A tissue retractor with particular use in spinal surgery comprises a pair of pivotally linked arms, each with a blade mounted thereto by a ball and socket joint to allow the blades free movement relative to the arms. The blades have anchoring end to anchor to bone, which preferably are sharp piercing tips. The balls and the sockets are preferably detachable from each other. The retractor is operable by placing the blades in a wound opening; securing the anchoring ends to a portion of bone at positions a distance apart from each other to define a desired surgical field; and operating the retractor to cause the blades to separate and to retract tissues surrounding said wound opening by outward pivoting of the blades relative to the position of the anchoring ends. A supplemental retractor blade or blades may be provided by a linking armature for additional retraction generally perpendicularly to a retraction action provided by the main retractor blades.