Prevalence and Morphological Spectrum of the Spina Musculi Recti Lateralis and Associated Bony Variants in a Turkish Population: A Combined CT and Dry Skull Study

This study aimed to determine the prevalence and topographical characteristics of the spina musculi recti lateralis (SMRL), a bony projection located on the orbital surface of the greater wing of the sphenoid bone, in a Turkish sample, and to identify accompanying bony variants while emphasizing their clinical importance within the orbital apex. A total of 181 cases (362 orbits) were evaluated retrospectively, including cranial computed tomography (CT) images of 160 adult patients and 21 dry skulls. The presence of SMRL and other bony variants (plaque-type variant, lingula, and tubercle) was recorded; when SMRL was present, the shortest distance to the superior orbital fissure (SOF) was measured. The prevalence of SMRL was 34.8% on a case basis and 28.7% on an orbit basis. Other variants were less frequent: the plaque-type variant was observed in 9.4% of cases, while lingula and tubercle were each detected in 2.2%. No significant correlation was found between the presence of SMRL and age. A sex-related difference was observed, with the plaque-type variant more frequent in male orbits. A significant inverse relationship was identified between SMRL and the plaque-type variant. The mean distance from the SMRL to the anterior margin of the SOF was 7.00 ± 2.47 mm. These findings provide sample-specific data that may contribute to safer surgical planning in the orbital apex.