Spring-Assisted Cranioplasty for the Correction of Nonsyndromic Scaphocephaly: A Quantitative Analysis of 100 Consecutive Cases

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.

Towards a radiation free numerical modelling framework to predict spring assisted correction of scaphocephaly

Sagittal Craniosynostosis (SC) is a congenital craniofacial malformation, involving premature sagittal suture ossification; spring-assisted cranioplasty (SAC) - insertion of metallic distractors for skull reshaping - is an established method for treating SC. Surgical outcomes are predictable using numerical modelling, however published methods rely on computed tomography (CT) scans availability, which are not routinely performed. We investigated a simplified method, based on radiation-free 3D stereophotogrammetry scans.Eight SAC patients (age 5.1 ± 0.4 months) with preoperative CT and 3D stereophotogrammetry scans were included. Information on osteotomies, spring model and post-operative spring opening were recorded. For each patient, two preoperative models (PREOP) were created: i) CT model and ii) S model, created by processing patient specific 3D surface scans using population averaged skin and skull thickness and suture locations. Each model was imported into ANSYS Mechanical (Analysis System Inc., Canonsburg, PA) to simulate spring expansion. Spring expansion and cranial index (CI - skull width over length) at times equivalent to immediate postop (POSTOP) and follow up (FU) were extracted and compared with in-vivo measurements.Overall expansion patterns were very similar for the 2 models at both POSTOP and FU. Both models had comparable outcomes when predicting spring expansion. Spring induced CI increase was similar, with a difference of 1.2%±0.8% for POSTOP and 1.6%±0.6% for FU.This work shows that a simplified model created from the head surface shape yields acceptable results in terms of spring expansion prediction. Further modelling refinements will allow the use of this predictive tool during preoperative planning.

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.

Posterior Cranial Retraction Combined With Bilateral Parietal Distraction for Children With Nonsyndromic Craniosynostosis

BACKGROUND

The nonsyndromic craniosynostosis is the most common of craniosynostoses in childhood. There are many treatments. We aim to treat 12 cases of nonsyndromic craniosynostosis via posterior cranial vault distraction osteogenesis combined with bilateral parietal distraction.

METHODS

Data of a total of 12 patients (7 boys and 5 girls) with nonsyndromic sagittal synostosis who underwent distraction osteogenesis between January 2015 and August 2020 were retrospectively analyzed. Bilateral parietal bone flaps and posterior occipital flaps were designed and cut. Then, distraction device was placed, which was distracted at 5 days after surgery (twice per day, 0.4-0.6 mm/d, and lasting for 10-15 days). After 6 months of fixation, the secondary surgery was performed to remove the device.

RESULTS

The scaphocephaly was corrected, and the appearance was satisfactory. Postoperative follow-up time was 6 to 14 months, with an average of 10 months, and the mean CI was 63.2 and 78.25 before and after surgery, respectively; the mean anterior-posterior skull diameter was shortened (12.63 ± 3.47) mm, the transverse diameter of both temporal regions was lengthened (15.4 ± 4.18) mm, and the scaphocephalic deformity was significantly improved. There was no detachment or rupture of the extender postoperatively. No severe complications, such as radiation necrosis or intracranial infection, were observed.

CONCLUSION

Posterior cranial retraction combined with bilateral parietal distraction in children with nonsyndromic craniosynostosis, in which the proposed technique did not exhibit severe complications, and it is worthy of further promotion and application in clinical practice.

Initial UK series of endoscopic suturectomy with postoperative helmeting for craniosynostosis: early report of perioperative experience

BACKGROUND

Endoscopic suturectomy with postoperative helmeting (ESCH) has emerged as a successful treatment for craniosynostosis, initially in North America. We report early outcomes from the first cohort of ESCH patients treated in the United Kingdom (UK).

METHODS

Retrospective cohort study with electronic chart review.

