abnormal sperm flagellum morphology hairpin sperm flagellum hairpin-curved sperm MP:0009243 MPheno.ontology hairpin bent sperm tail a structural alteration where the sperm flagellum becomes bent back (folded) on itself to form a hairpin (loop) structure; a sharp hairpin-like bend formation can disrupt the axial structures and cause the sperm tail to become kinked abnormal hairpin-fold of the sperm flagellum hairpin-shaped sperm flagellar hairpin bends hairpin-configuration spermatozoa hairpin-like sperm flagellum