Fibrous sheaths of digits of hand - Upper extremity - Muscles of upper limb - e-Anatomy
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Fibrous sheaths of digits of hand

Vaginae fibrosae digitorum manus

Definition

Muhammad A. Javaid

The fibrous sheaths of the digits of the hand form fibro-osseous tunnels on the palmar aspect of the fingers, enclosing the flexor digitorum superficialis and flexor digitorum profundus tendons. Each fibrous sheath is composed of annular (A) pulleys and cruciate (C) ligaments, which together maintain tendon alignment and prevent bowstringing during finger flexion.

Annular (A) Pulleys

  • There are five A pulleys (A1–A5) in each finger.

  • A1, A3, and A5 are joint pulleys attached to the volar plates of the MCP, PIP, and DIP joints, respectively.

  • A2 and A4 arise from the periosteum of the proximal and middle phalanges.

  • Together, they form a continuous tunnel of the fibrous sheath of each digit.

  • In the thumb, there are two annular pulleys and one oblique pulley serving a similar function.

Cruciate (C) Ligaments

  • Three cruciate pulleys (C1–C3) lie between the annular pulleys.

  • Their crossed fibres offer flexibility, allowing the fibrous sheaths of digits of hand to collapse and expand smoothly during finger movement.

Function

The annular pulleys and cruciate ligaments of the fibrous sheaths of digits of hand constrain the long flexor tendons close to the bone prevent bowstringing during finger flexion.

Clinical Note

Thickening or inflammation at the A1 pulley leads to trigger finger (stenosing tenosynovitis).

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.

  • Bianchi, S., Martinoli, C., De Gautard, R. and Gaignot, C., 2007. Ultrasound of the digital flexor system: normal and pathological findings. Journal of Ultrasound, 10(2), pp.85-92.

  • Makkouk, A.H., Oetgen, M.E., Swigart, C.R. and Dodds, S.D., 2008. Trigger finger: etiology, evaluation, and treatment. Current reviews in musculoskeletal medicine, 1(2), pp.92-96.

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