| 51. |
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| 52. |
- Hedenstierna, Sofia, 1976-, et al.
(författare)
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How does a three-dimensional continuum muscle model affect the kinematics and muscle strains of a finite element neck model compared to a discrete muscle model in rear-end, frontal, and lateral impacts
- 2008
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Ingår i: Spine. - : Lippincott Williams & Wilkins. - 0362-2436 .- 1528-1159. ; 33:8, s. E236-E245
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Tidskriftsartikel (refereegranskat)abstract
- STUDY DESIGN. A finite element (FE) model of the human neck with incorporated continuum or discrete muscles was used to simulate experimental impacts in rear, frontal, and lateral directions. OBJECTIVE. The aim of this study was to determine how a continuum muscle model influences the impact behavior of a FE human neck model compared with a discrete muscle model. SUMMARY OF BACKGROUND DATA. Most FE neck models used for impact analysis today include a spring element musculature and are limited to discrete geometries and nodal output results. A solid-element muscle model was thought to improve the behavior of the model by adding properties such as tissue inertia and compressive stiffness and by improving the geometry. It would also predict the strain distribution within the continuum elements. METHODS. A passive continuum muscle model with nonlinear viscoelastic materials was incorporated into the KTH neck model together with active spring muscles and used in impact simulations. The resulting head and vertebral kinematics was compared with the results from a discrete muscle model as well as volunteer corridors. The muscle strain prediction was compared between the 2 muscle models. RESULTS. The head and vertebral kinematics were within the volunteer corridors for both models when activated. The continuum model behaved more stiffly than the discrete model and needed less active force to fit the experimental results. The largest difference was seen in the rear impact. The strain predicted by the continuum model was lower than for the discrete model. CONCLUSION. The continuum muscle model stiffened the response of the KTH neck model compared with a discrete model, and the strain prediction in the muscles was improved.
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| 53. |
- Hedenstierna, Sofia, 1976-, et al.
(författare)
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Neck Muscle Load Distribution in Lateral, Frontal, and Rear-end Impacts : A Three-Dimensional Finite Element Analysis
- 2009
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Ingår i: Spine. - 0362-2436 .- 1528-1159. ; 34:24, s. 2626-2633
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Tidskriftsartikel (refereegranskat)abstract
- Study Design. A finite element (FE) model of the human neck was used to study the distribution of neck muscle loads during multidirectional impacts. The computed load distributions were compared to experimental electromyography (EMG) recordings. Objective. To quantify passive muscle loads in nonactive cervical muscles during impacts of varying direction and energy, using a three-dimensional (3D) continuum FE muscle model. Summary of Background Data. Experimental and numerical studies have confirmed the importance of muscles in the impact response of the neck. Although EMG has been used to measure the relative activity levels in neck muscles during impact tests, this technique has not been able to measure all neck muscles and cannot directly quantify the force distribution between the muscles. A numerical model can give additional insight into muscle loading during impact. Methods. An FE model with solid element musculature was used to simulate frontal, lateral, and rear-end vehicle impacts at 4 peak accelerations. The peak cross-sectional forces, internal energies, and effective strains were calculated for each muscle and impact configuration. The computed load distribution was compared with experimental EMG data. Results. The load distribution in the cervical muscles varied with load direction. Peak sectional forces, internal energies, and strains increased in most muscles with increasing impact acceleration. The dominant muscles identified by the model for each direction were splenius capitis, levator scapulae, and sternocleidomastoid in lateral impacts, splenius capitis, and trapezoid in frontal impacts, and sternocleidomastoid, rectus capitis posterior minor, and hyoids in rear-end impacts. This corresponded with the most active muscles identified by EMG recordings, although within these muscles the distribution of forces and EMG levels were not the same. Conclusion. The passive muscle forces, strains, and energies computed using a continuum FE model of the cervical musculature distinguished between impact directions and peak accelerations, and on the basis of prior studies, isolated the most important muscles for each direction.
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| 54. |
- Henriques, Thomas, et al.