RESULTS

18 consecutive patients from the first ESCH procedure in UK (May 2017) until January 2020 identified. 12 male and 6 female infantsd, with a mean age of 4.6 months (range 2.5-7.8 months) and weight of 6.8 kg (range 4.8-9.8 kg). Diagnoses were metopic (n = 8), unicoronal (n = 7), sagittal (n = 2) and multi-sutural (n = 1) synostoses. Median incision length was 3 cm (range 2-10 cm). 16/18 received no blood products, with 2 (both metopics) requiring transfusion (1 donor exposure). Mean operative time (including anaesthesia) was 96 min (range 40-127 min). Median length of hospital stay was 1 night. 1 surgical complication (superficial infection). All patients are currently undergoing helmet orthosis therapy. So far, no patients have required revisional or squint surgery.

CONCLUSION

Early experience from the first UK cohort of ESCH suggests that this is a safe and well tolerated technique with low morbidity, transfusion and short hospital stay. Long-term results in terms of shape, cosmetic and developmental outcome are awaited.

Sagittal synostosis: does choice of intervention and its timing affect the long-term aesthetic and neurodevelopmental outcome? A single-institution study of 167 children

OBJECTIVE

Sagittal craniosynostosis (SC) is the most commonly encountered form of craniosynostosis. Despite its relative frequency, there remains significant heterogeneity in both operative management and follow-up between centers and a relative paucity of long-term outcome data in the literature. At the authors' institution, families of children presenting with SC are offered the following options: 1) conservative management with ophthalmic surveillance, 2) minimally invasive surgery at < 6 months of age (spring-assisted cranioplasty [SAC]) or 3) calvarial vault remodeling at any age (CVR). The authors reviewed outcomes for all children presenting with SC during a 5-year period, regardless of the treatment received.

METHODS

Consecutive children born between January 1, 2008, and December 31, 2012, presenting with SC were identified, and detailed chart reviews were undertaken. Demographic, surgical, perioperative, head shape, scar, and neurodevelopmental (behavioral, education, speech, and language) data were analyzed. The cohort was divided by type of surgery (none, SAC, or CVR) and by age at surgery (early, defined as ≤ 6 months; or late, defined as > 6 months) for comparison purposes.

RESULTS

A total of 167 children were identified, 129 boys and 38 girls, with a median age at presentation of 5.0 (range 0.4-135) months. Three families opted for conservative management. Of the 164 children who underwent surgery, 83 underwent SAC, 76 underwent CVR, and 5 underwent a "hybrid" procedure (CVR with springs). At a median age of 7.0 (range 0.5-12.3) years, there was no significant difference in concerns regarding head shape, scar, or neurodevelopmental outcomes between the early and late intervention groups over all procedures performed, or between the early or late SAC and CVR cohorts. There were more head shape concerns in the SAC group than in the CVR group overall (25.7% vs 11.8%, respectively; p = 0.026), although most of these concerns were minor and did not require revision.

CONCLUSIONS

In this cohort, regardless of operative intervention and timing of intervention, infants achieved similar neurodevelopmental outcomes. Minimally invasive surgery (SAC) appears to result in less complete correction of head shape than CVR, but this may be balanced by advantages in reduced operative time, hospitalization, and blood loss. SAC was equal to CVR in neuropsychological outcomes.

Endoscopic strip craniectomy with molding helmet therapy versus spring-assisted cranioplasty for nonsyndromic single-suture sagittal craniosynostosis: a systematic review

OBJECTIVE

Endoscopic strip craniectomy with postoperative molding helmet therapy (ESC-H) and spring-assisted cranioplasty (SAC) are commonly used minimally invasive techniques for correction of nonsyndromic sagittal craniosynostosis, but it is unclear which, if either, is superior. Therefore, the authors undertook a systematic review to compare ESC-H with SAC for the surgical management of nonsyndromic single-suture sagittal craniosynostosis.

METHODS

Studies were identified through a systematic and comprehensive search of four databases (Embase, MEDLINE, and two databases in the Cochrane Library). Databases were searched from inception until February 19, 2021. Pediatric patients undergoing either ESC-H or SAC for the management of nonsyndromic single-suture sagittal craniosynostosis were included. Systematic reviews and meta-analyses, single-patient case reports, mixed cohorts of nonsyndromic and syndromic patients, mixed cohorts of different craniosynostosis types, and studies in which no outcomes of interest were reported were excluded. Outcomes of interest included reoperations, blood transfusion, complications, postoperative intensive care unit (ICU) admission, operative time, estimated blood loss, length of hospital stay, and cephalic index. Pooled summary cohort characteristics were calculated for each outcome of interest. Methodological quality was assessed using the Newcastle-Ottawa Scale. The study was reported in accordance with the 2020 PRISMA statement.

