An improved distraction bone screw and a method for its use are described.
The distraction screw is comprised of an implantable distal segment and a
detachably secured proximal segment. The distal segment includes a head
portion and a threaded shank portion. The proximal segment is represented
as an elongated body having an internal bore that extends through its
length. A deployable member is disposed within the bore, which is
extendible outside the internal bore to securely couple to the distal
segment. As an assembly, the distraction screw is used to affix and
realign bone during surgical reconstruction. Upon completion of the
surgical work, the proximal segment is removed and the distal segment is
left attached to the reconstructed bone. Securely affixed, the distal
segment provides an additional point of fixation for the skeletal plates
that are used to preserve the bony alignment while bone healing occurs.
The affixed distal segment will also provide a ready mechanism for
distraction screw replacement at the time of surgical revision without
obligatory plate removal. Different embodiments of the proximal segment,
distal segment and the rotational locking mechanisms which inhibit the
rotation of one segment relative to the other during deployment were also
described. In addition, in cases where the distraction screw must be
placed into the bone at an inclined angle, poly-axial heads were provided
so that proper skeletal plate placement can still be accomplished.