Biomedical subjects

J U Yoo

Publications and source records attributed to J U Yoo.

28 records · Page 2Linked to original sources

PubMed1995

The role of distraction in improving the space available for the cord in cervical spondylosis.

STUDY DESIGN: This study analyzed the effects of distraction via strut graft insertion on the canal dimensions in spondylotic human cadaver cervical spines. Transverse and anteroposterior diameters and cross-sectional areas were measured by transverse computed tomography imaging before and after distraction without direct decompression. OBJECTIVES: This experiment was designed to address whether distraction across the disc space without direct canal decompression can improve the space available for the cord. SUMMARY OF BACKGROUND DATA: Smith-Robinson anterior discectomy and fusion have been shown to improve clinical symptoms of radiculopathy and myelopathy even in the absence of direct decompression. This has been postulated to be the result of gradual resorption of intruding osteophytes. However, the immediate effects of indirect distraction alone have not been previously investigated. METHODS: Four cadaver spines from elderly donors were harvested intact. The transverse diameter, anteroposterior diameter, and cross-sectional area of the spinal canal were measured before and after discectomy and distraction via insertion of fibular strut graft by digitization of contiguous computed tomography scan slices. RESULTS: The spinal canal dimensions before distraction were found to vary in a sinusoidal pattern around the disc space, with the maximum measurements located at the pedicle and the minimum measurements at the spondylotic ridge above or below the disc space. Distraction via strut graft insertion significantly increased the anteroposterior diameter and cross-sectional area, but had a negligible effect on transverse diameter. CONCLUSIONS: Anterior discectomy and distraction with a strut graft can significantly improve the space available for the cord in cervical spondylosis. Osteophyte debridement, which risks iatrogenic injury to the cord, may not always be necessary for improving clinical radiculopathy and myelopathy.

Aged↗

PubMed1993

Review of Harrington rod treatment of spinal trauma.

Harrington rod treatment for spinal trauma has become the gold standard against which other treatment modalities are judged. A review of the results of Harrington rod treatment is essential to establish a baseline level of efficiency in terms of rehabilitation time, correction of deformity, canal decompression, motion segment loss, and device-related complications. With economic concerns becoming more important in medical treatment, the value of newer techniques must be clearly superior to established methods. Harrington rod-augmented spine fusion is reliable and cost-effective in the thoracic and thoracolumbar spine. The risks of rod failure and late complications related to lost motion segments in the lumbar spine make pedicle screw systems a better option in this region.

Biomechanical Phenomena↗

PubMed1993

Mechanics of anatomic reduction of thoracolumbar burst fractures. Comparison of distraction versus distraction plus lordosis, in the anatomic reduction of the thoracolumbar burst fracture.

The adequate reduction of vertebral burst fractures is dependent on successful application of distractive forces in combination with the restoration of normal spinal lordosis. However, the optimal sequence of distraction in comparison to distraction plus lordosis in the anatomic restoration of the fractured thoracolumbar spine has not been described. Burst fractures of the L1 vertebra were first created and the reduced in vitro using three differing reduction techniques. In six fresh human cadaver spine specimens, the mean fracture severity based on the degree of canal compromise was 31% (SD +/- 20%) after fracture. Reductions were performed using the AO Fixator Intern, the Reduction Fixation (RF) Device, and the Steffee plate systems following standard clinical techniques. The AO Fixator Intern provided independent but variable control of distraction and lordosis, the RF device provided variable distraction with independent, but preset, correction of lordosis and the Steffee system provided set distraction and stabilization. Both the AO and RF devices restored the lordosis (7.6 degrees +/- 5.2 degrees and 9.7 degrees +/- 4.5 degrees, respectively) better than the Steffee plate system (0 degrees +/- 1.6 degrees). However, the AO device provided poorest restoration of the posterior vertebral body height (92% vs 96% for the RF device and 99% for the Steffee plate). The RF device, which restored both lordosis and posterior vertebral body height to the near anatomic prefracture level, provided significantly better canal clearance (9% +/- 8%) than the other techniques, P < 0.05. The study demonstrates that instrumentation systems that provide independent correction of distraction and lordosis can best restore anatomic alignment, with indirect neurodecompression of the compromised spinal canal.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

Suppression of proteoglycan synthesis in chondrocyte cultures derived from canine intervertebral disc.

