Leinonen S (1), Suokas E (2), Veiranto M (3), Törmälä P (2), Waris T (4), Ashammakhi N (1)

1. Department of Surgery, Oulu University Hospital, P.O. Box 22, FIN-90221 Oulu, Finland.
2. Institute of Biomaterials, Tampere University of Technology, P.O. Box 589, FIN-33101 Tampere, Finland.
3. Department of Surgery, Tampere University Hospital and University of Tampere, Tampere, Finland
4. Department of Surgery, Tampere University Hospital and University of Tampere, Tampere, Finland.

Aim
The aim of the present study was to test the pullout properties of these recently developed bioabsorbable self-reinforced (SR) polylactide miniscrews which contain antibiotics and bioactive glass.

Materials and methods
Ciprofloxacin- plus bioactive glass-containing SR-polylactide miniscrews (BC) were compared with miniscrews made of neat SR-polylactide (A), SR-polylactide with bioactive glass (B) and ciprofloxacin-containing SR-polylactide. BC miniscrews and their controls (A, B, C) (all of length 6.0 mm, core diameter 1.45 mm, thread diameter 2.0 mm) were applied to one pair of cadaveric fibulae. Pullout force was measured using a materials testing machine. We carried out 49-50 pullout tests for each implant type. The Mann-Whitney test and Student's t-test were used for statistical evaluation.

Results
The pullout force for BC miniscrews was 114.9 ± 34.0 (SD) N. Pullout forces for control miniscrews were 162.7 ± 37.8 N (A), 99.1 ± 16.2 N (B) and 142.9 ± 26.9 N (C). Differences between the four groups were statistically significant (p < 0.001).

Conclusion
Ciprofloxacin- plus bioactive glass-containing polylactide miniscrews have good holding power to human cadaver fibulae. However, adding bioactive glass and ciprofloxacin components to neat SR-polylactide results in lower pullout values.

Keywords: Antibiotics; Bioabsorbable; Bioactive glass; Polylactide; Screw