Fact-sheet: Phlegmon of the tendon sheath


Updated on 11/05/2024 at 9:11 AM

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Definition

Pyogenic flexor tenosynovitis is an infection of the tendon sheaths surrounding the tendons. It corresponds to the acute, infectious, and severe form of tenosynovitis of the finger flexor tendons. This infection accounts for 20% of hand infections and can have serious consequences for finger and hand function if not treated promptly.

  • Location: Pyogenic flexor tenosynovitis may be confined to the finger (digital synovial sheath) or extend to the forearm (ulnar or radial digitocarpal synovial sheath).
  • Impact: Pyogenic flexor tenosynovitis can lead to stiffness or even amputation of the finger if not treated promptly.

Clinical features

Functional signs:

  • Pain: constant, of variable intensity, inflammatory in character, sometimes causing insomnia or pulsatile. Its onset may be sudden or progressive depending on the etiology. The pain is localized along the course of the flexor tendon sheath and may radiate to the anterior aspect of the wrist.
  • Hook-like posture of the affected finger (inconstant)

Physical signs:

  • Local signs: Edema: The edema may be localized to the infected finger or extend to the entire hand.
  • Pain on passive extension.
  • Pain on palpation of the proximal recess of the flexor sheath of the affected finger. This recess is located opposite the metacarpal heads for the 2nd, 3rd, and 4th fingers and at the anterior aspect of the wrist for the thumb and 5th finger.
  • Regional signs: Epitrochlear or axillary lymphadenopathy.
  • Lymphangitis.
  • General signs (inconstant, signs of severity): Fever.
  • Chills.
  • Asthenia.

Laboratory findings

  • Inflammation: elevated CRP, leukocytosis.
  • Bacteriologic sampling during surgery to guide antibiotic therapy.

Radiography

  • Limited role: may show soft tissue swelling, reactive bone resorption, or the presence of radiopaque foreign bodies, but these signs are not specific.
  • Assessment for complications: associated arthritis or osteomyelitis.

Ultrasound

Examination of choice.

  • Hypoechoic peritendinous effusion
  • Thickening of the synovial sheath with Doppler hyperemia
  • Intratendinous involvement: The tendon itself may be affected
  • Loss of the normal fibrillar structure of the tendon, which appears less organized.
  • Increased tendon diameter
  • Presence of foreign bodies: Hyperechoic, often with a posterior acoustic shadow
  • Reverberation artifacts may also be observed
  • ! The presence of air in the wound may create artifacts similar to those of foreign bodies
  • Joint effusion: The presence of intra-articular fluid suggests arthritis associated with the pyogenic flexor tenosynovitis.

MRI

May provide information in complex cases or when ultrasound is inconclusive.

  • Thickened synovial sheath with T2 hyperintensity
  • Marked enhancement of the sheath after gadolinium injection, confirming active synovitis. This enhancement also allows distinction between fluid collection, which does not enhance, and the thickened synovium.
  • Variable signal of the sheath on T1- and T2-weighted sequences
  • Thickening and edema of the tendon
  • Signs of arthritis and osteomyelitis.

Vascular intervention

Ultrasound-guided aspiration for analysis of fluid within the tendon sheath:

  • Search for microcrystals: allows exclusion of a microcrystalline cause of tenosynovitis, such as chondrocalcinosis, which can mimic pyogenic flexor tenosynovitis.
  • Culture: allows identification of the causative organism and guides antibiotic therapy.

Management

Management of pyogenic flexor tenosynovitis is a surgical emergency requiring prompt intervention to preserve hand function.

1. Diagnosis:

  • Clinical: The diagnosis is primarily clinical, based on history and physical examination. The cardinal signs described by Kanavel are: Intense pain along the flexor tendon sheath, exacerbated by passive extension of the finger.
  • Fusiform swelling of the finger.
  • Hook-like posture: the finger is held in flexion.
  • Tenderness on palpation of the proximal recess of the sheath.
  • Additional workup: Radiography: Used to look for a radiopaque foreign body or associated bone involvement (osteoarthritis).
  • Ultrasound: Examination of choice to confirm the diagnosis and assess the extent of the infection.
  • MRI: Useful in complex cases or when ultrasound is inconclusive, to assess tendon, joint, or bone involvement.

2. Surgical treatment:

  • Emergency: Surgical intervention must be performed emergently, ideally within 24 hours of diagnosis, to prevent complications and preserve hand function.
  • Technique: Debridement of the entry wound, if present.
  • Opening of the tendon sheath: In early stages (Michon stage 1), a proximal or distal counter-incision may be sufficient.
  • In more advanced stages (Michon stages 2 and 3), complete opening of the sheath is required, from the distal palmar crease to the fingertip pulp for the 2nd, 3rd, and 4th fingers, and up to the wrist for the thumb and 5th finger.
  • Excision of infected and necrotic tissue.
  • Copious irrigation of the sheath with saline.
  • Repair of associated injuries (tendons, nerves, arteries).
  • Partial closure of the wound, leaving the corners open for drainage.

3. Medical treatment:

  • Antibiotic therapy: Empiric intravenous antibiotic therapy is started pending the results of bacteriological samples.
  • Amoxicillin-clavulanic acid is the first-line treatment.
  • Antibiotic therapy is then tailored to the identified organism and its susceptibility.
  • Immobilization: Brief immobilization may be necessary, particularly in cases of tendon repair.
  • Rehabilitation: Rehabilitation is started early to prevent stiffness and restore hand function.

4. Complications:

  • Local: Ischemia, septic recurrence, joint stiffness, tendon adhesions.
  • Regional: Proximal spread of the infection to the hand or forearm.
  • Systemic: Severe sepsis.

5. Prognosis:

Functional prognosis depends on how early treatment is initiated, the extent of the infection, and the causative organism. Delayed treatment can lead to significant functional sequelae, or even finger amputation.

Classification

Michon classification (1974): based on intraoperative findings

  • Stage I: Exudative serositis. The tendon sheath is distended by clear or cloudy fluid, and the synovium is simply hyperemic.
  • Stage II: Turbid or purulent fluid. The synovium is congestive and granulomatous, but the tendon remains intact.
  • Stage III: Tendon necrosis. This stage is characterized by more or less extensive necrosis of the tendons.

Sokolow classification (1987): modifies and refines stage II of the Michon classification, subdividing it into two substages, also based on intraoperative findings:

  • Stage IIa: Near-normal synovium. Only a few areas of the synovium show abnormalities. Synovectomy limited to the pathologic areas is sufficient.
  • Stage IIb: Pathologic synovium along the entire length of the digital canal. The synovium is swollen, hypertrophic, and wine-colored. The subcutaneous tissue may also be infiltrated and show septic areas. Complete synovectomy is required.

Differential diagnosis

Microcrystalline Disorders:

  • Calcium pyrophosphate deposition disease: Chondrocalcinosis can affect the synovial sheaths and mimic flexor tenosynovitis (phlegmon of the tendon sheaths).
  • Resorption of an apatite calcification: Resorption of an apatite calcification within a tendon sheath can cause highly inflammatory tenosynovitis.

Spondyloarthritis:

  • Ankylosing spondylitis and psoriatic arthritis: Dactylitis, or "sausage digit," is acute tenosynovitis of the flexor tendon sheath.

Noninfectious Tenosynovitis:

  • Rheumatoid arthritis
  • Sarcoidosis
  • Giant cell tumor of the tendon sheath

Bursitis

Cellulitis