The Biodynamical Survey And Histologica Investigation On Tendon-bone Healing After Reconstruction Of Anterior Cruciate Ligament In Rabbits

Objective Explore the reconstruction method of anterior cruciate ligament in rabbits for promoting tendon-bone healing. Make autologous tendon as a donor to reconstruct anterior cruciate ligament(ACL)in the induce of bone morphogenetic protein (BMP) with the help of deproteined bone(DPB) . according to the results of preliminary studies of this subject-BMP can promote repairs of the tendon-bone interface in histology after ACL reconstruction, we need to confirm the complex can enhance the strength of tendon-bone healing from biomechanical testing and histological investigation. Under the premise of eventuating injury and complications as less as possible, We offerd experimental basis for clinical application in ACL reconstruction.Methods Sixty-four New Zealand and white rabbits were randomly divided into four groups, including BMP+DPB group, BMP group, DPB group and blank control group. After cutting off the normal ACL and established the model of ACL reconstruction with semitendinosus tendon autograft, put BMP+DPB,BMPandDPB into the bone tunnel respectively. Specimens were taken at 3, 6, 12, 24 weeks after operation for tensile test and histological investigation, recording the tensile force as the bone-graft-bone complex breaking, then we analysed the data by statistics. Observed the fracture location and histological structure of cross-section of grafts and tendon-bone interface, using haematoxylin-eosin (HE) staining to observe change of tissue of grafts.Results Three weeks,twelve weeks and twenty-four weeks after operation, biomechanical testing was found that the average load of BMP+DPB when the grafts were ruptured incompletely was significantly greater than the BMP group, DPB group and blank control group, the difference was of statistical significance; Six weeks after operation, the average load of BMP+DPB group and BMP group when the grafts were ruptured incompletely was of no significant difference(P>0.05), while the BMP group was of greater load than the DPB group and blank control group (P<0.05). There was no significant difference among BMP group,DPB group and blank control group at other time after operation. The average load of BMP+DPB group when the grafts were ruptured completely was greater than the DPB group and blank control group (P<0.01), the difference was of statistical significance. Six weeks after operation, the average load of BMP+DPB group was of statistical significance compared with BMP group(P<0.05). But the BMP group was significantly greater than the DPB group and blank control group (P<0.05)when the grafts were ruptured completely. There was no significant difference among BMP group,DPB group and blank control group at other time after operation. Three weeks after operation, histological observation was found that graft rupture sites of DPB group and blank control group were in the femoral tunnels, only fibrous tissue was detected, BMP group and BMP +DPB group were located at the tunnel mouth, a little of cartilage-like tissue can be seen in the stump; Six weeks after operation, graft rupture sites of DPB group and blank control group were at the tunnel mouth, fibrous tissue was around the stump, graft rupture sites of BMP group and BMP+DPB group were in the intra-articular, some cartilage-like tissue was found; Six weeks after operation, graft rupture sites of all groups were located in the intra-articular, there were a large number of collagen fibers can be seen, Collagen fibers of blank control group and DPB group were irregularly arranged, but they were regular of BMP group and BMP+DPB group, fibrocartilage cells were found markedly increased; Twenty-four weeks after operation, all the grafts rupture sites were located in the middle of intra-articular graft or around enthesis, collagen fibers were neatly and regularly arranged of BMP+DPB group and BMP group, there were more short rod-shaped and oval-shaped cells were detected in BMP+DPB group. The collagen fibers of DPB group and blank control group were more regular than former, no cartilage cells were found.Conclusions 1,In the model of ACL reconstruction, BMP had effect in accelerating tendon bone healing, this effect was enhanced under the help of DPB. 2,The strength of graft enhanced with induce of BMP. 3,DPB reduced the wear between graft and runnel, playing an important role as screw fixation. 4,Because of the acceleration of tendon bone healing, graft rupture site changed from femoral tunnel to intra-articular. 5,At different time, the morphologies of the rupture site of grafts were significantly different, collagen fibers gradually with the rules.