By Alissa Mussell, MD
Jardin E, Delord M, Aubry S, et al. Usefulness of ultrasound for the diagnosis of pyogenic flexor tenosynovitis: A prospective single-center study of 57 cases. Hand Surg Rehabil. 2018 Apr; 37(2):95-98. epub 2018 Feb 1.
Point of care ultrasound (POCUS) has been proposed as a diagnostic adjunct for infectious or pyogenic flexor tenosynovitis (PFT) but has not been well studied. Previous mentions in existing literature were limited to two small studies from the 1980s, a few case reports, and a retrospective case series. The current study is the most robust evaluation of POCUS for diagnosing infectious flexor tenosynovitis to date.
This was a single center prospective cohort study. Seventy-three potential participants were seen during the study period; 16 were diagnosed with infectious tenosynovitis based on clinical exam alone (Kanavel signs) and were excluded from the study. The remaining 57 patients with a non-diagnostic clinical exam were enrolled. Inclusion criteria were any of the following: finger pain with signs of inflammation (pain, redness, heat), confirmed infection entry portal, or pain over the flexor tendon sheath.
POCUS was used to identify signs of early PFT compared to a contralateral or nearby unaffected finger: 1) hypoechoic effusion surrounding the tendon with no color doppler signal, and/or 2) a thickened synovial sheath that is hypoechoic and hyperemic on color Doppler. Patients with a positive ultrasound were immediately sent for surgical treatment. If there was no sheath effusion or hyperemia, the patient was diagnosed with cellulitis and started on empirical antibiotics with follow up every 2 days until resolution.
In this study 27 patients were found to have peritendinous effusion (47.4%) and 23 patients were found to have synovial sheath thickening (40.4%). Twenty-seven patients were taken to the OR and 18 of these had a positive intraoperative diagnosis of PFT based on purulent or culture positive synovial fluid. The authors did not define if the 27 patients receiving operative management had one or both of study findings on POCUS. It would have also been useful to explore if the 18 patients with operatively confirmed PFT had one or both of the significant findings on POCUS compared to the 9 patients in which PFT was ruled out operatively.
Of the 29 patients who were diagnosed with cellulitis, given antibiotics and monitored, one patient required operative intervention later because of a poor clinical outcome. PFT was considered ruled out in the nonoperative group if the patient improved clinically on antibiotics alone in <21 days.
In this study, POCUS had a sensitivity of 94.4%, specificity of 74.4%, PPV of 63%, and NPV of 96.7% for infectious tenosynovitis if the clinical diagnosis was uncertain based on physical exam alone.
While this study certainly adds to our understanding of the utility of POCUS to evaluate for PFT, it does have some limitations. It would be interesting to look at the sensitivity/specificity for each of the POCUS findings separately compared to the sensitivity/specificity for both findings together.