Although the precise etiology for TF in most cases remains elusive, risk factors associated with TF include genetic predisposition, presence of a systemic metabolic condition (eg, diabetes mellitus), and an inciting mechanical irritation of the tendon-A1 pulley interface (eg, repetitive power gripping activities).[2,3] TF is caused by thickening of the A1 pulley or flexor tendon that disturbs the flexor tendon gliding at the tendon-A1 pulley interface. Although some studies have suggested that the onset of TF could be caused by performing ipsilateral carpal tunnel release, recent evidence refutes this. Zhang et al conducted a retrospective review of 1,386 hands that underwent carpal tunnel release. They found no difference in the onset of new TF before or after CTR, with TF seen in 10.6% of patients within 1 year before CTR and 5.8% of patients within 1 year after CTR.
Schreck et al demonstrated the utility of an animation glove for assessing how TF affects the dynamic hand function. This comparison of dynamic measurements in healthy fingers and those with known TF showed joint velocity to be a reliable parameter for assessment of TF. They found that normal peak extension and flexion velocity of the index and long fingers was highest at the metacarpophalangeal (MCP) joint and slowest at the distal interphalangeal joint. Patients with TF had a notable decrease in the maximum velocity of the proximal interphalangeal (PIP) joint in both flexion and extension.
The efficacy of surgery relies on the precise knowledge and anticipation of anatomy based on the surface landmarks (Figure 1). Fiorini et al sought to define an optimal incision for predictably allowing access to the proximal edge of the A1 pulley. They conducted a cadaveric study of 280 fingers and found that the distance between the digital-palmar and PIP creases corresponds with the distance between the digital palmar crease and the proximal edge of the A1 pulley in the palm. They concluded that this should be used as a surface landmark intraoperatively. Gnanasekaran et al conducted an anatomic study to identify palmar surface landmarks that could help locate the A1, A2, oblique, and variable annular (Av) pulleys of the thumb. The Av pulley is found between A1 and the oblique pulley. Names were assigned to the palmar thumb creases (ie, proximal palmar crease [PPC] at the MCP joint, the distal palmar crease over the middle of the proximal phalanx, and the distal crease at the interphalangeal joint). They reported that the proximal edge of the A1 pulley was 2 mm proximal to the PPC, and the distal edge of the A1 pulley was 3 mm distal to the PPC. The proximal Av and oblique pulleys were 8 and 16 mm distal to the PPC, respectively. The proximal edge of the A2 pulley was 3 mm proximal to distal crease. Precise placement of the incision over the A1 pulley of the thumb and careful technique are critical to avoid injury to the radial digital nerve, which may pass obliquely beneath the incision (Figure 2).
A, Illustration showing the anatomic and surface landmarks for surgical exposure. B, Photograph of three incision techniques for trigger finger release: longitudinal (left), oblique (middle), and transverse (right). A, Reproduced with permission from Smith AA, Zidel P. Tendinopathies, in Weiss APC, Goldfarb CA, Hentz VR, Raven RB, Slutsky DJ, Steinmann SP, eds. Textbook of Hand & Upper Extremity Surgery. Chicago, IL, American Society for Surgery of the Hand, 2013, pp 670–705. B, Courtesy of Arnold-Peter C. Weiss, MD, Providence, RI.
Illustration showing the vulnerability of the digital nerves of the thumb during incision of the A1 pulley. (Reproduced with permission from Smith AA, Zidel P. Tendinopathies, in Weiss APC, Goldfarb CA, Hentz VR, Raven RB, Slutsky DJ, Steinmann SP, eds. Textbook of Hand & Upper Extremity Surgery. Chicago, IL, American Society for Surgery of the Hand, 2013, pp 670–705.)
J Am Acad Orthop Surg. 2020;28(15):e642-e650. © 2020 American Academy of Orthopaedic Surgeons