EXPRESS: Pull-out strength of cannulated compression headless screws and cortical screws in the feline sacrum.

OBJECTIVES: The aim of this study was to compare the pull-out strength of cannulated compression headless screws (CCHSs) of two different lengths with that of cortical screws in the feline sacrum. METHODS: In this experimental study, 30 cadavers of adult Domestic Shorthair cats were randomly assigned to three groups: single 2.4 mm cortical screws engaging 60 % of the sacral width (CS 60, n = 10), 2.5 mm CCHSs engaging 60 % of the sacral width (CCHSs 60, n = 10), and 2.5 mm CCHSs engaging 40 % of the sacral width (CCHS 40, n = 10). Screws were inserted into feline sacra and tested for pull-out strength using a universal testing machine at a constant displacement rate of 0.2 mm / sec up to 20 mm. Peak pull-out force (PPF), displacement at PPF and stiffness were calculated from the load-displacement curves and compared among groups using Fisher's ANOVA and the Welch test. Post-hoc pairwise comparisons were performed using Student's t-tests and the Games-Howell test. Statistical significance was set at p ≤ 0.05. RESULTS: Pairwise comparison of PPF showed significant differences between the CS 60 and CCHS 60 groups (p = 0.05) and between the CS 60 and CCHS 40 groups (p = 0.05). No significant difference was detected between the CCHS 60 and CCHS 40 groups (p = 0.98). For displacement at PPF and stiffness, no significant differences were identified in the pairwise comparison. CONCLUSION AND RELEVANCE: Fully threaded cortical screws provide greater holding strength than partially threaded CCHSs in cadaveric feline sacra. In addition, a single short CCHS offers holding strength comparable to that of a CCHS of the conventionally recommended length.