RESULTS

Twenty-two studies were eligible for inclusion in the review, including 1094 patients, of whom 605 (55.3%) underwent ESC-H and 489 (44.7%) underwent SAC for nonsyndromic sagittal craniosynostosis. There was no difference between the pooled estimates of the ESC-H and SAC groups for operative time, length of stay, estimated blood loss, and cephalic index. There was no difference between the groups for reoperation rate and complication rate. However, ESC-H was associated with a higher blood transfusion rate and higher postoperative ICU admission.

CONCLUSIONS

The available literature does not demonstrate superiority of either ESC-H or SAC, and outcomes are broadly similar for the treatment of nonsyndromic sagittal craniosynostosis. However, the evidence is limited by single-center retrospective studies with low methodological quality. There is a need for international multicenter randomized controlled trials comparing both techniques to gain definitive and generalizable data.

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.

Transverse Distraction Osteogenesis for Posterior Narrowing of the Cranial Vault

SUMMARY

Although conventional posterior vault distraction osteogenesis is known to achieve the greatest improvement in intracranial volume, anteroposterior expansion of the cranial vault is not always ideal in certain head shapes. Transverse posterior vault distraction osteogenesis is an alternative reconstructive strategy in patients presenting with recalcitrant multisuture craniosynostosis resulting in scaphocephaly with posterior narrowing. The authors present a multimedia demonstration of placing the cranial hinge points at the superior anterior aspect of the bone segments in order to achieve increased intracranial volume and significant improvement in posterior head shape, while preserving normal anterior skull dimensions.

Clinical Features and the Use of Three-Dimensional Imaging for Unilateral Lambdoid Synostosis

INTRODUCTION

True isolated lambdoid craniosynostosis is rare. It requires corrective surgery to prevent intracranial pressure and aesthetic stigma by significant dyscrania. We summarize our case series for lambdoid craniosynostosis outlining the pathophysiology, clinical findings and surgical approaches and outcomes.

METHODOLOGY

A retrospective analysis of our data from 2010 to 2020 summarized our cases of true lambdoid synostosis. We have used the medical notes and the radiological findings from computed tomography scans to summarize a case series of isolated lambdoid synostosis.

RESULTS

Our case series demonstrated 7 patients with true isolated lambdoid craniosynostosis. In most cases surgical intervention in the form of posterior cranial vault remodeling utilizing a bandeau, based on occipital advancement techniques, has demonstrated the most consistently favorable aesthetic outcome.

CONCLUSIONS

Surgical referral to a craniofacial center should be sought early in difficult to diagnose cases. Although rare, surgical intervention is indicated to correct potentially increased intracranial pressure and to ameliorate cranial dyscrania.

Validation of an in-silico modelling platform for outcome prediction in spring assisted posterior vault expansion

BACKGROUND

Spring-Assisted Posterior Vault Expansion has been adopted at Great Ormond Street Hospital for Children, London, UK to treat raised intracranial pressure in patients affected by syndromic craniosynostosis, a congenital calvarial anomaly which causes premature fusion of skull sutures. This procedure aims at normalising head shape and augmenting intracranial volume by means of metallic springs which expand the back portion of the skull. The aim of this study is to create and validate a 3D numerical model able to predict the outcome of spring cranioplasty in patients affected by syndromic craniosynostosis, suitable for clinical adoption for preoperative surgical planning.

METHODS

Retrospective spring expansion measurements retrieved from x-ray images of 50 patients were used to tune the skull viscoelastic properties for syndromic cases. Pre-operative computed tomography (CT) data relative to 14 patients were processed to extract patient-specific skull shape, replicate surgical cuts and simulate spring insertion. For each patient, the predicted finite element post-operative skull shape model was compared with the respective post-operative 3D CT data.

FINDINGS

The comparison of the sagittal and transverse cross-sections of the simulated end-of-expansion calvaria and the post-operative skull shapes extracted from CT images showed a good shape matching for the whole population. The finite element model compared well in terms of post-operative intracranial volume prediction (R² = 0.92, p < 0.0001).

