An expandable bone plate assembly is provided having a top plate portion and a bottom plate portion. A back side of the top plate portion has a longitudinally extending blind slot. A transversely extending counterbore extends through front back sides of the top plate portion. A transversely extending bore extends through the front and back sides of the bottom plate portion. The bone plate assembly also includes a pin with a pin head and a pin shaft depending from the pin head. The pin shaft is disposed within the transversely extending bore of the bottom plate portion and has an outer diameter greater than the minor diameter of the transversely extending bore. The pin head is disposed against the longitudinally extending blind slot of the top plate portion.