Aoyama Naoki, Izumi Masashi, Morimoto Toru, Wada Hiroyuki, Dan Junpei, Kasai Yusuke, Satake Yoshinori, Aso Koji, Ikeuchi Masahiko
Department of Orthopedic Surgery, Kochi Medical School, Kochi University, Nankoku, Japan.
J Pain Res. 2022 Sep 14;15:2911-2918. doi: 10.2147/JPR.S368130. eCollection 2022.
The mechanisms underlying chronic postsurgical pain after joint replacement (JR) are complex, and it has been suggested that chronic postsurgical pain can develop as a result of inadequate acute pain management. Few studies have addressed acute pain after JR using specific animal models. This study aimed to develop a novel JR model focused on postsurgical pain assessment and the time course of pain recovery.
Rats were allocated to the following three groups: sham (joint exposure), joint destruction (JD; resection of the femoral head), and JR (femoral head replacement using an originally developed implant). The time course of postsurgical pain behavior was measured using a dynamic weight-bearing apparatus, along with radiological assessments. The expression of calcitonin gene-related peptide-immunoreactive (CGRP-IR) neurons in the dorsal root ganglion (DRG) was evaluated by immunohistochemistry on days 28 and 42.
The ratio of weight-bearing distribution in the JR group gradually recovered from day 14 and reached the same level as that in the sham group on day 42, which was significantly greater than that in the JD group after day 7 (p<0.05). Radiologically, no significant issues were found, except for transient central migration of the implant in the JR group. The percentage of CGRP-IR DRG neurons in the JR group was significantly lower than that in the JD group on day 28 (mean, 37.4 vs 58.1%, p<0.05) and day 42 (mean, 32.3 vs 50.0%, p<0.05).
Our novel JR model presented acute postsurgical pain behavior that was successfully recovered to the baseline level at day 42 after surgery. Difference of the pain manifestation between the JR and JD groups could be supported by the expression of CGRP-IR in DRG neurons. This model is the first step toward understanding detailed mechanisms of post-JR pain.
关节置换术后慢性疼痛的潜在机制复杂，有人认为慢性术后疼痛可能是由于急性疼痛管理不足所致。很少有研究使用特定动物模型来研究关节置换术后的急性疼痛。本研究旨在建立一种新型的关节置换模型，重点关注术后疼痛评估和疼痛恢复的时间进程。
将大鼠分为以下三组：假手术组（关节暴露）、关节破坏组（JD；股骨头切除）和关节置换组（JR；使用自行研制的植入物进行股骨头置换）。使用动态负重装置测量术后疼痛行为的时间进程，并进行放射学评估。在术后第28天和第42天，通过免疫组织化学评估背根神经节（DRG）中降钙素基因相关肽免疫反应性（CGRP-IR）神经元的表达。
JR组的负重分布比例从第14天开始逐渐恢复，在第42天达到与假手术组相同的水平，显著高于JD组术后第7天的水平（p<0.05）。放射学检查发现，除JR组植入物有短暂的中心移位外，未发现明显问题。JR组DRG中CGRP-IR神经元的百分比在第28天（平均值分别为37.4%和58.1%，p<0.05）和第42天（平均值分别为32.3%和50.0%，p<0.05）显著低于JD组。
我们的新型JR模型呈现出术后急性疼痛行为，术后第42天成功恢复到基线水平。JR组和JD组疼痛表现的差异可通过DRG神经元中CGRP-IR的表达得到支持。该模型是理解关节置换术后疼痛详细机制的第一步。
