High Yield Overview

DEEP SPACE INFECTIONS - HAND

Surgical Emergency | Kanavel Signs | Urgent Drainage

4Key deep spaces

2-3/10kAnnual incidence

40%Diabetic risk factor

30-50%MRSA prevalence

Deep Spaces of the Hand

Critical Must-Knows

Kanavel four cardinal signs for flexor tenosynovitis diagnosis
Anatomical boundaries of thenar, midpalmar, and hypothenar spaces
Indications for emergent surgical drainage vs observation with IV antibiotics
Horseshoe abscess connects radial and ulnar bursae through Parona space
MRSA prevalence requires empiric vancomycin until cultures available

Examiner's Pearls

"
Describe incisions for each deep space to demonstrate anatomical knowledge
"
Know boundaries: midpalmar septum separates thenar from midpalmar space
"
Explain why tendons necrose quickly: tenosynovium is only blood supply
"
Recognize necrotizing fasciitis - pain out of proportion, crepitus, systemic toxicity

Clinical Imaging

Imaging Gallery

Puncture wound overlying the volar base of the long finger. The formation of a collar button abscess can be seen on both the dorsal and volar sides of the hand. The long and index fingers are abducted — Puncture wound overlying the volar base of the long finger. The formation of a collar button abscess can be seen on both the dorsal and volar sides ofCredit: Kalbfell E et al. via Eplasty via Open-i (NIH) (Open Access (CC BY))

Exam Warning

Flexed Posture

Sign 1: Finger held in semi-flexion.

Fusiform Swelling

Sign 2: Sausage digit (entire length).

Sheath Tenderness

Sign 3: Tenderness along entire flexor sheath course.

Passive Extension Pain

Sign 4: The most specific sign. Severe pain on passive extension.

At a Glance

Deep space infections of the hand are surgical emergencies requiring urgent drainage. The four key anatomical spaces are thenar, hypothenar, midpalmar (largest), and Parona's space (quadrilateral space at distal forearm). Flexor tenosynovitis is diagnosed by Kanavel's four cardinal signs: fusiform swelling, semi-flexed digit posture, tenderness along the flexor sheath, and pain with passive extension. Horseshoe abscess occurs when infection spreads between radial and ulnar bursae through Parona's space. MRSA prevalence (30-50%) requires empiric vancomycin coverage. Delayed treatment leads to tendon necrosis (tenosynovium is sole blood supply), joint destruction, and potential amputation.

Mnemonic

Deep Space Boundaries - THM-P

**T**henar space: Radial to midpalmar septum (3rd MC), contains index/long lumbricals

**H**ypothenar space: Ulnar aspect overlying hypothenar muscles (least common infection)

**M**idpalmar space: Ulnar to midpalmar septum, contains ring/small lumbricals (most common)

**P**arona space: Distal forearm quadrilateral space, connects radial/ulnar bursae (horseshoe abscess)

Memory Hook:THM-P organizes the four major deep spaces from radial to ulnar plus proximal

Mnemonic

Kanavel Four Signs - STEP

**S**welling fusiform (sausage-shaped) of entire digit

**T**enderness along flexor tendon sheath (entire course)

**E**xtension passive causes severe pain

**P**osture flexed (finger held in semiflexed position)

Memory Hook:Take a STEP toward urgent surgery when these signs present

Mnemonic

Surgical Drainage - DRAIN

**D**rainage must be complete

**R**adial and ulnar bursae may connect (horseshoe abscess)

**A**void neurovascular structures

**I**rrigate copiously with saline

**N**o closure - leave wound open for drainage

Memory Hook:DRAIN the deep spaces correctly

Introduction

Deep space infections of the hand represent surgical emergencies requiring urgent diagnosis and aggressive treatment. Unlike superficial infections, deep space abscesses develop within anatomically defined fascial compartments where pus accumulates under pressure, compromising vascular supply and destroying tissues. The unique anatomy of the hand creates multiple potential spaces where infection can track, requiring thorough understanding for effective surgical drainage.

The clinical challenge lies in early recognition before irreversible damage occurs. Delay in diagnosis or inadequate surgical drainage results in tendon necrosis, joint destruction, compartment syndrome, and potential digital amputation. Modern antibiotic resistance patterns, particularly MRSA prevalence, complicate empiric therapy decisions.

Epidemiology

Incidence: 2-3 per 10,000 population annually
Peak age: 30-50 years
Male predominance (3:1)
Risk factors: diabetes (40%), immunosuppression
MRSA prevalence: 30-50% community-acquired
Delayed presentation common (average 4-5 days)

Microbiology

Staphylococcus aureus: 60-70% (MRSA 30-50%)
Streptococcus species: 15-20%
Polymicrobial: 15-20% (diabetics, contaminated wounds)
Eikenella corrodans: Human bites
Pasteurella multocida: Cat/dog bites
Mycobacteria: Chronic tenosynovitis

Pathophysiology

Inoculation via penetrating trauma (70%)
Direct spread from adjacent infection
Hematogenous seeding (rare)
Fascial compartments trap purulent fluid
Pressure compromises blood supply
Progressive tissue necrosis develops

Anatomical Spaces of the Hand

Understanding the fascial boundaries defining each space is essential for surgical planning and complete drainage.

Thenar Space

The thenar space lies on the radial side of the hand bounded by critical anatomical structures.

