A Mouse Model of Lumbar Spine Instability

This is a surgery to induce the mouse model offers an alternative for lumbar intervertebral disc degeneration related studies. This robust LSI mode requires no special equipment. It's reproducible and it can be used to induce the intervertebral disc degeneration in a relatively short period of time.

Controlling the incision depths and the hemorrhage and perform for resection of each interspinous process are two key expense for implantation of our success for experiment. After confirming a lack of response to pedal reflex, place an anesthetized eight week old, male, C57 black six mouse onto a surgical pad in the supine position and apply ointment to the animal's eyes. Use a small animal trimmer to shave the surgical area from the lower thoracic region to the top of the sacral region and remove the shaved fur with tissue wipes.

Apply depilatory cream to the shaved area using gauze to remove the cream after no more than three minutes and flush the exposed skin with two milliliters of 0.9 sterile saline. Then place a custom-made surgical cylindrical pad under the abdomen to raise the lumbar spine. To expose the L3 and L5 vertebrae use the index finger to touch the subcutaneous spinous processes of the lumbar vertebrae and palpate to compare the processes with those of the thoracic vertebrae and sacral vertebrae to identify the lumbar region.

Rinse the skin with 75%alcohol, and using a dissecting microscope use a scalpel to make a three to four centimeter midline skin incision over the lumbar region from the mid thoracic region to the hip. Identify the lumbar spine by the V-shape of the posterior fascia inserted, into the tip so the spinous processes and use the scalpel to make shallow posterior paraspinous muscle incisions along the spinous processes from L3 to L5 laterally on both sides of the spine. Then use two pairs of ophthalmic forceps to separate the muscle layers to expose the L3 to L5 spinous processes and supraspinous ligaments.

To separate individual spinous processes use venous sheers to cut off interspinous ligaments and to resect the L3 to L5 spinous processes and interspinous ligaments. Then use sterile number five silk braided sutures to close the skin incision without reattaching the paravertebral muscles and apply chlortetracycline hydrochloride ointment to the surgical site. 3D histomorphometric analysis allows intervertebral disc measurement, while 3D structural analysis allows quantification of the total tissue volume.

The intervertebral disc volume significantly increases one week after surgery before decreasing two to 16 weeks after the procedure consistent with a decrease in the intervertebral disc height measured over the same time period. Increased cavities within the cranial endplates are also observed in LSI mice as quantified by an increased percentage of trabecular separation values greater or equal to 0.089 and a significant increase in the endplate volumes post-surgery. Model endplates exhibit a similar phenotype, indicating that LSI leads to endplate hypertrophy and an increase in cavity number.

L5 vertebra volumes slightly increase post-surgery with statistical differences observed at 16 weeks. A significant decrease in the bone to total tissue volume ratio is also present 16 weeks after surgery, indicating that LSI causes vertebral bone loss at a later stage. A reduction in intracellular vacuoles of nucleus pulposus cells is also accelerated in LSI animals with increased numbers of osteoclasts observed in LSI endplates.

This model can be modified by attaching different number of vertebrae, such as the fifth lumbar only, or from first lumbar to fifth lumbar.