Experimental Study of Spinal Reconstruction Using Bioabsorbable Material

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Objectives of the study were to evaluate the validity and advantage of forged composite of uncalcined hydroxyapatite Poly L-Lactite cage (F-u-HA/PLLA) radiographically, biomechanically, and histlogically when compared to conventional autologousiliac bone (AM) and carbon fiber cage (CFC). Twenty-five mature sheep underwent posterior lumbar interbody fusion at L2-3 level with pedide screw system. Three types of interbody fusion implants were grafted : AIB (n=7), CFC (n=9), F-u-HA/PLLA((n=9). Two types of cages were packed with autologous fragmented cancellous bone harvested locally. All animals were euthanized at 120 days after surgery. The fusion scoreing using the coronal view CT scans was designed to three dimentionally evaluate fusionquality within and around cages. The meen CT scores of threee groups were 33.3 points, 35.0 points, 33.6 points in AIB, CFC, and F-u-HA/PLLA cage groups, respectively (full-score : 56 points). Statistical differences were not detected among the three groups. The mean range of motion values among fused groups had no significant diffierence under all pure moment loadings. The range of motion showed strong and significant correlation with the CT fusion scores. Histologic results demonstrated that F-u-HA/PLLA cages contacted with the surrounding bone directly, and CFC was encircled with thick fibrous tissue layrs without any sign of inflammation around cages. The fusion quality of fused spinal segment using F-u-HA/PLLA cages was equal to that of AIB or CFC both radiographically and biomechanically. In the histological observation, biocompatibility of F-u-HA/PLLA cage was obviously superior to CFC. It has been confirmed that the novel bioactive and bioabsorbable cages had valuable advantages over existing CFC for use in spinal re constructive surgery.