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  • 1.
    Brodén, Cyrus
    et al.
    Department of Molecular Medicine and Surgery, Karolinska Institutet.
    Olivecrona, Henrik
    Department of Molecular Medicine and Surgery, Karolinska Institutet.
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Zeleznik, Michael P.
    School of Computing, College of Engineering, University of Utah.
    Sköldenberg, Olof
    Department of Clinical Sciences, Danderyd Hospital, Karolinska Institutet.
    Accuracy and Precision of Three-Dimensional Low Dose CT Compared to Standard RSA in Acetabular Cups: An Experimental Study2016In: BioMed Research International, ISSN 2314-6133, E-ISSN 2314-6141, article id 5909741Article in journal (Refereed)
    Abstract [en]

    Background and Purpose. The gold standard for detection of implant wear and migration is currently radiostereometry (RSA). The purpose of this study is to compare a three-dimensional computed tomography technique (3D CT) to standard RSA as an alternative technique for measuring migration of acetabular cups in total hip arthroplasty.

    Materials and Methods. With tantalum beads, we marked one cemented and one uncemented cup and mounted these on a similarly marked pelvic model. A comparison was made between 3D CT and standard RSA for measuring migration. Twelve repeated stereoradiographs and CT scans with double examinations in each position and gradual migration of the implants were made. Precision and accuracy of the 3D CT were calculated.

    Results. The accuracy of the 3D CT ranged between 0.07 and 0.32 mm for translations and 0.21 and 0.82° for rotation. The precision ranged between 0.01 and 0.09 mm for translations and 0.06 and 0.29° for rotations, respectively. For standard RSA, the precision ranged between 0.04 and 0.09 mm for translations and 0.08 and 0.32° for rotations, respectively. There was no significant difference in precision between 3D CT and standard RSA. The effective radiation dose of the 3D CT method, comparable to RSA, was estimated to be 0.33 mSv.

    Interpretation. Low dose 3D CT is a comparable method to standard RSA in an experimental setting.

  • 2.
    Engström, Pähr
    et al.
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Bartonek, Åsa
    Karolinska Institutet, Dept. of Women's and Child's Health.
    Tedroff, Kristina
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Orefelt, Christina
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Haglund-Åkerlind, Yvonne
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Gutierrez-Farewik, Elena
    Department of Women’s and Children’s Health. Karolinska University Hospital, Sweden.
    Botulinum toxin A does not improve cast treatment for idiopathic toe-walking - a randomized controlled trial2013In: Journal of Bone and Joint Surgery. American volume, ISSN 0021-9355, E-ISSN 1535-1386, Vol. 95, no 5, p. 400-407Article in journal (Refereed)
    Abstract [en]

    Background: There are many treatments for idiopathic toe-walking, including casts with or without injection of botulinum toxin A. Combined treatment with casts and botulinum toxin A has become more common even though there have been few studies of its efficacy and safety problems. Our aims were to conduct a randomized controlled trial to test the hypotheses that combined treatment with casts and botulinum toxin A is more effective than casts alone in reducing toewalking by patients five to fifteen years of age, and that the treatment effect correlates with the extent of coexisting neuropsychiatric problems. Methods: All patients who had been consecutively admitted to the pediatric orthopaedics department of our institution because of idiopathic toe-walking between November 2005 and April 2010 were considered for inclusion in the study. Forty-seven children constituted the study population. The children were randomized to undergo four weeks of treatment with below-the-knee casts either as the sole intervention or to undergo the cast treatment one to two weeks after receiving injections of botulinum toxin A into the calves. Before treatment and three and twelve months after cast removal, all children underwent three-dimensional (3-D) gait analysis. The severity of the idiopathic toe-walking was classified on the basis of the gait analysis, and the parents rated the time that their child spent on his/her toes during barefoot walking. Passive hip, knee, and ankle motion as well as ankle dorsiflexor strength were measured. Before treatment, all children were evaluated with a screening questionnaire for neuropsychiatric problems. Results: No differences were found in any outcome parameter between the groups before treatment or at three or twelve months after cast removal. Several gait-analysis parameters, passive ankle motion, and ankle dorsiflexor strength were improved at both three and twelve months in both groups, even though many children still demonstrated some degree of toe-walking. The treatment outcomes were not correlated with coexisting neuropsychiatric problems. Conclusion: Adding botulinum toxin-A injections prior to cast treatment for idiopathic toe-walking does not improve the outcome of cast-only treatment. Level of Evidence: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

  • 3.
    Engström, Pähr
    et al.
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics. KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Bartonek, Åsa
    Karolinska Institutet, Dept. of Women's and Child's Health.
    Tedroff, Kristina
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Orefelt, Christina
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Haglund-Åkerlind, Yvonne
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Does Botulinum toxin A improve the walking pattern in children with idiopathic toe-walking?2010In: Journal of Children's Orthopaedics, ISSN 1863-2521, Vol. 4, no 4, p. 301-308Article in journal (Refereed)
    Abstract [en]

    Background: Numerous recommendations have been made for treating idiopathic toe-walking (ITW), but the treatment results have been questioned. The purpose of this study was to investigate whether botulinum toxin A (BTX) improves the walking pattern in ITW as examined with 3-D gait analysis. Participants and methods: A consecutive series of 15 children (aged 5-13 years) were enrolled in the study. The children underwent a 3-D gait analysis prior to treatment with a total of 6 units/kg bodyweight Botox® in the calf muscles and an exercise program. The gait analysis was repeated 3 weeks and 3, 6, and 12 months after treatment. A classification of toe-walking severity was made before treatment and after 12 months. The parents rated the perceived amount of toe-walking prior to treatment and 6 and 12 months after treatment. Results: Eleven children completed the 12-month follow-up. The gait analysis results displayed a significant improvement, indicating decreased plantarflexion angle at initial contact and during swing phase and increased dorsiflexion angle during midstance at all post-treatment testing instances. According to the parents' perception of toe-walking, 3/11 children followed for 12 months had ceased toe-walking completely, 4/11 decreased toe-walking, and 4/11 continued toe-walking. After 6-12 months, the toe-walking severity classification improved in 9 of the 14 children for whom data could be assessed. Conclusions: A single injection of BTX in combination with an exercise program can improve the walking pattern in children with ITW seen at gait analysis, but the obvious goal of ceasing toe-walking is only occasionally reached.

