Analysis of the Long-Term Outcomes of Nonsyndromic Bicoronal Synostosis

Neoforehead Remodelling Techniques for Fronto-Orbital Advancement and Remodelling in the Oxford Craniofacial Unit: Lateral Remodelling and a Novel Central Self-Stabilizing S-Osteotomy Technique

Fronto-orbital advancement and remodelling (FOAR) has undergone many modifications over the years, aimed at improving outcomes and reducing risks for patients. This work describes 2 techniques for remodelling the neoforehead used by the Oxford Craniofacial Unit since 1995: lateral remodelling and a central S-Osteotomy. Both methods adopt bone from the vertex as a neoforehead, but they differ in their techniques to adapt its shape to that of the newly remodelled orbital bandeau. The novel S-Osteotomy technique can be successfully applied to all FOAR procedures, irrespective of underlying synostosis and calvarial symmetry. It was originally developed for when 2 separate bony panels were required to create a neoforehead in asymmetrical cases, but was adopted for single panel neoforehead designs in metopic synostosis with the idea it may reduce temporal hollowing. An investigation of temporal hollowing in these patients who underwent either of the described methods was undertaken to assess this hypothesis with no statistically significant difference seen ( P =0.1111). Both techniques on average resulted in minimal hollowing that was not felt to require any revision, supporting the belief that temporal hollowing is a multifactorial issue. This work describes 2 successful methods of neoforehead remodelling and introduces the S-Osteotomy technique that can be applied in all FOAR procedures.

Physiologic Timeline of Cranial-Base Suture and Synchondrosis Closure

BACKGROUND

Fusion of cranial-base sutures/synchondroses presents a clinical conundrum, given their often unclear "normal" timing of closure. This study investigates the physiologic fusion timelines of cranial-base sutures/synchondroses.

METHODS

Twenty-three age intervals were analyzed in subjects aged 0 to 18 years. For each age interval, 10 head computed tomographic scans of healthy subjects were assessed. Thirteen cranial-base sutures/synchondroses were evaluated for patency. Partial closure in greater than or equal to 50 percent of subjects and complete bilateral closure in less than 50 percent of subjects defined the fusion "midpoint." Factor analysis identified clusters of related fusion patterns.

RESULTS

Two hundred thirty scans met inclusion criteria. The sutures' fusion midpoints and completion ages, respectively, were as follows: frontoethmoidal, 0 to 2 months and 4 years; frontosphenoidal, 6 to 8 months and 12 years; and sphenoparietal, 6 to 8 months and 4 years. Sphenosquamosal, sphenopetrosal, parietosquamosal, and parietomastoid sutures reached the midpoint at 6 to 8 months, 8 years, 9 to 11 months, and 12 years, respectively, but rarely completed fusion. The occipitomastoid suture partially closed in less than or equal to 30 percent of subjects. The synchondroses' fusion midpoints and completion ages, respectively, were as follows: sphenoethmoidal, 3 to 5 months and 5 years; spheno-occipital, 9 years and 17 years; anterior intraoccipital, 4 years and 10 years; and posterior intraoccipital, 18 to 23 months and 4 years. The petro-occipital synchondrosis reached the midpoint at 11 years and completely fused in less than 50 percent of subjects. Order of fusion of the sutures, but not the synchondroses, followed the anterior-to-posterior direction. Factor analysis suggested three separate fusion patterns.

CONCLUSIONS

The fusion timelines of cranial-base sutures/synchondroses may help providers interpret computed tomographic data of patients with head-shape abnormalities. Future work should elucidate the mechanisms and sequelae of cranial-base suture fusion that deviates from normal timelines.

Respective Roles of Craniosynostosis and Syndromic Influences on Cranial Fossa Development

BACKGROUND

Little is known about the detailed growth of the cranial fossae, even though they provide an important structural connection between the cranial vault and the facial skeleton. This study details the morphologic development of isolated cranial vault synostosis and associated syndromes on cranial fossa development.

METHODS

A total of 125 computed tomographic scans were included (nonsyndromic bicoronal synostosis, n = 36; Apert syndrome associated with bicoronal synostosis, n = 24; Crouzon syndrome associated with bicoronal synostosis, n = 11; and controls, n = 54). Three-dimensional analyses were produced using Materialise software.

