Lateral cephalogram radiograph is mostly used in orthodontics to evaluate and assess the craniofacial morphology to assess distinguish features between the skeletal discrepancies and dentoalveolar malocclusion. Most of the changes in craniofacial morphology occur at the age of 6-18 years in males and 6-15 years in females. The sella turcica is a superior saddle-shaped depression located in the intracranial surface of sphenoid bone, containing the pituitary gland.

It consists of four clinoid processes (two anterior and two posterior), the anterior border represented by tuberculum sellae and the posterior border by the dorsum sellae. The anterior clinoid processes are larger and more diverse. The size and shape of clinoid processes may vary. They can be short and blunt or may protrude above the pituitary fossa and are sometimes connected. The floor of the sella turcica is the pituitary fossa with the pituitary gland.

The sella turcica is variable in size and shape.[2] It can be deep or shallow in both children and adults.[2] Camp[3] has classified normal sella turcica into three types: Circular, oval, or flat; circular was the most frequent, whereas flat was the least. In 70% of children, the sella turcica is round.[2] In profile, the sella at times has a somewhat high concave appearance caused by what appears to be an excavation beneath the anterior clinoids.[2] The floor of the sella turcica, which in most cases is concave, may be flat or even convex.[2] In lateral radiographs, the sella turcica is usually demarcated by a dense thin white line.[2] This feature seems to be more important than the size of the fossa.[2]

The cephalometric radiograph tracing involves the use of many landmarks within the cranium, which are used to measure the relative position of maxilla and mandible to the cranium and to themselves. One such landmark is sella turcica, which has been routinely used in various cephalometric analyses to act as a reference point for evaluating spatial position of both jaws. The sella turcica is located in the middle cranial fossa on the intracranial surface of the body of the sphenoid bone which contains the pituitary gland. On a lateral cephalometric radiograph, the image of sella turcica is “U” shaped. A deviation from normal size and shape of the sella turcica can be an indication of a pathological condition of the pituitary gland. Size of the sella turcica is variable with normal dimensions ranging from an anteroposterior diameter of 5-16 mm and depth of 4-12 mm.

The most frequent abnormality described in the orthodontic literature is sella turcica bridge.[3-7] Bridging is a fusion between the anterior and posterior structures of the sella turcica, specifically a calcification of interclinoid ligament[8-10] or it may be owing to superimposition of sella structures.[7] Sella bridging has been classified by Becktor et al.[7] into two groups:

Type A: Ribbon-like fusion.

A partial calcification of interclinoid ligament is defined as incomplete bridge.[9]

The purpose of this study was to analyze the morphological shape and to measure the linear dimensions of sella turcica to determine if differences exist due to gender or age or in subjects with different skeletal patterns.

This investigation was a cross-sectional comparative study of lateral cephalogram of 100 patients (43 males and 57 females) in the age group of 15-19 years and 20-38 years.

All the lateral cephalograms were taken by the same trained operator on Rotograph Plus, cephalostat machine at 80 kVp, 10 mA, and 0.8 s exposure time using 8×10 inch Kodak green film with the patient’s head in postural position.

The lateral cephalometric records for the patients were selected according to the following criteria:

All patients were above 15 years of age.

This study describes the linear dimensions and morphological appearance of the sella turcica in subjects with different skeletal patterns. The shape variations in the sella turcica have long been reported by many researchers[5-8] who examined the radiographs of children 1-12 years of age and classified the sella turcica into circular, oval, and flattened, or saucer shaped.

In a recent study by Axelsson et al.,[4] the shape of the sella turcica was categorized into six main types; normal sella turcica, oblique anterior wall, double-contoured sella, sella turcica bridge, irregularity (notching) in the posterior part of the sella, and pyramidal shape of the dorsum sellae.

Shah et al.[9] described the morphology of sella turcica and his findings were that morphology was normal in 66% of the subjects and variation was present in 34% of the subjects. Among the variations, irregular dorsum was seen in 16.7%, pyramidal shape in 7.7%, double contour of the floor in 5.5%, oblique anterior wall in 4%, and sella turcica bridging in 0%. The only difference, however, was observed that sella turcica bridging was seen in 8% of the patients.

The presence of a sella turcica bridge in normal individuals is not uncommon and has been shown to occur in 5.5-22% of the subjects,[6,8-11] with an increase in occurrence in patients with craniofacial deviations.

A microsurgical anatomical study of 250 sphenoidal blocks obtained from cadavers, showed that the average width of sella turcica was 12 mm, length (anteroposterior diameter) was 8 mm, and height (vertical diameter) was 6 mm.[12]

One study has described abnormally large or less commonly, small sella turcica.[13-17] Similar results were given in the study conducted in South Indian population, which showed the difference in length of sella turcica between males and females.[14] The radiological diagnosis of an enlarged sella turcica has been found to be associated with adenomas, mucocele, meningioma, primary hypothyroidism, prolactinoma, gigantism, acromegaly, and Nelson syndrome.[17,18] There was a significant increase in the depth and anteroposterior diameter of sella turcica as age increases.[18-21]

Morphological aberrations of the sella turcica described in the literature are bridge, oblique anterior wall, double contour of the floor, irregularity (notching) in the posterior part of the dorsum sellae, and pyramidal shape of the dorsum sellae.[20,21] However, it should be remembered that the two-dimensional representation of an abnormality system does not really provide complete information about its three-dimensional structure. An infinitive number of three-dimensional sizes and shapes can yield an identical two-dimensional radiographic image, which constitutes a well proven mathematical fact inherent to two-dimensional radiography.[21,22]

The findings of the linear dimensions obtained from this study can be used to have an approximate idea of the size of the pituitary gland, which may help the orthodontist when faced with a dilemma of an abnormally large sella turcica on the lateral cephalograms, and this may help the clinician to have a complete knowledge of the different shapes of the sella turcica to distinguish between pathological and normal physiological patterns. Moreover, the growth of the individual can be assessed based on the size of the sella turcica at different age period.

The shape of the sella turcica was normal in 78% of the subjects. Assessment of the sella turcica should be carried out during cephalometric analysis in orthodontic treatment.

When sella size was compared with high and low angle subjects, there was a significant difference in length between high and low angle subjects, where length of the sella turcica was larger in the low angle subjects.

There was no significant difference in length, depth, and diameter of the sella turcica between the two genders and the two age groups, and additionally, a direct correlation was found existed between patients’ age and the diameter of sella turcica and with increasing age; it was noticed that the diameter of the sella turcica was significantly increased.

The distribution of the shape of sella turcica was found to be significantly different among both high and low angle groups wherein the low angle group, pyramidal is the most common type followed by bridging and oblique types, and in the high angle group, oblique and irregular types were the most common types.