Monday, March 28, 2011

Stability of Locking and Non-Locking Plates in an Osteoporotic Calcaneal Fracture Model

Till Illert, MD; Stefan Rammelt, MD, PhD; Tim Drewes, MD; Rene Grass, MD

Background: The aim of this biomechanical cadaver study of calcaneal
fractures was to investigate whether a locking calcaneal plate provides
more stiffness in osteoporotic bone compared to a non-locking plate.
Materials and Methods: Sixteen fresh frozen bone mineral density
(BMD)-matched cadaver feet were tested in a four-part model of a
Sanders Type IIB calcaneal fracture. The fractures were fixed either
with a non-locking AO (Sanders) plate or an interlocking AO plate
(Synthes, Paoli, PA) to the lateral calcaneal wall with six screws.
Specimens were subjected to cyclic loading which was increased stepwise
to full body weight. Displacement of the posterior facet fragment was
measured with an optical tracking system in the sagittal and transverse
planes. Results: No statistically significant differences were observed
between the non-locking and the locking plates with respect to number
of cycles to failure or 1-mm displacement of the posterior facet. The
initial stiffness was significantly higher for non-locking plates.
Conclusion: In osteoporotic bone, the greater stiffness of the
screw-locking plate construct was offset by the smaller diameter of the
screw threads and the lower friction between the plate and bone when a
locking plate was used. In clinical practice, the plate should first be
compressed to osteoporotic bone with cancellous screws and at least two
screws should be placed in the anterior process and in the tuberosity
of the calcaneus.

Key Words: Calcaneus; Fracture; Locking Plate; Non-Locking Plate;
Biomechanical Properties

1 comment:

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