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박경용(K.Y. Park),박은영(E.Y. Park),김민선(M.S. Kim),황정구(J.G. Hwang),손웅희(W.H. Shon),김건하(K.H. Kim),박진환(J.H. Park) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
Under the various conditions and purposes of excavator, fracture and fatigue happens at rotary grippers part in which damage is occurring frequently. This study is for computational analysis and design optimization for ring-geared grippers of 21-ton excavator rotary in order to improve the life. Through this study, we tried to evaluate the stress concentration leads to fracture and find out the optimal condition of structure. We conducted study on the design of the ring gear for improvement and suggested the design change to prevent stress concentration.
척추경나사못을 이용한 유합술과 동반 시술된 극돌기간 삽입기구의 생체역학적 연구
김영현,박은영,이성재,Kim, Y.H.,Park, E.Y.,Lee, S.J. 대한의용생체공학회 2015 의공학회지 Vol.36 No.6
Recently, during the multi-level fusion with pedicle screws, interspinous spacer are sometimes substituted for the most superior level of the fusion in an attempt to reduce the number of fusion level and likelihood of degeneration process at the adjacent level. In this study, a finite element (FE) study was performed to assess biomechanical efficacies of the interspinous spacer combined with posterior lumbar fusion with a previously-validated 3-dimensional FE model of the intact lumbar spine (L1-S1). The post-operative models were made by modifying the intact model to simulate the implantation of interspinous spacer and pedicle screws at the L3-4 and L4-5. Four different configurations of the post-op model were considered: (1) a normal spinal model; (2) Type 1, one-level fusion using posterior pedicle screws at the L4-5; (3) Type 2, two-level (L3-5) fusion; (4) Type 3, Type 1 plus Coflex$^{TM}$ at the L3-4. hybrid protocol (intact: 10 Nm) with a compressive follower load of 400N were used to flex, extend, axially rotate and laterally bend the FE model. As compared to the intact model, Type 2 showed the greatest increase in Range of motion (ROM) at the adjacent level (L2-3), followed Type 3, and Type 1 depending on the loading type. At L3-4, ROM of Type 2 was reduced by 34~56% regardless of loading mode, as compared to decrease of 55% in Type 3 only in extension. In case of normal bone strength model (Type 3_Normal), PVMS at the process and the pedicle remained less than 20% of their yield strengths regardless of loading, except in extension (about 35%). However, for the osteoporotic model (Type 3_Osteoporotic), it reached up to 56% in extension indicating increased susceptibility to fracture. This study suggested that substitution of the superior level fusion with the interspinous spacer in multi-level fusion may be able to offer similar biomechanical outcome and stability while reducing likelihood of adjacent level degeneration.
Spring rod를 사용한 척추경 나사못과 동반 시술된 Flexible cage의 생체역학적 효과
김영현,박은영,김원현,황성필,박경우,이성재,Kim, Y.H.,Park, E.Y.,Kim, W.H.,Hwang, S.P.,Park, K.W.,Lee, Sung-Jae 대한의용생체공학회 2017 의공학회지 Vol.38 No.1
Recently, flexible cages have been introduced in an attempt to absorb and reduce the abnormal load transfer along the anterior parts of the spine. They are designed to be used with the pedicle screw systems to allow some mobility at the index level while containing ROM at the adjacent level. In this study, a finite element (FE) study was performed to assess biomechanical efficacies of the flexible cage when combined with pedicle screws with flexible rods. The post-operated models were constructed by modifying the L4-5 of a previously-validated 3-D FE model of the intact lumbar spine (L2-S1): (1) Type 1, flexible cage only; (2) Type 2, pedicle screws with flexible rods; (3) Type 3, interbody fusion cage plus pedicle screws with rigid rods; (4) Type 4, interbody fusion cage plus Type 2; (5) Type 5, Type 1 plus Type 2. Flexion/extension of 10 Nm with a compressive follower load of 400N was applied. As compared to the Type 3 (62~65%) and Type 4 (59~62%), Type 5 (53~55%) was able to limit the motion at the operated level effectively, despite moderate reduction at the adjacent level. It was also able to shift the load back to the anterior portions of the spine thus relieving excessively high posterior load transfer and to reduce stress on the endplate by absorbing the load with its flexible shape design features. The likelihood of component failure of flexble cage remained less than 30% regardless of loading conditions when combined with pedicle screws with flexible rods. Our study demonstrated that flexible cages when combined with posterior dynamic system may help reduce subsidence of cage and degeneration process at the adjacent levels while effectively providing stability at the operated level.