The distal biceps tendon. Two potential mechanisms involved in its rupture: arterial supply and mechanical impingement.

The purpose of this anatomic study was to evaluate potential causes of rupture of the distal biceps tendon, to assess the dynamic relationship of the proximal radioulnar joint during pronation and supination, and to identify potential sites of impingement of the distal biceps tendon. For the anatomic study specimens were evaluated by light microscopy, multiplanar gross dissections, and Spalteholz vascular injection. For the radiographic study computed tomography was used to assess dynamic changes in the radioulnar space in pronation, neutral position, and supination. Three vascular zones were identified in the distal biceps tendon. Vascular contributions were consistently noted from the brachial artery proximally and from the posterior recurrent artery distally. A hypovascular zone averaging 2.14 cm was evident between the proximal and distal zones. On sectioning through the proximal radioulnar joint 85% of the space was occupied by the distal tendon in full pronation. In addition, computed tomography imaging revealed a 50% reduction in the radioulnar joint at the radial tuberosity from full supination to full pronation. Mechanical impingement on the biceps tendon during forearm rotation and hypovascularity within sections of the tendon may contribute to attritional ruptures of the distal biceps tendon.