We introduce a kinematic analysis method that uses a three-dimensional motion capture apparatus containing four cameras and data processing software for performing functional evaluations during fundamental research involving rodent models.
Compared to the Sciatic Functional Index (SFI), kinematic analysis is a more reliable and sensitive method for performing functional evaluations of sciatic nerve injury rodent models. In this protocol, we describe a novel kinematic analysis method that uses a three-dimensional (3D) motion capture apparatus for functional evaluations using a rat sciatic nerve crush injury model. First, the rat is familiarized with treadmill walking. Markers are then attached to the designated bone landmarks and the rat is made to walk on the treadmill at the desired speed. Meanwhile, the posterior limb movements of the rat are recorded using four cameras. Depending on the software used, marker tracings are created using both automatic and manual modes and the desired data are produced after subtle adjustments. This method of kinematic analysis, which uses a 3D motion capture apparatus, offers numerous advantages, including superior precision and accuracy. Many more parameters can be investigated during the comprehensive functional evaluations. This method has several shortcomings that require consideration: The system is expensive, can be complicated to operate, and may produce data deviations due to skin shifting. Nevertheless, kinematic analysis using a 3D motion capture apparatus is useful for performing functional anterior and posterior limb evaluations. In the future, this method may become increasingly useful for generating accurate assessments of various traumas and diseases.
The Sciatic Functional Index (SFI) is the benchmark method for carrying out functional sciatic nerve evaluations1. The SFI has been widely adopted and is frequently used within various functional evaluation studies on rat sciatic nerve injuries2,3,4,5,6. In spite of its popularity, there are several problems with SFI, including automutilation7, joint contracture risk, and smearing of the footprints8. These problems seriously affect its prognostic value9. Therefore, an alternative, less error-prone method is required as a substitute for the SFI.
One such alternative method is kinematic analysis. This includes comprehensive gait analysis using tracking markers attached to bony landmarks or joints. Kinematic analysis is increasingly used for functional evaluations9. This method is progressively being recognized as a reliable and sensitive tool for functional evaluation10 without the shortcomings attributed to the SFI11,12.
In this protocol, we describe a series of kinematic analyses that use a 3D motion capture apparatus consisting of a treadmill, four 120 Hz charged coupled device (CCD) cameras, and data processing software (see Table of Materials). This kinematic analysis method differs from general video walking or gait analysis13,14. Two cameras are positioned in different directions to record posterior limb movements from a single side. Subsequently, a 3D digital model of the posterior limb is constructed using computer graphics9. We can calculate designated joint angles, such as hip, knee, ankle, and toe joint, by closely recapitulating the actual limb dimensions. Additionally, we can determine various parameters such as stride/step length and the ratio of the stance phase to the swing phase. These reconstructions are based on a completely reconstructed 3D digital model of the posterior limbs, generated from data transmitted by two sets of cameras. Even the imaginary center of gravity (CoG) trajectory can be calculated automatically.
We used this 3D motion capture apparatus to introduce and assess multiple kinematic parameters that reveal functional changes over time within the context of the rat sciatic nerve crush injury model.
In this protocol, a stable and continuously walking rat is the most vital component of kinematic analysis. The treadmill speed was set to 20 cm/s. This walking speed is by no means considered "high" if rats move without space constraints16. Nevertheless, this speed is too fast for untrained rats to stably walk on the treadmill and would likely result in an abnormal gait and nonuniform movements. These events may seriously affect data reliability and authenticity. However, treadmill speeds …
The authors have nothing to disclose.
This study was supported by JSPS KAKENHI Grant Number JP19K19793, JP18H03129, and JP18K19739.
9-0 nylon suture | Bear Medic Corporation. | T06A09N20-25 | |
Anesthetic Apparatus for Small Animals | SHINANO MFG CO.,LTD. | SN-487-0T | |
ISOFLURANE Inhalation Solution | Pfizer Japan Inc. | (01)14987114133400 | |
Kine Analyzer | KISSEI COMTEC CO.,LTD. | N.A. | A analysis software |
Liquid adhesive | KANBO PRAS CORPORATION | PT-B180 | |
Micro forceps | BRC CO. | 16171080 | |
Motion Recorder | KISSEI COMTEC CO.,LTD. | N.A. | A recording software |
Standard surgical hemostat | Fine Science Tools, Inc. | 12501-13 | |
Surgical blade No.10 | FEATHER Safety Razor CO., LTD | 100D | |
Surgical hemostat | World Precision Instruments | 503740 | |
Three-dimensional motion capture apparatus (KinemaTracer for Animal) | KISSEI COMTEC CO.,LTD. | N.A. | A 3D motion analysis system that consists of cameras |
Three-dimensional(3D) Calculator | KISSEI COMTEC CO.,LTD. | N.A. | A marker tracing software |
Treadmill | MUROMACHI KIKAI CO.,LTD | MK-685 | a treadmill with affialiated the electrical schocker, transparent sheats and a speed control apparatus |