Minimally Invasive, Spring-Assisted Correction of Sagittal Suture Synostosis: Technique, Outcome, and Complications in 83 Cases

Mesenchymal stem cells in craniofacial reconstruction: a comprehensive review

Craniofacial reconstruction faces many challenges, including high complexity, strong specificity, severe injury, irregular and complex wounds, and high risk of bleeding. Traditionally, the "gold standard" for treating craniofacial bone defects has been tissue transplantation, which involves the transplantation of bone, cartilage, skin, and other tissues from other parts of the body. However, the shape of craniofacial bone and cartilage structures varies greatly and is distinctly different from ordinary long bones. Craniofacial bones originate from the neural crest, while long bones originate from the mesoderm. These factors contribute to the poor effectiveness of tissue transplantation in repairing craniofacial defects. Autologous mesenchymal stem cell transplantation exhibits excellent pluripotency, low immunogenicity, and minimally invasive properties, and is considered a potential alternative to tissue transplantation for treating craniofacial defects. Researchers have found that both craniofacial-specific mesenchymal stem cells and mesenchymal stem cells from other parts of the body have significant effects on the restoration and reconstruction of craniofacial bones, cartilage, wounds, and adipose tissue. In addition, the continuous development and application of tissue engineering technology provide new ideas for craniofacial repair. With the continuous exploration of mesenchymal stem cells by researchers and the continuous development of tissue engineering technology, the use of autologous mesenchymal stem cell transplantation for craniofacial reconstruction has gradually been accepted and promoted. This article will review the applications of various types of mesenchymal stem cells and related tissue engineering in craniofacial repair and reconstruction.

Understanding the influence of surgical parameters on craniofacial surgery outcomes: a computational study

Sagittal craniosynostosis (SC) is a congenital condition whereby the newborn skull develops abnormally owing to the premature ossification of the sagittal suture. Spring-assisted cranioplasty (SAC) is a minimally invasive surgical technique to treat SC, where metallic distractors are used to reshape the newborn's head. Although safe and effective, SAC outcomes remain uncertain owing to the limited understanding of skull-distractor interaction and the limited information provided by the analysis of single surgical cases. In this work, an SC population-averaged skull model was created and used to simulate spring insertion by means of the finite-element analysis using a previously developed modelling framework. Surgical parameters were varied to assess the effect of osteotomy and spring positioning, as well as distractor combinations, on the final skull dimensions. Simulation trends were compared with retrospective measurements from clinical imaging (X-ray and three-dimensional photogrammetry scans). It was found that the on-table post-implantation head shape change is more sensitive to spring stiffness than to the other surgical parameters. However, the overall end-of-treatment head shape is more sensitive to spring positioning and osteotomy size parameters. The results of this work suggest that SAC surgical planning should be performed in view of long-term results, rather than immediate on-table reshaping outcomes.

Sagittal Craniosynostosis: Treatment and Outcomes According to Age at Intervention

The purpose of this study is to describe the treatment strategies and outcomes of nonsyndromic single-suture sagittal craniosynostosis based on the patient's age at intervention. Studies from MEDLINE, Scopus, and Cochrane Central Register of Controlled Trials were systematically searched for patients with nonsyndromic single-suture sagittal craniosynostosis. Inclusion criteria encompassed studies with follow-up of at least 12 months, minimum of 25 patients per cohort, and first-time surgical intervention. The risk of bias in nonrandomized studies of intervention tool [Risk Of Bias In Non-randomized Studies-of Interventions (ROBINS-I)] was applied. A total of 49 manuscripts with 3316 patients met criteria. Articles were categorized based on age at intervention; 0 to 6, older than 6 to 12, and older than 12 months. Fifteen of the manuscripts described interventions in more than 1 age group. From the 49 articles, 39 (n=2141) included patients 0 to 6 months old, 15 (n=669) discussed patients older than 6 to 12 months old, and 9 (n=506) evaluated patients older than 12 months old. Follow-up ranged from 12 to 144 months. Over 8 types of open surgical techniques were identified and 5 different minimally invasive procedures were described. Minimally invasive procedures were exclusively seen in the youngest patient cohort, while open cranial vault reconstructions were often seen in the 2 older cohorts. Endoscopic surgery and open conservative procedures are indicated for younger patients, while complex open cranial vault reconstructions are common in older patients. However, there is no consensus on one approach over the other. Even with the analysis of this review, we cannot factor a strong conclusion on a specific technique.