  • 4.
    Ericson, Anne
    et al.
    Karolinska Institute, Department of Molecular Medicine and Surgery, Section of Orthopaedics and Sports Medicine.
    Arndt, Anton
    Karolinska Institut, Department of Clinical Science, Intervention and Technology, Section of Orthopaedics.
    Stark, Andreas
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Zeleznik, Michael P.
    Saya Systems Inc., Salt Lake City, UT, USA.
    Olivecrona, Henrik
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Fusion of radio stereometric analysis data into computed tomography space: Application to the elbow joint2007In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 40, no 2, p. 296-304Article in journal (Refereed)
    Abstract [en]

    Improvement of joint prostheses is dependent upon information concerning the biomechanical properties of the joint. Radiostereometric analysis (RSA) and electromagnetic techniques have been applied in previous cadaver and in vivo studies on the elbow joint to provide valuable information concerning joint motion axes. However, such information is limited to mathematically calculated positions of the axes according to an orthogonal coordinate system and is difficult to relate to individual skeletal anatomy. The aim of this study was to evaluate the in vivo application of a new fusion method to provide three-dimensional (31)) visualization of flexion axes according to bony landmarks. In vivo RSA data of the elbow joint's flexion axes was combined with data obtained by 3D computed tomography (CT). Results were obtained from five healthy subjects after one was excluded due to an instable RSA marker. The median error between imported and transformed RSA marker coordinates and those obtained in the CT volume was 0.22mm. Median maximal rotation error after transformation of the rigid RSA body to the CT volume was 0.003 degrees. Points of interception with a plane calculated in the RSA orthogonal coordinate system were imported into the CT volume, facilitating the 3D visualization of the flexion axes. This study demonstrates a successful fusion of RSA and CT data, without significant loss of RSA accuracy. The method could be used for relating individual motion axes to a 3D representation of relevant joint anatomy, thus providing important information for clinical applications such as the development of joint prostheses.

  • 5.
    Eriksson, Marie
    et al.
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics. Karolinska Institutet.
    Broström, Eva
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Bartonek, Åsa
    Karolinska Institutet, Dept. of Women's and Child's Health.
    Gait pattern in children with arthrogryposis multiplex congenita2010In: Journal of Children's Orthopaedics, ISSN 1863-2521, E-ISSN 1863-2548, Vol. 4, no 1, p. 21-31Article in journal (Refereed)
    Abstract [en]

    Purpose: Lower limb contractures and muscle weakness are common in children with arthrogryposis multiplex congenita (AMC). To enhance or facilitate ambulation, orthoses may be used. The aim of this study was to describe gait pattern among individuals wearing their habitual orthotic devices. Methods: Fifteen children with AMC, mean age 12. 4 (4. 3) years, with some lower limb involvement underwent 3-D gait analysis. Three groups were defined based on orthosis use; Group 1 used knee-ankle-foot orthoses with locked knee joints, Group 2 used ankle-foot orthoses or knee-ankle-foot orthoses with open knee joints and Group 3 used no orthoses. Results: The greatest trunk and pelvis movements in all planes and the greatest hip abduction were observed in Group 1, compared to Groups 2 and 3, as well as to the gait laboratory control group. Maximum hip extension was similar in Groups 1 and 2, but in Group 3, there was less hip extension and large deviations from the control data. Lower cadence and walking speed were observed in Group 1 than in Groups 2 and 3. The step length was similar in all groups and also with respect to the gait laboratory reference values. Conclusions: Children with AMC were subdivided according to orthoses use. Kinematic data as recorded with 3-D gait analysis showed differences among the groups in trunk, pelvis and knee kinematics, and in cadence and walking speed. The step length was similar in all groups and to the gait laboratory reference values, which may be attributable to good hip extension strength in all participants.

  • 6. Flinck, M.
    et al.
    von Heideken, J.
    Janarv, P. -M
    Wåtz, Veronica
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Riad, J.
    Biomechanical comparison of semi-rigid pediatric locking nail versus titanium elastic nails in a femur fracture model2015In: Journal of Children's Orthopaedics, ISSN 1863-2521, E-ISSN 1863-2548, Vol. 9, no 1, p. 77-84Article in journal (Refereed)
    Abstract [en]

    Methods: Twenty-four femur models with an intramedullary canal diameter of 10.0 mm were used. Three groups with various combinations of titanium elastic nails (TEN) with end caps and one group with a PLN were tested. An oblique midshaft fracture was created, and the models underwent compression, rotation, flexion/extension, and a varus/valgus test, with 50 and 100 % of the forces generated during walking in corresponding planes. Results: We present the results [median (range)] from 100 % loading during walking. In axial compression, the PLN was less shortened than the combination with two 4.0-mm TEN [by 4.4 (3.4–5.4) mm vs. 5.2 (4.8–6.6) mm, respectively; p = 0.030]. No difference was found in shortening between the PLN and the four 3.0-mm TEN [by 7.0 (3.3–8.4) mm; p = 0.065]. The two 3.0-mm TEN did not withstand the maximum shortening of 10.0 mm. In external rotation, the PLN rotated 12.0° (7.0–16.4°) while the TEN models displaced more than the maximum of 20.0°. No model withstood a maximal rotation of 20.0° internal rotation. In the four-point bending test, in the coronal and the sagittal plane, all combinations except the two 3.0-mm TEN in extension withstood the maximum angulation of 20.0°. Conclusions: PLN provides the greatest stability in all planes compared to TEN models with end caps, even though the difference from the two 4.0-mm or four 3.0-mm TEN models was small. Background: The treatment for length-unstable diaphyseal femur fractures among school-age children is commonly intramedullary elastic nails, with or without end caps. Another possible treatment is the semi-rigid pediatric locking nail (PLN). The purpose of this biomechanical study was to assess the stability of a length-unstable oblique midshaft fracture in a synthetic femur model stabilized with different combinations of intramedullary elastic nails and with a PLN.

  • 7.
    Försth, Peter
    et al.
    Department of Orthopedics, Institution of Surgical Sciences, Uppsala University Hospital.
    Svedmark, Per
    Karolinska Institutet at Karolinska University Hospital Solna.
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT). Department of Orthopedics, Institution of Surgical Science, Uppsala University Hospital, Uppsala.
    Zeleznik, Michael P.
    University of Utah.
    Sandén, Bengt
    Department of Orthopedics, Institution of Surgical Science, Uppsala University Hospital, Uppsala.
    Motion Analysis in Lumbar Spinal Stenosis With Degenerative Spondylolisthesis: A Feasibility Study of the 3DCT Technique Comparing Laminectomy Versus Bilateral Laminotomy.2018In: Clinical spine surgery, ISSN 2380-0186, Vol. 31, no 8, p. E397-E402Article in journal (Refereed)
    Abstract [en]

