Operation process of creating injury model using free fall impactor for traumatic brain and spinal cord injury

Traumatic brain injury (TBI) refers to brain injury caused by external mechanical force. The clinical incidence of TBI is increasing year by year. It is crucial to establish a good animal model in order to better study the pathogenesis of these issues, understand the pathophysiological processes of traumatic brain injury, and develop new treatment methods.

The falling impact model is used for modeling, and before modeling, surgery is required to expose the intact dura mater. The falling impact acts on the intact dura mater, causing cortical contusion. The severity of the injury is adjusted by changing the weight and height of the falling body.

Create a rat model of severe traumatic brain injury using a self-made and improved free fall method.

Free fall method: It consists of a brain stereotaxic device, a fixed frame, a smooth stainless steel tube with holes, a falling weight, an impact needle, and a stopper. When in use, the stopper is inserted into a stainless steel tube at a certain height, the weight is placed, the impact needle is placed on the dura mater, and the stopper is quickly pulled out. The weight impacts the impact head at the speed of free fall, which directly hits the dura mater, causing a model of cranial injury. The following are some accessories of the free fall hammer

Impact needle (choose the corresponding model of impact needle for mice of different body types)

Weights (choose relative weights for mice of different body types)

Free fall bracket (optional)

Spinal cord strike adapter (fixing mouse spinal cord)

Next is the operation process

Select 250-300g male SD rats and fast for 8-12 hours before modeling; Rats were weighed and anesthetized with 10% chloral hydrate (0.3ml/100g) or with gas anesthesia under sufficient conditions for inhalation anesthesia, reducing the mortality rate of rats while ensuring the success rate of the experiment. Use a hair clipper to remove the hair on the top of the rat's head, prepare the skin, disinfect it with iodine, and then cut open the scalp in the mid sagittal plane, about 3-4cm long.

Peel off the soft tissue, remove the outer membrane of the bone, expose the left parietal bone, and drill a small hole with a high-speed skull drill at a position 3mm behind the coronal suture and 2.5mm left of the midline (this positioning can be adjusted), and enlarge it into a 5mm diameter bone window to expose the arachnoid membrane and maintain the integrity of the dura mater.

Place the impact needle outside the dura mater without placing a weight. Adjust the needle upwards by 2-3mm so that a 40g weight falls freely along the catheter from a height of 20cm and impacts the needle (suddenly pulling out the stopper). This can compress the needle to a depth of 2-3mm without piercing through the dura mater, causing local brain contusion and laceration, resulting in an impact force of 800g/cm (40g × 20cm). After the impact, immediately remove the injured area to avoid secondary damage. Suture the scalp layer by layer, clamp the wound with a hemostatic forceps, wipe it with an alcohol cotton ball, remove the ear canal and rat, inject penicillin anti infection into the muscle, and put the animal back into the feeding cage. Pay attention to postoperative insulation.