Chondrocytes were dissociated enzymatically from canine nucleus pulposus. After attaining monolayer growth, the cells were subpassaged and incubated with sodium salicylate, indomethacin, or sodium meclofenamate (10(-2) M to 3 x 10(-6) M). When incubated with nonsteroidal anti-inflammatory drug concentrations mimicking therapeutic plasma levels, proteoglycan synthesis was significantly suppressed. After 24 hours of incubation, there was a 15% decrease in radioactive sulfate (35SO4) incorporation for salicylate (10(-3) M), a 29% decrease for indomethacin (3 x 10(-6) M), and a 75% decrease for sodium meclofenamate (10(-5) M). This inhibition was both dose- and time-dependent. Despite the effect of these nonsteroidal anti-inflammatory drugs on quantitative proteoglycan synthesis, there was no demonstrable effect of these drugs on the size of proteoglycan monomers or the degree to which proteoglycan aggregate formation occurred.

Animals↗

PubMed1992

Effect of cervical spine motion on the neuroforaminal dimensions of human cervical spine.

A nerve root impingement within a stenotic neuroforamen is a common sequela of cervical degenerative arthritis and herniated nucleus pulposus. Understanding of the effects of cervical position on foraminal size is important in the assessment of pathology and injury, for selection of a provocative maneuver to elicit symptoms and in selecting a position of immobilization for the management of nerve root impingement syndrome. This biomechanical study of human cadaver cervical spines reports the measured variations in the sizes of neuroforamina as a function of cervical positioning. Five fresh frozen adult human cadaver cervical spines (C2-T1) were tested with combinations of flexion-extension and rotational position. Ten pounds of axial load was applied to simulate a normal loading of a cervical spine. The foramina of C5, C6, and C7 were directly measured using a set of finely graded circular probes. Compared to the foraminal diameter at the neutral position, there were statistically significant reductions in the foramen diameter of 10% and 13%, at 20 degrees and 30 degrees of extension respectively (P < 0.01). Conversely, in flexion, there were statistically significant increase of 8% and 10% at 20 degrees and 30 degrees of flexion respectively (P < 0.01). Though there was a reduction in the foraminal size with ipsilateral 20 degrees rotation, and an increase with contralateral 20 degrees rotation, these changes were not significantly different from the mean of the control. Combinations of flexion or extension position with axial rotation did not significantly change the foraminal size compared to the respective sagittal position with no axial rotation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1988

Evidence that a humoral immune response to autologous cartilage proteoglycan can participate in the induction of cartilage pathology.

We examined antiproteoglycan antibodies as an autoimmune response for induction of synovitis. This hypothesis was studied by monitoring humoral antiproteoglycan antibody following IgG induction of experimental immune synovitis, localization in the articular cartilage of an autologous immune response, and loss of proteoglycan from cartilage following intravenous administration of antiproteoglycan monoclonal antibodies. The data support the hypothesis that autoimmunity to cartilage macromolecules may play a role in the etiopathogenesis of arthritis.

Animals↗

PubMed1988

Analysis of experimental immune synovitis cartilage using monoclonal antibodies reactive to rabbit proteoglycan.

This study details the macromolecular changes in cartilage involving proteoglycan molecules in an animal model of rheumatoid arthritis. In experimental chronic immune synovitis, fluorescein-conjugated mouse IgG and three monoclonal antibodies (MAbs 2G2, 2E9, and 6C9) portraying differing fine antigenic specificity for rabbit cartilage proteoglycan monomer were utilized to detail alterations in cartilage proteoglycan. In normal and IgG-immune animals, fluorescein isothiocynate (FITC)-conjugated MAbs 2G2 and 2E9 stained cellular/pericellular (C/PC) region intensely. FITC-MAb 2G2 stained cartilage interterritorial matrix as well. FITC-MAb 6C9 stained only C/PC area lightly but did not stain matrix. A marked decrease in staining intensity with FITC-MAb 2G2 was noted in cartilage sections derived from animals with immune synovitis. A corresponding increase in staining of cartilage was noted with FITC-MAb 6C9. The augmented staining of articular cartilage with FITC-MAb 6C9 was most prominent in femoral condyle tissue sections, which corresponded to the cartilaginous area, with the greatest severity in gross pathology. There was a slight augmentation of staining with FITC-MAb 2E9, especially in the C/PC area of medial/femoral cartilage. In addition, the animals with immune synovitis showed abortive cartilage repair exemplified by the presence of chondrocyte cloning (up to 20 cells) which correlated with increased FITC-MAb 2G2 staining. The differential MAb staining patterns of cartilaginous tissues obtained utilizing FITC-conjugated monoclonal antibodies with known fine antigenic specificity indicates a modulation of proteoglycans involving predominantly core protein epitopes in the articular cartilage of animals with chronic immune synovitis.

