STUDIES IN CRANIAL SUTURE BIOLOGY - REGIONAL DURA-MATER DETERMINES OVERLYING SUTURE BIOLOGY

The influence of dura mater on adjacent cranial sutures is significant . By better understanding the mechanisms of normal suture fusion and t he role of the dura mater, it may be possible to delineate the events responsible for the premature suture fusion seen in craniosynostosis. In the Sprague-Dawley rat, the posterior frontal suture normally fuses between 12 and 20 days of postnatal life and has proved to be an exce llent model to describe normal suture fusion. The purpose of this stud y was to document the critical role that the dura mater-suture complex may play on cranial suture biology. Forty Sprague-Dawley rats at 8 da ys of age were divided into two groups of 20 animals each. The control group (group A) had surgical disruption of the dura mater-calvarial i nterface. This was accomplished by elevating a strip of cranium inclus ive of the posterior frontal and sagittal sutures and replacement of t he cranial strip back to its anatomic position, all with the dura mate r left intact. The experimental group (group B) had the same calvarial elevation (strip craniectomy), but the sutural anatomy/alignment was rotated 180 degrees. This rotation placed the posterior frontal suture into the sagittal suture's anatomic position and the sagittal suture into the posterior frontal suture's anatomic position. All of these pr ocedures were accomplished by leaving the underlying dura mater intact . Animals were killed at 20, 30, 40, and 50 days (12, 22, 32, and 42 d ays postoperatively), and tissue sections were examined with hematoxyl in and eosin staining. Group A (control) showed normal but delayed sut ure activity. The posterior frontal suture fused, and the sagittal sut ure remained patent. Fusion was delayed, not beginning before 20 days (12 days postoperative) and showing complete fusion between 30 and 40 days. Group B (180-degree calvarial rotation) demonstrated that the su ture in the posterior frontal anatomic position tactual sagittal sutur e) fused between 20 and 40 days, whereas the suture in the sagittal an atomic position tactual posterior-frontal suture) remained patent thro ughout the study. This study demonstrates that the location of the dur a mater-suture complex is important in determining either suture paten cy or closure in this model. Normal closure of the suture overlying th e posterior frontal dura mater demonstrates that the dura mater itself , or forces derived in specific cranial locations, determines the over lying suture biology.