Osteogenic ability of free periosteal autografts in tibial fractures with severe soft tissue damage: an experimental study.

OBJECTIVE: The present study was undertaken to assess whether free nonvascularized autologous periosteum transplants enhance bone healing in a rabbit fracture model designed to resemble a tibial fracture with severe soft tissue damage.

DESIGN: Transplantation of free autologous periosteal grafts on the anteromedial site of the tibia (experimental group) was compared with nontransplantation on the contralateral tibia (control group). We produced a standardized transverse osteotomy of both tibial diaphyses in white male adult New Zealand rabbits. The endomedullary cavity was reamed and nailed, and then a one-centimeter segment of periosteum was excised from either side of the osteotomy. To prevent periosteal and extraosseous ingrowth at the osteotomy site, a silastic sheet was wrapped around two-thirds of the circumference of the tibia. In the first group, on the silastic-free bone window, we then spanned the osteotomy with a free, nonvascularized, longitudinally oriented autologous periosteum and sewed it to the adjacent periosteum both proximally and distally. In the second group, the periosteum was placed transversely, leaving a gap between it and the adjacent periosteum proximally and distally. Revascularization of the graft was determined with the colored microsphere technique.

MAIN OUTCOME MEASUREMENTS: Histomorphometric analysis of the periosteal callus was done on a transparent grid superimposed on enlarged photographs of the histologic sections.

RESULTS: Free, nonvascularized, longitudinally placed autologous periosteum in contact with intact periosteum produced significantly more periosteal callus than was seen in the control group, in which no periosteal graft was used. However, when transversely placed periosteal grafts were set in the silastic-free bone window and there was no contact with surrounding remnants of intact periosteum, no significant difference in callus production was noted when compared with the control. Revascularization of these grafts was seen within one week after transplantation. Bone healing occurred mainly through endochondral ossification.

CONCLUSION: Our data suggest that orthotopically placed autologous nonvascularized periosteum retains its osteogenic potential in a poorly vascularized environment such as a tibial fracture with severe soft tissue damage. The effect is enhanced if the graft is in contact with intact periosteum. Histologically, callus formation after periosteal grafting resembles endochondral and intramembranous ossification.