Partial thickness triceps brachii tears selectively involving the superficial layer. MR findings and anatomy review

Clinical History

52-year-old male patient who fell onto the outstretched arm, presented inflammation, pain and limited articular range, associated with a palpable defect in the posterior region of the elbow.

Imaging Findings

Lateral radiograph of the elbow shows a spur at the dorsum of the olecranon process with a small bony avulsion (‘flake sign’) located posterior to the distal humerus.
MRI showed proximal retraction and isolated rupture of the superficial triceps tendon (lateral and long heads), with an intact deep tendon (medial head).

Discussion

Clinical Perspective: Sierra et al mentioned that rupture of the triceps tendon is a rare situation, with only 50 cases reported from 1987 to 2006 [1]. However, Koplas et al in his study referred that the prevalence of triceps tendon injuries was 3.8% (18 patients with partial tears and 10 with complete tears) [2]. Predisposing factors for triceps tendon tear include olecranon bursitis (local steroid injection), hyperparathyroidism and renal failure, weight-lifting (anabolic steroid use), and systemic corticosteroid use [2].
Imaging Perspective: The occurrence of partial-thickness triceps brachii tears selectively involving the superficial layer of the triceps may be explained by the unique anatomy of the distal tendon insertion on the olecranon [3].
The triceps brachii muscle is part of the posterior group of the elbow muscles and is formed by three heads (long, lateral, and medial), hence, its name [4].
The lateral and long heads converge distally to form a fused flattened tendon that inserts into the posterior part of the proximal end of the olecranon (Fig. 3). The medial head originates from the medial aspect of the radial groove of the humerus. The long and lateral heads give rise to a single tendon that inserts onto the olecranon. The superficial fibres continue as the triceps expansion and insert into the posterior crest of the ulna medially and the fascia of the extensor carpi ulnaris laterally (Fig. 3). The medial head remains muscular more distally until close to the insertion where it gives rise to a separate tendon that inserts in part to the olecranon, in part to the flattened fused tendon of the long and lateral heads, and in part to the posterior aspect of the elbow joint capsule (Fig. 3), preventing impingement of the capsule on extension of the elbow [5]. The tendon may have a bipartite appearance on MRI but histological studies have shown that the tendon fuses to form one unit before insertion on to the olecranon [6] (Fig. 3).
Presence of spur at the dorsum of the olecranon process and ectopic calcifications into the tendon can be related to enthesopathy and chronic tendinitis and may alter structural tendon integrity [7].
Outcome: Surgical repair of partial ruptures, however, remains controversial, because good results of conservative treatment are often sufficient and effective in these cases. However, the authors recommend surgical repair in strength workers or sportsmen and in young people [6].

Differential Diagnosis List

Final Diagnosis

Isolated tear of the superficial triceps tendon.

URL:	https://eurorad.org/case/11480
DOI:	10.1594/EURORAD/CASE.11480
ISSN:	1563-4086