A comprehensive review of the normal, abnormal, and post-operative MRI appearance of the distal biceps brachii
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REVIEW ARTICLE
A comprehensive review of the normal, abnormal, and post-operative MRI appearance of the distal biceps brachii My-Linh Nguyen 1 & Jeffrey Rosenthal 2 & Spero Karas 3 & Michael Gottschalk 3 & Charles Daly 3 & Eric Wagner 3 & Adam Singer 1 Received: 9 April 2020 / Revised: 27 May 2020 / Accepted: 2 June 2020 # ISS 2020
Abstract The biceps brachii myotendinous unit is a common source of shoulder, arm, and elbow pain. Its complex anatomy can present a challenge when interpreting MR images. We discuss the clinical and imaging presentations of injury related to the proximal biceps brachii separately in another manuscript. The purpose of this manuscript is to review the distal biceps anatomy along with pathology and post-operative appearance as seen on MRI. Keywords Biceps . Tendon . Long head . Short head . MRI . Elbow . Rupture
Normal anatomy, function, and innervation of the distal biceps The biceps brachii is made up of two distinct muscle bellies, the long head and short head, which originate from the scapular supraglenoid tubercle and anterolateral coracoid process, respectively, and insert on the radial tuberosity. The mediolateral orientation of the distal tendons follows the orientation at their origins; the short head originates medially from the coracoid process and inserts medial to the long head while the long head originates laterally from the glenoid and inserts lateral to the short head (Figs. 1 and 2). The proximal-to-distal orientation of the tendon insertions is such that the short head inserts distal to the long head (Fig. 1). The long and short head muscle bellies course together and their tendinous insertions often appear as a single unit on imaging (Fig. 3). However, the long and short heads can
* Adam Singer [email protected] 1
Department of Radiology and Imaging Sciences Section of Musculoskeletal Imaging, Emory University Hospital, 59 Executive Park South, 4th Floor Suite 4009, Atlanta, GA 30329, USA
2
Emory University School of Medicine, Atlanta, GA, USA
3
Department of Orthopaedics, Emory University Hospital, Atlanta, GA, USA
remain independent and sometimes maintain separate, bifurcate insertions on the proximal radius (Fig. 4), as a normal variant [1, 2]. A study of 17 cadaveric dissections reported that the tendons are separable along their course in approximately 40% of cases [2]. The bicipital aponeurosis, otherwise known as the lacertus fibrosus, is an extension of the brachial fascia that arises from the distal long and short head tendons and fans out medially over the brachial artery, brachial vein, and median nerve and blends with the pronator teres fascia (Fig. 1). Another important structure in the region of the distal biceps brachii is the bicipitoradial bursa. This bursa, not normally seen on imaging unless distended by fluid or synovial tissue, is located between the biceps tendon and radial tuberosity. It surrounds the biceps tendon in forearm supination and is compressed between the tendon and radius in pronation [3]. The biceps brachii allow for su
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