The effects of the ankle joint prosthesis over the load distribution on the foot with different angles

Abstract

In this study, biomechanical stability on normal and prosthetic ankle joint were evaluated with different position of the ankle joint. The biomechanical tests were performed by using the axial compression testing machine (AG-I 10 kN, Shimadzu, Japan). The video extensometer markers were placed on distal tibia and talus lateral and medial side. The displacements between articular surfaces were measured with two non-contact CCD camera extensometers (Non-contact Video Extensometer DVE-101/201, Shimadzu, Japan). The axial compression was applied to all amputee legs with the loading speed of 5 mm/min (max. 800 N). Biomechanical test, axial compression, was performed on eight amputee legs within four positions (neutral 0, 15 dorsoflexion, 15 and 30 plantar flexion position), same study repeated after replacing with ankle joint prosthesis. Surgical technique was performed as anterior midjoint incision and the soft tissue discussion in ankle joint, then osteotomy, bone resection and replacement of prosthesis both side of ankle joint. Ankle stability was evaluated with measured displacements on the medial side and the lateral side of ankle, against the axial compression forces for all position. When the instability of ankle joint was compared, prosthesis group demonstrated higher than non-prosthesis group. In non-prosthesis group, plain foot position showed more stable values (724.28 N) but 30° ankle joint plantar flexion showed lowest instability (490.82 N). 15° plantar flexion (616.02 N) and 15° dorsolflexion's instabilities exhibited familiar values (582.54 N). In prosthesis group, 15° plantar flexion showed highest instability (602.38 N). 15° dorsoflexion showed lowest instability (407.76 N). There were no significant differences between medial and lateral side both prosthesis and non-prosthesis group.