Introduction

Ultrasound-guided percutaneous cryoneurolysis provides analgesia using cold temperatures to reversibly ablate peripheral nerves. Cryoneurolysis probes pass a gas through a small internal annulus, rapidly lowering the pressure and temperature, forming an ice ball to envelope the target nerve. Analgesia is compromised if a nerve is inadequately frozen, and laboratory studies suggest that pain may be paradoxically induced with a magnitude and duration in proportion with the incomplete ablation. We therefore investigated the relative effects of various factors that may contribute to the size of the ice ball and the effective cryoneurolysis zone.

Methods

A cryoprobe was inserted into a piece of meat, a gas was passed through for 2 min, and the resulting ice ball width (cross-section) and length (axis parallel to the probe) were measured using ultrasound, with the temperature evaluated in nine concentric locations concurrently.

Results

The factor with the greatest influence on ice ball size was probe gauge: in all probe types, a change from 18 to 14 increased ice ball width, length, and volume by up to 70%, 113%, and 512% respectively, with minimum internal temperature decreasing as much as from −5 to −32 °C. In contrast, alternating the type of meat (chicken, beef, pork) and the shape of the probe tip (straight, coudé) affected ice ball dimensions to a negligible degree. The ice ball dimensions and the zone of adequate temperature drop were not always correlated, and, even within a visualized ice ball, the temperature was often inadequate to induce Wallerian degeneration.

Conclusions

Percutaneous probe design can significantly influence the effective cryoneurolysis zone; visualizing a nerve fully encompassed in an ice ball does not guarantee adequate treatment to induce the desired Wallerian degeneration because ice forms at temperatures between 0 and −20 °C, whereas only temperatures below −20 °C induce Wallerian degeneration. The correlation between temperatures in isolated pieces of meat and perfused human tissue remains unknown, and further research to evaluate these findings in situ appears highly warranted.

中文翻译：

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超声引导下经皮冷冻神经松解术中各种因素对冰球形成和消融区大小的相对影响：一项为临床实践和未来研究提供信息的实验室研究

介绍

超声引导下的经皮冷冻神经松解术利用低温可逆地消融周围神经来提供镇痛。冷冻神经溶解探针将气体穿过一个小的内部环，迅速降低压力和温度，形成一个冰球来包裹目标神经。如果神经冷冻不充分，镇痛效果就会受到影响，实验室研究表明，可能会矛盾地诱发疼痛，其程度和持续时间与不完全消融成比例。因此，我们研究了可能影响冰球大小和有效冷冻神经松解区的各种因素的相对影响。

方法

将冷冻探针插入一块肉中，通入气体 2 分钟，然后使用超声波测量所得冰球的宽度（横截面）和长度（与探针平行的轴），并以九分之一评估温度同时同心位置。

结果

对冰球尺寸影响最大的因素是探头规格：在所有探头类型中，从 18 变为 14 使冰球宽度、长度和体积分别增加最多 70%、113% 和 512%，最小内部温度从-5°C 降至-32°C。相比之下，交替改变肉类类型（鸡肉、牛肉、猪肉）和探针尖端的形状（直形、粗形）对冰球尺寸的影响可以忽略不计。冰球尺寸和足够温降的区域并不总是相关的，并且即使在可视化的冰球内，温度通常也不足以引起沃勒变性。

结论

经皮探头设计可以显着影响有效的冷冻神经松解区；可视化完全包围在冰球中的神经并不能保证充分治疗以诱导所需的沃勒变性，因为冰在 0 至 -20 °C 之间的温度下形成，而只有低于 -20 °C 的温度才会诱导沃勒变性。分离的肉块和灌注的人体组织的温度之间的相关性仍然未知，并且非常有必要进一步研究来评估这些发现的原位。