| Objective:To investigate the effect of plaster external fixation for bone-tendon junction healing after Patellar tendon rupture repair and to prove the healing effect of external fixation by experiments.Methods:36 adult New Zealand rabbits (18 wks) were randomly divided into two groups, the external fixation group (18 rabbits) and the control group (18 rabbits). Each group got the sample 2 wks (6 rabbits),4 wks (6 rabbits) and 8 wks (6 rabbits) after operation respectively. Modeling:We had a transverse osteotomy in the distal one third of the patellar. The connnection of apex patellae and patellar tendon was cut off. The fibrocartilage zone of patella and patellar tendon was cleared after the resection of distal one-third of the patella. We drilled two 0.8mm vertical holes in proximal patellar and sutured the patellar tendon to the patellar. We drilled holes below the tibial tuberosity in the junction area. "8" shaped tension wires were used to protect the structure. For the experimental group, the knees were fixed with plaster cast in the 90°position. The plaster was removed and the rabbits move free in the cage 3 wks later. For the control group, no cast immobilization and move free in the cage. All the samples were taken from the groups that contains 6 rabbits at 2 wks,4 wks and 8 wks respectively after operation. All the samples were used for doing biomechanical tests, including HE,Safranin'O and Masson staining and macrophages immunohistochemistry. The results were analyzed with statistics.Results:The tissue edema and adhesion at bone-tendon junction of external plaster fixation group was better than the control group, the external fixation group healed earlier than the control group. Biomechanical results displayed that the cross-section area of surgery group 4 wks after operation was 17.13±3.68 mm2 while that of control group was 22.74±4.18 mm2. The breaking load of surgery group was 76.05±9.16 N while that of control group was 61.69±8.56N. The ultimate tensile stress of surgery group was 5.23±0.93Mpa while the control group was 3.72±1.07Mpa. The cross-sectional area, tensile load and ultimate tensile stress between two groups had significant difference (P≤0.05). The cross-section area of surgery group 8 wks after operation was 14.65±3.27 mm2 while that of control group was 16.78±4.03 mm2. The breaking load of surgery group was 172.58±15.66 N while that of control group was 146.09±15.20 N. The ultimate tensile stress of surgery group was 14.26±2.02 Mpa while the control group was9.13±1.66 Mpa. Between two groups which have a significant difference(P≤0.05) in the cross-sectional area, tensile load and ultimate tensile stress. HE, Safranin'O and Masson staining results showed that bone-tendon junction of external plaster fixation group heals was good. The formation and arrangement of fibers of the fixation group was significant better than that of the control group. The immunohistochemical data revealed that the macrophages in external plaster fixation group were less than those of control group at 2,4 and 8 wks. The positive staining of macrophages showed that the absorbance value of the control group was higher than that of the fixation group. There was a significant difference between two groups (P≤0.05)Conclusion: We found External fixation could reduce the macrophages aggregation, promote the cell proliferation, differentiation and the cell matrix synthesis of bone-tendon junction and then let the bone-tendon junction heal better. |
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