High Yield Overview

ULNAR NERVE DECOMPRESSION AT GUYON'S CANAL

Curvilinear incision along ulnar border of palm from wrist to mid-palm | intermediate

Critical Danger Structures

Palmar Cutaneous Branch

Location: Arises 6-8cm proximal to wrist, runs superficial to Guyon's canal

Protection: Identify early during superficial dissection, use loupe magnification, gentle handling

Deep Motor Branch

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

Ulnar Artery

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

Superficial Sensory Branch

Location: Continues distally after bifurcation toward small finger, runs under hypothenar muscles

Protection: Identify at bifurcation, protect during distal release and hypothenar muscle dissection

Flexor Tendons

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

Mnemonic

GUYONGUYON - Anatomic Boundaries

Mnemonic

HAMMERHAMMER - Hypothenar Hammer Syndrome Features

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

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

Exam Pearl

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.

Dangers at this step

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)

Exam Pearl

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.

Dangers at this step

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

Exam Pearl

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.

Dangers at this step

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)

Exam Pearl

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.

Dangers at this step

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

Pisohamate arcade: Fibrous arch between pisiform and hook of hamate
Hypothenar muscle origin: Fascial origin of ADM and FDMB creates fibrous tunnel
Hook of hamate: Bony prominence or fracture fragment
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

Exam Pearl

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.

Dangers at this step

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

Exam Pearl

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.

Dangers at this step

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

Exam Pearl

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.

Dangers at this step

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)

Exam Pearl

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.

Dangers at this step

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

Exam Pearl

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.

Dangers at this step

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

Exam Pearl

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.

Dangers at this step

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

Exam Pearl

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

Exam Pearl

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.

Dangers at this step

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

Exam Pearl

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.

Dangers at this step

Immobilization - adhesions and stiffness
Premature return to repetitive trauma - recurrence
Inadequate elevation - swelling and CRPS
Infection
Persistent symptoms from incomplete release

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

EXAMINER

"A 45-year-old mechanic presents with 6 months of progressive weakness in his right hand and numbness in the small finger. On examination, you note hypothenar and interosseous atrophy, positive Froment sign, positive Wartenberg sign, and numbness isolated to the palmar aspect of the small and ulnar ring fingers. The dorsal ulnar hand has normal sensation. EMG shows denervation in FDI and ADM but normal FDP to small finger. Where is the compression and what are the three zones of Guyon's canal?"

EXCEPTIONAL ANSWER

This is classic Guyon's canal syndrome (ulnar tunnel syndrome at the wrist). The key clinical clues are: (1) Pure ulnar intrinsic motor deficit with atrophy (hypothenar, interossei), (2) Sensory loss limited to palmar small and ulnar ring fingers, (3) SPARED dorsal ulnar hand sensation (dorsal cutaneous branch arises proximal to wrist), (4) NORMAL FDP to small finger on EMG (arises proximal to wrist), distinguishing from cubital tunnel. The three zones of Guyon's canal based on Shea and McClain classification are: ZONE 1 - Proximal to nerve bifurcation, contains mixed ulnar nerve (motor and sensory). Compression here causes BOTH motor weakness AND sensory loss. Common causes: ganglion cyst, ulnar artery aneurysm, fracture-dislocation. ZONE 2 - Deep motor branch only (after bifurcation). Curves around hook of hamate. Compression causes PURE MOTOR deficit (intrinsic atrophy, weak pinch, claw hand) with NORMAL sensation. This is our patient's zone. Common causes: hook of hamate fracture, ganglion, pisohamate arcade compression. ZONE 3 - Superficial sensory branch only (after bifurcation). Compression causes PURE SENSORY deficit (small finger numbness) with NORMAL motor. Least common. The bifurcation typically occurs at the level of the hook of hamate. Guyon's canal boundaries are: ROOF - palmaris brevis and volar carpal ligament, FLOOR - flexor retinaculum and pisohamate ligament, ULNAR WALL - pisiform, RADIAL WALL - hook of hamate.