Sagittal Craniosynostosis: Comparing Surgical Techniques Using 3D Photogrammetry

BACKGROUND

The aim of this study was to compare three surgical interventions for correction of sagittal synostosis-frontobiparietal remodeling (FBR), extended strip craniotomy (ESC), and spring-assisted correction (SAC)-based on three-dimensional (3D) photogrammetry and operation characteristics.

METHODS

Patients who were born between 1991 and 2019 and diagnosed with nonsyndromic sagittal synostosis who underwent FBR, ESC, or SAC and had at least one postoperative 3D photogrammetry image taken during one of six follow-up appointments until age 6 were considered for this study. Operative characteristics, postoperative complications, reinterventions, and presence of intracranial hypertension were collected. To assess cranial growth, orthogonal cranial slices and 3D photocephalometric measurements were extracted automatically and evaluated from 3D photogrammetry images.

RESULTS

A total of 322 postoperative 3D images from 218 patients were included. After correcting for age and sex, no significant differences were observed in 3D photocephalometric measurements. Mean cranial shapes suggested that postoperative growth and shape gradually normalized with higher occipitofrontal head circumference and intracranial volume values compared with normal values, regardless of type of surgery. Flattening of the vertex seems to persist after surgical correction. The authors' cranial 3D mesh processing tool has been made publicly available as a part of this study.

CONCLUSIONS

The findings suggest that until age 6, there are no significant differences among the FBR, ESC, and SAC in their ability to correct sagittal synostosis with regard to 3D photocephalometric measurements. Therefore, efforts should be made to ensure early diagnosis so that minimally invasive surgery is a viable treatment option.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Early and long-term skull growth after surgical correction for sagittal synostosis in relation to the occurrence of papilledema

OBJECTIVE

Stagnation of skull growth is correlated with papilledema in craniosynostosis. In this retrospective cohort study, we describe the postoperative skull growth after surgical correction for sagittal synostosis and its relation to the development of papilledema.

METHODS

Patients with isolated sagittal synostosis at our center between 2005 and 2012 were included. Occipitofrontal circumference (OFC) was analyzed, at 3 time points (preoperative, 2 years postoperative, and last OFC measurement) and 3 phases (initial postoperative growth, long-term growth, and overall growth), and related to papilledema on fundoscopy.

RESULTS

In total, 163 patients were included. The first time interval showed a decline in skull growth, with subsequent stabilization at long term. Papilledema occurred postoperatively in 10 patients. In these patients, the OFC at 2 years and at last follow-up (T3) were significantly smaller than in patients without papilledema. A larger OFC resulted in a decreased odds of developing papilledema at both postoperative time points (at T2 (OR = 0.40, p = 0.01) and at T3 (OR 0.29, p < 0.001)). Sensitivity and specificity analysis indicated that an OFC below 0.25 SD at T2 (sensitivity 90%, specificity 65%) and below 0.49 at T3 (sensitivity 100%, specificity 60%) are related to the occurrence of papilledema.

CONCLUSION

A small OFC is correlated with the occurrence of papilledema. A decline in OFC within 2 years postoperatively is common in sagittal synostosis and is acceptable up to a value of 0.25SD. Patients with an OFC at last follow-up of less than 0.5SD are at risk for developing papilledema.

