Infectious flexor tenosynovitis (FTS) is a surgical emergency. If not treated promptly, infectious FTS carries significant morbidity including loss of function of fingers, necrosis of the tendon, and even digit amputation (1).
Infection can be caused in three ways: direct inoculation, contiguous spread, or hematogenous spread, as seen in cases of disseminated gonococcal infection. Tenosynovitis occurs when fluid collects between the visceral and parietal layer of the tendon, the most common location being in the hand and wrist.
Traditionally, diagnosis of infectious FTS is centered on the tetrad known as Kanavel’s signs (swelling of the finger, finger held in partially flexed position, pain on palpation of the flexor tendon, and pain on passive extension of the finger). While Kanavel’s signs are specific for infectious FTD, in a study of 41 participants with infectious FTS, only 54% of patients taken to the operating room (OR) had all of these signs (2). The gold standard of diagnosis remains surgical exploration and drainage. MRI can aid in the diagnosis of FTS, but this is rarely available in the ED. While radiographs may be obtained to look for trauma, osteomyelitis or a foreign body, they offer minimal to no additional benefit in diagnosing infectious FTS.
This article presents a case of a 58-year-old man where point of care ultrasound (POCUS) identified tissue necrosis and fluid along the flexor tendon sheath of the hand, aiding in the rapid diagnosis of FTS, adding to the limited body of literature supporting use of POCUS for early diagnosis of infectious FTS.
Can point of care ultrasound be used in the emergency department to diagnose infectious FTS?
Methods & Study Design
58 year old male with hypertension, diabetes and end stage renal disease.
POCUS looking for fluid in flexor tendon sheath. Appropriate technique is shown in the image below, with a linear ultrasound probe placed on the palmar side of the wrist crease. Common findings of FTS are hypoechoic or anechoic fluid surrounding the flexor tendons.
Accurate diagnosis of FTS
The physicians found a moderate amount of fluid and echogenic material within the tendon sheath, as noted in the image below. Orthopedics was consulted and patient was started on broad spectrum antibiotics and taken to the operating room. They found extensive pus within the flexor tendon sheath and cultures grew Staph aureus.
Strength & Limitations
The POCUS exam the authors describe is practical and useful. This could feasibly be performed by clinicians with relatively little ultrasound training. As mentioned, FTS is a surgical emergency and remains largely a clinical diagnosis, so any modality that helps bring more certainty to the diagnosis, and lead to quicker definitive treatment, is welcome.
It is unclear what the level of ultrasound training was for the physicians who performed this exam. Another note, it may be difficult to distinguish rheumatologic from infectious causes of tenosynovitis using ultrasound, so clinical context is always important. They also mentioned this can only aid in increasing your suspicion for FTS, it cannot be used to rule it out.
POCUS may be an ideal adjunct for the ED physician in the evaluation of a patient with suspected infectious FTS
We agree with the authors conclusions that POCUS can be a useful adjunct to clinical exam in diagnosing FTS, with the understanding that POCUS cannot rule out FTS or distinguish rheumatologic from infectious process.
The Bottom Line
POCUS can be a useful adjunct to clinical exam in diagnosing FTS. Use the linear probe and place at the palmar side of the wrist crease, look for hypoechoic or anechoic material around the flexor tendons with possible thickening of the tendon itself.
This post was written by Betial Asmerom. Review and further commentary was provided by Charles Murchison, MD, Emergency Ultrasound Fellow at UCSD and Amir Aminlari, MD, Ultrasound Faculty at UCSD.
- Mamane, W. et al. Infectious flexor hand tenosynovitis: State of knowledge. A study of 120 cases. J. Orthop. 15, 701–706 (2018).
- Hubbard, D., Joing, S. & Smith, S. W. Pyogenic Flexor Tenosynovitis by Point-of-care Ultrasound in the Emergency Department. Clin. Pract. Cases Emerg. Med. 2, 235–240 (2018).
- Padrez et al. Bedsound Ultrasound Identification of Infectious Flexor Tenosynovitis in the Emergency Department. West J Emerg 2015. 16 (2).