A Novel Rat Model to Study Postsurgical Pain After Joint Replacement Surgery.

Area of Science:

• Orthopedic Surgery
• Pain Research
• Animal Models

Background:

• Chronic postsurgical pain after joint replacement (JR) is complex and may stem from inadequate acute pain management.
• Few studies utilize specific animal models to investigate acute pain following JR.

Purpose of the Study:

• To develop a novel JR animal model for assessing postsurgical pain.
• To evaluate the time course of pain recovery and associated molecular changes after JR.

Main Methods:

• A rat model involving sham surgery, joint destruction (JD), and JR with a custom implant was used.
• Postsurgical pain was measured via dynamic weight-bearing, radiological assessment, and dorsal root ganglion (DRG) calcitonin gene-related peptide-immunoreactive (CGRP-IR) neuron evaluation.

Main Results:

• Weight-bearing function in the JR group recovered to sham levels by day 42, significantly outperforming the JD group after day 7.
• Radiological assessment revealed no major complications, only transient implant migration.
• The percentage of CGRP-IR DRG neurons was significantly lower in the JR group compared to the JD group at days 28 and 42.

Conclusions:

• The novel JR model effectively demonstrated acute postsurgical pain that resolved by day 42.
• Differences in pain manifestation between JR and JD groups correlate with CGRP-IR neuron expression.
• This model provides a foundation for further research into the mechanisms of post-JR pain.