Management of Sagittal and Lambdoid Craniosynostosis: Minimally Invasive Approaches

The resurgence of strip craniectomies began in the mid-1990s with advances in surgical technique and anesthesia coupled with the critical observation that earlier interventions benefitted from an easily molded skull. Jimenez and Barone's pioneering introduction of endoscopic approaches to strip craniectomies coupled with postoperative helmeting in newborns and young infants and Claes Lauritzen's introduction of spring-mediated cranioplasty began the era of minimally invasive approaches in the surgical correction of craniosynostosis. This article provides technical descriptions of these treatment modalities, a comparative literature review, and our institutional algorithms for the correction of sagittal craniosynostosis and unilambdoid craniosynostosis.

Response of Gli1+ Suture Stem Cells to Mechanical Force Upon Suture Expansion

Normal development of craniofacial sutures is crucial for cranial and facial growth in all three dimensions. These sutures provide a unique niche for suture stem cells (SuSCs), which are indispensable for homeostasis, damage repair, as well as stress balance. Expansion appliances are now routinely used to treat underdevelopment of the skull and maxilla, stimulating the craniofacial sutures through distraction osteogenesis. However, various treatment challenges exist due to a lack of full understanding of the mechanism through which mechanical forces stimulate suture and bone remodeling. To address this issue, we first identified crucial steps in the cycle of suture and bone remodeling based on the established standard suture expansion model. Observed spatiotemporal morphological changes revealed that the remodeling cycle is approximately 3 to 4 weeks, with collagen restoration proceeding more rapidly. Next, we traced the fate of the Gli1⁺ SuSCs lineage upon application of tensile force in three dimensions. SuSCs were rapidly activated and greatly contributed to bone remodeling within 1 month. Furthermore, we confirmed the presence of Wnt activity within Gli1⁺ SuSCs based on the high co-expression ratio of Gli1⁺ cells and Axin2⁺ cells, which also indicated the homogeneity and heterogeneity of two cell groups. Because Wnt signaling in the sutures is highly upregulated upon tensile force loading, conditional knockout of β-catenin largely restricted the activation of Gli1⁺ SuSCs and suppressed bone remodeling under physiological and expansion conditions. Thus, we concluded that Gli1⁺ SuSCs play essential roles in suture and bone remodeling stimulated by mechanical force and that Wnt signaling is crucial to this process. © 2022 American Society for Bone and Mineral Research (ASBMR).

Long-Term Neurocognitive Outcomes of Spring-Assisted Surgery versus Cranial Vault Remodeling for Sagittal Synostosis

BACKGROUND

A long-term neurocognitive comparison of patients with sagittal synostosis who underwent spring-assisted surgery or cranial vault remodeling has not been performed.

METHODS

Patients with sagittal synostosis who underwent spring-assisted surgery or cranial vault remodeling were recruited from Wake Forest School of Medicine and Yale School of Medicine, respectively. Cognitive tests administered included an abbreviated intelligence quotient, academic achievement, and visuomotor integration. An analysis of covariance model compared cohorts controlling for demographic variables.

RESULTS

Thirty-nine spring-assisted surgery and 36 cranial vault remodeling patients were included in the study. No significant differences between cohorts were found with respect to age at surgery, sex, race, birth weight, family income, or parental education. The cranial vault cohort had significantly older parental age (p < 0.001), and mean age at testing for the spring cohort was significantly higher (p = 0.001). After adjusting for covariates, the cranial vault cohort had significantly higher verbal intelligence quotient (116.5 versus 104.3; p = 0.0024), performance intelligence quotient (109.2 versus 101.5; p = 0.041), and full-scale intelligence quotient (114.3 versus 103.2; p = 0.0032). When included patients were limited to intelligence quotients from 80 to 120, the cranial vault cohort maintained higher verbal (108.0 versus 100.4; p = 0.036), performance (104.5 versus 97.7; p = 0.016), and full-scale (107.6 versus 101.5; p = 0.038) intelligence quotients. The cranial vault cohort had higher visuomotor integration scores than the surgery group (111.1 versus 98.1; p < 0.001). There were no significant differences in academic achievement.

CONCLUSIONS

Sagittal synostosis patients who underwent cranial vault remodeling had higher intelligence quotient and visuomotor integration scores. There were no differences in academic achievement. Both cohorts had intelligence quotient scores at or above the normal range. Further studies are warranted to identify factors that may contribute to cognitive outcome differences.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, II.

