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 login to view 3 more bullets pathoanatomy infection travels in the synovial sheath that surrounds the flexor tendon microbiology Staph aureus (40-75%) login to view 1 more bullet MRSA (29%) login to view 1 more bullet other common skin flora login to view 3 more bullets mixed flora and gram negative organsims login to view 1 more bullet Eikenella login to view 1 more bullet Pasteurella multocida login to view 1 more bullet Associated conditions "horseshoe abscess" may develop from spread pyogenic flexor tenosynovitis login to view 2 more bullets Anatomy Tendon sheaths function to protect and nourish the tendons anatomy variations common sheaths extends from login to view 6 more bullets 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 login to view 1 more bullet modalities login to view 1 more bullet outcomes login to view 1 more bullet Operative I&D followed by culture-specific IV antibiotics indications login to view 3 more bullets 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