Spring-Mediated Cranial Reshaping For Craniosynostosis

Spring-assisted surgery-a surgeon's manual for the manufacture and utilization of springs in craniofacial surgery

BACKGROUND AND PURPOSE

Spring-assisted surgery has been used for the treatment of craniofacial deformities since its 1997 inception in Sweden by Dr Lauritzen (Scand J Plast Reconstr Surg Hand Surg 1998;32:331-338). Initial applications have focused on the treatment of patients with single-suture craniosynostosis. Recently, indications and applications have expanded to include patients with syndromic craniosynostosis, multiple-suture synostosis, and midface hypoplasia. The advancement of spring-assisted surgery in this country has been hindered by the need for patient-specific spring fabrication because few surgeons understand how to make the springs for each application. We will review our spring design and treatment algorithms to facilitate wider use of this innovative treatment modality.

METHODS

This is a retrospective institutional review board-approved analysis of the spring design for our first 90 cases of spring-assisted surgery used to treat sagittal synostosis at the North Carolina Center for Cleft and Craniofacial Deformities. Outcome analysis was done to generate a treatment algorithm based on diagnosis, patient age, spring design, number of springs, spring force and expansion, and clinical outcome.

RESULTS

Ninety children with sagittal craniosynostosis (64 males, 26 females) were treated during an 8-year period (2001-2009) with spring-assisted surgery. Mean age at treatment was 4.4 months and mean age at spring removal was 8.8 months. Mean number of springs used was 2 (range, 1-3). Mean spring force used in sagittal synostosis was 5.5-9.5 (range) for the anterior spring and 5.5-9.5 (range) for the posterior spring with a mean posttreatment expansion of 6.65 cm. Analysis of the results shows that spring force and expansion required for optimal correction is dependent on the age at surgery, type of the deformity, and severity of the deformity. Specifically, the younger the child, the weaker the spring needed for surgical correction. General principles for spring application for scaphocephaly include (1) the longer the anterior posterior dimension of the skull deformity, the more likely a third spring is necessary; (2) the narrower the posterior occiput, the stronger the posterior spring required; and (3) if a postcoronal band is seen in the calvarium, a stronger anterior spring is needed.

CONCLUSIONS

Long-term experience with spring-assisted surgery has facilitated the development of standardized, reproducible techniques allowing spring design modifications to optimize clinical outcome.

Adaptation of the cranium to spring cranioplasty forces

BACKGROUND

During spring-assisted cranioplasty, the spring transmits forces through adjacent cranium. We have previously demonstrated that the ectocranial-endocranial thickness of cranial sutures increases significantly over time in the presence of continuous spring forces. We wished to investigate if cranial bone showed similar adaptational responses.

METHODS

New Zealand white rabbits were randomized into a treatment group [a spring was placed across a posterior frontal suture (PFS) suturectomy and a control group (PFS suturectomy)]. Animals (n = 6) were euthanized from each group at 4, 7, and 10 weeks, respectively. A sham group (n = 6) was euthanized at 10 weeks. Frontal bone thickness was recorded at five reproducible anatomical points on the frontal bone. Histological analysis of the bone architecture was performed.

RESULTS

Frontal bone thickness was significantly greater than controls at all five sites at weeks 7 and 10. There were multiple significant differences between the 4-, 7-, and 10-week groups with each site progressively thickening over time. Histological analysis revealed a uniform increase in thickness of the endocranial and ectocranial cortical bone in the treatment groups.

CONCLUSIONS

Cranial bone adapts to the presence of continuous spring cranioplasty forces by progressively thickening over time. This property is beneficial in craniosynostosis cases with very thin and poor quality bone and may partly explain the observed lack of spring erosion through bone.

Correction of nonsynostotic scaphocephaly without cranial osteotomy: spring expansion of the sagittal suture

BACKGROUND

Scaphocephaly is usually due to sagittal synostosis. Scaphocephaly may also be seen in the presence of a nonsynostosed sagittal suture. In this situation traditional surgery is controversial due to the altered risk-benefit profile. This paper reports the first known series of patients with nonsynostotic scaphocephaly treated using spring assisted expansion of the sagittal suture.

METHODS

All patients referred to our craniofacial program over the period February 2005-February 2008 were retrospectively reviewed. Eleven patients were seen with nonsynostotic scaphocephaly. Seven patients underwent spring expansion of the sagittal suture without osteotomy.

RESULTS

Four female and three male patients had spring expansion of a patent sagittal suture. Four patients were born prematurely. Two patients had Beckwith-Weidemann syndrome. The ages ranged from 6 to 26 months (mean 12 months). The average preoperative cranial index was 66 (range 63-67). This improved to 76 at the time of spring removal (range 73-78). Springs were kept in situ for an average of 7.25 months. The mean blood loss was 7 ml and the mean operative time 36 min.

CONCLUSION

Spring cranioplasty for sagittal synostosis is ideally performed before 6 months of age however in nonsynostotic scaphocephaly older children can be considered due to the absence of frontal bossing. Significant aesthetic improvement was achieved in all cases and normalization of the cranial index was achieved in 86% of cases with minimal morbidity and no significant complications. This technique is an alternative for nonsynostotic cases that were previously either untreated or undergone major remodelling surgery.