Three-Dimensional Treatment Outcomes of a Virtual Helmet Design Protocol for Sagittal Strip Craniectomy

BACKGROUND

The helmet worn after sagittal strip craniectomy must be customized to the surgical procedure and the patient's anatomy to achieve optimal outcomes. This study compares three-dimensional head shape outcomes obtained from a novel virtual helmet design and from a traditional helmet design.

METHODS

Twenty-four patients underwent extended sagittal strip craniectomy performed by a single surgeon and helmet management performed by a single orthotist. Eleven patients constitute the traditional helmet group, with helmet design based on laser scans. Thirteen patients constitute the virtual helmet group, with helmet design based on an overlay of a three-dimensional volume rendering of a low-radiation protocol computed tomographic scan and three-dimensional photograph. Cephalic index and vertical height were recorded from three-dimensional photographs. Three-dimensional whole-head composite images were generated to compare global head shape outcomes to those of age-matched controls.

RESULTS

There was no significant difference in mean cephalic index between the virtual helmet group (83.70 ± 2.33) and controls (83.53 ± 2.40). The differences in mean cephalic index between the traditional helmet group (81.07 ± 3.37) and controls and in mean vertical height were each significant (p < 0.05). Three-dimensional analysis demonstrated normal biparietal and vertical dimensions in the virtual helmet group compared to controls. The traditional helmet group exhibited narrower biparietal dimension and greater vertical dimension compared to controls.

CONCLUSIONS

Traditional and virtual helmet protocols improved mean cephalic index, but the virtual helmet group yielded more consistent and greater change in cephalic index. The virtual helmet design protocol yielded three-dimensional outcomes similar to those of age-matched controls. Traditional helmet design yielded a narrower biparietal dimension and greater vertical dimension to the cranial vault compared to the virtual helmet group and controls.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Morphological and surgical results in sagittal synostosis: early craniectomy versus later cranioplasty

BACKGROUND AND PURPOSE

Morphological correction is one of the main aims of surgery for sagittal synostosis (SSO). Different surgical techniques have been developed; however, few studies have compared the different surgical protocols. The morphological outcome is poorly documented, because a consensual evaluation tool is lacking.

MATERIAL AND METHODS

We performed a prospective study of children operated for SSO in our institution. Children were operated whenever possible at 4 months for craniectomy; by default, children underwent cranioplasty at or after 9 months. The morphological outcome of all children was evaluated using traditional craniometry with head circumference (HC) and the cephalic index (CI), and with the Rotterdam scaphocephaly morphology score (RSMS), a total of semi-quantitative assessments of morphological hallmarks.

RESULTS

Craniectomy was significantly associated with a shorter operation time and hospital stay, and a better impact on HC and CI measurements, compared with cranioplasty. The RSMS was markedly improved after surgery in both groups; however, we found no significant difference in improvement between the two groups. Although the transfusion rate and the prevalence of developmental delay were lower in the craniectomy group, and reoperations for calvarial lacunae or complex craniosynostosis occurred only this group, these differences were not significant.

CONCLUSIONS

Our results support early surgery with craniectomy whenever possible; however, cranioplasty at a later age is a very acceptable by-default indication. In addition to classical craniometry, morphological evaluation using the RSMS or a similar quantitative scale appears highly desirable for future studies.

Disappointing results of spring-assisted cranial vault expansion in patients with Crouzon syndrome presenting with sagittal synostosis

The aim of this study was to report on a single center's experience with spring-assisted cranial vault expansion (SAE) in patients with Crouzon syndrome and sagittal suture synostosis. Strip craniotomy with SAE has resulted in successful outcomes with low complication and revision rates in patients with isolated scaphocephaly. However, recent experience suggests that outcomes in patients with Crouzon syndrome and sagittal synostosis (SS) who undergo SAE are less favorable compared with the outcomes of those who undergo frontobiparietal (FBP) expansion. The authors reviewed both operations performed at a single center and noticed an upward expansion of the skull, which may be related to ventriculomegaly, with concurrent intracranial hypertension and poor aesthetic outcome. All patients diagnosed with Crouzon syndrome and SS who were treated with SAE required a revision FBP operation. Based on this outcome, the authors consider Crouzon syndrome a contraindication for correcting SS with springs.

