Introduction
Hand infections are common among people. Deep hand infections like tenosynovitis are surgical emergencies resulting in permanent morbidity. Tenosynovitis is inflammation within the tendons and synovial sheath. The condition primarily develops in the hand and wrist but can appear in any extremities where the tendon glides with a synovial-lined fibro-osseous sheath. This article discusses the infectious cause of tenosynovitis.
What Is Infectious Flexor Tenosynovitis?
Infectious flexor tenosynovitis, or flexor sheath infection, is an acute infection within the tendon sheath. A purulent fluid collects between the visceral and purulent layers of the flexor tendon. The infections can also spread to deep fascial spaces. It is a common illness affecting the hands and has an incidence of 2.5 to 9.4 percent among all hand infections. The condition is a surgical emergency as it impairs blood flow to the tendon sheath and results in necrosis that needs immediate treatment.
What Causes Infectious Flexor Tenosynovitis?
The condition is caused by penetration and invasion of infectious agents within the tendon sheath, which spreads to the synovial membrane. The organisms that cause infectious flexor tenosynovitis are pyogenic bacteria, Mycobacterium, and fungi.
The condition can also develop because of trauma, contagious spread from other tissues, and hematogenous spread. Other causes include animal bites, intravenous drug abuse, puncture wounds, or wounds with skin breach, laceration, or ulceration exposed to salt or fresh water.
Infectious tenosynovitis could be associated with cellulitis, septic bursitis, septic arthritis, bone erosions, or foreign bodies. Individuals with diabetes, immunosuppression, and smoking are at a higher risk for developing infectious flexor tenosynovitis.
What Are the Symptoms of Infectious Flexor Tenosynovitis?
When the wound in hand is associated with severe tenderness, it raises high suspicion for infectious flexor tenosynovitis. The patients also experience swelling, tenderness, warmth, and painful range of motion in the affected tendon.
The condition initially begins as exudative fluid within the tendon sheath. The discharge gradually turns purulent. An excessive bacterial overgrowth within the synovial fluid increases fluid and pressure, which causes ischemia and septic necrosis of the tendon sheath and adjacent structures.
Infection and pus within the tendon sheath sometimes cause adhesions and septations. Individuals with infectious flexor tenosynovitis may not develop a fever.
How Is Infectious Flexor Tenosynovitis Diagnosed?
Diagnosing the condition is possible with clinical symptoms and radiographic imaging. The infectious flexor tenosynovitis is diagnosed by:
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Laboratory Tests: Affected individuals may show increased inflammatory markers such as leukocyte count and C reactive protein (CRP).
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Kanavel Signs: These include the flexed testing position of the digit, fusiform swelling (sausage digit), tenderness along the flexor tendon sheath, and pain with the passive extension of the digit.
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Radiographic Imaging: Imaging of affected individuals with infectious flexor tenosynovitis reveals the presence of fluid within the tendon sheath, which shows different signal characteristics such as pus, blood, or gas. Taking an X-ray helps identify occult foreign bodies, soft tissue swelling, or gas but is of limited value. Ultrasound imaging of the affected individual reveals synovial hyperemia and fluid distension of the tendon sheath.
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Culturing the Surgical Sample or Fluid Drained: Infectious flexor tenosynovitis can be confirmed by culturing the purulent synovial fluid.
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Synovial Biopsy: Taking a synovial biopsy is advised if a granulomatous infection is suspected.
The earliest sign of the condition is pain during passive extension. Pain and tenderness along the flexor sheath indicate the progression of infection more proximally. The presence of all four Kanavel signs predicts high sensitivity for flexor tenosynovitis.
What Is the Differential Diagnosis of Infectious Flexor Tenosynovitis?
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Acute Calcific Tendinitis and Rheumatoid Arthritis: They can restrict motion and cause pain within the tendon sheath but are differentiated with gradual onset and absence of Kanavel signs.
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Disseminated Gonococcal Infection: The condition does cause tenosynovitis but affects multiple joints such as wrists, fingers, ankles, and toes. Additionally, affected patients develop rash, fever, and polyarthralgia and have a risk of sexually transmitted diseases.
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Tendon Sheath Infection: No tuberculosis mycobacteria cause infection in tendon sheath. However, these infections can become indolent in immunocompromised patients.
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Inflammation Tenosynovitis: It is caused by inflammatory conditions such as autoimmune arthropathies and crystal joint depositions. The condition is treated on an outpatient basis.
How Is Infectious Flexor Tenosynovitis Treated?
Affected individuals require antibiotic therapy, primarily with cephalosporins and cultures, if the infection is diagnosed after 24 to 48 hours. If methicillin-resistant Staphylococcus aureus (MRSA) is prevalent within the infected tendon sheath, then Trimethoprim, Clindamycin, Doxycycline, and Linezolid can be used instead of Cephalosporins. Treatment measures like splinting and limb elevation help treat patients.
Most infectious flexor tenosynovitis is considered an emergency and requires surgical treatment if they do not respond to antibiotic treatment after 24 hours or if the wound is more than 48 hours. Treatment for flexor tenosynovitis is treated with surgical drainage. It is done by irrigating the tendon sheath by inserting a cannula in one end and allowing the irrigation fluid to pass from the other end of the tendon sheath. The individual with severe infection might need extensive open incision. Closed drainage of pus is commonly preferred but causes discomfort to the patients. However, if the infection is uncontrollable, it requires open drainage.
Most patients with infectious flexor tenosynovitis start feeling better after beginning antibiotic treatment. However, it is essential to continue taking the antibiotics for the prescribed duration with adequate dosing.
What Are the Complications of Infectious Flexor Tenosynovitis?
Individuals with infectious flexor tenosynovitis are at a higher risk for developing complications and have a longer recovery time. There is a risk of infection spreading to other parts of the body. Some affected individuals develop stiffness deformity or may need amputation of the digit. Other complications include soft tissue necrosis, osteomyelitis, stenosing tenosynovitis, and necrotizing fasciitis.
Pyogenic flexor tenosynovitis can develop from infectious flexor tenosynovitis. It forms an abscess at the base of the digit. The abscess is usually benign and is in the shape of a horseshoe.
What Is the Prognosis for Infectious Flexor Tenosynovitis?
The outcome for individuals suffering from infectious flexor tenosynovitis depends on several factors. Older age groups, individuals with diabetes, peripheral vascular disease, human bite wounds, late presentation of symptoms, digital ischemia, subcutaneous purulence, or kidney disorder have poorer outcomes. Misdiagnosis or improper treatment of infectious flexor tenosynovitis can have life-threatening implications.
Conclusion
Infectious flexor tenosynovitis is the tendon sheath inflammation caused by an infectious agent. Bacteria are the predominant cause of the condition. The condition is often diagnosed with clinical symptoms like Kanavel signs or imaging. Treatment for infectious flexor tenosynovitis includes antibiotic therapy and surgical drainage.
