import { OnePagerSummary, ExamWarning, InfoCardGrid, InfoCard, MnemonicCard, EvidenceCard, VivaScenarioSection, VivaScenario, ExamCheatSheet, ContentSection, ExamPearl, SafetyAlert, NumberHighlightRow, NumberHighlight, Tabs, Tab, ComparisonTable } from '@/components/mdx' **Common peroneal nerve**. Target structure - wraps around fibular neck 1-2cm below head. Nerve itself is the surgical target. **Deep peroneal nerve**. Branch entering anterior compartment - supplies tibialis anterior, EHL, EDL, EDB. Motor to foot dorsiflexion. **Superficial peroneal nerve**. Branch entering lateral compartment - supplies peroneus longus/brevis. Sensory to dorsum of foot. **Lateral sural cutaneous nerve**. Branches from CPN proximally - injury causes numbness over lateral calf. ### Indications for CPN Decompression **Absolute Indications:** - Progressive motor weakness (foot drop) with compressive lesion - Failed conservative management after 3-6 months observation - Space-occupying lesion (ganglion cyst, schwannoma) - Open injury with nerve in continuity requiring exploration **Relative Indications:** - Persistent symptoms with documented compression on imaging - Iatrogenic injury after TKA or proximal tibial surgery - Positive Tinel sign at fibular neck with EMG confirming compression **Timing Considerations:** - Traumatic lesion: observe 3-4 months if nerve in continuity - Compressive lesion: earlier surgery if progressive or space-occupying - Post-TKA: explore early if no recovery by 6 weeks ### Contraindications **Absolute:** - Complete nerve transection requiring grafting (different procedure) - Active infection at surgical site - Irreversible nerve damage with chronic denervation (>18 months) **Relative:** - Central cause of foot drop (stroke, MS, spinal pathology) - L5 radiculopathy mimicking CPN palsy - Polyneuropathy (Charcot-Marie-Tooth) - decompression less effective - Unrealistic patient expectations **Important Differentials:** - L5 radiculopathy: weak hip abduction (gluteus medius), back pain, dermatomal sensory loss - Sciatic nerve lesion: weak hamstrings, absent ankle jerk - ALS: upper motor neuron signs, no sensory loss ### Pre-operative Assessment **Clinical Examination:** - Document motor function: tibialis anterior (4/5 = resisted ankle dorsiflexion) - Tinel sign at fibular neck (positive = regenerating/damaged nerve) - Sensory examination: lateral leg, dorsum of foot, first web space - Check for mass lesion (ganglion palpable 60% of time) - Assess gastrocnemius-soleus function (intact = not sciatic/tibial) **Investigations:** - **EMG/NCS**: Essential - confirms site, severity, chronicity - Conduction block at fibular neck = good prognosis - Fibrillation potentials in tibialis anterior = denervation - **MRI**: Rule out mass lesion, assess nerve signal changes - **Ultrasound**: Dynamic assessment, ganglion cysts, nerve caliber **Consent Discussion:** - 60-80% improvement if compressive etiology with good preoperative function - Complete foot drop >12 months: poor prognosis - Risk of worsening (2-5%), incomplete recovery, numbness ### Required Equipment **Basic Setup:** - Standard soft tissue tray - Bipolar cautery (essential for hemostasis near nerve) - Loupe magnification (2.5-3.5x) recommended - Nerve stimulator (optional but helpful) - Headlight **Positioning Aids:** - Lateral decubitus positioning equipment OR - Bump/sandbag for supine with hip elevation - Knee support to maintain slight flexion **Instruments:** - Fine dissection scissors (Metzenbaum, tenotomy) - Penfield dissectors - Vessel loops for nerve retraction - Self-retaining retractor (Weitlaner or Gelpi) **Closure:** - Absorbable sutures for fascia (if closing - leave LOOSE) - Skin staples or subcuticular suture ### Anatomical Course of CPN **Proximal Course:** - CPN separates from tibial nerve in distal thigh (at sciatic bifurcation) - Travels along medial border of biceps femoris tendon - Emerges between biceps and lateral head of gastrocnemius **At Fibular Neck:** - Wraps around fibular neck 1-2cm distal to fibular head - Subcutaneous for ~4cm - most superficial and vulnerable location - Gives off lateral sural cutaneous nerve proximally - Enters peroneus longus muscle through fibrous tunnel **Bifurcation:** - Divides into deep and superficial peroneal nerves within peroneus