Definition, classification and morphometry of entrance of the bicipital groove and its associations with lesions of adjacent structures

Background The definition of the entrance of the bicipital groove (EBG) is still unclear, and the relationships between the EBG and lesions of the long head of the biceps brachii tendon (LBT) and biceps pulley complex (BPC) have long been controversial. The purpose of this anatomic and imaging study was to define the EBG and to examine morphological parameters, classifications, and their relationships with lesions of the LBT and BPC. Methods One hundred thirteen unpaired intact dry humeri, 34 cadaveric shoulder specimens and 278 shoulder images were collected, measured, and classified based on morphological characteristics. Soft tissue and bony landmarks of the EBG were classified into different types. The relationships between the types and lesions of the LBT and BPC were analyzed through an anatomic and imaging study. Results Type II, type A and type i of the EBG and type b of the adjacent articular surface accounted for most of the dry humeri, cadavers, and images. Based on the EBG classification in the superoinferior image view, all of the subluxations and dislocations were classified as type B (61/120, 50.83%; χ2 = 16.55, P < 0.001), and most LBT and BPC lesions were type B (65/117, 55.56%; χ2 = 26.05, P < 0.001). LBTs were injured in (χ2=, P < 0.001) 83.56% of type B, 100% of type C, and 95.83% of type iii EBGs (χ2 = 135.69, 31.89, all P < 0.001). Similarly, BPCs were injured in 89.04% of type B and 93.10% of type C EBGs (χ2 = 153.14, P < 0.001), while BPCs were injured in 95.8% of type iii EBGs (χ2 = 33.79, P < 0.001). Conclusions The EBG is an anatomical concept worthy of clinical attention. Anatomical variations in the EBG correlated with lesions of the LBT and BPC. LBT and BPC lesions correlated with type B and C EBGs by imaging analysis.