(författare)
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Biomechanical comparison of five different atlantoaxial posterior fixation techhniques
- 2000
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Ingår i: Spine. - 0362-2436 .- 1528-1159. ; 25:22, s. 2877-2883
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Tidskriftsartikel (refereegranskat)abstract
- STUDY DESIGN:Five different reconstructions of the atlantoaxial complex were biomechanically compared in vitro in a nondestructive test.OBJECTIVES:To determine whether non-bone graft-dependent one-point fixation affords stability levels equivalent to three-point reconstructions.SUMMARY OF BACKGROUND DATA:Previous investigations have demonstrated that three-point fixation, using bilateral transarticular screws in combination with posterior wiring, provide the most effective resistance to minimize motion around C1-C2. However, placement of transarticular screws is technically demanding. Posterior wiring techniques affording one-point fixation have failure rates of approximately 15%, with failure considered to be secondary to structural bone graft failures. One-point, non-bone graft-dependent fixations have not been tested.METHODS:Eight human cervical specimens, C0-C3 were loaded nondestructively. Unconstrained three-dimensional segmental motion was measured. The reconstructions tested were two one-point fixations, one two-point fixation, and two three-point fixations.RESULTS:Under axial rotation two and three-point reconstructions provided better stiffness than the one-point reconstructions (P < 0.05). During flexion-extension, higher stiffness levels were observed in one- and three-point fixations when compared with the intact spine (P < 0.05). In lateral bending no significant differences were observed among the six groups, although the trend was that reconstructions including transarticular screws provided greater stability than one-point fixations.CONCLUSION:The current findings substantiate the use of three-point fixation as the treatment of choice for C1-C2 instability. [l: atlantoaxial fixation, biomechanics, cervical spine, instability, spinal instrumentation, transarticular screws]
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| 55. |
- Henriques, Thomas, et al.
(författare)
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Letter to the editor
- 2001
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Ingår i: Spine. - 0362-2436 .- 1528-1159. ; 26:21, s. 2405-
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 56. |
- Hermansen, Anna, et al.
(författare)
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A Comparison Between the Carbon Fiber Cage and the Cloward Procedure in Cervical Spine Surgery A Ten- to Thirteen-Year Follow-Up of a Prospective Randomized Study
- 2011
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Ingår i: SPINE. - : J B Lippincott Co. - 0362-2436 .- 1528-1159. ; 36:12, s. 919-925
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Tidskriftsartikel (refereegranskat)abstract
- Study Design. Ten- to 13-year follow-up of a prospective randomized study. Objective. To compare the 10- to 13-year outcomes of anterior cervical decompression and fusion (ACDF) with a cervical intervertebral fusion cage (CIFC), and the Cloward procedure (CP) using a broad clinical and patient-centered assessment. Summary of Background Data. There are few prospective studies and none with a follow-up of 10 years or more. Methods. Patient questionnaires completed 10 years or more after ACDF. Seventy-three patients (77%) responded. Radiographs were obtained at 2 years. Results. Apart from greater fulfillment of preoperative expectation (P = 0.01) and less headache (P = 0.005) in the CIFC group compared with the CP group, there were no significant differences in the outcomes of the two surgical methods. Pain intensity improved in comparison with preoperative levels in both the CIFC and CP groups (P andlt; 0.0001), but the Neck Disability Index (NDI) only improved in the CIFC group (P = 0.04). Only those with a healed fusion benefited from an improved NDI (P = 0.02). There was no deterioration in pain intensity or NDI after the 2-year follow-up. Conclusion. The outcomes of the two surgical methods, with a few exceptions, were equal at 10- to 13-year follow-up, and there was no deterioration in outcome after the 2-year follow-up. Pain intensity improved more than disability, which may indicate that further improvement of physical function requires early more extensive postoperative rehabilitation. Despite persisting disability, repeat surgery was relatively uncommon.
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| 57. |
- Hirasawa, Atsuhiko, et al.
(författare)
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Regional Differences in Diffuse Idiopathic Skeletal Hyperostosis : A Retrospective Cohort Study from Sweden and Japan
- 2018
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Ingår i: Spine. - 0362-2436 .- 1528-1159. ; 43:24, s. E1474-E1478
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Tidskriftsartikel (refereegranskat)abstract
- Study Design: We retrospectively reviewed computed tomography (CT) records of patients in Japan and Sweden, which are both aging populations. Objective. To research the influence of ethnicity and region on diffuse idiopathic skeletal hyperostosis (DISH) prevalence.Summary of Background Data_ DISH can complicate nonsurgical treatment of spinal fractures and often requires surgical intervention. We previously reported a prevalence of DISH in Japan that was higher than that reported in other studies.Methods: We retrospectively reviewed CT records of patients in Japan and Sweden, which have both aging populations. Patients undergoing whole body CT during trauma examinations at an acute outpatient clinic in Uppsala University Hospital in a 1-year period were eligible for inclusion. Excluded were those less than 40 and more than or equal to 90 years old, and those with previous spinal surgery. The prevalence of DISH by sex and age was determined according to radiographic criteria by Resnick. Results from Sweden were compared with the Japan data, which we previously reported.Results: Age of the eligible subjects (265 men and 153 women) ranged from 40 to 89 years, with a mean age of 63.4 years. Among men, 86 (32.5%) were diagnosed with DISH, and the results by age (40s, 50s, 60s, 70s, and 80s) were: 6 (10.7%), 13 (22%), 35 (46.1%), 17 (34%), and 15 (62.5%) patients, respectively. Among women, 16 (10.5%) had DISH, and the results by age were as follows: 1 (2.6%), 1 (3.3%), 2 (6.7%), 6 (22.2%), and 6 (22.2%) patients, respectively. These results did not differ from those previously published for Japan (Fisher exact test, men: P = 1, 0.27, 0.12, 0.06, and 1, respectively; women: P = 0.49, 0.62, 0.5, 0.8, and 0.3, respectively).Conclusion: The presented cohort study revealed that ethnicity and region may not be notable factors of DISH prevalence, since patients from both Japan and Sweden had similar DISH prevalence.Level of Evidence: 3
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| 58. |
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| 59. |
- Huang, Q M, et al.