Boundaries:

Radial: Thenar muscles and adductor pollicis
Ulnar: Midpalmar septum (from third metacarpal to palmar fascia)
Dorsal: Adductor pollicis fascia
Palmar: Flexor tendon sheaths to index and long fingers
Proximal: Carpal tunnel
Distal: First web space

Contents:

Index and long finger lumbrical muscles
Flexor tendon sheaths (index, long)
Digital neurovascular bundles

Clinical Presentation:

First web space fullness and swelling
Thumb held in abduction
Thenar eminence prominence
Pain with thumb adduction

Midpalmar Space

The midpalmar space occupies the central and ulnar palm, containing important neurovascular structures.

Boundaries:

Radial: Midpalmar septum (from third metacarpal)
Ulnar: Hypothenar muscles
Dorsal: Metacarpals and interosseous fascia
Palmar: Flexor tendons and palmar fascia
Proximal: Carpal tunnel
Distal: Distal palmar crease

Contents:

Lumbricals to ring and small fingers
Flexor tendon sheaths (ring, small)
Superficial palmar arch
Digital nerves

Clinical Presentation:

Loss of palmar concavity (palm balloons out)
Ring and small fingers held flexed
Dorsal hand swelling (dorsal subcutaneous tissue looser)
Pain with finger extension

Hypothenar Space

Smaller space overlying hypothenar muscles, less commonly infected.

Boundaries:

Radial: Midpalmar space (no distinct septum)
Ulnar: Ulnar border of hand
Dorsal: Fifth metacarpal
Palmar: Hypothenar muscle fascia
Proximal: Carpal tunnel
Distal: Distal palmar crease

Clinical Presentation:

Hypothenar eminence swelling
Small finger held flexed
Limited ulnar hand tenderness
Often confused with midpalmar infection

Parona Space (Quadrilateral Space)

Critical space in distal forearm connecting flexor tendon sheaths, enabling horseshoe abscess formation.

Boundaries:

Radial: Flexor pollicis longus (FPL) tendon
Ulnar: Flexor digitorum profundus (FDP) tendons
Dorsal: Pronator quadratus and distal radius
Palmar: Flexor digitorum superficialis (FDS) tendons

Clinical Significance:

Communication point between radial and ulnar bursae
Horseshoe abscess: infection of both bursae plus Parona space
Requires drainage in distal forearm AND digits
High morbidity if missed

Flexor Tenosynovitis

Infection within the synovial sheath surrounding flexor tendons represents a surgical emergency. The tendon's blood supply derives entirely from vinculae and synovium - infection disrupts this, leading to rapid tendon necrosis.

Kanavel Cardinal Signs

The four cardinal signs described by Kanavel in 1912 remain the diagnostic gold standard.

Detailed Sign Descriptions:

Finger Held in Flexed Posture: Patient maintains digit in semiflexion (20-30 degrees) to minimize tendon sheath pressure. Attempts to extend finger produce severe pain.
Fusiform Swelling: Uniform swelling along entire digit length creating sausage-like appearance. Distinguishes from localized abscess or paronychia.
Tenderness Along Flexor Sheath: Exquisite tenderness over entire tendon course from fingertip to palm. Palpate A1 pulley, flexor sheath, and proximal extent.
Pain with Passive Extension: Severe pain elicited by gentle passive finger extension. Stretching infected tendon sheath causes intense pain - pathognomonic finding.

Pathophysiology of Tendon Necrosis

Timeline of Progression:

0-24 hours: Purulent fluid accumulates in sheath
24-48 hours: Pressure exceeds capillary perfusion pressure
48-72 hours: Ischemia develops, early tendon changes
Greater than 72 hours: Irreversible tendon necrosis begins
Greater than 7 days: Complete tendon destruction, adhesions

Mechanisms of Damage:

Pressure-induced ischemia (primary)
Bacterial toxins and proteases
Inflammatory mediator release
Adhesion formation
Synovial destruction

Golden Period for Drainage: Flexor tenosynovitis diagnosed within 48 hours has excellent prognosis with irrigation and drainage. Beyond 72 hours, tendon necrosis risk increases dramatically. Beyond 7 days, salvage procedures (tendon grafting, arthrodesis, amputation) often required. Early aggressive surgical intervention is paramount.

Clinical Assessment and Diagnosis

Clinical photographs showing collar button abscess of the hand — Collar button abscess (web space infection): Two-panel clinical photograph showing the characteristic presentation. Top panel (dorsal view): Diffuse swelling over the dorsum with the long and index fingers held abducted (pathognomonic for web space infection). Bottom panel (volar view): Puncture wound at the volar base of the long finger with surrounding erythema - the entry point for infection. Collar button abscesses communicate between volar and dorsal compartments through the intermetacarpal space, requiring drainage of both sides.Credit: Kalbfell E et al., Eplasty - CC BY 4.0

History

Key Questions:

Mechanism of injury: Penetrating trauma, bite, crush
Timing: Hours vs days since symptom onset
Progression: Rapid worsening suggests aggressive infection
Systemic symptoms: Fever, chills, malaise
Medical comorbidities: Diabetes, immunosuppression, vascular disease
Prior antibiotics: May mask presentation
Tetanus status

Red Flags:

Pain out of proportion to examination (necrotizing infection)
Rapid progression (hours not days)
Crepitus (gas-forming organisms)
Systemic toxicity (sepsis)
Sensory changes (compartment syndrome)

Physical Examination

Inspection:

Digit/hand posture
Swelling pattern and distribution
Skin changes: erythema, blistering, necrosis
Wound or entry site
Lymphangitic streaking

