Animal models of compression spinal cord injury

Abstract

Compression spinal cord injuries are a common cause of morbidity in people who experience a spinal cord injury (SCI). Either as a by-product of a traumatic injury or due to nontraumatic conditions such as cervical myelitis, compression injuries are growing in prevalence clinically and many attempts of animal replication have been described within the literature. These models, however, often focus on the traumatic side of injury or mimic short-term injuries that are not representative of the majority of compression SCI. Of this, nontraumatic spinal cord injuries are severely understudied and have an increased prevalence in elderly populations, adults, and children. Therefore, there is a need to critically evaluate the current animal models of compression SCI and their suitability as a method for clinically relevant data that can help reduce morbidity and mortality of SCI. In this review, we reviewed the established and emerging methods of animal models of compression SCI. These models are the clip, balloon, solid spacer, expanding polymer, remote, weight drop, calibrated forceps, screw, and strap methods. These methods showed that there is a large reliance on the use of laminectomy to induce injury. Furthermore, the age range of many studies does not reflect the elderly and young populations that commonly suffer from compression injuries. It is therefore important to have techniques and methods that are able to minimize secondary effects of the surgeries, and are representative of the clinical cases seen so that treatments and interventions can be developed that are specific.

Keywords: age related; compression; elderly; nontraumatic; pediatric; rodent.

FIGURE 1

Schematic of spinal cord injury compression model using an aneurysm clip on the exposed spinal cord post‐laminectomy. The spinal cord sits between the two prongs of the aneurysm clip and compresses the spinal cord laterally for a short time before been removed. Created with BioRender.com.

FIGURE 2

Schematic of balloon compression model with a 2‐French Fogarty catheter and the inflatable “balloon” tip. The catheter is maneuvered under the spinal column and above the dura upstream from the laminectomy, before being inflated. Created with BioRender.com.

FIGURE 3

Schematic of solid spacer model using a wedged shape spacer which is inserted between the dorsal spinal column and dura of the spinal cord after a laminectomy. The spacer can be left in for days–weeks. Created with BioRender.com.

FIGURE 4

Schematic of expanding polymer with a thin strip of polymer inserted between the posterior spinal column and dura of the spinal cord after a laminectomy. The spacer expands in situ over time to create a growing spinal cord injury that slowly compresses the spinal cord. Created with BioRender.com.

FIGURE 5

Schematic of the weight drop method using a mechanical impactor. The weighted rod drops on the exposed spinal cord from a set height and will displace the cord a varying degree and time depending on the model of weight drop used. Created with BioRender.com.

FIGURE 6

Schematic of calibrated forceps model for compression spinal cord injury. The forceps are modified to have a spacer between the handles so that the compression of the spinal cord is consistent. This procedure can be done from the posterior plane or lateral plane of the spinal cord post‐laminectomy. Created with BioRender.com.

FIGURE 7

Schematic of the screw method of NTSCI where a screw goes through the lamina of the spinal column and compresses the spinal cord. The screw can be adjusted incrementally over a period of days to weeks. Created with BioRender.com.

FIGURE 8

Schematic of the strap method of compressive spinal cord injuries. The thread passed through the dermal layers and wraps under the spinal cord before exiting the derma. The straps are then attached to weights that pull the spinal cord up and compress it against the posterior spinal column. Created with BioRender.com.

FIGURE 9

Schematic of Bluetooth compression model in sheep. The compression device is screwed into the anterior C2–C3 spinal column after removal of the intervertebral disk. The device then increases compression on the spinal cord using a Bluetooth‐controlled plunger that can be incrementally increased. Created with BioRender.com.