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  • 1.
    Goldvasser, Dov
    et al.
    Harris Orthopaedic Laboratory, Massachusetts General Hospital, Boston MA, United States .
    Hansen, Viktor J.
    Harris Orthopaedic Laboratory, Massachusetts General Hospital, Boston MA, United States .
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Zeleznik, Michael P.
    University of Utah, Salt Lake City, UT, USA.
    Olivecrona, Henrik
    Karolinska Institute.
    Bragdon, Charles R.
    Harris Orthopaedic Laboratory, Massachusetts General Hospital, Boston MA, United States .
    Weidenhielm, Lars
    Karolinska Institute.
    Malchau, Henrik
    Harris Orthopaedic Laboratory, Massachusetts General Hospital, Boston MA, United States .
    In vivo and ex vivo measurement of polyethylene wear in total hip arthroplasty2014In: Acta Orthopaedica, ISSN 1745-3674, E-ISSN 1745-3682, Vol. 85, no 3, p. 271-275Article in journal (Refereed)
    Abstract [en]

    Background - Determination of the amount of wear in a polyethylene liner following total hip arthroplasty (THA) is important for both the clinical care of individual patients and the development of new types of liners. Patients and methods - We measured in vivo wear of the polyethylene liner using computed tomography (CT) (obtained in the course of regular clinical care) and compared it to coordinate-measuring machine (CMM) readings. Also, changes in liner thickness of the same retrieved polyethylene liner were measured using a micrometer, and were compared to CT and CMM measurements. The distance between the centers of the acetabular cup and femoral head component was measured in 3D CT, using a semi-automatic analysis method. CMM readings were performed on each acetabular liner and data were analyzed using 3D computer-aided design software. Micrometer readings compared the thickest and thinnest regions of the liner. We analyzed 10 THA CTs and retrievals that met minimal requirements for CT slice thickness and explanted cup condition. Results - For the 10 cups, the mean difference between the CT readings and the CMM readings was -0.09 (-0.38 to 0.20) mm. This difference was not statistically significant (p = 0.6). Between CT and micrometer, the mean difference was 0.11 (-0.33 to 0.55) mm. This difference was not statistically significant (p = 0.6). Interpretation - Our results show that CT imaging is ready to be used as a tool in clinical wear measurement of polyethylene liners used in THA.

  • 2.
    Jedenmalm, Anneli
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. Lund University, Sweden.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Green, Douglas D.
    Loma Linda University, Orthopaedic Research Center.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Clarke, Ian C.
    Loma Linda University, Orthopaedic Research Center.
    Stark, Andreas
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Zeleznik, Michael P.
    Saya Systems Inc., Salt Lake City, UT, USA.
    Olivecrona, Henrik
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Validation of a 3D CT method for measurement of linear wear of acetabular cups: A hip simulator study2011In: Acta Orthopaedica, ISSN 1745-3674, E-ISSN 1745-3682, Vol. 82, no 1, p. 35-41Article in journal (Refereed)
    Abstract [en]

    Material and methods Ultra-high molecular weight polyethylene cups with a titanium mesh molded on the outside were subjected to wear using a hip simulator. Before and after wear, they were (1) imaged with a CT scanner using a phantom model device, (2) measured using a coordinate measurement machine (CMM), and (3) weighed. CMM was used as the reference method for measurement of femoral head penetration into the cup and for comparison with CT, and gravimetric measurements were used as a reference for both CT and CMM. Femoral head penetration and wear vector angle were studied. The head diameters were also measured with both CMM and CT. The repeatability of the method proposed was evaluated with two repeated measurements using different positions of the phantom in the CT scanner. Results The accuracy of the 3D CT method for evaluation of linear wear was 0.51 mm and the repeatability was 0.39 mm. Repeatability for wear vector angle was 17 degrees A degrees. Interpretation This study of metal-meshed hip-simulated acetabular cups shows that CT has the capacity for reliable measurement of linear wear of acetabular cups at a clinically relevant level of accuracy.

  • 3.
    Jedenmalm, Anneli
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Noz, Marilyn
    Green, Douglas
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Clarke, Ian
    Stark, Andreas
    Olivecrona, Henrik
    Validation of a 3D CT method for measuring linear and -volumetric wear of acetabular cups - a hip simulator studyIn: Acta Orthopaedica, ISSN 1745-3674, E-ISSN 1745-3682Article in journal (Other academic)
  • 4.
    Jedenmalm, Anneli
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Noz, Marilyn E.
    Department of Radiology, New York University School of Medicine, New York.
    Olivecrona, Henrik
    Department of Hand Surgery, Södersjukhuset, Stockholm.
    Olivecrona, Lofta
    Department of Radiology, Karolinska University Hospital Solna, Stockholm.
    Stark, Andre
    Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm.
    A new approach for assessment of wear in metal-backed acetabular cups using computed tomography: a phantom study with retrievals2008In: Acta Orthopaedica, ISSN 1745-3674, E-ISSN 1745-3682, Vol. 79, no 2, p. 218-224Article in journal (Refereed)
    Abstract [en]

    Background and purpose Polyethylene wear is an important cause of aseptic loosening in hip arthroplasty. Detection of significant wear usually happens late on, since available diagnostic techniques are either not sensitive enough or too complicated and expensive for routine use. This study evaluates a new approach for measurement of linear wear of metal-backed acetabular cups using CT as the intended clinically feasible method.

