The Influences of Bone Cement Vacancy on the Biomechanical Behaviors of the Tibial Component in Cemented Total Knee Arthroplasty

• Main Authors: Jhen-Yun Su, 蘇振畇
• Other Authors: 陳文斌
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/7e5fs4

碩士 === 國立臺北科技大學 === 製造科技研究所 === 103 === Although minimally-invasive procedures used in total knee replacement(TKR) has the benefit of smaller incision, shorter hospital stay and shorter time of recovery, however, the smaller incision can also causelimited space of operation and less visual exposure during surgery. Thus, sometimes cementoverflowmay occur in the posterolateral site of the tibial tray following surgery. Suchcement overflow may become debris in the knee joint and causesevere painand edema. Also the cement overflow may cause bone absorption which may lead to the loosening and failure of the tibial component. Currently,there is still no ideal solution to this problem.Some surgeons placedgelfoam in the posterolateralboundary of the tibial trayto act as a partition for preventing cement overflow. During theimplantation oftibial component, gelfoammay be squeezed into the space between thetibial tray and the osteotomy plane. Later on when gelfoamdecomposes,the space maybecome a gap without cement coverage. Therefore, the cement coverage ratio will be reduced. Currently, the tibial tray stabilityfollowing TKR with gelfoam insertion has not been investigated.In this study,tibiasawbone specimens and commercial knee prostheses were used to test the hypothesis that partial vacancy of cement caused bythemisplace ofgelfoam may reduce the stability oftibial component following cemented TKR. Twenty-four commercial tibial trays were used and assigned into four groups: In group I (n=6), no cementvacancy at the bone-implant interface. Ingroup II (n=6), cement vacancywas created at the lateral sideof the tibial tray. In group III (n=6), with cement vacancy at the posterior site. In group IV (n=6), with cementvacancy at the posterolateral site of the tibial tray. In the in vitro mechanical testing, a static loadsimulatingthree-times body weight of a 70 kg male was applied on the tibial tray. The micro-motions at the anterior, medial and posterior sides of the tibial tray were measured using LVDT (Linear Variable DifferentialTrasformer) sensors.Following the static loading, an eccentric cyclic loading (50000 cycles) at 1 Hz was applied to the tibial tray.Finally, the micromotions of the tibial trayin relative to the tibia for the static loading and after cyclic loading were measured for each test group.The meanvalues oftibial tray mircomotionsfor each group under static loading and after cyclic loading were compared. According to the results, there were no significant differences for the micromotionsbetween thestatic loading and after cyclic loading conditionsand thetibial tray was in varus and posterior tilt with no cement vacancy. The same tendencies were in agreement with theprevious in vitro experiment resultsin literature. So the setting of this study was validated. Based on the resultsfrom the initial and after cyclic loading conditions, reduced cement coverage areas will affect the stability of the tibial tray, but the main factor affecting the behavior of themicromotions is the location of cement vacancy. Lateral cement vacancy caused abduction and posterior tilting of the tibial tray. Posterior cement vacancycausedposterior tilting of the tibial tray. Posterolateral vacancy cause extensive abduction and posterior tilting of the tibial tray. Therefore, gelfoam should be avoided toreside at the posterolateral side of the tibial tray for a better tibial tray stability following cyclic loading. The placement of gelfoam at the posterior side might have less influence on the stability of tibial tray.