BIOMECHANICAL PROPERTIES OF HUMAN CADAVERIC ANKLE-SUBTALAR JOINTS IN QUASI-STATIC LOADING

The biomechanical properties of human ankle-subtalar joints have been determined in a quasi-static loading condition. The moving center of r otation was determined and approximated by a fixed point. The moment-a ngle characteristics of the ankle-subtalar joints about the fixed cent er of rotation have been measured under four basic movements: dorsifle xion, plantarflexion, inversion, and eversion. The method linearly inc reases rotation of the calcaneus until failure, and measures the momen ts, forces, and linear and rotational displacements. Failure was ident ified as the initial drop of moment on plot showing the moment represe nting gross injury or microfilament damage. In this study, 32 human an kle-subtalar joints have been rested to failure. The center of rotatio n of the ankle-subtalar joints was determined for a pure dorsiflexion (9 specimens), plantarflexion (7 specimens), inversion (8 specimens), and eversion (8 specimens). Failure in the joints occurred at an avera ge moment of -33.1 +/- 16.5 Nm in dorsiflexion, 40.1 +/- 9.2 Nn in pla ntarflexion, -34.1 +/- 14.5 Nm in inversion, and 48.1 +/- 12.2 Nn in e version. The failure angle was also determined in all four motions. Fa ilure was best predicted by an angle of -44.0 +/- 10.9 deg in dorsifle xion, 71.6 +/- 5.7 deg in plantarflexion, -34.3 +/- 7.5 deg in inversi on, and 32.4 +/- 7.3 deg in eversion. Injury was identified in every p reparation tested in inversion and eversion, while it resulted in Jive of the nine preparations in dorsiflexion, and in three of the seven i n plantarflexion. Injury occurred at -47.0 +/- 5.3 deg and -36.2 +/- 1 4.8 Nm in dorsiflexion, and at 68.7 +/- 5.9 deg and 36.7 +/- 2.5 Nm in plantarflexion. The results obtained in this study, provide basic inf ormation of the ankle-subtalar joint kinematics, biomechanics, and inj ury. The data will be used to form a basis for corridors of the ankle- subtalar joint responses.