Safety and efficacy of the polymer enhanced AS-ELARIS® pedicle screw system using ultrasonically liquefied polylactide: a short-, mid-, and long-term posterolateral fusion study in sheep.

BACKGROUND

Lumbar fusion surgery using pedicle screws and intervertebral cages is frequently performed to treat low back pain when conservative therapies were unsuccessful. Screw loosening, however, remains one of the most common postoperative complications. The purpose of this study was to show that the fixation with polymer-enhanced AS-ELARIS® Pedicle Screws by ultrasonic-assisted extrusion of 0.104 mL resorbable polylactide per screw, represents a suitable alternative to current fixation techniques.

METHODS

Forty adult female sheep were enrolled in the study and posterolateral fusions were performed at two non-adjacent lumbar levels (L1+L2, L4+L5), implanting eight AS-ELARIS® Pedicle Screws per animal. After a survival period of 2 days, 8 weeks, 6, 12 or 24 months, animals were sacrificed and the instrumented vertebrae harvested for macroscopic, radiological, and histological evaluation.

RESULTS

Despite surgical challenges in achieving optimal screw positioning, all evaluations demonstrated good biocompatibility and progressive osseointegration. Ultrasonic liquefaction-mediated polymer enhancement proved safe at all investigated timepoints, without evidence of thermal or inflammatory tissue damage.

CONCLUSIONS

The AS-ELARIS® Pedicle Screw System may offer a promising alternative to current fixation techniques. Its biocompatibility, biodegradability, safe removal, and ease of handling make it a valuable addition to spinal fixation strategies.