Vitor Filipe

Methods for the experimental functional assessment of rat sciatic nerve regeneration

Abstract In experimental peripheral nerve studies, the rat sciatic nerve model is widely used to examine functional changes after different surgical repairs or pharmacological treatments, following nerve injury. The number and diversity of tests which have been used to assess functional recovery after experimental interventions often makes it difficult to recommend any particular indicator of nerve regeneration. Functional assessment after sciatic nerve lesion has long been focused on walking track analysis, therefore, this article describes in more detail the method to obtain and measure the walking tracks in order to calculate the sciatic functional index (SFI). However, it is important to note that the validity of the SFI has been questioned by several researchers. In addition, the present review includes other traditional tests described in the experimental peripheral nerve literature regarding the rate of return of motor function and sensation, such as the extensor postural thrust (EPT), nociceptive function, and the gastrocnemius-soleus weight parameters. In the last decade, several authors have designed a series of sensitive quantitative methods to assess the recovery of hind limb locomotor function using computerized rat gait analysis. This study aims to review kinematic measures that can be gathered with this technology, including calculation of sciatic functional index, gait-stance duration, ankle kinematics and toe out angle (TOA). A combination of tests, each examining particular components of recovered sensorimotor function is recommended for an overall assessment of rat sciatic nerve regeneration.

Toe out angle : a functional index for the evaluation of sciatic nerve recovery in the rat model

In experimental peripheral nerve studies, the rat sciatic nerve model is widely used to examine functional outcome following nerve injury and repair. A variety of evaluation methods exist in the literature, but an adequate selection continues to be a critical point for the researcher. Rats with sciatic nerve injury typically ambulate with an external rotation of the foot. A new functional assessment instrument, the toe out angle (TOA) is quantified using computerized gait analysis. We compared Sciatic Functional Index (SFI) with TOA parameter after peripheral nerve transection and entubulation repair. We found a good correlation between SFI and TOA measurements in terms of predicting functional recovery. Moreover, the TOA provides information on the biomechanical consequences of the external rotation of the foot in the stance phase of walking.

Motion of the foot and ankle during the stance phase in rats

Computerized analysis of rat gait is becoming an invaluable technique used by some peripheral nerve investigators for the evaluation of function. In this article we describe the use of a biomechanical model of the foot and ankle that allows a quantitative assessment and description of the ankle angle, reflecting plantarflexion and dorsiflexion during the stance phase of gait. Kinematic data of 144 trial walks from 36 normal rats were recorded with a high‐speed digital image camera at 225 images per second. The ankle angular changes associated with the specific temporal events of foot placement on the ground through the stance phase were assessed. The information obtained was used to propose a new subdivision of the stance phase in the rat into three major components. This approach will provide a helpful research tool to analyze gait data that rely on the accurate determination of spatiotemporal foot events.

Effect of skin movement on the analysis of hindlimb kinematics during treadmill locomotion in rats

In rat gait kinematics, the method most frequently used for measuring hindlimb movement involves placing markers on the skin surface overlying the joints being analyzed. Soft tissue movement around the knee joint has been considered the principle source of error when estimating hindlimb joint kinematics in rodents. However, the motion of knee marker was never quantified, nor the different variations in joint angle associated with this gait analysis system. The purpose of this study was two-fold. The first purpose was to expand upon the limited pool of information describing the effect of soft tissue movement over the knee upon the angular positions of the hip, knee and ankle of rats during treadmill locomotion. Secondly, it was a goal of this study to document the magnitude of the skin displacement when using markers that were attached superficially to the knee joint. This was examined by comparing the hindlimb kinematics in sagittal plane during treadmill locomotion determined from the marker attached to the knee and when the knee position was determined indirectly by computer analysis. Results showed that there is a considerable skin movement artefact which propagates to knee joint position and hindlimb kinematics estimates. It was concluded that these large errors can decrease data reliability in the research of rat gait analysis.

Ankle kinematics to evaluate functional recovery in crushed rat sciatic nerve

Peripheral nerve researchers frequently use the rat sciatic nerve crush model in order to test different therapeutic approaches. The purpose of this study was to determine the sequence of changes after an axonotmetic injury by means of a biomechanical model of the foot and ankle, and compare them with walking track analysis, over a fixed period of time. A kinematic analysis program was used to acquire ankle motion data for further analysis. Although repeated measures analysis of variance showed significant cumulative changes induced by the crush lesion for both ankle kinematic parameters and sciatic functional index, post‐hoc multiple comparisons by the Student‐Neuman‐Keuls test revealed significant differences between week 0 and week 8 only for ankle kinematics. These results are of importance in showing the superiority of ankle kinematics in detecting small biomechanical deficits related to hyperexcitability of the plantarflexor muscles, in contrast with walking track analysis, which showed full motor functional recovery 8 weeks after the crush lesion. Muscle Nerve 27: 706–714, 2003

A comparison analysis of hindlimb kinematics during overground and treadmill locomotion in rats

The convenience of the motor-driven treadmill makes it an attractive instrument for investigating rat locomotion. However, no data are available to indicate whether hindlimb treadmill kinematic findings may be compared or generalized to overground locomotion. In this investigation, we compared overground and treadmill locomotion for differences in the two-dimensional angular kinematics and temporal and spatial measurements for the hindlimb. Ten female rats were evaluated at the same speed for natural overground and treadmill walking. The walking velocity, swing duration and stride length were statistically indistinguishable between the two testing conditions. Significant differences were found between overground and treadmill locomotion for step cycle duration and stance phase duration parameters. During the stance phase of walking, the angular movement of the hip, knee and ankle joints were significantly different in the two conditions, with greater flexion occurring on the overground. Despite this, the sagittal joint movements of the hindlimb were similar between the two walking conditions, with only three parameters being significantly different in the swing. Hip height and angle-angle cyclograms were also only found to display subtle differences. This study suggests that reliable kinematic measurements can be obtained from the treadmill gait analysis in rats.

