Traumatic flexor tendon injuries

Abstract

The flexor system of the fingers consisting of flexor tendons and finger pulleys is a key anatomic structure for the grasping function. Athletes and manual workers are particularly at risk for closed injuries of the flexor system: ruptured pulleys, ruptures of the flexor digitorum profundus from its distal attachment ("jersey finger"), and less frequently, ruptures of the flexor digitorum superficialis and of the lumbrical muscles. Open injuries vary more and their imaging features are more complex since tendons may be torn in several locations, the locations may be unusual, the injuries may be associated with nerve and vascular injuries, fibrosis… Sonography is the best imaging modality to associate with the clinical exam for it allows an experienced physician to make an accurate and early diagnosis, crucial to appropriate early treatment planning.

Ultrasound of flexor digitorum apparatus in acute and chronic pathology

“…The A2 and A4 pulleys are wider and insert directly into the bone over the proximal and middle phalanges, respectively. The annular pulleys are made of concentric collagen fibres that can resist loads of up to 700 N . The cruciate pulleys of C1, C2 and C3 lie between the A2–A3, A3–A4 and A4–A5 annular pulleys, respectively.…”

“…Open injuries are the consequence of lacerations and penetrating trauma in which the soft tissues overlying the flexor tendons are disrupted. Closed injuries occur when the overlying soft tissues are intact, usually as a result of acute trauma from sport or manual work . Rarely closed flexor tendon rupture may be caused by rheumatoid arthritis, gout or other arthropathies…”

“…Type V involves avulsion of the FDP associated with a separate fracture of the distal phalanx Type VI ‘false mallet finger’ is described as the insertion of the FDP, remaining intact but the dorsal aspect of the distal phalanx is fractured (Figure ) …”

“…Micro‐traumas are the consequence of chronic repetitive movement of the finger, related to occupational or recreational activities . Acute rupture is the result of sudden excessive traction on the flexor tendons, such as in elite rock climbers where the finger withstands their entire body weight causing detachment of the A2 pulley and anterior bowstringing of the tendons …”

“…Normal pulleys appear to have three layers, hypoechoic in the central portion and hyperechoic on either side with a thickness that does not exceed 0.3 to 0.5 mm . Abnormal pulleys appear diffusely thickened and hypoechoic (Figure ), which is a hallmark of trigger finger on ultrasound .…”