Thomas Steffen — Page 2

PubMed1998

Lumbar intradiscal pressure measured in the anterior and posterolateral annular regions during asymmetrical loading.

OBJECTIVE: To analyze the effect of asymmetrical loading on intradiscal pressure. DESIGN: Human cadaveric lumbar spines were instrumented with multiple pressure sensors and subjected to external mechanical loads. BACKGROUND: Tears and radial fissures in the posterolateral annulus with no evidence of annular protrusion or nuclear extrusion are frequently observed in non-degenerated intervertebral discs. Cadaveric studies have shown that asymmetrical loads lead to posterolateral herniation. Regional overload may be responsible for a progressive structural weakness of the posterolateral annular fibres. METHODS: Three needles each equipped with three independent pressure sensors were inserted in the midplane of the L(3)/L(4) intervertebral disc (n = 16) in the anterior, right posterolateral and left posterolateral regions. Axial rotation was applied in the upright, flexed and extended positions and the pressures recorded. RESULTS: The largest intradiscal pressure increase was observed in the posterolateral inner annular regions, more so in flexion than extension, when combined with axial rotation. Significant centripetal pressure gradients were found only in the posterolateral needles during the upright and flexed positions. CONCLUSIONS: When applying compression and axial rotation, the posterolateral inner annular zones of the intervertebral disc show high stress peaks and centripetal pressure gradients. Asymmetrical loads (rotation) combined with postural changes in the sagittal plane increase these effects, and may be responsible for a chronic mechanical overload of these regions. RELEVANCE: Our findings suggest a predilection for the posterolateral inner annular regions to mechanical failure, especially under asymmetrical loading.

Journal Article↗

PubMedDate not supplied

Biological evaluation of chitosan salts cross-linked to genipin as a cell scaffold for disk tissue engineering.

Degenerative disc disease has been implicated as a major component of spine pathology. However, although biological repair of the degenerate disk would be the ideal treatment, there is no universally accepted scaffold for tissue engineering of the intervertebral disk. To help remedy this, we investigated the gelation kinetics of various concentrations (2.5 to 10%) of two water-soluble chitosan chlorides (low molecular weight Protasan UP CL113 and high molecular weight Protasan UP CL213) and two chitosan glutamates (low molecular weight Protasan UP G113 and high molecular weight Protasan UP G213). Various concentrations (5 to 20%) of genipin, a naturally occurring cross-linking reagent used in herbal medicine and in the fabrication of food dyes, were used to prepare cross-linked chitosan hydrogels. The results show that 2.5% Protasan UP G213 cross-linked to 5% genipin was the best candidate. This formulation gelled fastest at 37 degrees C, and maintained 95% viability of encapsulated cultured disk cells. The gel did not produce an inflammatory reaction when injected subcutaneously into C57BL/6 mice and is therefore biocompatible. Most importantly, when injected into the degenerated nucleus pulposus of human cadaveric intervertebral disk, the gel flowed into the clefts without leakage. This study demonstrates that 2.5% Protasan UP G213 cross-linked to 5% genipin might be a promising scaffold for disk tissue engineering.

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