Machine Learning Applied to Registry Data: Development of a Patient-Specific Prediction Model for Blood Transfusion Requirements During Craniofacial Surgery Using the Pediatric Craniofacial Perioperative Registry Dataset

BACKGROUND

Craniosynostosis is the premature fusion of ≥1 cranial sutures and often requires surgical intervention. Surgery may involve extensive osteotomies, which can lead to substantial blood loss. Currently, there are no consensus recommendations for guiding blood conservation or transfusion in this patient population. The aim of this study is to develop a machine-learning model to predict blood product transfusion requirements for individual pediatric patients undergoing craniofacial surgery.

METHODS

Using data from 2143 patients in the Pediatric Craniofacial Surgery Perioperative Registry, we assessed 6 machine-learning classification and regression models based on random forest, adaptive boosting (AdaBoost), neural network, gradient boosting machine (GBM), support vector machine, and elastic net methods with inputs from 22 demographic and preoperative features. We developed classification models to predict an individual's overall need for transfusion and regression models to predict the number of blood product units to be ordered preoperatively. The study is reported according to the Transparent Reporting of a multivariable prediction model for Individual Prognosis Or Diagnosis (TRIPOD) checklist for prediction model development.

RESULTS

The GBM performed best in both domains, with an area under receiver operating characteristic curve of 0.87 ± 0.03 (95% confidence interval) and F-score of 0.91 ± 0.04 for classification, and a mean squared error of 1.15 ± 0.12, R-squared (R) of 0.73 ± 0.02, and root mean squared error of 1.05 ± 0.06 for regression. GBM feature ranking determined that the following variables held the most information for prediction: platelet count, weight, preoperative hematocrit, surgical volume per institution, age, and preoperative hemoglobin. We then produced a calculator to show the number of units of blood that should be ordered preoperatively for an individual patient.

CONCLUSIONS

Anesthesiologists and surgeons can use this continually evolving predictive model to improve clinical care of patients presenting for craniosynostosis surgery.

Comparison of Perioperative Outcomes and Parental Satisfaction Outcomes of Strip Craniectomy with Postoperative Helmet versus Spring-Mediated Remodeling in Sagittal Craniosynostosis

INTRODUCTION

We sought to compare outcomes and parental satisfaction between 2 approaches for sagittal craniosynostosis: strip craniectomy with spring-mediated skull remodeling (SMSR) and strip craniectomy with postoperative helmet (SCH).

METHODS

Perioperative and outcome data for SMSR or SCH patients between September 2010 and July 2019 were retrospectively reviewed. A telephone survey was administered to parents of children who underwent both procedures.

RESULTS

A total of 62 children were treated for sagittal craniosynostosis by either SMSR (n = 45) or SCH (n = 17). The SCH group had a lower estimated blood loss (27 vs. 47.06 mL, p = 0.021) and age at surgery (13.0 vs. 19.8 weeks) than the SMSR group. Three patients underwent early springs removal due to trauma or dislodgement, all of whom converted to helmeting. Of the 62 children initially identified, 59 were determined to have an adequate follow-up time to assess long-term outcomes. The mean follow-up time was 30.1 months (n = 16) in the SCH group and 32.0 months in the SMSR group (n = 43, p = 0.39). Two patients in the SCH group and one in the SMSR group converted to open cranial vault reconstruction. Thirty parents agreed to respond to the satisfaction survey (8 SCH, 22 SMSR) based on a Likert scale of responses (0 being most dissatisfied possible, 4 most satisfied possible). Average satisfaction was 3.86/4.0 in the SCH group and 3.45/4.0 in the SMSR group. No parents in the SCH group would change to SMSR, while 3 of the 22 SMSR survey responders would have changed to SCH.

