Stenosing tenosynovitis, commonly known as Trigger Thumb, occurs when the thumb’s flexor tendon sheath becomes inflamed and narrowed. This causes the tendon to catch or lock as it attempts to glide through the tight tunnel, often resulting in a popping sound or a sudden stop in movement. Trigger Thumb is painful and often worsens in the morning or after forceful gripping activities. Non-surgical treatments, including splinting, are typically the first step to reduce pain and restore smooth motion.
The Purpose of Splinting for Trigger Thumb
The primary purpose of applying a splint for Trigger Thumb is to provide targeted rest and prevent the painful catching mechanism. The catching occurs because the flexor tendon, which bends the thumb, develops a nodule or thickening that snags on the A1 pulley, a narrow band of tissue at the base of the thumb. By restricting the thumb’s movement, the splint prevents the inflamed tendon from repeatedly attempting to slide through the constricted pulley.
Immobilizing the joint in a slightly extended position allows the inflammation within the tendon sheath to subside naturally over time. This rest is crucial because repeated triggering exacerbates the irritation and swelling. The goal of the splint is targeted rest, not complete hand immobilization, which allows the rest of the hand and fingers to continue functioning. Reducing the movement that causes the trigger offers the best chance for the tendon and sheath to heal without requiring more invasive treatments.
Understanding the Different Splint Designs
Splints designed for the thumb vary based on which joint they restrict to achieve immobilization. One major category includes splints that restrict the Interphalangeal (IP) joint, the joint closest to the tip of the thumb. These often take the form of small, ring-like orthoses, such as the popular Oval-8 design, which holds the tip of the thumb straight or slightly bent. These splints block the final, most forceful bending of the thumb, which is often when the tendon catches.
Another category restricts the Metacarpophalangeal (MCP) joint, the main knuckle joint where the thumb meets the palm. These splints are generally larger, often extending down onto the palm, and they block the thumb from bending at the knuckle. A third, less common type for isolated Trigger Thumb is the Thumb Spica splint, a larger brace that immobilizes both the MCP joint and the wrist. While a Thumb Spica provides maximum rest, it is often more restrictive than necessary for a condition localized to the flexor tendon sheath.
Choosing the Clinically Recommended Splint
The most effective splint design minimizes the movement that creates the painful friction. Clinical evidence suggests that splints primarily targeting the MCP joint are highly successful, showing positive outcomes in a significant percentage of patients. The MCP joint blocking splint prevents the thumb from bending at the knuckle, which is the point closest to the problematic A1 pulley. This restricted movement reduces the excursion of the flexor tendon through the inflamed sheath while often allowing the IP joint to retain some movement for light function.
Conversely, splints that only block the IP joint, while more comfortable and less restrictive of overall hand function, have shown lower rates of success. The choice of splint must also consider patient comfort and compliance, as a cumbersome splint will not be worn as directed. A well-fitted MCP-blocking splint is preferred because it offers a good balance of effective immobilization and tolerable comfort. The splint must be snug enough to prevent movement but never tight enough to impede circulation or cause skin irritation.
Proper Application and Treatment Duration
The wearing schedule for a Trigger Thumb splint is crucial for successful non-surgical treatment. Healthcare providers often recommend wearing the splint continuously, or at least during the night and for activities that aggravate symptoms. Nocturnal splinting is particularly important because many people unconsciously flex their thumbs in their sleep, which can cause the tendon to catch and increase morning pain and stiffness. The splint should only be removed briefly for necessary hand hygiene and gentle range-of-motion exercises to prevent joint stiffness.
The typical duration for the splinting regimen is generally between six and ten weeks, and improvement can sometimes be seen within the first few weeks of consistent use. Patients with long-standing symptoms or those with diabetes may require a longer treatment period. If symptoms do not improve after this initial period of conservative treatment, or if the locking becomes severe, medical consultation is necessary. Next steps often involve a corticosteroid injection directly into the tendon sheath or, if all other options fail, a surgical release of the A1 pulley.