Distal Biceps Tendon Injuries

 

 Epidemiology

• Relatively uncommon (~10% of all biceps ruptures)
• Typically affects:
  • Men
  • Age 40–50 years
  • Dominant arm
• Much less common than proximal (shoulder) biceps rupture

 Mechanism of Injury

• Usually a single traumatic event
• Classic scenario:
  • Elbow flexed
  • Sudden eccentric load (forced extension)
• Patients often report:
  • “Pop” sensation
  • Immediate pain

 Risk Factors

• Smoking (major risk)
• Anabolic steroid use
• Male gender
• Repetitive forearm use

 Anatomy Highlights

• Main functions of biceps:
  • Supination (primary role)
  • Elbow flexion (secondary to brachialis)
• Two heads:
  • Long head  more supination
  • Short head  more flexion
• Important structure:
  • Lacertus fibrosus (bicipital aponeurosis)
    • May remain intact  limits tendon retraction

 Clinical Presentation

• Sudden pain in antecubital fossa
• Weakness:
  • Supination (most affected)
  • Flexion (variable)
• Visible deformity:
  • Reverse Popeye sign

 Physical Examination Tests

1. Hook Test (Most reliable)

• Try to hook tendon with finger
• ` Cannot hook  positive test (rupture)

2. Squeeze Test

• Squeeze biceps  look for forearm supination
• No movement – rupture

 Imaging

• X-ray: usually normal
• MRI:
  • Gold standard for:
    • Partial tears
    • Chronic/retracted tears
    • Surgical planning

 Classification

• Complete vs Partial
• Acute vs Chronic

 Treatment

 Non-Operative (Selective cases)

Indications:

• Low-demand patients
• Medically unfit
• Patient preference

Expected deficits:

•  Flexion strength: 10–20%
•  Supination strength: 30–40%
•  endurance

Still acceptable functional outcomes for some patients

 Operative Treatment (Most common)

Techniques:

1. Single Incision

• Anterior approach
• Fixation with:
  • Cortical button (most common)
  • Suture anchors

Pros:

• Smaller incision
• Easier technique

Cons:

• Risk of nerve injury (especially PIN)

2. Double Incision

• Anterior + posterior

Pros:

• More anatomic repair (theoretical)
• Less nerve risk

Cons:

• Risk of:
  • Heterotopic ossification
  • Radioulnar synostosis

 Fixation Methods

• Cortical button  strongest biomechanically
• Suture anchors
• Bone tunnels
• Interference screws (less used alone)

 Outcomes

• Both single & double incision:
  •  Similar functional results
  •  Good recovery
• Complications:
  • Single incision  nerve issues
  • Double incision  heterotopic ossification

 Partial Tears

• Symptoms similar but:
  • Hook test negative
  • Tendon still palpable

Treatment:

• <50% tear  try conservative
• 50% tear  surgery often considered

In practice: decision is individualized

 Chronic Tears (>4–12 weeks)

Problems:

• Tendon retraction
• Scar formation
• Muscle atrophy

Treatment Options:

1. Direct repair (if possible)

• May need elbow flexed up to 90°

2. Reconstruction

• Using graft (e.g., Achilles allograft)

3. Tenodesis to brachialis

• Reduces pain but does NOT restore supination strength

 Key Surgical Insight

• Repairs done in flexion (even up to 90°) can:
  gradually stretch out over 6–8 weeks
  regain full extension

 Take-Home Messages

• Distal biceps rupture = eccentric overload injury
• Supination weakness is the key deficit
• Diagnosis is mainly clinical
• Surgery is preferred for active patients
• No clear superiority:
  • Single vs double incision
• Chronic cases are more complex and often need graft

 

Courtesy: Garett Sobol MD, New Jersey, USA