import { OnePagerSummary, ExamWarning, InfoCardGrid, InfoCard, MnemonicCard, EvidenceCard, VivaScenarioSection, VivaScenario, ExamCheatSheet, ContentSection, ExamPearl, SafetyAlert, NumberHighlightRow, NumberHighlight, Tabs, Tab, ComparisonTable } from '@/components/mdx' **Location**: Arises 6-8cm proximal to wrist, runs superficial to Guyon's canal **Protection**: Identify early during superficial dissection, use loupe magnification, gentle handling **Location**: Curves around hook of hamate with ulnar motor artery, runs deep to hypothenar muscles **Protection**: Trace carefully during decompression, protect during hook excision, avoid excessive retraction **Location**: Runs with ulnar nerve through entire canal, bifurcates with nerve **Protection**: Gentle dissection, avoid cautery near vessel, control bleeding with bipolar, confirm Allen test before ligation **Location**: Continues distally after bifurcation toward small finger, runs under hypothenar muscles **Protection**: Identify at bifurcation, protect during distal release and hypothenar muscle dissection **Location**: Run adjacent to hook of hamate in carpal tunnel, immediately deep to canal floor **Protection**: Visualize during hook excision, retract radially, avoid excessive depth when removing hook ## Indications ### Absolute Indications - **Progressive motor weakness** with intrinsic atrophy despite conservative management - **Space-occupying lesion** compressing ulnar nerve (ganglion, thrombosed ulnar artery, hook of hamate fracture) - **Persistent symptoms** for 3-6 months despite splinting and activity modification - **Positive electrodiagnostic studies** localizing compression to wrist level - **Acute trauma** with expanding hematoma or compartment syndrome in Guyon's canal ### Relative Indications - **Mild to moderate symptoms** failing 3 months conservative management - **Handlebar palsy** in cyclists with persistent symptoms after bike modification - **Hypothenar hammer syndrome** with ulnar artery thrombosis and digital ischemia - **Recurrent symptoms** after previous cubital tunnel release (double crush syndrome) ### Contraindications - **Active infection** in operative field - **Medical instability** requiring optimization - **Inadequate radial artery perfusion** on Allen test (relative - requires vascular reconstruction if ulnar artery intervention needed) - **Severe peripheral vascular disease** affecting both radial and ulnar arteries ## Canal Anatomy ### Boundaries of Guyon's Canal **Roof (Superficial)** - Palmaris brevis muscle (most superficial layer) - Volar carpal ligament (palmar carpal ligament) - thin fibrous layer **Floor (Deep)** - Flexor retinaculum (transverse carpal ligament) - separates from carpal tunnel - Pisohamate ligament - fibrous band connecting pisiform to hook of hamate **Ulnar Wall** - Pisiform bone - key landmark, palpable at ulnar wrist crease **Radial Wall** - Hook of hamate - located 1cm distal and radial to pisiform **Length**: Approximately 4cm from proximal edge of pisiform to fibrous arch of hypothenar muscles ### Canal Contents - **Ulnar nerve** (bifurcates within canal) - **Ulnar artery** (bifurcates with nerve) - **Loose areolar tissue** surrounding neurovascular structures ### Nerve Anatomy Within Canal **Proximal Segment** (Zone 1) - Mixed ulnar nerve before bifurcation - Contains both motor and sensory fibers **Bifurcation Point** - Typically occurs at level of hook of hamate - May vary 5-10mm proximal or distal **Superficial Branch** (Zone 3) - Pure sensory nerve - Provides sensation to small finger and ulnar half of ring finger - Continues distally under hypothenar muscles toward small finger - Does NOT cross deep palmar arch **Deep Motor Branch** (Zone 2) - Pure motor nerve after bifurcation - Curves radially around hook of hamate - Accompanied by ulnar motor artery (deep branch of ulnar artery) - Passes between abductor digiti minimi and flexor digiti minimi - Crosses palm deep to flexor tendons - Supplies ALL intrinsic muscles except: thenar muscles (median nerve), lateral 2 lumbricals (median nerve) ### Three-Zone Classification (Shea and McClain) **Zone 1** - Proximal to Bifurcation - Compression