X线投射角度对踝关节影像学评估的影响

Radiologic evaluation of ankle from different projective anglesRadiologic angles

背景:临床手术中通常用X线来确认踝关节骨折治疗时的解剖复位。但由于踝关节的各参数存在个体差异,因此,摄片时足的旋转角度无法准确控制。目前,对于投射角度对踝关节评估的研究较少。目的:本研究通过不同旋转角度对踝关节进行透视,评估相关参数对下胫腓联合及三角韧带损伤诊断的可靠性。方法:取8具新鲜下肢尸体标本,分别在正常情况以及建立腓骨短缩和(或)三角韧带损伤模型后,"C"型臂X线机以5°为间隔,从-30°至30°逐一测量内踝间隙、胫距上间隙、胫腓间隙及胫腓重叠的距离。结果:正常情况下,内踝间隙平均为(2.58±0.59)mm,胫距上间隙为(2.89±0.56)mm,胫腓间隙为(3.03±0.72)mm,胫腓重叠为(4.25±3.14)mm。建立腓骨短缩和(或)三角韧带损伤模型后,内踝间隙及胫腓间隙变大,而胫距上间隙及胫腓重叠变小。所有参数值均随X线投射角度的改变而发生相应变化。结论:胫腓间隙受透照角度的影响较小,是判断下胫腓联合损伤较为可靠的影像学参数。内踝间隙始终小于胫距上间隙,一旦内踝间隙超过胫距上间隙,则应怀疑三角韧带损伤,或存在外踝短缩畸形的可能。胫腓重叠不会出现负值,如果出现负值,意味着下胫腓联合存在损伤。

Background：X-ray is used to confirm intraoperative anatomic reduction of ankle fractures. However, because of individual differences in ankle-related parameters, the rotation angle of foot can not be accurately controlled. It makes radiologic as-sessment difficult, and few studies have been reported. Objective： To measure radiologic parameters of the ankle in different projective angles and to evaluate the reliability of these parameters in the diagnosis of distal tibiofibular syndesmosis and deltoid ligament disruption. Methods：Eight fresh lower limb specimens were collected in the study. The models of fibula shortening and deltoid liga-ment injury were constructed. The radiologic parameters, including medial clear space, superior clear space, tibiofibular clear space and tibiofibular overlap were measured in the normal specimen and the models of fibula shortening and deltoid ligament injury by＆quot;C＆quot;arm X-ray machine from-30＆#176; to 30＆#176; with an interval of 5＆#176;. Results：The average medial clear space, superior clear space, tibiofibular clear space and tibiofibular overlap were （2.58 ± 0.59） mm, （2.89±0.56） mm, （3.03±0.72） mm, and （4.25±3.14） mm, respectively, in the normal specimens. In shortened fibu-la and （or） deltoid ligament injury models, the medial clear space and tibiofibular clear space increased, while the superior clear space and tibiofibular overlap decreased. The values of all parameters changed with different projective angles of X-ray. Conclusions：There are few changes of tibiofibular clear space from different projective angles. So it is a reliable imaging parameters to judge distal tibiofibular syndesmosis. If medial clear space is bigger than superior clear space, the deltoid liga-ment may be disrupted or the length of fibula may be lost. The negative value of tibiofibular overlap means inferior tibiofib-ular joint injury.