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89th Annual Meeting Abstracts

Changes in Frontal Morphology after Open Posterior Vault Expansion for Sagittal Synostosis
David Y. Khechoyan, MD, Carolyn Schook, BS, Rohit K. Khosla, MD, Joseph S. Gruss, MD, Craig B. Birgfeld, Richard A. Hopper, MD.
University of Washington, Seattle, WA, USA.

PURPOSE: The need for fronto-orbital advancement to correct frontal bossing in sagittal synostosis continues to be debated. In our center, we have clinically observed that in most cases frontal bossing decreases after a single-stage, open posterior and middle vault cranial expansion only. This restrospective study was designed to quantify the changes in frontal bone morphology two years following open posterior and mid-vault cranial expansion operation.
Inclusion criteria required the presence of high-definition CT scans at the pre-operative and two years after primary operation time points. Twenty-seven patients with sagittal synostosis who were treated primarily with a modified Pi procedure met the inclusion criteria and comprised the study group. Changes in frontal morphology were also measured in five patients with lambdoid synostosis, who served as a control group. Linear and angular measurements of the frontal bone contour were performed on axial and sagittal cuts of CT images utilizing V-works software (CyberMed Inc, Seoul, Korea). Two-year post-operative measurements were compared to pre-operative values. We standardized the measurements to age-related skull base growth. We defined the frontal bossing angle as the angle measured in the mid-sagittal plane between a ray from the skull base (sella to nasion) and a ray tangential to the anterior-most projection of the frontal bone.
RESULTS: The prominent frontal contour decreased in all parameters in both the study and the control group patients, when measured at two years following primary surgical correction. The frontal bossing angle decreased an average of 41% in patients with sagittal synostosis compared to an 8% decrease in patient with lambdoid synostosis (p < 0.05, paired t-test). In the sagittal synostosis group, the vertical and horizontal dimensions of the frontal region in the sagittal plane decreased by 8% and 19%, respectively. In the axial plane, the frontal bone contour decreased by approximately 11% in the study group and 10% in the control group, with the change in each respective group being statistically significant (p < 0.05).
CONCLUSION: The frontal region of the skull remodels substantially after a single-stage, open posterior and mid-vault cranial expansion in sagittal and lambdoid synostoses. Based on our analysis, frontal bossing appears to self-correct in patient with sagittal synostosis, obviating the need for an additional frontal contouring operation. The reduction in frontal bossing is likely due to a combination of bi-parietal surgical expansion and mid-face growth that occurs in the two years following the primary operation.


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