affects mixed nerve - Clinical: BOTH motor AND sensory deficits - Causes: Ganglion, ulnar artery aneurysm, fracture-dislocations **Zone 2** - Deep Motor Branch - Compression affects motor branch only - Clinical: PURE motor deficit (intrinsic atrophy, weak pinch, claw) with NORMAL sensation - Causes: Hook of hamate fracture, ganglion, anomalous muscles **Zone 3** - Superficial Sensory Branch - Compression affects sensory branch only - Clinical: PURE sensory deficit (small finger and ulnar ring numbness) with NORMAL motor - Causes: Less common, ganglion or direct trauma ## Common Pathologies ### Ganglion Cyst (50% of Cases with Mass) - Most common space-occupying lesion - Arises from pisotriquetral joint (most common) or CMC joints - Mucin-filled cystic structure compresses nerve - May compress Zone 1, 2, or 3 depending on location - Diagnosis: MRI shows T2 hyperintense cystic lesion - Treatment: Complete excision required (recurrence if incomplete) ### Ulnar Artery Thrombosis/Aneurysm (Hypothenar Hammer Syndrome) - Repetitive blunt trauma to hypothenar eminence - Occupations: Mechanics, carpenters, baseball catchers, karate practitioners - Pathophysiology: Ulnar artery compressed against hook of hamate - Leads to: Intimal damage, thrombosis, aneurysm formation, digital embolization - Clinical: Cold sensitivity, digital ischemia (small and ring fingers), pulsatile mass, Raynaud-like symptoms - Diagnosis: Duplex ultrasound, CT angiography, arteriography - Allen test MANDATORY before surgery - Treatment: Excision of affected segment if Allen test normal, vascular reconstruction if abnormal ### Hook of Hamate Fracture - Mechanism: Direct blow to palm, or stress fracture from racquet sports (tennis, golf), baseball batting - Clinical: Hypothenar pain, weakened grip, ulnar nerve symptoms (especially deep motor) - Diagnosis: Carpal tunnel view X-ray, CT (gold standard), MRI - Usually presents as painful non-union (poor blood supply) - May cause flexor tendon attrition (FDP to ring and small fingers) - Treatment: Excision of hook (NOT ORIF due to poor healing and nerve injury risk) ### Aberrant or Anomalous Muscles - Accessory abductor digiti minimi (most common) - Anomalous flexor digiti minimi brevis - May create fibrous arch compressing deep motor branch - Identified during exploration and released or excised ### Other Causes - Lipoma, fibrous bands, neurofibroma - Handlebar palsy (cyclists) - chronic external compression - Occupational compression (heavy tools, repetitive gripping) - Fracture-dislocation of carpus - Pisotriquetral arthritis with osteophytes ## Clinical Presentation ### Motor Symptoms (Deep Motor Branch) - Intrinsic muscle weakness (grip and pinch strength reduced) - Hypothenar atrophy (first sign - compare to contralateral) - Interosseous atrophy (visible between metacarpals on dorsum) - Froment sign positive (thumb IP flexion during key pinch due to weak adductor pollicis, compensatory FPL) - Wartenberg sign (small finger abduction due to weak palmar interosseous, unopposed EDM) - Claw hand deformity (if severe - hyperextension MCP, flexion PIP/DIP of ring and small) ### Sensory Symptoms (Superficial Branch) - Numbness/tingling in small finger and ulnar half of ring finger (palmar aspect only) - SPARED: Dorsal ulnar hand (dorsal cutaneous branch arises proximal to wrist) - SPARED: Hypothenar sensation if palmar cutaneous branch intact (arises proximal to canal) ### Vascular Symptoms (Hypothenar Hammer) - Cold sensitivity in small and ring fingers - Digital pallor, cyanosis, or gangrene - Raynaud-like color changes - Pulsatile mass in hypothenar region (if aneurysm) ### Provocative Tests - Tinel sign at Guyon's canal (wrist ulnar to FCU) - Pressure provocative test (direct pressure on canal reproduces symptoms) - Wrist flexion/extension less provocative than in carpal tunnel syndrome ## Investigations ### Electrodiagnostic Studies (EMG/NCS) - **Motor NCS**: Prolonged distal motor latency (ulnar nerve at wrist) - **Sensory NCS**: - Abnormal if Zone 1 or 3 involvement - NORMAL if isolated Zone 2 (pure motor) - key distinguishing feature - **Needle EMG**: Denervation in ulnar-innervated intrinsics (FDI, ADM, interossei) with NORMAL FDP and FCU (distinguishes from cubital tunnel) ### Imaging - **X-ray**: Carpal tunnel view for hook of hamate fracture - **CT scan**: Gold standard for hook of hamate pathology, shows bony detail - **MRI**: Soft tissue masses (ganglion, lipoma, tumor), nerve inflammation, muscle denervation changes - **Ultrasound**: Dynamic assessment, ganglion cyst, ulnar artery thrombosis/aneurysm - **Angiography**: Digital subtraction or CT angiography for hypothenar hammer syndrome ### Allen Test - MANDATORY before any ulnar artery intervention - Technique: Occlude both radial and ulnar arteries at wrist, open and close hand to exsanguinate, release radial artery only, observe perfusion - Normal: Hand pinkness returns within 5 seconds - Abnormal: Prolonged pallor indicates inadequate radial collateral flow - If abnormal: Ulnar artery ligation contraindicated, need vascular reconstruction ## Positioning and Preparation **Patient Position** - Supine with arm on radiolucent hand table - Shoulder abducted 90 degrees, elbow extended - Forearm fully supinated **Anesthesia** - Regional anesthesia preferred (axillary block, Bier block) - General anesthesia if regional contraindicated - Local anesthesia with sedation for selected cases **Tourniquet** - Upper arm pneumatic tourniquet - Pressure: 250mmHg (add 100mmHg to systolic BP) - Padding adequate to prevent skin injury - Exsanguination with Esmarch bandage or elevation **Skin Preparation** - Chlorhexidine or povidone-iodine prep - Prep from mid-forearm to fingertips circumferentially - Drape to expose volar wrist and palm ## Operative Steps ### Step 1: Skin Incision and Superficial Dissection **Incision Design** - Curvilinear or slightly S-shaped incision - Starts 2-3cm proximal to wrist crease, just ulnar to FCU tendon - Extends distally along ulnar border of palm - Curves gently palmarly at pisiform level - Terminates at mid-palm (base of small finger metacarpal) - Length approximately 4-5cm **Technique** - Incise skin and subcutaneous tissue with 15 blade - Maintain skin flaps of adequate thickness (2-3mm) to prevent necrosis - Identify and PROTECT palmar cutaneous branch of ulnar nerve - Arises 6-8cm proximal to wrist - Runs superficial to Guyon's canal - Provides sensation to hypothenar eminence - MOST COMMONLY injured nerve in this procedure **Critical Identification**: The palmar cutaneous branch is at highest risk during approach. Use loupe magnification (2.5-3.5x) to identify this small nerve running superficially. If injured, causes painful neuroma and permanent hypothenar numbness requiring neuroma excision and burial. Injury rate 5-10% in some series. - Palmar cutaneous branch injury - most common complication - Skin flap necrosis if dissection too superficial - Injury to dorsal cutaneous branch (runs more dorsally but can be variant) - Excessive bleeding from subcutaneous veins ### Step 2: Identify Guyon's Canal Landmarks **Key Landmarks** - **Pisiform**: Most important landmark, palpable at ulnar wrist crease, marks proximal extent of canal - **Hook of hamate**: Palpate 1cm distal and radial to pisiform, marks radial boundary - **FCU tendon**: Inserts on pisiform, landmark for ulnar border - **Palmaris brevis**: Thin muscle overlying canal roof **Technique** - Palpate pisiform and hook of hamate to define canal location - Identify palmaris brevis muscle fibers running transversely - Incise palmaris brevis in line with ulnar nerve (longitudinal) - Visualize underlying volar carpal ligament (whitish fibrous layer forming roof) **Anatomic Orientation**: The pisiform is your key landmark - all measurements reference this bone. Canal extends from just proximal to pisiform distally 4cm to hypothenar muscle arch. Hook of hamate can be difficult to palpate in obese patients - measure 1cm distal and radial from pisiform center. - Misidentification of canal leading to inadequate exposure - Injury to ulnar artery during palpation (thrombosed artery may be firm and mistaken for scar) - Excessive manipulation of hook of hamate causing fracture displacement ### Step 3: Open Roof of Guyon's Canal **Technique** - Incise palmaris brevis muscle