RESULTS

The regional anterior and middle cranial fossae volumes of nonsyndromic bicoronal synostosis are characterized by significant increases of 43 percent (p < 0.001) and 60 percent (p < 0.001), respectively, and normal posterior cranial fossa volume. The cranial fossae depths of nonsyndromic bicoronal synostosis were increased, by 37, 42, and 21 percent (all p < 0.001) for anterior, middle, and posterior cranial fossae, respectively, accompanying the shortened cranial fossae lengths. The volume and morphology of all cranial fossae in Apert syndrome nearly paralleled nonsyndromic bicoronal synostosis. However, Crouzon syndrome had reduced depths of cranial fossae, and more restricted fossa volumes than both Apert syndrome and nonsyndromic bicoronal synostosis.

CONCLUSIONS

Cranial vault suture synostosis is likely to be more influential on cranial fossae development than other associated influences (genetic, morphologic) in Apert and Crouzon syndromes. Isolated Apert syndrome pathogenesis is associated with an elongation of the anterior cranial fossa length in infants, whereas in Crouzon syndrome, there is a tendency to reduce cranial fossa depth, suggesting individual adaptability in cranial fossae development related to vault synostosis.

Postoperative helmet therapy following fronto-orbital advancement and cranial vault remodeling in patients with unilateral coronal synostosis

Out of all the synostotic corrective surgeries, fronto-orbital advancement and cranial vault remodeling for patients with unilateral coronal synostosis is one of the hardest to maintain symmetric and proportional correction without some amount of relapse. Over the course of 20 years operating on these patients, the senior author has made multiple adjustments to compensate for relapse asymmetry, including overcorrection on the affected side, increased points of fixation, periosteal release, and scalp expansion with galeal scoring to minimize tension of the closure. As a result of these interventions, we have seen improved immediate results following surgery. However, we have continued to note clinically significant relapse postoperatively. As such, we have started to implement postoperative helmet therapy (PHT) to help maintain the surgical correction, improve secondary brachycephaly, and increase overall symmetry. PHT is a reasonable low-risk complement to fronto-orbital advancement and cranial vault remolding. Clinically, PHT appears to help minimize relapse and improve overall head symmetry. Further investigation and increased patient enrollment are required to determine the true benefits of PHT in this patient population.

Evolution of Cranioorbital Shape in Nonsyndromic, Muenke, and Saethre-Chotzen Bilateral Coronal Synostosis: A Case-Control Study of 2-Year Outcomes

BACKGROUND

The purpose of this study was to quantify change in cranioorbital morphology from presentation, after fronto-orbital advancement, and at 2-year follow-up.

METHODS

Volumetric, linear, and angular analyses were performed on computed tomographic scans of consecutive bilateral coronal synostosis patients. Comparisons were made across three time points, between syndromic and nonsyndromic cases, and against normal controls. Significance was set at p < 0.05.

RESULTS

Twenty-five patients were included: 11 were nonsyndromic, eight had Saethre-Chotzen syndrome, and six had Muenke syndrome. Total cranial volume was comparable to normal, age-matched control subjects before and 2 years after surgery despite an expansion during surgery. Axial and sagittal vector analyses showed advancement and widening of the lower forehead beyond control values with surgery and comparable anterior position, but increased width compared to controls at 2 years. Frontal bossing decreased with a drop in anterior cranial height and advanced lower forehead position. Middle vault height was not normalized and turricephaly persisted at follow-up. Posterior fossa volume remained lower at all three time points compared to control subjects. Supraorbital retrusion relative to anterior corneal position was overcorrected by surgery, with values comparable to those of control subjects at 2 years because of differential growth. There was no difference at 2 years between syndromic and nonsyndromic groups.

CONCLUSIONS

Open fronto-orbital advancement successfully remodels the anterior forehead but requires overcorrection to be comparable to normal at 2 years. Although there are differences in syndromic cases at presentation, they do not result in significant morphometric differences on follow-up. Posterior fossa volume remains lower at all time points.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Pediatric Fronto-Orbital Skull Reconstruction

Craniofacial surgery in children is a highly challenging discipline that requires extensive knowledge of craniofacial anatomy and pathology. Insults to the fronto-orbital skeleton have the potential to inflict significant morbidity and even mortality in patients due to its proximity to the central nervous system. In addition, significant aesthetic and ophthalmologic disturbances frequently accompany these insults. Craniosynostosis, facial trauma, and craniofacial tumors are all pathologies that frequently affect the fronto-orbital region of the craniofacial skeleton in children. While the mechanisms of these pathologies vary greatly, the underlying principles of reconstruction remain the same. Despite the limited data in certain areas of fronto-orbital reconstruction in children, significant innovations have greatly improved its safety and efficacy. It is imperative that further investigations of fronto-orbital reconstruction are undertaken so that craniofacial surgeons may provide optimal care for these patients.

