Proceedings of the NASS 20th Annual Meeting / The Spine Journal 5 (2005) 1S–189S12S

Fig. 2.

DISCLOSURES: FDA device/drug: parathyroid hormone (1–34). Status:Not approved for this indication.CONFLICT OF INTEREST: No conflicts.

doi: 10.1016/j.spinee.2005.05.024

12:0024. Effect of lumbar disc space narrowing on intervertebralforaminal dimensionsJiayong Liu, Nabil Ebraheim, MD, Haitham Elsamaloty, MD,Nakul Karkare, MD, Richard Yeasting, PhD, Lisa Storer, RT(R)CT; Medical College of Ohio, Toledo, OH, USA

BACKGROUND CONTEXT: A distinct clinical feature of lumbar degen-erative disc diseases is disc space narrowing. Although several studies havedemonstrated the effects of segmental compression and distraction onthe cross-sectional area of the neuroforamen, there is lack of quantitativedata on the magnitude of reduction in the lumbar foraminal area following1 mm incremental disc space narrowing.PURPOSE: To quantify changes of the cross sectional neuroforaminalareas following the different degree of narrowing of disc space.STUDY DESIGN/SETTING: Computer-assisted simulation of L34 andL45 disc space narrowing was performed on reconstructed computerized to-mography in 20 cadaveric lumbar spines.PATIENT SAMPLE: N/A.OUTCOME MEASURES: N/A.METHODS: Twenty cadaver lumbar spine specimens without any historyof other spinal pathology except some degrees of degenerative changeswere used for the study. Computed tomography scans of each specimenwere taken with 1-mm slice thickness, at 1-mm intervals. Reconstructed

11:5423. The relative contributions of the end plate permeabilityto disc degenerationAzucena Rodriguez, BS, David Bradford, MD, Jeffrey Lotz, PhD;University of California, San Francisco, San Francisco, CA, USA

BACKGROUND CONTEXT: The cartilaginous end plate and the sub-chondral bone play important roles in regulating nutrient diffusion into thedisc. Decreased end plate permeability has been hypothesized as an im-portant mechanism of disc degeneration by restricting cell nutrition. Thisinterface may also hinder attempts at biologic disc repair that requireincreased nuclear cell metabolism to enhance matrix synthesis. Yet,there are no data that define the optimal end plate permeability, or therelative contributions of the cartilage and bony portions. These dataare critical to assess the potential for disc repair and to design strategiesfor permeability enhancement.PURPOSE: To directly measure the hydraulic permeability of humanvertebral end plate and relate this to other specimen-specific variables.STUDY DESIGN/SETTING: We harvested intervertebral cores that in-cluded the subchondral bone, cartilage end plate, and adjacent nucleus.Then, we correlated direct measurements of hydraulic permeability to sub-chondral bone architecture, nucleus cellularity, and overall disc degeneration.PATIENT SAMPLE: Eight human cadaveric specimens ranging 16 to 79years old.OUTCOME MEASURES: The hydraulic permeability, subchondral boneporosity, nuclear cellularity and disc degeneration status were measured.METHODS: Cylindrical intervertebral cores centered along the vertebralcentrum were harvested from frozen human spines (16 to 79 years). Speci-mens consisting of end plate cartilage and subchondral bone were isolated.The hydraulic permeability was measured using a custom made permeame-ter, both before and after removing the cartilage end plate. Nucleus cellu-larity was quantified by measuring DNA content. In addition, specimenswere imaged using microCT, and end plate porosity was calculated alongwith several other measures of bony architecture (Fig. 1).

Fig. 1. Schematic of end plate specimen harvest.

RESULTS: Hydraulic permeability for the intact specimens ranged from6.18×10–12 m2/Pa-s to 1.82×10–13 m2/Pa-s. The permeability of the bonyportion of the end plate was linearly related to the porosity and age. Nuclearcellularity was inversely correlated to the end plate permeability. Withage and degeneration, the bony end plate became more permeable whilethe cartilage end plate became less permeable.CONCLUSIONS: These data are consistent with prior measurements ofend plate strength that demonstrate mineralization decreases with degenera-tion. Our results also suggest that the cartilage end plate should be the targetfor future attempts to enhance disc nutrition that should be included withtissue engineering approaches at nuclear regeneration.DISCLOSURES: No disclosures.CONFLICT OF INTEREST: No conflicts.

doi: 10.1016/j.spinee.2005.05.025