Insert the point of a utility knife blade into the seam between the caning insert and the chair. Run the blade along and all the way around the seam to separate the spline from the chair. The spline is the runner that is fixed in the groove around the chair seat opening and that secures the caning in place.
Pry out the spline with a scaling chisel.
Cut a piece of caning, using scissors, that is 1 inch longer in both directions than the opening in the chair seat.
Submerge the cut piece of caning in water and leave it to soak for approximately half an hour, or until it is pliable. Remove the caning from the water and shake off the excess.
Center and place the caning over the opening in the seat.
Tap a wood wedge into the groove at the front of the chair, securing the edge of the caning with it. Stretch the caning towards the back of the chair and insert another wedge to hold it in place. Stretch the sides and insert wedges.
Extrude a thin bead of wood glue around the rim of the seat opening, on top of the wicker so it runs along the line of the spline groove.
Tap the spline back into the groove, stretching and wedging the caning at the same time. Work gradually around the chair opening and remove the wood wedges as they are reached.