User blog comment:Xilinoc/Ch. 554 - Desperate Lights/@comment-1332195-20131023181348/@comment-11051098-20131023222210

The tip of Sakanade's Shikai doesn't look as pointed/sharp angled as the shard that appeared to stick out of her chest. Maybe it simply was some release-related thing. Or maybe, if the theory of Yhwach activating their Vollständigs from his throne could be true, the shard appeared from that reason.