High-yield overview

Urgent surgical drainage guided by infection type. Flexor tenosynovitis requires emergency washout. Deep spaces need anatomical approach. Distinguish herpetic whitlow from felon — do NOT incise viral lesions. | intermediate

Surgical Imaging

Kanavel cardinal signs of pyogenic flexor tenosynovitis — Kanavel’s four cardinal signs of pyogenic flexor tenosynovitis: fusiform (sausage) swelling, finger held in slight flexion, tenderness along the flexor sheath, and pain on passive extension (most sensitive).Credit: AI-generated medical image · OrthoVellum

Flexor sheaths and deep hand spaces with drainage incisions — Flexor tendon sheaths, the radial and ulnar bursae and the thenar and midpalmar deep spaces of the palm. Communication of the radial and ulnar bursae lets pus track from thumb to little finger as a horseshoe abscess.Credit: AI-generated medical image · OrthoVellum

Felon and paronychia drainage technique — A felon: a tensely swollen, erythematous fingertip pulp with a pointing abscess. Drain through a high lateral (mid-axial) incision on the non-contact border — avoiding fish-mouth and transverse incisions, protecting the neurovascular bundle, and never crossing flexion creases.Credit: AI-generated medical image · OrthoVellum

Critical Exam Concepts — Hand Infections

Kanavel's 4 Signs

Classic FTS Diagnosis — Exam Favourite

Fusiform (uniform) swelling of entire digit
Flexed resting posture (semiflexed)
Pain on passive extension (most sensitive/specific)
Tenderness along flexor sheath (volar)

All 4 = emergency drainage within 6 hours

Herpetic Whitlow vs Felon

DO NOT CONFUSE — Incision is catastrophic for HSV

Herpetic whitlow: HSV-1/2, grouped vesicles, healthcare workers/children, viral prodrome, self-limiting 3 weeks

Felon: bacterial, tense pulp, no vesicles, progressive pain, requires I&D

If in doubt: Tzanck smear / PCR. NEVER incise suspected herpetic whitlow

Flexor Sheath Irrigation vs Open Drainage

Two techniques — know both for viva

Closed continuous irrigation (Neviaser): proximal + distal windows, catheter irrigation 24-48hr, preserves sheath

Open drainage (Bunnell): volar Brunner or mid-lateral incisions, direct visualisation, reserved for late/severe cases

Early presentation (<48hr): closed irrigation preferred. Late/severe: open drainage

Human Bite — Eikenella

Fight bite = Eikenella corrodens emergency

MCPJ laceration from opponent's tooth — examine in EXTENSION (injury deeper than it looks in flexion)

Organism: Eikenella corrodens + anaerobes — resistant to first-generation cephalosporins

Treatment: IV amoxicillin-clavulanate, wound exploration, joint washout if MCP involved

Thenar vs Midpalmar Space

Deep space anatomy critical for surgical approach

Thenar space: radial palm, deep to thenar muscles, bounded by 3rd metacarpal (medial) and oblique head of AdP (floor)

Midpalmar space: ulnar palm, beneath flexor tendons to ring/small fingers, bordered by 3rd metacarpal (radial) and hypothenar fascia (ulnar)

Thenar infection: dorsal thumb web approach. Midpalmar: transverse volar crease incision

Post-op FTS Outcomes

Counsel patients pre-operatively

Even with prompt drainage (within 24hr): 20-30% residual stiffness

Delayed drainage (>48hr): up to 50-70% poor functional outcomes, risk tendon necrosis

May require staged tenolysis at 3-6 months if significant adhesions develop

Diabetes, immunosuppression, IV drug use = significantly worse prognosis

Mnemonic

KANAVELKANAVEL — 4 Signs of Flexor Tenosynovitis

Hook:In the exam, if asked about FTS management, state all 4 Kanavel signs BEFORE discussing treatment. Examiners expect systematic identification of the condition before proceeding to surgical planning.

Mnemonic

FISTFIST — Organisms by Mechanism of Injury

Hook:Add Vibrio/Aeromonas for aquatic injuries (fish tank, water exposure) — requires ciprofloxacin. S. aureus remains the commonest organism overall across all hand infections.

Surgical Indications by Infection Type

Flexor Tenosynovitis — Emergency

Absolute indications for surgical drainage:

All 4 Kanavel signs present → immediate OR
Any 3 Kanavel signs present with systemic sepsis → emergency OR
Failed 12-24 hour IV antibiotics trial (Neviaser approach)
Immunocompromised patient with any 2 Kanavel signs

Trial of IV antibiotics (controversial, select cases only):

Very early presentation (<24 hours), mild, 2-3 signs only
Reliable patient, close observation, admitted
Must proceed to OR if no improvement within 12-24 hours

Deep Space Infections

Fluctuant swelling with systemic signs → surgical drainage
Failure of IV antibiotics at 24-48 hours
Thenar space: swelling, limited thumb abduction, pain in first web space
Midpalmar space: loss of normal palmar concavity, pain on middle/ring finger movement

