STUDY DESIGN: An in-vivo experiment. OBJECTIVES: To compare the results of various methodologies for an annulotomy, and evaluate the relationship between the degenerative change and the volume of an extruded nucleus according to the various methodologies. SUMMARY OF LITERATURE REVIEW: Many authors have reported that the traditional annulotomy technique is an open annulotomy. MATERIAL AND METHODS: 16 female white New Zealand rabbits, each weighing about 4-4.5 kg, were used. A retroperitoneal approach, using a paravertebral incision, was used. Using a number 11 blade, a 21G needle and a number 15 blade, transverse stab incisions, or puncture wounds, were made into the L3-4, L4-5 and L5-6 disc through the antero-lateral annulus. At all the experimental levels, a complete annulotomy, which confirms the leakage of nucleus pulposus after an annulotomy, was used. To check the extruded nucleus volume after each annulotomy, the gross findings and histological findings of 10 disc samples from each level were analyzed. Radiological methods were used simple lumbar x-ray and MRI. From simple x-rays, the change in the disc height was measured with NIH image software, and the degeneration grade was classified using MRI. RESULTS: The gross and histological findings showed the most advanced degeneration in the number 15 blade annulotomy group (L5-6 level), with the simple radiographs showing a fast decrease in the disc height. From the MRI findings, early degenerative findings were observed 2 months after the annulotomy in the number 11 and 15 blades groups. The largest extruded nucleus volume was observed in the number 15 blade annulotomy group. CONCLUSION: In conclusion, the degenerative change in the disc, following an annulotomy, was related to the volume of the extruded nucleus.
Animals* ; Female ; Humans ; Intervertebral Disc Degeneration* ; Magnetic Resonance Imaging ; Needles ; Punctures ; Rabbits ; Wounds and Injuries

STUDY DESIGN: An in-vivo experiment. OBJECTIVES: To evaluate the feasibility of achieving bone formation by percutaneous gene delivery, with plasmid DNA encoding BMP-7(OP-1). SUMMARY OF LITERATURE REVIEW: Currently, the preferred method for posterolateral spinal fusion involves decortication of the transverse process, followed by a graft of autogenous bone harvested from the iliac crest. Unfortunately, this procedure suffers from significant morbidity, including blood loss, infection and persistent pain at the harvest site. MATERIAL AND METHODS: 24 Sprague-Dawley rats, weighing approximately 250~300 g, were used. The percutaneous injection was attempted above both the L5 transverse processes. The animals were divided into three groups, according to the injection materials: 1) OP-1 gene/collagen, 2) recombinant OP-1 protein/collagen and 3) control of PBS/collagen. At 2 and 4 weeks post-injection, the animals were sacrificed. The gross, radiological and histological findings were analyzed. RESULTS: No bone was detected grossly by manual palpation or radiography in the groups receiving OP-1 gene/collagen at either time point. The histological findings revealed the initiation of endochondral bone formation within the paraspinal muscle, directly above the L5 transverse process. In the rhOP-1 protein/collagen groups, the gross, radiological and histological findings revealed extensive cartilage and bone formation at both 2 and 4 weeks. CONCLUSION: In conclusion, the authors confirmed the feasibility of achieving bone formation by percutaneous gene delivery, with plasmid DNA encoding BMP-7(OP-1).
Animals ; Cartilage ; DNA ; Osteogenesis ; Palpation ; Paraspinal Muscles ; Plasmids ; Radiography ; Rats, Sprague-Dawley ; Spinal Fusion* ; Transplants

PURPOSE: To develop an animal disc degeneration model. MATERIALS AND METHODS: 12 female 8-month-old white New Zealand rabbits, weighing about 4-4.5 kg, were used. A retroperitoneal approach using a paravertebral incision was adopted. Using a number-11 blade, a transverse stab incision was made into the L3-4 and L5-6 disc through the antero-lateral annulus. At L3-4 level, complete annulotomy was performed and incomplete annulotomy at the L5-6 level. In the complete annulotomy group, extrusion of the nucleus after annulotomy was confirmed. Gross and histological findings, and lumbarx-rays and MRIs were analyzed. From simple x-rays, changes in disc heights were measured using NIH image software; degeneration grade was classified using MRI. RESULTS: The gross and histological findings showed progressive degenerative change in both groups, which were more severe in the complete annulotomy group. Simple radiographs showed a progressive decrease in the disc height and osteophyte formation in several samples, which were more severe in the complete annulotomy group. From the MRI findings, early degenerative findings were identified 2 and 3 months after complete and incomplete annulotomy, respectively. CONCLUSION: In conclusion, the disc degenerative process, following incomplete annulotomy, more resembled the natural course of disc degeneration than complete annulotomy.
Animals ; Female ; Humans ; Infant ; Intervertebral Disc Degeneration ; Intervertebral Disc* ; Magnetic Resonance Imaging ; Osteophyte ; Rabbits