Computed Tomography–Based Morphometric Analysis of Extended Strip Craniectomy for Sagittal Synostosis:

The Esthetic Perception of Morphological Severity in Scaphocephalic Patients is Correlated With Specific Head Geometrical Features

OBJECTIVE

To investigate the relationship between perception of craniofacial deformity, geometric head features, and 3D head shape analyzed by statistical shape modeling (SSM).

PATIENTS

A total of 18 unoperated patients with scaphocephaly (age  =  5.2  ±  1.1m)-6 were followed-up after spring-assisted cranioplasty (SAC) (age  =  9.6  ±  1.5m)-and 6 controls (age  =  6.7  ±  2.5m).

MAIN OUTCOME MEASURES

3D head shapes were retrieved from 3D scans or computed tomography (CTs). Various geometrical features were measured: anterior and posterior prominence, take-off angle, average anterior and posterior lateral and horizontal curvatures, cranial index (CI) (cranial width over length), and turricephaly index (TI) (cranial height over length). SSM and principal component analysis (PCA) described shape variability. All models were 3D printed; the perception of deformity was blindly scored by 9 surgeons and 1 radiologist in terms of frontal bossing (FB), occipital bulleting (OB), biparietal narrowing (BN), low posterior vertex (LPV), and overall head shape (OHS).

RESULTS

A moderate correlation was found between FB and anterior prominence (r  =  0.56, P < .01) and take-off angle (r  =  - 0.57, P < .01). OB correlated with average posterior lateral curvature (r  =  0.43, P < 0.01) similarly to BPN (r  =  0.55, P < .01) and LPV (r  =  0.43, P < .01). OHS showed strong correlation with CI (r  =   - 0.68, P < .01) and TI (r  =  0.63, P< .01). SSM Mode 1 correlated with OHS (r  =  0.66, p < .01) while Mode 3 correlated with FB (r  =   - 0.58, P < .01).

CONCLUSIONS

Esthetic cranial appearance in craniofacial patients is correlated to specific geometric parameters and could be estimated using automated methods such as SSM.

A New Measure of Posterior Morphology in Sagittal Craniosynostosis: The Occipital Bullet Index

INTRODUCTION

Sagittal craniosynostosis (SC) is associated with scaphocephaly, an elongated narrow head shape. Assessment of regional severity in the scaphocephalic head is limited by the use of serial computed tomographic (CT) imaging or complex computer programing. Three-dimensional measurements of cranial surface morphology provide a radiation-free alternative for assessing cranial shape. This study describes the creation of an occipital bulleting index (OBI), a novel tool using surface morphology to assess the regional severity in patients with SC.

METHODS

Surface imaging from CT scans or 3D photographs of 360 individuals with SC and 221 normocephalic individuals were compared to identify differences in morphology. Cartesian grids were created on each individual's surface mesh using equidistant axial and sagittal planes. Area under the curve (AUC) analyses were performed to identify trends in regional morphology and create measures capturing population differences.

RESULTS

The largest differences were located in the medial regions posteriorly. Using these population trends, a measure was created to maximize AUC. The OBI has an AUC of 0.72 with a sensitivity of 74% and a specificity of 61%. When the frontal bossing index is applied in tandem, the two have a sensitivity of 94.7% and a specificity of 93.1%. Correlation between the two scores in individuals with SC was found to be negligible with an intraclass correlation coefficient of 0.018. Severity was found to be independent of age under 24 months, sex, and imaging modality.

CONCLUSIONS

This index creates a tool for differentiating control head shapes from those with SC and has the potential to allow for objective evaluation of the regional severity, outcomes of different surgical techniques, and tracking shape changes in individuals over time, without the need for radiation.

Comparing Cephalic Index and Midsagittal Vector Analysis in Assessing Morphology in Sagittal Synostosis: A CT-Based Morphometric Analysis

INTRODUCTION

Assessment of cranial dysmorphism in sagittal synostosis is often subjective but objective measures can be applied. These include cephalic index (CI) and midsagittal vector analysis (MSVA).

OBJECTIVE

To assess discriminant validity, construct validity, and responsiveness of CI and MSVA measured from computed tomography (CT) in patients with sagittal synostosis.

METHODS

Patients with nonsyndromic isolated sagittal synostosis with complete preoperative (n = 30) and postoperative (n = 13) CT data were included. Age-matched control group (n = 24) comprised of normocephalic patients who underwent CT for reasons related to trauma.

OUTCOME MEASURES

Retrospective CT evaluation of CI and MSVA was conducted and correlated with a dysmorphism numeric rating scale (D-NRS) that measured surgeon-rated severity of sagittal synostosis. Responsiveness of CI and MSVA was evaluated using dysmorphism global rating of change (D-GRC).

RESULTS

Thirty patients with sagittal synostosis were demographically similar to 24 normocephalic patients. The difference in CI and MSVA was statistically significant between normocephalic and scaphocephalic patients. Cephalic index had a good correlation with D-NRS (r = -0.665, ρ = -0.667), but not with MSVA (r = 0.250, ρ = 0.203). Change in CI (r = 0.738, ρ = 0.657) was well correlated with D-GRC, but not with MSVA (r = -0.409, ρ = -0.301).

