[Biomechanical effect of anterior lower tibiofibular ligament rupture on tibiotalar articular surface]

To investigate the changes between pressure of trochlea of talus surface and distribution of area after anterior lower tibiofibular ligament rupture, and provide basis for treating anterior lower tibiofibular ligament rupture.

Six fresh adult ankle joint specimens (4 males and 2 females, ranging age from 25 to 60 years, with an average of 44.6 years) were adopted. The specimens were removed from skin and muscles, remained ankle joint capsule, medial and lateral ligaments and anteroinferior tibiofibular ligament. The ankle joint was fixed with a special fixture in neutral position. Pressure sensitive film (700 N axial load ) was respectively used to measure mean pressure, peak pressure and stress distribution area of the upper articular facet of talar trochlea of the normal ankle joint and the ankle joint with anterioinferior tibiofibular ligament rupture.

The stress distribution areas of the control group and the ruptured group were respectively (367.8 +/- 54.0) mm2 and (386.0 +/- 53.7) mm2; the mean pressures were respectively (1.40 +/- 0.12) MPa and (1.70 +/- 0.35) MPa; the peak pressures were respectively (2.60 +/- 0.33) MPa and (3.20 +/- 0.32) MPa. The experimental results showed that the change in stress distribution area after anterioinferior tibiofibular ligament rupture was not significant (t = 0.021, P = -0.983). When stress distribution changed, the region of stress concentration transferred to poster lateral,and mean pressure (t = 4.140, P = 0.020) and peak pressure (t = 3.169, P = 0.010) increased significantly.

When anterior lower tibiofibular ligament rupture occurs, mean pressure,peak pressure and stress distribution of pressure of trochlea of talus surface is changed, which may cause traumatic arthritis, and surgical treatment is considerably used to restore normal anatomy.