Introduction Orbital floor fractures or “blowout fractures” frequently result form blunt trauma to the face. Definitively, the repair of orbital floor fractures is a common maxillofacial procedure that aims at restoring the bony structure of the orbital floor using various surgical techniques and materials. One of the key considerations in orbital floor reconstruction is the choice of mate-rial. Different materials such as titanium mesh, and bioresorbable polymers have been tradi-tionally used in this context, each with its advantages and disadvantages. Titanium offers good structural support, but needs removal if infection or discomfort occurs. Bioresorbable polymers degrade over time, but are susceptible to mechanical failure. Magnesium biomateri-als may overcome these biomechanical limitations and are the next-generation biodegradable implants for trauma surgery applications, eliminating the need for surgical removal of im-plants. In addition, magnesium materials provide advantages such as reduced implant weight and improved load transfer. Material and Methods Six Tyrolean mountain sheep were included in this animal study between January 2023 and February 2023. After a controlled fracture of the orbital floor via a transconjunctival approach the repair of right and left orbits followed using unmodified and PEO-surface modified ZX00 (Mg-0.45Zn-0.45Ca) implants. The suitability of these implants was evaluated based on their intraoperative biomechanical behavior, and postoperative outcomes. Outcome measures in-cluded surgical complications assessed using regular examinations. The sheep were moni-tored for a period of 12 weeks at the BMF animal facility. Unmodified and PEO-surface mod-ified ZX00 magnesium implants were compared in terms of implant volume, surface area and hydrogen gas formation. Data analysis included descriptive statistics to identify factors acco-ciated with good biomechanical and surgical performance. The sheep were monitored for a period of 12 weeks at the animal husbandry facility. Relevant parameters were assessed, including the gas volume of the magnesium implants. Page 19 of 90 Results At week 1, there was no swelling, tearing, discharge, or tissue damage. Additionally, emphy-sema of the lower lid was detected in one, and (pseud-)enophthalmos was noticed in three or-bits. At weeks 6 and 12, there were no infections, exophthalmus, enophthalmus, emphysema, or bleeding. The initial mean total gas volume of the left and right orbits measured by hCT was 0.9 cc and 0.6 cc respectively on the day of surgery, but no statistically significant differ-ence was observed between the two unmodified and modified Mg implants (p=0.194). All Mg orbital implants were present at week 12. No complications such as plate fractures or migration were observed. The implant volume of uncoated ZX00 implants was lower than the implant volume of PEO surface-modified ZX00 implants (Fig.2), measured by post-mortem micro-CT (p=0.026), but the implants surface area was not different (Fig.2) at 12 weeks. Conclusion This large animal study showed that REE-free ZX00 magnesium biomaterials were suitable and safe for orbital floor repair. Overall, we found a good biological response. Additionally, PEO surface modification enhanced the corrosion resistance and overall performance of mag-nesium implants. Clinical trials are needed to validate these results and to evaluate the long-term outcomes of magnesium implants for orbital floor repair.
Preclinical application of Mg- based bioresorbable material for orbital floor reconstruction in an animal model
Tomic, J. (Autor/-in). 2024
Studienabschlussarbeit: Dissertation