What is the diagnosis and treatment for a patient with distal swelling in the arm, bruising, and ability to hook?

Distal Biceps Tendon Rupture

This presentation is most consistent with a distal biceps tendon rupture, and the patient requires urgent orthopedic surgical referral for optimal functional outcomes.

Clinical Diagnosis

The ability to "hook" refers to the hook test, which assesses distal biceps tendon integrity:

• Positive hook test (ability to hook the index finger under the biceps tendon lateral to the bicipital aponeurosis with elbow flexed at 90 degrees) indicates an intact distal biceps tendon 1, 2
• Negative hook test (inability to hook) suggests complete rupture
• The presence of distal arm swelling and bruising with maintained hooking ability suggests a partial tear or associated soft tissue injury 1, 2

Key Physical Examination Findings to Assess

• Ecchymosis pattern: Bruising tracking distally into the antecubital fossa is characteristic of biceps tendon pathology 3, 4
• Palpable defect: Feel for a gap in the distal biceps tendon with the elbow flexed 1, 2
• Popeye deformity: Retracted biceps muscle belly creating proximal bulge (more common with proximal biceps ruptures) 1
• Weakness in supination: Distal biceps is the primary supinator; test resisted supination strength compared to contralateral side 2
• Pain with resisted elbow flexion: Indicates partial tear if hook test positive 1, 2

Immediate Management Algorithm

If Hook Test is Positive (Tendon Intact):

• Immobilize in sling with elbow at 90 degrees flexion 1, 2
• Ice application immediately to control inflammation and swelling 3
• Active finger motion exercises should begin immediately to prevent hand stiffness, which is functionally disabling 1, 2, 5
• Urgent orthopedic referral within 48-72 hours for definitive assessment 1, 2

If Hook Test is Negative (Complete Rupture):

• Emergent orthopedic surgical consultation - surgical repair within 2-3 weeks yields best outcomes 1, 2
• Delayed repair beyond 4 weeks significantly compromises functional results 1

Diagnostic Imaging

• MRI is the gold standard for confirming partial versus complete tears and assessing tendon retraction 1, 2
• Ultrasound can be used as initial imaging if MRI unavailable, though operator-dependent 6
• Plain radiographs are not useful for tendon pathology but may identify associated fractures 1

Treatment Based on Tear Severity

Partial Tears (<50% thickness):

• Conservative management with immobilization for 3-6 weeks 1
• NSAIDs for pain and inflammation control, though effects may take several days in severe cases 3
• Progressive rehabilitation after immobilization period with range of motion and strengthening exercises 1, 2

Complete or High-Grade Partial Tears (>50%):

• Surgical repair is strongly recommended for active patients to restore supination strength and prevent chronic weakness 1, 2
• Non-operative management results in 30-50% loss of supination strength 1

Critical Pitfalls to Avoid

• Do not delay surgical referral - tendon retraction and scarring after 3-4 weeks makes repair technically difficult with inferior outcomes 1, 2
• Do not restrict finger motion - failure to encourage immediate finger exercises leads to debilitating hand stiffness requiring prolonged therapy 1, 2, 5
• Do not assume minor injury based on maintained hook test - partial tears can progress to complete rupture with continued activity 1, 2
• Do not miss associated injuries - assess for fractures, neurovascular compromise, and compartment syndrome 1, 3

Red Flags Requiring Immediate Action

• Unremitting pain during follow-up warrants urgent reevaluation for complications 1, 2
• Progressive weakness suggests tear propagation 1
• Neurovascular symptoms (numbness, pallor, absent pulses) require emergent vascular surgery consultation 7