INTERPRETATION

These preliminary results show that Finite Element Modelling has great potential for outcome prediction of spring assisted posterior vault expansion. Further optimisation will make it suitable for clinical deployment.

Removal of cranial springs after spring-mediated cranioplasty

Cranial spring hardware is generally removed 3 months after placement for spring-mediated cranioplasty. Spring removal is performed as an outpatient procedure under general anesthesia in approximately 15 minutes through the incision locations of the index procedure. Herein, the authors provide a multimedia demonstration of cranial spring hardware removal after spring-mediated cranioplasty for sagittal craniosynostosis.

The video can be found here: https://vimeo.com/511179695

Spring-mediated cranioplasty for sagittal craniosynostosis

Spring-mediated cranioplasty is a useful treatment modality for correcting scaphocephalic head shape in sagittal craniosynostosis because it is less invasive than whole-vault cranioplasty and offers durable morphologic outcomes. Herein, the authors provide a multimedia demonstration of alternative operative approaches for spring-mediated cranioplasty for sagittal craniosynostosis. The video can be found here: https://vimeo.com/511256259.

Statistical shape modelling for the analysis of head shape variations

The aim of this study is, firstly, to create a population-based 3D head shape model for the 0 to 2-year-old subjects to describe head shape variability within a normal population and, secondly, to test a combined normal and sagittal craniosynostosis (SAG) population model, able to provide surgical outcome assessment. 3D head shapes of patients affected by non-cranial related pathologies and of SAG patients (pre- and post-op) were extracted either from head CTs or 3D stereophotography scans, and processed. Statistical shape modelling (SSM) was used to describe shape variability using two models - a normal population model (MODEL1) and a combined normal and SAG population model (MODEL2). Head shape variability was described via principal components analysis (PCA) which calculates shape modes describing specific shape features. MODEL1 (n = 65) mode 1 showed statistical correlation (p < 0.001) with width (125.8 ± 13.6 mm), length (151.3 ± 17.4 mm) and height (112.5 ± 11.1 mm) whilst mode 2 showed correlation with cranial index (83.5 mm ± 6.3 mm, p < 0.001). The remaining 9 modes showed more subtle head shape variability. MODEL2 (n = 159) revealed that post-operative head shape still did not achieve full shape normalization with either spring cranioplasty or total calvarial remodelling. This study proves that SSM has the potential to describe detailed anatomical variations in a paediatric population.

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.

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.

Three-Dimensional Calvarial Growth in Spring-Assisted Cranioplasty for Correction of Sagittal Synostosis

Spring-assisted cranioplasty (SAC) is a minimally invasive technique for treating sagittal synostosis in young infants. Yet, follow-up data on cranial growth in patients who have undergone SAC are lacking. This project aimed to understand how the cranial shape develops during the postoperative period, from spring insertion to removal. 3D head scans of 30 consecutive infants undergoing SAC for sagittal synostosis were acquired using a handheld scanner pre-operatively, immediately postoperatively, at follow-up and at spring removal; 3D scans of 41 age-matched control subjects were also acquired. Measurements of head length, width, height, circumference, and volume were taken for all subjects; cephalic index (CI) was calculated. Statistical shape modeling was used to compute 3D average head models of sagittal patients at the different time points. SAC was performed at a mean age of 5.2 months (range 3.3-8.0) and springs were removed 4.3 months later. CI increased significantly (P < 0.001) from pre-op (69.5% ± 2.8%) to spring removal (74.4% ± 3.9%), mainly due to the widening of head width, which became as wide as for age-matched controls; however, the CI of controls was not reached (82.3% ± 6.8%). The springs did not constrain volume changes and allowed for natural growth. Population mean shapes showed that the bony prominences seen at the sites of spring engagement settle over time, and that springs affect the overall 3D head shape of the skull. In conclusion, results reaffirmed the effectiveness of SAC as a treatment method for nonsyndromic single suture sagittal synostosis.