(författare)
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Intramuscular myoelectric activity and selective coactivation of trunk muscles during lateral flexion with and without load.
- 2001
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Ingår i: Spine. - : Ovid Technologies (Wolters Kluwer Health). - 0362-2436 .- 1528-1159. ; 26:13, s. 1465-72
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Tidskriftsartikel (refereegranskat)abstract
- STUDY DESIGN: Myoelectric activity of trunk muscles was measured intramuscularly in six healthy subjects as they maintained static trunk postures at 0 degrees, 15 degrees, and 30 degrees of lateral bending, unloaded or holding a 20-kg load in one hand alongside the body. OBJECTIVE: To determine the position and load dependency of the agonistic and antagonistic myoelectric responses of deep and superficial trunk lateral flexor muscles. SUMMARY OF BACKGROUND DATA: Loading of the trunk in lateral bending is associated with incidences of low back pain. The neuromotor control of muscles surrounding the spine may be decisive for its vulnerability. Earlier documentation of the activation pattern of trunk muscles, particularly those situated deeply, is incomplete. METHODS: Trunk angle was measured between S1-C7 and the vertical with a protractor. Electromyographic activity was recorded unilaterally from eight trunk muscles using intramuscular fine-wire electrodes inserted under the guidance of ultrasound. RESULTS: The electromyographic data showed that all muscles on the side contralateral to the load, except rectus abdominis, had their highest activity while loaded in the position most laterally flexed to the loaded side. The degree of bilateral coactivation was greater for the ventral than for the dorsal muscles. CONCLUSIONS: The myoelectric responses of most lumbar trunk muscles to static lateral flexion were dependent on trunk position and loading. The abdominal muscles demonstrated more coactivation than the other trunk muscles, and thus appeared to contribute more to trunk stabilization in laterally bent and loaded trunk positions.
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| 60. |
- Jensen, Irene B., et al.
(författare)
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Assessing the Needs of Patients in Pain: A Matter of Opinion?
- 2000
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Ingår i: Spine. - : LWW. - 0362-2436 .- 1528-1159. ; 25:21, s. 2816-2823
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Tidskriftsartikel (refereegranskat)abstract
- Study Design. A prospective cohort study including patients with nonspecific spinal pain was performed.Objectives. To investigate whether the use of expert judgment in routine practice can provide a basis for reliable decision making concerning the need for intervention in patients with spinal pain and their ability to benefit from treatment.Summary of Background Data. A wide range of instruments and techniques are used to assess and treat patients with spinal pain. Many instruments are used without being clinimetrically tested.Methods. A questionnaire concerning the patients’ need of treatment and their potential to assimilate it was sent to experts in the health care arena: physicians, physical therapists, social insurance officers. The experts included were those connected with patients participating in a larger outcome study. Two cohorts of patients (sample 1, n = 217; sample 2, n = 257) were followed for 6 and 12 months, during which time the patients’ health and work status were mapped.Results. No acceptable agreement was found between any of the experts’ ratings of patients’ needs and potential for rehabilitation. Logistic regression showed that the experts’ judgments were based almost solely on the age of the patient. The prediction analyses showed that the most consistent predictor of the patients’ status at the 6-month follow-up assessment was the patients’ own belief in the existence of effective treatments and their perceived ability for learning to cope with the condition.Conclusions. Expert judgment as exercised in routine practice cannot be used as basis for reliable decision making concerning the need of the patient with spinal pain for intervention and the patient’s ability to benefit from treatment.
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