Basic Study
Copyright ©The Author(s) 2023. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Orthop. Sep 18, 2023; 14(9): 669-681
Published online Sep 18, 2023. doi: 10.5312/wjo.v14.i9.669
Formation process of extension knee joint contracture following external immobilization in rats
Chen-Xu Zhou, Feng Wang, Yun Zhou, Qiao-Zhou Fang, Quan-Bing Zhang
Chen-Xu Zhou, Feng Wang, Yun Zhou, Quan-Bing Zhang, Department of Rehabilitation Medicine, The Second Affiliated Hospital of Anhui Medical University, Hefei 230601, Anhui Province, China
Qiao-Zhou Fang, The Second Clinical Medicine College, Anhui Medical University, Hefei 230000, Anhui Province, China
Author contributions: Zhou CX conceived the study, participated in its design and coordination, and drafted the manuscript; Wang F participated in the design of the study and performed the statistical analyses; Zhou Y participated in its design and coordination, and helped to draft the manuscript; Fang QZ drew the pictures in the manuscript; Zhang QB performed the statistical analysis in the revised manuscript; All authors read and approved the final manuscript.
Supported by Anhui Key Research and Development Program-Population Health, No. 201904a07020067; Anhui Provincial Health Research Project, No. AHWJ2022b063; Clinical Medicine Discipline Construction Project of Anhui Medical University in 2022 (Clinic and Preliminary Co-Construction Discipline Project), No. 2022 lcxkEFY010; 2022 National Natural Science Foundation Incubation Plan, No. 2022GMFY05; Clinical Medicine Discipline Construction Project of Anhui Medical University in 2022 (High-Level Personnel Training Program), No. 2022 lcxkEFY04 and No. 2022 lcxkEFY05.
Institutional animal care and use committee statement: All animal experiments conformed to the internationally accepted principles for the care and use of laboratory animals (Anhui Medical University; protocol no. LLSC20221126, Experimental Animal Ethics Committee of Anhui Medical University, Anhui, China).
Conflict-of-interest statement: The authors have no conflicts of interest to declare.
Data sharing statement: No additional data are available.
ARRIVE guidelines statement: The authors have read the ARRIVE guidelines, and the manuscript was prepared and revised according to the ARRIVE guidelines.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Yun Zhou, MD, PhD, Chief Physician, Professor, Department of Rehabilitation Medicine, The Second Affiliated Hospital of Anhui Medical University, No. 678 Furong Road, Economic and Technological Development Zone, Hefei 230601, Anhui, China. zhouyunanhui@sina.com
Received: April 27, 2023
Peer-review started: April 27, 2023
First decision: June 14, 2023
Revised: June 30, 2023
Accepted: August 21, 2023
Article in press: August 21, 2023
Published online: September 18, 2023
Abstract
BACKGROUND

Current research lacks a model of knee extension contracture in rats.

AIM

To elucidate the formation process of knee extension contracture.

METHODS

We developed a rat model using an aluminum external fixator. Sixty male Sprague-Dawley rats with mature bones were divided into the control group (n = 6) and groups that had the left knee immobilized with an aluminum external fixator for 1, 2, and 3 d, and 1, 2, 3, 4, 6, and 8 wk (n = 6 in each group). The passive extension range of motion, histology, and expression of fibrosis-related proteins were compared between the control group and the immobilization groups.

RESULTS

Myogenic contracture progressed very quickly during the initial 2 wk of immobilization. After 2 wk, the contracture gradually changed from myogenic to arthrogenic. The arthrogenic contracture progressed slowly during the 1st week, rapidly progressed until the 3rd week, and then showed a steady progression until the 4rd week. Histological analyses confirmed that the anterior joint capsule of the extended fixed knee became increasingly thicker over time. Correspondingly, the level of transforming growth factor beta 1 (TGF-β1) and phosphorylated mothers against decapentaplegic homolog 2 (p-Smad2) in the anterior joint capsule also increased with the immobilization time. Over time, the cross-sectional area of muscle fibers gradually decreased, while the amount of intermuscular collagen and TGF-β1, p-Smad2, and p-Smad3 was increased. Unexpectedly, the amount of intermuscular collagen and TGF-β1, p-Smad2, and p-Smad3 was decreased during the late stage of immobilization (6-8 wk). The myogenic contracture was stabilized after 2 wk of immobilization, whereas the arthrogenic contracture was stabilized after 3 wk of immobilization and completely stable in 4 wk.

CONCLUSION

This rat model may be a useful tool to study the etiology of joint contracture and establish therapeutic approaches.

Keywords: Knee joint, Immobilization, Contracture, External fixator, Rats

Core Tip: Current research lacks a model of knee extension contracture in rats. The study elucidated the formation process and therapeutic strategies of knee extension contracture. To this end, we developed a rat model using an aluminum external fixator. The results showed that the myogenic contracture was stabilized after 2 wk of immobilization, whereas the arthrogenic contracture was stabilized after 4 wk of immobilization. This rat model may be a useful tool to study the etiology of the joint contracture and establish therapeutic approaches.