School of Health Sciences, Faculty of Life and Health Sciences, Ulster University, Jordanstown campus, Newtownabbey, UK.
Division of Public Health Science, School of Health Sciences, Mid Sweden University, Sundsvall, Sweden.
BMC Musculoskelet Disord. 2023 Jun 22;24(1):511. doi: 10.1186/s12891-023-06653-x.
Mechanical loading is purported to restore ligament biomechanics post-injury. But this is difficult to corroborate in clinical research when key ligament tissue properties (e.g. strength, stiffness), cannot be accurately measured. We reviewed experimental animal models, to evaluate if post-injury loading restores tissue biomechanics more favourably than immobilisation or unloading. Our second objective was to explore if outcomes are moderated by loading parameters (e.g. nature, magnitude, duration, frequency of loading).
Electronic and supplemental searches were performed in April 2021 and updated in May 2023. We included controlled trials using injured animal ligament models, where at least one group was subjected to a mechanical loading intervention postinjury. There were no restrictions on the dose, time of initiation, intensity, or nature of the load. Animals with concomitant fractures or tendon injuries were excluded. Prespecified primary and secondary outcomes were force/stress at ligament failure, stiffness, laxity/deformation. The Systematic Review Center for Laboratory animal Experimentation tool was used to assess the risk of bias.
There were seven eligible studies; all had a high risk of bias. All studies used surgically induced injury to the medial collateral ligament of the rat or rabbit knee. Three studies recorded large effects in favour of ad libitum loading postinjury (vs. unloading), for force at failure and stiffness at 12-week follow up. However, loaded ligaments had greater laxity at initial recruitment (vs. unloaded) at 6 and 12 weeks postinjury. There were trends from two studies that adding structured exercise intervention (short bouts of daily swimming) to ad libitum activity further enhances ligament behaviour under high loads (force at failure, stiffness). Only one study compared different loading parameters (e.g. type, frequency); reporting that an increase in loading duration (from 5 to 15 min/day) had minimal effect on biomechanical outcomes.
There is preliminary evidence that post-injury loading results in stronger, stiffer ligament tissue, but has a negative effect on low load extensibility. Findings are preliminary due to high risk of bias in animal models, and the optimal loading dose for healing ligaments remains unclear.
机械加载据称可以恢复受伤后的韧带生物力学。但在临床研究中，当关键的韧带组织特性（例如强度、刚度）无法准确测量时，这很难得到证实。我们回顾了实验动物模型，以评估受伤后加载是否比固定或卸载更能有利地恢复组织生物力学。我们的第二个目标是探讨加载参数（例如加载的性质、幅度、持续时间、频率）是否会影响结果。
我们于 2021 年 4 月进行了电子和补充检索，并于 2023 年 5 月进行了更新。我们纳入了使用受伤动物韧带模型的对照试验，其中至少有一组在受伤后接受了机械加载干预。加载的剂量、开始时间、强度或性质均不受限制。同时伴有骨折或肌腱损伤的动物被排除在外。预先指定的主要和次要结果是韧带断裂时的力/应力、刚度、松弛度/变形。使用实验室动物实验系统评价中心工具来评估偏倚风险。
共有 7 项符合条件的研究；所有研究的偏倚风险都很高。所有研究均使用手术诱导大鼠或兔膝关节内侧副韧带损伤。有 3 项研究记录了有利于受伤后自由活动（与卸载相比）的较大影响，表现在 12 周随访时的断裂力和刚度。然而，在受伤后 6 和 12 周时，负载韧带在初始募集时的松弛度更大（与未加载相比）。有两项研究的结果表明，将结构化运动干预（每日短时间游泳）加入自由活动中，进一步增强了韧带在高负荷下的行为（断裂力、刚度）。只有一项研究比较了不同的加载参数（例如类型、频率）；报告说，加载持续时间（从 5 分钟/天增加到 15 分钟/天）对生物力学结果的影响很小。
有初步证据表明，受伤后加载会导致更强、更硬的韧带组织，但会对低负荷伸展性产生负面影响。由于动物模型的高偏倚风险，这些发现尚属初步，愈合韧带的最佳加载剂量仍不清楚。
