What is the likely diagnosis and recommended management for a patient who fell onto a desk, has localized tenderness over the left biceps brachii, intact elbow active and passive range of motion, and a negative hook test (no tenderness)?

Likely Diagnosis: Partial Distal Biceps Tendon Tear

A negative hook test with localized biceps tenderness after trauma strongly suggests a partial distal biceps tendon tear rather than a complete rupture, and this patient requires MRI without contrast for definitive diagnosis and surgical planning.

Clinical Reasoning

The hook test is highly specific for complete distal biceps tendon ruptures—when negative (no palpable tendon cord), it effectively rules out complete tears. However, your patient has:

• Localized tenderness over the biceps brachii
• Intact active and passive elbow range of motion
• Negative hook test (tendon still palpable)

This clinical picture is classic for a partial tear of the distal biceps tendon 1, 2. The preserved tendon continuity explains the negative hook test, while the trauma mechanism and localized tenderness indicate underlying structural damage.

Diagnostic Approach

Immediate Next Step: Advanced Imaging

Order MRI of the elbow without IV contrast 3. This is the gold standard for:

• Distinguishing partial from complete tears
• Quantifying tear extent (critical for treatment decisions)
• Detecting associated injuries

Key imaging considerations:

• Standard MRI sequences have 76% sensitivity and 50% specificity for biceps tendon tears 3
• Consider adding FABS (flexion-abduction-supination) view for challenging cases where you need to differentiate high-grade partial from complete tears 3
• Ultrasound is not recommended as the primary modality—it has only 62.5% sensitivity and 20% specificity for biceps tears, significantly inferior to MRI 3

Physical Examination Refinement

Before imaging, perform the TILT sign test 2:

• Flex elbow to 90°
• Firmly palpate the dorsal forearm over the radial tuberosity
• Passively pronate and supinate the forearm
• Positive test: Tenderness over the radial/lateral aspect of tuberosity only in full pronation, not supination
• This test has 100% sensitivity for partial distal biceps tears 2

Management Algorithm

If Tear <50% on MRI:

• Conservative management is acceptable 1
• Immobilization initially, then progressive rehabilitation
• Close follow-up for symptom progression
• Consider surgical debridement if persistent symptoms

If Tear ≥50% on MRI:

Surgical repair is strongly recommended 1, 4. The rationale:

• Partial tears >50% behave functionally like complete tears
• Nonoperative treatment results in persistent strength deficits in flexion and supination 4, 5
• Surgical technique: Divide remaining tendon and repair entire unit anatomically 1

Surgical approach options (both yield similar outcomes) 5:

• Single-incision technique: Higher nerve injury risk
• Double-incision technique: Higher heterotopic ossification risk
• Choice depends on surgeon experience

Fixation methods 5:

• Cortical buttons have superior biomechanical properties
• Suture anchors, interference screws, or transosseous repair are alternatives
• All show satisfactory clinical outcomes

Critical Pitfalls to Avoid

1. Don't assume negative hook test = no injury: Partial tears present with palpable tendon but significant pathology 1, 2

2. Don't rely on ultrasound alone: Its poor sensitivity (62.5%) will miss many tears 3

3. Don't delay imaging: Chronic tears develop tendon retraction and scarring, making reconstruction significantly more complex and requiring grafts 4, 6

4. Don't underestimate partial tears: Even <50% tears can progress and cause persistent functional deficits if not monitored closely 1

5. Age and activity matter: Young, active patients benefit most from surgical intervention; older, sedentary patients may tolerate conservative management 4, 6

Expected Outcomes

With appropriate surgical management for significant tears:

• High subjective satisfaction rates 7
• Slight residual weakness in flexion/supination is common 7
• Range of motion typically preserved 7
• Major complications: posterior interosseous nerve palsy and heterotopic ossification 7, 5