Normal anatomy-pars interarticularis. The neck of the Scottie Dog (white arrows) is intact. This is the bony bridge between the superior and inferior articulating facets of the left pars of L3. Spondylolysis. There is a break in the right pars of L4 in this patient. The Scottie Dog has an apparent collar, which it should not have. The collar is the break in the pars.