Subtotal cranial vault remodelling in anterior sagittal suture closure: impact of age on surgical outcome

Abstract

Isolated fusion of the sagittal suture is usually treated before 1 year of age, but some patients present at a later age. The aim of this study was to evaluate the impact of children’s age on the surgical outcome. The authors investigated 46 patients with isolated nonsyndromic sagittal craniosynostosis limited to the anterior two-thirds of the cranial vault. All patients underwent subtotal cranial vault remodelling, 36 patients (78.3%) before the age of 12 months (mean 8.92 months) and 10 patients after the age of 12 months (mean 15.77 months). Perioperative parameters and measurements of the cephalic index, preoperatively and postoperatively, were evaluated. All 46 patients showed improved head shape independent of their age. In patients younger than 12 months, mean cephalic indices improved from 65.99 to 74.49 ( p < 0.0001) and in patients older than 12 months from 66.38 to 74.38 ( p < 0.0004). There were no statistical differences in perioperative parameters including length of surgery, intraoperative blood loss and duration of hospital stay. In this study, patients showed no significant differences in surgical outcome that could have been related to the age at surgery. Surgical treatment should be performed early enough to benefit from the remodelling potential of the skull.

Isolated synostosis of the sagittal suture is the most prevalent form of craniosynostosis with a frequency of one case per 2000–4000 live births. Children with sagittal craniosynostosis have an abnormal skull shape as a result of shortening of the transverse diameter and a compensatory increase in the antero-posterior diameter. The commonly used term, scaphocephaly, describes this anomaly with a long narrow skull in the antero-posterior plane accompanied by frontal and occipital bossing. Depending on the location of the premature fusion along the sagittal suture, sagittal synostosis is present in many different forms. In particular, anterior sagittal suture closure causes frontal bossing ( Fig. 1 ), which requires extensive craniotomy to correct this compensatory growth of the frontal bone. Several surgical procedures have been described in the treatment of scaphocephaly including simple strip craniectomy, H-procedure, pi-procedure, vertex craniectomies and subtotal or total cranial vault remodelling.

Fig. 1
Clinical manifestation of anterior fusion of the sagittal suture with typically shortening of the transverse diameter and a compensatory increase in the antero-posterior diameter with frontal bossing (A). Morphological outcome 2.9 years after surgery (B).

As diagnosis is commonly accomplished without difficulty during the first 12 months and surgery in younger children usually results in minimal impairment of brain development and shows optimal bone regeneration the preferred age for cranial vault expansion is before 1 year of age. Some children present at an older age with previously undiagnosed craniosynostosis. Few studies have focused on these older patients, who might be at a higher risk for elevated intracranial pressure or for developing non-healing cranial bone defects.

Studies that have focused on the influence of the patient’s age on the surgical outcome have revealed conflicting results.

In the present study, the authors investigated a homogenous study population consisting of 46 patients with isolated non-syndromic anterior fusion of the sagittal suture. All patients received a standardized surgical procedure. Patients who underwent surgery before the age of 12 months were compared to patients older than 12 months at the time of surgery in terms of surgical outcome, perioperative parameters and postoperative complications.

Patients and methods

In this retrospective study, the authors reviewed 46 patients with a clinical and radiological diagnosis of isolated nonsyndromic sagittal craniosynostis who underwent subtotal cranial vault remodelling between January 2001 and December 2009 at the Department of Maxillofacial Surgery of the University Heidelberg. All review procedures were in strict accordance with general guidelines and an approved application on file at the authors’ institutional review board. Patients with multisuture or syndromic synostosis were excluded. Patients were only included with anterior fusion of the sagittal suture with frontal bossing to standardize the required surgical procedure. Patients were separated according to their age at surgery and patients who were younger than 12 months at the time of surgery ( n = 36) were compared to patients who underwent surgery when they were older than 12 months ( n = 10). The following data were collected: patient’s sex, age at primary surgery, length of operation, length of hospital stay, signs and symptoms of increased intracranial pressure, postoperative complications, incidence of residual cranial bone defects and preoperative and postoperative head shape as measured by the cephalic index (CI). For the postoperative CI, the CI measured at the last clinical appointment (average follow-up of 54 months) was chosen, to provide information on the long term follow-up of the surgery performed. The CI was calculated from anthropomorphic measurements obtained in the clinic and is defined as the widest dimension of the cranium divided by the maximal length of the cranium multiplied by 100. The perioperative blood loss was calculated using the method previously described by Brecher et al. Aesthetic outcome was rated by the surgeon and the patient’s parents and rated as excellent if both parents and surgeon were satisfied, good if only the parents were satisfied and poor if both the parents and the physician were not satisfied. The Whitaker classification was used to evaluate the surgical results ( Table 1 ). Neurodevelopmental delays were assessed preoperatively using the BSID II (Bayley Scales of Infant Developmental Second Edition), a tool to measure the infant cognitive and motor development standardized for ages from 1 to 42 months.