longus - Deep peroneal: enters anterior compartment through anterior intermuscular septum - Superficial peroneal: continues in lateral compartment **EXAM KEY**: The peroneus longus fascial edge (fibrous arch at muscle entry) is the MOST COMMON compression site - analogous to arcade of Frohse for PIN or Osborne's ligament for ulnar nerve. **Patient Position**: - Lateral decubitus (affected side up) - PREFERRED for optimal access - Alternative: Supine with bump under ipsilateral hip - Knee slightly flexed (15-20 degrees) to relax peroneus longus **Surface Markings:** - Mark fibular head (prominent landmark) - Mark course of CPN (1-2cm below head, curving anteriorly) - Mark planned incision (curvilinear, posterior to fibular neck) **Anaesthesia**: - General or regional (spinal/epidural) - Local anaesthesia possible for ganglion excision **Preparation:** - Full leg prep from mid-thigh to toes - Thigh tourniquet (optional - helps visualization but may affect nerve assessment) - If tourniquet used, deflate before closure to check hemostasis ### Step 1: Position and Mark Landmarks Position lateral decubitus with affected side up, or supine with bump under ipsilateral hip. Knee slightly flexed 15-20 degrees. Mark fibular head, fibular neck, and anticipated CPN course. **Technical Tip**: Palpate fibular head - CPN is 1-2cm distal and wraps around neck in subcutaneous plane. The nerve can sometimes be palpated as a cord-like structure. Inadequate positioning limiting surgical access - ensure full lateral access to fibular neck ### Step 2: Skin Incision Make 6-8cm curvilinear incision centered on fibular neck. Start posteriorly (following nerve course from popliteal fossa) and curve anteriorly distally. **Technical Tip**: Curvilinear incision follows nerve anatomy - CPN comes from posterior (popliteal fossa), wraps around neck, then dives anteriorly into peroneus longus. Incision too anterior may miss proximal compression sites; too posterior risks sural nerve ### Step 3: Dissect Through Subcutaneous Tissue Incise subcutaneous tissue carefully. Identify and protect the lateral sural cutaneous nerve (branches from CPN proximally). **Technical Tip**: The lateral sural cutaneous nerve branches proximally - injury causes numbness over posterolateral calf. Identify and protect with vessel loop. Lateral sural cutaneous nerve injury - be aware it branches from CPN proximal to fibular neck ### Step 4: Incise Deep Fascia and Identify CPN Proximally Incise deep fascia longitudinally. Identify CPN PROXIMAL to fibular head where it emerges from interval between biceps femoris and lateral head of gastrocnemius. **Technical Tip**: ALWAYS find nerve proximal first where it's easier and safer - in the interval between biceps femoris (anterior) and gastrocnemius (posterior). Misidentification of nerve - confirm with nerve stimulator if uncertain ### Step 5: Trace Nerve to Fibular Neck Trace nerve distally as it wraps around fibular neck. Place vessel loop around nerve for gentle retraction. The nerve is most superficial and vulnerable here - handle with extreme care. **Technical Tip**: The subcutaneous segment at the fibular neck is the site of maximum vulnerability - external compression (casts, positioning) affects nerve here. Direct nerve injury from excessive manipulation - use gentle handling and atraumatic technique ### Step 6: Release Peroneus Longus Fascia (KEY STEP) Identify the fibrous arch at entry to peroneus longus muscle. Release this fascial edge completely - this is the MOST COMMON compression site. **Technical Tip**: The peroneus longus fascial edge is the PRIMARY compression point - like arcade of Frohse for PIN. Complete release is essential for successful decompression. Incomplete release of fascial arch - visualize nerve freely passing through before proceeding ### Step 7: Release All Fibrous Bands Gently dissect nerve from all fibrous bands around fibular neck. Release any tight intermuscular septum. Ensure complete external neurolysis. **Technical Tip**: Release all constrictive tissue 360 degrees around nerve - scar, fibrous bands, tight fascia. The nerve should be freely mobile. Nerve handling trauma - use atraumatic technique, minimize direct manipulation ### Step 8: Follow to Bifurcation and Decompress Both Branches Follow nerve to bifurcation into