A computational modelling tool for prediction of head reshaping following endoscopic strip craniectomy and helmet therapy for the treatment of scaphocephaly.

BACKGROUND: Endoscopic strip craniectomy followed by helmet therapy (ESCH) is a minimally invasive approach for correcting sagittal craniosynostosis. The treatment involves a patient-specific helmet designed to facilitate lateral growth while constraining sagittal expansion. In this study, finite element modelling was used to predict post-treatment head reshaping, improving our comprehension of the necessary helmet therapy duration. METHOD: Six patients (aged 11 weeks to 9 months) who underwent ESCH at Connecticut Children's Hospital were enrolled in this study. Day-1 post-operative 3D scans were used to create skin, skull, and intracranial volume models. Patient-specific helmet models, incorporating areas for growth, were designed based on post-operative imaging. Brain growth was simulated through thermal expansion, and treatments were modelled according to post-operative Imaging available. Mechanical testing and finite element modelling were combined to determine patient-specific mechanical properties from bone samples collected from surgery. Validation compared simulated end-of-treatment skin surfaces with optical scans in terms of shape matching and cranial index estimation. RESULTS: Comparison between the simulated post-treatment head shape and optical scans showed that on average 97.3 ± 2.1 % of surface data points were within a distance range of -3 to 3 mm. The cranial index was also accurately predicted (r = 0.91). CONCLUSIONS: In conclusion, finite element models effectively predicted the ESCH cranial remodeling outcomes up to 8 months postoperatively. This computational tool offers valuable insights to guide and refine helmet treatment duration. This study also incorporated patient-specific material properties, enhancing the accuracy of the modeling approach.

In Vitro Assessment of the Neuro-Compatibility of Fe-20Mn as a Potential Bioresorbable Material for Craniofacial Surgery.

Background and Objectives: Spring-assisted surgery is a popular option for the treatment of non-syndromic craniosynostosis. The main drawback of this procedure is the need for a second surgery for spring removal, which could be avoided if a distractor material could be metabolised over time. Iron-Manganese alloys (FeMn) have a good trade-off between degradation rate and strength; however, their biocompatibility is still debated. Materials and Methods: In this study, the neuro-compatibility of Fe-20Mn (wt.%) was assessed using standard assays. PC-12 cells were exposed to Fe-20Mn (wt.%) and stainless steel via indirect contact. To examine the cytotoxicity, a Cell Tox Green assay was carried out after 1, 2, and 3 days of incubation. Following differentiation, a neurite morphological examination after 1 and 7 days of incubation time was carried out. The degradation response in modified Hank's solution at 1, 3, and 7 days was investigated, too. Results: The cytotoxicity assay showed a higher toxicity of Fe-20Mn than stainless steel at earlier time points; however, at the latest time point, no differences were found. Neurite morphology was similar for cells exposed to Fe-20Mn and stainless steel. Conclusions: In conclusion, the Fe-20Mn alloy shows promising neuro-compatibility. Future studies will focus on in vivo studies to confirm the cellular response to Fe-20Mn.

What can a morphometric study of unoperated children teach us about the natural history of metopic synostosis?

OBJECTIVE: Outcomes of surgical repair of trigonocephaly are well reported in the literature, but there is a paucity of information on the natural history of unoperated children. The authors evaluated a group of unoperated children with metopic synostosis to describe the natural change in head shape over time. METHODS: A database was screened for scans of children with unoperated trigonocephaly (2010-2021). Multisuture cases and those with a metopic ridge were excluded. Three-dimensional surface scans (3D stereophotogrammetry/CT) were used for morphological analysis. Nine previously published parameters were used: frontal angle (FA30°), anteroposterior (AP) volume ratio (APVR), AP area ratio (APAR), AP width ratios 1 and 2 (APWR1 and APWR2), and 4 AP diagonal ratios (30° right APDR [rAPDR30], 30° left APDR [lAPDR30], 60° right APDR [rAPDR60], and 60° left APDR [lAPDR60]). RESULTS: Ninety-seven scans were identified from a cohort of 316 patients with a single metopic suture, in which the male-to-female ratio was 2.7:1. Ages at the time of the scan ranged from 9 days to 11 years and were stratified into 4 groups: group 1, < 6 months; group 2, 6-12 months; group 3, 1-3 years; and group 4, > 3 years. Significant improvements were detected in 5 parameters (APVR, APAR, APWR1, rAPDR30, and lAPDR30) over time, whereas no significant differences were found in FA30, APWR2, rAPDR60, and lAPDR60 between age groups. CONCLUSIONS: Forehead shape (surface area and volume), as well as narrowing and anterolateral contour at the frontal points, differed significantly over time without surgery. However, forehead angulation, narrowing, and anterolateral contour at temporal points did not show significant differences. This knowledge will aid in surgical and parental decision-making.