Table 1
Whitaker classification of surgical results.
Class 2 Soft-tissue or lesser bone-contouring revisions advisable apt to be performed on an outpatient basis or requiring a maximum 2 day hospitalization
Class 3 Major alternative osteotomies or bone grafting procedure advisable (orbital repositions, onlay bone grafts are not as extensive as the original operations)
Class 4 A major craniofacial procedure is advisable, duplicating or exceeding the original operation

Student’s t test was used to compare continuous variables and p -values < 0.05 were considered significant. All statistical analyses were performed using SPSS for Windows version 12.0 (SPSS, Chicago, USA).

The operative procedures were undertaken in association with the neurosurgery team at the authors’ institution. Surgery was performed using a modified surgical procedure originally described by Jane et al. This method uses intraoperative longitudinal compression to shorten the skull dynamically. Of key importance is that the operation focuses more on the areas of compensatory growth than the excision of the pathological sagittal suture. All procedures were carried out through a coronal waveline incision to reduce scar visibility. First, biparietal flaps were fashioned, which extended from the coronal sutures to the lambdoid sutures ( Fig. 2 A) . Second, an osteotomy of the coronal suture is performed, leaving a craniotomy in the shape of the Greek letter pi ( Fig. 2 A). Before the remaining bone elements are brought together, the sagittal sinus must be separated from the overlying bone. As only cases with pronounced frontal bossing were included in this study, the frontal bone was removed after osteotomy approximately 10 mm above the N. supraorbitales and reshaped through radial osteotomies to harmonise the fronto-orbital region ( Fig. 2 B). When the remaining bone elements were re-approximated, the skull length was shortened and actively widened and the frontal bossing was reduced. An even greater shortening of the skull length was achieved by excision of approximately 15 mm of the remaining sagittal bone element before re-approximation. In patients who were operated on between 2001 and 2007, bone elements were refixed with titanium plates, which were removed 6 months after surgery in a second operation. Since 2008, only resorbable mini- or microplates have been used, to avoid a second operation.

Fig. 2
Modified technique of the pi-procedure with osteotomy lines (A) and final vault remodelling (B).

Results

46 children with isolated nonsyndromic sagittal craniosynostosis underwent subtotal cranial vault remodelling; 37 were male (80.4%) and 9 female (19.6%). Follow-up after surgery ranged from 9.3 to 174.4 months, with an average follow-up of 54 months. Children were divided into two groups according to their age at surgery with 12 months being the cut off point. 36 patients underwent surgery before the age of 12 months (mean 8.9 months, range 3.1–11.6 months), and 10 underwent surgery aged over 12 months (mean 15.8 months, range 12.3–19.4 months). Perioperative data for both groups are shown in Table 2 . Intraoperative blood loss was calculated using the method described by Brecher et al. as percentage of the estimated blood volume. There was no statistical difference in blood loss as percentage of estimated blood volume in both groups ( p = 0.708). The operation time for cranial remodelling did not differ statistically for both groups ( p = 0.604) and there were no significant differences in hospital stay in both groups ( p = 0.073).

Table 2
Perioperative data.
p -Value <12 months ( n = 36) >12 months ( n = 10)
Mean Range SD Mean Range SD
Body weight [g] n.s. 8996 6000–11000 1226 8474 6220–11800 1865
Age at surgery [months] <0.0001 8.91 3.10–11.63 1.86 15.77 12.30–19.40 2.73
Duration of operation [min] n.s. 145 65–240 41 130 65–185 34.64
Intraoperative blood loss [% of estimated blood volume] n.s. 43.74 13.89–111.9 23.03 46.64 23.31–70.99 14.22
Duration of postoperative hospital stay [days] n.s. 6.28 4–10 1.23 7.2 5–12 1.93
Follow-up [month] n.s. 54 9.33–174.37 36 62.82 22.83–120.70 30.12

Preoperative and postoperative CI measurements were obtained by anthropomorphic measurements. In both groups, surgical intervention significantly improved the CI. In patients younger than 12 months, mean CI improved from 65.99 to 74.49 ( p < 0.0001) ( Fig. 3 A ) and in patients older than 12 month from 66.38 to 74.38 ( p < 0.0004) ( Fig. 3 B). The difference between preoperative and postoperative CI in patients younger than 12 months (8.5%) did not differ statistically from the difference in CI in patients older than 12 months (8.0%).

Fig. 3
Distribution of pre- and postoperative CI. In patients younger than 12 months at the time of surgery mean CI improved from 65.99 to 74.49 ( p < 0.0001) (A) and in patients older than 12 months from 66.38 to 74.38 ( p < 0.0004) (B). Postoperative CI was measured at the last clinical examination (average follow-up of 54 month).

According to the Whitaker classification, in patients younger than 12 months, 27 patients had a Class 1 outcome, with excellent surgical results, 4 patients were defined as Class 2 and 1 patient as Class 3 ( Table 3 ). Four patients were Class 4 which required a second operation because of a recurrence of scaphocephaly; they showed a good surgical result in their follow up. In patients who were older than 12 months at surgery, 8 patients showed a Class 1 outcome, 1 had Class 2 and 1 had Class 3. No patients were defined as Class 4 ( Table 4 ).

Jan 26, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Subtotal cranial vault remodelling in anterior sagittal suture closure: impact of age on surgical outcome
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