IMPROVEMENTS IN THE MODIFIED OSTEO-ODONTO KERATOPROSTHESIS (MOOKP) SURGERY TECHNIQUE

Abstract

 

Purpose

 

To assess the long-term effectiveness of 3 bonding agents that are periodically subjected to high static pressures on the optical cylinder face mimicking traumatic ocular incidents, and to develop an autoclavable µ-milling device designed to contour and drill the MOOKP lamina in an efficient and precise manner.

 

Methods

 

An instrument was fabricated to stabilize the lamina and apply direct pressure to the cemented optical cylinder. The strengths of cyanoacrylate adhesive (Histoacryl), a 2-part bone cement (Stryker), and the dental acrylic (Jet) were compared. 4 laminas per agent preserved at 36°C in 30cc of BSS with antibiotic (gatifloxacin 2µg/cc) and antifungal (amphotericin B 0.2mg/cc) for >12 months were subjected monthly to static forces ranging from 200g, 500g, and 1kg (1kg force = 200mmHg IOP equivalent). The force range was expanded to include 2kg and 3kg at month 13. An autoclavable µ-mill was developed to adapt a commercially available Stryker drill; using extracted canines, laminas were fashioned while monitoring internal temperatures via two thermocouples.

 

Results

 

All 12 laminas resisted the applied static forces corresponding to pressures of 2, 5 and 10kg/cm² and the 30kg/cm² applied at month 13. The µ-mill performance was tested on resected cadaveric lamina specimens. Planar surfaces are better than 50µm, perpendicularity is better than 1 degree; drilling departure from ovality is less than 10µm assuring excellent fit with the optical cylinder. The µ-mill was shown to be as efficacious as the manual technique, as it took less than 10 min to create a lamina. Moreover, the canine’s canal temperature never exceeded 38°C whereas with the manual technique, it exceeded 69°C which is higher than bone’s denaturation temperature.

 

Conclusions

 

There was no difference in the effectiveness of the 3 bonding agents at 13 months. A dynamic stress test will be necessary to differentiate between the bonding agents. The µ-mill keeps the temperature below the denaturation temperature and thus is safer than the manual technique. These two new observations can improve the MOOKP surgery technique. Acknowledgments: The authors acknowledge the scientific contributions of Giancarlo Falcinelli and Andres Bernal.

 

 

Instrument fabricated to stabilize the lamina and apply direct pressure to the cemented optical cylinder.

 

 

Autoclavable µ-milling device.

 

Keywords: 575 keratoprostheses • 467 clinical laboratory testing