Cranial auto graft expansion (CAGE) technique for cranial vault expansion

We present a method for cranial vault expansion that provides a strong construct, leaves small skull defects, and provides bony coverage of the sagittal sinus. The resultant small defects optimize the possibility for spontaneous reossification while avoiding large calvarial defects. This method has been used in 2 children who developed clinical evidence of total cranial growth restriction.

Implications of a vertex bulge following modified strip craniectomy for sagittal synostosis

BACKGROUND

Modified strip craniectomy is a common treatment for early isolated sagittal synostosis. The authors assessed the significance of the development of a progressive vertex bulge following strip craniectomy as a predictor of raised intracranial pressure or multiple suture synostosis.

METHODS

All cases of sagittal synostosis treated by modified strip craniectomy (removal of the sagittal suture with lateral barrel staving) at the authors' institution were reviewed. Eighty-nine patients with isolated sagittal synostosis were treated by modified strip craniectomy, usually before 6 months of age, between 1995 and 2005. Seven patients were noted to have developed a progressive vertex bulge. The vertex bulge was noted an average of 8 months postoperatively (range, 2 to 25 months). The clinical records of these seven patients were evaluated with regard to their clinical course, radiologic investigations, genetics testing, intracranial pressure monitoring, and the need for further surgery.

RESULTS

Computed tomographic scanning demonstrated new synostosis involving other calvarial sutures in five patients. Five patients underwent intracranial pressure monitoring, and this was elevated in four patients. One patient required a ventriculoperitoneal shunt for hydrocephalus. All patients underwent genetic screening, and two were found to have fibroblast growth factor receptor (FGFR) mutations (one FGFR2 and one FGFR3 mutation). All patients required reoperation (calvarial remodeling) for either raised intracranial pressure, deteriorating head shape, or both.

CONCLUSIONS

A progressive vertex bulge after modified strip craniectomy is a sign of possible raised intracranial pressure, the development of progressive multiple suture synostosis, or both. It is an indication for genetic testing for FGFR mutations.

Perioperative management of pediatric patients with craniosynostosis

Craniosynostosis, premature closures of the skull sutures, results in dysmorphic features if left untreated. Brain growth and cognitive development may also be impacted. Craniosynostosis repair is usually performed in young infants and has its perioperative challenges. This article provides background information about the different forms of craniosynostosis, with an overview of associated anomalies, genetic influences, and their connection with cognitive function. It also discusses the anesthetic considerations for perioperative management, including blood-loss management and strategies to reduce homologous blood transfusions.

Priorities for public health research on craniosynostosis: summary and recommendations from a Centers for Disease Control and Prevention-sponsored meeting

On June 8-9, 2006, the National Center on Birth Defects and Developmental Disabilities at the Centers for Disease Control and Prevention held a meeting entitled "Prioritizing a Public Health Research Agenda for Craniosynostosis". The meeting goals were to review current knowledge in the area, discuss research gaps, and identify future priorities for public health research. Participants with a broad range of expertise (including clinical and molecular genetics, cranial morphology, epidemiology, pediatrics, psychology, public health, and surgery) contributed to the development of the research agenda. Meeting participants were asked to consider public health significance and feasibility when identifying areas of priority for future public health research. Participants identified several priorities, including the need to better delineate the prevalence and phenotype of craniosynostosis (CS); to identify factors important in the causation of CS (including potentially modifiable environmental risk factors as well as genes involved in isolated CS and gene-gene and gene-environment interactions); and to better understand short- and long-term outcomes of CS (e.g., surgical, neurocognitive and neuropsychological outcomes, psychological adjustment, and social relationships) and issues related to clinical care that could affect those outcomes. The need for improved collaboration among clinical treatment centers and standardization of data collection to address these priorities was emphasized. These priorities will be used to guide future public health research on CS.

Spring-Assisted Correction of Hypotelorism in Metopic Synostosis

BACKGROUND

Metopic synostosis, apart from the pointed forehead, typically is characterized by hypotelorism with egg-shaped orbits on cephalography and the frontoorbital axis parallel or even converging superiorly. The frontoorbital axis angle is a novel parameter for analyzing and describing the orientation of the orbits. Current methods of surgery often result in undercorrection of the almost ever-present hypotelorism. The present study was performed to analyze a new technique, capable in this respect, using steel wire springs in conjunction with a cranioplasty.

METHODS

A retrospective study of 23 metopic synostosis patients operated on between 1999 and 2004 was conducted. A strip midline craniectomy and frontal reshaping were combined with the insertion of a steel wire spring across the midline craniectomy, forcing lateral displacement of the orbits. Preoperative and postoperative follow-up cephalograms were obtained, and the bony medial interorbital distance was measured and compared with the bony medial interorbital distance of a control group. Perioperative data and complications were noted.

