Flexor pulley system of fingers of hand
Ligamenta cruciata et anulare digitorum manus
Definition
The flexor pulley system of fingers of hand consists of a series of fibrous bands that form part of the fibrous flexor sheath on the palmar side of each finger. These structures guide and stabilize the flexor digitorum superficialis (FDS), flexor digitorum profundus (FDP), and flexor pollicis longus (FPL) tendons as they glide during finger movement.
Components
The flexor pulley system is made up of:
Five annular pulleys (A1–A5): Strong, transverse bands that firmly anchor the tendons close to the bone.
Additional oblique and variable annular pulleys in the thumb
Three cruciate pulleys (C1–C3): Thin, cross-shaped bands between the annular pulleys that allow the sheath to flex and adjust during movement.
Locations
A1: Over the metacarpophalangeal (MCP) joint.
A2: Along the proximal phalanx.
A3: Over the proximal interphalangeal (PIP) joint.
A4: Along the middle phalanx.
A5: Over the distal interphalangeal (DIP) joint.
C1–C3: Positioned between the annular pulleys (A2–A3, A3–A4, and A4–A5 respectively).
Function
The flexor pulley system of fingers of hand:
Holds the flexor tendons close to the phalanges, preventing bowstringing during flexion.
Ensures smooth, efficient gliding of tendons within their synovial sheaths.
Allows coordinated and powerful flexion of the fingers necessary for gripping and fine motor control.
References
Hauger, O., Chung, C.B., Lektrakul, N., Botte, M.J., Trudell, D., Boutin, R.D. and Resnick, D., 2000. Pulley system in the fingers: normal anatomy and simulated lesions in cadavers at MR imaging, CT, and US with and without contrast material distention of the tendon sheath. Radiology, 217(1), pp.201-212.
Petchprapa CN, Vaswani D. MRI of the Fingers: An Update. AJR Am J Roentgenol. 2019 Sep;213(3):534-548. doi: 10.2214/AJR.19.21217. Epub 2019 Jul 3. PMID: 31268729.
Gupta P, Lenchik L, Wuertzer SD, Pacholke DA. High-resolution 3-T MRI of the fingers: review of anatomy and common tendon and ligament injuries. AJR Am J Roentgenol. 2015 Mar;204(3):W314-23. doi: 10.2214/AJR.14.12776. PMID: 25714317.
Clavero JA, Alomar X, Monill JM, Esplugas M, Golanó P, Mendoza M, Salvador A. MR imaging of ligament and tendon injuries of the fingers. Radiographics. 2002 Mar-Apr;22(2):237-56. doi: 10.1148/radiographics.22.2.g02mr11237. PMID: 11896215.
