Biomechanical analyses on effects of stress deprivation on the mechanical properties of the frozen anterior cruciate ligament.

1. 我们开发了一种螺旋冷冻探针，其中液氮循环进行犬前交叉韧带（ACL）的原位冷冻。为了了解冷冻探针的能力，我们冷冻了4只成年狗的acl。冷冻后用显微镜观察和细胞培养检测活细胞。冷冻前交叉韧带未见活细胞。结果表明原位冷冻可使aol的成纤维细胞全部死亡。用专门设计的螺旋卵巢探针原位冷冻28只成熟比格犬的ACLs。所有成纤维细胞死亡后，用生理盐水解冻acl。每个人工骨在线的胫骨插入是用一个圆柱形骨块穿过一个空心铰刀从胫骨中取出的。这些狗被分成两组。第一组解剖复位骨块（假手术组）。在第二组，通过将骨块向近端移位3mm完全放松人工在线（放松组）。更重要的是，每个骨块都用干涉螺钉固定牢固。观察Sham组和Relax组原位冷冻acl的力学性能和超微结构的变化。仅在12周时，Relax组的AOL横截面积明显大于Sham组。松弛组各时间段的抗拉强度和切线模量均显著低于Sham组。两组在各时段的失败应变无显著差异。对4只狗的ACLs进行了超微结构分析。术后6周，Sham组成纤维细胞进入原位冷冻前交叉韧带的浅表物质，而Relax组卵形核细胞进入*物质空间。12周时，各组人工血管实质均可见成纤维细胞，Sham组进入细胞核呈梭形，Relax组进入细胞核呈卵圆形。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 4 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 AOL.2. The ACLs of the 28mature beagle dogs were frozen in situ with the specially designed helical oryoprobe. After all fibroblasts died, the ACLs were thawed out with physiological saline. The tibial insertion of each AOL was made tree 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 (Sham group). At the second group, the AOL was completely relaxed by translocating the bone block to the proximal direction by 3 mm (Relax group). Th … More en, the each bone block was firmly fixed with an interference screw. The differences of the in situ frozen ACLs between the Sham and the Relax groups were investigated about the changes of mechanical properties and ultrastructure.3. The cross sectional area of the AOL in Relax group was significantly greater than that in Sham group only at 12 weeks. The tensile strength and the tangent modulus in Relax group were significantly lower than that in Sham group at each period. There were no significant differences in the strain at failure between the two groups at each period.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 Sham group, although cells with oval nucleus entered into the *tersubstancial space in the Relax group. At 12 weeks, the fibroblasts were found at all the substance of the AOL in each group, although the shape of the nucleus of entered cell was spindle in the Sham group and oval in the Relax group. Less