Orthognathic Surgery in Craniosynostosis

INTRODUCTION

Craniosynostosis is characterized by the fusion of 1 or more sutures of the skull leading to craniofacial deformations. Our aim is to describe the dental malocclusion associated with craniosynostosis, syndromic, or nonsyndromic, and also the treatment used and its stability.

MATERIAL AND METHODS

This retrospective study included all patients who presented at our Department for facial growth monitoring and occlusal management following syndromic and nonsyndromic craniosynostosis. Inclusion began in January 1996 and ended in December 2015 to ensure sufficient follow-up. Orthognathic surgery was performed after the end of growth. Dental occlusion was evaluated clinically and radiographically.

RESULTS

Fifty-five patients were included with 18 syndromic cases. The majority of patients presented with class III malocclusion (69.1%), especially syndromic cases (94.7%) and brachycephalies (96.3%). Conversely, scaphocephalies are associated with class II malocclusions. Thirty-nine patients underwent orthodontic treatment associated with orthognathic surgery to correct their malocclusion. In 4 cases, optimal dental occlusion was achieved with orthodontic treatment alone. Forty patients achieved stable optimal final dental occlusion. Optimal dental occlusion was achieved in 76.9% of the nonsurgically treated craniosynostosis patients and 68.9% of the surgically treated craniosynostosis patients.

DISCUSSION

Sutural fusion induces a facial growth restrictions and dental malocclusions. Several mechanisms may be responsible for these malocclusions: positional anomaly of the jaws due to the cranial deformity, associated anomaly of the facial sutures, or osteocartilagenous system diseases. Early craniosynostosis management does not avoid the occurrence of malocclusion, which will require orthodontic treatment and orthognathic surgery for their management.

Surgical-Orthodontic Considerations in Subcranial and Frontofacial Distraction

Subcranial and frontofacial distraction osteogenesis have emerged as powerful tools for management of hypoplasia involving the upper two-thirds of the face. The primary goal of subcranial or frontofacial distraction is to improve the orientation of the upper face and midface structures (frontal bone, orbitozygomatic complex, maxilla, nasal complex) relative to the cranial base, globes, and mandible. The various techniques used are tailored for management of specific phenotypic differences in facial position and may include segmental osteotomies, differential vectors, or synchronous maxillomandibular rotation.

What remains of non-syndromic bicoronal synostosis?

More and more genetic syndromes are associated with bicoronal synostosis (BCS), making non-syndromic BCS (NSBCS) a shrinking entity. However, the numerical importance and clinical impact of syndromic BCS (SBCS) versus NSBCS have not been much studied. We retrospectively reviewed our experience with BCS over the last four decades in order to compare prevalence trends in SBCS and NSBCS. 195 patients were treated for BCS during the period 1978-2017: 104 (53.3%) were syndromic, 24 (12.3%) showed clinical and/or familial features suggesting a syndrome, although without final diagnostic confirmation, and 7 (3.5%) had associated extra-cranial malformations suggesting a syndromic context without identified genetic mutation; the remaining 61 (31.3%) were purely NSBCS. Surgery was required earlier in SBCS (21.7months, 95%CI 18.4-25.1) than in NSBCS (29.5months 95%CI 26.4-32.7). Prevalence of hydrocephalus and tonsillar herniation was significantly lower in NSBCS, and mortality concerned only SBCS. Prevalence of NSBC decreased significantly over the study period, likely because of more accurate testing, and decreased slightly over the last decade, possibly because of prenatal testing and abortion. NSBCS is now much less common than SBCS, and has a less aggressive clinical course, with lower rates of hydrocephalus, tonsillar herniation and mortality. This subgroup also deserves attention because it is likely that new discoveries are still to be made.

Evaluation of Endoscopic Strip Craniectomy and Orthotic Therapy for Bilateral Coronal Craniosynostosis

BACKGROUND

Bilateral coronal craniosynostosis is the premature fusion of both coronal sutures. Traditionally, this condition is treated by frontal-orbital advancement (FOA). Endoscopic strip craniectomy with cranial orthotic therapy, which has gained popularity in treating single suture craniosynostosis, has recently been adapted for the treatment of bicoronal synostosis. There have been few studies documenting the outcomes of this treatment. The objective of this study is to compare the morphological outcomes of endoscopic strip craniectomy and FOA in patients with bicoronal synostosis.

