Injuries to the finger flexor tendon (FT) pulleys require the correct imaging protocol for assessment. Determining how to diagnose -- and treat -- an injury to such a delicate and critical anatomical structure requires a multidisciplinary approach as well as different imaging modalities, according to a new European Journal of Radiology article.
A team of authors headed by Dr. Hicham Bouredoucen of the Division of Radiology in the Department of Imaging and Medical Informatics at Geneva University Hospitals in Geneva, Switzerland, offered an analysis in EJR of injuries to the fingers’ FT pulleys: the dynamics of the finger’s FT pulleys, how injury most commonly occurs, and recommended imaging protocol as guidance for diagnosing these injuries.
Finger positions used by climbers. Crimping position (a, b): The DIP joint is hyperextended, the PIP joint is flexed, the MCP joint is extended, and the wrist is extended. This position places high stress on the cartilage and pulley system. Suspended or extended position (c, d): The PIP, DIP, and MCP joints are flexed, while the wrist may be flexed, neutral, or extended. This position increases stress on the tendons, joint capsule, and ligaments. Semi-arched position (e, f): Increasingly recommended because it reduces mechanical stress. Stacked finger position (g): In this grip, shear stress is exerted on the MCP and PIP joints as well as on the connexus intertendineus of the extensor tendons. Single-finger grip (h): The DIP joint is flexed, the other joints are extended, and the MCP joints of the adjacent fingers are maximally flexed, increasing the tensile load on the “active” finger through the quadriga effect. Underhand grip (i). Lock or jam (j): This grip involves sliding the fingers into a crack. Pincer grip (k): In this grip, the thumb acts as an opponent while the long fingers adopt a semi-arched position. DIP, distal interphalangeal joint; PIP, proximal interphalangeal joint; MCP, metacarpophalangeal joint.Bouredoucen et al; EJR
The finger FT pulleys stabilize the finger tendons during flexion by keeping tendons in the proper proximity to the phalanges. The ruptures and tears to the FT pulleys are often known as “climber’s finger,” as FT pulley injuries are ubiquitous in the sport of rock-climbing, due to the stresses the hands are subject to.
The authors used a structured narrative literature review on the imaging of finger flexor pulley injuries in climbers to determine the optimal methodology for imaging these injuries. Following a description of the functions and anatomy of FT pulleys, the authors reviewed how such injuries occur, in both rock-climbing and everyday activities, as these biomechanics inform the approach.
Any imaging assessment of suspected finger FT pulley injuries should begin with x-rays, the authors wrote, to rule out fractures or avulsions of the volar plate. In the case of adolescents, epiphyseal fractures must also be ruled out via x-ray.
Ultrasound examination using the counter-flexion technique. To assess for rupture of the A2 pulley, the probe is positioned over the proximal phalanx to evaluate the distance between the flexor tendon and the bone. With the proximal interphalangeal joint flexed to 20° and the distal interphalangeal joint flexed to 40°, the examiner applies resistance against the patient’s finger, which performs an active counter-flexion movement.Bouredoucen et al; EJR
Dynamic ultrasound is the gold standard for diagnosis in FT pulley injuries, according to Bouredoucen et al. It allows for real-time examination of the tendons in motion and permits clear visualization of the pulleys. This approach enables measurement of tendon-to-bone distances, as well as detection of indirect signs of FT pulley rupture, such as “bowstringing” (an increase in the distance between the tendon and the bone) and flexor tendon sheath effusion. The authors review features of normal and ruptured pulleys, and how to distinguish features for diagnosis using ultrasound.
They also added that ultrasound is the essential modality for distinguishing flap irritation phenomenon (FLIP), in which a torn pulley fragment has become incarcerated beneath the flexor tendon. FLIP can prevent tendon repositioning, and may also cause chronic tenosynovitis, which may necessitate secondary surgical repair.
Indirect signs of A2 pulley rupture on MRI.(a) Schematic illustration. (b) Sagittal and (c) axial proton density fat-saturated (PD FS) MRI. (d) Axial T1-weighted MRI. Findings include increased tendon-to-bone distance (double-headed blue arrow), fluid effusion within the tendon sheath (yellow arrow), deep fluid collection surrounding the tendons (asterisk), and perilesional edema superficial to the tendon (orange arrow). On the axial PD FS (c) and T1-weighted (d) images, direct visualization of the A2 pulley rupture is limited, but tendon-to-bone separation is clearly visible on both sagittal and axial views (double-headed blue arrow).Bouredoucen et al; EJR
However, if neither x-rays nor dynamic ultrasound are sufficient for diagnosis of this type of injury, the next line of imaging should be MRI, according to the authors, which they say is “a valuable tool for understanding biomechanical mechanisms, diagnosing ligamentous injuries, and assessing microtraumas related to repetitive or extreme finger movements.”
MRI allows for assessing the tendon–bone distance and detailed analysis of structures, including the volar plate. Moreover, direct visualization of the pulleys is facilitated with the use of high-field MRI, they added.
Finger in flexion against resistance. Combined complete rupture of the A3 and A4 pulleys. (a) Schematic illustration. (b) Sagittal proton density fat-saturated (PD FS) MRI. Fluid effusion (asterisk) and increased distance between the flexor tendon and the volar plate at the level of the joint (double-headed blue arrow) confirm injury to the A3 pulley. Fluid effusion (asterisk) and separation between the middle phalanx (P2) and the tendon (double-headed blue arrow) indicate additional injury to the A4 pulley. Note the edematous infiltration of the A3 and A4 pulleys located superficial to the flexor tendons (orange arrows).Bouredoucen et al; EJR
Finally, the authors discussed treatment approaches. Treatment of these injuries is based on the severity, which is graded from I to IV, with IV being the most severe, and incorporating multiple pulley ruptures. These Grade IV injuries often require surgical management (usually due to “bowstringing” or FLIP), although the authors have argued that the evidence points to subdivisions within Grade IV, which may require different surgical approaches, or in some cases, the conservative treatments used for the lower grades of injury. Here, again, the authors have emphasized the value of multidisciplinary approach in the diagnosis and management of these FT pulley injuries, for the best patient outcomes.
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