    Study Design: This was a randomized radiologic biomechanical pilot study in vivo. Objective: The objectives of this study was to evaluate if 3-dimensional computed tomography is a feasible tool in motion analyses of the lumbar spine and to study if preservation of segmental midline structures offers less postoperative instability compared with central decompression in patients with lumbar spinal stenosis with degenerative spondylolisthesis. Summary of Background Data: The role of segmental instability after decompression is controversial. Validated techniques for biomechanical evaluation of segmental motion in human live subjects are lacking. Methods: In total, 23 patients (mean age, 68 y) with typical symptoms and magnetic resonance imaging findings of spinal stenosis with degenerative spondylolisthesis (>3 mm) in 1 or 2 adjacent lumbar levels from L3 to L5 were included. They were randomized to either laminectomy (LE) or bilateral laminotomy (LT) (preservation of the midline structures). Documentation of segmental motion was made preoperatively and 6 months postoperatively with CT in provoked flexion and extension. Analyses of movements were performed with validated software. The accuracy for this method is 0.6 mm in translation and 1 degree in rotation. Patient-reported outcome measures were collected from the Swespine register preoperatively and 2-year postoperatively. Results: The mean preoperative values for 3D rotation and translation were 6.2 degrees and 1.8 mm. The mean increase in 3D rotation 6 months after surgery was 0.25 degrees after LT and 0.7 degrees after LE (P=0.79) while the mean increase in 3D translation was 0.15 mm after LT and 1.1 mm after LE (P=0.42). Both surgeries demonstrated significant improvement in patient-reported outcome measures 2 years postoperatively. Conclusions: The 3D computed tomography technique proved to be a feasible tool in the evaluation of segmental motion in this group of older patients. There was negligible increase in segmental motion after decompressive surgery. LE with removal of the midline structures did not create a greater instability compared with when these structures were preserved.

  • 8.
    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.

  • 9.
    Gutierrez, Elena M
    et al.
    Karolinska Institutet, Dept. of Surgical Sciences, Orthopedics Section.
    Bartonek, Åsa
    Karolinska Institutet, Dept. of Women's and Child's Health.
    Haglund-Åkerlind, Yvonne
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Saraste, Helena
    Karolinska Institutet, Dept. of Surgical Sciences, Orthopedics Section.
    Kinetics of compensatory gait in persons with myelomeningocele2005In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 21, no 1, p. 12-23Article in journal (Refereed)
    Abstract [en]

    This study investigated the kinetic strategy and compensatory mechanisms during self-ambulatory gait in children with lumbo-sacral myelomeningocele. Thirty-one children with mid-lumbar to low-sacral myelomeningocele who walked without aids and 21 control children were evaluated by three-dimensional gait analysis. Joint moments in all planes at the hip and knee and sagittal moments at the ankle, as well as joint power and work done at all three joints, were analyzed. Joint moment capacity lost due to plantarflexor and dorsiflexor weakness was provided instead by orthotic support, but other joints were loaded more to compensate for the weakness at the ankles and restricted ankle motion. Subjects with total plantarflexor and dorsiflexor paresis and strength in the hip abductors had more knee extensor loading due to plantarflexor weakness and dorsiflexion angle of the orthotic, ankle joint. The subjects with orthoses also generated more power at the hip to supplement the power generation lost to plantarflexor weakness and fixed ankles. The most determinant muscle whose paresis changes gait kinetics was the hip abductor. Hip abductor weakness resulted in a characteristic pattern where the hips displayed an eccentric adduction moment, mediating energy transfer into the lower limbs, and the hips replaced the knees as power absorbers in early stance. Joint moment, power and work analyses complement a kinematic analysis to provide a complete picture of how children who have muscle paresis recruit stronger muscle groups to compensate for weaker ones.

  • 10.
    Halvorsen, Kjartan
    et al.
    The Swedish School of Sport and Health Sciences.
    Arndt, Anton
    Karolinska Institute.
    Lundberg, Arne
    Karolinska Institute.
    Estimating the directions of the talar and subtalar axes2007In: Proceedings of the International Society of Biomechanics XXI Congress, 2007Conference paper (Refereed)
  • 11.
    Jönhagen, Sven
    et al.
    Karolinska Institute.
    Halvorsen, Kjartan
    Swedish School of Sports and Health Sciences.
    Benoit, Daniel L
    Karolinska Institute.
    Muscle activation and length changes during two lunge exercises: implications for rehabilitation2009In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838, Scand J Med Sc Sports, Vol. 19, p. 561-568Article in journal (Refereed)
    Abstract [en]

    Eccentric exercises are commonly used as a treatment for various muscle and tendon injuries. During complex motions such as the forward lunge, however, it is not always clear which muscles may be contracting eccentrically and at what time. Because this exercise is used during rehabilitation, the purpose of this investigation was to determine what type of contractions take place during two different types of forward lunge and assess the implications for rehabilitation. Five experienced athletes performed five cycles for each of the walking and jumping forward lunges. Motion analysis was used to calculate the shortening or elongation of each muscle based on the change of position of their origin and insertion points during the lunge. Electromyography of the lateral hamstrings, rectus femoris and lateral gastrocnemius was combined with the muscle length change data to determine when isometric, concentric and eccentric activations occur during the lunge. Eccentric contractions in both the quadriceps and gastrocnemius were observed during the lunge. No hamstring eccentric contractions were found; however, the hamstrings showed isometric contractions during the first part of the stance phase.

  • 12. Karlsson, Anette
    et al.
    Leinhard, Olof Dahlqvist
    Aslund, Ulrika
    West, Janne
    Romu, Thobias
    Smedby, Örjan
    KTH, School of Technology and Health (STH), Medical Engineering, Medical Image Processing and Visualization. Linkoping Univ, Sweden.
    Zsigmond, Peter
    Peolsson, Anneli
    An Investigation of Fat Infiltration of the Multifidus Muscle in Patients With Severe Neck Symptoms Associated With Chronic Whiplash-Associated Disorder2016In: Journal of Orthopaedic and Sports Physical Therapy, ISSN 0190-6011, E-ISSN 1938-1344, Vol. 46, no 10, p. 886-893Article in journal (Refereed)
    Abstract [en]

    STUDY DESIGN: Cross-sectional study. BACKGROUND: Findings of fat infiltration in cervical spine multifidus, as a sign of degenerative morphometric changes due to whiplash injury, need to be verified. OBJECTIVES: To develop a method using water/fat magnetic resonance imaging (MRI) to investigate fat infiltration and cross-sectional area of multifidus muscle in individuals with whiplash associated disorders (WADS) compared to healthy controls. METHODS: Fat infiltration and cross-sectional area in the multifidus muscles spanning the C4 to C7 segmental levels were investigated by manual segmentation using water/fat-separated MRI in 31 participants with WAD and 31 controls, matched for age and sex. RESULTS: Based on average values for data spanning C4 to C7, participants with severe disability related to WAD had 38% greater muscular fat infiltration compared to healthy controls (P = .03) and 45% greater fat infiltration compared to those with mild to moderate disability related to WAD (P = .02). There were no significant differences between those with mild to moderate disability and healthy controls. No significant differences between groups were found for multifidus cross-sectional area. Significant differences were observed for both cross-sectional area and fat infiltration between segmental levels. CONCLUSION: Participants with severe disability after a whiplash injury had higher fat infiltration in the multifidus compared to controls and to those with mild/moderate disability secondary to WAD. Earlier reported findings using T1-weighted MRI were reproduced using refined imaging technology. The results of the study also indicate a risk when segmenting single cross-sectional slices, as both cross-sectional area and fat infiltration differ between cervical levels.

