Cirujano

J. Anat. (1988), 161, pp. 203-215
With 9 figures Printed in Great Britain

203

Metopic sutural closure in the human skull
M. C. MANZANARES, M. GORET-NICAISE AND A. DHEM

Human Anatomy Research Unit, Catholic University of Louvain, Tour Vesale 5240, Avenue E. Mounier, 52, B- 1200 Brussels, Belgium

(Accepted 29 March 1988)
INTRODUCTION

The cranial sutures, their closure and theirinfluence on skull growth form one of the most controversial subjects in the field of craniofacial development. Many authors have performed descriptive or experimental studies of cranial sutures and their evolution, either in man (Pritchard, Scott & Girgis, 1956; Moss, 1957; Latham & Burston, 1966; Thilander & Ingervall, 1973; Melsen, 1974; Jane, Edgerton, Futrell & Park, 1978; Dhem, Dambrain,Thauvoy & Stricker, 1983) or in animals (Pritchard et al. 1956; Moss, 1958, 1960; Young, 1959; Herring, 1972, 1974; Koskinen, 1977; Sarnat, 1978, 1986; Markens & Oudhof, 1980; Watzek, Grundschober, Plenk & Eschberger, 1982; Engstr6m, Linde & Thilander, 1982; Persing, Babler, Jane & Duckworth, 1986; Balber, Persing, Nagorsky & Jane, 1987). The metopic suture, considered in the present study, is ofparticular interest because of its early closure which happens at the moment of the loss of deciduous dentition in monkeys, and normally before the second year of life in man (Chopra, 1957). The closure of the rest of the calvarial sutures occurs in man between twenty six and thirty years, with subsidiary periods of activity in the fifties and the late seventies (Todd & Lyon, 1924, 1925 a-c). The aimof this work, entirely based on human autopsy material, is to present the histological and microradiogaphic aspect of the human metopic suture before, during and after its closure.
MATERIAL AND METHODS

The metopic suture region of 53 human subjects, whose ages ranged between 20 weeks of gestational age and 17 months postnatum, was studied. The gestational age was calculated from the last normalmenstrual period of the mother (Jirasek, 1983). The samples, obtained from autopsy material, consisted of the soft tissue of the sutures and the medial borders of the frontal bones, excised 2 cm from the suture, from the nasion to the anterior fontanelle (Fig. 4A). In some cases, due to previous autopsy manipulations, only a part of the suture was available. Samples taken from 32 human subjectswere embedded without decalcification in methyl methacrylate (UCB, Leuven, Belgium) following the procedure described by Vincent (1955), then sectioned at 200 ,tm using an automatic saw (Type 32, Safag, Bienne, Switzerland). The section planes, shown in Figure 4B, were perpendicular to the longitudinal axis of the metopic suture. The samples were reduced to a uniform 80 ,m thickness by manualgrinding on a ground glass plate under methanol. A contact microradiograph was prepared for each section by placing it on a fine grain

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M. C. MANZANARES, M. GORET-NICAISE AND A. DHEM

Kodak Spectroscopic plate 649-0 and exposure to long wavelength X-rays produced by a Machlett tube connected to a Baltograph BF 50/20 (Balteau, Liege). Exposure times, at 13 kV and 18 mA, were 15 minutes for afilm-focus distance of 61 mm and 45 minutes for a film-focus distance of 106 mm. The microradiographic plates were developed for 4 minutes at 20 'C in a D19 (Kodak) solution, fixed and washed under running water, dried, protected from dust and mounted using DPX (BDH Chemicals, Ltd, Poole, England), as for usual histological preparations. In addition samples taken from the metopic region of 21subjects were embedded, after decalcification, in paraffin and the sections were then stained with Masson's trichrome for histological analysis.
RESULTS

During fetal life the two frontal bones are separated by the so-called sutural space; it consists of fibrous tissue and mesenchymal cells responsible for the growth of the frontal bones. As generally considered, this mesenchyme differentiates...