An assembly for distraction of spinal vertebrae and which can optionally accommodate retraction blades. The assembly includes a pair of pins each having a first end adapted for vertebral bone engagement and a second end. A pair of sleeves respectively and concentrically engage said pins. A frame includes respective openings which receive the pins and a first end of each said sleeves. The first end of each said sleeve including a portion offset relative to a longitudinal axis of said sleeve such that when the first end of each said pins is anchored in bone, axial rotation of each said sleeves enables said first end of each said pins to move between a first position in which said vertebral bones are not distracted and a second position in which said vertebral bones are distracted.