Peroneal Nerve Palsy

synonyms: foot drop

Peroneal Nerve Palsy ICD-9

Peroneal Nerve Palsy Etiology / Epidemiology / Natural History

• Occurs in 14%-40% of knee dislocations.

Peroneal Nerve Palsy Anatomy

• Peroneal nerve innervates: extensor hallucis longus, extensor digitorum brevis, tibialis anterior, peroneus longus.
• Extensor hallucis longus is innervated most distally and recovers last after peroneal nerve palsy.
• Lies superficial to the lateral head of the gasctrocnemius.
• Mean distance from the posterolateral corner of the tibia = 1.49cm.
• Common peroneal nerve emerges from the popliteal fossa running superficial to the lateral head of the gastrocnemius and posterior to the biceps femoris tendon. It wraps around the fibular neck. Motor = short head of the biceps femoris. Sensory = lateral sural cutaneous nerve= sensation to the superior aspect of the lateral side of the leg. Divides into superficial and deep branches beneath the proximal aspect of the peroneus longus muscle.
• Superficial peroneal nerve: Motor= lateral compartment of the leg (peroneus longus and brevis). sensory = lateral aspect of the lower leg and the dorsum of the foot.
• Deep peroneal nerve: Motor = anterior compartment of the leg (tibialis anterior, extensor hallucis longus, extensor digitorum longus, peroneus tertius). Sensory = first dorsal webspace.

Peroneal Nerve Palsy Clinical Evaluation

• Document neurovascular exam: Superficial peroneal = active foot eversion. Deep peroneal = tibialis anterior, EHL. See Muscle Grading.
• Test tibialis posterior function with resistance to plantar flexion and inversion. Weakness indicates that lesion is likely from L5 radiculopathy instead of peroneal nerve palsy. Tibialis posterior is innervated by the tibial nerve.

Peroneal Nerve Palsy Xray / Diagnositc Tests

• EMG/NCV. Nerve injury indicated by postive sharp waves, fibrillation potentilas and polyphasic potentials. Generally not present until 3 weeks after injury.

Peroneal Nerve Palsy Classification / Treatment

• Initial: prevention of equinovarus deformity using an ankle-foot orthosis (AFO).
• Physical therapy: strengthen any remaining functional muscles and stretch the posterior ankle capsule should. Neuromuscular electrical stimulation (NMES) may be useful to prevent of atrophy of peroneal supplied muscles.
• Must rule out compartment syndrome as cause especiallty in acute situations.
• After TKA : occurs primarily with correction of fixed valgus deformities with flexion contractures. Initial treatment = release of compressive dressings and knee flexion.
• If complete injury with no recovery indicated on intial EMG consider early exploration and neuolysis.
• Surgical treatment options: surgical exploration with neurolysis (Thoma A, Plast Reconstr Surg 2000;107:1183), primary nerve repair, nerve grafting (Kim DH, Neurosurgery 2003;53:1114), and posterior tibial tendon transfer (Yeap JS, Int Orthop 2001;25:114).

Peroneal Nerve Palsy Associated Injuries / Differential Diagnosis

• HNPP
• L5 Radiculopathy
• Knee dislocation
• PLC injury

Peroneal Nerve Palsy Complications

• Foot drop
• Gait impairment

Peroneal Nerve Palsy Follow-up Care

• Extensor hallucis longus is innervated most distally and recovers last after peroneal nerve palsy.

Peroneal Nerve Palsy Review References

• Rosson GD, CORR 2005 Sep;438:248)
• Hems TE, Injury. 2005 May;36(5):651
• Garozzo D, J Neurosurg Sci. 2004 Sep;48(3):105
• °