Surgical Technique for the Implantation of a Biomimetic Artificial Intervertebral Disc in a Goat Animal Model

This study presents a novel surgical technique for implanting a biomimetic artificial intervertebral disc called the BioAID. The BioAID incorporates a viscoelastic core, a tensile fiber jacket, 3D printed titanium endplates, and unique instruments for disc replacement. To begin, position the anesthetized animal on the surgical table and make a ventral midline skin incision.

Dissect through the subcutis and the platysma muscle. Separate and retract the muscle bellies of the sternohyoideus and sternomastoideus in the midline. Then perform blunt dissection to the right side of the trachea and gently retract the trachea with the esophagus to the left side.

Now, laterally retract the right carotid sheath to the right side. Identify the sixth cervical vertebrae by palpating its left and right large transverse processes extending lateral-ventrally. Palpate the singular ventral process of the fifth cervical vertebra in the midline.

Next, identify the singular ventral process of the fourth cervical vertebrae. Bluntly separate the longus colli muscles to expose the ventral surfaces of the fourth and fifth cervical vertebral bodies. Use two self-retaining Gelpi retractors to retract the longus colli muscle bellies and localize the C4, C5 disc space immediately caudal to the ventral spinous process of the fourth cervical vertebra.

Then perform a limited partial discectomy with a beaver knife. Next, place marks on the midline halfway between the vertebral bodies C4 and C5 for the application of the Caspar distractor. Using a two millimeter drill bit attached to a low speed drill, make a pilot hole on the marks, progressing through cis cortex and into the cancellous bone.

Insert two 2.5 millimeter K-wires into the pilot holes using a low speed drill. Now, use fluoroscopy to confirm the correct placement of the K-wires, alignment with the C4, C5 disc space, and absence of involvement of the trans cortex. Then connect the Caspar vertebral distractor to the K-wires on the C4 and C5 vertebral bodies.

Use a Spinal Curette and Chevalier Jackson grasping forceps to completely empty the dorsoventral central midline portion of the intervertebral disc. Carefully debride the cartilaginous endplates using a Scoville Disc Curette. Next, insert the trial disc without keels to assess the proper artificial disc placement and confirm placement using fluoroscopy.

Then remove the trial disc without keels. Connect the saw guide to the holder and insert it into the prepared space. After confirming the correct insertion of the saw guide, disconnect and remove the holder.

Line up a 0.6 millimeter thick saw blade with the ventral midline vertebral crest of C4 and C5 within the open slot of the saw guide and start sawing using an oscillating sawing machine. Stop sawing when the blade contacts the closed dorsal titanium side of the slot. With the saw blade inserted, perform fluoroscopy.

Next, reconnect the holder to the saw guide and carefully remove the saw guide while maintaining distraction with the Caspar retractor. Insert the trial disc with keels into the disc space and ensure proper placement. Use fluoroscopy to confirm the alignment.

Remove the trial disc with keels and unpack the artificial disc device. Now, press the ventral side of the artificial disc fiber jacket firmly into the disc insert holder and push the artificial disc into the prepared disc space. Use fluoroscopy to confirm correct artificial disc placement and seating of the dorsal and ventral keels on both cranial and caudal sides.

Then release the distraction on the Caspar distractor. Next, remove the Caspar distractor and the 2.5 millimeter K-wires. With a high speed one to two millimeter burr, create a round hole with a diameter of five millimeters within the ventral saw slit caudally on C4 and cranially on C5.Finally, prepare the bone cement according to the manufacturer's instructions.

Apply the bone cement into the channel holes and allow it to cure for approximately 10 minutes. Use two plates of two millimeter titanium with three holes to cover the cemented channels and fixate each plate with two two millimeter locking screws. In vivo implantation of the artificial disc at the C4, C5 level in goats showed accurate placement and immediate stability as confirmed by intra and postoperative imaging.

Computed tomography imaging enabled multiplanar views that confirmed proper alignment of the artificial disc with the intervertebral disc space and vertebral endplates, restoration of disc height, and symmetrical keel channel preparation. Follow up fluoroscopy at 24 hours and 21 days post-implantation confirmed the artificial discs maintained position and the integrity of the surrounding vertebrae. Our disc replacement research provides a safe implantation protocol for a biomimetic artificial disc demonstrating secure fixation and rapid recovery.

The future research of this novel artificial disc will focus on osseointegration, implant stability, tissue response, and long-term biomechanical performance.