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KMID : 0350519920450020517
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Journal of Catholic Medical College
1992 Volume.45 No. 2 p.517 ~ p.531
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The Effect of rigid Internal Fixation on Growth of the Craniofacial Bone in Growing Rabbits
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Abstract
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Craniofcial surgery includes those surgical procedures to correct complex congenital and acquired deformities of cranial and facial bones. Classically, osteosynthesis of the craniofacial skeleton has been performed using interosseous wire.
Miniplate and
screw fixation has had a profound effect on the recent development of craniofacial surgery. Rigid internal fixation has proven of great value in adult orthognathic and traumatic reconstructive surgical procedures. In recent years, craniofacial
surgeons
have extended the application of rigid fixation techniques to correct congenital malformations in infancy and early childhood. This technology has been shown to create an environment conductive to primary bone healing, to obviate the need for
intermaxillary fixation, and to contribute in lowering postoperative morbidity. But the effect of rigid fixation on growith of the craniofacial skeleton is not entirely known and has not been qualified in infancy and childhood.
This study is to determine which of the following theoretical possibilities : (1) craniofacial growth could continue unhindered by the rigid fixation, (2) growth could be limited either locally where the plate is applied or in an adijacent
region,
and
(3) local growth restriction may be associated with a compensatory growth in an adjacent region.
Thirty -one male New Zealand white rabbits weighing 500g to 600g were obtained immediately after weaning at the age of 6 to 7 weeks and divided into 4 surgical groups. All rabbits in group I, II, III, and IV were anesthetized with intramuscular
ketamine
20mg/kg. Their scalp and face were shaved and prepared for surgery using aseptic thechnique. Identical midline sagittal skin incision was made in all operative groups. Periosteal elevation was performed with a periosteal elevator to the left of
the
midline over the nasal and frontal bone. In group I, a rotary saw was used to complete a osteotomy across the left frontonasal suture with saline irrigation. In group II, 4 hole miniplates and self-tapping screws were used across the osteotomy
lines.
The plates and screws were removed after 4 weeks postoperatively under ketamine anesthesia. In group III, rigid internal fixations wer kept until sacrifice. In group IV, interosseous wire techniques were used with 0.018 inch wires across the
osteotomy
lines. Skin and periosteum were closed with a running 4-0 chromic catgut sutures. All animals were housed and fed under identical conditions postoperatively for 12 weeks. After sacrifice. Their skulls were manually cleaned of skin. Furgher soft
tissue
removal was accomplished by boiling in solution of water and potassium hydroxide. The cleaned skulls were soaked in a sodium hyperchlorite solution for an hour and then rinsed and dried.
All dry skulls were taken photographs simultaneously with identical focal length and photographer. The 11 topographic landmarks made on each skull, and each landmarks were recorded using the image analysis system(Vidas, Kontron, West Germany)
interfaced
with a 286 personal computer. All digitizings were made by a single investigator.
The osteometric measurements were evaluated to compare the operated with the unoperated sdes and intergroup significant differences using Student's paired t-test ans Scheffe's test.
@ES The results were as follows:
@EN 1. In group I and group IV, a significant growth restriction on the operated sides(P<0.05, P<0.05) was observed in nasoincisive suture length. However, no such changes were observed in nasal and cranial bone.
2. In group II and group III, more significant growth restriction on the operated side was observed in nasoincisive suture length(P<0.0001, P<0.0001), total length of lateral rim of nasal bone(P<0.001, P<0.0001), and nasal bone extent(P<0.005,
P<0.0001). But no such changes were observed in cranial bone.
3. A significant difference of mean length in nasal bone was observed on the operated side between group I, IV and group II,III(P<0.05), but mean extent between group I and group III only.
The results showed that osteotomy and either plate or removal after union of growing craniofacial skeketon resulted in a statistically significant growth restriction on the operated side, with a statistically insignificant change on the osteotomy
and
wire fixation groups, when compared with unoperated sides.
In conclusion, rigid internal fixation results in growth disturbance on growing craniofacial skeleton. It is recommended that plates and screws are removed as early as possible after bony union.
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