CONCLUSION

Cephalic index appears to quantify the severity of sagittal synostosis better than MSVA. Cephalic index also has better responsiveness than MSVA to measure a reduction in severity of disease; however, MSVA is a better descriptive craniometric measurement. Midsagittal vector analysis was able to quantify the shift in morphology in sagittal synostosis following surgical treatment.

Modification of the Melbourne Method for Total Calvarial Vault Remodeling

Background:

Sagittal synostosis is the most common form of single suture synostosis. It often results in characteristic calvarial deformities, including a long, narrow head, frontal bossing, a bullet-shaped occiput, and an anteriorly placed vertex. Several methods for correcting the phenotypic deformities have been described, each with their own advantages and challenges. In this study, we describe a modification of the Melbourne method of total calvarial remodeling for correcting scaphocephaly.

Methods:

We conducted a retrospective review of all consecutive patients who underwent total calvarial remodeling using a modified version of the Melbourne technique from 2011 to 2015. We evaluated clinical photographs, computed tomographic imaging, and cephalic indices both pre- and postoperatively to determine morphologic changes after operation.

Results:

A total of 9 patients underwent the modified Melbourne technique for calvarial vault remodeling during the study period. Intraoperative blood loss was 260 mL (range, 80–400 mL), and mean intraoperative transfusion was 232 mL (range, 0–360 mL). The average length of stay in the hospital was 3.9 days. The mean cephalic indices increased from 0.66 to 0.74 postoperatively (P < 0.01).

Conclusions:

A modified Melbourne method for calvarial vault reconstruction addresses the phenotypic aspects of severe scaphocephaly associated with isolated sagittal synostosis and maintains a homeotopic relationship across the calvaria. It is associated with shorter operative times, lower blood loss, and lower transfusion requirements.

An Appraisal of the Cephalic Index in Sagittal Craniosynostosis, and the Unseen Third Dimension

BACKGROUND

The cephalic index is often used to evaluate sagittal craniosynostosis corrections; however, validation of this measure remains untested.

METHODS

A three-part study was designed to (1) determine the normal distribution of cephalic indices in untreated sagittal craniosynostosis; (2) examine index values in treated children, subsequently determined to require secondary surgery; and (3) explore the correlation between a photography-based assessment of scaphocephaly severity and the cephalic index.

RESULTS

Of 392 preoperatively measured patients (mean cephalic index, 70.7; 95 percent CI, 57.4 to 89.5), 343 (87.5 percent) had Z scores falling within 2 SD of the mean; only 49 (12.5 percent) fell more than 2 SD below the mean, whereas 13 percent exceeded the mean. For 10 patients requiring secondary surgery (mean cephalic index, 74.8; 95 percent CI, 68.1 to 83.4), the mean Z score was -0.5 (range, -2.5 to 1.6). The polled results of 10 observers revealed no significant correlation between subjectively ranked severity scores and cephalic indices.

CONCLUSIONS

Although the average preoperative cephalic index in children with sagittal craniosynostosis was below normal, the majority of measurements fell within a statistically normal distribution. Furthermore, many children requiring secondary corrections were found to have relatively normal indices, suggesting that normal values are not necessarily predictive of satisfactory outcomes. We also found no correlation between this index and a subjective assessment of severity. These findings suggest that the cephalic index is not a reliable outcome measure, perhaps because of the inability for this ratio to capture the amount of correction of the reduced posterior skull height associated with sagittal craniosynostosis.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Diagnostic, IV.

Operative Management of Nonsyndromic Sagittal Synostosis: A Head-to-Head Meta-analysis of Outcomes Comparing 3 Techniques

BACKGROUND

The timing and surgical technique for the treatment of sagittal synostosis remain controversial. Calvarial vault remodeling (CVR), strip craniectomy (SC), and spring-mediated cranioplasty (SMC) are currently in use. We perform a meta-analysis of the literature to compare these 3 techniques.

METHODS

A literature search identified articles involving operative management of nonsyndromic sagittal synostosis. Comparison of 2 operative techniques was required, and methodology was assessed via the American Society of Plastic Surgeons' Levels of Evidence. Three techniques were considered: CVR, SC, and SMC. Meta-analysis was conducted for change in cephalic index (CI), reported as weighted mean difference (WMD). Pooled subgroup comparisons were performed for operative time, length of stay, blood loss, and cost.

RESULTS

Twelve studies providing level 2 or 3 evidence were included. All studies involved CVR (n = 187), 8 involved SC (n = 299), and 7 involved SMC (n = 158). Head-to-head comparison of change in CI demonstrated a greater, yet statistically insignificant change for CVR versus SMC, WMD = 0.94 (-0.23 to 2.11) (P = 0.12, I(2) = 55%). Calvarial vault remodeling showed a statistically greater change in CI versus SC, WMD = 1.47 (0.47-2.48) (P = 0.004, I(2) = 66%). Compared with SMC/SC, CVR had longer operative length (170 vs 97 minutes), higher blood loss (238 vs 47 mL), longer length of stay (5.1 vs 2.9 days), and higher costs ($35,280 vs $13,147), all with P < 0.0001.

CONCLUSIONS

This study, the first meta-analysis comparing 3 primary operations for correcting nonsyndromic sagittal synostosis, demonstrates no difference in CI for CVR versus SMC and a small but statistically greater improvement in CI favoring CVR over SC. Secondary outcomes favored SC/SMC procedures over CVR. However, long-term studies are still needed to adequately assess the risk-benefit ratios.