  • 13.
    Linder, Hugo
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems.
    Rosenberg, Viktor
    Mätning av axelkraft: En studie av en modell och prototyp för mätning av axelkraft vid abduktion2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    During rehabilitation, it is important to know if and when the muscles in the injured area have regained their strength. Regarding shoulder injuries, there is currently no established method of measuring muscle strength. In the methods tested, certain attributes are undesirable. Therefore, Karolinska Universitetssjukhuset, Huddinge is looking into developing a new, improved method. In this method, one should be able to measure a patient's muscle strength and study the difference in measurements over time. The maximum muscle strength and the muscle strength at 45 ° of abduction and flexion is of interest. The project is to produce a prototype that can be used according to the new method and see if the prototype is appropriate. A test group consisting of both healthy and shoulder injured patients performed tests regarding the prototype accuracy of angular measurement, prototype usability and appropriate angle for maximum muscle strength in the shoulder. The result showed that the prototype accuracy was within the approved range of the method. Usability was also approved as all test subjects could use the prototype within the limits we set. We did not see an overall trend in which maximum muscle force in the shoulder were obtained at 45 °. For further work and increased validity, further studies with larger test groups is required

  • 14.
    Lundblad, Henrik
    et al.
    Karolinska Institute, Stockholm, Sweden.
    Karlsson-Thur, Charlotte
    Karolinska Institute, Stockholm, Sweden.
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Jonsson, Cathrine
    Karolinska University Hospital, Stockholm, Sweden.
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Zeleznik, Michael P.
    University of Utah.
    Weidenhielm, Lars
    Karolinska Institutet at Karolinska University Hospital Solna.
    Can Spatiotemporal Fluoride (18F-ˆ’) Uptake be Used to Assess Bone Formation in the Tibia?: A Longitudinal Study Using PET/CT2017In: Clinical Orthopaedics and Related Research, ISSN 0009-921X, E-ISSN 1528-1132, Vol. 475, no 5, p. 1486-1498Article in journal (Refereed)
    Abstract [en]

    When a bone is broken for any reason, it is important for the orthopaedic surgeon to know how bone healing is progressing. There has been resurgence in the use of the fluoride (18F-ˆ’) ion to evaluate various bone conditions. This has been made possible by availability of positron emission tomography (PET)/CT hybrid scanners together with cyclotrons. Absorbed on the bone surface from blood flow, 18F-ˆ’ attaches to the osteoblasts in cancellous bone and acts as a pharmacokinetic agent, which reflects the local physiologic activity of bone. This is important because it shows bone formation indicating that the bone is healing or no bone formation indicating no healing. As 18F-ˆ’ is extracted from blood in proportion to blood flow and bone formation, it thus enables determination of bone healing progress.

  • 15.
    Lundblad, Henrik
    et al.
    Karolinska Institutet, Sweden.
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Karlsson-Thur, Charlotte
    Karolinska Institutet, Sweden.
    Jonsson, Cathrine
    Karolinska University Hospital Solna, Sweden.
    Noz, Marilyn E.
    New York University, USA.
    Zeleznik, Michael P.
    University of Utah, USA.
    Jacobsson, Hans
    Karolinska Institutet, Sweden.
    Weidenhielm, Lars
    Karolinska Institutet, Sweden.
    Using PET/CT Bone Scan Dynamic Data to Evaluate Tibia Remodeling When a Taylor Spatial Frame Is Used: Short and Longer Term Differences2015In: BioMed Research International, ISSN 2314-6133, E-ISSN 2314-6141, Vol. 2015, p. 1-11, article id 574705Article in journal (Refereed)
    Abstract [en]

    Eighteen consecutive patients, treated with a Taylor Spatial Frame for complex tibia conditions, gave their informed consentto undergo Na18F− PET/CT bone scans. We present a Patlak-like analysis utilizing an approximated blood time-activity curveeliminating the need for blood aliquots. Additionally, standardized uptake values (SUV) derived from dynamic acquisitions werecompared to this Patlak-like approach. Spherical volumes of interest (VOIs) were drawn to include broken bone, other (normal)bone, and muscle. The SUV𝑚(𝑡) (𝑚 = max, mean) and a series of slopes were computed as (SUV𝑚(𝑡𝑖) − SUV𝑚(𝑡𝑗))/(𝑡𝑖 − 𝑡𝑗), forpairs of time values 𝑡𝑖 and 𝑡𝑗. A Patlak-like analysis was performed for the same time values by computing ((VOI𝑝(𝑡𝑖)/VOI𝑒(𝑡𝑖)) −(VOI𝑝(𝑡𝑗)/VOI𝑒(𝑡𝑗)))/(𝑡𝑖−𝑡𝑗), where p = broken bone, other bone, andmuscle and e = expected activity in aVOI. Paired comparisonsbetween Patlak-like and SUV𝑚 slopes showed good agreement by both linear regression and correlation coefficient analysis(𝑟 = 84%, 𝑟𝑠 = 78%-SUVmax, 𝑟 = 92%, and 𝑟𝑠 = 91%-SUVmean), suggesting static scans could substitute for dynamic studies.Patlak-like slope differences of 0.1 min−1 or greater between examinations and SUVmax differences of ∼5 usually indicated goodremodeling progress, while negative Patlak-like slope differences of −0.06 min−1 usually indicated poor remodeling progress in thiscohort.

  • 16.
    Maguire Jr., Gerald Q.
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Olivecrona, Henrik
    Karolinska Institute.
    Zeleznik, Michael P.
    University of Utah, Salt Lake City, UT, USA.
    Weidenhielm, Lars
    Karolinska Institute.
    A New Automated Way to Measure Polyethylene Wear in THA Using a High Resolution CT Scanner: Method and Analysis2014In: Scientific World Journal, ISSN 1537-744X, E-ISSN 1537-744X, Vol. 2014, p. 528407-Article in journal (Refereed)
    Abstract [en]

    As the most advantageous total hip arthroplasty (THA) operation is the first, timely replacement of only the liner is socially and economically important because the utilization of THA is increasing as younger and more active patients are receiving implants and they are living longer. Automatic algorithms were developed to infer liner wear by estimating the separation between the acetabular cup and femoral component head given a computed tomography (CT) volume. Two series of CT volumes of a hip phantom were acquired with the femoral component head placed at 14 different positions relative to the acetabular cup. The mean and standard deviation (SD) of the diameter of the acetabular cup and femoral component head, in addition to the range of error in the expected wear values and the repeatability of all the measurements, were calculated. The algorithms resulted in a mean (+/- SD) for the diameter of the acetabular cup of 54.21 (+/- 0.011) mm and for the femoral component head of 22.09 (+/- 0.02) mm. The wear error was +/- 0.1 mm and the repeatability was 0.077 mm. This approach is applicable clinically as it utilizes readily available computed tomography imaging systems and requires only five minutes of human interaction.

