STUDY DESIGN: A disc model with full anular division was used to investigate how different biomechanical parameters influence the severity of nuclear disruption during compressive loading. OBJECTIVE: To quantify the manner in which flexion, hydration, and loading rate contribute to the breakdown in the intrinsic cohesive structure of the nucleus pulposus. SUMMARY OF BACKGROUND DATA: The risk of disc herniation is known to increase when the disc is loaded in flexed positions. However, there is a lack of experimental data showing how a combination of flexion with different loading rates and hydration levels affects the extent of nuclear disruption. METHODS: A reproducible state of full hydration was established for isolated bovine caudal discs. A period of static preloading at an applied stress of 1 MPa was used to obtain a consistent state of partial hydration. Then 96 discs were subjected to a full-thickness division of the anulus fibrosus and compressed while hydration level, degree of flexion, and rate of loading were varied systematically. RESULTS: A full spectrum of nuclear damage was observed in the tests, ranging from no detectable disruption to sudden sequestration of the entire nucleus. These results were quantified, and a general correlation was established between the severity of disruption and the different loading parameters. CONCLUSIONS: The degree of flexion and the level of hydration were shown to play an important role in influencing the tendency of the nucleus to break loose and extrude through a preexisting anular division. Interestingly, the rate of loading appeared to have only a minor effect on the severity of damage induced in discs that incorporated a full depth anular division.
STUDY DESIGN: A disc model with full anular division was used to investigate how different biomechanical parameters influence the severity of nuclear disruption during compressive loading. OBJECTIVE: To quantify the manner in which flexion, hydration, and loading rate contribute to the breakdown in the intrinsic cohesive structure of the nucleus pulposus. SUMMARY OF BACKGROUND DATA: The risk of disc herniation is known to increase when the disc is loaded in flexed positions. However, there is a lack of experimental data showing how a combination of flexion with different loading rates and hydration levels affects the extent of nuclear disruption. METHODS: A reproducible state of full hydration was established for isolated bovine caudal discs. A period of static preloading at an applied stress of 1 MPa was used to obtain a consistent state of partial hydration. Then 96 discs were subjected to a full-thickness division of the anulus fibrosus and compressed while hydration level, degree of flexion, and rate of loading were varied systematically. RESULTS: A full spectrum of nuclear damage was observed in the tests, ranging from no detectable disruption to sudden sequestration of the entire nucleus. These results were quantified, and a general correlation was established between the severity of disruption and the different loading parameters. CONCLUSIONS: The degree of flexion and the level of hydration were shown to play an important role in influencing the tendency of the nucleus to break loose and extrude through a preexisting anular division. Interestingly, the rate of loading appeared to have only a minor effect on the severity of damage induced in discs that incorporated a full depth anular division.
Authors: Yongren Wu; Sarah E Cisewski; Barton L Sachs; Vincent D Pellegrini; Michael J Kern; Elizabeth H Slate; Hai Yao Journal: J Biomech Date: 2015-07-10 Impact factor: 2.712
Authors: Pilar Sainz de Baranda; Antonio Cejudo; Victor Jesus Moreno-Alcaraz; Maria Teresa Martinez-Romero; Alba Aparicio-Sarmiento; Fernando Santonja-Medina Journal: PeerJ Date: 2020-01-02 Impact factor: 2.984