目的　观察前臂骨间后神经及其拇示指肌支的解剖学特征。  方法　解剖43具尸体的86侧上肢部桡神经深支及其分支到腕背部，观测骨间后神经的行程与投影及其拇示指肌支起始部位横径、长度和骨性标志线与神经干间夹角关系等参数。  结果　骨间后神经及其各分支均呈扁薄的窄带状神经束，其主干和多数肌支都走行在前臂后面中2/4段浅、深层肌之间，终末支止于腕背侧的梭形膨大部；主干起始处横径为（3.79±0.64）mm，各分支在起始部的平均横径（除指伸肌支约2.0 mm外）均小于1.0 mm；在旋后位，它呈向桡侧开放的弓形线段投影在肱骨外上髁至尺骨茎突连线的尺侧，半旋前位时则投影于该连线上或其桡侧。  结论　前臂后面中2/4段是骨间后神经主干及其大多数拇示指肌支在临床上易被损伤、误伤发生的高风险区域。

Objective　To explore the anatomic features of posterior interosseous nerve and its muscular branches to thumb and index fingers.　Methods　86 upper limb specimens from 43 fixed cadavers were used in this study. Deep branches of radial nerve were dissected, for following the courses of  posterior interosseous nerve. As well, the origin, diameter, and other anatomic parameters of its muscular branches to thumb and index fingers were measured and analyzed.　Results　Posterior interosseous nerve and its branches presented as flat and thin nerve bundles. Its main trunk and muscular branches passed between intermuscular space at posterior and middle 2/4 part of forearm. Fusiform terminal fiber enlargement appeared at the dorsal side of the wrist. The diameter of the origin of the main trunk was about（3.79±0.64）mm，except for branches to extensor digitoium with the diameter of 2.0mm, the mean diameter of other branches was less than 1.0mm. The projection line of posterior interosseous nerve extended ulnarly or radially from radial condyle of humerus to ulnar malleolus, at the supination or semipronation positions, respectively.　Conclusions　Posterior interosseous nerve and its muscular branches are easy to be damaged during its course at the middle and posterior 2/4 segment of forearm.