Biomechanical analyzes on effects of change of initial tension on the mechanical properties of the frozen anterior cruciate ligament in the dog.

1.我们研制了一种液氮循环的螺旋形冷冻探针，用于犬前交叉韧带（ACL）的原位冷冻。为了了解冷冻探针的能力，我们冷冻了12只成年狗的头部。冷冻后行显微镜观察及细胞培养检测活细胞。结果：1.冷冻前交叉韧带中未发现活细胞，证明原位冷冻可杀死前交叉韧带的所有成纤维细胞.用自行设计的螺旋形冷冻探针对20只成年Beagle犬的胚胎进行原位冷冻。所有成纤维细胞死亡后，用生理盐水解冻。通过穿入空心扩髓钻，用圆柱形骨块将每个ACL的胫骨插入点从胫骨上分离。将狗分为两组。第一组为解剖复位的骨块（生理张力组：P组）。在第二组中，通过将骨块拉到远端，在ACL上施加20 N的初始张力。 ...更多信息 用张力计向胫骨方向施加张力，导致胫骨止点远端移位（高张力组：H组）。然后，用界面螺钉牢固固定每个骨块。研究P组和H组原位冷冻组织力学性能和超微结构变化的差异.术后6周，P组和H组之间的力学性能无显著差异。另一方面，在12周时，H组的拉伸强度、最大载荷和切线模量显著低于P组（p<0.05）。横截面积和断裂应变无显著性差异.对4只狗的睾丸进行了超微结构分析。术后6周，P组成纤维细胞进入原位冷冻ACL表面，H组炎性细胞进入ACL间隙。12周时，P组ACL的所有物质均可见成纤维细胞，而H组ACL的物质发生退行性改变。少

1. We developed helical cryoprobe in which liquid nitrogen was circulated to perform in situ freezing of the canine anterior cruciate ligament (ACL). To know the ability of the cryoprobe we froze the ACLs of 12 adult dogs. After freezing, the ligaments were investigated with microscope and cell culture to detect living cell. No living cell was found in the frozen ACL.It was proved that the in situ freezing killed all fibroblasts of the ACL.2. The ACLs of the 20 mature beagle dogs were frozen in situ with the specially designed helical cryoprobe. After all fibroblasts died, the ACLs were thawed out with physiological saline. The tibial insertion of each ACL was made free from the tibia with a cylindrical bone block by penetrating a hollow reamer. The dogs were divided in two groups. At the first group, the bone block was reduced anatomically (physiological tension group : P group). At the second group, an initial tension of 20 N was applied on the ACL by pulling the bone block to the di … More stal direction with a tensiometer, resulting in distal translocation of the tibial insertion (high tension group : H group). Then, the each bone block was firmly fixed with an interference screw. The differences of the in situ frozen ACLs between the P and the H groups were investigated about the changes of mechanical properties and ultrastructure.3. There were no significant differences in the mechanical properties between the P and the H groups at 6 weeks after surgery. On the other hand, the tensile strength, maximum load and the tangent modulus in the H group were significantly lower than those in the P group at 12 weeks (p<.05). No significant differences could be found in thecross sectional area and in the strain at failure.4. The ACLs of four dogs were analyzed ultrastructurally. At 6 weeks after surgery, fibroblasts entered into the superficial substance of the in situ frozen ACL in the P group, although inflammatory cells entered into the intersubstancial space in the H group. At 12 weeks, the fibroblasts were found at all the substance of the ACL in the P group, although the degenerative change of the substance was found in the H group. Less