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Author

Fredrik Einarsson

Other affiliations: University of Gothenburg
Bio: Fredrik Einarsson is an academic researcher from Sahlgrenska University Hospital. The author has contributed to research in topics: Contracture & Subscapularis muscle. The author has an hindex of 5, co-authored 6 publications receiving 266 citations. Previous affiliations of Fredrik Einarsson include University of Gothenburg.

Papers
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Journal ArticleDOI
TL;DR: The passive mechanical properties of small muscle fiber bundles obtained from surgical patients with spasticity and patients without neuromuscular disorders were measured to determine the relative influence of intracellular and extracellular components.
Abstract: The passive mechanical properties of small muscle fiber bundles obtained from surgical patients with spasticity (n = 9) and patients without neuromuscular disorders (n = 21) were measured in order to determine the relative influence of intracellular and extracellular components. For both types of patient, tangent modulus was significantly greater in bundles compared to identical tests performed on isolated single cells (P < 0.05). However, the relative difference between bundles and single cells was much greater in normal tissue than spastic tissue. The tangent modulus of normal bundles (462.5 +/- 99.6 MPa) was 16 times greater than normal single cells (28.2 +/- 3.3 MPa), whereas the tangent modulus of spastic bundles (111.2 +/- 35.5 MPa) was only twice that of spastic muscle cells (55.0 +/- 6.6 MPa). This relatively small influence of the extracellular matrix (ECM) in spastic muscle was even more surprising because spastic muscle cells occupied a significantly smaller fraction of the total specimen area (38.5 +/- 13.6%) compared to normal muscle (95.0 +/- 8.8%). Based on these data, normal muscle ECM is calculated to have a modulus of 8.7 GPa, and the ECM from spastic muscle of only 0.20 GPa. These data indicate that spastic muscle, although composed of cells that are stiffer compared to normal muscle, contains an ECM of inferior mechanical strength. The present findings illustrate some of the profound changes that occur in skeletal muscle secondary to spasticity. The surgical implications of these results are discussed.

227 citations

Journal ArticleDOI
TL;DR: It is concluded that secondary changes in muscle fibre properties will occur as a result of a longstanding lack of sufficient passive stretch, leading to compensatory changes in the extracellular matrix.
Abstract: This study investigates the passive mechanical properties of the subscapularis muscle in children with a contracture as a result of obstetrical brachial plexus palsy. Muscle biopsies were harvested from nine children undergoing open surgery for shoulder contracture. Passive mechanical testing of single cells and muscle bundles was performed. Corresponding comparisons were made using muscle biopsies from seven healthy controls. Single muscle fibres from patients with obstetric brachial plexus palsy displayed a shorter slack sarcomere length, linear deformation of the fibre within a wider zone of sarcomere length and a greater relative increase in stiffness compared with muscle bundles. We conclude that secondary changes in muscle fibre properties will occur as a result of a longstanding lack of sufficient passive stretch, leading to compensatory changes in the extracellular matrix. These results suggest the presence of a dynamic feedback system constituting a muscle-to-extracellular matrix communication interface.

38 citations

Journal ArticleDOI
TL;DR: The findings support the assumption that shortening of the subscapularis is caused primarily by the nerve injury, which weakens the antagonistic lateral rotators, but that direct injury to the muscle might be a contributory factor.
Abstract: The aim of this study was to obtain a better understanding of the cause of the medial rotation contracture of the shoulder after obstetric brachial plexus lesions by studying the morphology of the shortened subscapularis muscle. Muscle biopsy specimens were harvested from 13 children with obstetric brachial plexus palsy who underwent corrective surgery for the rotation contracture. The majority of the subscapularis muscle biopsy samples had an essentially normal morphology and showed a predominance of type I myosin heavy chain isoform, while one biopsy showed signs of marked fibrosis and a predominance of type II myosin heavy chain isoform. The findings support the assumption that shortening of the subscapularis is caused primarily by the nerve injury, which weakens the antagonistic lateral rotators, but that direct injury to the muscle might be a contributory factor.

20 citations

Journal ArticleDOI
TL;DR: It is concluded that muscle biopsies from the supraspinatus in retracted rotator cuff tears respond normally to mechanical testing in vitro.
Abstract: The aim of the present study was to assess the function of the isolated muscle component in retracted rotator cuff tears. Muscle biopsies were harvested from the supraspinatus and the ipsilateral deltoid in seven patients undergoing surgery for a large, retracted rotator cuff tear. Single fibres and fibre bundles were subjected to passive stretching in vitro with subsequent recordings of tension and sarcomere lengths using the laser diffraction technique. Stress–strain curves were plotted, and the elastic modulus was calculated for all preparations. Morphology was evaluated with regard to collagen fraction, ratio between fast and slow fibres, fibre size and fibre size variability using standard staining techniques. Intra-individual comparisons of the stress–strain curves showed a high degree of conformity in terms of both shape and tangent values, and there were no statistically significant differences in the elastic modulus for single fibres and bundles in the deltoid and supraspinatus muscles, respectively, supported by the analysis of the observed confidence interval of the differences between the paired values of the elastic modulus. There were no differences in collagen content, fibre size and ratio between fast and slow fibres in the deltoid and supraspinatus muscles, respectively. We conclude that muscle biopsies from the supraspinatus in retracted rotator cuff tears respond normally to mechanical testing in vitro.

