Session IV Scientific Basis for Fracture Care


Saturday, September 28, 1996 Session IV, 10:10 a.m.

Biological Implementation of Autologous Foreign Body Membranes in Consolidation of Massive Cancellous Bone Grafts

Kaj Klaue, MD, Ulf Knothe, MD, Christoph Anton, Alain C. Masquelet, MD, Stephan Perren, MD

AO Development Institute (ADI), Davos, SWITZERLAND

Hypothesis: Complex skeletal trauma and/or fractures complicated with infection and necrosis may result in massive bone loss. Cancellous bone graft is often resorbed. Creating an autologous foreign body membrane with a temporary spacer may improve the local conditions for cancellous bone graft.

Materials and Methods: A mid-diaphyseal 3 cm long whole bone defect (bone and periosteum) was performed in the left femur of 30 sheep. The defect was replaced by a customized methyl-metacrylate block. A broad 8 hole plate with 6 screws was applied to splint the bone defect. Four weeks later, 26 sheep, organized in 4 groups, were operated on a second time. Through a limited approach at the bridged bone defect, the spacer was removed with or without the newly-formed foreign body membrane and autologous cancellous bone graft interposed or not.

group A: membrane

group B: no membrane

graft group C: membrane, no graft

graft group D: no membrane, no graft

Sixteen weeks after the second operation, the sheep were sacrificed and the femurs radiologically and histologically evaluated.

Results: 8 sheep had to be sacrificed earlier for various reasons. Four sheep of group A, 5 sheep of group B, 5 sheep of group C and 4 sheep of group D reached histological investigation at 20 weeks. The results were marked by the frequent implant failure (3 cases) in sheep of group D showing no new bone formation. The sheep of group C showed bone formation beginning at the osteotomy site and at the bony side of the membrane. However, in no sheep did the defect consolidate. Sheep of group B showed bone graft being resorbed at the level of the plate. This resorption reached in some cases the mid-width of the femur. Also, density of cancellous bone (integration) within the previous defect seems to be less than in group A. Those sheep (group A) all demonstrated sound consolidation without bone loss and in full diameter. The quantity of new formed bone was significantly different between all groups A, B, C and D. Tubulisation of the bone grafted area was not seen at this stage.

Discussion: The method allowed differentiation between the effects of bone graft and foreign body membrane. The mechanical environment of all operated groups were identical after the second operation as the mechanical strength of fresh bone graft can be neglected. Considering group A in which cancellous bone graft was placed within the "bag" provided by the well vascularized foreign body membrane and group B in which the bone graft was partially resorbed brings up two possible explanations: either the foreign body membrane acts as a pure protection against resorption factors (e.g. muscular origin) or the membrane induces bone formation by producing some unknown bone growth factors. Considering group C, in which bone grows into the "empty" bone defect and group D in which no new bone is observed in the same conditions demonstrates the local potential of bone for regeneration. However, no further conclusion upon eventual biochemical implementation of the foreign body membrane may be drawn. This might be the subject of further investigations.

Conclusion: Inducing a foreign body membrane to encapsulate cancellous bone graft showed a strikingly positive effect upon consolidation of long bone defects.