Flexor Tenosynovitis

anatomy

Illustration by Dr. Lisa Bryski

Flexor tenosynovitis is a limb threatening emergency that results from an infection of the tendon sheath. Of note, the infection can spread between tendon sheaths or between the radial and ulnar bursa. When it spreads between the two bursa, it’s often termed a horseshoe abscess.

Remember, the hand does not have a lot of space. As infection spreads, the compartment pressures can get critically high. ^1,2

Classic Presentation

Patient's present two to five days following an injury such as a cut, puncture, or bite. They will present with a painful swollen finger often held in flexion.

Flexor tenosynovitis can be secondary to hemotogenous spread but this is less common. ^1,2

Diagnosis: Kanavel Signs

This is a clinical diagnosis! Blood work and imaging are often non-specific.

The Kanavel signs are the 4 cardinal exam findings for flexor tenosynovitis.²

Fun Fact: The four Kanavel signs were first outlined in 1912.

The four signs are:

Tenderness over volar tendon sheath.

- - Feel down adjacent digits and the opposite hand as a control.
  - Sheath tenderness is thought to be the greatest discriminator for flexor tenosynovitis.

Pain with passive extension is often the earliest finding
Finger held in flexion passively
Uniform digit swelling

Limited studies exist for sensitivity and specificity but has been cited to be as high as 97% but with specificity as low as 51%. ³

Kanavel signs are not reliable in pediatric populations or with flexor tenosynovitis of the thumb.

Tip: Avoid palpating areas of cellulitis when examining for Kanavel signs as this can cloud the examination.

Case studies also report the use of ultrasound to help diagnose flexor tenosynovitis, although remember this is a clinical diagnosis. To image the flexor tendons, use a high frequency linear array transducer (14-8 MHz) and consider a water bath or step-off pad to optimize visualization of superficial structures.

The goal is visualize the tendons in both short and long axis. Tendons are more striated than skeletal muscle. With flexor tenosynovitis, these tendons become thickened, lose their characteristic structure, and become edematous. They also can develop areas of increased vascularity that can be seen with colour doppler. ^5,6

Thickened, edematous tendon.⁵

Normal flexor tendon. Note the striae.⁵

Significant edema around the tendon⁶

Treatment

⁴

There are three initial treatment steps to be undertaken in the ED:

Broad spectrum antibiotics
Hand surgeon consultation for inpatient admission.
Splinting and elevation of the hand

These infections are often polymicrobial. Common pathogens include Staphylococcus, Streptococcus, Mycoplasma, MRSA, Cryptococcus and Gram negatives. Occasionally, it can be caused by Neisseria gonorrhoeae. Choose broad spectrum antibiotics that also cover for Pseudomonas and MRSA.

The patient should be referred to a hand surgeon for an in-patient admission. These patients may be treated conservatively or undergo a drainage and irrigation. Regardless of the choice, they require close monitoring.

There is some growing evidence that systemic steroids may be administered to help limit biofilm production. However, the decision to administer steroids should be done in consultation with the hand surgeon. ^1,2

References

Chapman, T., & Ilyas, A. M. (2019). Pyogenic Flexor Tenosynovitis: Evaluation and Treatment Strategies. The Journal of Hand Surgery, 44(11), 981-985.
Hyatt, B. T., & Bagg, M. R. (2017). Flexor Tenosynovitis. Orthopedic Clinics of North America, 48(2), 217-227.
Kennedy, C. D., Lauder, A. S., Pribaz, J. R., & Kennedy, S. A. (2017). Differentiation Between Pyogenic Flexor Tenosynovitis and Other Finger Infections. Hand, 12(6), 585-590.
Chan, E., Robertson, B. F., & Johnson, S. M. (2019). Kanavel signs of flexor sheath infection: A cautionary tale. British Journal of General Practice, 69(683), 315-316.
Cohen, S. G., & Beck, S. C. (2015). Point-of-Care Ultrasound in the Evaluation of Pyogenic Flexor Tenosynovitis. Pediatric Emergency Care, 31(11), 805-807.
Hubbard, D., Joing, S., & Smith, S. (2018). Pyogenic Flexor Tenosynovitis by Point-of-care Ultrasound in the Emergency Department. Clinical Practice and Cases in Emergency Medicine, 2(3), 235-240.

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