see also Interspinous spacer.
Interspinous plates (e.g. Aspen® (Lanx), AffixTM (Nuvasive), Spire® (Medtronic)) clamp across two spinous processes to fixate them (unlike X-StopTM which just limits extension). The Aspen® clamps have a space for a graft that may optionally be used to promote fusion between the spinous processes. Interspinous plates may be used to augment other constructs, e.g. lateral interbody fusion, 1) but are not intended for stand-alone use. Biomechanical stability is reported to be similar to bilateral pedicle screws in flexion, and unilateral pedicle screws in lateral bending 2).