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E2209. Imaging Evaluation of Finger Flexor Pulley Injuries in Rock Climbers
Authors
  1. Paulo Miro; University of Arizona College of Medicine Phoenix
  2. Eric vanSonnenberg; University of Arizona College of Medicine Phoenix
  3. Dylan Sabb; University of California – Davis, Department of Family & Community Medicine
  4. Volker Schöffl; Section of Wilderness Medicine, Department of Emergency Medicine, University of Colorado School of Medicine; Section Sportsorthopedics and Sportsmedicine, Department of Orthopedic and Trauma Surgery, Klinikum Bamberg
Background
Rock climbing has increased in popularity steadily over the last two decades. The proposed debut of rock climbing in the 2021 Tokyo Summer Olympics will further accelerate its growth as a sport. Consequently, climbing-related injuries have, and will continue to become more common. Climbers are uniquely susceptible to injuries of the finger flexor pulley system due to the sport’s bio- mechanical demands. Injuries of the pulley system are otherwise rare, rendering them often difficult to diagnose.

Educational Goals / Teaching Points
Our objective is to synthesize recent literature and provide current concepts in the imaging evaluation of finger flexor pulley injuries, while also reviewing anatomy, bio-mechanics, prevention, and treatment strategies pertaining to these injuries.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
The second through fifth digits contain five annular pulleys (A1-A5) and three cruciate pulleys (C1-C3). The pulleys function primarily to prevent excessive volar displacement of the flexor digitorum profundus and flexor digitorum superficialis away from the phalanges, a phenomenon termed “bowstringing”. The “crimp grip” position, defined as flexion of the PIP at 90 degrees with the DIP joints maximally hyperextended, places high levels of stress on the flexor tendons, and consequently, the pulleys. This results in overuse injuries ranging from simple strains to complete ruptures that involve several pulleys. Ultrasound (US) is the initial imaging technique of choice, and MRI is recommended as an additional study if US is inconclusive. On US, the flexor tendons appear as hyperechoic fibrillar structures, while the appearance of the pulleys is variable due to anisotropy. The distance between the flexor tendons and phalanges, termed the tendon-to-bone distance, is used in both US and MRI as an indirect marker of finger flexor pulley injuries and disruption. Specifically, a tendon-to-bone distance > 2mm on ultrasound provides a 98% sensitivity and 99% specificity for diagnosis of A2 and A4 pulley ruptures, and a volar plate to tendon distance > 0.9mm provides a 76% sensitivity and 94% specificity for A3 pulley ruptures. 3T MRI with dedicated surface coils allows for the highest resolution imaging of the digits. Transverse images, using gadolinium-enhanced and fat-saturated T1 weighted sequences, provide the best visualization of the finger flexor pulley system. The use of the “crimp grip” positioning during MR evaluation enhances the sensitivity and specificity of pulley injury diagnoses.

Conclusion
Finger flexor pulley injuries are largely unique to rock climbers. US and MRI are essential for accurate diagnosis and prognosis.