Distal Biceps Rupture

Epidemiology

• Incidence: ~1–5 per 100,000

• Age: 40–60 years

• Predominantly male (≈90–95%)

• More common in the dominant arm (not absolute)

Mechanism of Injury

Sudden eccentric load on a flexed elbow during forced extension.

Typical scenario:

• Lifting a heavy object → tendon avulses during extension

Risk Factors

• Smoking

• Anabolic steroid use

• High BMI

• Degenerative tendon changes

Anatomy

• Distal insertion: radial tuberosity

• Footprint:

  • Short head → distal and radial

  • Long head → proximal and ulnar

Functional contribution:

• Long head → supination

• Short head → flexion

Lacertus fibrosus (bicipital aponeurosis):

• Intact → limits retraction

• Torn → marked proximal migration

Pathophysiology

• Tendon avulsion from radial tuberosity

• Often complete rupture

• Proximal retraction of muscle belly

Contributing factors:

• Hypovascular zone

• Tendon degeneration

• Mechanical impingement

Clinical Presentation

• Sudden antecubital pain

• Audible “pop”

• Swelling and ecchymosis

Functional deficit:

• Supination ↓↓

• Flexion ↓

Physical Examination

Key Findings

• Reverse “Popeye” deformity

• Palpable tendon defect

• Asymmetry

Special Tests (High-yield)

• Hook Test
  Inability to hook tendon → suggests complete rupture
  No forearm supination → rupture

• Diagnosis is often clinical

Imaging

X-ray

• Usually normal

• Used to exclude other pathology

MRI (Gold standard)

• Partial vs complete tear

• Degree of retraction

• Surgical planning

Ultrasound

• Dynamic and useful

• Operator dependent

Classification

By Extent

• Partial rupture

• Complete rupture

By Timing

• Acute (<3–4 weeks)

• Subacute

• Chronic (>8–12 weeks)

Treatment

Nonoperative Management

Indications

• Low-demand patients

• Partial tears

• High surgical risk

Outcomes

• ~30–40% loss of supination strength

• ~20% loss of flexion strength

• Possible cosmetic deformity

Operative Treatment

Indications

• Complete rupture

• Active patients

• Functional demand

Timing

• Ideal: within 2–3 weeks

• Delay → retraction → more complex repair

Surgical Techniques

Approach

• Single incision (anterior)

  • Less dissection

  • Higher nerve injury risk

• Double incision

  • More anatomic footprint

  • Risk of heterotopic ossification

Fixation Methods

• Cortical button (strongest fixation)

• Suture anchors

• Interference screw

• Bone tunnels

Complications

• Nerve injury (most common):

  • Lateral antebrachial cutaneous nerve

  • Posterior interosseous nerve

• Heterotopic ossification (more with double incision)

• Re-rupture (rare)

• Stiffness

• Hematoma / infection

Prognosis

• Excellent with early repair

• Near-normal strength recovery

Worse outcomes with:

• Delayed treatment

• Chronic rupture

Pits and Pearls

• Hook test is the most reliable clinical test

• Supination loss is more significant than flexion loss

• Early surgery provides best outcomes

• Lacertus fibrosus affects retraction

Pitfalls

• Misdiagnosing as muscle strain

• Delayed referral

• Ignoring partial tears

• Underestimating functional deficit

Concept Summary

• Supination loss drives disability

• Diagnosis is mostly clinical

• Early repair is key to optimal outcome

Mini Decision Algorithm