Objective: To compare the parameters of screw implantation in capitolunate arthrodesis between the 2nd and 3rd metacarpal bones and via the distal dorsal capitate bone approach based on CT images of the normal wrist, and provide reference for the selection of surgical approaches and planning of screw insertion trajectory.
Methods: CT data of 50 patients who met the criteria between February 2022 and April 2022 were selected as the study objects. There were 30 males and 20 females, and the age ranged from 18 to 69 years (mean, 37 years). The normal wrist alignment was conformed in all CT images. All CT data from the unilateral wrist of the patients was imported into Mimics Medical 20.0 software to construct a three-dimensional plane model, in which a virtual 3.5 mm screw was implanted between the 2nd and 3rd metacarpal bones and via the distal dorsal capitate bone approach. The angle between screw and coronal, sagittal, and transverse planes, the total length of the screw, the length of the screw in the lunate bone and the capitate bone were measured. The ratios of the length of the screw in capitate bone to the length of the long axis of the capitate bone, the length of the screw in lunate bone to the length of the long axis of the lunate bone, and the length of screw in lunate bone to the length of the screw in capitate bone were calculated. Assuming that the result of screw implantation between the 2nd and 3rd metacarpal bones was better than that via the distal dorsal capitate bone approach, the difference in length of the screw in the lunate bone between the two approaches was calculated, and the superiority test was performed.
Results: Compared with the distal dorsal capitate bone approach, the total length of the screw increased, the length of the screw in the capitate bone decreased, and the length of the screw in the lunate bone increased, the angle between the screw and coronal plane decreased, the angles between screw and sagittal, transverse planes increased after the screw was implanted between the 2nd and 3rd metacarpal bones. And the ratio of the length of the screw in capitate bone to the length of the long axis of capitate bone decreased, the ratio of the length of the screw in lunate bone to the length of the long axis of lunate bone increased, and the ratio of the length of the screw in lunate bone to the length of the screw in capitate bone also increased. All the differences were significant ( P<0.05). The difference in the length of the screw in the lunate bone between the two approaches was 1.86 mm [95% CI (1.54, 2.18) mm], which was greater than the superiority margin (1.35 mm). The superiority hypothesis was supported.
Conclusion: Compared with the distal dorsal capitate bone approach, the screws implanted between the the 2nd and 3rd metacarpal bones in the capitolunate arthrodesis are longer in lunate bone and more vertical to the articular surface of the capitolunate joint. Theoretically, the capitolunate joint are more firmly fixed.
目的: 基于正常腕关节CT图像，分析头月关节融合术中经第2、3掌骨间及头状骨远端背侧缘入路植入螺钉的参数差异，为临床手术入路选择以及螺钉植入路径规划提供参考。.
方法: 选择2022年2月—4月符合标准的50例患者作为研究对象。男30例，女20例；年龄18～69岁，平均37岁。腕关节力线均正常。将患者单侧腕关节CT数据导入Mimics Medical 20.0软件，构建三维平面模型，分别模拟经第2、3掌骨间及经头状骨远端背侧缘入路植入直径3.5 mm螺钉。测量螺钉与冠状面、矢状面、横断面夹角角度，螺钉位于头状骨、月骨内长度以及螺钉总长度，计算相关指标比值（头状骨内螺钉长度/头状骨长轴长度、月骨内螺钉长度/月骨长轴长度、月骨内螺钉长度/头状骨内螺钉长度）。并假设经第2、3掌骨间入路植入螺钉效果优于经头状骨远端背侧缘入路，计算两种方式月骨内螺钉长度差值，行优效性检验。.
结果: 与经头状骨远端背侧缘入路相比，经第2、3掌骨间入路植入螺钉后，螺钉在头状骨内长度减小、在月骨内长度增加，螺钉总长度亦增加；螺钉与冠状面夹角变小，与矢状面、横断面夹角增大；头状骨内螺钉长度/头状骨长轴长度减小，月骨内螺钉长度/月骨长轴长度、月骨内螺钉长度/头状骨内螺钉长度增加；组间差异均有统计学意义（ P<0.05）。两种方式植入的螺钉在月骨内长度差值为1.86 mm ［95% CI（1.54，2.18）mm］，均大于优效界值（1.35 mm），优效性假设成立。.
结论: 与经头状骨远端背侧缘入路相比，头月关节融合术中经第2、3掌骨间入路植入的螺钉在月骨内更长、与头月关节面更垂直，理论上头月关节固定更牢固。.
Keywords: Wrist; capitate bone; capitolunate arthrodesis; imaging analysis; lunate bone; screw.