VASCULARIZATION OF THE FUSION MASS IN A POSTEROLATERAL INTERTRANSVERSE PROCESS FUSION

Study Design. A previously characterized rabbit model was used to stud y vascularization of the fusion mass in a posterolateral intertransver se process fusion. Objectives. To determine the interosseus origin of the new blood vessels in a posterolateral intertransverse process fusi on mass and to test the hypothesis that bone incorporation and the ext ent of vascularization are closely related.Summary of Background Data, It has been reported that vascularization is essential for bone graft incorporation. There are, however, few reports dealing with vasculari zation of the spinal arthrodesis. Methods. Thirty-one adult New Zealan d White rabbits underwent bilateral intertransverse process fusion, us ing autogenous iliac crest bone graft. The rabbits were killed at 3 we eks (n = 6) and 6 weeks (n = 25) after surgery, and colored silicone w as injected to fix the vasculature. A semiautomated image analysis sys tem was used to assess the percentage of the area of vascularization i n the fusion mass and the transverse processes. Results. The major int erosseus blood supply for vascularization of the autogenous bone graft came from upper and lower transverse processes. There were three type s of fusion mass observed at 6 weeks after surgery: solid type, solid type with cartilaginous cleft, and nonunion type. There was significan tly less vascularization of the fusion mass and of the transverse proc esses in the nonunion type compared with that in the solid type and wi th that in the cartilaginous cleft type. Conclusions. There is a close correlation between bone incorporation and the extent of vascularizat ion in a posterolateral intertransverse process fusion.