The Anatomy of the Human Linea Alba: A Systematic Review and Meta-analysis.

BACKGROUND: The linea alba is a key midline structure of the abdominal wall, and its morphology may influence the development of pathologies such as midline hernia and diastasis recti abdominis. However, anatomical and histological findings remain inconsistent. This systematic review aims to synthesize the macroscopic and microscopic features of the human linea alba and evaluate their clinical relevance. METHODS: A comprehensive search was conducted in PubMed, Web of Science, and CINAHL through April 2, 2025. Eligible studies included anatomical or histological investigations of the human linea alba. Three independent reviewers performed data extraction and risk-of-bias assessment. RESULTS: Fifteen studies met the inclusion criteria. Conflicting findings were reported regarding the effects of sex, age, and body mass index, whereas parity and hormonal factors were not studied. Despite methodological heterogeneity, a consistent anatomical trend emerged: the linea alba is widest at the umbilicus and narrowest near the pubic symphysis. Histologically, most studies described a layered collagen structure with ventral oblique and dorsal transverse fibers. Midline fiber decussation was not observed in newer studies, contradicting older models. Meta-analysis showed reduced collagen types I and III in pathological samples. Elastin was seldom examined, and no study evaluated other collagen subtypes, hormonal receptors, or innervation. CONCLUSIONS: Although some structural patterns of the linea alba are consistent, major gaps remain regarding its variability and modifying factors.