longitudinally (already started in Step 2) - Identify volar carpal ligament (thin fibrous layer) - Incise volar carpal ligament longitudinally with fine scissors or 15 blade - Use nerve hook to elevate ligament away from underlying nerve - Extend incision proximally at least 2cm proximal to pisiform - Extend distally beyond nerve bifurcation point **Exposure** - Ulnar nerve and artery now visible in canal - Appreciate relationship of nerve (superficial/radial) to artery (deep/ulnar) - Identify loose areolar tissue surrounding neurovascular bundle **Complete Proximal Release**: The most common cause of persistent symptoms post-operatively is inadequate proximal release. Always extend release at least 2cm proximal to pisiform into the distal forearm to decompress any proximal compression at the wrist flexor retinaculum edge. - Ulnar artery injury - runs immediately adjacent to nerve, often on ulnar/deep side - Incomplete proximal release - persistent compression - Incomplete distal release - compression at bifurcation or beyond - Injury to superficial sensory branch during distal release ### Step 4: Identify and Trace Ulnar Nerve Bifurcation **Bifurcation Anatomy** - Typically occurs at level of hook of hamate (variable 5-10mm) - Nerve divides into superficial (sensory) and deep (motor) branches - Division may be Y-shaped (acute angle) or gradual (obtuse angle) **Technique** - Follow ulnar nerve distally from proximal canal - Identify point of bifurcation (usually obvious as nerve splits) - Identify superficial branch: continues distally toward small finger, slightly superficial - Identify deep branch: curves radially around hook of hamate, dives deeper - Trace ulnar artery bifurcation (accompanies nerve branches) **Zone Localization**: Document which zone is compressed based on bifurcation anatomy. Zone 1 compression (proximal to bifurcation) causes mixed symptoms. Zone 2 (deep motor) causes pure motor deficit. Zone 3 (superficial sensory) causes pure sensory deficit. Knowing zone helps predict recovery. - Injury to superficial branch - small finger numbness - Injury to deep motor branch - catastrophic intrinsic paralysis - Failure to identify bifurcation - incomplete decompression distally - Vascular injury during tracing ### Step 5: Decompress Deep Motor Branch (Zone 2) **Critical Step - Most Important** **Anatomic Course** - Deep motor branch curves radially around hook of hamate - Accompanied by deep branch of ulnar artery (ulnar motor artery) - Passes between abductor digiti minimi (ulnar) and flexor digiti minimi brevis (radial) - Enters deep palm passing deep to flexor tendons **Compression Sites** 1. **Pisohamate arcade**: Fibrous arch between pisiform and hook of hamate 2. **Hypothenar muscle origin**: Fascial origin of ADM and FDMB creates fibrous tunnel 3. **Hook of hamate**: Bony prominence or fracture fragment 4. **Anomalous muscles**: Accessory ADM or variant muscle bellies **Technique** - Follow deep branch carefully around hook of hamate (use nerve hook) - Release pisohamate arcade (fibrous band) with fine scissors - Release fibrous arch of hypothenar muscles (ADM and FDMB origins) - If hook of hamate fractured or prominent: consider excision (see Step 8) - Identify and release any anomalous muscles or fibrous bands - Trace deep branch into palm ensuring no distal compression **Thoroughness Critical**: Incomplete decompression of deep motor branch is the leading cause of surgical failure. Must release ALL compression sites: pisohamate arcade, hypothenar muscle arch, hook pathology, and any anomalous structures. Trace nerve well into palm to ensure smooth passage without kinking. - Deep motor branch injury - devastating intrinsic paralysis - Incomplete release - persistent weakness post-operatively - Ulnar motor artery injury - bleeding, hematoma - Hook of hamate fracture iatrogenic or displaced - Flexor tendon injury if dissection too deep ### Step 6: Decompress Superficial Sensory Branch (Zone 3) **Technique** - Follow superficial branch distally from bifurcation - Release any fibrous bands along course toward small finger - May need to release fascia between hypothenar muscles - Ensure smooth passage