CAJ | 학술논문

目的通过几何学模型探讨内固定物尖端与股骨头边缘的安全距离,以避免内固定物穿出股骨头.方法把股骨头作为一个球体处理,正、侧位投影所得为两个平面圆形影像.平面圆形影像所代表的空间结构为两个互相垂直的圆柱体,两者的公共部分即为正、侧位影像所代表的空间区域.分析股骨头的正、侧位投影所得的二维影像与其三维空间结构的几何关系,通过两者立体结构及体积的比较,计算为确保内固定物位于股骨头内所要求的内固定物尖端与股骨头边缘的安全距离.结果股骨头的二维正、侧位影像所构成的空间结构为一个外切于股骨头球体的牟合方盖,其与股骨头球体的体积比为4:π.正、侧位X线影像中内固定物尖端均位于股骨头内的情况下,其实际上穿出股骨头的危险性约为21.5%.为了降低内固定物穿出股骨头的危险性,必须使牟合方盖的体积变小,即内固定物的尖端距股骨头边缘有一定的距离.当牟合方盖小到恰好内切于球体时,内固定物穿出股骨头的危险性降为零.此时通过几何学计算可知X线影像上内固定物尖端与股骨头中心的距离约为股骨头半径的0.71倍.即当X线影像上股骨头直径为5 cm时,内固定物尖端与股骨头边缘的距离约为0.7 cm.结论为确保内固定物位于股骨头内,X线影像上内固定物尖端与股骨头中心的距离应小于股骨头半径的0.71倍.即当正、侧位X线影像上股骨头直径为5 cm时,内固定物尖端与股骨头边缘的安全距离应>0.7 cm.
목적 통과궤하학모형탐토내고정물첨단여고골두변연적안전거리,이피면내고정물천출고골두.방법 파고골두작위일개구체처리,정、측위투영소득위량개평면원형영상.평면원형영상소대표적공간결구위량개호상수직적원주체,량자적공공부분즉위정、측위영상소대표적공간구역.분석고골두적정、측위투영소득적이유영상여기삼유공간결구적궤하관계,통과량자입체결구급체적적비교,계산위학보내고정물위우고골두내소요구적내고정물첨단여고골두변연적안전거리.결과 고골두적이유정、측위영상소구성적공간결구위일개외절우고골두구체적모합방개,기여고골두구체적체적비위4:π.정、측위X선영상중내고정물첨단균위우고골두내적정황하,기실제상천출고골두적위험성약위21.5%.위료강저내고정물천출고골두적위험성,필수사모합방개적체적변소,즉내고정물적첨단거고골두변연유일정적거리.당모합방개소도흡호내절우구체시,내고정물천출고골두적위험성강위령.차시통과궤하학계산가지X선영상상내고정물첨단여고골두중심적거리약위고골두반경적0.71배.즉당X선영상상고골두직경위5 cm시,내고정물첨단여고골두변연적거리약위0.7 cm.결론 위학보내고정물위우고골두내,X선영상상내고정물첨단여고골두중심적거리응소우고골두반경적0.71배.즉당정、측위X선영상상고골두직경위5 cm시,내고정물첨단여고골두변연적안전거리응>0.7 cm.
Objective To determine the geometric safe distance from the tip of screw to the edge of femoral head (tip-to-edge distance, or TED) on radiographic images. Methods Using geometric methods to analyze the position of internal fixation implants on anteroposterior (AP) and lateral X-ray images and to cor-relate them with the three-dimensional structure of the femoral head. To calculate the safe distance from the tip of screw implants to the edge of femoral head (TED) on images to ensure it within the femoral head by comparing both of their structure and volumes. Results The imaginary spatial structure created from the AP and lateral X-ray images, designated as a "Steinmetz Solid" in geometry, had a volume proportional to the femoral head with a ratio of 4:π. The risk of the screw implant penetrating the femoral head when the tip lo-cated inside the shadow on both AP and lateral X-ray images was about 21.5%. To ensure that the screw implant was entirely within the femoral head, this imaginary spatial structure should be internally tangential to the femoral head. The distance from the implant's tip to the center of femoral head was about 0.71 times to the diameter of femoral head on images, which meant the TED was about 0.7 cm when the diameter of femoral head was 5 cm. Conclusion The distance from the screw implant's tip to the center of femoral head should be at most 0.71 times the diameter of femoral head, and the TED should be more than 0.7 cm when the radius of the femoral head is 2.5 cm on images, in order to ensure that the implant is entirely with-in bone and not in the joint space