Paronychia

Simple acute: I&D when fluctuant; subungual spread requires partial nail plate removal
Chronic paronychia: only surgical (nail fold marsupialisation) after 3+ months failed conservative treatment — underlying cause is often Candida

Felon

All felons with tense pulp require surgical drainage — untreated leads to vascular compromise and osteomyelitis of distal phalanx

Web Space (Collar-Stud) Abscess

Both dorsal and palmar components require drainage — collar-stud abscess tracks through web space; draining only one component leads to recurrence

Pang Prognostic Classification (Surgical Decision-Making)

The Pang classification (2007, 75 patients) stratifies pyogenic flexor tenosynovitis by intra-operative findings and predicts both amputation risk and recovery of total active motion (TAM):

Group I — no subcutaneous purulence, no digital ischaemia: best prognosis, 0% amputation, mean 80% TAM
Group II — subcutaneous purulence present but no ischaemia: 8% amputation, mean 72% TAM
Group III — extensive subcutaneous purulence AND digital ischaemia: worst prognosis, 59% amputation, mean 49% TAM

Five independent risk factors for poor outcome: age over 43 years; diabetes, peripheral vascular disease or renal failure; subcutaneous purulence; digital ischaemia; and polymicrobial infection.

Evidence Base (Verified)

Kanavel's original description (1912) remains the clinical gold standard — the four cardinal signs are still used to guide diagnosis and emergency drainage
Neviaser (1978, PMID 556478): original closed continuous catheter irrigation series — 18 of 20 patients regained complete motion by one week, establishing closed irrigation as a sheath-preserving alternative to open drainage
Pang et al. (2007, PMID 17671013): prognostic classification linking intra-operative purulence/ischaemia to amputation and TAM
McDonald et al. (2011, PMID 21816297) and Osterman et al. (2014, PMID 25070032): contemporary reviews emphasising prompt diagnosis, empirical cover for MRSA, and that even healthy patients retain some residual stiffness after sheath infection

Clinical Decision Scenarios

Use these scenarios to practise clinical reasoning and management decisions

CLINICAL SCENARIOStandard

CLINICAL PROMPT

"A 28-year-old man presents with a 2-day history of a swollen, painful right ring finger. On examination the entire digit is uniformly swollen, held in a flexed posture, and exquisitely tender on the volar surface. He is afebrile. Describe your assessment and management."

PRACTICAL APPROACH

This presentation is highly suspicious for flexor tenosynovitis based on Kanavel's four signs. I would systematically confirm all four: first, fusiform or uniform swelling of the entire digit — present; second, semiflexed resting posture of the digit — present; third, pain on passive extension of the digit — I would gently assess; fourth, tenderness along the entire volar flexor sheath from the A1 pulley to the DIP joint. With 3-4 signs, this is a surgical emergency requiring prompt drainage. I would admit the patient immediately, commence IV antibiotics (flucloxacillin or cefazolin), take a history of mechanism — biting, puncture wound — and arrange urgent theatre within 6 hours. Imaging (X-ray) to exclude foreign body and early osteomyelitis. Surgical plan: closed catheter irrigation via proximal window at A1 pulley level and distal window at DIP crease, irrigating 500-1000mL saline until effluent clear, with continuous post-operative infusion at 10mL/hr × 24-48 hours. Open Bunnell drainage reserved if this fails or presentation is beyond 48 hours. I would counsel the patient that even with prompt drainage, 20-30% experience residual stiffness.

CLINICAL SCENARIOStandard

CLINICAL PROMPT

"A 45-year-old labourer presents with 3 days of increasing pain and swelling in the palm. Examination shows loss of the normal palmar concavity, severe pain on attempted movement of the ring and small fingers, and a mildly raised temperature. The thumb and index are unaffected. Where is the infection and how do you drain it?"

PRACTICAL APPROACH

The clinical presentation with loss of palmar concavity and pain specifically on ring and small finger movement points to a midpalmar space infection — this is the ulnar deep space of the palm situated beneath the long flexor tendons to the ring and small fingers, bounded medially by the hypothenar fascia and radially by the third metacarpal. The thenar space would be indicated by first web space swelling and restricted thumb abduction. My drainage approach for midpalmar space infection would be under GA or regional block with tourniquet. I would use a transverse incision at the distal palmar crease, placed between the ring and small finger rays. Deep dissection proceeds carefully in the interval between the flexor tendons, taking care to avoid the common digital nerves and branches of the superficial palmar arch. I enter the midpalmar space bluntly, drain and send pus for culture, irrigate with saline, and place a loose drain. I leave the wound loosely packed with ribbon gauze and return for second look at 48 hours. Post-operatively, IV antibiotics, elevation, and early digit range of motion.

CLINICAL SCENARIOStandard

CLINICAL PROMPT

"A 32-year-old nurse presents with 5 days of pain, swelling, and erythema around the nail fold of her right index finger. There are small grouped vesicular lesions visible. She thinks she recently treated a patient with oral herpes. How do you manage her?"