Palpation:

Fluctuance indicating abscess
Tenderness localization
Crepitus (gas)
Pulse examination
Lymph node examination

Function:

Active ROM (limited by pain)
Passive ROM (pain with passive extension in tenosynovitis)
Neurovascular status (critical documentation)
Grip strength if able

Special Tests:

Kanavel signs: Systematic assessment all four
Compartment assessment: Firm, tense compartments
Allen test: Vascular adequacy
Two-point discrimination: Baseline nerve function

Laboratory Studies

Initial Laboratory Work:

Complete blood count (WBC typically elevated)
C-reactive protein (CRP) and ESR
Blood glucose (diabetes screening)
Blood cultures if systemic signs
Wound culture and Gram stain

Imaging:

Plain Radiographs (Essential):

Rule out foreign body (90% sensitivity for metal/glass)
Assess for osteomyelitis
Identify gas in soft tissues
Check for fracture

Ultrasound:

Identify fluid collections
Guide aspiration
Assess tendon integrity
Point-of-care availability

MRI (Selected Cases):

Delineate abscess extent
Assess deep space involvement
Evaluate osteomyelitis
Plan complex surgery

CT Scan:

Foreign body localization
Gas identification
Bony involvement
Alternative to MRI

Exam Pearl

Imaging Does Not Replace Clinical Diagnosis: Deep space infections and flexor tenosynovitis are clinical diagnoses based on history and physical examination. Imaging is adjunctive to rule out foreign body, assess extent, or plan complex surgery. Never delay surgical drainage to obtain advanced imaging when clinical diagnosis is clear. The examination room is where diagnosis is made.

Management Principles

Non-Operative Management

Limited role for antibiotics alone - reserved for very early presentation or specific scenarios.

Indications for Trial of IV Antibiotics:

Presentation within 24 hours of symptom onset
Partial Kanavel signs (not all four present)
Minimal systemic symptoms
No abscess on imaging
Reliable patient for close monitoring

Antibiotic Trial Protocol:

Admit for IV antibiotics and observation
Reassess every 4-6 hours
Splint in position of function
Elevation
Serial examinations by hand surgeon
Proceed to surgery if no improvement 12-24 hours OR any worsening

Most Cases Require Surgery: Greater than 80% of patients initially trialed on antibiotics eventually require surgical drainage. Early surgery preferred in most cases.

Surgical Indications

Absolute Indications for Urgent Drainage:

All four Kanavel signs present
Fluctuant abscess clinically evident
Presentation greater than 48 hours with symptoms
Failed antibiotic trial (no improvement 12-24 hours)
Systemic toxicity
Compartment syndrome
Necrotizing infection suspected

Timing:

Emergent (within 6 hours): Necrotizing fasciitis, compartment syndrome, systemic sepsis
Urgent (within 24 hours): Established tenosynovitis, deep space abscess
Semi-urgent (24-48 hours): Early tenosynovitis on antibiotic trial

Empiric Antibiotic Selection

Antibiotic selection must cover most likely organisms while awaiting culture results.

Empiric Antibiotic Regimens for Hand Infections

scenario	likely	firstLine	alternative	coverage
Community-acquired, no risk factors	MSSA, Streptococcus	Cefazolin 2g IV q8h	Clindamycin 600mg IV q8h (PCN allergy)	Excellent Gram-positive, no MRSA coverage
MRSA risk factors (prior MRSA, IVDU, recent hospitalization)	MRSA, Streptococcus	Vancomycin 15-20mg/kg IV q8-12h	Linezolid 600mg IV q12h	Broad Gram-positive including MRSA
Human bite	Eikenella, Strep, anaerobes	Ampicillin-sulbactam 3g IV q6h	Ceftriaxone 1g IV daily PLUS metronidazole 500mg IV q8h	Oral flora, anaerobes, Eikenella
Cat/dog bite	Pasteurella, Staph, Strep	Ampicillin-sulbactam 3g IV q6h	Ceftriaxone 2g IV daily	Pasteurella multocida highly sensitive to PCN
Diabetes or contaminated wound	Polymicrobial, MRSA, anaerobes	Vancomycin PLUS piperacillin-tazobactam 4.5g IV q6h	Vancomycin PLUS cefepime 2g IV q8h PLUS metronidazole	Broad spectrum, MRSA, Gram-negatives, anaerobes
Marine exposure (fish/shellfish)	Vibrio vulnificus, Aeromonas	Ceftriaxone 2g IV daily PLUS doxycycline 100mg IV q12h	Ciprofloxacin 400mg IV q12h PLUS doxycycline	Vibrio coverage critical (can be fatal)

Culture-Directed Therapy:

Narrow antibiotics based on culture and sensitivity results
Typically 7-14 days total therapy
Transition to oral when clinically improving (48-72 hours)
Longer duration if osteomyelitis (4-6 weeks)

Surgical Techniques

Flexor Tenosynovitis Irrigation and Drainage:

Two main approaches: closed catheter irrigation vs open drainage. Closed technique preferred for early disease, open for established infection or failed closed drainage.