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.

Spring-assisted cranioplasty (SAC) ­insertion of metallic distractors helping skull reshaping ­ is a method for treating sagittal craniosynostosis, caused by premature sagittal suture closure. We present a method for predicting SAC outcomes, relying on radiation-free 3D stereophotogrammetry scans. Eight patients with preoperative CT and 3D stereophotogrammetry scans were recruited; results of spring expansion simulation were compared between models created using CT versus 3D scan data. Expansion patterns and extent of reshaping were very similar. This work proves that SAC preoperative planning can be carried out using non-ionising imaging. Further modelling refinements will allow clinical adoption of this predictive tool.

Soft tissue prediction in orthognathic surgery: Improving accuracy by means of anatomical details.

Three-dimensional virtual simulation of orthognathic surgery is now a well-established method in maxillo-facial surgery. The commercial software packages are still burdened by a consistent imprecision on soft tissue predictions. In this study, the authors produced an anatomically detailed patient specific numerical model for simulation of soft tissue changes in orthognathic surgery. Eight patients were prospectively enrolled. Each patient underwent CBCT and planar x-rays prior to surgery and in addition received an MRI scan. Postoperative soft-tissue change was simulated using Finite Element Modeling (FEM) relying on a patient-specific 3D models generated combining data from preoperative CBCT (hard tissue) scans and MRI scans (muscles and skin). An initial simulation was performed assuming that all the muscles and the other soft tissue had the same material properties (Homogeneous Model). This model was compared with the postoperative CBCT 3D simulation for validation purpose. Design of experiments (DoE) was used to assess the effect of the presence of the muscles considered and of their variation in stiffness. The effect of single muscles was evaluated in specific areas of the midface. The quantitative distance error between the homogeneous model and actual patient surfaces for the midface area was 0.55 mm, standard deviation 2.9 mm. In our experience, including muscles in the numerical simulation of orthognathic surgery, brought an improvement in the quality of the simulation obtained.

Evaluation of Research Diagnostic Criteria in Craniofacial Microsomia.

Characteristics of patients with craniofacial microsomia (CFM) vary in type and severity. The diagnosis is based on phenotypical assessment and no consensus on standardized clinical diagnostic criteria is available. The use of diagnostic criteria could improve research and communication among patients and healthcare professionals. Two sets of phenotypic criteria for research were independently developed and based on multidisciplinary consensus: the FACIAL and ICHOM criteria. This study aimed to assess the sensitivity of both criteria with an existing global multicenter database of patients with CFM and study the characteristics of patients that do not meet the criteria. A total of 730 patients with CFM from were included. Characteristics of the patients were extracted, and severity was graded using the O.M.E.N.S. and Pruzansky-Kaban classification. The sensitivity of the FACIAL and ICHOM was respectively 99.6% and 94.4%. The Cohen's kappa of 0.38 indicated a fair agreement between both criteria. Patients that did not fulfill the FACIAL criteria had facial asymmetry without additional features. It can be concluded that the FACIAL and ICHOM criteria are accurate criteria to describe patients with CFM. Both criteria could be useful for future studies on CFM to create comparable and reproducible outcomes.

Frontofacial Surgery: Reducing Infection with the Development and 6-Year Outcome of a Frontofacial Protocol.

