Closure of the anterior and posterior fontanelle in the New Zealand population: A computed tomography study

Abstract

Aim Significant ethnic variation has been demonstrated in the closure of the anterior fontanelle (AF); however, to date, this has not been investigated in the Māori/Pasifika population. Methods The computed tomography scans of 163 individuals (116 Māori/Pasifika and 47 New Zealand (NZ) European) aged between birth and 4 years were retrospectively analysed to investigate the surface area (SA) and time of closure of the anterior and posterior fontanelles in New Zealand. Results The Māori/Pasifika group showed clinical AF closure (SA < 114 mm2) rates of 25% at 4–6 months, increasing to 47% at 10–12 months and 80% at 13–18 months. The posterior fontanelle was clinically unfused in 17% of the Māori/Pasifika group aged <1 month and in 7% of the 1–3‐month‐old group. No cases of posterior fontanelle non‐fusion were identified in the NZ European population. Conclusion This study establishes normal values for AF size and closure frequency for the first time in the paediatric Māori/Pasifika population.

Temporal mapping of the closure of the anterior fontanelle and contiguous sutures using computed tomography, in silico models of modern infants

“…Our statistical projections estimated that a robust sample size of modern Indigenous children for each age cohort would not be attainable from the target hospitals within the data collection period; and we also hypothesise that inclusion of this ancestral group may present as statistical outliers due to suspected differences in socio‐economic status and/or a predisposition to advanced maturation (Garn and Bailey, 1978; Cameron et al , 1993; Bogin, 1999). This statement may be supported by a recent New Zealand study by Kirkpatrick et al (2019). For example, the mean AF surface area (pooled for sex) for Australian infants aged 6–9 months is similar to New Zealand European infants (Australian: 639 mm 2 , NZ European: 650 mm 2 ), but 41% larger than Maori/Pacific infants in the same age cohort.…”

“…This statement may be supported by a recent New Zealand study by Kirkpatrick et al (2019). For example, the mean AF surface area (pooled for sex) for Australian infants aged 6-9 months is similar to New Zealand European infants (Australian: 639 mm 2 , NZ European: 650 mm 2 ), but 41% larger than Maori/Pacific infants in the same age cohort.…”

“…Moffett and Aldridge (2014) report that 15.30% variance in AFSA is attributed to the measurement error between the conventional (Smith and Popich, 1972) and 3D areal protocols, demonstrating that the traditional method is more likely to overestimate AFSA. It is important to reinforce that the quantification of the fibrous membrane for individuals < 6 months postpartum in our study is not restricted to the AF, but includes the contiguous sutures and fontanelles (Figure 3), thus direct comparison with studies employing the conventional methodology to assess AFSA (Ogunye et al , 1982; Chakrabarti, 1989; Mattur et al , 1994; Kirkpatrick et al , 2019) is not possible below this age.…”

“…To overcome the assumption of geometric regularity in conventional AF methodologies (Davies et al , 1975; Hall et al , 2006), Moffett and Aldridge (2014) proposed a new method to quantify the surface area of the AF in Amira ® on MSCT scans of skulls in the Bosma Collection based on the radiodensity of connective tissue via voxel selection. Similarly, Kirkpatrick et al (2019) quantified the surface area of the AF in a non‐accidental MSCT sample of New Zealand infants using 3D oblique multi‐planar reformatting features in OsiriX®. Using a CAD workflow, Lottering et al (2014) proposed an automated areal quantification method in Geomagic Design X TM based on the interpolation of coordinates using the reference geometry of the isosurface.…”

“…Concurrently, the width of the metopic suture starts decreasing (< 2 mm) after 6 days post‐birth in males and 12 days in females, prior to closing between 1 and 2 months, respectively. In an investigation of ethnic differences in time and rate of closure, Kirkpatrick et al (2019) report that the AF is closed by 19 months in New Zealand (NZ) Maori/Pacific infants ( n = 116), whereas 50% of NZ European infants ( n = 47) still present with remnants of an AF in the 19–24 month cohort. Considerable variation in fontanelle size is evident within and across age cohorts, possibly attributable to a small sample size.…”