The concept of a poller screw is based on the principle that the
malalignment induced by oblique, proximal and distal fractures can be
counteracted by the nail-directing effect of the screw. Therefore, its position
should aim to counteract the anticipated displacement of the fracture. Most
often, it is therefore inserted in the short side in the distal fragment. If
there is a wide canal, two screws can be inserted, one on either side of the
path of the nail. It is technically challenging to insert the poller screw in
the exactly correct position. On one hand, the screw should prevent reaming in
the undesired location. On the other hand, it should not impede the reaming
process, or nail insertion.
It is better to insert the poller screw prior to reaming and, in cases of
unreamed nailing, prior to nail insertion, in order to provide adequate contact
between the nail and the screw. If the poller screw is inserted after reaming,
the path of the nail is already set and the poller screw may not function. A
small fracture screw, or a locking screw, can be used as a poller screw,
depending on the local anatomy.
The reaming process in the presence of the poller screw must be performed
very carefully in order not to damage the reamer tip.
The most frequent indication for poller screws is an oblique fracture which
would tend to shift when the axial knee blow technique is used to close any
fracture gap, or when the patient is mobilized.
See also: Stedtfeld HW, Mittlmeier T, Landgraf P et al (2004) The
Logic and Clinical Applications of Blocking Screws. J. Bone Joint Surg.
Am. 86:17-25, 2004.