An assembly for tissue retraction in surgery includes a pair of arm members removably positioned on and movable along an elongate support member. The arm members each include an external housing, a locking member positioned within the external housing and a passageway extending through the external housing and the locking member. The elongate support member extends through the passageways and the locking members are releasably biased into engagement with the elongate support member to allow the arm members to move in opposite directions along the elongate support member and prevent the arm members from moving toward one another. Each arm member further includes a rotatable engagement portion engageable with a respective retractor portion and a locking element releasably biased into engagement with the engagement portion to limit rotation of the engagement portion to a first direction relative to the arm member.