  • 17. Naili, J. E.
    et al.
    Broström, E. W.
    Gutierrez-Farewik, Elena M.
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics. KTH, School of Engineering Sciences (SCI), Centres, BioMEx.
    Schwartz, M. H.
    The Centre Of Mass Trajectory Is A Sensitive And Responsive Measure Of Compensations For Pain And Weakness Among Individuals With Knee Osteoarthritis Performing A Sit-To-Stand Test2017In: Osteoarthritis and Cartilage, ISSN 1063-4584, E-ISSN 1522-9653, Vol. 25, p. S125-S126Article in journal (Other academic)
  • 18. 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.

  • 19.
    Olivecrona, Henrik
    et al.
    Karolinska.
    Hessman, P.
    Sollerman, Christer M.
    Noz, Marilyn E.
    New York University.
    Maguire Jr., Gerald Q.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Zeleznik, Michael P.
    A New Method to Evaluate Migration in Total Wrist Arthroplasties Using CT and a Semi-automated Progran for Volume Fusion2004Conference paper (Refereed)
  • 20.
    Olivecrona, Henrik
    et al.
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Zeleznik, Michael P.
    Saya Systems Inc., Salt Lake City, UT, USA.
    Sollerman, Christer M.
    Handkirurgiska verksamhetsområdet, Sahlgrenska Universitetssjukhuset/Sahlgrenska, Göteborg.
    Olivecrona, Lotta
    Karolinska Institutet, Department of Clinical Science, Intervention and Technology, Division of Radiology.
    A new computed tomography-based radiographic method to detect early loosening of total wrist implants2007In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 48, no 9, p. 997-1003Article in journal (Refereed)
    Abstract [en]

    Background: Diagnosis of loosening of total wrist implants is usually late using routine radiographs. Switching modality to computed tomography (CT) should aid in early diagnosis. Purpose: To propose and evaluate the accuracy of a new CT method for assessing loosening of the carpal component in total wrist arthroplasty. Material and Methods: A protocol encompassing volume registration of paired CT scans of patients with unexplained pain in a prosthetically replaced wrist (used in clinical routine) is presented. Scans are acquired as a dynamic examination under torsional load. Using volume registration, the carpal component of the prosthesis is brought into spatial alignment. After registration, prosthetic loosening is diagnosed by a shift in position of the bones relative to the prosthesis. This study is a preclinical validation of this method using a human cadaverous arm with a cemented total wrist implant and tantalum markers. Seven CT scans of the arm were acquired. The scans were combined into 21 pairs of CT volumes. The carpal component was registered in each scan pair, and the residual mismatch of the surrounding tantalum markers and bone was analyzed both visually and numerically. Results: The detection limit for prosthetic movement was less than 1 mm. Conclusion: The results of this study demonstrate that CT volume registration holds promise to improve detection of movement of the carpal component at an earlier stage than is obtainable with plain radiography.

  • 21.
    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.

  • 22.
    Olivecrona, Henrik
    et al.
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Olivecrona, Lotta
    Karolinska Institutet, Department of Clinical Science, Intervention and Technology, Division of Radiology.
    Weidenhielm, Lars
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Maguire Jr., Gerald Q.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Zeleznik, Michael P.
    RAHD Oncology Products, St. Lous, MO, USA.
    Svensson, Lars E.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    Jonson, T.
    Stability of acetabular axis after total hip arthroplasty, repeatability using CT and a semiautomated program for volume fusion2003In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 44, no 6, p. 653-661Article in journal (Refereed)
    Abstract [en]

    Purpose: To validate a CT method for detecting changes in acetabular cup orientation after THA. Material and Methods: 26 CT examinations were obtained from a pelvic model with an uncemented acetabular cup. The model position was altered between acquisitions, but the cup axis angle vis-a-vis the pelvis was maintained. Data sets were combined into 37 pairs, each containing a unique positioning error. The pelvi in different examinations were fused, creating transformed volumes. Landmarks corresponding to the cup before and after fusion were placed interactively by two independent examiners. The orientation of the acetabular axis was calculated for each volume and compared across volumes. Results: Before fusion the mean angle error between the acetabular axes was 4.17degrees (SD +/- 1.95degrees). After fusion the mean angle error was 0.36degrees (SD +/- 0.17). The 95% repeatability limits were below 0.7degrees. There was no significant interobserver difference. Analysis of the cup landmarking pattern by condition numbers and individual landmark errors showed stability. Conclusion: Non-invasive fusion of CT volumes and a stable landmarking pattern for the acetabular cup outperforms routine plain radiography in detecting changes in the orientation of the acetabular axis over time. The method delivers both visual and numerical output and could be used in clinical practice.

  • 23.
    Olivecrona, Henrik
    et al.
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Weidenhielm, Lars
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Olivecrona, Lotta
    Karolinska Institutet, Department of Clinical Science, Intervention and Technology, Division of Radiology.
    Beckman, M. O.
    Stark, Andreas
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Maguire Jr., Gerald Q.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Zeleznik, Michael P.
    RAHD Oncology Products, St. Loius MO, USA.
    Svensson, Lars E.
    KTH, Superseded Departments, Mathematics.
    Jonson, T.
    A new CT method for measuring cup orientation after total hip arthroplasty: A study of 10 patients2004In: Acta Orthopaedica Scandinavica, ISSN 0001-6470, Vol. 75, no 3, p. 252-260Article in journal (Refereed)
    Abstract [en]

    Background It is difficult to assess the orientation of the acetabular component on routine radiographs. We present a method for determining the spatial orientation of the acetabular component after total hip arthroplasty (THA) using computed tomography. Patients and methods Two CT-scans, 10 min apart, were obtained from each of 10 patients after THA. Using locally developed software, two independent examiners measured the orientation of the acetabular component in relation to the pelvis. The measurements were repeated after one week. To be independent of the patient position during scanning, the method involved two steps. Firstly, a 3D volumetric image of the pelvis was brought into a standard pelvic orientation, then the orientation of the acetabular component was measured. The orientation of the acetabular component was expressed as operative anteversion and inclination relative to an internal pelvic reference coordinate system. To evaluate precision, we compared measurements across pairs of CT volumes between observers and trials. Results Mean absolute interobserver angle error was 2.3degrees for anteversion (range 0-6.6degrees), and 1.1degrees for inclination (range 0-4.6degrees). For interobserver measurements, the precision, defined as one standard deviation, was 2.9degrees for anteversion, and 1.5degrees for inclination. A Student's West showed that the overall differences between the examiners, trials, and cases were not significant. Data were normally distributed and were not dependent on examiner or trial. Interpretation We conclude that the implant angles of the acetabular component in relation to the pelvis could be detected repeatedly using CT, independently of patient positioning.