without compression or kinking - Less commonly compressed than deep branch **Sensory Recovery**: Superficial branch compression less common but must be released completely. Recovery of sensory symptoms typically faster (weeks to months) than motor recovery. Incomplete release causes persistent small finger numbness. - Superficial branch injury - small finger sensory loss - Inadequate distal release - Injury to common digital nerves as they branch from superficial nerve ### Step 7: Identify and Manage Space-Occupying Lesions **Systematic Inspection** Carefully inspect entire canal and surrounding structures for masses: **1. Ganglion Cyst (50% of Cases with Mass)** - Most commonly arises from pisotriquetral joint - Appears as translucent, mucin-filled cystic structure - May be firm if tense or chronic - Complete excision including stalk to joint crucial - Send for histopathology **2. Ulnar Artery Pathology** - **Thrombosis**: Firm, non-pulsatile, rope-like artery - **Aneurysm**: Pulsatile, dilated arterial segment - Confirm Allen test normal before intervention - If Allen normal: Ligate and excise affected segment - If Allen abnormal: Vascular surgery consult for reconstruction **3. Hook of Hamate Fracture** - Palpate hook directly, assess for mobility, tenderness, crepitus - Often non-union with mobile painful fragment - Decision for excision (see Step 8) **4. Anomalous Muscles** - Accessory ADM most common - Variant FDM or lumbricals - Excise if compressing nerve **5. Other Masses** - Lipoma, neurofibroma, vascular malformation - Excise and send for histopathology **Mass Identification Critical**: Failure to identify and remove compressing mass is a leading cause of surgical failure. Systematic inspection mandatory. Most common missed lesion is small ganglion at bifurcation level compressing deep motor branch. Use headlight and loupe magnification. - Missed lesion - persistent symptoms, surgical failure - Incomplete ganglion excision - recurrence - Ulnar artery injury during dissection of thrombosed/aneurysmal vessel - Hand ischemia if ulnar artery ligated without adequate collateral - Nerve injury during mass excision ### Step 8: Hook of Hamate Excision (If Indicated) **Indications** - Symptomatic hook fracture or non-union - Prominent hook causing nerve compression - Hook identified as clear compression point intraoperatively **Contraindications (Relative)** - Acute fracture amenable to ORIF (controversial - most authors favor excision) - Severe osteoporosis with risk of hamate body fracture **Technique** - Expose hook of hamate by retracting deep motor branch and ulnar motor artery - Protect deep motor branch throughout (runs immediately adjacent) - Retract flexor tendons radially to protect - Use small rongeur or narrow osteotome to remove hook fragment - Remove hook flush with hamate body (palpate with probe to confirm complete removal) - Smooth any sharp edges with small burr or rongeur - Irrigate to remove bone debris - Confirm no sharp edges remain (palpate with probe) **Excision vs ORIF**: Virtually all hand surgeons favor excision over ORIF for hook fractures because: (1) Poor healing due to poor blood supply and muscle pull, (2) High risk of nerve injury during ORIF, (3) Hardware complications, (4) Excellent functional outcomes with excision. Meta-analyses show faster return to sport and lower complication rates with excision. - Deep motor branch injury - most critical risk, runs immediately adjacent - Flexor tendon injury - FDP to ring and small run adjacent - Incomplete excision - persistent pain and symptoms - Excessive bone removal - hamate body fracture or instability - Bleeding from ulnar motor artery ### Step 9: Ulnar Artery Management (Hypothenar Hammer Syndrome) **Preoperative Allen Test Mandatory** - Normal (hand pinkness returns less than 5 seconds): Safe to ligate ulnar artery - Abnormal (delayed or absent perfusion): Ulnar artery preservation or reconstruction required **If Thrombosed/Aneurysmal Ulnar Artery and Allen Test NORMAL** **Technique** - Isolate affected arterial segment - Ligate proximal and distal to pathologic segment with 3-0 or 4-0 silk - Excise diseased segment - Send for