Hope Springs Eternal: Insights Into the Durability of Springs to Provide Long-Term Correction of the Scaphocephalic Head Shape

Spring-mediated cranial vault expansion (SMC) has become a primary treatment modality at our institution to correct scaphocephalic head shape in the setting of isolated sagittal craniosynostosis (CS). Spring-mediated cranioplasty is associated with minimal procedural morbidity and reliable clinical efficacy, although long-term outcomes are not well elucidated. Herein we describe our institutional experience and lessons learned with SMC. We hypothesize that SMC performed in young infants offers durable scaphocephalic correction as measured by cephalic index (CI) at the 1, 3, and 5-year postoperative timepoints.Patients with isolated sagittal CS who underwent SMC at our institution during an 8-year period were retrospectively studied. The primary outcome measure was long-term head shape determined by CI at the 1, 3, and 5-year postoperative timepoints. Secondary outcomes included patient and spring factors associated with change in CI, including age and spring force. All statistical tests were 2-tailed with P < 0.05 denoting significance.In total, 88 patients underwent SMC at a median age of 3.3 months with a median preoperative CI 69 (interquartile range: [66, 71]). The postoperative CI increased to 73 [71, 76] at postoperative day 1. At 1 month, the CI increased by 8.6 to 77 (P < 0.0001) and appeared to reach a plateau at 3 months (76, [74, 78]) without further improvement (P < 0.10). At 5 years, CI remained stable without relapse (76, [75, 81], demonstrating an 8.9 increase from preoperative CI. Age at time of spring placement and change in CI were inversely related (P < 0.005). Total spring force directly correlated with increased change in postoperative CI at the 6-month postoperative timepoint (P < 0.02).In summary, SMC offers durable correction of scaphocephaly as measured by CI for patients with isolated sagittal CS at the 5-year postoperative timepoint. The cranial expansion observed 1-month post-spring implantation may serve as a proxy for long-term CI.

Outcomes of Endoscopic Versus Open Spring Assisted Surgery for Sagittal Craniosynostosis

Spring-assisted surgery (SAS) has been shown to be an effective technique for correction of isolated sagittal craniosynostosis in patients less than 6 months of age. At their institution, the authors adopted a minimally invasive technique in 2010, using a shorter incision and an endoscope. A retrospective chart review of 101 patients with isolated, nonsyndromic, sagittal craniosynostosis, who underwent SAS, was performed in order to compare perioperative and clinical outcomes of the open (n = 51) and minimally-invasive (n = 50) approaches. Surgeries were performed by 2 neurosurgeons and 3 plastic surgeons, between 2005 and 2018. The pre and postoperative cephalic indices were not significantly different in both groups. Minimally-invasive spring placement required a longer operative time than the open approach, with the mean minimally-invasive operative time at 65 minutes, compared to 53 minutes (P < 0.0001). Spring removal operative time was not significantly different, with the minimally-invasive operative time at 31 minutes versus 29 minutes (P = 0.48). There were no significant differences in major or minor complications when comparing the open and minimally-invasive approaches. In conclusion, both the open and the minimally-invasive SAS techniques are effective for early correction of isolated sagittal craniosynostosis, although the minimally-invasive approach requires a longer operative time for spring placement.

Visualization of skull remodeling and re-ossification after reconstructive surgery and mosaic-like cranioplasty in sagittal synostosis and deformational brachycephaly1

INTRODUCTION

Extended vertex craniectomy in sagittal synostosis (SS) and transposition craniectomy in severe deformational brachycephaly (DB) combined with mosaic-like cranioplasty (M-LC) have been performed in 17 and 24 infants from 2001 to 2003. The hitherto not well-known mechanisms of remodeling and effectiveness of M-LC is assessed by X-ray and anthropometry.

METHODS

Follow-ups included skull radiograms preoperatively and 3 and 15 months postoperatively, which were analyzed by craniometry according to Haas, long-term anthropometry, and clinical follow-up till mean age of 7.6 and 7.4 years. Analysis included the following: time course of cephalic indexes (CI), sizes of distances (breadth, length, height) and modulus, and mean deviation of distances and modulus from the normal age- and sex-dependent values; evaluation of re-ossification of the operative defects covered by M-L C.

RESULTS

CI in SS is normalized in early follow-up with stabilization thereafter; CI of DB is gradually normalized till late follow-up. Remodeling occurs in both disorders by active and passive mechanisms: increased growth of distances with preoperative minus and decreased growth of distances with surplus. The latter mechanism adds more to the postoperative remodeling. M-LC leads to concentric and final complete re-ossification of the defects.