CONCLUSIONS

Perioperative outcomes and average parental satisfaction were similar in both groups. Importance of helmet wear compliance and risk of spring dislodgement should be discussed with parents.

Secondary vault reconstruction after open or minimal invasive correction for unisutural, multisutural or syndromic craniosynostosis: A cohort study on the impact of diagnosis and type of initial surgical technique

BACKGROUND

The aim of this study is to identify if certain types of craniosynostosis and/or surgical procedures are more likely to require a secondary intracranial procedure because of insufficient correction of skull shape or raised ICP after initial surgery.

METHODS

All consecutive cases with craniosynostosis that were operated at our center between January 2010 and January 2019 were included and the number of secondary operations of the vault were determined, as well as diagnosis, the indication and type and timing of initial surgery. Monobloc and facial bipartition procedures were excluded.

RESULTS

Over a nine year period, 790 vault corrections were performed in 780 patients of which 38 procedures were reoperations in 35 patient because of raised intracranial pressure or an insufficient esthetic result of the skull shape. Particularly patients with a multisutural or syndromic craniosynostosis are represented in this group, as well as three surgical procedures: 1. biparietal outfracturing for sagittal synostosis; 2. endoscopic stripcraniectomy with helmet therapy for unicoronal, multisutural or syndromic craniosynostosis; 3. conventional occipital expansion for syndromic craniosynostosis.

CONCLUSIONS

The risk of a second intracranial correction for insufficient outcome of skull shape or for raised ICP is related to type of synostosis and type of initial surgical technique. Particularly multisutural and syndromic craniosynostosis are more likely to require repeat surgery for these indications. Concerning initial technique, biparietal outfracturing does not correct sagittal synostosis sufficiently, stripcraniectomy with helmet therapy appears to undercorrect unicoronal, multisutural and syndromic synostosis, and conventional occipital expansion for multisutural and syndromic synostosis has poorer outcome than occipital expansion with distraction.

Computational modelling of patient specific spring assisted lambdoid craniosynostosis correction

Lambdoid craniosynostosis (LC) is a rare non-syndromic craniosynostosis characterised by fusion of the lambdoid sutures at the back of the head. Surgical correction including the spring assisted cranioplasty is the only option to correct the asymmetry at the skull in LC. However, the aesthetic outcome from spring assisted cranioplasty may remain suboptimal. The aim of this study is to develop a parametric finite element (FE) model of the LC skulls that could be used in the future to optimise spring surgery. The skull geometries from three different LC patients who underwent spring correction were reconstructed from the pre-operative computed tomography (CT) in Simpleware ScanIP. Initially, the skull growth between the pre-operative CT imaging and surgical intervention was simulated using MSC Marc. The osteotomies and spring implantation were performed to simulate the skull expansion due to the spring forces and skull growth between surgery and post-operative CT imaging in MSC Marc. Surface deviation between the FE models and post-operative skull models reconstructed from CT images changed between ± 5 mm over the skull geometries. Replicating spring assisted cranioplasty in LC patients allow to tune the parameters for surgical planning, which may help to improve outcomes in LC surgeries in the future.

Comparison of 2 Sagittal Craniosynostosis Repair Techniques: Spring-Assisted Surgery Versus Endoscope-Assisted Craniectomy With Helmet Molding Therapy

INTRODUCTION

This study compares anthropometric outcomes of 2 sagittal synostosis repair techniques: spring-assisted surgery and endoscope-assisted craniectomy with molding helmet therapy.

METHODS

Patients undergoing spring-assisted surgery (n = 27) or endoscope-assisted craniectomy with helmet therapy (n = 40) at separate institutions were retrospectively reviewed. Pre- and 1-year postoperative computed tomography (CT) or laser scans were analyzed for traditional cranial index (CI), adjusted cranial index (aCI), and cranial vault volume (CVV). Nine patient-matched scans were analyzed for measurement consistency.

