Laboratory for Soft Tissue Research, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021, USA.
J Bone Joint Surg Am. 2010 Oct 20;92(14):2387-401. doi: 10.2106/JBJS.I.01270.
Modulation of the mechanical environment may profoundly affect the healing tendon graft-bone interface. The purpose of this study was to determine how controlled axial loading after anterior cruciate ligament reconstruction affects tendon-to-bone healing. Our hypothesis was that controlled cyclic axial loading after a period of immobilization would improve tendon-to-bone healing compared with that associated with immediate axial loading or prolonged immobilization.
One hundred and fifty-six male Sprague-Dawley rats underwent anterior cruciate ligament reconstruction with use of a flexor digitorum longus autograft. A custom-designed fixture was used to apply an external fixator across the knee parallel to the anterior cruciate ligament graft. Animals were randomly assigned to be treated with immobilization (n = 36) or controlled knee distraction along the long axis of the graft to achieve approximately 2% axial strain beginning (1) immediately postoperatively (n = 36), (2) on postoperative day 4 ("early delayed loading," n = 42), or (3) on postoperative day 10 ("late delayed loading," n = 42). The animals were killed at fourteen or twenty-eight days postoperatively for biomechanical testing, micro-computed tomography, and histomorphometric analysis of the bone-tendon-bone complex. Data were analyzed with use of a two-way analysis of variance followed by a post hoc Tukey test with p < 0.05 defined as significant.
Delayed initiation of cyclic axial loading on postoperative day 10 resulted in a load to failure of the femur-anterior cruciate ligament-tibia complex at two weeks that was significantly greater than that resulting from immediate loading or prolonged immobilization of the knee (mean and standard deviation, 9.6 ± 3.3 N versus 4.4 ± 2.3 N and 4.4 ± 1.5 N, respectively; p < 0.01). The new-bone formation observed in the tibial tunnels of the delayed-loading groups was significantly increased compared with that in the immediate-loading and immobilization groups at both two and four weeks postoperatively (1.47 ± 0.11 mm(3) [postoperative-day-10 group] versus 0.89 ± 0.30 mm(3) and 0.85 ± 0.19 mm(3), respectively, at two weeks; p < 0.003). There were significantly fewer ED1+ inflammatory macrophages and significantly more ED2+ resident macrophages at the healing tendon-bone interface in both delayed-loading groups compared with the counts in the immediate-loading and immobilization groups at two and four weeks (2.97 ± 0.7 [postoperative day 10] versus 1.14 ± 0.47 and 1.71 ± 1.5 ED2+ cells, respectively, per high-power field at two weeks; p < 0.02). The numbers of osteoclasts in the delayed-loading groups were significantly lower than those in the immediate-loading and immobilization groups at two and four weeks postoperatively (0.35 ± 0.15 [postoperative-day-10 group] versus 1.02 ± 0.08 and 1.44 ± 0.2 cells, respectively, per high-power field at two weeks; p < 0.01), and the delayed-loading groups also had significantly reduced interface tissue vascularity compared with the other groups (p < 0.003).
Delayed application of cyclic axial load after anterior cruciate ligament reconstruction resulted in improved mechanical and biological parameters of tendon-to-bone healing compared with those associated with immediate loading or prolonged postoperative immobilization of the knee.
机械环境的调节可能会对前交叉韧带重建后的愈合界面产生深远的影响。本研究的目的是确定在前交叉韧带重建后，施加何种方式的周期性轴向负荷会对腱骨愈合产生影响。我们的假设是，与即刻施加轴向负荷或膝关节长时间固定相比，在固定期后施加周期性轴向负荷可以改善腱骨愈合。
156 只雄性 Sprague-Dawley 大鼠接受了使用趾深屈肌腱重建前交叉韧带的手术。使用定制的固定装置在膝关节上施加一个外固定器，使其与前交叉韧带移植物平行。动物被随机分为固定组（n = 36）或在移植物的长轴上进行控制性膝关节分离以实现约 2%的轴向应变组（n = 36），该组又分为即刻开始（术后即刻开始，n = 36）、术后第 4 天（“早期延迟加载”，n = 42）或术后第 10 天（“晚期延迟加载”，n = 42）开始的亚组。在术后 14 天或 28 天处死动物，进行生物力学测试、微计算机断层扫描和骨-腱-骨复合体的组织形态计量学分析。使用双因素方差分析进行数据分析，随后进行事后 Tukey 检验，p < 0.05 为差异有统计学意义。
术后第 10 天开始延迟施加周期性轴向负荷会导致术后两周时股骨-前交叉韧带-胫骨复合体的失效负荷明显大于即刻负荷或膝关节长时间固定（分别为 9.6 ± 3.3 N、4.4 ± 2.3 N 和 4.4 ± 1.5 N；p < 0.01）。延迟加载组胫骨隧道内新骨形成量在术后两周和四周时均明显高于即刻加载和固定组（术后第 10 天组为 1.47 ± 0.11 mm3，而即刻加载和固定组分别为 0.89 ± 0.30 mm3 和 0.85 ± 0.19 mm3；p < 0.003）。与即刻加载和固定组相比，延迟加载组在术后两周和四周时，愈合腱骨界面处的 ED1+炎症性巨噬细胞数量明显减少，而 ED2+驻留巨噬细胞数量明显增加（2 周时，术后第 10 天组为 2.97 ± 0.7，而即刻加载和固定组分别为 1.14 ± 0.47 和 1.71 ± 1.5 ED2+细胞/高倍视野；p < 0.02）。延迟加载组在术后两周和四周时破骨细胞数量明显低于即刻加载和固定组（2 周时，术后第 10 天组为 0.35 ± 0.15，而即刻加载和固定组分别为 1.02 ± 0.08 和 1.44 ± 0.2 细胞/高倍视野；p < 0.01），并且延迟加载组的界面组织血管密度也明显低于其他组（p < 0.003）。
与即刻加载或膝关节长时间固定相比，在前交叉韧带重建后延迟施加周期性轴向负荷可改善腱骨愈合的力学和生物学参数。
