Courtesy- Dr Nabil

 

 

Overview

• Distal biceps tendon rupture is an injury of the distal insertion of the biceps tendon at the radial tuberosity.
• It usually results from a sudden eccentric load applied to a flexed elbow.
• The Hook Test is one of the most reliable clinical tests for diagnosing a complete distal biceps tendon rupture.

Anatomy

• The distal biceps tendon inserts onto the radial tuberosity.
• Functions of the biceps:
? Forearm supination
? Elbow flexion

Mechanism of Injury

• Sudden eccentric force on the elbow while flexed to approximately 90 degrees.
• Typically occurs when an unexpected extension force is applied to a contracting biceps muscle.

Epidemiology

• Most common in middle aged men.
• Usually affects the dominant upper limb.
• Typically results from a single traumatic event.

Clinical Features

Symptoms

• Sudden painful pop in the front of the elbow.
• Immediate anterior elbow pain.
• Weakness of forearm supination.
• Weakness of elbow flexion.

Clinical Signs

• Bruising around the elbow.
• Palpable defect at the distal biceps tendon.
• Proximal retraction of the biceps muscle belly producing the “reverse Popeye sign.”

Functional Deficits if Untreated

Failure to diagnose and repair a complete rupture may result in:

• 40 to 50 percent loss of forearm supination strength.
• Approximately 30 percent loss of elbow flexion strength.

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Hook Test

Purpose

To diagnose complete rupture of the distal biceps tendon.

Patient Position

• Elbow flexed to 90 degrees.
• Forearm fully supinated.

Technique

• Examiner attempts to hook the lateral edge of the distal biceps tendon using the index finger.
• The finger is inserted beneath the tendon from the lateral side.

Interpretation

Normal or Partial Tear

• Tendon can be hooked with the examiner’s finger.
• Test is negative.

Complete Tear

• Tendon cannot be hooked.
• Test is positive for complete distal biceps tendon rupture.

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Causes of False Positive Hook Test

• Partial distal biceps tendon tear.
• Intact lacertus fibrosus masking the injury.
• Mistaking the brachialis tendon for the distal biceps tendon.

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Biceps Squeeze Test

Purpose

Alternative clinical test for distal biceps tendon rupture.

Patient Position

• Elbow flexed to approximately 80 degrees.
• Forearm held in slight pronation.

Technique

• Examiner squeezes the biceps muscle belly using one or both hands.

Interpretation

Intact Tendon

• Forearm supinates when the muscle is squeezed.

Complete Rupture

• No forearm supination occurs.

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Partial Versus Complete Tears

Complete Tear

• Positive Hook Test.
• Palpable tendon defect.
• Reverse Popeye deformity may be present.

Partial Tear

• Pain over the anterior elbow.
• Hook Test is often normal.
• Frequently missed or misdiagnosed.
• Clinical presentation may resemble a complete tear.

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Role of MRI

MRI is not required in every patient but is useful when:

• Partial tendon rupture is suspected.
• Clinical examination is inconclusive.
• Surgical planning is required.

MRI can determine:

• Presence of tendon tear.
• Partial versus complete rupture.
• Degree of tendon retraction.

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Key Take Home Messages

• Distal biceps tendon rupture usually occurs after a sudden eccentric load on a flexed elbow.
• The Hook Test is highly useful for diagnosing complete distal biceps tendon rupture.
• A normal Hook Test does not exclude a partial tear.
• The Biceps Squeeze Test is a useful additional clinical test.
• MRI is most valuable for diagnosing partial tears and assessing tendon retraction.
• Early diagnosis and repair help preserve forearm supination and elbow flexion strength.

Exam Pearls

• Distal biceps tendon inserts on the radial tuberosity.
• Middle aged men are most commonly affected.
• Reverse Popeye sign suggests distal biceps tendon rupture.
• Complete tears produce a positive Hook Test.
• Partial tears often have a normal Hook Test and require MRI for confirmation.
• Untreated complete rupture results in significant loss of forearm supination strength.