Spot the Cardinal Sign of Flexor Tenosynovitis: Case Study

Spot the Cardinal Sign of Flexor Tenosynovitis: Case Study

Patient Presentation & History

A 48-year-old male, a self-employed carpenter, presented to the emergency department complaining of severe pain and swelling in his left index finger. The pain had started acutely approximately 36 hours prior after he sustained a superficial puncture wound to the volar aspect of his left index finger with a small wooden splinter while working. He initially self-treated with topical antiseptic and a plaster, dismissing the injury as minor. However, over the past 24 hours, the pain progressively worsened, becoming throbbing and constant, accompanied by increasing swelling, redness, and a subjective fever. He reported significant limitation in using his left hand.

Demographics: 48-year-old male, right-hand dominant.
Mechanism of Injury: Puncture wound to the volar aspect of the left index finger by a wooden splinter.
Onset: Acute, 36 hours prior to presentation.
Symptoms: Progressive, severe throbbing pain, fusiform swelling, erythema, subjective fever, functional impairment of the affected digit.
Comorbidities: Well-controlled Type 2 Diabetes Mellitus (HbA1c 6.8%), no known allergies. Non-smoker, occasional alcohol use. No history of prior hand infections or surgeries.

Clinical Examination

General Appearance: Afebrile (37.5°C), alert, and cooperative but visibly distressed by pain.
Local Examination (Left Hand, Index Finger):

• Inspection:

  • Erythema: Pronounced redness extending from the metacarpophalangeal (MCP) joint to the distal interphalangeal (DIP) joint, involving the entire volar and partially the dorsal aspect of the index finger.
  • Swelling: Marked, symmetrical fusiform swelling of the entire index finger, giving it a 'sausage digit' appearance. There was mild extension to the adjacent web space.
  • Posture: The index finger was held in a position of slight flexion, characteristic of the 'posture of flexion' sign.
  • Puncture Wound: A small, erythematous puncture site was noted on the volar aspect of the proximal phalanx, with a small amount of seropurulent discharge.

• Palpation:

  • Tenderness: Exquisite tenderness elicited along the entire course of the flexor tendon sheath, from the A1 pulley to the insertion of the flexor digitorum profundus (FDP) tendon distally. This tenderness was maximal over the A2 pulley.
  • Warmth: Significant warmth was noted over the affected digit.
  • Fluctuance: No distinct fluctuant abscess was palpated within the pulp space or tendon sheath.

• Range of Motion (ROM):

  • Active Flexion: Severely limited and extremely painful. The patient was unable to actively flex the index finger beyond its resting flexed posture.
  • Active Extension: Absent due to pain.
  • Passive Extension: The cardinal sign of pain on passive extension of the digit was present and profoundly painful, preventing full extension even with gentle manipulation.
  • Adjacent Digits: ROM of the middle, ring, and small fingers was pain-free and full. Thumb ROM was also preserved.

• Neurological Assessment:

  • Sensation: Grossly intact to light touch and two-point discrimination in the digital nerve distribution of the index finger (radial and ulnar digital nerves), although difficult to assess fully due to pain.
  • Motor: Intrinsic and extrinsic muscle function of the unaffected digits was normal. No specific motor deficit noted for the index finger beyond that caused by pain and swelling.

• Vascular Assessment:

  • Capillary Refill: Slightly sluggish (3 seconds) in the index finger, likely due to significant edema, but palpable digital pulses were present bilaterally. No signs of vascular compromise requiring urgent intervention were noted.

Kanavel's Four Cardinal Signs of Flexor Tenosynovitis:
All four cardinal signs were present, strongly supporting the diagnosis of acute purulent flexor tenosynovitis:
1. Uniform Swelling: Fusiform swelling of the entire digit.
2. Flexed Posture: The digit was held in slight flexion.
3. Tenderness Along the Flexor Tendon Sheath: Palpable tenderness from the A1 pulley to the DIP joint.
4. Exquisite Pain on Passive Extension: The most sensitive and specific sign.

Imaging & Diagnostics

Laboratory Investigations:
* Complete Blood Count (CBC): Leukocytosis with white blood cell (WBC) count of 18.5 x 10^9/L (normal range 4.0-10.0), with a significant left shift (neutrophils 85%).
* Erythrocyte Sedimentation Rate (ESR): Elevated at 65 mm/hr (normal <15).
* C-Reactive Protein (CRP): Markedly elevated at 120 mg/L (normal <5).
* Blood Cultures: Sent, pending results.
* Glucose: Random blood glucose was 180 mg/dL, reflecting poorly controlled diabetes or stress hyperglycemia.

