Effectiveness of Posterolateral Lumbar Fusion Varies with the Physical Properties of Demineralized Bone Matrix Strip

STUDY DESIGN: A randomized, controlled animal study. PURPOSE: To investigate the effectiveness of fusion and new bone formation induced by demineralized bone matrix (DBM) strips with jelly strengths. OVERVIEW OF LITERATURE: The form of the DBM can make a difference to the outcome. The effect of different jelly strengths on the ability of DBM to form new bone is not known. METHODS: Forty-eight rabbits were randomized into a control group and two experimental groups. In the control group (group 1), 1.4 g of autologous iliac crest bone was placed bilaterally. In the experimental groups, a high jelly strength DBM-hyaluronic acid (HA)-gelatin strip (group 2) and a low jelly strength DBM-HA-gelatin strip (group 3) were used. The fusion was assessed with manual manipulation and radiographs. The volume of the fusion mass was determined from computed tomographic images. RESULTS: The fusion rates as determined by manual palpation were 37.5%, 93.8% and 50.0% in group 1, group 2, and group 3, respectively (p<0.05). By radiography, the fusion rate of High jelly strength DBM strip was statistically significantly greater than that of the other alternatives (p<0.05). The mean bone volume of the fusion mass as determined by computed tomography was 2,142.2+/-318.5 mm3, 3,132.9+/-632.1 mm3, and 2,741.5+/-380.4 mm3 in group 1, group 2, and group 3, respectively (p<0.05). CONCLUSIONS: These results indicate that differences in the structural and mechanical properties of gelatin that are associated with jelly strength influenced cellular responses such as cell viability and bony tissue ingrowth, facilitating greater bone fusion around high jelly strength implants.

Development of an Intervertebral Disc Degeneration Model using Newzealand White Rabbits

STUDY DESIGN: An experimental animal study. OBJECTIVES: To create a more appropriate disc degeneration model which shows how Interleukin 1alpha may induce the activation of metalloproteinases within the nucleus pulposus. SUMMARY OF LITERATURE REVIEW: There are few disc degeneration models wherein there is activation of metalloproteinases within the nucleus pulposus without structural destruction of the intervertebral disc. MATERIALS AND METHODS: Three consecutive intervertebral discs in New Zealand White Rabbits were exposed. Each disc was injected with 0.1ml of saline (Saline group), 0.1ml of 1microg/ml (IL-1 group), 0.1ml of 10microg/ml (IL-10 group) of IL-1alpha through a 30-gauge needle. The lumbar spine was harvested 12 weeks after operation. We then analyzed radiographic findings and histological changes. RESULTS: There was no difference in the radiological disc height index among the three groups; 0.071 in saline group, 0.045 in IL-1 group and 0.058 in IL-10 group (p=0.194). The histological cellularity of the nucleus pulposus revealed a decrease in the number of cells (p=0.0001, 1.42 in saline group vs. 3.00 in IL-10 group; p=0.001, 2.00 in IL-1 group and 3.00 in IL-10). The histological matrix of the nucleus pulposus was 1.42 in saline group and 2.42 in IL-10(p=0.007), which meant that there had been condensation of the extracellular nucleus pulposus matrix. CONCLUSIONS: The results of this study demonstrate that interleukin-1alpha may contribute to degradation of the nucleus pulposus. This is useful for future study into the effects of the cytokine inhibitor on matrix regeneration and cellularity in the nucleus pulposus in intervertebral disc disease.