Trigger thumb (stenosing tenosynovitis) is a common condition characterized by difficulty smoothly extending the thumb. The primary symptom is a noticeable catching, clicking, or locking sensation when the thumb attempts to straighten after being bent. This guide focuses on identifying the optimal splinting solution to manage this painful restriction.
Understanding the Mechanics of Trigger Thumb
Trigger thumb occurs due to a size mismatch between the flexor tendon and the sheath it slides through. The flexor pollicis longus (FPL) tendon runs through a fibrous tunnel secured by a series of pulleys. The A1 pulley, located near the base of the thumb in the palm, is the structure most commonly implicated in this condition.
Inflammation causes the tendon sheath to thicken and the tendon itself may develop a small nodule. This swelling creates friction as the tendon attempts to glide through the narrowed A1 pulley. The mechanical blockage results in the characteristic popping or clicking sensation. Patients often experience tenderness and pain localized to the area of the A1 pulley, which sits at the metacarpophalangeal (MCP) joint.
How Immobilization Relieves Trigger Thumb Symptoms
Splinting provides mechanical rest for the inflamed tendon and pulley system. The core function of an effective splint is to prevent the repetitive, high-friction movements that aggravate the A1 pulley. By restricting the range of motion, the splint minimizes the gliding distance of the flexor tendon.
This restriction reduces the rubbing of the swollen tendon against the constricted pulley, which is the direct source of inflammation and pain. Minimizing this friction allows the swelling in the tendon and the pulley to subside over time. Splinting facilitates the body’s natural healing process by keeping the affected structures in a resting position.
Comparing Splint Designs
The most effective splint design targets the joint nearest the pathology: the metacarpophalangeal (MCP) joint. An MCP joint splint works by immobilizing the main knuckle of the thumb in a slightly straightened position. This design is highly recommended because the A1 pulley, the site of the problem, sits directly over the MCP joint. Restricting movement at the MCP joint prevents the triggering action, yet it allows the tip of the thumb (the interphalangeal, or IP, joint) to remain free. The goal is to stop the movement that causes the tendon to catch while maintaining as much hand function as possible.
Alternative splint designs, such as a distal interphalangeal (DIP) joint splint, which only immobilizes the tip of the thumb, are less effective. These distal splints fail to adequately restrict the movement at the MCP joint where the primary friction occurs. They do not address the mechanical issue at the A1 pulley as directly as the MCP blocking splint.
A third option, the full thumb spica splint, immobilizes the entire thumb and often a portion of the wrist. This design provides maximum rest by fully restricting all thumb movement. However, this level of restriction is often unnecessary for mild to moderate trigger thumb and can significantly interfere with daily activities. A physician may recommend this design only for severe cases or those unresponsive to less restrictive splints.
Regardless of the design, the material and fit are important for effectiveness and patient comfort. Splints made from rigid thermoplastic material offer the necessary stability to maintain the joint position. A properly fitted splint ensures that the immobilization is maintained without causing excessive pressure or skin irritation, which encourages consistent wear.
Practical Guidelines for Splint Therapy
Consistent wear is paramount to the success of non-surgical splint therapy. The typical protocol involves wearing the splint primarily at night and during activities that are known to cause triggering or pain. Many healthcare providers suggest wearing the splint for a minimum of six weeks, and sometimes up to ten weeks, to allow sufficient time for the inflamed tissues to heal.
During this period, the splint should be kept clean, and the skin underneath should be regularly inspected for irritation or pressure sores. The splint should be removed several times a day for gentle, full-range-of-motion exercises of the thumb and hand, as directed by a therapist or physician, to prevent joint stiffness. It is also important to wash the skin and the splint according to the manufacturer’s directions to maintain hygiene.
If symptoms of catching, locking, or pain persist after a defined period of consistent splint use, typically six weeks, medical follow-up is necessary. Persistent symptoms may indicate that the inflammation requires a more aggressive approach, such as a corticosteroid injection into the tendon sheath. If both splinting and injections fail to resolve the condition, a surgical release of the A1 pulley may be considered.