VIVA SCENARIOStandard

EXAMINER

"You are performing ulnar nerve decompression at Guyon's canal and encounter a 2cm firm, slightly pulsatile mass compressing the nerve just distal to the pisiform. Describe your management approach and critical considerations."

EXCEPTIONAL ANSWER

This clinical scenario suggests either ulnar artery aneurysm or thrombosis (hypothenar hammer syndrome). The most critical immediate question is: Was an Allen test performed preoperatively? This is MANDATORY before any ulnar artery intervention and should have been documented. If NOT done preoperatively, I would perform it now under anesthesia before proceeding with arterial management. ALLEN TEST INTERPRETATION: If NORMAL (hand pinkness returns within 5 seconds when releasing radial artery alone) - Safe to ligate ulnar artery. Radial artery provides adequate collateral perfusion through palmar arches. If ABNORMAL (delayed or absent perfusion) - Ulnar artery ligation will cause hand ischemia. Need vascular surgery consultation for reconstruction. My SYSTEMATIC APPROACH: (1) Complete nerve decompression first regardless of artery status. (2) Carefully expose mass without injuring nerve. (3) Determine if thrombosed artery (firm, non-pulsatile) or aneurysm (pulsatile, dilated). (4) If Allen test NORMAL: Ligate proximal and distal to affected segment with 3-0 or 4-0 silk ties, excise diseased segment, send for histopathology to confirm thrombosis and rule out vasculitis. (5) If Allen test ABNORMAL: Options include (a) Two-stage procedure - decompress nerve now, refer vascular surgery for arterial reconstruction later, (b) Intraoperative vascular consultation for same-stage reconstruction with vein graft or bypass, (c) If aneurysm causing mass effect, may need to excise with immediate reconstruction. (6) Meticulous hemostasis critical. (7) Postoperative monitoring of perfusion (capillary refill, temperature, pulse oximetry). Most patients tolerate ulnar artery ligation well (90% if Allen normal), but 10% still develop digital ischemia despite normal Allen test, so close postoperative monitoring essential.

VIVA SCENARIOStandard

EXAMINER

"During Guyon's canal release, you need to excise a fractured hook of hamate. Describe your technique and the critical anatomical relationships you must protect."

EXCEPTIONAL ANSWER

Hook of hamate excision during Guyon's canal release requires meticulous technique due to critical adjacent structures. The most important structure to protect is the DEEP MOTOR BRANCH of the ulnar nerve, which curves immediately around the radial side of the hook. Injury causes devastating intrinsic paralysis. My SYSTEMATIC APPROACH: (1) EXPOSURE - Already decompressed Guyon's canal and identified nerve bifurcation. Deep motor branch now visible curving radially around hook. Use small Senn or love retractor to GENTLY retract deep motor branch ulnarly, protecting it throughout. (2) PROTECT FLEXOR TENDONS - FDP to ring and small fingers run immediately adjacent to hook on radial side in carpal tunnel. Use retractor to retract tendons radially away from operative field. Visualize tendons to confirm position. (3) IDENTIFY HOOK - Palpate hook with probe to define borders. Assess for mobility indicating non-union. Hook usually 1cm long, projects palmarly. (4) EXCISION TECHNIQUE - Use small rongeur (or narrow osteotome) to remove hook fragment in controlled bites. Start distally and work proximally. Remove hook flush with hamate body - palpate with probe to confirm smooth contour. (5) SMOOTH EDGES - Use small burr or rongeur to smooth any sharp edges on hamate body. Sharp edges cause continued pain and potential flexor tendon attrition. (6) IRRIGATION - Copious irrigation to remove bone debris. (7) FINAL ASSESSMENT - Palpate hamate body (should be smooth), confirm deep motor branch intact (visible, healthy appearance), confirm flexor tendons intact (visible, no laceration). The key anatomical relationships are: Deep motor branch runs RADIAL to hook (most critical), Ulnar motor artery accompanies deep branch, Flexor tendons (FDP ring/small) run RADIAL in carpal tunnel adjacent to hook, Hook projects PALMARLY from hamate body. TECHNICAL PEARLS: Use loupe magnification. Never attempt ORIF - poor healing, high complication rate. Excision has excellent outcomes.