The contribution of tibiocalcaneal fibres to talonavicular axis stability - A cadaver based randomised trial

The deltoid-spring ligament complex (DSL) is recognised as an integrated stabilising structure of the ankle-hindfoot complex; however, the relative contributions of its individual components to talonavicular joint (TNJ) stability remain incompletely defined. While the tibiocalcaneal (TC) fibres are known to influence ankle and subtalar mechanics, their role in TNJ abduction stability has not previously been experimentally assessed.

To quantify the contribution of the tibiocalcaneal fibres to talonavicular joint abduction stability (primary outcome, degrees) and hindfoot eversion (secondary outcome, millimetres), and to compare their effect with that of other DSL components using a paired cadaveric sectioning model.

Eighteen embalmed cadaveric lower limbs were tested under controlled, non-weight-bearing conditions. Specimens were randomised to anterior-posterior or posterior-anterior sequential sectioning of the tibionavicular, tibiospring, spring, and tibiocalcaneal fibres. Changes in TNJ abduction and hindfoot eversion were recorded following isolated and sequential ligament sectioning. The primary comparison was the effect of isolated tibiocalcaneal sectioning versus isolated tibionavicular and tibiospring sectioning on TNJ abduction.

Sequential DSL sectioning resulted in significant, stepwise increases in TNJ abduction and hindfoot eversion (p < 0.05). Isolated sectioning of the tibiocalcaneal fibres produced greater TNJ abduction than isolated tibionavicular or tibiospring sectioning. Across protocols, the tibiocalcaneal fibres accounted for approximately 28-40% of total TNJ abduction stability. Hindfoot eversion increased progressively with ligament disruption, reflecting combined tibiotalar and subtalar contributions.

Tibiocalcaneal fibres contribute substantially to talonavicular joint abduction stability despite not directly spanning the joint. These findings support the concept of integrated medial ligament function and provide biomechanical insight to inform future experimental and modelling studies of ankle-hindfoot stability.