Trigger finger release surgery involves opening a tight sheath around the flexor tendon to restore smooth finger movement. While the operation is generally successful with a low complication rate, patients occasionally experience structural issues afterward. One complication is digital flexor tendon bowstringing, which occurs when the necessary containment of the tendon is compromised, potentially affecting the finger’s strength and motion.
Defining Digital Flexor Tendon Bowstringing
Bowstringing is a physical phenomenon where the flexor tendon lifts away from the underlying bone during finger flexion. This displacement causes the tendon to protrude visibly and become palpable just beneath the skin. The appearance is similar to the taut string of a drawn bow, which gives the condition its name.
This complication signifies mechanical failure in the finger’s pulley system, which normally holds the tendon close to the bone. The displacement results in an abnormal contour and can create a painful pulling sensation in the palm when the patient actively bends the affected finger.
The Anatomical Mechanism of Bowstringing
The flexor tendons that bend the finger are held in place by fibrous bands called annular pulleys. These pulleys ensure the tendon glides smoothly and efficiently along the phalangeal bones. Trigger finger surgery involves surgically releasing the A1 pulley, located near the palm over the metacarpophalangeal joint.
Bowstringing typically occurs from the unintended compromise of other, more structurally significant pulleys, such as the A2 and A4. These pulleys are crucial for maintaining the tendon’s path and mechanical advantage. If these pulleys are injured, the flexor tendon lifts away from the bone.
This displacement increases the distance between the tendon and the joint’s rotation, known as the flexion moment arm. This change reduces overall efficiency and range of motion, despite a theoretical mechanical advantage. The increased moment arm requires the tendon to travel a greater distance to achieve the same amount of finger bending. Releasing 50% or more of the A2 pulley can significantly lead to this complication.
Impact on Hand Function and Daily Life
The mechanical disadvantage created by bowstringing translates directly into noticeable functional impairment. The most immediate effect is a reduction in grip strength, making it harder to generate a powerful, full fist. Patients often report weakness when trying to hold or squeeze objects due to the increased tendon travel distance.
The altered biomechanics also limit the finger’s full range of motion. The overall excursion of the tendon is less effective, resulting in a reduction of total composite flexion. This makes simple, fine motor tasks difficult, such as buttoning a shirt or picking up small coins. Abnormal force transmission can also lead to muscle fatigue and cramping.
Management and Prognosis
The treatment pathway depends on the severity of the bowstringing and the specific pulleys involved. For milder cases or partial injuries, conservative management is the first approach. This typically involves a supervised hand therapy program focused on strengthening and range-of-motion exercises. Splinting may also be incorporated to provide external support and prevent further displacement.
If the bowstringing is severe, causes significant functional loss, or involves the A2 or A4 pulleys, surgical revision may be necessary. This involves a pulley reconstruction procedure. During surgery, the surgeon uses a tendon graft to create a new, functional pulley.
This reconstructed pulley restores the normal anatomical relationship, anchoring the flexor tendon back down to the bone. Prognosis is generally favorable, especially with prompt detection and intervention, as successful reconstruction can restore near-normal function and eliminate the visible bowstringing.