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Title: Morphological, histological and biomechanical adaptation of the rat musculoskeletal system to electrical muscle stimulation
Author: Vickerton, Paula
ISNI:       0000 0004 5363 2343
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2014
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Musculoskeletal tissues exhibit a remarkable extent of plasticity throughout life, with tissues continually able to adapt in line with functional demands. As the skeleton plays a major structural role, its form is profoundly influenced by its mechanical environment, which is largely determined by muscular contraction. Despite the clear functional link between muscle and bone relatively little is known about the biomechanical relationship between these tissues. This thesis therefore focuses upon the use of implantable neuromuscular stimulators to provide controlled muscular mechanical stimuli. Stimulators were implanted into Wistar rats, inducing muscular contraction every 30 seconds for 28 days. Following stimulation, microCT, histology, and nanoindentation were used to establish changes occurring at the micro and macro-scale in muscle and skeletal architecture. Analysis revealed a localised region of extensive bone growth, with significant increases in cross-sectional area (28.61%, p<0.05) and bone volume (30.29%, p<0.05) in the stimulated limb. Bone growth was confined to the region which showed peak strain (640μƐ +30.4μƐ). Histology targeted to this region showed clusters of chondrocytes within this new bone growth, possibly indicative of growth via an endochondral process. This region showed a correspondingly low elastic modulus (8.8+2.2 GPa) when compared with established cortical bone (20+1.4 GPa). To investigate the biomechanical impact of the structural differences in control and stimulated tibiae microCT data were used to construct computational models. Models were used to simulate force propagation throughout the bones in response to muscular contraction. In addition, models were created to investigate the impact of muscle force, bone material properties and bone geometry. The addition of a layer of newly deposited, nascent bone to this region increased effective strain by 8-28% and reduced effective stress by 37-44%. Complete mineralisation of the nascent bone region combined with associated reductions of muscle force production, yielded a significant decrease in both effective strain and stress. This thesis has demonstrated a rapid and profound skeletal and muscular response to sustained muscle contractions. As such it is a potent reminder of core ideas concerning the significance of interactions amongst tissues in determining overall musculoskeletal form.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Q Science (General)