Memory of DL-polylactic acid biodegradable plates.

Biodegradable plates and screws have many advantages over metal plates and screws. Plates were injection-molded and made of DL-polylactic acid. Four-hole plates were bent with the use of a heated tip to angles of 30, 45, and 60 degrees. They were inserted in the subcutaneous space in the back of rabbits. After 2 weeks, the plates straightened, suggesting that the plates had a memory. The results were confirmed by similar in vitro investigations. The in vitro experiment was repeated with tempering of the plates. The plates were heated to a temperature of 200 degrees C for 45 seconds, cooled, and then again heated to 200 degrees C for 40 seconds. This process resulted in loss of memory of the plates. After 4 weeks, there was a change of the bending angle of less than 2.5 degrees.

Pharmacologic manipulation of postoperative labial wound contraction and midfacial growth in rabbits.

Recent experimental work has suggested that increased lip pressure and scar contraction following lip repair with wide soft-tissue undermining may, in part, contribute to midfacial growth inhibition. The present study was designed to test this hypothesis through the application of pharmacologic agents reported to minimize scar contraction. Thirty-six 6-week-old rabbits were divided into six groups: unoperated controls, rabbits with surgically created defects left unrepaired (surgical controls), and four groups of rabbits with surgically created defects with lip repair and wide undermining on the maxillary surface. Animals with lip repair received either no injections or labial subcutaneous injections of distilled water (route-of-injection controls), normal saline, or papaverine hydrochloride for 2 weeks postoperatively. Rabbits with lip repair and saline or papaverine injections showed significantly (p less than 0.05) decreased lip pressure, relatively hypotonic orbicularis oris muscle EMG activity on the cleft lip side, and greater anteroposterior facial growth (assessed radiologically) from 2 to 24 weeks postoperatively compared with rabbits with lip repair and postoperatively compared with rabbits with lip repair and no injections or distilled water injections. Preliminary results suggest that wound contraction following lip repair and soft-tissue undermining may contribute to mid-facial growth inhibition, which may be reduced by pharmacologic manipulations in the rabbit model.

A test of two midfacial growth models using path analysis of normal human fetal material.

Predictions about the temporal sequencing (i.e., primacy) and causal relationships between various midfacial growth components, as suggested by two midfacial growth models (functional matrix and septal traction), were examined in the present study. The relationships between quantitative changes in the nasal septum, nasal airway, nasolabial musculature, and premaxilla of 15 normal human fetal specimens, ranging in age from 12 to 20 weeks postmenstrual age, were assessed using the multivariate technique of path analysis. Path analysis results revealed that the causal sequence of variables proposed by the septal-traction model explained more of the variance in premaxillary size (87 percent goodness-of-fit) than did the sequence of variables proposed by the functional matrix model (65 percent goodness-of-fit). These results suggest that the septal-traction model may be a more parsimonious and primary explanation of early human fetal midfacial growth than the functional matrix model. Path analysis results also reiterate the observed complex developmental relationships within the fetal labioseptopremaxillary region, knowledge of which may be important in the surgical management of infants with complete cleft.

Development of the orbicularis oris muscle in normal and cleft lip and palate human fetuses using three-dimensional computer reconstruction.

As part of an ongoing study of cleft lip and palate fetal morphology, normal and dysmorphic development of the human fetal orbicularis oris muscle was studied in a cross-sectional sample of 29 human fetuses (20 "normal" and 9 cleft lip and palate) ranging in age from 8 to 21 postmenstrual weeks. The specimens were embedded in celloidin and sectioned at 20 microns, and every tenth section was stained with hematoxylin and eosin. A computer reconstruction technique was applied to produce three-dimensional representations of the orbicularis oris muscle. The orbicularis oris muscle in the normal fetal sample with discernible lip fibers (N = 15) increased symmetrically in both fiber density and complexity from 12 to 21 weeks. Metrically, muscle volume and thickness growth curves were consistent with qualitative observations. In contrast, the unilateral cleft lip and palate fetal specimens with discernible lip fibers (N = 3) exhibited a 3.5-week delay in overall muscle development, asymmetrical fiber distribution, and abnormal fiber insertions. However, quantitatively, no significant (p greater than 0.05) differences were noted in orbicularis oris muscle thickness or volume between the normal and cleft lip and palate fetal specimens through 21 weeks. Findings suggest that orbicularis muscle deficiency, noted clinically in cleft lip and palate neonates, may be a result of perinatal functional dysmorphogenesis rather than congenital mesenchymal reduction or deficiency.

Analysis of the size variability of the human normal and cleft palate fetal nasal capsule by means of three-dimensional computer reconstruction of histologic preparations.

As part of an ongoing study of cleft palate fetal morphology, normal and dysmorphic development of the human fetal nasal capsule was studied in a cross-sectional sample of 29 human fetuses (20 "normal" and 9 cleft), ranging in age from 8 to 21 postmenstrual weeks. The specimens were celloidin embedded, sectioned at 20 microns, and every tenth section stained with hematoxylin and eosin. A computer reconstruction technique was applied to produce three-dimensional representations of the nasal capsule, nasal septal cartilage, and nasal airway. Qualitatively, the cleft palate nasal capsule exhibited gross abnormalities including cartilaginous nasal septum deformities, abnormal septal volume and hypertrophy, reduced nasal airway and capsule volumes, and abnormal spatial relationships between the nasal capsule components. These results suggest that the reduced nasal airways, noted clinically in cleft perinates, may be a function of an interaction of nasal capsule deficiency and nasal septum hypertrophy. However, when lengths and volumes were plotted against fetal postmenstrual age, producing fetal "growth" curves, no significant differences (p greater than 0.05) were noted for growth rates (slopes) or nasal capsule size between the normal and cleft palate fetal samples. Curvilinear regression analysis revealed that both normal and cleft palate nasal capsule and septum lengths changed in a sigmoidal fashion, with the steepest increases from 13 to 17 weeks. In contrast, nasal capsule, airway, and septum volumes changed curvilinearly, showing slow relative growth rates from 8 to 17 weeks, which increased sharply from 18 to 21 weeks. Results suggest that from 8 to 21 weeks prenatally, normal and cleft palate specimens exhibited a similar pattern of fetal nasal capsule development that was characterized by an initial anteroposterior elongation followed by circumferential (i.e., volumetric) growth.