The ramus sustentacularis of the tibialis posterior tendon: An anatomical and histological cadaveric study

BACKGROUND: The tibialis posterior tendon (TPT) is a crucial dynamic stabilizer of the medial longitudinal arch, facilitating midfoot locking and efficient propulsion during gait. While the navicular and cuneiforms are well-established distal insertion sites, an additional posterior band inserting onto the sustentaculum tali-historically termed ramus sustentacularis-has been inconsistently described and never histologically verified. METHODS: Twenty lower limbs from adult cadavers (mean age 81.7 ± 8.6 years; 8 female) were dissected using a standardized protocol. The distal TPT and its sustentacular band were exposed, and the width of the ramus sustentacularis was measured. Representative samples were processed for histological analysis to assess tissue composition and the tendon-bone interface. RESULTS: A distinct posterior band of the TPT inserting onto the anterior surface of the sustentaculum tali was present in all specimens. The band's mean width was 13.9 mm (range 10-17 mm), with no variation by sex or laterality. Histology confirmed dense, longitudinally oriented collagen fibers with parallelly arranged fibrocyte nuclei and no vascular or inflammatory features, consistent with mature tendon tissue. CONCLUSION: This study provides the first histological confirmation of the ramus sustentacularis as a true tendinous structure and a constant component of the TPT's distal footprint. Its consistent presence suggests an overlooked role in hindfoot stabilization and adult-acquired flatfoot deformity pathomechanics. Classical anatomical descriptions should be updated to include the sustentacular band as a standard element of the TPT.