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

1.研制了液氮循环螺旋冷冻探头，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，我们冻结了12只成年狗的前交叉韧带。冷冻后，取韧带进行光镜观察和细胞培养，检测活细胞。冷冻后的前交叉韧带内未见活细胞，证明原位冷冻可使前交叉韧带成纤维细胞全部死亡。用特制的螺旋冷冻探头原位冷冻20只成年比格犬的前交叉韧带。所有成纤维细胞死亡后，用生理盐水解冻前交叉韧带。每个前交叉韧带的胫骨附着点通过穿透中空扩孔器用圆柱形骨块从胫骨中分离出来。狗被分成两组。第一组：解剖复位骨块(生理张力组：P组)。在第二组，通过将骨块拉到di…上，对前交叉韧带施加20N的初始张力张力计使胫骨止点向远端移位(高张力组：H组)。然后，用干涉螺丝钉将每个骨块牢牢固定。比较P组和H组原位冷冻人工晶状体的力学性能和超微结构的差异。术后6周，P组和H组的力学性能差异无统计学意义。12周时，H组的抗拉强度、最大载荷和切线弹性系数均显著低于P组(p&lt；0.05)。断裂时的横截面积和应变均无显著差异。对4只犬的前交叉韧带进行了超微结构分析。术后6周，P组有成纤维细胞进入冰冻前交叉韧带表层，而H组有炎性细胞进入基质间隙。12周时，P组前交叉韧带内可见全部成纤维细胞，而H组可见成纤维细胞变性改变。较少

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