Analysis of compression forces between varying sizes of cannulated screws versus rail external fixation for treatment of Jones type fifth metatarsal fracture.

This study compared peak compression load in Newtons and stiffness in Newtons/millimeter for varying interfragmental screw sizes versus mini rail external fixation for the surgical treatment of Jones fifth metatarsal fractures. Four groups were included into this study: (1) Jones fracture with external fixation (Orthofix, Inc., McKinney, TX); (2) Jones fracture with 4.5-mm interfragmental cannulated screw; (3) Jones fracture with 5.5-mm interfragmental cannulated screw; and (4) Jones fracture with 6.5-mm interfragmental cannulated screw. There was no statistically significant difference between the peak compression achieved with the different groups of interfragmental cannulated screws: 4.5-mm interfragmental cannulated screw = 30.56 (+/- 9.40) N; 5.5-mm interfragmental cannulated screw = 30.69 (+/- 10.75) N; and 6.5-mm interfragmental cannulated screw = 32.84 (+/- 9.65) N. When comparing the compression achieved with the different groups of interfragmental cannulated screws to that achieved with the small rail external fixator (69.70 [+/- 14.69] N), a statistically significant difference was noted. There was no statistically significant difference in regard to stiffness (Newtons/millimeter) noted between the intramedullary cannulated screw groups: 4.5 cannulated screw 5.25 (+/- 1.96), 5.5 cannulated screw 5.50 (+/- 2.01), and 6.5 cannulated screw 6.75 (+/- 2.60). A statistically significant difference was noted when the stiffness (Newtons/millimeter) of the rail external fixator (12.69 (+/- 4.52) was compared to the stiffness achieved with the different interfragmental screws. The results indicated that the small rail external fixation device provided increased compression and an increased ability to resist bending when compared to the different intramedullary cannulated screws.