Radiological Imaging:

• Plain Radiographs (Left Hand, AP, Oblique, Lateral views):

  • Revealed soft tissue swelling primarily involving the index finger.
  • No evidence of fracture, dislocation, osteomyelitis, or septic arthritis in the immediate presentation.
  • No radiopaque foreign body was identified (though a wooden splinter would be radiolucent).

• Ultrasound:

  • Performed in the emergency department, demonstrated a significant anechoic effusion within the flexor tendon sheath of the index finger, consistent with purulent collection.
  • Tendon sheath thickening and hyperemia on Doppler were also noted.
  • Helpful in differentiating from cellulitis and ruling out a discrete abscess in the pulp or other deep spaces. It could not definitively rule out a retained radiolucent foreign body.

• Magnetic Resonance Imaging (MRI):

  • Generally not indicated in acute purulent flexor tenosynovitis due to the urgency of surgical intervention. The diagnosis is clinical, supported by labs and sometimes ultrasound.
  • Could be considered in atypical presentations, chronic cases, or to rule out osteomyelitis/deep space infection if the diagnosis is unclear or if a retained foreign body is suspected but not seen on X-ray/ultrasound and the infection is not rapidly progressing. In this acute, clear case, it was deferred.

Differential Diagnosis

The presentation of acute pain, swelling, and reduced function in a digit, particularly after a penetrating injury, necessitates a thorough differential diagnosis to ensure prompt and accurate management.

Surgical Decision Making & Classification

The diagnosis of acute purulent flexor tenosynovitis, confirmed by the presence of Kanavel's four cardinal signs, elevated inflammatory markers, and ultrasound findings, mandates urgent surgical intervention.

Rationale for Operative Intervention:
* Time is Tendon: Flexor tenosynovitis is a surgical emergency. The flexor tendon sheath is a confined space. Accumulation of purulent exudate leads to increased pressure, which compromises the vascular supply to the avascular flexor tendons (nourished by synovial fluid and vincula). This results in rapid tendon necrosis, adhesions, and potential rupture, leading to irreversible functional impairment.
* Infection Control: Surgical drainage and irrigation are necessary to remove pus, reduce bacterial load, and allow antibiotics to penetrate the infected area more effectively.
* Foreign Body Removal: If a foreign body (like the suspected wooden splinter) is present, it acts as a nidus for infection and must be removed surgically.
* Prevention of Spread: Untreated infections can spread to adjacent tendon sheaths (e.g., ulnar bursa, radial bursa via common synovial sheath), deep fascial spaces, bones (osteomyelitis), or lead to systemic sepsis.

Non-Operative Management:
* Contraindicated: Non-operative management with antibiotics alone is generally reserved for very early, mild cases (e.g., non-suppurative tenosynovitis or "pre-suppurative" phase) or cases where the diagnosis is uncertain and inflammation is mild. However, once Kanavel's signs are unequivocally present, surgical drainage is the standard of care. Delay dramatically increases morbidity.

Classification (Not for Severity, but for Diagnosis):
* Kanavel's Four Cardinal Signs: As previously detailed, these are the diagnostic criteria that guide the urgent decision for surgical management. There is no universally accepted classification system for the severity of purulent flexor tenosynovitis that dictates different operative approaches; rather, the presence of the condition itself dictates surgery. While some authors may refer to stages (e.g., initial inflammatory, purulent, necrotic), these are largely descriptive of disease progression rather than a formal pre-operative classification guiding specific interventions beyond "drainage."

Surgical Technique / Intervention

The patient was immediately scheduled for emergent incision and drainage.

Pre-operative:
* Antibiotics: Intravenous broad-spectrum antibiotics (e.g., Vancomycin 1g IV and Piperacillin-Tazobactam 4.5g IV) were initiated immediately upon diagnosis in the ED.
* Consent: Informed consent obtained, detailing the procedure, potential complications (stiffness, adhesion, recurrence, nerve injury, loss of function, amputation), and need for hand therapy.

Anesthesia and Positioning:
* Anesthesia: General anesthesia was chosen due to the patient's anxiety and anticipated extensive debridement. A tourniquet was applied to the upper arm.
* Positioning: Supine position with the left arm abducted and pronated on a sterile hand table.

