Evaluation of Intersomatic Arthrodesis With and Without Ligature of Segmentary Vessels: An Experimental Study in Rabbits

Abstract from the SRS 2004 Annual Meeting

Introduction: Correct vascularization is mandatory in the process of bone reparation. The risk of nonconsolidation increases in the absence of adequate vascular support. Knowledge about the optimum conditions under which intersomatic bone reparation develops successfully is useful to prepare the fusion area to obtain the best bone callus quality in the shortest period of time.

Objectives:

1. to describe the natural history of intersomatic vertebral consolidation in rabbits.

2. to assess if absence of unilateral segmentary vascularization modifies the process of intersomatic bone consolidation.

Study Design: Descriptive comparative experiment model designed to assess intersomatic fusion in rabbits.

Material and Methods: Eighteen rabbits were randomly divided into two groups. In group A, intersomatic arthrodesis was performed preserving the segmentary vessels. In group B, the same procedure was performed with ligature of the segmentary vessels contiguous with the fusion area. Each group was divided into three subgroups that were sacrificed at 4, 8 and 12 weeks respectively. The samples were studied clinically, radiologically and anatomo-pathologically.

Results: At 4 weeks, group A showed an intersomatic union that annulled movement. A similar union was found in group B at 8 weeks. Radiological evidence of intersomatic consolidation, however, was not found in either group until 8 weeks. Both groups showed clinical and radiological evidence of bone consolidation at 12 weeks. Radiologically, however, group A presented greater size and density of the intersomatic callus than group B. Histopathologically, it was observed that group B, unlike group A, went through an exuberant stage of neovascularization occupying the intersomatic space. At 12 weeks, group A presented mature bone tissue whereas group B presented immature bone tissue with osteoid tissue and numerous blood vessels.

Conclusions:

Objective 1: The natural history of intersomatic vertebral consolidation in rabbits is the following: at 4 weeks of evolution, there is a union that annuls intersomatic movement but is not radiologically visible. At 12 weeks, clinical, radiological and anatomo-pathological evidence of intervertebral consolidation exists.

Objective 2: Deprivation of unilateral segmentary vascularization negatively alters the process of bone formation for intersomatic fusion. Clinically, radiologically and anatomo-pathologically observed alterations support this hypothesis.