- 2 degrees from the femoral anatomical axis, close to the mechanical axis alignment. It was 91 +/- 3 degrees from the epicondylar axis, and 88 +/- 3 degrees from the trochlear axis. In the transverse plane it was 91 +/- 3 degrees and 88 +/- 3 degrees from the epicondylar and trochlear axes, respectively. Manipulation of the data to different axis alignments showed that differing previously published data could be reconciled. The circular path of patellar motion around the trochlea, aligned with the mechanical axis of the leg, is easily visualized and understood. (C) 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:589-594, 2010

  • Journal article
    Gregory T, Hansen U, Taillieu F, Baring T, Brassart N, Mutchler C, Amis A, Augereau B, Emery Ret 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
  • Journal article
    Merican AM, Sanghavi S, Iranpour F, Amis AAet al., 2009,

    The structural properties of the lateral retinaculum and capsular complex of the knee

    , JOURNAL OF BIOMECHANICS, Vol: 42, Pages: 2323-2329, ISSN: 0021-9290
  • Conference paper
    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
  • Journal article
    Chia S-L, Merican AM, Devadasan B, Strachan RK, Amis AAet al., 2009,

    Radiographic features predictive of patellar maltracking during total knee arthroplasty

    , KNEE SURGERY SPORTS TRAUMATOLOGY ARTHROSCOPY, Vol: 17, Pages: 1217-1224, ISSN: 0942-2056
  • Journal article
    Ghosh KM, Merican AM, Iranpour F, Deehan DJ, Amis AAet al., 2009,

    The effect of overstuffing the patellofemoral joint on the extensor retinaculum of the knee

    , KNEE SURGERY SPORTS TRAUMATOLOGY ARTHROSCOPY, Vol: 17, Pages: 1211-1216, ISSN: 0942-2056
  • Conference paper
    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.

  • Journal article
    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.

  • Journal article
    Strachan RK, Merican AM, Devadasan B, Maheshwari R, Amis AAet al., 2009,

    A Technique of Staged Lateral Release to Correct Patellar Tracking in Total Knee Arthroplasty

    , JOURNAL OF ARTHROPLASTY, Vol: 24, Pages: 735-742, ISSN: 0883-5403
  • Journal article
    Smith CD, Masouros S, Hill AM, Amis AA, Bull AMJet al., 2009,

    A biomechanical basis for tears of the human acetabular labrum

    , BRITISH JOURNAL OF SPORTS MEDICINE, Vol: 43, Pages: 574-578, ISSN: 0306-3674
  • Journal article
    Merican AM, Amis AA, 2009,

    Iliotibial band tension affects patellofemoral and tibiofemoral kinematics

    , JOURNAL OF BIOMECHANICS, Vol: 42, Pages: 1539-1546, ISSN: 0021-9290
  • Journal article
    Ghosh KM, Merican AM, Iranpour-Boroujeni F, Deehan DJ, Amis AAet al., 2009,

    Length Change Patterns of the Extensor Retinaculum and the Effect of Total Knee Replacement

    , JOURNAL OF ORTHOPAEDIC RESEARCH, Vol: 27, Pages: 865-870, ISSN: 0736-0266
  • Journal article
    Southgate DF, Hill AM, Alexander S, Wallace AL, Hansen UN, Bull AMet 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.

  • Journal article
    Sinnett-Jones PE, Browne M, Moffat AJ, Jeffers JRT, Saffari N, Buffiere J-Y, Sinclair Iet al., 2009,

    Crack initiation processes in acrylic bone cement

    , JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A, Vol: 89A, Pages: 1088-1097, ISSN: 1549-3296
  • Journal article
    Apsingi S, Bull AMJ, Deehan DJ, Amis AAet al., 2009,

    Review: femoral tunnel placement for PCL reconstruction in relation to the PCL fibre bundle attachments

    , KNEE SURGERY SPORTS TRAUMATOLOGY ARTHROSCOPY, Vol: 17, Pages: 652-659, ISSN: 0942-2056
  • Journal article
    Smith CD, Masouros SD, Hill AM, Wallace AL, Amis AA, Bull AMJet al., 2009,

    The Compressive Behavior of the Human Glenoid Labrum May Explain the Common Patterns of SLAP Lesions

    , ARTHROSCOPY-THE JOURNAL OF ARTHROSCOPIC AND RELATED SURGERY, Vol: 25, Pages: 504-509, ISSN: 0749-8063
  • Journal article
    Apsingi S, Nguyen T, Bull AMJ, Unwin A, Deehan DJ, Amis AAet al., 2009,

    A comparison of modified Larson and 'anatomic' posterolateral corner reconstructions in knees with combined PCL and posterolateral corner deficiency

    , KNEE SURGERY SPORTS TRAUMATOLOGY ARTHROSCOPY, Vol: 17, Pages: 305-312, ISSN: 0942-2056
  • Journal article
    Merican AM, Ghosh KM, Deehan DJ, Amis AAet al., 2009,

    The Transpatellar Approach for the Knee in the Laboratory

    , JOURNAL OF ORTHOPAEDIC RESEARCH, Vol: 27, Pages: 330-334, ISSN: 0736-0266
  • Journal article
    Merican AM, Kondo E, Amis AA, 2009,

    The effect on patellofemoral joint stability of selective cutting of lateral retinacular and capsular structures

    , JOURNAL OF BIOMECHANICS, Vol: 42, Pages: 291-296, ISSN: 0021-9290
  • Conference paper
    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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