  • 24.
    Olivecrona, Henrik
    et al.
    Soder Sjukhuset, Dept Hand Surgery.
    Weidenhielm, Lars
    Karolinska Hosp, Dept Orthoped.
    Olivecrona, Lotta
    Karolinska Hosp, Dept Radiologyy.
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Maguire Jr., Gerald Q.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Zeleznik, Michael P.
    RAHD Oncology Products, St. Louis, MO, USA.
    Svensson, Lars E.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    Jonson, T.
    Spatial component position in total hip arthroplasty - Accuracy and repeatability with a new CT method2003In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 44, no 1, p. 84-91Article in journal (Refereed)
    Abstract [en]

    Purpose: 3D detection of centerpoints of prosthetic cup and head after total hip arthroplasty (THA) using CT. Material and Methods: Two CT examinations, 10 min apart, were obtained from each of 10 patients after THA. Two independent examiners placed landmarks in images of the prosthetic cup and head. All landmarking was repeated after 1 week. Centerpoints were calculated and compared. Results: Within volumes, all measurements of centerpoints of cup and head fell, with a 95% confidence, within one CT-voxel of any other measurement of the same object. Across two volumes, the mean error of distance between center of cup and prosthetic head was 1.4 mm (SD 0.73). Intra- and interobserver 95% accuracy limit was below 2 mm within and below 3 mm across volumes. No difference between intra- and interobserver measurements occurred. A formula for converting finite sets of point landmarks in the radiolucent tread of the cup to a centerpoint was stable. The percent difference of the landmark distances from a calculated spherical surface was within one CT-voxel. This data was normally distributed and not dependent on observer or trial. Conclusion: The true 3D position of the centers of cup and prosthetic head can be detected using CT. Spatial relationship between the components can be analyzed visually and numerically.

  • 25.
    Olivecrona, Lotta
    et al.
    Karolinska Hospital, Department of Radiology.
    Crafoord, Joakim
    Karolinska Hospital, Department of Radiology.
    Olivecrona, Henrik
    Karolinska Hosp, Dept Orthopaed.
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Maguire Jr., Gerald Q.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Zeleznik, Michael P.
    RAHD Oncology Products, St. Louism MO, USA.
    Svensson, Lars E.
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    Weidenhielm, Lars
    Karolinska Hosp, Dept Orthopaed.
    Acetabular component migration in total hip arthroplasty using CT and a semiautomated program for volume merging2002In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 43, no 5, p. 517-527Article in journal (Refereed)
    Abstract [en]

    Purpose: To develop a non-invasive method for detection of acetabular cup migration after total hip arthroplasty (THA) with a higher degree of accuracy than routine plain radiography. Material and Methods: Two CT examinations, 10 min apart, were obtained from each of 10 patients that had undergone THA. Using an in-house developed semiautomated program for volume merging, the pelves in the two examinations were fused and the acetabular cup was visually and numerically evaluated to test the method's accuracy in detecting migration. Results: In the visual evaluation of the best match a 1-mm translation of the cup was detectable. The numerical evaluation, comparing landmarks placed in the images of the acetabular cup and the head of the femur component in the two examinations, showed the mean difference in orientation of acetabular axes to be 2.5degrees, the mean distance between centre of cup face to be 2.5 mm and the mean distance between centre of the head of the prosthetic femoral component to be 1 mm. Conclusion: This method has a significantly higher accuracy than routine plain radiography in detecting acetabular cup migration and could be used in clinical practice. It gives both a visual and a numerical correlate to migration.

  • 26.
    Olivecrona, Lotta
    et al.
    Karolinska Institutet, Department of Clinical Science, Intervention and Technology, Division of Radiology.
    Jedenmalm, Anneli
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Aspelin, Peter
    Karolinska Institutet, Department of Clinical Science, Intervention and Technology, Division of Radiology.
    Weidenhielm, Lars
    Karolinska Institutet, Dept. Orthoped..
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Zeleznik, Michael P.
    RAHD Oncology Products, St. Louis. Mo.
    Olivecrona, Henrik
    Department of Hand Surgery, Södersjukhuset, Stockholm.
    Assessing wear of the acetabular cup using computed tomography: an ex vivo study2005In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 46, no 8, p. 852-857Article in journal (Refereed)
    Abstract [en]

    Purpose: To validate a clinically useful method for measuring acetabular cup wear using computed tomography (CT). Material and Methods: Eight uncemented acetabular cups were scanned twice ex vivo using CT. The linear penetration depth of the femoral component head into the cup and the thickness of the remaining polyethylene liner were measured in the CT volumes using dedicated software. Two independent examiners twice assessed each volume. The CT measurements were compared to direct measurements using a coordinate measuring device and micrometer measurements. Results: Accuracy of wear measurements expressed as penetration depth was +/- 0.6 and +/- 1.0 mm for the two examiners, respectively, with no significant differences between examiners, trials, and CT scans. Accuracy of measurements of remaining polyethylene was +/- 1.3 and +/- 1.0 mm, respectively, for the two examiners. Systematic differences between examiners were found, but no significant differences between trials and CT scans. These differences were due to different interpretations of metal artifacts in the volumes. Conclusion: The proposed CT method for evaluating wear as head penetration depth allows for reliable wear detection at a clinically relevant level. Measurements of remaining polyethylene on CT volumes are not as reliable as wear measurements owing to metal artifacts.

  • 27.
    Olivecrona, Lotta
    et al.
    Karolinska Hosp, Dept Radiology.
    Olivecrona, Henrik
    Soder Sjukhuset, Dept Hand Surg, Stockholm, Sweden .
    Weidenhielm, Lars
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Maguire Jr., Gerald Q.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Zeleznik, Michael P.
    RAHD Oncology Products, St. Louis, MO, USA.
    Model studies on acetabular component migration in total hip arthroplasty using CT and a semiautomated program for volume merging2003In: Acta Radiologica, ISSN 0284-1851, E-ISSN 1600-0455, Vol. 44, no 4, p. 419-429Article in journal (Refereed)
    Abstract [en]

    Purpose: Validation of a non-invasive CT method for detection of acetabular cup migration after total hip arthroplasty in a phantom study. Material and Methods: 26 CT examinations were obtained of a pelvic model while altering the position of the acetabular cup. Using a previously described program for volume merging, the pelvi in different examinations were fused and the 3D alterations of the position of the acetabular cup were evaluated visually and numerically and correlated to direct measurements on the model. Results: Visually, two independent examiners differentiated between 0, 1 and 2 to 3 mm migration with 100% specificity and sensitivity. Numerically, the mean error over all cases between model and CT measurements was 0.04 mm (SD +/- 0.33). The mean absolute error between model and CT data was 0.26 mm (SD +/- 0.19). Intra- and interobserver 95% accuracy and repeatability limits were below 0.5/0.7 mm, respectively. No significant interobserver difference occurred. The data were normally distributed and not dependent on observer. Conclusion: The accuracy of this non-invasive method out-performs routine plain radiography. The method gives both visual and numerical correlates to migration and can be used in clinical practice.

