Osteolysis of Distal Clavicle
June 25, 2019
2019 UofT Sports Medicine Conference
August 6, 2019

Peroneal Nerve Entrapment/Palsy

 

Common Peroneal Nerve Entrapment/Palsy

Case 1:

45F training for her first marathon. Race is in September. Presents with 2 week history of numbness to the lateral left leg. Aggravated with plantarflexion and relieved with dorsiflexion.

No weakness

Case 2:

60F with history of left knee osteoarthritis presents with sudden onset of left foot drop. Patient was wearing a tight fitting over-the-counter knee brace while walking during a European vacation to provide relief of her knee symptoms.

Case 3:

20 yo football/soccer player – tackle to right lateral knee.   Initially pain over lateral knee which resolved within 3 days.  Then he noticed decreased sensation on dorsum of left foot.

Description:

Anatomy

The common peroneal nerve (CPN), also known as the fibular nerve, is derived from the L4, L5, S1, and S2 nerve roots. This along with the tibial nerve are the two terminal branches of the sciatic nerve. The peroneal nerve is prone to stretch and direct injury due to its posterolateral location. The CPN separates from the tibial nerve in the superior aspect of the popliteal fossa. It crosses posterior to the lateral head of the gastrocnemius through the posterior intermuscular septum and becomes subcutaneous while it curves around the head of the fibula deep to the peroneus longus muscle.

There are three branches of the peroneal nerve:

(1) Lateral cutaneous nerve of the calf

(2) Superficial peroneal nerve (SPN)

(3) Deep peroneal nerve (DPN).

Superior Peroneal Nerve:

  • Motor: Peroneus Longus and Brevis muscles
  • Sensory: Lateral lower leg and dorsum of the foot

Deep Peroneal Nerve:

  • Course: runs along the anterior cortex of the fibula and then travels anterior and medial to the intermuscular septum between the anterior and lateral compartments. This is a potential point of entrapment.
  • Motor: tibialis anterior, extensor digitorum longus, extensor hallucis longus, peroneus tertius, and extensor digitorum brevis muscles.
  • Sensory: 1st dorsal web space.

Figure 1 anatomy of peroneal/fibular nerve (4):

From: https://teachmeanatomy.info/lower-limb/nerves/sciatic-nerve/

Etiology

  • Compression (most common)
    • Recent significant weight loss
    • Habitual leg crossing
    • Prolonged squatting
    • Masses
      • Intraneural and extraneural lesions
    • Fibrous band at the origin of the peroneus longus muscle
  • Trauma
    • Knee dislocation
    • Severe ankle inversion injuries
    • Laceration
    • Direct blunt trauma
  • Diabetes Mellitus
  • Lower extremity neuropathies
  • Iatrogenic
    • Positioning during anesthesia
    • Prolonged bed rest
    • Casting
    • Bracing
    • Compression wrapping
    • Use of Pneumatic compression devices

 

Clinical Presentation

Signs and symptoms will vary depending on the severity and location of the injury

  • Foot drop
    • most common symptom
    • “catching toes while walking”
    • can be acute or chronic
  • Numbness/dysesthesias
    • Lateral leg
    • Dorsal foot
    • First toe web space
  • Pain
    • If concurrent traumatic injury
    • Overall, uncommon

 

Physical Examination:

  • Gait assessment
    • Steppage gait
      • Due to weakened/paralyzed ankle dorsiflexors
      • Affected knee is lifted higher during swing phase to avoid dragging toes on the floor
      • Forefoot slaps to the ground after heel strike
    • Sensation
      • Numbness/dysesthesia to:
        • upper lateral leg
          • lesion proximal to fibular head
          • may signal potential involvement of sciatic nerve or lumbosacral nerve root
        • Lower lateral leg and dorsum of the foot
          • Superficial peroneal nerve
        • First web space
          • Deep peroneal nerve
        • Strength
          • Foot eversion weakness (SPN)
          • Foot/toe dorsiflexion (DPN)
          • Issue with both of the above indicate lesion involving CPN
        • Special Tests
          • Tinel sign near fibular head

