Is numbness a normal finding after a small laceration to the skin over the Achilles tendon with intact mobility and normal pulses?

Management of Numbness After Laceration Over the Achilles Tendon

Numbness is a common and expected finding after a small laceration to the skin over the Achilles tendon, particularly when mobility remains intact and pulses are normal.

Assessment of Achilles Region Injuries

When evaluating a patient with a laceration over the Achilles tendon area:

1. Neurovascular Assessment:

   • Check for intact mobility of the ankle joint 1
   • Verify normal pulses (dorsalis pedis and posterior tibial) 1
   • Assess sensation in the distribution of the sural nerve 2

2. Physical Examination Tests:

   • Thompson/Simonds squeeze test to confirm Achilles tendon integrity 1
   • Evaluate ankle plantar flexion strength 1
   • Check for palpable gap or defect in the tendon 1
   • Assess passive ankle dorsiflexion 1

Understanding Post-Laceration Numbness

The numbness after a small laceration over the Achilles tendon is typically due to:

• Sural nerve involvement: The sural nerve courses laterally to the Achilles tendon at varying distances (from 21.48 mm at insertion to 0.81 mm proximally) 2
• Age-related factors: In older patients, the sural nerve passes significantly closer to the Achilles tendon, increasing risk of nerve involvement 2
• Anatomical variants: Three common variants exist in how the nerve relates to the tendon 2

Management Approach

1. Initial Assessment:

   • If mobility is intact and pulses are normal, numbness alone is not concerning for major injury 3
   • Delayed physical examination (4-5 days post-injury) optimizes sensitivity (84%) and specificity (96%) for ligament injuries 3

2. Treatment Plan:

   • Conservative management is appropriate for isolated numbness with intact mobility and pulses
   • Monitor for improvement of sensation over 1-3 months
   • Sensory symptoms typically resolve or significantly improve within 6 months in 99% of patients with peripheral nerve involvement 4

3. Follow-up Recommendations:

   • Clinical follow-up at 2 weeks and 4-6 weeks to assess healing and sensation 3
   • Consider referral if no improvement after 6 weeks of conservative treatment 3

Important Considerations

• Sural nerve anatomy: The nerve courses progressively closer to the Achilles tendon as you move proximally up the leg 2
• Risk factors: Older patients have the sural nerve positioned closer to the Achilles tendon, increasing risk of nerve involvement during injury or repair 2
• Prognosis: Temporary worsening of nerve function may occur in a small percentage of patients (approximately 2%) but typically resolves 4

When to Consider Further Evaluation

Seek further evaluation if:

• Numbness worsens or spreads
• Motor function becomes impaired
• Pain becomes severe or persistent
• Signs of infection develop
• No improvement in sensation after 6 weeks 3

The high incidence of favorable outcomes with conservative management of minor lacerations in this area supports a watchful waiting approach when mobility and pulses remain normal 5.