A pelvic implant orthosis in rodents, for spinal cord injury rehabilitation, and for brain machine interface research: Construction, surgical implantation and validation

Highlights

• Construction and surgical implantation of a pelvic orthosis for rats is described.

• Orthosis allows easy attachment to a range of standard robotic and other devices.

• ANOVA shows no implant effects or perturbation on stepping kinematics in population tested.

• Orthosis osseo integrates well with no apparent discomfort or locomotor deficits.

Abstract

Background

Rodents are important model systems used to explore spinal cord injury (SCI) and rehabilitation, and brain machine interfaces (BMI). We present a new method to provide mechanical interaction for BMI and rehabilitation in rat models of SCI.

New method

We present the design and implantation procedures for a pelvic orthosis that allows direct force application to the skeleton in brain machine interface and robot rehabilitation applications in rodents. We detail the materials, construction, machining, surgery and validation of the device.

Results

We describe the statistical validation of the implant procedures by comparing stepping parameters of 8 rats prior to and after implantation and surgical recovery. An ANOVA showed no effects of the implantation on stepping. Paired tests in the individual rats also showed no effect in 7/8 rats and minor effects in the last rat, within the group's variance.

Comparison with existing methods

Our method allows interaction with rats at the pelvis without any perturbation of normal stepping in the intact rat. The method bypasses slings, and cuffs, avoiding cuff or slings squeezing the abdomen, or other altered sensory feedback. Our implant osseointegrates, and thus allows an efficient high bandwidth mechanical coupling to a robot. The implants support quadrupedal training and are readily integrated into either treadmill or overground contexts.

Conclusions

Our novel device and procedures support a range of novel experimental designs and motor tests for rehabilitative and augmentation devices in intact and SCI model rats, with the advantage of allowing direct force application at the pelvic bones.

Introduction

As part of a system to allow novel robotic-rehabilitation in rats (Udoekwere et al., 2006) and brain machine interface experiments (Song and Giszter, 2011, Song et al., 2009) we have developed a pelvic implantation surgical technique and apparatus that allows direct application of robot generated forces and torques in the pelvic bones. This paper describes the techniques of construction, implantation and validation needed to replicate our methods in other laboratories. The value of our techniques are that they allow sensorimotor impedance training that targets the mid-low trunk muscles in spinalized rats, and perturbation or interaction in intact rats. Further, the techniques we have developed might also be generalized to smaller animals such as mice with similar materials, or larger animals such as cats using titanium parts.

We describe a pelvic orthosis that clamps to the animals pelvic girdle (as shown in Fig. 1) and extends to a conduit outside the animal's body for force application. Typically, in our hands this occurs through the (active or passive) gimbal of a haptic robotic arm which is attached using standard hardware (e.g., Fig. 1E). The robotic arm allows us to generate and apply elastic forces around the pelvis and mid/low trunk region while the animal walks on a treadmill quadrupedally. In principle 6 degree of freedom interaction is feasible. We have currently successfully implanted over 80 rats. The aim of this paper is to describe the pelvic orthosis design, surgical implantation technique and the associated concerns. We also discuss means we have used for validation of the minimal effects of the orthotic and surgical implantation on the intact animal's locomotion by assessing the kinematics of locomotion prior to and after implantation, and present these data.