Our findings suggest that injury sizes large enough to disrupt biomechanical function are needed to drive degenerative changes in rat caudal disc AF. Based on the data, we believe that small anular defects become sealed, allowing the disc to function normally and the AF to heal. Larger defects appear to require longer wound closure times, and may prolong the duration of impaired disc function.

Damage of the annulus fibrosus is implicated in common spinal pathologies. The objective of this study was to obtain a quantitative relationship between both the number of cycles and the magnitude of tensile strain resulting in damage to the annulus fibrosus. Four rectangular tensile specimens oriented in the circumferential direction were harvested from the outer annulus of 8 bovine caudal discs (n = 32) and subjected to one of four tensile testing protocols: (i) ultimate tensile strain (UTS) test; (ii) baseline cyclic test with 4 series of 400 cycles of baseline cyclic loading (peak strain = 20% UTS); (iii & iv) acute and fatigue damage cyclic tests consisting of 4 x 400 cycles of baseline cyclic loading with intermittent loading to 1 and 100 cycles, respectively, with peak tensile strain of 40%, 60%, and 80% UTS. Normalized peak stress for all mechanically loaded specimens was reduced from 0.89 to 0.11 of the baseline control levels, and depended on the magnitude of damaging strain and number of cycles at that damaging strain. Baseline, acute, and fatigue protocols resulted in permanent deformation of 3.5%, 6.7% and 9.6% elongation, respectively. Damage to the laminate structure of the annulus in the absence of biochemical activity in this study was assessed using histology, transmission electron microscopy, and biochemical measurements and was most likely a result of separation of annulus layers (i.e., delamination). Permanent elongation and stress reduction in the annulus may manifest in the motion segment as sub-catastrophic damage including increased neutral zone, disc bulging, and loss of nucleus pulposus pressure. The preparation of rectangular tensile strip specimens required cutting of collagen fibers and may influence absolute values of results, however, it is not expected to affect the comparisons between loading groups or dose-response reported.

BackgroundBalloon guide catheters (BGCs) achieve proximal flow control during thrombectomy but antegrade intracranial flow often persists via the Circle of Willis. Closely sizing an aspiration catheter to the target vessel might achieve greater flow control and improve technical performance. Our objective was to measure the impact of aspiration catheter size on distal flow control and flow reversal with and without the use of BGCs. Clot retrieval testing was performed to establish the impact of these parameters on revascularization.MethodsAn in vitro thrombectomy model replicated in vivo conditions. Flow was measured continuously using ultrasonic flow sensors placed 20 cm distal to the catheter tip in the middlel cerebral artery (MCA). Four aspiration catheters of increasing size were evaluated: ACE 60 and 64 (Penumbra), SOFIA Plus (MicroVention), and Millipede 088 (Perfuze). Two clot analog types (red blood cell-rich and fibrin/platelet-rich) were used for clot retrieval testing.ResultsThe larger area of the ‘superbore’ Millipede 088 catheter resulted in a larger reduction in antegrade flow than standard aspiration catheters, even when the latter were combined with a BGC. During aspiration, 6Fr catheters were unable to cause flow reversal in the distal MCA while the Millipede 088 achieved significant distal flow reversal (−146 mL/min) (P<0.0001*) (*denotes significance). The solo use of Millipede 088 resulted in better recanalization outcomes and significantly reduced distal emboli for internal carotid artery (P=0.015*) and MCA (P=0.014*) occlusions compared with all other devices and combinations.ConclusionsMaximizing the catheter-to-vessel size facilitates near flow-arrest on catheter insertion, potentially negating the need for a BGC. A 0.088 inch aspiration catheter enables significant flow reversal in the distal MCA during aspiration.

BackgroundLarger bore aspiration catheters are expected to significantly improve the speed and completeness of acute stroke revascularization.ObjectiveTo evaluate the navigability and clot retrieval performance of a novel 8Fr aspiration catheter, Millipede 088 (Perfuze Ltd), using fresh-frozen cadavers and an in vitro thrombectomy model, respectively.MethodsCadaveric study: Transfemoral catheterization of the intracranial arteries was performed in six cadavers, allowing evaluation of navigation to 12 middle cerebral arteries (MCAs) and six basilar arteries. Commercially available 6Fr aspiration catheters (SOFIA Plus, Microvention) were used as controls. In vitro study: Three human blood clot phenotypes were created; red blood cell-rich, mixed, and fibrin/platelets-rich. Two clot sizes, resulting in occlusion of the internal carotid artery (ICA) and MCA-M1 were investigated. Endpoints were first-pass effect (FPE), first-pass complete ingestion, and second-pass recanalization.ResultsCadaveric study: Both the Millipede 088 and SOFIA Plus devices reached the distal MCA-M1 and the basilar artery in 10/12 and 2/2 of the navigation attempts, respectively. In the two instances of unsuccessful navigation, neither device was able to cross the ophthalmic artery. In vitro study: In 10 mm long M1 occlusions, Millipede 088 achieved 100% FPE versus 40% for 6Fr devices (p>0.001). In 20 mm long ICA occlusions, Millipede 088 achieved 100% removal success within two passes in each clot phenotype compared with an average of 27% for 6Fr devices (p>0.001).ConclusionsNavigation of the Millipede 088 catheter to the MCA-M1 and basilar artery is feasible in a cadaver model. Millipede 088 demonstrates superiority over 6Fr aspiration catheters for three representative clot phenotypes at the most common sites of occlusion in an in vitro vasculature model.

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