  • 28.
    Otten, Volker
    et al.
    Department of Surgical and Perioperative Sciences (Institutionen för kirurgisk och perioperativ vetenskap), Umeå University, Umeå, Sweden.
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Zeleznik, Michael P.
    University of Utah.
    Nilsson, Kjell G.
    Department of Surgical and Perioperative Sciences (Institutionen för kirurgisk och perioperativ vetenskap), Umeå University, Umeå, Sweden.
    Olivecrona, Henrik
    Karolinska Institutet, Sweden.
    Are CT Scans a Satisfactory Substitute for the Follow-Up of RSA Migration Studies of Uncemented Cups?: A Comparison of RSA Double Examinations and CT Datasets of 46 Total Hip Arthroplasties2017In: BioMed Research International, ISSN 2314-6133, E-ISSN 2314-6141, Vol. 2017, p. 1-11, article id 3681458Article in journal (Refereed)
    Abstract [en]

    As part of the 14-year follow-up of a prospectively randomized radiostereometry (RSA) study on uncemented cup fixation, two pairs of stereo radiographs and a CT scan of 46 hips were compared. Tantalum beads, inserted during the primary operation, were detected in the CT volume and the stereo radiographs and used to produce datasets of 3D coordinates. The limit of agreement between the combined CT and RSA datasets was calculated in the same way as the precision of the double RSA examination. The precision of RSA corresponding to the 99% confidence interval was 1.36°, 1.36°, and 0.60° for -, -, and -rotation and 0.40, 0.17, and 0.37 mm for -, -, and -translation. The limit of agreement between CT and RSA was 1.51°, 2.17°, and 1.05° for rotation and 0.59, 0.56, and 0.74 mm for translation. The differences between CT and RSA are close to the described normal 99% confidence interval for precision in RSA: 0.3° to 2° for rotation and 0.15 to 0.6 mm for translation. We conclude that measurements using CT and RSA are comparable and that CT can be used for migration studies for longitudinal evaluations of patients with RSA markers.

  • 29.
    Riad, Jacques
    et al.
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Modlesky, Christopher
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics. KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Broström, Eva W.
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Are Muscle Volume Differences Related to Concentric Muscle Work During Walking in Spastic Hemiplegic Cerebral Palsy?2012In: Clinical Orthopaedics and Related Research, ISSN 0009-921X, E-ISSN 1528-1132, Vol. 470, no 5, p. 1278-1285Article in journal (Refereed)
    Abstract [en]

    Background: Individuals with spastic hemiplegic cerebral palsy are typically high functioning and walk without assistive devices. The involved limb is usually smaller and shorter, although it is not clear whether the difference in muscle volume has an impact on walking capacity. Questions/purposes: We determined the volume of muscles important for propulsion and related that volume to concentric muscle work during walking on the hemiplegic and noninvolved sides in patients with cerebral palsy. Patients and Methods: We studied 46 patients (mean age, 17.6 years; range, 13-24 years) with spastic hemiplegic cerebral palsy. We assessed muscle volume using MRI and concentric muscle work in the sagittal plane from the hip, knee, and ankle using three-dimensional gait analysis. Patients were classified by Winters' criteria to assess the involvement of cerebral palsy and movement pattern during walking. Results: On the hemiplegic side, muscles were smaller, except for the gracilis muscle, and concentric muscle work from the ankle plantar flexors, knee extensors, and hip flexors and extensors was lower compared to the noninvolved side. Hip extensor work was higher on the hemiplegic and the noninvolved sides compared to a control group of 14 subjects without cerebral palsy. Hemiplegic to noninvolved volume ratios correlated with work ratios (r = 0.40-0.66). The Winters classification and previous calf muscle surgery predicted work ratios. Conclusions: Our observations of smaller muscles on the hemiplegic side and changes in muscle work on both sides can help us distinguish between primary deviations that may potentially be treatable and compensatory mechanisms that should not be treated.

  • 30.
    Svedmark, Per
    et al.
    Karolinska Institutet at Karolinska University Hospital Solna.
    Berg, Svante
    Stockholm Spine Center, Löwenströmska Hospital.
    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.
    Weidenhielm, Lars
    Karolinska Institutet at Karolinska University Hospital Solna.
    Nemeth, Gunnar
    Capio S:t Göran Sjukhuset.
    Olivecrona, Henrik
    A New CT Method for Assessing 3D Movements in Lumbar Facet Joints and Vertebrae in Patients before and after TDR2015In: BioMed Research International, ISSN 2314-6133, Vol. 2015, p. 1-9, article id 260703Article in journal (Refereed)
    Abstract [en]

    This study describes a 3D-CT method for analyzing facet joint motion and vertebral rotation in the lumbar spine after TDR. Ten patients were examined before and then three years after surgery, each time with two CT scans: provoked flexion and provoked extension. After 3D registration, the facet joint 3D translation and segmental vertebral 3D rotation were analyzed at the operated level (L5-S1) and adjacent level (L4-L5). Pain was evaluated using VAS. The median (±SD) 3D movement in the operated level for the left facet joint was 3.2 mm (±1.9 mm) before and 3.5 mm (±1.7 mm) after surgery and for the right facet joint was 3.0 mm (±1.0 mm) before and 3.6 mm (±1.4 mm) after surgery. The median vertebral rotation in the sagittal plane at the operated level was 5.4° (±2.3°) before surgery and 6.8° (±1.7°) after surgery and in the adjacent level was 7.7° (±4.0°) before and 9.2° (±2.7°) after surgery. The median VAS was reduced from 6 (range 5–8) to 3 (range 2–8) in extension and from 4 (range 2–6) to 2 (range 1–3) in flexion.

  • 31.
    Svedmark, Per
    et al.
    Karolinska Institute, Department Orthopaed..
    Weidenhielm, Lars
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Nemeth, Gunnar
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Tullberg, Tycho
    Lowenstromska Sjukhuset, Stockholm Spine Ctr, Upplands Vasby, Sweden .
    Noz, Marilyn E.
    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.
    Olivecrona, Henrik
    Karolinska Institute, Department of Molecular Medicine and Surgery.
    Model studies on segmental movement in lumbar spine using a semi-automated program for volume fusion2008In: Journal of Computer-Aided Surgery, ISSN 1092-9088, E-ISSN 1097-0150, Vol. 13, no 1, p. 14-22Article in journal (Refereed)
    Abstract [en]

