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SELF-REINFORCED BIOABSORBABLE DEVICES IN CRANIOFACIAL
SURGERY AND RELATED ISSUES |
Developments in in the field of biomaterials
has lead to manufacturing of absorbable devices with ultra-high
strength that can be used successfully to achieve secure
bone fixation. This was achieved by using the self-reinforcing
technique. Besides plates and screws that are used conventionally
in bone fixation, mesh-plates and membranes were also
developed and studied in experimental models to guide
bone regeneration in bone defects which are either grafted
or nongrafted with successful results or to guide cartilage
formation.
Experimental work on bioabsorbable miniplates and screws
in craniofacial surgery have assessed the healing of a
craniotomies fixed either with polylactide or titanium
miniplates. There was a faster and superior consolidation
with SR-PLLA plates. SR-PGA are rapidly degrading and
hence, they may be used to avoid restriction of growth
in infant neurocranium. Degradation of PGA was accompanied
by a non-specific foreign-body reaction (FBR) and initial
transient osteolysis with decreased osteoid formation
around the screw channel, but compensatory intense osteoid
formation followed after resorption of the polymer. For
PLLA, FBR was considerably milder. Slow resorption of
bone tissue around the screw heads was noted during degradation
and resorption of the polymer, but a reparative phase
with new bone formation followed and the bone surface
was restored. Mechanical testing for compression strength
of rectangular osteotomies, resorbable plate systems tolerated
approximately 46-76 N, SR-PDLLA wire 143 N, metallic wire
239 and metallic microplating 305 N. The results were
slightly in favor of large plates and melting of the screw
heads against the plate.
Preliminary clinical experience results with self reinforced
poly-L-lactide (SR-PLLA) miniplates and screws in craniofacial
surgery show that these devices provide stable bone fixation
with no need for additional support.
Manufacture of new implants, e.g., membranes, plates,
microscrews, tacks and tissue scaffolds to be used for
bone stabilization and guided tissue regeneration, arises
a wide spectrum of experimental work to be done. In near
future, special applications such as intracranial positioning
of the devices will be studied, and strength retention
of different stabilization methods will be tested.
Future will see further developments and innovations on
use of biodegradable devices and craniofacial surgery
for better tomorrow.
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N Ashammakhi, H Peltoniemi and T Waris 7.4.1999
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