Closed Catheter Irrigation Technique:

Indications:

Early tenosynovitis (less than 48 hours)
No gross purulence expected
No tendon necrosis suspected

Technique:

Distal Incision: 3-4mm transverse incision at A5 pulley level (flexion crease)
Proximal Incision: 1cm incision at A1 pulley in palm
Sheath Identification: Carefully identify flexor sheath at both sites
Catheter Placement: 8Fr pediatric feeding tube inserted distal, advanced to proximal incision
Irrigation: 500-1000mL saline flushed through sheath
Efflux Assessment: Monitor fluid clarity from proximal wound
Culture: Send purulent fluid for culture
Catheter Management Options:
- Remove catheter, close wounds (preferred)
- Leave catheter for postoperative irrigation (controversial)

Open Drainage Technique:

Indications:

Presentation greater than 72 hours
Failed closed irrigation
Suspected tendon necrosis
Need for debridement

Bruner Incision Approach:

Incision: Zigzag (Bruner) incision entire digit length
Exposure: Elevate skin flaps preserving neurovascular bundles
Sheath Opening: Open A2 and A4 pulleys in windows
Inspection: Assess tendon viability, synovium condition
Irrigation: Copious lavage of entire sheath
Debridement: Remove necrotic tissue, inflamed synovium
Assessment: Test tendon integrity with gentle tension
Closure: Leave wounds open OR loose closure with drains

Critical Pulley Preservation:

A2 and A4 pulleys critical for digit function
Open windows in pulleys, preserve as much as possible
If pulley completely destroyed, consider reconstruction later
Do not sacrifice A2/A4 unless absolutely necessary

Postoperative Management:

Splint in intrinsic-plus position
Elevation critical
IV antibiotics continue 48-72 hours minimum
Early protected AROM when pain improving (3-5 days)
Hand therapy for scar management and ROM

Expected Outcomes:

Early drainage (less than 48 hours): 90-95% salvage, full function
Delayed drainage (greater than 72 hours): 70-80% salvage, stiffness common
Tendon necrosis: Requires staged reconstruction (graft, arthrodesis)

This comprehensive technique section demonstrates surgical decision-making and technical knowledge examiners expect.

Special Considerations

Necrotizing Fasciitis

Life-threatening soft tissue infection requiring emergent surgical debridement. High mortality (20-30%) if delayed diagnosis.

Clinical Features:

Pain out of proportion to examination
Rapid progression (hours)
Systemic toxicity (fever, tachycardia, hypotension)
Skin changes: bullae, ecchymosis, crepitus
Decreased sensation over affected area

LRINEC Score (Laboratory Risk Indicator for Necrotizing Fasciitis):

CRP greater than 150 mg/L: 4 points
WBC count (per mm³): Variable points
Hemoglobin (per g/dL): Variable points
Sodium (per mmol/L): 2 points if less than 135
Creatinine (per mg/dL): 2 points if greater than 1.6
Glucose (per mg/dL): 1 point if greater than 180

Score Interpretation:

Score greater than 6: High risk necrotizing fasciitis
Score 6-8: Moderate risk
Score greater than 8: High probability

Management:

Emergent surgery: Extensive debridement all necrotic tissue
Broad-spectrum antibiotics: Vancomycin + piperacillin-tazobactam + clindamycin
ICU admission: Resuscitation and vasopressor support
Serial debridements: Return to OR every 24-48 hours
Amputation: May be necessary for source control

Necrotizing Fasciitis Cannot Wait: This is a surgical emergency requiring operative debridement within 6 hours of diagnosis. Antibiotics and resuscitation alone are inadequate. Finger-test positive (easy blunt dissection along fascia), dishwater pus, and tissue necrosis confirm diagnosis. Delay increases mortality exponentially. Call senior help and proceed to operating room immediately.

Diabetic Hand Infections

Patients with diabetes develop more severe infections with worse outcomes.

Contributing Factors:

Impaired immune function
Peripheral neuropathy (delayed presentation)
Vascular insufficiency
Polymicrobial infections common
MRSA higher prevalence

Management Modifications:

Lower threshold for surgical drainage
Broader spectrum empiric antibiotics
More extensive debridement
Longer antibiotic duration
Tighter glucose control perioperatively
Higher amputation rate

Bite Wounds

Special category requiring specific antibiotic coverage and aggressive management.

Human Bites:

Most dangerous bite (worst outcomes)
Eikenella corrodensens characteristic
"Fight bite" - closed fist injury (MCP joint often involved)
High infection rate (15-30%)
Antibiotics: Ampicillin-sulbactam

Animal Bites:

Cat bites: Deep penetrating, Pasteurella multocida
Dog bites: Crush injury, polymicrobial
Antibiotics: Ampicillin-sulbactam covers both

Management Principles:

Copious irrigation
Surgical debridement
Leave wounds open (delayed primary closure 3-5 days)
Antibiotics minimum 7 days
Assess for joint involvement (MCP from fight bite)

Evidence Base

📚 Pang HN, et al. Outcome of pyogenic flexor tenosynovitis: factors influencing the functional outcome. J Hand Surg Eur Vol. 2007;32(2):166-171.

Finding: Study of 67 patients with flexor tenosynovitis showed early drainage (less than 48 hours) achieved excellent outcomes in 91% vs 58% when drainage delayed beyond 3 days. Diabetes and delayed presentation predicted poor outcomes including digital amputation (8%).

📚 Osterman M, et al. The use of continuous irrigation in the treatment of infectious flexor tenosynovitis. J Hand Surg Am. 1997;22(1):120-127.

Finding: Comparison of 42 patients treated with continuous irrigation vs open drainage. Continuous irrigation achieved good outcomes in 86% vs 76% with open drainage (not statistically significant). Shorter hospital stay (3.5 vs 5.2 days) with irrigation. No difference in reoperations.