DISCUSSION

Significant remodeling of the skull vault is observed in both disorders by the demonstrated time course and mechanisms. M-LC does not hinder early remodeling and guarantees re-ossification of the defects.

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.

Short- and Long-Term Outcomes by Procedure Type for Nonsagittal Single-Suture Craniosynostosis

BACKGROUND

Minimally invasive approaches for the treatment of single-suture craniosynostosis are sometimes touted as equivalent to cranial vault reconstruction. While techniques for sagittal synostosis have been reviewed previously, evidence regarding open and less invasive surgical techniques for metopic, coronal, and lambdoid synostosis has yet to be reviewed.

METHODS

Systematic searches were performed using Embase.com and PubMed. Included studies reported short- or long-term outcomes, compared at least 2 standard techniques, discussed single-suture coronal, metopic, or lambdoid craniosynostosis, and enrolled at least 20 study participants. Two authors screened titles and abstracts, and also performed full text review and data extraction. Given heterogeneous outcomes, qualitative synthesis was performed after data extraction.

RESULTS

The search strategy yielded 2348 articles. Of these, 313 were removed as duplicates, and 1935 were excluded during title/abstract review. After full text review of 100 articles, 19 were selected for data extraction. The heterogeneity of outcomes precluded meta-analysis and required qualitative synthesis. While short-term outcomes indicated decreased morbidity of minimally invasive techniques, only 2 articles presented long-term reoperation rates. One study reported higher reoperation rates in the less invasive technique, and the second reported no reoperations in the median follow-up period of 33 months.

CONCLUSION

Studies comparing long-term outcomes between different surgical techniques for single-suture craniosynostosis remain deficient. The development of standardized outcome measures is essential, and prospective, multicenter studies are necessary to assess the long-term efficacy of these procedures.

Spring-Assisted Surgery in the Treatment of Complex Craniosynostosis

Multisutural nonsyndromic craniosynostosis is a rare group of malformations, whose frequency has been reported between 3% and 7% of all craniosynostosis. The clinical diagnosis can be difficult and computed tomography is usually required. Surgical treatment is challenging and staged procedures are performed in up to 80% of patients. The aim of the present study was to determine the reoperation rate and to evaluate the surgical outcomes by measuring intracranial volume (ICV) preoperatively and at follow-up, and comparing it to a control group. Perioperative variables and reoperation rate were recorded. Fifty-one patients presented with a complex pattern of synostosis without a recognizable syndrome (5% of cases of total patients evaluated). Fifteen patients have been treated with spring-assisted surgery, either alone or in combination with a foreheadplasty. The mean follow-up was 6.2 years. The mean preoperative ICV of the patients was smaller, but not significantly, than in the normal population (P = 0.13). Postoperatively, the mean ICV was similar to that of the control group at 1 year (P = 0.92), while at 3 years it was appreciably smaller, although not significantly different (P = 0.06). Five patients (33%) went through a secondary skull expansion for either raised intracranial pressure or cosmetic reasons. Spring-assisted surgery seems to temporarily expand ICV in children with complex synostosis and lower the reoperation rate, thus reducing the need for a second procedure. A longer follow-up would be necessary to further investigate the effects of springs over time.

Assessment of spring cranioplasty biomechanics in sagittal craniosynostosis patients

OBJECTIVE Scaphocephaly secondary to sagittal craniosynostosis has been treated in recent years with spring-assisted cranioplasty, an innovative approach that leverages the use of metallic spring distractors to reshape the patient skull. In this study, a population of patients who had undergone spring cranioplasty for the correction of scaphocephaly at the Great Ormond Street Hospital for Children was retrospectively analyzed to systematically assess spring biomechanical performance and kinematics in relation to spring model, patient age, and outcomes over time. METHODS Data from 60 patients (49 males, mean age at surgery 5.2 ± 0.9 months) who had received 2 springs for the treatment of isolated sagittal craniosynostosis were analyzed. The opening distance of the springs at the time of insertion and removal was retrieved from the surgical notes and, during the implantation period, from planar radiographs obtained at 1 day postoperatively and at the 3-week follow-up. The force exerted by the spring to the patient skull at each time point was derived after mechanical testing of each spring model-3 devices with the same geometry but different wire thicknesses. Changes in the cephalic index between preoperatively and the 3-week follow-up were recorded. RESULTS Stiffer springs were implanted in older patients (p < 0.05) to achieve the same opening on-table as in younger patients, but this entailed significantly different-higher-forces exerted on the skull when combinations of stiffer springs were used (p < 0.001). After initial force differences between spring models, however, the devices all plateaued. Indeed, regardless of patient age or spring model, after 10 days from insertion, all the devices were open. CONCLUSIONS Results in this study provide biomechanical insights into spring-assisted cranioplasty and could help to improve spring design and follow-up strategy in the future.