5 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the effect of storage of human muscle biopsies on passive mechanical properties and found that the storage of muscle biopsy data significantly reduced passive mechanical property degradation.
Abstract: Background The purpose of this study was to investigate the effect of storage of human muscle biopsies on passive mechanical properties.

5 citations


Cited by
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Journal ArticleDOI
TL;DR: The structure, composition, and mechanical properties of skeletal muscle ECM are reviewed; the cells that contribute to the maintenance of the ECMAreas for future study are proposed; and overview changes that occur with pathology are described.
Abstract: The skeletal muscle extracellular matrix (ECM) plays an important role in muscle fiber force transmission, maintenance, and repair. In both injured and diseased states, ECM adapts dramatically, a property thathas clinical manifestations and alters muscle function. Here, we review the structure, composition, and mechanical properties of skeletal muscle ECM, describe the cells that contribute to the maintenance of the ECM and, finally, overview changes that occur with pathology. New scanning electron micrographs of ECM structure are also presented with hypotheses about ECM structure-function relationships. Detailed structure-function relationships of the ECM have yet to be defined and, as a result, we propose areas for future studies.

737 citations

Journal ArticleDOI
TL;DR: A 66-year-old man was suddenly unable to speak, follow directions, or move his right arm and leg within 90 minutes and his speech was limited to effortful answers of yes or no.
Abstract: A 66-year-old man was suddenly unable to speak, follow directions, or move his right arm and leg. He received tissue plasminogen activator within 90 minutes. Four days later, his speech was limited to effortful answers of yes or no. He could not walk or use his right arm, and self-care tasks required maximal assistance. What advice would you offer him and his family regarding rehabilitation for his disabilities?

731 citations

Journal ArticleDOI
TL;DR: Clinicians should encourage patients to build greater strength, speed, endurance, and precision of multijoint movements on tasks that increase independence and enrich daily activity to augment rehabilitation in the next decade.
Abstract: Summary Rehabilitation after hemiplegic stroke has typically relied on the training of patients in compensatory strategies. The translation of neuroscientific research into care has led to new approaches and renewed promise for better outcomes. Improved motor control can progress with task-specific training incorporating increased use of proximal and distal movements during intensive practice of real-world activities. Functional gains are incorrectly said to plateau by 3–6 months. Many patients retain latent sensorimotor function that can be realised any time after stroke with a pulse of goal-directed therapy. The amount of practice probably best determines gains for a given level of residual movement ability. Clinicians should encourage patients to build greater strength, speed, endurance, and precision of multijoint movements on tasks that increase independence and enrich daily activity. Imaging tools may help clinicians determine the capacity of residual networks to respond to a therapeutic approach and help establish optimal doseresponse curves for training. Promising adjunct approaches include practice with robotic devices or in a virtual environment, electrical stimulation to increase cortical excitability during training, and drugs to optimise molecular mechanisms for learning. Biological strategies for neural repair may augment rehabilitation in the next decade.

642 citations

Journal ArticleDOI
TL;DR: A three-dimensional finite-element model of the biceps brachii was created and it was revealed that the variation in fascicle lengths within the muscle and the curvature of the fascicles were the primary factors contributing to nonuniform strains.

405 citations

Journal ArticleDOI
TL;DR: The literature supports the notion that, although spasticity is multifactorial and neural in origin, significant structural alterations in muscle also occur and an understanding of the specific changes that occur in the muscle and extracellular matrix may facilitate the development of new conservative or surgical therapies for this problem.
Abstract: This review summarizes current information regarding the changes in structure or function that occur in skeletal muscle secondary to spasticity. Most published studies have reported an increase in fiber size variability in spastic muscle. There is no general agreement regarding any shift in fiber type distribution secondary to spasticity. Mechanical studies in whole limbs as well as in isolated single cells support the notion of an intrinsic change in the passive mechanical properties of muscle after spasticity in addition to the more widely reported neural changes that occur. Evidence is presented for changes within both the muscle cell and extracellular matrix that contribute to the overall changes in the tissue. Taken together, the literature supports the notion that, although spasticity is multifactorial and neural in origin, significant structural alterations in muscle also occur. An understanding of the specific changes that occur in the muscle and extracellular matrix may facilitate the development of new conservative or surgical therapies for this problem.

357 citations