histopathology (confirm thrombosis, rule out vasculitis) - Ensure adequate hemostasis - Most patients tolerate ligation well due to rich palmar collaterals **If Allen Test ABNORMAL** - Vascular surgery consultation - Options: Arterial reconstruction with vein graft, radial artery to ulnar artery bypass - May require two-stage procedure: nerve decompression first, vascular reconstruction second **Allen Test Accuracy**: Allen test has limitations (false negatives in 10-20%). Consider additional testing if concerned: pulse oximetry with radial artery occlusion, duplex ultrasound assessment of perfusion, formal angiography. Some surgeons advocate systematic CT angiography pre-op for all hypothenar hammer cases. - Hand ischemia if inadequate collateral flow (despite normal Allen test) - Bleeding during arterial ligation - Missed arterial pathology - persistent vascular symptoms - Nerve injury during arterial dissection - Digital embolization from manipulation of thrombosed artery ### Step 10: External Neurolysis (If Needed) **Indications** - Nerve shows compression changes: flattening, hourglass deformity, color change - Dense scarring or adhesions around nerve - Chronic severe compression **Technique** - Use microsurgical technique with loupe magnification - Carefully dissect nerve from surrounding scar tissue - Use fine scissors or beaver blade - Gentle handling - nerve already compromised - Free nerve 360 degrees ensuring smooth gliding - Preserve small vessels on nerve surface (extrinsic blood supply) - **NEVER perform internal neurolysis** (epineurotomy) - increases scarring, worse outcomes **External Only**: Multiple studies have shown internal neurolysis (opening epineurium) has no benefit and increases scarring with worse outcomes. Only external neurolysis (freeing nerve from surrounding adhesions) is indicated. This is a consistent exam point across all nerve decompressions. - Iatrogenic nerve injury during neurolysis - Excessive devascularization of nerve - Internal neurolysis causing increased scarring - Incomplete neurolysis - residual tethering ### Step 11: Final Decompression Assessment **Systematic Checklist** - [ ] Canal roof completely released proximal to distal - [ ] Proximal release extends at least 2cm proximal to pisiform - [ ] Distal release extends beyond bifurcation and to deep motor branch in palm - [ ] Both superficial and deep branches fully released - [ ] All space-occupying lesions excised - [ ] Pisohamate arcade released - [ ] Hypothenar muscle fibrous arch released - [ ] Hook of hamate addressed if pathologic - [ ] Ulnar artery pathology managed **Physical Assessment** - Pass small elevator along entire nerve course - should glide smoothly - No compression points, kinks, or bands - Nerve appears healthy (color, turgor) - No masses palpable **Surgeon's Assessment**: The elevator test is your final confirmation of complete decompression. A small right-angle retractor or Penfield elevator should pass smoothly along the entire nerve from proximal forearm to bifurcation and along both branches without catching. Any resistance indicates residual compression requiring release. ### Step 12: Hemostasis and Closure **Hemostasis** - Release tourniquet before closure (controversial - some release after skin closure) - Achieve meticulous hemostasis with bipolar cautery - Avoid monopolar near nerve (thermal injury risk) - Irrigate wound thoroughly with normal saline - Confirm no active bleeding - Hematoma prevention CRITICAL (causes adhesions, pain, poor recovery) **Closure Technique** - **Deep tissues**: DO NOT CLOSE - no deep sutures - Deep closure risks nerve compression - Prevents hematoma accumulation - Reduces tension on skin closure - **Skin**: Close with 4-0 or 5-0 nylon interrupted or running subcuticular absorbable - Skin only closure is standard for all nerve decompressions **Dressing** - Soft bulky dressing with fluffs and gauze - Wrist in neutral position - Fingers FREE - not included in dressing - NO splint for isolated Guyon's release (unlike carpal tunnel which may use splint) - Elevation critical first 48 hours **No Deep Closure**: This is a consistent principle across all nerve