deep and superficial peroneal nerves. Ensure BOTH branches are decompressed at their respective compression points. **Technical Tip**: Must decompress BOTH branches: Deep peroneal (anterior compartment - motor to dorsiflexion), Superficial peroneal (lateral compartment - eversion, dorsal foot sensation). Missing branch compression - incomplete decompression of either branch leads to persistent symptoms ### Step 9: Examine Nerve Quality Examine nerve for neuroma, intrinsic damage, hourglass constriction, or mass lesion. If ganglion present, excise completely with stalk. **Technical Tip**: Internal neurolysis (opening epineurium) is CONTROVERSIAL - no proven benefit and may worsen scarring. Only consider if obvious intraneural pathology. Unnecessary internal neurolysis - epineurotomy may worsen outcomes ### Step 10: Assess Nerve Continuity and Plan If nerve healthy externally but poor function: external neurolysis usually sufficient. If complete transection identified: mark for grafting (different procedure). **Technical Tip**: Complete lesion on EMG but nerve in continuity with neuroma-in-continuity: may benefit from nerve stimulation intraoperatively or observation for 3-4 months. Wrong surgical decision - avoid cutting nerve in continuity that may recover ### Step 11: Hemostasis and Closure Achieve meticulous hemostasis with bipolar cautery. If closing fascia, leave LOOSE or do not close at all. Close subcutaneous tissue and skin. **Technical Tip**: Do NOT close fascia tightly - creates new iatrogenic compression point. Many surgeons leave fascia completely open. Tight fascial closure causing iatrogenic compression - either leave open or close very loosely ### Immediate Post-operative - No splinting required unless combined procedure - Elevate leg 24-48 hours to minimize swelling - Weight bearing as tolerated immediately - Wound check at 2 weeks ### AFO (Ankle-Foot Orthosis) - Continue AFO for foot drop until motor recovery documented - Custom molded AFO if prolonged use anticipated - Must prevent equinus contracture ### Rehabilitation - Early ankle ROM exercises - Physiotherapy for strengthening as power returns - Gait training with AFO ### Follow-up - Clinical review at 6 weeks, 3 months, 6 months - EMG at 3-6 months to assess reinnervation - Recovery timeline: first signs at 3-4 months, continues up to 18-24 months ### Expected Recovery - **Good prognosis factors**: Compressive etiology, short duration, partial lesion, positive Tinel sign - **Poor prognosis factors**: Traumatic transection, duration >12 months, absent Tinel sign, no EMG improvement - **Recovery rates**: 60-80% meaningful improvement with appropriate patient selection 1. Kim DH, Murovic JA, Tiel RL, Kline DG. Management and outcomes in 318 operative common peroneal nerve lesions at the Louisiana State University Health Sciences Center. Neurosurgery. 2004;54(6):1421-1428. 2. Mont MA, Dellon AL, Chen F, Hungerford MW, Krackow KA, Hungerford DS. The operative treatment of peroneal nerve palsy. J Bone Joint Surg Am. 1996;78(6):863-869. 3. Fabre T, Piton C, Andre D, Lasseur E, Durandeau A. Peroneal nerve entrapment. J Bone Joint Surg Am. 1998;80(1):47-53. 4. Maalla R, Youssef M, Ben Lassoued N, Sebai MA, Essadam H. Peroneal nerve entrapment at the fibular head: outcomes of neurolysis. Orthop Traumatol Surg Res. 2013;99(6):719-722. 5. Spinner RJ, Atkinson JL, Tiel RL. Peroneal intraneural ganglia: the importance of the articular branch. J Neurosurg. 2003;99(2):319-329. 6. Schmalzried TP, Amstutz HC, Dorey FJ. Nerve palsy associated with total hip replacement. J Bone Joint Surg Am. 1991;73(7):1074-1080. 7. Idusuyi OB, Morrey BF. Peroneal nerve palsy after total knee arthroplasty: assessment of predisposing and prognostic factors. J Bone Joint Surg Am. 1996;78(2):177-184. 8. Kang HJ, Choi YR, Kang ES. Outcomes of arthroscopic excision of proximal tibiofibular joint ganglion cysts. J Bone Joint Surg Am. 2012;94(18):1678-1683. 9. Humphreys DB, Novak CB, Mackinnon SE. Patient outcome after common peroneal nerve decompression. J Neurosurg. 2007;107(2):314-318. 10. George SC, Boyce DE. An evidence-based structured review to assess the results of common peroneal nerve repair. Plast Reconstr Surg. 2014;134(2):302e-311e.

Common Peroneal Nerve Decompression

Common Peroneal Nerve Decompression