summary Pyogenic flexor tenosynovitis is an infection of the synovial sheath that surrounds the flexor tendon. Diagnosis is made clinically with the presence of the 4 Kanavel signs. Treatment is urgent irrigation and debridement of the flexor tendon sheath with IV antibiotics. Epidemiology Incidence 2.5 to 9.4% of all hand infections Risk factors diabetes IV drug use immunocompromised patients Etiology Pathophysiology mechanism penetrating trauma to the tendon sheath direct spread from felon septic joint deep space infection pathoanatomy infection travels in the synovial sheath that surrounds the flexor tendon microbiology Staph aureus (40-75%) most common MRSA (29%) intravenous drug abusers other common skin flora staph epidermidis beta-hemolytic streptococcus pseudomonas aeruginosa mixed flora and gram negative organsims in immunocompromised patients Eikenella in human bites Pasteurella multocida in animal bites Associated conditions "horseshoe abscess" may develop from spread pyogenic flexor tenosynovitis of many individuals have a connection between the sheaths of the thumb and little fingers at the level of the wrist infection in one finger can lead to direct infection of the sheath on the opposite side of the hand resulting a "horseshoe abscess" Anatomy Tendon sheaths function to protect and nourish the tendons anatomy variations common sheaths extends from index, middle, and ring fingers from DIP to just proximal to A1 pulley thumb (flexor pollicus longus sheath) from IP joint to as proximal as radial bursa (in wrist) little finger from DIP joint to as proximal as ulnar bursa (in wrist) Presentation Symptoms pain and swelling typically present in delayed fashion (over last 24-48 hours) usually localized to palmar aspect of one digit Physical exam Kanavel signs (4 total) flexed posturing of the involved digit tenderness to palpation over the tendon sheath marked pain with passive extension of the digit fusiform swelling of the digit increased warmth and erythema of the involved digit Imaging Radiographs recommended views radiographs usually not required, but may be useful to rule out foreign object MRI cannot distinguish infectious flexor tenosynovitis from inflammatory but may help determine the extent of the ongoing process Differential Felon Cellulitis Deep space infection Collar button infection Diagnosis Clinical diagnosis is made with careful history and physical examination (Kanavel signs) Treatment Nonoperative (rare) hospital admission, IV antibiotics, hand immobilization, observation indications early presentation modalities splinting outcomes if signs of improvement within 24 hours, no surgery is required Operative I&D followed by culture-specific IV antibiotics indications low threshold to operative once suspected (orthopaedic emergency) late presentation no improvement after 24 hours of non-operative treatment (confirmed diagnosis) technique (see below) Technique I&D of flexor tendon approach full open exposure using long midaxial or Bruner incision two small incisions placed distally at A5 pulley and proximally at A1 pulley and using an angiocatheter Complications Stiffness Tendon or pulley rupture Spread of infection Loss of soft tissue Osteomyelitis