Abstract: Objective   To clarify the morphological features of the posterior bundle (PB) of the ulnar collateral ligament of the elbow joint, so as to provide reference for anatomy of elbow joint and surgical repairs of ligaments.     Methods    A total of 82 adult elbow joints were dissected and the characteristics of the PB were noted. The length, widths of the origin and insertion of the PB were measured with a vernier caliber. Results    (1)The PB was divided into four types according to the relation with the elbow joint capsule: ① typeⅠ, the anterior and posterior edges were located on the surface of the capsule and could be separated as a single ligament in 61% of cases. There was significant difference in length between male (20.92±2.59) mm and female (17.28±2.07) mm in this type (P=0.000, t=5.531). ② typeⅡ, the anterior edge of PB was fused with elbow joint capsule, while the posterior edge was thickened and free in 16% of cases. ③ type Ⅲ, the posterior edge of PB was fused with elbow joint capsule,  while the anterior edge was thickened and free in 18% of cases. ④ type Ⅳ, the anterior and posterior edges of PB could not be separated from the elbow joint capsule in 5%  of cases. (2) Types Ⅰand Ⅱ were more commonly occurred in male, while types Ⅰand Ⅲ were observed in female frequently. There was significant difference in type composition (c2=8.096,P=0.035).    Conclusions The new classification of the PB was proposed based on the supplement to the anatomy of UCL, which emphasized the relation with the joint  capsule of the elbow TypeⅡ~Ⅳ of PB maybe an important factor causing morphological variation. Gender difference should be considered when treating PB injury, so as to facilitate structural and functional recovery.  

Key words: Ulnar collateral ligament,  ,  , Posterior bundle,  ,  , Variation,  ,  , Applied anatomy