Rat Model of Adhesive Capsulitis of the Shoulder

Summary

This protocol presents an in vivo rat model of adhesive capsulitis. The model includes an internal fixation of the glenohumeral joint with extra-articular suture fixation for an extended time, resulting in a decreased rotational range of motion (ROM) and increased joint stiffness.

Abstract

This proposal aims to create an in vivo rat model of adhesive capsulitis for researching potential treatment options for this condition and other etiologies of comparable arthrofibrosis. The model includes extra-articular fixation of the shoulder in rats via scapular to humeral suturing, resulting in a secondary contracture without invading the intra-articular space and resulting in decreased rotational ROM and increased joint stiffness.

We used 10 Sprague-Dawley rats for the purpose of this study. Baseline ROM measurements were taken before glenohumeral immobilization. The rats were subjected to 8 weeks of immobilization before the fixation sutures were removed and changes in ROM and joint stiffness were evaluated. To evaluate whether immobilization resulted in a significant reduction in ROM, changes in kinematics were calculated. ROM was measured at each time point in the follow-up period and was compared to the baseline internal and external ROM measurements. In order to evaluate the stiffness, joint kinetics were calculated by determining the differences in torque (t_ext and t_int ) needed to reach the initial external rotation of 60° and initial internal rotation of 80°.

After the removal of the extra-articular suture fixation on follow-up day 0, we found a 63% decrease in total ROM compared to baseline. We observed continuous improvement until week 5 of follow-up, with the progress slowing down around a 19% restriction. On week 8 of follow-up, there was still an 18% restriction of ROM. Additionally, on follow-up day 0, we found the torque increased by 13.3 Nmm when compared to baseline. On week 8, the total torque was measured to be 1.4 ± 0.2 Nmm higher than initial measurements. This work introduces a rat model of shoulder adhesive capsulitis with lasting reduced ROM and increased stiffness.

Introduction

Adhesive capsulitis of the shoulder is frequently referred to as frozen shoulder or shoulder contracture. It is characterized by restricted glenohumeral motion and pain, presumably as a result of advanced fibrosis and joint contracture^1,2,3. The condition involves fibroblast and myofibroblast cell recruitment with a resultant dense collagen matrix (types I and III) in the joint capsule^2,3. There are many possible risk factors for developing a joint contracture, including gender, diabetes mellitus, hyperthyroidism, tra....

Protocol

The study was approved by the Institutional Animal Care and Use Committee at Beth Israel Deaconess Medical Center. Care was taken to avoid unnecessary prolonged anesthesia and also to avoid hypothermia. Animals were weighted at each ROM measurement session and monitored for weight loss.

1. Study Subjects

1. Use 10 Sprague-Dawley rats that are 13 weeks old at the time of surgery and that range between 250–300 g of body weight.

2. Surgical Procedure

1. Under anesthesia and before surgical immobilization, measure the baseline torque as a function of rotation angle between 60° of e....

Results

Range of motion

On follow-up day 0, we found a 63% decrease in total ROM compared to baseline (P < .001). We observed a gradual improvement of ROM until week 5 of follow-up, when progression stopped at 19% restriction (P <0.001). The remaining restriction, 18% of total ROM, was still apparent at 8 weeks of follow-up (P <0.001).

Stiffness

Discussion

This study presents a rat model of adhesive capsulitis of the shoulder through internal fixation of the glenohumeral joint. Furthermore, it shows an extended reduction of total ROM for at least 8 weeks after removal of the fixation. In order to calculate the alterations in ROM at different time points, measurements were compared to animal specific baselines. Conversely, Kanno et al.¹⁰ used a standardized torque for all of the animals in order to determine ex vivo ROM changes.......

Materials

Name	Company	Catalog Number	Comments
Sprague-Dawley rats	Charles River Laboratories, Wilmington, MA, USA		250-300 g
Surgical tool:
Injection needle			BD 1' 30 guage
Needle holder
5% isoflurane
2% isoflurane
Nose cone
Skalpel and skalpel holder			No. 11 scalpel
Curved hemostat forceps
Staright hemostat forceps
Tissue retractor
Toothed tissue forceps
Plain tissue forceps
Dissecting scissors
Suture scissors
Skin clip applicator			Any standard staples for wound closure
Immobilization material	Ethicon		No. 2-0 braided polyester ethibond suture was used for immobilization
Other materials:
Costumized device for ROM: 1)Sensor assembly, 2)pivoting axle, 3)arm clamp			Assembly that is described in relaxin paper and adhesive capsulitis paper
Orientation sensor (part of sensor assembly)	MicroStrain Inc., Williston, VT, USA		3DM-GX3-15
Reaction torque sensor (part of sensor assembly)	Futek Inc., Irvine, CA, USA		TFF400
Stepper Motor	SparkFun Electronics, Niwot, CO 80503		https://www.sparkfun.com/products/13656
Microcontroller	Torino, Italy).		Arduino UNO, R3
MATLAB code	MATLAB 7.13.0.564, Natick, Ma, USA
Weight Scale			Ohaus