Burst fractures were created in the spines of twelve dairy calves and
the mechanism of indirect canal clearance studied. The spines were red
uced posturally and divided in to four subsets-control, and subsets in
which either the posterior longitudinal ligament (PLL), the PLL and a
nnulus, or posterior osteoligmentous structures were sectioned. The sp
ecimens were then instrumented and further reduction obtained through
application of extension and distraction forces. Statistically signifi
cant reduction of the intracanal burst fragment occurred even if the P
LL or PLL and annulus were incompetent but did not occur in that group
in which the posterolateral complex had been sectioned.