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Abstract
Purpose
An experimental animal study was performed to compare the bone fusion capacity of an allograft and porous hydroxyapatite.
Materials and Methods
Three milliliters of allograft or porous hydroxyapatite particles were inserted between the 4th and 5th lumbar transverse processes of New Zealand white rabbits weighing 3-3.5 kg. The total number of rabbits was 30, which were divided randomly into 2 groups. The bone formation and fusion capacity were evaluated 12 weeks after surgery through the gross findings and manual palpation, as well as radiological, biomechanical, and histological studies. Six rabbits in the allograft group died during breeding but the autopsy finding did not show any evidence suggesting an infection or graft rejection. The allograft was harvested from the iliac crest of the rabbits of the same species aseptically and was preserved at -80℃ for at least 7 days before implantation.
Results
The fusion rates were 55.6% (5/9) and 66.7% (10/15) in the allograft and porous hydroxyapatite groups, respectively. The mean values of the tensile strengths were 140.7 N in the allograft group and 189.6 N in the porous hydroxyapatite group. Histological analysis of 2 specimens from each group revealed theporous hydroxyapatite group to show a slightly better osteoconduction capacity.
Figures and Tables
Fig. 2
Serial posteroanterior radiographs. In both groups, implanted allograft and hydroxyapatite granules showed marginal blurring at 6 weeks, however, the radioopacities of the centers of the granules was sustained for up to 12 weeks.
Fig. 3
Light microscopic findings of the fusion masses in the allograft group (H&E stain, ×100, decalcified). (A) Case 1. The allograft was transformed to mature bone including the osteoid formation with osteoblastic rim, newly formed bone marrow and intervening fibrous tissue. (B) Case 2. Newly formed bone and fibrous tissue are intermingled.
Fig. 4
Light microscopic findings of the fusion masses in the porous HA group (H&E stain, ×100, decalcified). (A) Case 1. Remodeling of new bone containing osteoid, bone marrow, and the surrounding new vessels can be observed within the pores. (B) Case 2. It shows a mixture of new vessels, osteoid, and bone marrow within the pore structure along the remodeled bone suggesting excellent osteoconduction.
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