IEEE Trans Ultrason Ferroelectr Freq Control. 2021 Sep;68(9):2981-2986. doi: 10.1109/TUFFC.2021.3075375. Epub 2021 Aug 27.
Around 30 million tendon injuries occur annually in the U.S. costing $ 114 billion. Conservative therapies, like dry needling, promote healing in chronically injured tendons by inducing microdamage but have mixed success rates. Focused ultrasound (fUS) therapy can noninvasively fractionate tissues through the creation, oscillation, and collapse of bubbles in a process termed histotripsy; however, highly collagenous tissues, like tendon, have shown resistance to mechanical fractionation. This study histologically evaluates whether fUS mechanical disruption is achievable in tendons. Ex vivo rat tendons (45 Achilles and 44 supraspinatus) were exposed to 1.5-MHz fUS operating with 0.1-10 ms pulses repeated at 1-100 Hz for 15-60 s with peak positive pressures <89 MPa and peak negative pressures <26 MPa; other tendons were exposed to dry needling or sham. Immediately after treatment, tendons were flash-frozen and stained with hematoxylin and eosin (H&E) or alpha-nicotinamide adenine dinucleotide diaphorase ( α -NADH-d) and evaluated by two reviewers blinded to the exposure conditions. Results showed successful creation of bubbles for all fUS-treated samples; however, not all samples showed histological injury. When the injury was detected, parameter sets with shorter pulses (0.1-1 ms), lower acoustic pressures, or reduced treatment times showed mechanical disruption in the form of fiber separation and fraying with little to no thermal injury. Longer pulses or treatment times showed a combination of mechanical and thermal injury. These findings suggest that mechanical disruption is achievable in tendons within a small window of acoustic parameters, supporting the potential of fUS therapy in tendon treatment.
美国每年约有 3000 万例肌腱损伤,造成的损失达 1140 亿美元。保守疗法,如干针疗法,通过诱导微损伤来促进慢性损伤的肌腱愈合,但成功率不一。聚焦超声(fUS)疗法可以通过在一个称为组织碎裂的过程中创建、振荡和崩溃气泡来非侵入性地分割组织;然而,像肌腱这样高度胶原化的组织对机械分割表现出抵抗力。本研究从组织学上评估 fUS 机械破坏是否可在肌腱中实现。离体大鼠肌腱(45 个跟腱和 44 个冈上肌腱)用 1.5MHz 的 fUS 处理,脉冲重复 1-100Hz,持续时间为 15-60s,正压峰值<89MPa,负压峰值<26MPa;其他肌腱用干针或假处理。治疗后立即将肌腱用闪冻法固定,用苏木精和伊红(H&E)或α-烟酰胺腺嘌呤二核苷酸脱氢酶(α-NADH-d)染色,由两位对暴露条件不知情的审阅者进行评估。结果显示,所有 fUS 处理的样本均成功地产生了气泡;然而,并非所有样本都显示出组织损伤。当检测到损伤时,具有较短脉冲(0.1-1ms)、较低声压或较短治疗时间的参数集显示出纤维分离和磨损的机械破坏,几乎没有热损伤。较长的脉冲或治疗时间显示出机械和热损伤的组合。这些发现表明,在小的声学参数窗口内,机械破坏可在肌腱中实现,支持 fUS 疗法在肌腱治疗中的潜力。