Abstract
BackgroundVarus malalignment of the tibia could alter ankle biomechanics, and might lead to degenerative changes of the ankle joint. However, previous studies failed to report the detailed changes of ankle biomechanics in varus malalignment of the tibia. The aim of this biomechanical study was to evaluate how the ankle joint pressure would change in response to the incremental increases in varus malalignment of the tibia.MethodsEight fresh-frozen human cadaver legs were tested in this study. Varus malalignment of the tibia and a total of 600 N compressive force was simulated using a custom made fixture. Intra-articular sensors (TeckScan) were inserted in the ankle joint to collect the ankle joint pressure data. The testing sequence was 0°, 2°,4°,6°,8°,10°,12°,14°,16°,18°,20° of tibial varus.ResultsAs the tibial varus progressed, the center of force (COF) shifted laterally both for the medial and lateral aspect of the ankle joint. For the medial aspect of the ankle joint, the lateral shift reached its maximum at 8° [2.76 (1.62) mm, p = 0.002] of tibial varus, while for the lateral aspect of the ankle joint, the lateral shift reached its maximum at 12° [2.11 (1.19) mm, p = 0.002] of tibial varus. Thereafter, the COF shifted medially as the tibial varus progressed. For the lateral aspect of the ankle joint, The Pmean increased from 2103.8 (625.1) kPa at 0° to 2295.3 (589.7) kPa at 8° of tibial varus (p = 0.047), significant difference was found between the Pmean at 0° and 8° (p = 0.047) of tibial varus. Then as the tibial varus progressed, the Pmean decreased to 1748.9 (467.2) kPa at 20° of tibial varus (p = 0.002). The lateral joint pressure ratio also increased from 0.481 (0.125) at 0° to 0.548 (0.108) at 10° of tibial varus (p = 0.002), then decreased to 0.517 (0.101) at 20° of tibial varus (p = 0.002) .ConclusionsFor mild tibial varus deformities, there was a lateral shift of COF and lateral stress concentration within the ankle joint. However, as the tibial varus progressed, the COF shifted medially and the lateral stress concentration decreased.
Highlights
Varus malalignment of the tibia could alter ankle biomechanics, and might lead to degenerative changes of the ankle joint
The center of force (COF) shift As the tibial varus progressed from 0° to 20° of tibial varus, the COF shifted laterally both for the medial and lateral aspect of the ankle joint initially, the COF converted to shift medially as the tibial varus progressed to 20°
The COF shifted medially as the tibial varus progressed, the lateral shift of the medial aspect COF was − 1.46 (1.08) mm at 20° of tibial varus, significant difference was found between 8° and 20° of tibial varus, p = 0.001 (Fig. 3)
Summary
Varus malalignment of the tibia could alter ankle biomechanics, and might lead to degenerative changes of the ankle joint. Previous studies failed to report the detailed changes of ankle biomechanics in varus malalignment of the tibia. The aim of this biomechanical study was to evaluate how the ankle joint pressure would change in response to the incremental increases in varus malalignment of the tibia. It is believed that the varus or valgus deformity of the lower extremity is highly associated with osteoarthritis, especially the knee joint [1,2,3,4]. The PreScale TM pressuresensitive film was utilized for the measurement of contact area and pressure, and 0°, 5°, 10°, 15° of deformities was simulated They failed to report the detailed ankle joint pressure change in response to the incremental increases in varus malalignment of the tibia
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