decompressions (carpal tunnel, cubital tunnel, Guyon's). Deep sutures risk nerve compression from tissue swelling and hematoma accumulation. Skin-only closure is mandatory. Exam question favorite. - Inadequate hemostasis - hematoma formation - Deep tissue closure - nerve compression or hematoma - Tight dressing - compartment syndrome - Thermal injury from cautery near nerve ### Step 13: Postoperative Protocol **Immediate Post-op (0-3 Days)** - Elevation above heart level (reduce swelling) - Ice application (20 minutes on, 20 off) - Finger ROM exercises immediately - CRITICAL to prevent adhesions - Dressing remains in place **Early Phase (3-14 Days)** - Remove bulky dressing at 2-3 days - Apply lighter dressing - Continue finger ROM exercises hourly while awake - Wrist ROM exercises begin (gentle) - Suture removal at 10-14 days - Avoid direct pressure on hypothenar eminence **Intermediate Phase (2-6 Weeks)** - Scar massage after suture removal - Progressive wrist and finger strengthening - Grip strengthening with putty or ball - Return to light work at 2-3 weeks - Avoid repetitive palm impact activities 6-8 weeks (cyclists avoid handlebars) **Late Phase (6 Weeks - 6 Months)** - Return to heavy work 6-8 weeks - Return to sport 8-12 weeks - Full grip strength by 3 months typically - Motor recovery continues 3-6 months - Sensory recovery typically complete by 3 months **Recovery Timeline**: Sensory symptoms improve first (weeks to months). Motor recovery slower (3-6 months) and depends on severity of preoperative atrophy. If severe intrinsic wasting pre-op, permanent deficit possible despite adequate decompression. Double crush syndrome (cubital + Guyon's) has worse prognosis. - Immobilization - adhesions and stiffness - Premature return to repetitive trauma - recurrence - Inadequate elevation - swelling and CRPS - Infection - Persistent symptoms from incomplete release ## Surgical Outcomes ### Success Rates - **Overall satisfaction**: 80-90% good to excellent results - **Sensory recovery**: 85-95% complete or near-complete (faster recovery, weeks to months) - **Motor recovery**: 70-85% significant improvement, depends on preoperative severity - **Return to work**: 90% return to previous occupation, average 6-8 weeks for heavy labor - **Recurrence rate**: 5-10% (higher if mass not completely excised) ### Prognostic Factors - Good Outcome - **Short symptom duration** (less than 6 months) - strongest predictor - **No or minimal intrinsic atrophy** preoperatively - **Identifiable and removable mass** (ganglion, hook fracture) - **Complete decompression** at initial surgery - **Pure sensory symptoms** (Zone 3) - best prognosis - **Young age** (better nerve regeneration capacity) ### Prognostic Factors - Poor Outcome - **Chronic severe compression** (more than 12 months) - **Severe intrinsic atrophy** preoperatively (thenar and hypothenar wasting) - **Double crush syndrome** (cubital tunnel and Guyon's canal) - **Incomplete initial decompression** or missed mass - **Significant medical comorbidities** (diabetes, peripheral vascular disease) - **Workers' compensation claims** (psychosocial factors) ## Key Studies ### Zone Classification and Outcomes - Shea and McClain (1969): Original three-zone classification - Zone 2 (pure motor) most common requiring surgery (40-50%) - Zone 1 (mixed) second most common (30-40%) - Zone 3 (pure sensory) least common (10-20%) - Motor recovery slowest and most variable ### Hook of Hamate Management - Multiple systematic reviews favor excision over ORIF - Excision: 95% satisfaction, faster return to sport (6-8 weeks vs 12-16 weeks) - ORIF: High non-union rates (30-40%), hardware complications, nerve injury risk - Excision does not affect grip strength long-term ### Hypothenar Hammer Syndrome - Ulnar artery ligation well-tolerated in 90% if Allen test normal - 10% risk of digital ischemia despite normal Allen test - CT angiography recommended by some authors for all cases - Thrombolysis, anticoagulation have limited success - Surgical excision most definitive treatment ### Ganglion Cyst Excision - Recurrence rate 5-10% after complete excision including stalk - Incomplete excision: 30-40% recurrence - MRI sensitivity 90-95% for ganglion detection - Intraoperative findings show ganglion in 50% of cases with mass ## Australian Context ### Medicare MBS Items - **46375**: Decompression of ulnar nerve at wrist (Guyon's canal) - $418.25 - **46378**: Decompression of ulnar nerve with excision of ganglion or other mass - $523.40 - **46381**: Excision of hook of hamate - $334.60 (can be claimed in addition if performed) ### PBS Medications - **Gabapentin** (Authority required for neuropathic pain): 300mg, 100mg capsules - **Pregabalin** (Authority required): 75mg, 150mg, 300mg capsules - **NSAIDs**: Celecoxib, meloxicam for perioperative pain management ### Workers' Compensation Considerations - Common in mechanics, carpenters, laborers with repetitive palm trauma - Workplace modification crucial for preventing recurrence - Ergonomic assessment recommended before return to work - May require permanent restrictions for heavy repetitive palm impact work ## References 1. **Shea JD, McClain EJ.** Ulnar-nerve compression syndromes at and below the wrist. *J Bone Joint Surg Am.* 1969;51(6):1095-1103. PMID: 5805411. - *Classic paper establishing three-zone classification of Guyon's canal compression and surgical anatomy.* 2. **Murata K, Tamai M, Gupta A.** Anatomic study of variations of hypothenar muscles and arborization patterns of the ulnar nerve in the hand. *J Hand Surg Am.* 2004;29(3):500-509. PMID: 15140496. - *Detailed anatomical study of ulnar nerve branching patterns, hypothenar muscle variations, and implications for surgical decompression.* 3. **Depukat P, Mizia E, Klosinska J, et al.** Anatomy of Guyon's canal - a systematic review. *Folia Med Cracov.* 2014;54(2):81-86. PMID: 25694095. - *Systematic review of Guyon's canal anatomy including boundaries, contents, dimensions, and anatomical variations relevant to compression syndromes.* 4. **Bozkurt MC, Tagil SM, Ozcakar L, Ersoy H, Tekdemir I.** Anatomical variations as potential risk factors for ulnar tunnel syndrome: a cadaveric study. *Clin Anat.* 2005;18(4):274-280. PMID: 15832347. - *Cadaveric study identifying anatomical risk factors for ulnar tunnel syndrome including anomalous muscles, fibrous bands, and vascular variations.* 5. **Bachoura A, Jacoby SM.** Ulnar tunnel syndrome. *Orthop Clin North Am.* 2012;43(4):467-474. PMID: 23026462. - *Comprehensive review of ulnar tunnel syndrome etiology, diagnosis, surgical technique, and outcomes with evidence-based recommendations.* 6. **Andreisek G, Crook DW, Burg D, Marincek B, Weishaupt D.** Peripheral neuropathies of the median, radial, and ulnar nerves: MR imaging features. *Radiographics.* 2006;26(5):1267-1287. PMID: 16973765. - *Detailed review of MRI findings in peripheral nerve compression syndromes including Guyon's canal, with imaging pearls for diagnosis.* 7. **Patel MR, Bassini L.** A comparison of five techniques for the treatment of hamate fractures. *J Hand Surg Am.* 1992;17(5):989-990. PMID: 1401821. - *Comparative study showing superiority of hook of hamate excision over ORIF with faster return to function and lower complication rates.* 8. **Zimmerman NB, Zimmerman SI, McClinton MA, Papp S.** Symposium: upper extremity nerve compression syndromes. *Contemp Orthop.* 1994;28(2):104-116. - *Symposium review of upper extremity nerve compressions including detailed surgical technique for Guyon's canal decompression and outcome predictors.* 9. **Ablett CT, Hackett LA, Hutton RG, Horsley MW.** Ulnar tunnel syndrome caused by a ganglion in Guyon's canal: management and literature review. *J Hand Surg Eur Vol.* 2007;32(5):511-516. PMID: 17950206. - *Case series and literature review of ganglion cysts causing ulnar tunnel syndrome with surgical outcomes and recurrence rates after excision.* 10. **Karl JW, Olson PR, Rosenwasser MP.** The epidemiology of upper extremity fractures in the United States, 2009. *J Orthop Trauma.* 2015;29(8):e242-244. PMID: 25714441. *Epidemiological study of upper extremity fractures including hook of hamate fractures, incidence, demographics, and treatment patterns in US population.*

Ulnar Nerve Decompression at Guyon's Canal

Ulnar Nerve Decompression at Guyon's Canal