RESULTS

The spring-assisted group was older at both time points (P < .050) and spring-assisted group CVV was larger preoperatively and postoperatively (P < .01). However, the change in CVV did not differ between the groups (P = .210). There was no difference in preoperative CI (helmet vs spring: 70.1 vs 71.2, P = .368) between the groups. Postoperatively, helmet group CI (77.0 vs 74.3, P = .008) was greater. The helmet group also demonstrated a greater increase in CI (6.9 vs 3.1, P < .001). The proportion of patients achieving CI of 75 or greater was not significantly different between the groups (helmet vs spring: CI, 65% vs 52%, P = .370). There was no detectable bias in CI between matched CT and laser scans. Differences were identified between scan types in aCI and CVV measurements; subsequent analyses used corrected CVV and aCI measures for laser scan measures.

CONCLUSIONS

Both techniques had equivalent proportions of patients achieving normal CI, comparable effects on cranial volume, and similar operative characteristics. The study suggests that there may be greater improvement in CI in the helmet group. However, further research should be performed.

The Science Behind the Springs: Using Biomechanics and Finite Element Modeling to Predict Outcomes in Spring-Assisted Sagittal Synostosis Surgery

Spring-assisted surgery for the correction of scaphocephaly has gained popularity over the past 2 decades. Our unit utilizes standardized torsional springs with a central helix for spring-assisted surgery. This design allows a high degree of accuracy and reproducibility of the force vectors and force distance curves. In this manuscript, we expand on the biomechanical testing and properties of these springs. Standardization of design has enabled us to study the springs on bench and in vivo and a comprehensive repository of calvarial remodeling and spring dynamics has been acquired and analyzed.Finite element modeling is a technique utilized to predict the outcomes of spring-assisted surgery. We have found this to be a useful tool, in planning our surgical strategy and improving outcomes. This technique has also contributed significantly to the process of informed consent preoperatively. In this article, we expand on our spring design and dynamics as well as the finite element modeling used to predict and improve outcomes.In our unit, this practice has led to a significant improvement in patient outcomes and parental satisfaction and we hope to make our techniques available to a wider audience.

Spring-Assisted Surgery for Treatment of Sagittal Craniosynostosis

ABSTRACT

Craniosynostosis (CSS), the premature fusion of calvarial sutures, most commonly involves the sagittal suture. Cranial vault remodeling (CVR) is a traditional method of CSS correction. Minimally invasive methods are becoming widely accepted, including spring-assisted surgery (SAS). The equipment required for SAS is minimal therefore adaptable to resource challenged health systems. This paper outlines the experience of SAS in Moldova.A retrospective study was performed for patients treated with SAS for sagittal CSS from 2011 to 2018 in Moldova. Perioperative data were recorded including age, length of surgery, blood loss, volume transfused and length of stay. Four patients had pre- and post-operative computed tomography (CT) scans which were used to calculate changes in cephalic index, normative cephalic index, and intracranial volume.Thirteen patients underwent SAS. Diagnoses were made clinically and confirmed with CT. Mean age at surgery was 4.0 months, and length of surgery 62.7 minutes. All but one patient received a blood transfusion, as is standard of practice in Moldova. The mean length of post-operative recovery in ICU was 30.9 hours. No complications required surgical revision. Springs were removed after 4 to 5 months. All patients had a subjective improvement in scaphocephaly. Based on the available CT scans, an increase in cephalic index (7.3%), normative cephalic index (11.8%), and intracranial volume (38.1%) was observed. One patient underwent SAS at 11 months and required cranioplasty for asymmetry at the time of spring removal.SAS is a safe and cost-effective method of CSS correction that can be utilized in countries with limited health system resources.