Animals↗

PubMed1987

Epitopes of proteoglycans eliciting an anti-proteoglycan response in chronic immune synovitis.

This study details the immune response to cartilage proteoglycan in experimental chronic IgG-induced immune synovitis. Antibodies reactive with purified rabbit proteoglycan monomer were observed in nine of nine rabbits with immune synovitis. IgG-immunized but nonsynovitic control animals with no pathology showed no antibody response. A panel of murine monoclonal antibodies with defined specificity towards rabbit proteoglycan were utilized to characterize the epitope specificity of the immune synovitis polyclonal anti-proteoglycan response. One murine monoclonal antibody, 6C11, inhibited the binding of the polyclonal antisera to proteoglycan in all nine animals with significant (greater than 40%) inhibition in six of nine rabbits. Further inhibition studies utilizing DEAE-cellulose-resolved proteoglycan tryptic peptides revealed that peptides poor in chondroitin sulfate were strong inhibitors of binding of the polyclonal antibodies to the proteoglycan substrate. In particular, keratan sulfate-containing tryptic peptides were most inhibitory on a per weight basis. These results indicate that, in chronic IgG-induced immune synovitis, anti-proteoglycan antibodies elicited are heterogeneous with regard to specificity, but a relatively large proportion predominantly recognized a portion of the proteoglycan molecule containing core protein and associated keratan sulfate.

Animals↗

PubMed1987

Structural characteristics of articular cartilage proteoglycan in IgG induced experimental immune synovitis.

The early changes (five weeks) in the structure of newly synthesised and endogenous articular cartilage sulphated proteoglycans were studied in lapine IgG induced experimental immune synovitis. Rabbits with immune synovitis (IS-IgG) were compared with animals with a developed hypersensitivity to IgG (I-IgG) and with non-treated normal weight matched controls. Medial and lateral femoral condyle and tibial plateau cartilage was pooled and radiolabelled for 24 h in vitro with 35SO4. The samples constituted tissue from regions underlying pannus and from pannus free sites. Cartilage from animals with IS-IgG showed a significantly diminished amount of newly synthesised and endogenous proteoglycan aggregate and an increased amount of hydrodynamically small proteoglycans. Newly synthesised (obtained by in vivo radiosulphate labelling) and endogenous proteoglycans showed a similar profile. The proteoglycan monomer fraction from animals with IS-IgG failed to form proteoglycan aggregates in the presence of excess hyaluronic acid. In the group with IS-IgG linear regression analysis showed a statistically significant relationship between the synovial pathology scores (but not cartilage pathology score) and diminished newly synthesised and endogenous proteoglycan aggregate.

Animals↗

PubMedDate not supplied

High variability in rabbit bone marrow-derived mesenchymal cell preparations.

The rabbit has been extensively used for preclinical models, especially in orthopedic applications. One of the more troubling features of this model is the high interindividual variability that is encountered and that requires a careful experimental design with sufficient sample size to make judgments valid. We have processed 241 individual preparations of rabbit bone marrow-derived mesenchymal progenitor cells (MPCs) over the last 3 years and have kept detailed records of the performance of these cells in various assays. This communication details the lack of correlation between the analyzed parameters. Bone marrow was harvested from 4-month-old rabbits; the cells were centrifuged, resuspended, and cultured. When cells reached 80% of confluence, they were removed from the plates with trypsin and assayed for their osteo- and chondrogenic potential. The average yield of the 241 individual MPC preparations exhibited a coefficient of variation of 77. An in vivo implantation assay with porous calcium phosphate ceramic cubes exhibited scores with a coefficient of variation of 65. Lastly, an in vitro assay of alkaline phosphatase enzyme activity exhibited the most variability with a coefficient of variation of 132. All of the cell preparations tested in an in vitro aggregate culture assay underwent chondrogenic differentiation. No relationships between any of these parameters were found. The variability of the results within the different assays is interpreted to be the result of the heterogeneity of the preparations. The lack of correlation between the parameters studied shows the importance of the conditions intrinsic to the different assays. These results serve to emphasize that any experimental design involving rabbit progenitor cells must include a sufficiently large sample size to allow statistically significant and rigorous conclusions.

Alkaline Phosphatase↗