METHODS

A retrospective case series was done on 24 patients with bilateral coronal synostosis treated with endoscopic strip craniectomy or FOA at 2 institutions. Patients with preoperative and 1-year postoperative computed tomography scans were included. Multiple measures of cranial shape and size were assessed: cephalic index, turricephaly index, basofrontal angle, circumference Z-score, and cranial vault volume Z-score.

RESULTS

The 2 groups were similar statistically in terms of morphology at preoperative scan. There were no statistical differences between the FOA group and endoscopic group at postoperative scan in any of the morphologic outcomes measured. Cranial vault volume Z-scores increased postoperatively in both the endoscopic (P < 0.001) and FOA (P = 0.034) groups.

CONCLUSIONS

One year after repair there were no significant morphological difference between patients with bicoronal synostosis treated with the endoscopic approach and those treated by FOA.

Power-Assisted Particulate Bone Grafting Effectively Prevents Osseous Defects After Cranial Vault Reconstruction

BACKGROUND

Cranial vault reconstruction (CVR) is the gold standard in the operative treatment of craniosynostosis. Full thickness osseous defects (FTOD) of the calvaria have been observed in 5% to 15% patients after CVR, with higher rates cited in the fronto-orbital advancement (FOA) subset. Particulate bone graft (PBG) harvested manually has been shown to decrease FTOD after FOA from 24% to 5.5%. The authors used a modified technique using a powered craniotome, with the hypothesis that the technique would also improve outcomes.

METHODS

A retrospective review was performed of patients who underwent CVR for craniosynostosis between 2004 and 2014. Patient demographics, diagnosis, age, operative details, and postoperative care were reviewed in detail. Categorical, nonparametric variables were compared by Fisher exact tests.

RESULTS

A total of 135 patients met inclusion criteria. The most common diagnoses were metopic (n = 41), sagittal (n = 33), and unilateral coronal craniosynostosis (n = 31); 65% (n = 88) underwent FOA, 29% (n = 39) underwent single-stage total vault reconstruction, and 6% (n = 8) had a posterior vault reconstruction. CVR was performed without PBG in 95 patients and with PBG in 40 patients. Without PBG, FTOD were discovered on clinical examination in 18% of patients (n=17): 11 presented with subcentimeter defects, while 6 had larger defects requiring revision cranioplasty (6% operative revision rate). Among those receiving PBG, 1 patient presented a subcentimeter FTOD (2.5% FTOD incidence and 0% operative revision rate).

CONCLUSION

Particulate bone graft harvested with a powered device decreases the rate of FTOD and reoperation rate after CVR for craniosynostosis.

Multidisciplinary care of craniosynostosis

The management of craniosynostosis, especially in the setting of craniofacial syndromes, is ideally done in a multidisciplinary clinic with a team focused toward comprehensive care. Craniosynostosis is a congenital disorder of the cranium, caused by the premature fusion of one or more cranial sutures. This fusion results in abnormal cranial growth due to the inability of the involved sutures to accommodate the growing brain. Skull growth occurs only at the patent sutures, resulting in an abnormal head shape. If cranial growth is severely restricted, as seen in multisuture craniosynostosis, elevation in intracranial pressure can occur. Whereas most patients treated in a multidisciplinary craniofacial clinic have non-syndromic or isolated craniosynostosis, the most challenging patients are those with syndromic craniosynostosis. The purpose of this article was to discuss the multidisciplinary team care required to treat both syndromic and non-syndromic craniosynostosis.

Endoscopic craniosynostosis repair

INTRODUCTION

Craniosynostosis is a rare condition that affects approximately one child in every 2,000 live births, and involves pathological fusion of two or more skull bones. Consequences of craniosynostosis include possible limitation of brain growth and cosmetic effects on the appearance of the child. Traditional repairs for these conditions over the past 3-4 decades have involved an open operation with a large skin incision and major manipulations of the skull bones. More recently, minimally invasive endoscopic techniques have been developed to release the skull bones, followed by postoperative treatment with either an external orthosis or internal springs and distractors to achieve the desired correction.

METHODS

In this review minimally invasive endoscopic repair will be reviewed. A general overview of the condition and techniques for correction will be discussed, followed by specific application of these surgeries for different craniosynostosis diagnoses. Attention to the subtleties of each specific condition will be highlighted.

SUMMARY

Over the past two decades clinical experience and a large number of publications have substantiated the benefits of minimally invasive endoscopic techniques for the treatment of craniosynostosis. These techniques have clear benefits for selected patients, and should be part of the standard of care for this condition at craniofacial centers.