BACKGROUND: Frontofacial surgery (FFS) creates a communication between the cranial and nasal cavities and is associated with significant infection risk. After a cluster of infections affecting patients undergoing FFS, a root cause analysis of index cases was undertaken, but no specifically remedial causes were identified. Basic principles incorporating known risk factors for the prevention of surgical-site infection were then applied to the creation of a perioperative management protocol. This study analyzes infection rates before and after its implementation. METHODS: The protocol was designed around the needs of patients undergoing FFS and consists of three checklists covering their preoperative, intraoperative, and postoperative care. Compliance required the completion of each checklist. All patients undergoing FFS between 1999 and 2019 were studied retrospectively, and infections occurring before and after the implementation of the protocol were analyzed. RESULTS: One hundred three patients underwent FFS (60 monobloc and 36 facial bipartition) before the implementation of the protocol in August of 2013, and 30 patients underwent FFS after its implementation. Compliance with the protocol was 95%. After implementation, there was a statistically significant reduction in infections from 41.7% to 13.3% ( P = 0.005). CONCLUSIONS: Although no specific cause for a cluster of postoperative infection had been identified, the implementation of a bespoke protocol consisting of preoperative, perioperative, and postoperative checklists covering measures known to reduce infection risk was associated with a significant reduction in postoperative infections in patients undergoing FFS. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.

Comparison of Internal and External Distraction in Frontofacial Monobloc Advancement: A Three-Dimensional Quantification.

BACKGROUND: Crouzon syndrome is characterized by complex craniosynostosis and midfacial hypoplasia. Where frontofacial monobloc advancement (FFMBA) is indicated, the method of distraction used to achieve advancement holds an element of equipoise. This two-center retrospective cohort study quantifies the movements produced by internal or external distraction methods used for FFMBA. Using shape analysis, this study evaluates whether the different distraction forces cause plastic deformity of the frontofacial segment, producing distinct morphologic outcomes. METHODS: Patients with Crouzon syndrome who underwent FFMBA with internal distraction [Hôpital Necker-Enfants Malades (Paris, France)] or external distraction [Great Ormond Street Hospital for Children (London, United Kingdom)] were compared. Digital Imaging and Communications in Medicine files of preoperative and postoperative computed tomographic scans were converted to three-dimensional bone meshes and skeletal movements were assessed using nonrigid iterative closest point registration. Displacements were visualized using color maps and statistical analysis of the vectors was undertaken. RESULTS: Fifty-one patients met the strict inclusion criteria. Twenty-five underwent FFMBA with external distraction and 26 with internal distraction. External distraction provides a preferential midfacial advancement, whereas internal distractors produce a more positive movement at the lateral orbital rim. This confers good orbital protection but does not advance the central midface to the same extent. Vector analysis confirmed this to be statistically significant ( P < 0.01). CONCLUSIONS: Morphologic changes resulting from monobloc surgery differ depending on the distraction technique used. Although the relative merits of internal and external distraction still stand, it may be that external distraction is more suited to addressing the midfacial biconcavity seen in syndromic craniosynostosis. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.

Two-Center Review of Posterior Vault Expansion following a Staged or Expectant Treatment of Crouzon and Apert Craniosynostosis.

BACKGROUND: The timing of posterior cranial expansion for the management of intracranial pressure can be "staged" by age and dysmorphology or "expectant" by pressure monitoring. The authors report shared outcome measures from one center performing posterior vault remodeling (PCVR) or distraction (PVDO) following a staged approach and another performing spring-assisted expansion (SAPVE) following an expectant protocol. METHODS: Apert or Crouzon syndrome patients who underwent posterior expansion younger than 2 years were included. Perioperative outcomes and subsequent cranial operations were recorded up to last follow-up and intracranial volume changes measured and adjusted using growth curves. RESULTS: Thirty-eight patients were included. Following the expectant protocol, Apert patients underwent SAPVE at a younger age (8 months) than Crouzon patients (16 months). The initial surgery time was shorter but total operative time, including device removal, was longer for PVDO (3 hours 52 minutes) and SAPVE (4 hours 34 minutes) than for PCVR (3 hours 24 minutes). Growth-adjusted volume increase was significant and comparable. Fourteen percent of PCVR, 33% of PVDO, and 11% of SAPVE cases had complications, but without long-term deficits. Following the staged approach, 5% underwent only PVDO, 85% had a staged posterior followed by anterior surgery, and 10% required a third expansion. Following the expectant approach, 42% of patients had only posterior expansion at last follow-up, 32% had a secondary cranial surgery, and 26% had a third cranial expansion. CONCLUSION: Two approaches involving posterior vault expansion in young syndromic patients using three techniques resulted in comparable early volume expansion and complication profiles. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.

Does the Mutation Type Affect the Response to Cranial Vault Expansion in Children With Apert Syndrome?

LEVEL OF EVIDENCE: III.

