Definition

A distal biceps tendon injury can be defined as a complete or partial rupture or avulsion of the distal biceps tendon from its distal insertion on the radial tuberosity. Distal biceps tendon ruptures are typically caused by eccentric muscle contractions. Partial ruptures are rare and usually more painful than complete ruptures as the pain for complete ruptures subsides quickly after the initial injury. Often, distal biceps tendon ruptures can be diagnosed from the deformity that forms in the anterior brachium. Risk factors for biceps tendon avulsions include anabolic steroid use, cigarette smoking, and previous tendon injury.

Anatomy

The biceps tendon inserts onto the radial tuberosity of the radius bone in the forearm, just distal to the elbow crease. The tendon has two distinct insertions: the short head of the biceps attaches distally while the long head attaches proximally. It is important to distinguish the biceps tendon from the neighboring “lacertus fibrosus” on clinical exam, which may be mistaken for an intact tendon in the antecubital fossa. Other contents of the anterior antecubital fossa include (from medial to lateral): median nerve (most medial structure), brachial artery, biceps tendon, and the radial nerve (most lateral structure).

Presentation And Motor Exam

Complete rupture of the distal biceps tendon will typically result in a “reverse Popeye sign” due to retraction of the biceps muscle belly into the mid-aspect of the upper arm. A palpable defect is often appreciated as well as a firm nodule due to the abnormal tendon that has retracted from its normal insertion point on the bone. The biceps muscle is responsible for flexion of the elbow and supination of the forearm. As a result, the strength of these two motions will be affected with biceps tendon avulsion (supination strength is more affected that elbow flexion strength).

Strength deficits following complete biceps tendon avulsion at the elbow:

  • loss of 50% sustained supination strength

  • loss of 40% supination strength

  • loss of 30% flexion strength.

The challenge for the clinician is to distinguish between complete and partial ruptures. The biceps tendon is absent in complete rupture and palpable in partial rupture (otherwise they have a very similar clinical picture).

Differential Diagnosis

  • Cubital bursitis

  • Partial tendon rupture

  • Distal biceps muscle tear

  • Elbow dislocation

  • Radial head fracture

  • Entrapment of lateral antebrachial cutaneous nerve (LABC)

Evaluation And Imaging

X-Rays are usually normal following tendon avulsion unless a piece of bone has been avulsed from the radial tuberosity along with the tendon.

An MRI is often ordered to:

  • confirm the diagnosis

  • differentiate between a complete and partial tear

  • assess the degree of retraction of the tendon

Treatment

The decision to perform surgery for primary tendon repair should be based on a comprehensive review of the risks and benefits of surgery, contrasted with the expectations of conservative management. Non-operative treatment consists of physical therapy and supportive treatment (ice, NSAID), which is sometimes indicated for older, low-demand patients who are willing to sacrifice function. Outcome following non-operative treatment for these injuries will include:

  • will lose 50% sustained supination strength

  • will lose 40% supination strength

  • will lose 30% flexion strength

  • will lose 15% grip strength

Indications for surgical repair of the tendon back down to the tuberosity include:

  • young, healthy patients who do not want to sacrifice function (as specified above).

  • partial tears that do not respond to non-operative management.

Surgical treatment should occur within a few weeks from the date of injury to avoid irreversible retraction of the tendon from its insertion point over time.

Dr. Dold utilizes an anterior, single-incision technique (utilizing an endobutton) for repair of the ruptured tendon. Dr. Dold has published on this topic and the various techniques utilized for surgical repair at Orthobullets.com. More information can be found here.

Research