What is the guideline for managing Common Peroneal Nerve (CPN) palsy after tibial plateau surgery?

Management of Common Peroneal Nerve (CPN) Palsy After Tibial Plateau Surgery

For CPN palsy following tibial plateau surgery, initial management should focus on clinical observation with serial examinations for 3-4 months, as the majority of patients (>80%) will achieve functional recovery without intervention, particularly those with incomplete nerve injuries. 1, 2

Initial Assessment and Monitoring

Immediate Post-Operative Period

• Document baseline motor function using the Medical Research Council (MRC) grading system, specifically testing tibialis anterior (TA) and extensor hallucis longus (EHL) strength 3
• Obtain nerve conduction studies to confirm CPN injury and establish baseline electrophysiologic data 3
• Distinguish between complete versus incomplete palsy, as this dramatically affects prognosis: incomplete palsies recover fully in 87.3% of cases, while complete palsies recover functionally in only 38.4% 2

Risk Stratification by Fracture Pattern

• Medial column fractures carry 5% CPN injury risk and bicondylar fractures carry 3% risk, making these high-risk patterns requiring vigilant monitoring 1
• C3 fragmentary patterns are most commonly associated with CPN palsy 1

Conservative Management (First 3-4 Months)

Non-Operative Treatment

• Prescribe ankle-foot orthoses (AFOs) to provide immediate gait improvement and prevent equinus contracture development 4
• Serial clinical examinations every 4-6 weeks to document any signs of motor recovery 5, 3
• Repeat electrodiagnostic studies at 3 months if no clinical improvement is evident 3

Expected Recovery Timeline

• Most tibial plateau fracture-associated CPN palsies recover within 2 years, with better prognosis than other knee trauma mechanisms 1
• Younger patients have better neurologic recovery outcomes 2

Surgical Intervention Criteria

Indications for Surgery (After 3-4 Months)

If no spontaneous recovery occurs within 3-4 months after injury, surgical treatment should be pursued regardless of causative mechanism. 5

Surgical Options Based on Timing and Nerve Status

Early Surgical Exploration (3-4 Months Post-Injury)

• Perform CPN decompression and neuroplasty at the lateral fibular neck if nerve continuity is demonstrated intraoperatively 5, 3
• Use prone positioning with microscope assistance to visualize the nerve from lower popliteal region to peroneal tunnel 3
• Expected improvement in motor function occurs in 90% of patients when nerve repair is combined with tendon transfer 5

Combined Nerve Repair and Tendon Transfer (Preferred Approach)

The one-stage procedure combining nerve repair with tibialis posterior tendon transfer dramatically improves outcomes compared to nerve repair alone. 5

• Perform neuroma resection with nerve grafting if nerve discontinuity is identified 5
• Simultaneously execute posterior tibial tendon transfer to restore antigravity dorsiflexion and prevent equinus contracture that impedes nerve regeneration 5, 2
• This combined approach achieves neural regeneration in 90% of patients at 2-year follow-up 5

Isolated Tendon Transfer (Chronic Cases >12-18 Months)

• Posterior tibial tendon transfer is the most predictable means of reestablishing antigravity dorsiflexion in persistent CPN palsy without recovery 2, 4
• Consider this definitive treatment when no signs of nerve recovery are evident after 12-18 months 4

Common Pitfalls and Caveats

Critical Timing Considerations

• Avoid premature surgical intervention before 3-4 months, as spontaneous recovery is common and surgery may be unnecessary 5, 1
• Do not delay surgery beyond 4 months without recovery, as prolonged denervation worsens outcomes 5

Technical Considerations

• Nerve repair alone without tendon transfer yields poor results (recovery in only 1 of 6 patients in historical series) 5
• The force imbalance between functioning flexors and paralyzed extensors creates fixed equinus that obstructs reinnervation, making tendon transfer mechanically essential 5

Prognostic Factors

• Sharp injuries and severe knee dislocations have excellent recovery, while crush injuries and gunshot wounds show less consistent improvement 5
• Isolated neurologic interventions without tendon transfer show recovery rates of only 0-30% 2
• Only 40% of patients with complete motor palsy will regain antigravity dorsiflexion without tendon transfer 2