A Experimental Research Of Segmental Radial Defects In Rabbits Repaired By L-arginine Supplementation

Objective:Freeze dried bone allografts were implanted in rabbits' 10mm mid-radius defects models.In order to research the effect of L-arginine supplementation to repair the segment bone defects and explore their mechanism. Methods:Making freeze dried bone allografts,10mm segmental bone and periosteum defects were created in 40 New Zealand rabbits on bilateral radius and were treated with 4 different metheds:the L-Arg group,20 rabbits,left radius(A group),freeze dried allograft bones were implantedï¼›right radius(B group),nothing was implanted as control. 0.9%Nacl group,20 rabbits, left radius (C group),freeze dried allograft bones were implantedï¼›right radius (D group),single autograft bones(from right radius)were implanted. After operation, rabbits in the arginine supplement group orally administrated 1.1g of L-Arg daily,however 0.9% Nacl group administrated 1.1ml 0.9% Nacl in the same manner.The repaires of defects were observed through body looking by naked eyes, radiology,the bone mineral density (BMD) in bone defects and histologic sections at 2,4,8,12 week after operationsï¼›NO and Alkaline Phosphatase(AKP) densities were measured in serum at 1 day before operations and 2,4,8,12 week after operations; biomechanical tests were made only at 12 week. Results:L-Arg group and 0.9% Nacl group have no obvious immunal transplanting rejection.The serum NO levels were higher in L-arg group than Nacl group at the same periods(P<0.01), The serum AKP levels were higher in L-arg groups than in Nacl group at 2,4,8 week after operations (P<0.01). The serum AKP level reached maximum at 4 week after operations and decreased to 2 week's level at 8 week after operations. Two groups had no obvious difference at 12 week after operations .All radius detects were healed in A,C,D groups at 12 week. But Callus and new bone formation, cartilage ossification, formation of marrow cavity in A group were earlier than in C groups. A group radius were repaired more thoroughly in 12 week than C group after operation. A groups's radiogrophs were close to D groups' . B group only formed a little new bone at edges of bone defects and filled with some soft tissue, and could not healing at 12 week. The BMDs in A group were obviously higher than C group at 2 week and 4 week(P<0.01) and were lower than D group at the same periods and the difference at 2 week and 4 week had statistical significance(P<0.01 and P<0.05). Histological examinations showed that vascular formation, osteoblast differentiation and proliferation, callus formation and remolding etc were all earlier than C group at the same periods, and had no obvious difference to D group. The defects treated with B group could not get osseous-tissue healing. The biomechanical test at 12 week results also showed maximum stresses of three points curving were higher in groups A than in group C(P<0.05), and had no obvious difference to D group. Conclusions: L-Arg that is transformed into NO in body can effectively repair segmental bone defects that have been implanted with freeze dried bone allografts.