ABSTRACT
BACKGROUND: Osteotomy of the fibula is a common orthopedic procedure performed for various indications, including harvesting fibula for grafting purposes. The effect of fibular osteotomy and need for tibiofibular syndesmotic fixation fusion at different levels on tibiotalar joint is matter of debate. We performed a biomechanical analysis of the impact of fibular osteotomies at different levels and whether the fixation of distal tibiofibular joint mitigates instability caused by the osteotomy. MATERIALS AND METHODS: Six lower limb specimens from fresh adult cadavers were used to prepare leg-foot models. The specimens were assigned to six status according to the level of osteotomy and whether fixation of distal tibiofibular joint was performed or not. Each specimen was then loaded axially to 700 N by the material testing machine, and the tibiotalar joint contact area and peak pressure were measured using an electronic pressure sensor. RESULTS: The contact area and the pressure of tibiotalar joint showed significant changes when compared to the normal specimen. All osteotomy specimens had a decreased tibiotalar contact area and an increased peak pressure. This positively correlated with proximity of level of osteotomy to the lateral malleolus. CONCLUSIONS: Through this study, we found that fibular osteotomy had an adverse effect in terms of decreasing the contact surface of tibiotalar joint that led to increased peak pressure in the joint. However, bone fusion and screw fixation of the distal tibiofibular joint reduced these adverse effects.
ABSTRACT
OBJECTIVE: To investigate the stability and three-dimensional movements of the atlantoaxial joint after artificial atlanto-odontoid joint (AAOJ) arthroplasty. METHOD: Ten sets of AAOJ implanted in bony specimens from 10 adults were used to test the pull-out strength of the atlas-axis components with a MTS858 Mini Bionix machine. Another twelve human cadaveric specimens including C(0)-C(4) were used to evaluate the three-dimensional movements of C(1)-C(2) under five different conditions in sequence, that is, the complete specimen, anterior decompression, posterior transarticular screws fixation, AAOJ arthroplasty and fatigue test. RESULT: There were significant differences between atlas and axis components in the maximum pull-out strength and trajectory length, however the yield length was not significantly different. The maximum pull-out strength of the atlas and axis was positively correlated with trajectory length (r(1)= 0.880, P < 0.05) and yield length (r(2)= 0.606, P < 0.05), respectively. After AAOJ arthroplasty, the range of movement (ROM) with respect to rotation and the neutral zone of the atlantoaxial joint were close to normal (P > 0.05), but the ROM in flexion-extension and lateral bending was significantly smaller compared with the specimens which underwent anterior decompression (P < 0.05). No abrasion and abnormal mobilization were observed after 2000 cycles of flexion, extension, lateral bending and axial rotation in the fatigue test. CONCLUSIONS: The self-designed AAOJ has excellent biomechanical performance, and AAOJ arthroplasty can restore excellent instant stability and preserve the movement of the atlantoaxial joint.