Surgical Approach and Technique:

1. Tourniquet Inflation: After sterile preparation and draping, the arm tourniquet was inflated to 250 mmHg.
2. Incisions:
   • Two standard Bruner-type mid-axial incisions were made on the affected index finger:
     • Proximal Incision: Centered over the proximal phalanx, extending from the A1 pulley level to just proximal to the A3 pulley.
     • Distal Incision: Centered over the middle phalanx, extending from just distal to the A3 pulley to the A5 pulley level.
   • Care was taken to avoid the neurovascular bundles, which are located volar to the mid-axial line.
3. Tendon Sheath Exposure and Opening:
   • The skin and subcutaneous tissue were carefully incised. The flexor tendon sheath was identified.
   • The tendon sheath was incised longitudinally along its mid-axial aspect through both incisions. This immediately released a significant amount of thick, yellowish purulent material under pressure.
4. Debridement and Irrigation:
   • Gross pus was evacuated. The tendon sheath was thoroughly irrigated with copious amounts of warm sterile normal saline (typically 500-1000 mL or more) using a pulsed lavage system. This irrigation was performed both proximally and distally through both incisions.
   • The flexor digitorum profundus (FDP) and superficialis (FDS) tendons were visually inspected. No overt necrosis or fraying was observed, but the synovium was hyperemic and edematous. All necrotic or severely inflamed synovium was debrided using fine curettes and rongeurs.
   • The suspected wooden splinter was not found intraoperatively, suggesting it had either disintegrated or was not significant enough to act as a persistent nidus.
5. Drain Placement (Continuous Irrigation System):
   • A small, multi-holed plastic irrigation catheter (e.g., 18-gauge angiocatheter or small silicone drain) was threaded proximally into the tendon sheath through the distal incision.
   • A second small catheter was threaded distally through the proximal incision, acting as an outflow drain.
   • This continuous irrigation system allows for post-operative flushing with antibiotic-laden saline (e.g., bacitracin 50,000 units in 500 mL saline, though plain saline is also widely used) or plain saline, to further cleanse the sheath and ensure complete evacuation of purulence. Some surgeons prefer simply leaving the wounds open for daily packing.
6. Wound Closure:
   • The skin incisions were left open and loosely packed with antibiotic-soaked gauze to allow for drainage and prevent re-accumulation of pus. The continuous irrigation system was secured.
7. Dressing: A bulky, protective hand dressing was applied, keeping the finger in a position of function (MCP flexion, IP extension) to facilitate early motion.

Post-Operative Protocol & Rehabilitation

Immediate Post-operative (Day 0-3):
* Wound Care & Irrigation:
* Continuous irrigation with sterile normal saline (or dilute antibiotic solution per surgeon preference) at a slow rate (e.g., 5-10 mL/hour) via the inflow catheter for 24-48 hours.
* Daily dressing changes, monitoring for signs of persistent infection (e.g., continued purulent discharge, increasing erythema, systemic signs).
* Antibiotics:
* Intravenous broad-spectrum antibiotics continued. Intraoperative cultures of pus were sent, and the antibiotic regimen would be tailored based on sensitivities. Typical duration of IV antibiotics is 48-72 hours post-op, or until inflammatory markers (WBC, CRP) show a clear downtrend.
* Pain Management: Aggressive pain control with opioid and non-opioid analgesics to facilitate early motion.
* Hand Elevation: Strict hand elevation (e.g., on pillows) to minimize edema.
* Early Motion: Crucial for preventing adhesions and stiffness. Under the guidance of a Certified Hand Therapist (CHT) or trained nursing staff, gentle active and passive range of motion exercises (specifically differential gliding exercises for FDP and FDS) were initiated as soon as pain allowed, typically within 24-48 hours. This includes active flexion and extension of the affected digit, starting within the limits of comfort. Splinting in an intrinsic-plus position (MCPs flexed, IPs extended) may be used for rest, but prolonged static immobilization is strictly avoided.

Early Rehabilitation (Week 1-4):
* Antibiotics: Transition to oral antibiotics (based on culture sensitivities) for an extended course, typically 2-4 weeks, depending on the severity of infection and resolution of inflammatory markers.
* Wound Healing: Wounds left open were managed with daily sterile dressing changes, allowing for healing by secondary intention or delayed primary closure if clean granulation tissue appeared. Irrigation catheters removed once drainage subsided and clinical improvement evident.
* Hand Therapy:
* Intensified active and passive ROM exercises to optimize tendon glide and joint mobility.
* Emphasis on differential flexor tendon gliding exercises.
* Gentle blocking exercises (holding one joint, moving another).
* Edema control (elevation, gentle massage, compression garments/gloves).
* Scar management techniques (massage, silicone sheeting) once wounds are closed.
* Splinting: Dynamic flexion or extension splints may be incorporated to regain motion, particularly if stiffness develops.
* Strength: Gentle grip strengthening exercises initiated as pain allows, typically after 2-3 weeks.