Upper and Lower Limb Anomalies in Craniofacial Microsomia and Its Relation to the OMENS+ Classification: A Multicenter Study of 688 Patients.

BACKGROUND: Craniofacial microsomia (CFM) is characterized by several malformations related to the first and second pharyngeal arch. Patients typically present with facial asymmetry, but extracraniofacial organ systems might be involved, including limb anomalies. The purpose of this study was to analyze the occurrence of upper and lower limb anomalies in CFM patients. Furthermore, the relation between limb anomalies and the OMENS+ (orbital distortion; mandibular hypoplasia; ear anomaly; nerve involvement; soft-tissue deficiency; and associated extracraniofacial anomalies) classification was examined. METHODS: A retrospective study was conducted including patients with CFM from craniofacial units in three different countries. Patients were included when clinical and/or radiographic images were available. Demographic, radiographic, and clinical information was obtained. RESULTS: A cohort of 688 patients was available and selected for analysis. In total, 18.2% of the patients were diagnosed with at least one upper and/or lower limb anomaly. Upper and lower limb anomalies were seen in, respectively, 13.4% and 7.8% of patients. Patients with other extracraniofacial anomalies had a significantly higher risk for limb anomalies (OR, 27.98; P = 0.005). Laterality of CFM and a higher OMENS score were not associated with limb anomalies. CONCLUSIONS: More than one in six patients with craniofacial microsomia have limb anomalies. Therefore, clinical awareness for these anomalies is warranted. Examination and, if present, follow-up on limb abnormalities in patients with CFM should be implemented in the standard assessment of CFM patients. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, III.

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.

The Accuracy of Computer-Assisted Surgical Planning in Predicting Soft Tissue Responses After Le Fort I Osteotomy: Retrospective Analysis.

PURPOSE: Mismatch between preoperative planning and surgical outcome in maxillofacial surgery relate to on-table replication of presurgical planning and predictive algorithm inaccuracy: software error was hereby decoupled from planning inaccuracy to assess a commercial software. The hypothesis was that soft tissue prediction error would be minimized if the surgical procedure was replicated precisely as planned and is independent of the extent of bone repositioning. MATERIALS AND METHODS: Cone-beam computed tomography scans of 16 Le Fort I osteotomy patients were collected at Boston Children's Hospital. Preoperative and postoperative models of bone and soft tissue were constructed and the maxilla repositioning was replicated. Each model was subdivided into 6 regions: mouth, nose, eyes, and cheeks. Soft tissue prediction (performed using Proplan CMF-Materialise) for each patient was compared with the relative postoperative reconstruction and error was determined. P <0.05 was considered significant. RESULTS: Le Fort I segment repositioning was replicated within 0.70±0.18 mm. The highest prediction error was found in the mouth (1.49±0.77 mm) followed by the cheeks (0.98±0.34 mm), nose (0.86±0.23 mm), and eyes (0.76±0.32). Prediction error on cheeks correlated significantly with mouth ( r =0.63, P < 0.01) and nose ( r =0.67, P < 0.01). Mouth prediction error correlated with total advancement ( r =0.52, P =0.04). CONCLUSIONS: ProPlan CMF is a useful outcome prediction tool; however, accuracy decreases with the extent of maxillary advancement even when errors in surgical replication are minimized.

3-Dimensional Morphometric Outcomes After Endoscopic Strip Craniectomy for Unicoronal Synostosis.

BACKGROUND: Endoscopic strip craniectomy with postoperative helmeting (ESCH) for unicoronal synostosis has shown to be a less morbid procedure when compared with fronto-orbital remodeling (FOR). We aim in this pilot study to report objective methods and quantitative morphologic outcomes of endoscopically treated unicoronal synostosis using 3-dimensional surface scans. METHODS: Our electronic records were reviewed for ophthalmological, neurodevelopmental outcomes, and helmet-related complications. For morphologic outcomes, the following parameters were used: Cranial Index, Cranial Vault Asymmetry Index, Anterior Symmetry Ratio (ASR), and Root Mean Square between the normal and synostotic sides of the head. Three-dimensional stereophotogrammetry scans were evaluated at 3 time points preoperative, 6 months post-op, and at the end of the treatment, which was compared with age-matched scans of normal controls and FOR patients. Nonparametric tests were used for statistical analysis. RESULTS: None of the ESCH cases developed strabismus, major neurodevelopmental delay, or helmet complications. All morphologic parameters improved significantly at 6 months post-op except for the Cranial Vault Asymmetry Index. The ASR was the only parameter to change significantly between 6 months post-op and final scans. At end of helmet treatment, ASR and Root Mean Square differed significantly between the ESCH and both FOR and control groups. CONCLUSIONS: Endoscopic strip craniectomy with postoperative helmeting for single unicoronal synostosis had excellent clinical outcomes. Most of the improvement in head morphology occurred in the first 6 months of treatment. Despite the normalization of the overall head shape, there was residual asymmetry in the frontal and temporal regions of the head.