    Objective: To validate a new non-invasive CT method for measuring segmental translations in lumbar spine in a phantom using plastic vertebrae with tantalum markers and human vertebrae. Material and Methods: One hundred and four CT volumes were acquired of a phantom incorporating three lumbar vertebrae. Lumbar segmental translation was simulated by altering the position of one vertebra in all three cardinal axes between acquisitions. The CT volumes were combined into 64 case pairs, simulating lumbar segmental movement of up to 3 mm between acquisitions. The relative movement between the vertebrae was evaluated visually and numerically using a volume fusion image post-processing tool. Results were correlated to direct measurements of the phantom. Results: On visual inspection, translation of at least 1 mm or more could be safely detected and correlated with separation between the vertebrae in three dimensions. There were no significant differences between plastic and human vertebrae. Numerically, the accuracy limit for all the CT measurements of the 3D segmental translations was 0.56 mm (median: 0.12; range: -0.76 to +0.49 mm). The accuracy for the sagittal axis was 0.45 mm (median: 0.10; range: -0.46 to +0.62 mm); the accuracy for the coronal axis was 0.46 min (median: 0.09; range: -0.66 to +0.69 mm); and the accuracy for the axial axis was 0.45 mm (median: 0.05; range: -0.72 to +0.62 mm). The repeatability, calculated over 10 cases, was 0.35 mm (median: 0.16; range: -0.26 to +0.30 mm). Conclusion: The accuracy of this non-invasive method is better than that of current routine methods for detecting segmental movements. The method allows both visual and numerical evaluation of such movements. Further studies are needed to validate this method in patients.

  • 32.
    Wang, Ruoli
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Gutierrez-Farewik, Elena M.
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics.
    Compensatory strategies during walking in response to excessive muscle co-contraction at the ankle joint2014In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 39, no 3, p. 926-932Article in journal (Refereed)
    Abstract [en]

    Excessive co-contraction causes inefficient or abnormal movement in several neuromuscular pathologies. How synergistic muscles spanning the ankle, knee and hip adapt to co-contraction of ankle muscles is not well understood. This study aimed to identify the compensation strategies required to retain normal walking with excessive antagonistic ankle muscle co-contraction. Muscle-actuated simulations of normal walking were performed to quantify compensatory mechanisms of ankle and knee muscles during stance in the presence of normal, medium and high levels of co-contraction of antagonistic pairs gastrocnemius + tibialis anterior and soleus + tibialis anterior. The study showed that if co-contraction increases, the synergistic ankle muscles can compensate; with gastrocmemius + tibialis anterior co-contraction, the soleus will increase its contribution to ankle plantarflexion acceleration. At the knee, however, almost all muscles spanning the knee and hip are involved in compensation. We also found that ankle and knee muscles alone can provide sufficient compensation at the ankle joint, but hip muscles must be involved to generate sufficient knee moment. Our findings imply that subjects with a rather high level of dorsiflexor + plantarflexor co-contraction can still perform normal walking. This also suggests that capacity of other lower limb muscles to compensate is important to retain normal walking in co-contracted persons. The compensatory mechanisms can be useful in clinical interpretation of motion analyses, when secondary muscle co-contraction or other deficits may present simultaneously in subjects with motion disorders.

  • 33.
    Weidenhielm, Lars
    et al.
    Karolinska Institutet at Karolinska University Hospital Solna.
    Olivecrona, Henrik
    Karolinska Institutet, Sweden.
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Noz, Marilyn E.
    New York University, Department of Radiology.
    Prosthetic liner wear in total hip replacement: a longitudinal 13-year study with computed tomography.2018In: Skeletal Radiology, ISSN 0364-2348, E-ISSN 1432-2161, p. 1-5Article in journal (Refereed)
    Abstract [en]

    This case report follows a woman who had a total hip replacement in 1992 when she was 45 years old. Six serial computed tomography (CT) examinations over a period of 13 years provided information that allowed her revision surgery to be limited to liner replacement as opposed to replacement of the entire prosthesis. Additionally, they provided data that ruled out the presence of osteolysis and indeed none was found at surgery. In 2004, when the first CT was performed, the 3D distance the femoral head had penetrated into the cup was determined to be 2.6 mm. By 2017, femoral head penetration had progressed to 5.0 mm. The extracted liner showed wear at the thinnest part to be 5.5 mm, as measured with a micrometer. The use of modern CT techniques can identify problems, while still correctable without major surgery. Furthermore, the ability of CT to assess the direction of wear revealed that the liner wear changed from the cranial to dorsal direction.

  • 34. Xia, Yang
    et al.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    The First Study of Cartilage by Magnetic Resonance: A Historical Account2016In: Cartilage, ISSN 1947-6035, E-ISSN 1947-6043, Vol. 7, no 4, p. 293-297Article in journal (Refereed)
    Abstract [en]

    Objective. To recap the historical journey leading to the first cartilage research article using nuclear magnetic resonance (NMR), published in 1955 by 2 Swedish researchers, Erik Odeblad and Gunnar Lindstrom. Design. Extensive Internet search utilizing both English and Swedish websites, and reading the dissertations available at the Royal Institute of Technology (Stockholm, Sweden) and via interlibrary loans at Oakland University (Michigan, USA). Results. Using a primitive NMR instrument that Lindstrom built for his graduate research at the Nobel Institute for Physics (Stockholm, Sweden), Odeblad and Lindstrom studied the characteristics of the NMR signal in calf cartilage. The authors wrote, "In cartilage and fibrous tissue, in which the proton signals probably arise from highly viscous water with short spin-lattice relaxation time, the signals were also larger than would correspond to the water content." The authors speculated the signal differences between water and biological tissues could be attributed to the absorption and organization of the water molecules to the proteins in the tissue, which was remarkably accurate. Conclusions. It is quite certain that Odeblad and Lindstrom published the first biomedical study using NMR in 1955. In this article, cartilage and a number of other biological tissues were examined for the first time using NMR.

  • 35.
    Xie, Meng
    et al.
    Karolinska Inst, Dept Physiol & Pharmacol, Stockholm, Sweden..
    Gol'din, Pavel
    Stockholm Univ, Stockholm, Sweden..
    Estsfa, Jordi
    Uppsala Univ, Dept Organismal Biol, Uppsala, Sweden..
    Li, Lei
    Karolinska Inst, Dept Physiol & Pharmacol, Stockholm, Sweden..
    Linares Arregui, Irene
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Gasser, T. Christian
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Medvedeva, Ekaterina
    Sechenov Med Univ, Moscow, Russia..
    Svetlana, Kotova
    Sechenov Med Univ, Moscow, Russia..
    Timashev, Peter
    Sechenov Med Univ, Moscow, Russia..
    Adameyko, Igor
    Karolinska Inst, Dept Physiol & Pharmacol, Stockholm, Sweden..
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Sanchez, Sophie
    Uppsala Univ, Dept Organismal Biol, Uppsala, Sweden..
    Chagin, Andrei
    Karolinska Inst, Dept Physiol & Pharmacol, Stockholm, Sweden..
    Evolutional Separation of Epiphyseal and Articular Cartilage is a Bone Adaptation to Terrestrial Growth2017In: Journal of Bone and Mineral Research, ISSN 0884-0431, E-ISSN 1523-4681, Vol. 32, p. S328-S328Article in journal (Other academic)
1 - 35 of 35
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