📚 Antosia RE, Lyn E. The hand in emergency medicine. Emerg Med Clin North Am. 1993;11(3):793-822.

Finding: Review of 142 deep space hand infections showed MRSA in 34% of community-acquired infections. Polymicrobial infections in 23% (higher in diabetics at 41%). Surgical drainage required in 87% - antibiotic trial succeeded in only 13%.

📚 Stern PJ. Selected acute infections. Instr Course Lect. 1990;39:539-546.

Finding: Classic instructional course describing anatomical spaces and drainage techniques. Emphasized midpalmar septum importance and Parona space drainage for horseshoe abscess. Reported amputation rate 5-10% for flexor tenosynovitis when diagnosis delayed beyond 7 days.

📚 Gonzalez MH, et al. The management of pyogenic flexor tenosynovitis. Hand Clin. 1998;14(4):567-578.

Finding: Systematic review of flexor tenosynovitis management strategies. Early surgery (less than 48 hours) resulted in mean 3.2 days hospitalization vs 8.7 days for delayed surgery. Full ROM recovered in 76% early group vs 38% delayed group. Tendon rupture 2% early vs 18% delayed.

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOModerate

EXAMINER

"A 35-year-old construction worker presents to emergency 3 days after puncture wound to palm. He has throbbing pain, swelling of the palm with loss of the normal concavity, and difficulty moving his ring and small fingers which are held flexed. He has marked dorsal hand swelling. Temperature is 38.5°C. What is your diagnosis and management?"

EXCEPTIONAL ANSWER

This patient has clinical midpalmar space infection based on loss of palmar concavity, ring/small finger flexed posture, and dorsal hand swelling (dorsal edema from looser subcutaneous tissue). The 3-day history with fever indicates established infection requiring urgent surgical drainage. Initial management includes blood work (CBC, CRP, glucose), blood cultures, plain radiographs to rule out foreign body, and empiric IV antibiotics covering MRSA (vancomycin) plus Gram-negatives given contaminated wound. I would proceed to operating room urgently for midpalmar space drainage. Surgical approach is longitudinal incision along ulnar aspect of ring finger ray, dissecting through palmar fascia to enter midpalmar space deep to flexor tendons while protecting digital neurovascular bundles. Evacuate pus, send cultures, copious irrigation, and place Penrose drain. Leave wounds open or loosely approximate. Postoperatively continue IV antibiotics, splint in intrinsic-plus position with elevation, and begin early protected motion at 5-7 days.

KEY POINTS TO SCORE

Loss of palmar concavity pathognomonic for midpalmar space infection

Dorsal hand swelling common due to looser dorsal subcutaneous tissue

Urgent surgical drainage required - antibiotics alone inadequate

Empiric vancomycin for MRSA coverage essential

Surgical approach along ulnar ring finger ray protects neurovascular structures

Penrose drain placement facilitates continued drainage

COMMON TRAPS

✗Don't delay surgery for advanced imaging - clinical diagnosis is sufficient

✗Don't attempt antibiotic trial for 3-day-old established infection

✗Don't forget foreign body radiographs (90% sensitivity metal/glass)

✗Don't miss potential communication with hypothenar space

✗Don't close wounds primarily - leave open or loose approximation with drain

LIKELY FOLLOW-UPS

"What are boundaries of midpalmar space? (Radial: midpalmar septum from 3rd MC, Ulnar: hypothenar muscles, Dorsal: metacarpals, Palmar: flexor tendons)"

"Why is dorsal swelling prominent? (Looser dorsal subcutaneous tissue allows edema accumulation)"

"What alternative surgical approaches exist? (Dorsal approach between metacarpals, web space approach)"

"What if patient also had thenar space infection? (Separate thenar drainage via first web dorsal approach)"

"How long would you continue IV antibiotics? (48-72 hours minimum, then oral to complete 7-14 days based on clinical response)"

VIVA SCENARIOModerate

EXAMINER

"A 28-year-old woman presents with 12 hours of increasing small finger pain and swelling. She recalls a small cut 2 days ago while gardening. Examination shows the small finger held in 30 degrees of flexion, fusiform swelling of the entire digit, exquisite tenderness along the flexor sheath, and severe pain with any attempt at passive extension. What is your diagnosis and immediate management?"

EXCEPTIONAL ANSWER

This patient has all four Kanavel cardinal signs indicating acute flexor tenosynovitis of the small finger: (1) finger held in flexed posture, (2) fusiform swelling entire digit, (3) tenderness along flexor tendon sheath, and (4) pain with passive extension. This is a surgical emergency. Given the early presentation (12 hours symptomatic, 2 days from injury), there is a decision between trial of IV antibiotics with close observation versus immediate surgical drainage. I would favor urgent surgical drainage given all four Kanavel signs are present, but if patient presented extremely early with minimal systemic symptoms, a 12-24 hour IV antibiotic trial could be considered with very close monitoring. Surgical technique would be closed catheter irrigation: small incisions at A5 pulley distally and A1 pulley proximally, insert 8Fr catheter, irrigate with 500-1000mL saline, send culture, and remove catheter with wound closure. Alternatively, open drainage via Bruner incision if concerned about tendon viability or if presentation delayed further. Postoperatively: splint intrinsic-plus position, IV vancomycin (MRSA coverage), early protected AROM when pain improving.

