Abstract
Background Intramedullary screw fixation is a commonly used technique for the management of
metacarpal fractures. However, compression across the fracture site can lead to unintentional
shortening of the metacarpal.
Questions/Purposes Our aim was to evaluate the risk of overshortening with differing intramedullary
device designs for fixation of metacarpals.
Methods The small finger metacarpal of nine fresh-frozen cadavers were included. A metacarpal
neck fracture was simulated with a 5-mm osteotomy. Three different intramedullary
screw designs were compared. Each screw was placed in a retrograde fashion into the
intramedullary canal and the amount of shortening measured. Screws were reversed and
the number of reverse turns with the screwdriver needed to release overshortening
were measured.
Results The average shortening at the osteotomy site was 2.5 mm. The mean shortening was
80%, 58%, and 12% for the partially threaded screw, fully threaded screw, and threaded
nail, respectively. The mean differences of the distance shortened were statistically
significant for the threaded nail compared with the partially and fully threaded screws.
The partially threaded screw had the most shortening, while the threaded nail provided
the least amount of shortening. When the screws were reversed, the screws did not
disengage until the screw was fully removed from the osteotomy site.
Conclusion The fully threaded nail demonstrates less shortening and possibly minimizes overshortening
of fractures compared with partially threaded and fully threaded screw designs. Overshortening
cannot be corrected by unscrewing the screw unless completely removed from the distal
fragment.
Clinical Relevance Orthopaedic surgeons may select intermedullary screws based on the design that is
suited for the particular metacarpal fracture pattern.
Keywords
metacarpal - fracture - treatment - intramedullary screw