Correction of trigonocephaly after endoscopic strip craniectomy with postoperative helmet orthosis therapy: a 3D stereophotogrammetric study.

OBJECTIVE: Endoscopic strip craniectomy with postoperative helmet orthosis therapy (ESCH) has emerged as a less invasive alternative to fronto-orbital remodeling for correction of trigonocephaly. However, there is no standardized objective method for monitoring morphological changes following ESCH. Such a method should be reproducible and avoid the use of ionizing radiation and general anesthesia for diagnostic imaging. The authors analyzed a number of metrics measured using 3D stereophotogrammetry (3DSPG) following ESCH, an imaging alternative that is free of ionizing radiation and can be performed on awake children. METHODS: 3DSPG images obtained at two time points (perisurgical and 1-year follow-up [FU]) of children with metopic synostosis who had undergone ESCH were analyzed and compared to 3DSPG images of age-matched control children without craniofacial anomalies. In total, 9 parameters were measured, the frontal angle and anteroposterior volume in addition to 7 novel parameters: anteroposterior area ratio, anteroposterior width ratios 1 and 2, and right and left anteroposterior diagonal ratios 30 and 60. RESULTS: Six eligible patients were identified in the operated group, and 15 children were in the control group. All 9 parameters differed significantly between perisurgical and age-matched controls, as well as from perisurgical to FU scans. Comparison of FU scans of metopic synostosis patients who underwent surgery to scans of age-matched controls without metopic synostosis revealed that all parameters were statistically identical, with the exception of the right anteroposterior diagonal ratio 30, which was not fully corrected in the treated patients. The left anterior part of the head showed the most change in surface area maps. CONCLUSIONS: In this pilot study, ESCH showed satisfactory results at 1 year, with improvements in all measured parameters compared to perisurgical results and normalization of 8 of 9 parameters compared to an age-matched control group. The results indicate that these parameters may be useful for craniofacial units for monitoring changes in head shape after ESCH for trigonocephaly and that 3DSPG, which avoids the use of anesthesia and ionizing radiation, is a satisfactory monitoring method.

Finite element method for the design of implants for temporal hollowing.

Temporal indentations are the most impacting craniofacial complication after coronal flap dissection. It is mainly due to a temporal fat pad or temporalis muscle dissection. Because of the great improvements achieved recently in CAD-CAM-aided surgery and the possibility of performing accurate pre-surgical virtual planning, it is now possible to correct it with a customised virtual approach. Furthermore, advancements in material science have allowed surgeons to rely on biocompatible materials like PEEK (showing a low complication and recurrence rate) for the manufacturing of patient-specific implants. We hereby describe our experience on a case of secondary and corrective surgery after a fronto-orbital remodelling, in which we used PEEK implants designed by CAD and optimized by finite element modelling.

Correlation between head shape and volumetric changes following spring-assisted posterior vault expansion.

The aim of the study was to investigate whether different head shapes show different volumetric changes following spring-assisted posterior vault expansion (SA-PVE) and to investigate the influence of surgical and morphological parameters on SA-PVE. Preoperative three-dimensional skull models from patients who underwent SA-PVE were extracted from computed tomography scans. Patient head shape was described using statistical shape modelling (SSM) and principal component analysis (PCA). Preoperative and postoperative intracranial volume (ICV) and cranial index (CI) were calculated. Surgical and morphological parameters included skull bone thickness, number of springs, duration of spring insertion and type of osteotomy. In the analysis, 31 patients were included. SA-PVE resulted in a significant ICV increase (284.1 ± 171.6 cm3, p < 0.001) and a significant CI decrease (-2.9 ± 4.3%, p < 0.001). The first principal component was significantly correlated with change in ICV (Spearman ρ = 0.68, p < 0.001). Change in ICV was significantly correlated with skull bone thickness (ρ = -0.60, p < 0.001) and age at time of surgery (ρ = -0.60, p < 0.001). No correlations were found between the change in ICV and number of springs, duration of spring insertion and type of osteotomy. SA-PVE is effective for increasing the ICV and resolving raised intracranial pressure. Younger, brachycephalic patients benefit more from surgery in terms of ICV increase. Skull bone thickness seems to be a crucial factor and should be assessed to achieve optimal ICV increase. In contrast, insertion of more than two springs, duration of spring insertion or performing a fully cut through osteotomy do not seem to impact the ICV increase. When interpreting ICV increases, normal calvarial growth should be taken into account.