Statistical shape modelling to aid surgical planning: associations between surgical parameters and head shapes following spring-assisted cranioplasty

PURPOSE

Spring-assisted cranioplasty is performed to correct the long and narrow head shape of children with sagittal synostosis. Such corrective surgery involves osteotomies and the placement of spring-like distractors, which gradually expand to widen the skull until removal about 4 months later. Due to its dynamic nature, associations between surgical parameters and post-operative 3D head shape features are difficult to comprehend. The current study aimed at applying population-based statistical shape modelling to gain insight into how the choice of surgical parameters such as craniotomy size and spring positioning affects post-surgical head shape.

METHODS

Twenty consecutive patients with sagittal synostosis who underwent spring-assisted cranioplasty at Great Ormond Street Hospital for Children (London, UK) were prospectively recruited. Using a nonparametric statistical modelling technique based on mathematical currents, a 3D head shape template was computed from surface head scans of sagittal patients after spring removal. Partial least squares (PLS) regression was employed to quantify and visualise trends of localised head shape changes associated with the surgical parameters recorded during spring insertion: anterior-posterior and lateral craniotomy dimensions, anterior spring position and distance between anterior and posterior springs.

RESULTS

Bivariate correlations between surgical parameters and corresponding PLS shape vectors demonstrated that anterior-posterior (Pearson's [Formula: see text]) and lateral craniotomy dimensions (Spearman's [Formula: see text]), as well as the position of the anterior spring ([Formula: see text]) and the distance between both springs ([Formula: see text]) on average had significant effects on head shapes at the time of spring removal. Such effects were visualised on 3D models.

CONCLUSIONS

Population-based analysis of 3D post-operative medical images via computational statistical modelling tools allowed for detection of novel associations between surgical parameters and head shape features achieved following spring-assisted cranioplasty. The techniques described here could be extended to other cranio-maxillofacial procedures in order to assess post-operative outcomes and ultimately facilitate surgical decision making.

Cranial bone structure in children with sagittal craniosynostosis: Relationship with surgical outcomes

BACKGROUND

While spring-assisted cranioplasty has become a widespread technique to correct scaphocephaly in children with sagittal synostosis, predicting head shape changes induced by the gradual opening of the springs remains challenging. This study aimed to explore the role of cranial bone structure on surgical outcomes.

METHODS

Patients with isolated sagittal synostosis undergoing spring-assisted cranioplasty at GOSH (London, UK) were recruited (n = 18, age: 3-8 months). Surgical outcome was assessed by the change in cephalic index measured on 3D head scans acquired before spring insertion and after their removal using a 3D handheld scanner. Parietal bone samples routinely discarded during spring-assisted cranioplasty were collected and scanned using micro-computed tomography. From visual assessment of such scans, bone structure was classified into one- or three-layered, the latter indicating the existence of a diploë cavity. Bone average thickness, volume fraction and surface density were computed and correlated with changes in cephalic index.

RESULTS

Cephalic index increased for all patients (p < 0.001), but individual improvement varied. Although the patient age and treatment duration were not significantly correlated with changes in cephalic index, bone structural parameters were. The increase of cephalic index was smaller with increasing bone thickness (Pearson's r = -0.79, p < 0.001) and decreasing bone surface density (r = 0.77, p < 0.001), associated with the three-layered bone structure.

CONCLUSIONS

Variation in parietal bone micro-structure was associated with the magnitude of head shape changes induced by spring-assisted cranioplasty. This suggests that bone structure analysis could be a valuable adjunct in designing surgical strategies that yield optimal patient-specific outcomes.