A tether tensioner includes a handle assembly, an elongate member extending distally from the handle assembly, and an engaging portion. The handle assembly includes a stationary member, a trigger pivotably coupled to the stationary member, and a spool rotatably supported on the stationary member. The spool is configured to wrap a tether thereabout. The spool is operatively coupled with the trigger such that pivoting of the trigger relative to the stationary member causes rotation of the spool. The elongate member includes a channel configured to slidably receive a tether therethrough. The engaging portion is configured to receive a head portion of a bone screw such that a tether extends from the head portion disposed in the engaging portion to the spool through the channel of the elongate member.