 

Differential Diagnosis:

  • Lumbosacral radiculopathy
  • Sciatic Nerve injury
  • Chronic Exertional Compartment Syndrome
  • Diabetic Neuropathy
  • Mononeuritis Multiplex
  • Amyotrophic Lateral Sclerosis (ALS)
  • Inflammatory demyelinating conditions
  • Tarsal Tunnel Syndrome

 

Diagnostic Studies

  • X-ray
  • MRI and ultrasound
    • Determine soft-tissue sources of impingement
  • NCS/EMG
    • Can be used to help evaluate the motor and sensory axons of the peroneal nerve and its branches.
    • Localizes site of injury, determines severity
    • Can be repeated q3months to monitor recovery
    • EMG to Tibialis Anterior
      • Short head of biceps femoris and a tibial innervated muscle distal to the knee to identify more proximal lesions and/or injury to the sciatic nerve
    • When these studies indicate more advanced disease than surgical intervention may be indicated
    • >50% conduction delay and evidence on EMG of substantial disruption of the CPN innervation to the musculature than surgical nerve decompression is indicated and may increase the likelihood of a favourable outcome

 

Management
Nonsurgical

  • Activity modification
    • Cessation of leg crossing
  • Padding on the prominent fibular head after direct traumatic injury. These may be worn at night to prevent compression while sleeping
  • Night splints
    • Prevent contractures
  • Rehabilitation
    • PT and orthotic devices
    • Custom AFO
    • Stretching the contralateral muscles groups
    • Electrical stimulation for substantial muscle weakness
    • Progressive strengthening of dorsiflexors and evertors once autonomous muscle contraction is present
    • Prognosis dependent on degree of dysfunction at presentation

Surgical

Acute Injuries

  • Contusion, stretch injuries, lacerations, crush injuries should be assessed to determine the degree of functional loss
  • Neuropraxia = monitor
  • Complete motor or sensory loss = Surgery
  • Surgical exploration and decompression with rapidly deteriorating lesion with no improvement within 3 months
  • Nerve laceration
    • Surgical exploration within 72 hours, attempt at primary repair
    • If unable to perform primary repair due to significant gapping = nerve grafting
    • Nerve transfer also possible
  • Compressive Masses
    • Excision of a compressive mass
    • Masses that are causing significant or progressive motor loss should be removed
    • Extraneural lesions
      • Fibular osteochondromas
      • Vascular malformation
      • Extraneural cysts
    • Intraneural lesions
      • Approach with caution
      • Schwannoma, neurofibroma, intraneural ganglion cyst from superior tibiofibular joint should be dissected free, with the stalk traced and disconnected from the joint to prevent recurrence
    • Idiopathic/Postoperative Compression
      • Surgical decompression if no improvement with non-surgical approach
      • Minimum 3 months
        • Nerve function improvement may be seen for up to 6 months
      • If patient fails to show clinical signs of improvement or if motor loss is rapidly progressive, decompression is warranted
      • Evidence of severe conduction loss or disruption of motor innervation
      • Neurolysis = 97% return to function

Author:  Dr. Alessandro Francella, MD, CCFP, Dip. Sport Med. (Jul 31, 2019 PR ND)

References:

  1. Poage C, Roth C, Scott B. Peroneal Nerve Palsy: Evaluation and Management. J Am Acad Orthop Surg. 2016 Jan; 24(1):1-10.
  2. Van Zantvoort A, Setz M, Hoogeveen A, Scheltinga M. Common Peroneal Nerve Entrapment in the Differential Diagnosis of Chronic Exertional Compartment Syndrome of the Lateral Lower Leg: A Report of 5 Cases. Orthop J Sports Med. 2018 Aug; 6(8).
  3. Rutboke S. Overview of lower extremity peripheral nerve syndromes. UpToDate.com. Last Updated: Nov 2018.
  4. https://teachmeanatomy.info/lower-limb/nerves/sciatic-nerve/