Tear of the Flexor Pulley of the Finger

A 47-year-old status post rock climbing injury of his finger. Now has deformity of the palmar aspect of the finger with flexion. What is the diagnosis?

Figure 1. What is abnormal in this digital image?

A. Sagittal image of finger in flexion. B. Axial image of finger. C. Sagittal image of finger in extension.

Figure 2. ABNORMAL FINGER

A. Sagittal image of finger in flexion. The flexor tendon is bow stringed with respect to the proximal phalanx. (yellow arrow)

B. Axial image of finger. There is a tear of the A1 pulley with retraction of the pulley fibers dorsally. The flexor digitorum superficialis tendon is split down the middle and mildly subluxed peripherally. Notice the marked soft tissue edema and tenosynovitis surrounding the flexor tendon. (green arrow)

C. Sagittal image of finger in extension. The flexor tendon is less bow stringed with respect to the proximal phalanx when extended. (red arrow)

Figure 3. NORMAL FINGER

A. Sagittal image of the normal adjacent finger in flexion. Notice that the flexor tendons hug the palmar surface of the proximal phalanx. (yellow arrow)

B. Axial image of the normal adjacent finger in flexion. Notice that the flexor tendons hug the palmar surface of the proximal phalanx. (green arrow)

C. Sagittal image of the normal adjacent finger in extension. The flexor tendons hug the palmar surface of the proximal phalanx. (red arrow)

Figure 4. Diagram of the normal digital flexor pulley system. Diagram from: https://theclimbingdoctor.com/pulley-injuries-explained-part-1/

Figure 5. Diagram of the normal digital flexor pulley system.

Figure 6. Diagram of the digital flexor pulley system with a tear of the A2 and A3 pulleys.

Figure 7. Intraoperative images of patient in Figure 1-3. A. First picture shows torn pulley. B. Palmaris graft harvested. C. Graft dorsal to bone and volar to extensor. D. Final picture tied down.

Figure 8. Rock climbing with the crimp grip. Note the extension of the MCP joints, flexion of the PIP joints, and extension of the DIP joints. When using the crimp grip rather than an open hand grip, the force on the A4 pulley increases 3.9 times and the force on the A2 pulley increases 31.5 times.

Discussion:

The flexor tendons of the finger travel through a fibro-osseous tunnel along the palmar aspect of the fingers. The fibrous portion of the canal includes five annular pulleys which are perpendicular to the long axis of the tunnel and are separate areas of thickening of the tendon sheaths. There are also three cruciform pulleys which crisscross fibers of the annular pulleys. The annular pulleys are named A1 through A5 and the cruciate pulleys are named C1 through C3. The A1 pulley originates in the palmar plate of the metacarpal phalangeal joint and extends to the base of the proximal phalanx and is intimately related to the metacarpal phalangeal joint. The A2 pulley originates along the volar proximal aspect of the proximal phalanx and spans the distance to the distal third of the proximal phalanx. The A3 pulley spans over the proximal interphalangeal joint, A4 is located palmar to the mid aspect of the middle phalanx, while the A5 pulley spans the DIP joint.

The main role of the annular pulleys is to stabilize the tendon sheaths to the phalanges. The function of the pulley system is to prevent bowstringing of the tendons on finger flexion. One analogy is the eyelets of a fishing rod. Flexor injuries are commonly encountered during forced extension on a flexed finger such as occurs when using the “crimp grip” during rock climbing. In fact, the crimp grip transfers 31.5 times more force on the A2 pulley than an open-hand grip. (Fig 8.) Flexor pulley injuries have also been reported in bowling, baseball and other sports. MRI is the main imaging method, however ultrasound is playing an increasingly important role in evaluation due to the possibility of dynamic assessment. All A2 and most A4 pulley ruptures require surgical repair in order to regain function. A1, A3 and A5 pulleys may be initially managed conservatively.

References and further reading:

1. Singh AP. Flexor Tendon Pulley System of Hand. http://boneandspine.com/flexor-tendon-pulley-system-of-hand/

2. Whitney Lowe W.Flexor Pulleys of the Fingers. Massage Today May, 2010, Vol. 10, Issue 05 http://www.massagetoday.com/mpacms/mt/article.php?id=14209

3. Awh MH. Pulley Lesions of the Fingers. http://radsource.us/pulley-lesion-of-the-fingers/

4. Rock Climbers and Pulleys. http://musculoskeletalmri.blogspot.com/2011/05/rock-climbers-and-pulleys.html

5. Rubin DA, Kneeland JB, Kitay GS, Naranja RJ. Flexor Tendon Tears in the Hand: Use of MR Imaging to Diagnose Degree of Injury in a Cadaver Model. AJR 1996;166:615-620

6. Drape J, et al. Closed ruptures of the flexor digitorum tendons: MRI evaluation. Skeletal Radiology 1998;27:617-624.

7. Clavero JA, Alomar X, Monill JM, et. al. MR Imaging of Ligament and Tendon Injuries of the Fingers. RadioGraphics 2002 22:2, 237-256

8. Lin GT, Amadio PC, An KN, Cooney WP. Functional anatomy of the human digital flexor pulley system. J Hand Surg [Am ]1989; 14:949–956.

9. Crowley TP. The Flexor Tendon Pulley System and Rock Climbing. J Hand Microsurg (2012) 4: 25.

10. Zafonte, Brian et al. Flexor Pulley System: Anatomy, Injury, and Management. Journal of Hand Surgery ,2014, Volume 39 , Issue 12 , 2525 - 2532

11. Bianchia S, Martinoli C, de Gautarda R, et. al. Ultrasound of the digital flexor system: Normal and pathological findings. J Ultrasound. 2007 Jun; 10(2): 85–92.

11. Vigouroux L, Quaine F, Labarre-Vila A, Moutet F-O. Estimation of finger muscle tendon tensions and pulley forces during specific sport-climbing grip techniques. J Biomech. 2006;39:2583-2592. doi:10.1016/j.jbiomech.2005.08.027

12. Pulley Injuries in Fingers. http://bouldersuk.com/2013/11/pully-injuries-fingers/

Phillip Tirman, MD is the Medical Director of Musculoskeletal Imaging at the Renaissance Imaging Center in Westlake Village, California. A nationally recognized expert in the applications of MRI for evaluating MSK and spine disorders, Dr. Tirman is the co-author of three textbooks, including MRI of the Shoulder and Diagnostic Imaging: Orthopedics. He is also the author or co-author on over sixty original scientific articles published in the radiology and orthopedic literature.

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Kevin M. Rice, MD is president of Global Radiology CME and serves as the Chief of staff and Chair of the Radiology Department of Valley Presbyterian Hospital in Los Angeles, California and is a radiologist with Renaissance Imaging Medical Associates. Dr. Rice's passion for state of the art radiology and teaching includes acting as a guest lecturer at UCLA. Dr. Rice co-founded Global Radiology CME with Natalie Rice to provide innovative radiology education at exciting international destinations, with the world's foremost authorities in their field. In 2016, Dr. Rice was nominated and became a semifinalist for a "Minnie" Award for the Most Effective Radiology Educator.

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