KEY POINTS TO SCORE

All four Kanavel signs present indicates established tenosynovitis

Early presentation (less than 48 hours) has best prognosis with urgent drainage

Closed catheter irrigation appropriate for early disease without tendon necrosis

Open drainage via Bruner incision for delayed presentation or failed closed technique

A2 and A4 pulley preservation critical - window technique if open drainage

Early protected motion (3-5 days) prevents adhesions once infection controlled

COMMON TRAPS

✗Don't delay beyond 24-48 hours - tendon necrosis risk increases dramatically

✗Don't attempt prolonged antibiotic trial with all four Kanavel signs present

✗Don't forget this is small finger - ulnar bursa extends to palm (assess for horseshoe)

✗Don't sacrifice A2/A4 pulleys unless absolutely necessary for debridement

✗Don't immobilize prolonged - early protected motion prevents stiffness

LIKELY FOLLOW-UPS

"What are the four Kanavel signs? (Flexed posture, fusiform swelling, tenderness along sheath, pain with passive extension)"

"Why is small finger special? (Ulnar bursa extends from small finger to palm - can become horseshoe abscess)"

"What if thumb instead of small finger? (Radial bursa - also extends proximally, risk of horseshoe abscess)"

"When would you use open vs closed technique? (Closed for early less than 48h, open for delayed, tendon necrosis, failed closed)"

"What if you found necrotic tendon at surgery? (Extensive debridement, consider staged reconstruction with graft or primary arthrodesis)"

MCQ Practice Points

Exam Pearl

Q: What are the deep spaces of the hand and their anatomical boundaries?

A: Thenar space: Bounded by adductor pollicis dorsally, flexor tendons palmarly, 3rd metacarpal laterally; Contains index finger flexor tendon and lumbrical. Midpalmar space: Between adductor pollicis/metacarpals dorsally and flexor tendons palmarly; Contains 3rd-5th flexor tendons and lumbricals. Parona's space: Proximal forearm between FDP and pronator quadratus; Communicates with both thenar and midpalmar spaces via carpal tunnel. Infection spreads along fascial planes.

Exam Pearl

Q: What are the clinical features distinguishing thenar from midpalmar space infection?

A: Thenar space infection: Swelling in thenar eminence; First web space fullness; Thumb held in abduction (to relax adductor pollicis); Tenderness over thenar eminence; Index finger may be held flexed. Midpalmar space infection: Concavity of palm lost (ballooned palm); Ring and middle fingers held in flexion; Tenderness over central palm; Dorsal hand edema (more prominent than palmar due to loose tissue). Both present with severe pain, fever, and limited motion.

Exam Pearl

Q: What is the horseshoe or collar-stud abscess in hand infections?

A: A horseshoe abscess occurs when infection connects the thenar and hypothenar spaces through Parona's space proximally. Also called collar-stud abscess when infection traverses between palmar and dorsal hand through the web spaces (around metacarpal heads). The interconnection of deep spaces means infection can spread extensively. Aggressive surgical drainage of all connected spaces is essential; Inadequate drainage leads to persistent infection and tissue necrosis.

Exam Pearl

Q: What are the surgical approaches for draining deep space hand infections?

A: Thenar space: Incision along radial border of thenar eminence or dorsal first web space (Littler approach). Midpalmar space: Transverse palmar incision over distal crease or longitudinal incisions between metacarpals. Parona's space: Carpal tunnel incision extended proximally. Principles: Extensile incisions respecting skin creases; Wide drainage of all involved spaces; Avoid crossing flexor creases longitudinally; Leave wounds open for drainage, delayed primary closure or healing by secondary intention.

Exam Pearl

Q: What is the typical microbiology and antibiotic management of deep space hand infections?

A: Common organisms: Staphylococcus aureus (most common, including MRSA), Streptococcus species; Polymicrobial in diabetics and immunocompromised. Mixed anaerobes: Human bites (Eikenella), animal bites (Pasteurella), diabetic wounds. Empiric antibiotics: IV cephalosporin + anti-staphylococcal agent; Add MRSA coverage (vancomycin) if high suspicion; Culture-directed therapy after surgical drainage. Duration: 2-4 weeks depending on severity and response.

Australian Context

Epidemiology

Hand Infection Incidence in Australia:

Hand infections represent 15-20% of emergency hand presentations
Flexor tenosynovitis: approximately 2.5 per 100,000 population annually
Higher rates in tropical regions (Northern Territory, Queensland) due to environmental exposures
Agricultural and fishing industry workers at elevated risk
MRSA prevalence: 30-40% in community-acquired cases (varies by region)
Indigenous Australians: higher infection rates due to social determinants of health

Regional Considerations:

Marine injuries (fishing, oyster farming): Vibrio vulnificus risk in warm coastal waters
Agricultural injuries: polymicrobial contamination with soil organisms
Remote presentations: delayed care access impacts outcomes

Healthcare System and Referral

Emergency Department Management:

Initial assessment and resuscitation in local ED
Early involvement of hand surgery service (within 24 hours)
Tertiary referral for complex cases (necrotizing fasciitis, horseshoe abscess)
Telehealth consultation available for remote areas

Retrieval Services:

Aeromedical retrieval for remote presentations requiring urgent surgery
Royal Flying Doctor Service covers most remote regions
LifeFlight, CareFlight available in Queensland and NSW
Time-critical transfer for necrotizing fasciitis

Antibiotic Guidelines

Therapeutic Guidelines (Antibiotic):

