Published in:
01-12-2020 | Musculoskeletal
Bifascicular nature of the flexor digitorum profundus and flexor pollicis longus tendons: forgotten anatomical characteristics rediscovered with US imaging
Published in: European Radiology | Issue 12/2020
Login to get accessAbstract
Objectives
To demonstrate the bifid configuration of the flexor digitorum profundus (FDP) and flexor pollicis longus (FPL).
Methods
In the first part of this study, 20 digits from 4 cadaver hands were dissected and analyzed using anatomical and histological slices. The second part of the study was carried out over a 12-month period starting in August 2018. It was a prospective US imaging study of 300 digits from 30 healthy participants performed by two radiologists in a double-blinded manner. This study focused on two items: tendon shape and whether a central septum separated the two hemitendons. Descriptive statistics were calculated along with the inter-rater reliability.
Results
In 100% (300/300) of fingers and thumbs, the FDP and FPL tendons were made up of two parallel bundles arranged side by side, with a central vertical septum between these two hemitendons, starting at the head of the proximal phalanx (PP) and continuing distally. This central septum was always present starting at the proximal third of PP for the FDP of the index, middle, and ring fingers. The septum was more difficult to identify in the thumb and little finger. Cohen’s kappa indicated near perfect agreement when all digits were considered together (≥ 0.9), and substantial agreement for the thumb (0.71) and for the little finger (0.82).
Conclusions
With US imaging, the bifascicular nature of the FDP and FPL tendons is easy to see, as these tendons have a double-barreled configuration starting at the head of the proximal phalanx.
Key Points
•Analysis of anatomical slices of the hand tendons found a bifascicular appearance of the flexor digitorum profundus and flexor pollicis longus tendons starting at the head of the proximal phalanx.
•This distinct feature of two hemitendons arranged side by side was seen in 100% of tendons we examined with US. It is associated with a vertical central septum that causes anisotropy.
•Awareness of this “forgotten” anatomical detail has practical implications when interpreting images generated by latest-generation US systems and during surgery on hand flexor tendons.