Spring-assisted posterior vault expansion-a single-centre experience of 200 cases.

PURPOSE: Children affected by premature fusion of the cranial sutures due to craniosynostosis can present with raised intracranial pressure and (turri)brachycephalic head shapes that require surgical treatment. Spring-assisted posterior vault expansion (SA-PVE) is the surgical technique of choice at Great Ormond Street Hospital for Children (GOSH), London, UK. This study aims to report the SA-PVE clinical experience of GOSH to date. METHODS: A retrospective review was carried out including all SA-PVE cases performed at GOSH between 2008 and 2020. Demographic and clinical data were recorded including genetic diagnosis, craniofacial surgical history, surgical indication and assessment, age at time of surgery (spring insertion and removal), operative time, in-patient stay, blood transfusion requirements, additional/secondary (cranio)facial procedures, and complications. RESULTS: Between 2008 and 2020, 200 SA-PVEs were undertaken in 184 patients (61% male). The study population consisted of patients affected by syndromic (65%) and non-syndromic disorders. Concerns regarding raised intracranial pressure were the surgical driver in 75% of the cases, with the remainder operated for shape correction. Median age for SA-PVE was 19 months (range, 2-131). Average operative time for first SA-PVE was 150 min and 87 for spring removal. Median in-patient stay was 3 nights, and 88 patients received a mean of 204.4 ml of blood transfusion at time of spring insertion. A single SA-PVE sufficed in 156 patients (85%) to date (26 springs still in situ at time of this analysis); 16 patients underwent repeat SA-PVE, whilst 12 underwent rigid redo. A second SA-PVE was needed in significantly more cases when the first SA-PVE was performed before age 1 year. Complications occurred in 26 patients with a total of 32 events, including one death. Forty-one patients underwent fronto-orbital remodelling at spring removal and 22 required additional cranio(maxillo)facial procedures. CONCLUSIONS: Spring-assisted posterior vault expansion is a safe, efficient, and effective procedure based on our 12-year experience. Those that are treated early in life might require a repeat SA-PVE. Long-term follow-up is recommended as some would require additional craniomaxillofacial correction later in life.

Local Soft Tissue and Bone Displacements Following Midfacial Bipartition Distraction in Apert Syndrome - Quantification Using a Semi-Automated Method.

ABSTRACT: Patients with Apert syndrome experience midfacial hypoplasia, hypertelorism, and downslanting palpebral fissures which can be corrected by midfacial bipartition distraction with rigid external distraction device. Quantitative studies typically focus on quantifying rigid advancement and rotation postdistraction, but intrinsic shape changes of bone and soft tissue remain unknown. This study presents a method to quantify these changes. Pre- and post-operative computed tomography scans from patients with Apert syndrome undergoing midfacial bipartition distraction with rigid external distraction device were collected. Digital Imaging and Communications in Medicine files were converted to three-dimensional bone and soft tissue reconstructions. Postoperative reconstructions were aligned on the preoperative maxilla, followed by nonrigid iterative closest point transformation to determine local shape changes. Anatomical point-to-point displacements were calculated and visualized using a heatmap and arrow map. Nine patients were included.Zygomatic arches and frontal bone demonstrated the largest changes. Mid-lateral to supra-orbital rim showed an upward, inward motion. Mean bone displacements ranged from 3.3 to 12.8 mm. Soft tissue displacements were relatively smaller, with greatest changes at the lateral canthi. Midfacial bipartition distraction with rigid external distraction device results in upward, inward rotation of the orbits, upward rotation of the zygomatic arch, and relative posterior motion of the frontal bone. Local movements were successfully quantified using a novel method, which can be applied to other surgical techniques/syndromes.