    Material and methods 8 retrieved uncemented metal-backed acetabular cups were scanned twice ex vivo using CT. The linear penetration depth of the femoral head into the cup was measured in the CT volumes using dedicated software. Landmark points were placed on the CT images of cup and head, and also on a reference plane in order to calculate the wear vector magnitude and angle to one of the axes. A coordinate-measuring machine was used to test the accuracy of the proposed CT method. For this purpose, the head diameters were also measured by both methods.

    Results Accuracy of the CT method for linear wear measurements was 0.6 nm and wear vector angle was 27 degrees. No systematic difference was found between CT scans.

    Interpretation This study on explanted acetabular cups shows that CT is capable of reliable measurement of linear wear in acetabular cups at a clinically relevant level of accuracy. It was also possible to use the method for assessment of direction of wear.

  • 5. Olczak, Jakub
    et al.
    Fahlberg, Niklas
    Maki, Atsuto
    KTH, School of Computer Science and Communication (CSC), Robotics, perception and learning, RPL.
    Razavian, Ali Sharif
    KTH, School of Computer Science and Communication (CSC), Robotics, perception and learning, RPL. Danderyd Hosp, Karolinska Inst, Sweden.
    Jilert, Anthony
    Stark, Andre
    Skoldenberg, Olof
    Gordon, Max
    Artificial intelligence for analyzing orthopedic trauma radiographs Deep learning algorithms-are they on par with humans for diagnosing fractures?2017In: Acta Orthopaedica, ISSN 1745-3674, E-ISSN 1745-3682, Vol. 88, no 6, p. 581-586Article in journal (Refereed)
    Abstract [en]

    Background and purpose - Recent advances in artificial intelligence (deep learning) have shown remarkable performance in classifying non-medical images, and the technology is believed to be the next technological revolution. So far it has never been applied in an orthopedic setting, and in this study we sought to determine the feasibility of using deep learning for skeletal radiographs. Methods - We extracted 256,000 wrist, hand, and ankle radiographs from Danderyd's Hospital and identified 4 classes: fracture, laterality, body part, and exam view. We then selected 5 openly available deep learning networks that were adapted for these images. The most accurate network was benchmarked against a gold standard for fractures. We furthermore compared the network's performance with 2 senior orthopedic surgeons who reviewed images at the same resolution as the network. Results - All networks exhibited an accuracy of at least 90% when identifying laterality, body part, and exam view. The final accuracy for fractures was estimated at 83% for the best performing network. The network performed similarly to senior orthopedic surgeons when presented with images at the same resolution as the network. The 2 reviewer Cohen's kappa under these conditions was 0.76. Interpretation - This study supports the use for orthopedic radiographs of artificial intelligence, which can perform at a human level. While current implementation lacks important features that surgeons require, e.g. risk of dislocation, classifications, measurements, and combining multiple exam views, these problems have technical solutions that are waiting to be implemented for orthopedics.

  • 6.
    Olivecrona, Henrik
    et al.
    Department of Hand Surgery, Södersjukhuset, Stockholm.
    Olivecrona, Lotta
    Karolinska Institutet, Department of Clinical Science, Intervention and Technology, Division of Radiology.
    Weidenhielm, Lars
    Karolinska University Hospital Solna, Department of Orthopedics.
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Kardos, Jocelyn
    New York University, Department of Radiology.
    Maguire, Gerald Q. Jr.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Zeleznik, Michael P.
    Saya Systems Inc., Salt Lake City, UT, USA.
    Aspelin, Peter
    Karolinska Institutet, Department of Clinical Science, Intervention and Technology, Division of Radiology.
    A new technique for diagnosis of acetabular cup loosening using computed tomography - Preliminary experience in 10 patients2008In: Acta Orthopaedica, ISSN 1745-3674, E-ISSN 1745-3682, Vol. 79, no 3, p. 346-353Article in journal (Refereed)
    Abstract [en]

    Background and purpose: Considerable migration of the acetabular cup is required for diagnosis of loosening by conventional radiography. We have developed a new clinically applicable method for assessment of cup loosening using computed tomography (CT). Patients and methods 10 patients scheduled for revision hip replacement due to suspected wear or loosening were scanned twice with CT under torsion loading of the prosthesis. Two independent examiners assessed each patient with respect to motion of the acetabular cup relative to the pelvis using CT volume registration. The CT measurements were compared to findings at revision surgery. Results The method was applicable in 8 of the 10 patients. 1 patient had a severe tremor. In 1 patient, surgery revealed that the hip was ankylotic due to massive ectopic bone formation. This left 8 patients that could be evaluated. 4 cups were loose at surgery, and 3 of these cups could be seen to be mobile by CT. 4 cups that were stable on revision were accurately diagnosed as not being mobile by CT. Movements of less than 1 millimeter between bone and prosthesis could not be distinguished from errors in CT acquisition and volume registration. There was good agreement between the two observers. Interpretation Movement of loose acetabular cups during torsion loading could be detected using CT volume registration. It was sensitive to cup movement in 3 out of 4 cases of loose cups. The method was specific and yielded no false positive results.

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