RESULTS

Preoperative mean bony interorbital distance was 10.6 mm (range, 7.7 to 13.2 mm). It increased to 15.7 mm (range, 10.4 to 22 mm) at 1.5 months postoperatively and to 16.2 mm (range, 10.9 to 24.5 mm) 5 months postoperatively. Results as judged clinically ranged from little effect to a definitive overcorrection. The frontoorbital axis was improved in every case. Average frontoorbital axis was -4 degrees (range, -33 to 23 degrees) preoperatively and 28 degrees (range, 11 to 46 degrees) postoperatively.

CONCLUSION

It was concluded that a spring used together with a cranioplasty is a powerful tool for the correction of both hypotelorism and orbital shape in trigonocephaly.

Dynamic Spring Mediated Cranioplasty in an Experimental Model With Resorbable Foot Plates

Craniofacial surgery continues to be progressive in its approach to maximize function and aesthetic appearance while minimizing risks and complications. Dynamic springs are one way to minimize invasiveness while achieving favorable results. The purpose of this study was to show the safety and efficacy of dynamic springs with resorbable foot plates for treatment of metopic suture abnormalities in a swine model. The study population consisted of twelve 20 kg Chester swine. The swine were divided into two treatment groups: four in the sham surgery group and eight in the stainless steel spring group. Postoperative analysis consisted of evaluation of the skull growth over time and integrity of the foot plates and underlying dura. The swine, killed at 8 weeks, were examined for spring location in the foot plates, ease of removal of the spring, and postmortem histologic analysis of the bone growth. No morbidity or mortality occurred in the immediate perioperative period secondary to the surgery. Postmortem histologic analysis revealed no infections or complications related to the surgery. Statistical analysis using a mixed linear model with an unstructured variance-covariance matrix was fit. In conclusion, this study confirms the efficacy and safety of the spring-mediated cranioplasty at the metopic suture with use of resorbable foot plates in a swine model.

New scaphocephaly severity indices of sagittal craniosynostosis: a comparative study with cranial index quantifications

OBJECTIVE

To describe a novel set of scaphocephaly severity indices (SSIs) for predicting and quantifying head- and skull-shape deformity in children diagnosed with isolated sagittal synostosis (ISS) and compare their sensitivity and specificity with those of the traditional cranial index (CI).

METHODS

Computed tomography head scans were obtained from 60 patients diagnosed with ISS and 41 age-matched control patients. Volumetric reformations of the skull and overlying skin were used to trace two-dimensional planes defined in terms of skull-base plane and internal or surface landmarks. For each patient, novel SSIs were computed as the ratio of head width and length as measured on each of these planes. A traditional CI was also calculated and a receiver operating characteristic curve analysis was applied to compare the sensitivity and specificity of the proposed indices with those of CI.

RESULTS

Although the CI is a sensitive measure of scaphocephaly, it is not specific and therefore not a suitable predictor of ISS in many practical applications. The SSI-A provides a specificity of 95% at a sensitivity level of 98%, in contrast with the 68% of CI. On average, the sensitivity and specificity of all proposed indices are superior to those of CI.

CONCLUSIONS

Measurements of cranial width and length derived from planes that are defined in terms of internal or surface landmarks and skull-base plane produce SSIs that outperform traditional CI measurements.

Early surgical treatment of nonsyndromic craniosynostosis

BACKGROUND

Craniosynostosis, a premature fusion of cranial sutures, can happen as an isolated defect (nonsyndromic) or as part of a syndrome. It may lead to raised intracranial pressure and deformity of both the cranial and facial skeletons. Early surgery is usually the best treatment choice. The aim of this study was to review the experience of a multidisciplinary staff with the surgical treatment of nonsyndromic craniosynostosis.

METHODS

All the nonsyndromic craniosynostosis cases treated surgically from 1991 to 2005 at 2 neurosurgical centers were reviewed. The variables analyzed were sex, age, weight, type of deformity, estimated volemia, surgical technique, surgical time, blood loss, PO hospitalization time, and complications. All data were stored in a database and analyzed with Microsoft Access (Microsoft Corp, Seattle, WA) and SPSS V11.0 (SPSS, Inc, Chicago, IL).

RESULTS

The sample consisted of 120 patients (70 males, 50 females). Six patients were excluded because of their atypical timing of treatment (average age, 72 months). The final average age was 7.08 months (variation, 1-18), and the average weight was 7.8 kg. The types of deformities found were scaphocephaly (n = 54, 45%), plagiocephaly (n = 27, 22%), trigonocephaly (n = 19, 16%), brachycephaly (n = 16, 13%), and oxycephaly (n = 4, 3%). The mean surgical time was 186 minutes and the mean PO hospitalization time was 6.8 days. The mortality on this series was 2.6% (3 patients). In the last operated cases, a significant improvement in morbid-mortality was observed.

CONCLUSION

A multidisciplinary approach, including neurosurgeons, neurologists, and pediatricians, and appropriate training of the clinical surgical staff can minimize the risks and decrease the complications in the treatment of craniosynostosis, leading to a satisfactory outcome.