ENHANCED HEALING OF SEGMENTAL TIBIAL DEFECTS IN SHEEP BY A COMPOSITE BONE SUBSTITUTE COMPOSED OF TRICALCIUM PHOSPHATE CYLINDER, BONE MORPHOGENETIC PROTEIN, AND TYPE-IV COLLAGEN

Diaphyseal segmental defects in the tibia of 18 sheep were used to eva luate the healing potential of a composite bone substitute device (CBS ) composed of a tricalcium phosphate cylinder (TCP), naturally occurri ng sheep bone morphogenetic protein (sBMP), and type IV collagen. A to tal of 100 mg of sBMP and 20 mg of type IV collagen in the high-dose g roup (CBSH), and 13 mg of sBMP and 2.5 mg of type IV collagen in the l ow-dose group (CBSL) were adsorbed to TCP cylinders, respectively. TCP cylinders impregnated with type IV collagen alone (TCPC) were used as control. A significantly larger area and more highly integrated inten sity of newly formed external callus between CBSH and CBSL or TCPC gro up were quantified by computerized image analyzer at both 3 and 6 week s. A torsion test showed that the maximal torque capacity, maximal ang ular deformation, and bone stiffness of healed osteotomized tibia with implants recovered 117-125% in CBSH, 72-109% in CBSL, and 63-80% in T CPC, compared with the corresponding contralateral tibia at 16 weeks. A healing superiority of the segmental bone defects replaced by the im plants was demonstrated in the CBSH group. Thus, the composite bone su bstitute device defined in this study was shown to possess osteoinduct ivity, osteoconductivity, and mechanical strength. (C) 1996 John Wiley & Sons, Inc.