Endoscopic anatomy of distal biceps tendon insertion and bicipitoradial bursa: a cadaveric study

Background: Distal biceps endoscopy has emerged as a minimally invasive alternative to open procedures for distal biceps tendon (DBT) pathology. The purpose of this study was to systematically describe the static and dynamic appearance and variations of the DBT insertional region using a standardized endoscopic technique and dissection in healthy cadaveric elbows. Methods: Endoscopic assessment of the DBT insertional region was performed using a standard proximal parabiceps portal in 20 fresh frozen cadaveric upper extremities. A 6-point endoscopic evaluation of the DBT and bicipitoradial bursa was performed in a static supination position and with dynamic rotation. Anatomic variations in the DBT insertional characteristics, as well as the extent and appearance of the intrabursal space, were documented. Each cadaver was then dissected to correlate endoscopic findings with gross anatomic structures. Results: A bare oval tuberosity area (n = 20) bounded by the supinator and DBT was observed. The DBT inserted ulnar to the bare area (n = 16) and the presence of an intervening wide (n = 1) or narrow (n = 3) tuberosity sulcus were documented. The dorsoradial DBT surface was consistently intrabursal and was differentiated into 2-5 fiber bundles (n = 15). The volar-ulnar DBT surface was always extrabursal and was associated with endoscopically identifiable proximal and distal fat pads. The bicipitoradial bursa formed a bursal sac that was attached to the dorsoradial (n = 13) or volar (n = 7) aspect of the tuberosity and extended proximally along the DBT for 3-5 cm (parabiceps space). A distinct ligament-like band (transverse radioulnar ligament) extended transversely across the proximal radio-ulnar space and appeared to form a sling that provided ulnar support to the DBT during dynamic rotation. The intact DBT surface was robust and could not be breached, even with firm pressure using a probe. Conclusions: The bare tuberosity area, the bursal sac, and the parabiceps space are consistent anatomic landmarks that can be used during DBT endoscopy. An insertional tuberosity sulcus and DBT surface differentiation are normal anatomic variations. The transverse radioulnar ligament provides ulnar support for the DBT during pronation and forms a pulley mechanism for smooth tendon gliding motion. (C) 2021 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved.