3 results
Filters
Settings
Now showing1 - 3 of 3
- Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Biomechanical analysis of atlas fractures : a study on 40 human atlas specimens(Lippincott Williams & Wilkins, 2008-04-01); ; ; STUDY DESIGN. Forty isolated specimens of the first cervical vertebra were tested by the application of pure axial force to failure. To exclude ligamentous side effects, transverse ligaments were dissected in all specimens. OBJECTIVE. To investigate the biomechanical characteristics of the human atlas and to describe the influence of different speeds of force impact on the fracture types. SUMMARY OF BACKGROUND DATA. Atlas fractures have been reproduced in some studies in the literature. However, the characteristics of isolated atlas fractures under pure axial loading at different speeds has not been reported so far. METHODS. After dissection of soft tissue and generation of a peripheral quantitative computed tomography scan, the atlas preparations were tested to failure by displacement-controlled axial force application at constant speeds of either 0.5 mm/s (Group 1) or 300 mm/s (Group 2). The fracture types were classified according to Gehweiler. RESULTS. At slow loading speed (Group 1), 2 Type-I (anterior arch), 3 Type-II (posterior arch), 2 Type-III (anterior and posterior arch), and 13 Type-IV (lateral mass) fractures occurred out of 20 specimens. At high loading speed (Group 2), Type-III fractures (burst fractures of 2 to 4 parts) occurred in all 20 tested specimens. CONCLUSION. The presented results strongly suggest that the Type of atlas fracture depends on the speed of axial force impact. The present study demonstrates that Type-III fractures (2- to 4-part burst fractures) result from fast force impact whereas slow force impact is responsible for Type-IV atlas fractures of the lateral mass. © 2008 Lippincott Williams & Wilkins, Inc.Publicationtype: Journal Article16 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Intramuscular pressure in the erector spinae and intra-abdominal pressure related to posture and load(Lippincott Williams & Wilkins, 1998); ; ; Study Design. Intramuscular pressures in both Erectors Spinae and intra- abdominal pressures were measured during different holding tasks. Objectives. To investigate the potential for using intramuscular pressure measurements in both Erectors Spinae to better quantitative the role of muscles during different lifting tasks in vivo. Summary of Background Data. Intramuscular pressure and intra-abdominal pressure were measured previously under isometric and dynamic conditions. However, no previous study systematically has addressed the relation between intramuscular and intra-abdominal pressures and different loads, tasks, and postures. Methods. Intramuscular and intra-abdominal were measured simultaneously with microtip pressure transducers in 10 healthy volunteers performing 24 different static holding tasks. Tasks included different weights (10 kg and 20 kg), postures (squat or back lift), and positions of the weight. Results. Intramuscular pressures were dependent on posture. Kyphotic back posture produced intramuscular pressures of 120-130 mm Hg, compared with the 10-25 mm Hg produced when volunteers were in the erect position (P < 0.001). Holding a 10-kg weight at the things close to the body produced significantly (P < 0.001) lower intramuscular pressure (25-32 mm Hg) than that produced by holding it 25 cm it front of the body (47-56 mm Hg). In all tasks, intramuscular pressures were significantly higher with the 20-kg weight than with the 10-kg weight (P < 0.001). Highest values (> 300 mm Hg) were measured when the 20-kg weight was held in the kyphotic posture above the floor and 25 cm away from the body. Conclusions. Intramuscular pressure measurements in the erector spinae seem to be a valuable tool for quantitating the role of bank muscles during different lifting tasks.Publicationtype: Journal Article2 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Stability of the instrumented spine : dynamic versus rigid instrumentation(Lippincott Williams & Wilkins, 1996); ; 6