PRACTICAL APPROACH

This presentation is highly suspicious for herpetic whitlow — HSV infection of the fingertip in a healthcare worker with likely occupational exposure. The critical finding is grouped vesicles, which distinguish herpetic whitlow from a bacterial felon. This is absolutely vital because the management is the complete opposite: I would NOT incise this lesion. Incision of herpetic whitlow risks secondary bacterial superinfection, viral spread, severe complications, and prolonged morbidity. Management is antiviral therapy — aciclovir 400mg three times daily for 7-10 days for primary episode. If severe or immunocompromised, IV aciclovir is used. If there is any diagnostic uncertainty, Tzanck smear from the vesicle base or PCR swab confirms HSV. The patient should be counselled that this is a self-limiting condition resolving over 2-3 weeks, with recurrence possible (HSV latency). She needs to understand that glove use is mandatory when treating patients with oral/genital herpes lesions. If after observation and antiviral therapy the condition is worsening or there is clear secondary bacterial infection, then surgical drainage with antibiotics can be considered — but this is the exception, not the rule.

Key Evidence

Factors affecting the prognosis of pyogenic flexor tenosynovitis

Level III

Pang HN, Teoh LC, Yam AK, Lee JY, Puhaindran ME, Tan AB • Journal of Bone and Joint Surgery (American)

Clinical Implication: The Pang classification is the standard prognostic framework for FTS — quantify purulence and ischaemia at operation to predict amputation risk and counsel the patient, and identify high-risk patients (older, comorbid, polymicrobial) for aggressive debridement.

Verify on PubMed (PMID 17671013)

Closed tendon sheath irrigation for pyogenic flexor tenosynovitis

Level IV

Neviaser RJ • Journal of Hand Surgery (American)

Clinical Implication: Closed catheter irrigation via a proximal A1 window and a distal counter-incision is the technique of choice for early, non-necrotic FTS, preserving the pulleys and sheath while achieving rapid functional recovery.

Verify on PubMed (PMID 556478)

Flexor tendon sheath infections of the hand

Level V

Draeger RW, Bynum DK • Journal of the American Academy of Orthopaedic Surgeons

Clinical Implication: Diagnose on Kanavel's signs, drain all but the very earliest cases, and counsel every patient that some residual stiffness is expected even after prompt, technically sound treatment.

Verify on PubMed (PMID 22661567)

Acute hand infections

Level V

Osterman M, Draeger R, Stern P • Journal of Hand Surgery (American)

Clinical Implication: Start empirical antistaphylococcal cover, add MRSA cover for high-risk patients (IVDU, healthcare exposure, high local prevalence), and treat hand infections urgently to avoid functional loss.

Verify on PubMed (PMID 25070032)

In vitro activity of 12 oral antimicrobials against 390 aerobic and anaerobic bacteria from human and animal bite wounds

Level II

Goldstein EJ, Citron DM, Hudspeth M, Hunt Gerardo S, Merriam CV • Antimicrobial Agents and Chemotherapy

Clinical Implication: Amoxicillin-clavulanate is the empirical agent of choice for human and animal bite wounds because it covers the characteristic polymicrobial aerobic/anaerobic flora including Eikenella corrodens and Pasteurella multocida.

Verify on PubMed (PMID 9210683)

Guidelines, Registries & Global Practice

Hand infection management is governed by general antimicrobial-stewardship and surgical-emergency principles rather than a single arthroplasty-style registry. Practice is broadly consistent across major training systems, with differences driven mainly by local MRSA prevalence and antibiotic formularies.

Diagnosis (universal): Kanavel's four signs remain the global clinical standard for pyogenic flexor tenosynovitis across FRCS, FRACS, EBOT, ABOS and DNB/MS curricula. Pain on passive extension is the most consistently cited single sign.
Empirical antibiotics — regional variation: Anti-staphylococcal cover (flucloxacillin or a first-generation cephalosporin) is standard first-line. Routine empirical MRSA cover (e.g. vancomycin) is recommended where community-acquired MRSA prevalence is high (parts of the US per IDSA skin-and-soft-tissue guidance) but is reserved for risk factors (IVDU, healthcare exposure, prior MRSA, failed therapy) in lower-prevalence settings (UK/Australia/much of Europe).
Bite wounds (consistent globally): Amoxicillin-clavulanate is the first-line agent endorsed across UK (NICE/BNF), US and Australasian guidance for human and animal bites; doxycycline plus metronidazole, or a fluoroquinolone plus an anti-anaerobe, are the usual penicillin-allergy alternatives. Tetanus and rabies risk assessment is mandatory for animal bites in endemic regions.
Surgical principle (universal): All but the earliest pyogenic flexor tenosynovitis requires drainage; closed catheter irrigation is preferred for early non-necrotic cases and open drainage for late/necrotic disease, with a low threshold for second-look. This is consistent across hand-society teaching (ASSH, BSSH, FESSH).
Resource-setting variation: Where theatre access or microbiology is limited, earlier empirical broad-spectrum cover and bedside incision/drainage of superficial collections are more common; the underlying surgical anatomy and drainage approaches are unchanged.