The Journal of Bone and Joint Surgery (American) 85:2152-2155 (2003)
© 2003 The Journal of Bone and Joint Surgery, Inc.
Closed Reduction of Forearm Refractures with Flexible Intramedullary Nails in Situ
Oliver J. Muensterer, MD1 and
Markus P. Regauer, MD1
1 Department of Pediatric Surgery, University of Munich, Dr. von Hauner
Children's Hospital, Lindwurmstrasse 4, 80337 Munich, Germany. E-mail address
for O.J. Muensterer:
oliver.muensterer{at}helios.med.unimuenchen.de
Investigation performed at the Department of Pediatric Surgery,
University of Munich, Dr. von Hauner Children's Hospital, Munich,
Germany
The authors did not receive grants or outside funding in support of their
research or preparation of this manuscript. They did not receive payments or
other benefits or a commitment or agreement to provide such benefits from a
commercial entity. No commercial entity paid or directed, or agreed to pay or
direct, any benefits to any research fund, foundation, educational
institution, or other charitable or nonprofit organization with which the
authors are affiliated or associated.
Background: Refractures of the forearm after flexible intramedullary
nailing are rare. An alternative to nail replacement is closed reduction with
the nails in situ. We successfully performed this maneuver on a
thirteen-year-old boy. However, no data on the stability of previously bent
nails are available. The purpose of the present study was to assess the
mechanical stability of titanium and stainless steel flexible intramedullary
nails after one cycle of reversed bending.
Methods: In an in vitro study, ten titanium and eighteen stainless
steel 3.0-mm flexible intramedullary nails were subjected to an increasing
lateral bending force until the point of first plastic deformation. As an
analogy to the clinical case, they were then bent to an angle of 21° and
were manually reduced back to their original straight position and the
experiment was repeated. The forces needed to achieve first plastic
deformation and modified spring constants (force/deflection) were calculated
and were compared between the native and previously bent nails.
Results: The average force required for permanent deformation of the
previously bent nails was reduced by 37% for both titanium and stainless steel
nails (from 21 to 13.2 N for titanium nails [p < 0.01] and from 25 to 15.7
N for stainless steel nails [p < 0.001]). The average modified spring
constant decreased by 15.1% (from 0.814 to 0.691 N/°) for titanium nails
(p < 0.001) and by 12.2% (from 0.991 to 0.870 N/°) for stainless steel
nails (p < 0.001). Overall, steel nails were stiffer and stronger than
titanium nails were. There was no macroscopic evidence of metal fracture or
fatigue after one cycle of reversed bending to 21°.
Conclusions: Closed reduction of a forearm refracture with flexible
intramedullary nails in situ is a safe, noninvasive, and effective alternative
to nail replacement. However, mechanical stability of the nails is
significantly reduced after the procedure. Therefore, the patient should be
instructed to avoid any excessive forces to the forearm until fracture union
has been documented radiographically, and casting for a limited time may be
appropriate.

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