A bioabsorbable surgical fastener comprising a fastener member and an interlocking retainer member. The retainer member has longitudinally extending slots on the lateral sides of the retainer for allowing transverse expansion of the columnar members into which the prongs of the fastener member are locked. Fins on both the lateral and transverse sides of the prongs provide extra strength, and stability during implantation. Stopping surfaces prevent the fastener's barbed tip from exiting the opposite side of the retainer.