目的　为解决胸小肌移植重建拇对掌功能术后出现拇指指骨间关节屈曲畸形提供解剖学依据并寻找解决办法。  方法　在15具尸体手标本上，使拇指处于对掌位时，测量拇指指骨间关节在拇短展肌未切断及切断两种情况下的自然屈曲角度；同时，通过外力作用使拇指指骨间关节分别屈曲处于45°及60°时，分析拇短展肌对拇指指骨间关节屈伸功能的影响。  结果　拇指处于对掌位时，拇短展肌在未切断及切断两种情况下，拇指指骨间关节自然屈曲角度分别为（13.30±2.13）°及（24.03±1.25）°；同时，使拇指指骨间关节屈曲处于45°时，所用外力分别约（0.50±0.08）N及（0.22±0.07）N，而使拇指指骨间关节屈曲处于60°时，所用外力分别约（1.48±0.09）N及（1.15±0.04）N。  结论　拇短展肌对拇指指骨间关节主要起背伸作用，因此胸小肌移植重建拇对掌功能时，应同时重建拇短展肌功能，才有可能纠正在拇对掌功能重建术后出现的拇指指骨间关节屈曲畸形。

Objective    This study aimed to provide anatomical evidence to solve the flexion deformity of the interphalangeal joint of the thumb caused by the surgical procedure of reconstruction of thumb opposition function with pectoralis minor muscle.　Methods　On 15 cadaveric hand specimens with the thumb in the opposition position, we measured the natural flexion angle of the interphalangeal joint of the thumb before and after transection of abductor pollicis brevis; Meanwhile, the interphalangeal joint was rendered into flexion angle of 45°and 60°by external force to analyze the effect of abductor pollicis brevis on the flexion and extension function of the interphalangeal joint of the thumb.　Results　When the thumb was in the opposition position, the natural flexion angles of the interphalangeal joint of the thumb was （13.30±2.13）°and （24.03±1.25）°before and after transection of abductor pollicis brevis; rendering of the interphalangeal joint of the thumb at the flexion angle of 45°required application of external force by（0.50±0.08）N and（0.22±0.07）N, respectively, while rendering of the interphalangeal joint at 60°required application of external force by（1.48±0.09）N and（1.15±0.04）N, respectively.　Conclusions　The main function of abductor pollicis brevis is to dorsally extend the interphalangeal joint of the thumb. Consequently, the function of abductor pollicis brevis on the thumb should be restored when reconstruction of thumb opposition with functional pectoralis minor muscle flap is performed，so that we can rectify the postoperative the flexion deformity of the interphalangeal joint of the thumb.