Blind navigation support system based on Microsoft Kinect

This paper presents a system which extends the use of the traditional white cane by the blind for navigation purposes in indoor environments. Depth data of the scene in front of the user is acquired using the Microsoft Kinect sensor which is then mapped into a pattern representation. Using neural networks, the proposed system uses this information to extract relevant features from the scene, enabling the detection of possible obstacles along the way. The results show that the neural network is able to correctly classify the type of pattern presented as input.

Methylprednisolone fails to improve functional and histological outcome following spinal cord injury in rats

Currently, methylprednisolone sodium succinate (MPSS) is the standard treatment following acute spinal cord injury (SCI) as a consequence of the results obtained from the National Acute Spinal Cord Injury Studies. However, many have questioned the efficacy of MPSS because of its marginal effects. Additionally there has been criticism of both study design and statistical interpretation. The functional consequences of experimental SCI have been assessed in many ways. The purpose of this investigation was to determine the effects of MPSS vs. saline solution (SS) following moderate T10 contusion injury in rat. Functional recovery was evaluated using the 21-point Basso, Beattie and Bresnahan (BBB) locomotor recovery scale, the inclined plane, the beam walk, footprint analysis and the horizontal ladder. To optimize the precision and accuracy of functional results we examined the locomotion on a treadmill using three-dimensional (3D) analysis. Stereology was used to estimate the amount of damaged tissue. The results of the traditional functional methods showed that administration of the NASCIS dosage of MPSS following acute spinal cord contusion did not lead to any significant differences in the functional recovery of MPSS- vs. SS-treated animals. More importantly, the results of the 3D kinematic showed that the MPSS administration did not affect the flexion/extension of the hip, knee and ankle joints during the step cycle. Finally, stereological results revealed no statistically significant differences between the two experimental groups. Altogether, our results support data previously reported by several authors, suggesting that MPSS does not lead to improved functional outcome following experimental acute SCI.

Dynamic joint stiffness of the ankle during walking: Gender-related differences

OBJECTIVES To characterize and compare dynamic joint stiffness (DJS) of the ankle in the sagittal plane during natural cadence walking in both genders. DESIGN Observation, cross-sectional and matched pairs. PARTICIPANTS Twenty-one males (mean age=27+/-4.2 years) and 18 females (mean age=22.9+/-4.1 years). SETTING Laboratory at the University de Trás-os-Montes and Alto Douro. The DJS of the ankle was assessed while participants performed barefoot walking at a natural cadence, was measured using a force platform (1000 Hz), and synchronized with a high-speed camera (200 Hz). MAIN OUTCOME MEASURES DJS of the ankle in males and females was calculated in two sub-phases (the second and the fourth sub-phases) of the stance phase. The Wilcoxon non-parametric matched-pairs test and the Mann-Whitney U non-parametric test were used to analyse difference of DJS of the ankle within and between the groups with p0.05 regarded as significant. RESULTS Male and female participants demonstrated significantly (p<0.005) less DJS during the second sub-phase. DJS was not significantly (p>0.063) different between females (0.0511 N m/kg/ degrees ) and males (0.0596 N m/kg/ degrees ) during the second sub-phase. DJS was significantly (p<0.001) higher in males (0.0844 N m/kg/ degrees ) than females (0.0691 N m/kg/ degrees ) during the fourth sub-phase. CONCLUSIONS Gender-specific DJS characteristics demonstrated by females in this study may be used in preventative training programs designed to promote a greater ability to use contractile components to produce mechanical energy through the ankle.

A comparison of two-dimensional and three-dimensional techniques for the determination of hindlimb kinematics during treadmill locomotion in rats following spinal cord injury

Of all the detrimental effects of spinal cord injury (SCI), one of the most devastating effects is the disruption of the ability to walk. Therefore, much effort has been focused on developing several methods to document the recovery of locomotor function after experimental SCI. Computerized rat gait analysis is becoming increasingly popular in the SCI research community. The two-dimensional (2D) kinematic approach is by far the most popular technique in rat gait analysis. This is a simple inexpensive procedure, which requires only one camera to record the movement. Our study included an examination of locomotion on a treadmill using 2D and three-dimensional (3D) analysis, in neurologically intact animals and following moderate T9 contusion injury. Despite the overall time course patterns of the curves were identical, we found significant differences between values of the 2D and 3D joint angular motion. In conclusion, maximal precision and accuracy of the kinematic values are expected when the experimental protocol includes a 3D motion analysis methodology. Moreover, a 2D method cannot be used to determine the external or internal rotations of the foot because this movement occurs in the transverse plane.