Partial hybrid cranial vault remodeling in late correction of scaphocephaly and revision surgery. A monocentric retrospective study of nine consecutive cases

There is currently no consensus on the surgical attitude to be adopted for late management of sagittal synostosis or for revision scaphocephaly surgeries without prolapse of the cerebellar tonsils. We present here a monocentric retrospective study of nine patients operated consecutively by a fixed expansion method of the cranial vault which may be associated with a fronto-orbital remodeling. The procedure consists in the realization of multiple parietal tongue-in-groove osteotomies fixed by resorbable plates. Simultaneous fronto-orbital remodeling have been performed when needed. No intraoperative complication was noted. The average operating time was 141min. Six patients (66.7%) had a blood transfusion during the perioperative period. The average hospital stay was 4.8days. With a mean follow-up of 26,7months, no surgical revision was noted. In all patients with clinical or ophthalmologic signs of intracranial hypertension, we highlighted a disappearance of signs within 4months. No protective helmet has been used. The craniofacial remodeling was judged very good by the family and the surgical team. Multiple tongue-in-groove tenons remolding cranioplasty associated or not with a fronto-orbital advancement is a safe technique. It seems to us to be a good alternative to floating or fixed bi-parietal or bi-parieto-frontal cranial flaps because of the very large increase in endocranial volume and the possibility of physiologically and aesthetically remodeling the parietal and fronto-orbital regions.

A population-specific material model for sagittal craniosynostosis to predict surgical shape outcomes

Sagittal craniosynostosis consists of premature fusion (ossification) of the sagittal suture during infancy, resulting in head deformity and brain growth restriction. Spring-assisted cranioplasty (SAC) entails skull incisions to free the fused suture and insertion of two springs (metallic distractors) to promote cranial reshaping. Although safe and effective, SAC outcomes remain uncertain. We aimed hereby to obtain and validate a skull material model for SAC outcome prediction. Computed tomography data relative to 18 patients were processed to simulate surgical cuts and spring location. A rescaling model for age matching was created using retrospective data and validated. Design of experiments was used to assess the effect of different material property parameters on the model output. Subsequent material optimization-using retrospective clinical spring measurements-was performed for nine patients. A population-derived material model was obtained and applied to the whole population. Results showed that bone Young's modulus and relaxation modulus had the largest effect on the model predictions: the use of the population-derived material model had a negligible effect on improving the prediction of on-table opening while significantly improved the prediction of spring kinematics at follow-up. The model was validated using on-table 3D scans for nine patients: the predicted head shape approximated within 2 mm the 3D scan model in 80% of the surface points, in 8 out of 9 patients. The accuracy and reliability of the developed computational model of SAC were increased using population data: this tool is now ready for prospective clinical application.

Papilledema in unicoronal synostosis: a rare finding

OBJECTIVE

Unicoronal synostosis results in frontal plagiocephaly and is preferably treated before the patient is 1 year of age to prevent intracranial hypertension (ICH). However, data on the prevalence of ICH in these patients is currently lacking. This study aimed to establish the prevalence of preoperative and postoperative signs of ICH in a large cohort of patients with unicoronal synostosis and to test whether there is a correlation between papilledema and occipitofrontal head circumference (OFC) curve stagnation in unicoronal synostosis.

METHODS

The authors included all patients with unicoronal synostosis treated before 2 years of age at a single center between 2003 and 2013. The presence of ICH was evaluated by routine fundoscopy. The OFC growth curve was analyzed for deflection and in relationship to signs of ICH.

RESULTS

In total, 104 patients were included in this study, 84 (81%) of whom were considered to have nonsyndromic unicoronal synostosis. Preoperatively, none of the patients had papilledema as determined by fundoscopy (mean age at surgery 11 months). Postoperatively, 5% of patients with syndromic synostosis and 3% of those with nonsyndromic synostosis had papilledema, and this was confirmed by optical coherence tomography. Raised intracranial pressure was confirmed in 1 patient with syndromic unicoronal synostosis. Six of 78 patients had OFC stagnation, which was not significantly correlated to papilledema (p = 0.22). One child with syndromic unicoronal synostosis required repeated surgery for ICH (0.96%).

CONCLUSIONS

Papilledema was not found in patients with unicoronal synostosis when they underwent surgery before the age of 1 year and was also very rare during follow-up. There was no relationship between papilledema and OFC stagnation.