The mandibular lingula (spine of Spix) in contemporary research: A comprehensive critical review of global morphological variations and clinical implications

The mandibular lingula, historically termed the spine of Spix, represents a critical anatomical landmark in oral and maxillofacial surgery. This comprehensive review synthesises findings from major studies spanning 25 years (2000-2025), encompassing 11,937 + mandibular sides across 19 + populations from six continents. The lingula serves as the primary landmark for inferior alveolar nerve blocks (IANB), sagittal split ramus osteotomy, and various orthognathic procedures. Significant morphological variations exist, with five distinct shapes documented: triangular, truncated, nodular, assimilated, and the recently described bridge/M-shaped morphology (Stipo et al., 2022). A critical methodological bias is evident: dry bone studies predominantly report triangular shapes (39%), while Cone-Beam Computed Tomography (CBCT) studies reveal a nodular predominance (50.6%) in many populations. The internal oblique or mylohyoid ridge has emerged as a reliable alternative landmark (95.7% visibility) and yields superior IANB success rates (97.3%) compared with traditional methods (∼85%). Furthermore, the antilingula is critically evaluated and found to have limited value as a sole landmark. However, it may serve as a supplementary guide when used with appropriate posterior safety margins. This review establishes evidence-based, population-specific surgical protocols, emphasizes the unreliability of traditional assumptions regarding bilateral symmetry, and includes critical appraisal of recent data regarding age-related mandibular remodelling. Comprehensive meta-analytic data representing 4694 subjects provides the most comprehensive morphometric reference values currently available.