Schaefer S L, Ciarelli M J, Arnoczky S P, Ross H E
Laboratory for Comparative Orthopaedic Research, College of Veterinary Medicine, Michigan State University, East Lansing 48824, USA.
Am J Sports Med. 1997 Nov-Dec;25(6):841-8. doi: 10.1177/036354659702500619.
The effect of laser energy on the length, stiffness, and structure of connective tissue was examined in a rabbit patellar tendon model. A holmium:yttrium-aluminum-garnet laser was used to deliver a calculated dose of laser energy (300 J/cm2) to one randomly selected patellar tendon in each of 13 adult New Zealand White rabbits. The contralateral patellar tendon was used as a control. Radiopaque markers were placed in the patella and tibial tuberosity to allow for patellar tendon length measurements (via standard lateral radiographs) before and after laser application and at 4 and 8 weeks. Limbs were not immobilized during the postoperative period. The tendons were harvested at 0 weeks (N = 7) and 8 weeks (N = 6) and evaluated for tensile, stiffness, cross-sectional area, histologic changes, and electron microscopic appearance. The results demonstrated significant tendon shrinkage (6.6% +/- 1.4%) after application of the calculated laser energy dose. However, tendon length had increased significantly beyond the immediate postlaser length at 4 weeks and beyond its original length by 8 weeks. At 8 weeks, the lased tendons were significantly less stiff with significantly greater cross-sectional areas than contralateral controls. There was generalized fibroblastic response throughout the entire lased tendon characterized by a marked increase in cellularity. There was also a change from the normal bimodal pattern of large- and small-diameter collagen fibers to a unimodal pattern with predominantly small-diameter fibers in the lased tendons. The tissue alterations seen in this study suggest that the biologic response of connective tissue to laser energy causes a further compromise in tissue integrity, beyond that attributed to the initial physical effects of the laser. These alterations must be taken into consideration when determining postoperative rehabilitation of laser-modified tissues.
在兔髌腱模型中研究了激光能量对结缔组织长度、刚度和结构的影响。使用钬：钇铝石榴石激光向13只成年新西兰白兔每只的一条随机选择的髌腱输送计算剂量的激光能量（300 J/cm²）。对侧髌腱用作对照。在髌骨和胫骨结节处放置不透射线的标记物，以便在激光照射前、照射后以及4周和8周时（通过标准侧位X线片）测量髌腱长度。术后期间肢体未固定。在0周（N = 7）和8周（N = 6）时采集肌腱，并评估其拉伸性能、刚度、横截面积、组织学变化和电子显微镜外观。结果表明，施加计算剂量的激光能量后，肌腱明显收缩（6.6%±1.4%）。然而，在4周时肌腱长度显著增加，超过激光照射后的即时长度，到8周时超过其原始长度。在8周时，接受激光照射的肌腱刚度明显降低，横截面积明显大于对侧对照。整个接受激光照射的肌腱出现普遍的成纤维细胞反应，其特征是细胞数量显著增加。在接受激光照射的肌腱中，胶原纤维的正常双峰模式（大直径和小直径）也转变为主要为小直径纤维的单峰模式。本研究中观察到的组织改变表明，结缔组织对激光能量的生物学反应会导致组织完整性进一步受损，超出激光最初物理效应所致的范围。在确定激光改性组织的术后康复方案时，必须考虑这些改变。