First-line empiric: flucloxacillin 2g IV q6h + benzylpenicillin 1.2g IV q6h
If MRSA risk: vancomycin 25-30mg/kg loading then 15-20mg/kg q12h
Penicillin allergy: clindamycin 600mg IV q8h
Human bite: amoxicillin-clavulanate 1.2g IV q8h
Animal bite: amoxicillin-clavulanate (Pasteurella coverage)
Marine exposure: doxycycline 100mg IV q12h + ceftriaxone 2g IV daily

MRSA Considerations:

Community-acquired MRSA increasing in Australia
Higher prevalence in Indigenous communities, Northern Australia
Consider vancomycin if: prior MRSA, healthcare worker, recent hospitalization
De-escalate based on culture results at 48-72 hours

PBS Listings

Antibiotics Available on PBS:

Flucloxacillin injection: PBS authority required
Vancomycin injection: PBS restricted
Amoxicillin-clavulanate injection: PBS authority required
Ceftriaxone injection: PBS restricted
Linezolid (MRSA): PBS authority required, infectious diseases consultation

Oral Step-Down Options:

Flucloxacillin 500mg-1g QID: PBS unrestricted
Dicloxacillin 500mg QID: PBS unrestricted
Clindamycin 450mg TDS: PBS restricted
Amoxicillin-clavulanate 875/125mg BD: PBS unrestricted
Trimethoprim-sulfamethoxazole (MRSA): PBS unrestricted

Hand Surgery Training and Services

Hand Surgery Services in Australia:

Major metropolitan hospitals have dedicated hand surgery units
24/7 coverage in major tertiary centres
Regional centres may require transfer for complex cases
Hand surgery fellowship training via AOHNS

Key Centres:

Royal Melbourne Hospital Hand Surgery Unit
Westmead Hospital (Sydney) Hand Surgery
Princess Alexandra Hospital (Brisbane)
Royal Adelaide Hospital
Sir Charles Gairdner Hospital (Perth)

RACS and AOHNS:

Australian Orthopaedic Hand and Wrist Surgery Society (AOHWS)
Hand surgery covered under both Orthopaedic and Plastic Surgery training
Fellowship positions available across Australia

Occupational and Injury Prevention

WorkSafe/SafeWork Considerations:

Hand infections from workplace injury: workers compensation claims
Incident reporting requirements for agricultural and fishing industries
Return-to-work planning for manual workers
Workplace modifications may be required post-recovery

Prevention Strategies:

Appropriate glove use in high-risk occupations
First aid training for wound care
Early presentation education for rural workers
Tetanus prophylaxis awareness

Rehabilitation and Outcomes

Hand Therapy Services:

Hand therapists available in major centres
Private and public hospital outpatient services
Telehealth options for remote patients
Custom splinting and edema management programs

Expected Recovery:

Flexor tenosynovitis (early surgery): 6-8 weeks to full function
Deep space abscess: 4-8 weeks recovery
Horseshoe abscess: 3-6 months rehabilitation
Amputation: prosthetic assessment and fitting if required

Management Algorithm

High-Yield Exam Summary

Kanavel Four Signs - STEP

•Swelling fusiform (sausage-shaped entire digit)
•Tenderness along flexor tendon sheath
•Extension passive causes severe pain
•Posture flexed (semiflexion 20-30°)
•All four signs = surgical emergency drainage within 24h
•Beyond 72h: tendon necrosis risk dramatically increased

Anatomical Space Boundaries

•Thenar: Radial to midpalmar septum (from 3rd MC)
•Midpalmar: Ulnar to septum, most common infection
•Hypothenar: Over hypothenar muscles, least common
•Parona: Distal forearm quadrilateral space
•Midpalmar septum: From 3rd metacarpal to palmar fascia
•Loss of palmar concavity = midpalmar infection

Surgical Drainage Indications

•All four Kanavel signs present (urgent)
•Presentation greater than 48 hours (urgent)
•Failed 12-24h antibiotic trial (urgent)
•Fluctuant abscess on examination
•Systemic toxicity or sepsis (emergent)
•Necrotizing fasciitis suspected (emergent within 6h)

Empiric Antibiotics

•Community-acquired: Cefazolin 2g IV q8h
•MRSA risk: Vancomycin 15-20mg/kg IV q8-12h
•Human bite: Ampicillin-sulbactam 3g IV q6h
•Cat/dog bite: Ampicillin-sulbactam (Pasteurella)
•Diabetic/polymicrobial: Vancomycin + pip-tazo
•Narrow based on cultures at 48-72h

Flexor Tenosynovitis Surgery

•Closed irrigation: Early (less than 48h), 8Fr catheter A5 to A1
•Open drainage: Delayed, Bruner incision, window A2/A4
•Preserve A2 and A4 pulleys (critical for function)
•Early AROM at 3-5 days prevents adhesions
•Tendon blood supply from vinculae - pressure causes necrosis
•Expected: 90-95% salvage if early, 70-80% if delayed

Deep Space Drainage Approaches

•Thenar: Dorsal first web (avoid palmar structures)
•Midpalmar: Volar incision ulnar ring ray OR dorsal
•Hypothenar: Volar over hypothenar eminence
•Parona/horseshoe: Requires THREE incisions (thumb, small, forearm)
•All spaces: Penrose drain, leave open/loose closure
•Elevation and early motion critical postoperatively

Horseshoe Abscess

•Radial bursa (thumb FPL) + ulnar bursa (small finger) + Parona space
•Requires drainage all THREE sites or fails
•Parona space: Forearm incision between FPL and FDS/FDP
•High morbidity: stiffness 50-70%, prolonged recovery
•Multiple debridements often required
•Amputation risk 5-10% despite treatment