Late Rehabilitation (Week 4+):
* Full ROM & Strength: Continue working towards full range of motion and restoration of grip strength.
* Return to Activity: Gradual return to activities of daily living and work, avoiding strenuous activities that could jeopardize tendon healing or cause re-injury. For a carpenter, this would involve a phased return to work with modified duties initially.
* Monitoring: Regular follow-up appointments to monitor for recurrent infection, chronic pain, or persistent stiffness.

Potential Complications to Monitor:
* Recurrent infection.
* Stiffness and adhesions of flexor tendons (most common long-term complication).
* Tendon rupture (rare but devastating).
* Chronic pain, hypersensitivity, or complex regional pain syndrome (CRPS).
* Osteomyelitis or septic arthritis (if infection spread to bone or joint).
* Need for tenolysis (secondary surgery to release adhesions).

Pearls & Pitfalls (Crucial for FRCS/Board Exams)

Pearls

• High Index of Suspicion: Any patient presenting with digital pain, swelling, and especially a history of penetrating trauma to the hand, requires immediate consideration of flexor tenosynovitis.
• Kanavel's Signs are Paramount: Know, recognize, and elicit all four cardinal signs:
  1. Uniform fusiform swelling of the digit.
  2. Flexed posture of the digit.
  3. Tenderness along the course of the flexor tendon sheath.
  4. Exquisite pain on passive extension of the digit.
     The presence of these signs is virtually pathognomonic for purulent flexor tenosynovitis and mandates urgent surgical intervention.
• Surgical Emergency: Flexor tenosynovitis is a true surgical emergency. "Time is tendon." Delay in surgical drainage and debridement directly correlates with increased risk of tendon necrosis, adhesions, stiffness, and permanent functional deficit.
• Thorough Irrigation and Debridement: The goal of surgery is complete washout of purulence and removal of any necrotic tissue or foreign bodies. Copious saline irrigation is essential.
• Empiric Broad-Spectrum Antibiotics: Initiate IV antibiotics immediately upon diagnosis, prior to surgery. Culture guided therapy is important, but empiric coverage (e.g., for Staphylococcus aureus , including MRSA, and Gram-negative organisms, especially with penetrating injuries) is critical.
• Early Mobilization is KEY: Despite the infection, early active and passive range of motion, often within 24-48 hours post-operatively, is vital to prevent adhesions between the flexor tendons and the tendon sheath. This requires careful pain management and close collaboration with hand therapy.
• Consider Comorbidities: Diabetes, immunosuppression, and peripheral vascular disease increase the risk of infection, severity, and complicate healing. Aggressive management of these conditions is integral to overall patient outcome.

Pitfalls

• Misdiagnosis: Confusing flexor tenosynovitis with simple cellulitis, septic arthritis, or gout. Cellulitis lacks the specific tendon sheath tenderness and pain on passive extension. Septic arthritis pain is localized to the joint, not the entire sheath. Misdiagnosis leads to inappropriate or delayed treatment.
• Delayed Treatment: The most common and devastating pitfall. Waiting for definitive culture results or assuming antibiotics alone will suffice once Kanavel's signs are present will lead to irreversible tendon damage and poor functional outcomes.
• Inadequate Surgical Drainage: Insufficient incisions, incomplete debridement, or failure to remove a retained foreign body can lead to persistent or recurrent infection.
• Prolonged Immobilization: Fear of disrupting healing or increasing pain can lead to prolonged immobilization, resulting in severe stiffness and adhesions. This is a common and avoidable pitfall.
• Failure to Address Foreign Body: If a foreign body is suspected (especially with puncture wounds), diligent search and removal are paramount during surgery. Radiotranslucent materials (wood, plastic) require careful exploration.
• Inappropriate Antibiotic Regimen: Failure to tailor antibiotics based on culture and sensitivity results can lead to treatment failure or resistance.
• Inadequate Rehabilitation: Poor compliance with hand therapy or lack of appropriate guidance can lead to sub-optimal functional recovery despite successful surgery.

Understanding these pearls and pitfalls is critical for any orthopedic surgeon managing hand infections, especially a rapidly progressing and potentially devastating condition like purulent flexor tenosynovitis.