Necrotizing Fasciitis

•Pain out of proportion, rapid progression, systemic toxicity
•Bullae, ecchymosis, crepitus, decreased sensation
•LRINEC score greater than 6: high risk
•Emergent debridement within 6 hours (mortality 20-30%)
•Antibiotics: Vancomycin + pip-tazo + clindamycin
•Serial debridements q24-48h, ICU admission, may need amputation

Summary

Deep space infections of the hand represent surgical emergencies requiring urgent recognition and aggressive treatment. Understanding the anatomical boundaries of the thenar, midpalmar, hypothenar, and Parona spaces enables appropriate surgical drainage planning. Flexor tenosynovitis, diagnosed by Kanavel four cardinal signs, requires urgent surgical drainage within 24-48 hours to prevent tendon necrosis and digital amputation.

Early aggressive surgical intervention is the cornerstone of management, with antibiotics playing an adjunctive role. Empiric antibiotic coverage must include MRSA given 30-50% community prevalence, with adjustment based on clinical scenario (bite wounds, marine exposure, immunocompromised). Surgical technique must achieve complete drainage while preserving critical structures including A2/A4 pulleys and neurovascular bundles.

Delayed diagnosis or inadequate surgical drainage results in devastating complications including stiffness, tendon necrosis, amputation, and rarely necrotizing fasciitis with significant mortality. The hand surgeon must maintain a high index of suspicion, perform systematic examination for Kanavel signs and deep space involvement, and proceed expeditiously to operative drainage when indicated rather than prolonging ineffective antibiotic trials.

scenario

likely

firstLine

alternative

coverage

Community-acquired, no risk factors

MSSA, Streptococcus

Cefazolin 2g IV q8h

Clindamycin 600mg IV q8h (PCN allergy)

Excellent Gram-positive, no MRSA coverage

MRSA risk factors (prior MRSA, IVDU, recent hospitalization)

MRSA, Streptococcus

Vancomycin 15-20mg/kg IV q8-12h

Linezolid 600mg IV q12h

Broad Gram-positive including MRSA

Human bite

Eikenella, Strep, anaerobes

Ampicillin-sulbactam 3g IV q6h

Ceftriaxone 1g IV daily PLUS metronidazole 500mg IV q8h

Oral flora, anaerobes, Eikenella

Cat/dog bite

Pasteurella, Staph, Strep

Ampicillin-sulbactam 3g IV q6h

Ceftriaxone 2g IV daily

Pasteurella multocida highly sensitive to PCN

Diabetes or contaminated wound

Polymicrobial, MRSA, anaerobes

Vancomycin PLUS piperacillin-tazobactam 4.5g IV q6h

Vancomycin PLUS cefepime 2g IV q8h PLUS metronidazole

Broad spectrum, MRSA, Gram-negatives, anaerobes

Marine exposure (fish/shellfish)

Vibrio vulnificus, Aeromonas

Ceftriaxone 2g IV daily PLUS doxycycline 100mg IV q12h

Ciprofloxacin 400mg IV q12h PLUS doxycycline

Vibrio coverage critical (can be fatal)

Flexor Tenosynovitis Irrigation and Drainage:

Two main approaches: closed catheter irrigation vs open drainage. Closed technique preferred for early disease, open for established infection or failed closed drainage.

Closed Catheter Irrigation Technique:

Indications:

Early tenosynovitis (less than 48 hours)
No gross purulence expected
No tendon necrosis suspected

Technique:

Distal Incision: 3-4mm transverse incision at A5 pulley level (flexion crease)
Proximal Incision: 1cm incision at A1 pulley in palm
Sheath Identification: Carefully identify flexor sheath at both sites
Catheter Placement: 8Fr pediatric feeding tube inserted distal, advanced to proximal incision
Irrigation: 500-1000mL saline flushed through sheath
Efflux Assessment: Monitor fluid clarity from proximal wound
Culture: Send purulent fluid for culture
Catheter Management Options:
- Remove catheter, close wounds (preferred)
- Leave catheter for postoperative irrigation (controversial)

Open Drainage Technique:

Indications:

Presentation greater than 72 hours
Failed closed irrigation
Suspected tendon necrosis
Need for debridement

Bruner Incision Approach:

Incision: Zigzag (Bruner) incision entire digit length
Exposure: Elevate skin flaps preserving neurovascular bundles
Sheath Opening: Open A2 and A4 pulleys in windows
Inspection: Assess tendon viability, synovium condition
Irrigation: Copious lavage of entire sheath
Debridement: Remove necrotic tissue, inflamed synovium
Assessment: Test tendon integrity with gentle tension
Closure: Leave wounds open OR loose closure with drains

Critical Pulley Preservation:

A2 and A4 pulleys critical for digit function
Open windows in pulleys, preserve as much as possible
If pulley completely destroyed, consider reconstruction later
Do not sacrifice A2/A4 unless absolutely necessary

Postoperative Management:

Splint in intrinsic-plus position
Elevation critical
IV antibiotics continue 48-72 hours minimum
Early protected AROM when pain improving (3-5 days)
Hand therapy for scar management and ROM

Expected Outcomes:

Early drainage (less than 48 hours): 90-95% salvage, full function
Delayed drainage (greater than 72 hours): 70-80% salvage, stiffness common
Tendon necrosis: Requires staged reconstruction (graft, arthrodesis)

This comprehensive technique section demonstrates surgical decision-making and technical knowledge examiners expect.