Stenosing tenosynovitis, commonly known as trigger thumb, is a condition causing pain and difficulty when bending or straightening the thumb. It occurs when the smooth gliding of the tendon that controls thumb movement is impeded, leading to a catching or locking sensation. For many individuals, conservative management is the first step toward relief. This non-surgical approach frequently involves using a specialized splint to support the thumb and reduce irritation.
Understanding Trigger Thumb and the Role of Splinting
The pathology of trigger thumb involves a size mismatch between the flexor tendon and the sheath that surrounds it. The flexor pollicis longus tendon can develop inflammation and a thickening on its surface. This swollen area struggles to pass smoothly through the A1 pulley, a fibrous band at the base of the thumb.
The resulting friction causes the characteristic clicking, catching, or locking sensation, often referred to as “triggering.” Splinting works by preventing the active flexion of the thumb that forces the thickened tendon to catch at the A1 pulley. By immobilizing the thumb, the splint gives the inflamed tendon and its sheath the necessary rest to allow swelling to decrease. This period of reduced mechanical irritation restores the proper gliding mechanism, eliminating the painful triggering.
Classifying Splint Options
Splints designed for trigger thumb are categorized based on which joint they are intended to immobilize or restrict. One option is the Distal Interphalangeal (DIP) joint splint, which restricts movement at the thumb’s outermost joint to prevent full tendon flexion. A second category includes the Proximal Interphalangeal (PIP) joint splints, which target the middle joint of the thumb.
Both DIP and PIP splints are often smaller, low-profile designs, sometimes resembling simple rings. A third option is the Metacarpophalangeal (MCP) joint blocking splint, which immobilizes the large joint at the base of the thumb where it meets the palm.
These splint options are available as either prefabricated, over-the-counter devices or as custom-fabricated splints. Custom splints are often made from thermoplastic material molded specifically to the patient’s hand. Prefabricated splints are typically made from materials like neoprene or plastic and come in various adjustable sizes.
Identifying the Recommended Splint Design
Research indicates that the MCP joint blocking splint is the most effective design for treating trigger thumb. This splint works by blocking the flexion of the large knuckle joint at the base of the thumb, often positioning it at a slight extension of 10 to 15 degrees. By restricting movement at this specific joint, the splint prevents the flexor tendon from being pulled forcefully against the inflamed A1 pulley.
The evidence suggests this design is superior to splints that immobilize the smaller thumb joints, showing success rates around 77 percent. Crucially, this design allows the patient to retain functional movement in the smaller thumb joints and the rest of the hand. This significantly improves comfort and compliance, as patients can still perform daily tasks like gripping and pinching with minimal obstruction.
The materials used often include custom-molded low-temperature thermoplastic, which provides a rigid and perfectly fitted support. Many effective prefabricated models use sturdy plastic or neoprene with a firm internal stay to maintain the restricted position. The splint’s efficacy relies on its ability to completely prevent the thumb from flexing at the large knuckle, providing the necessary mechanical rest to the tendon unit.
Proper Application and Treatment Duration
For optimal results, the wearing schedule for the MCP blocking splint focuses on periods of rest, especially at night. Nighttime splinting is highly recommended because many people unconsciously flex and trigger their thumb while sleeping, which aggravates the condition. Wearing the splint during the day is also advised during activities known to cause symptoms, such as heavy gripping or prolonged repetitive tasks.
The splint should be applied snugly enough to prevent the MCP joint from bending. It must not be so tight that it causes numbness, tingling, or discoloration of the thumb, which indicates compromised circulation. A proper fit is confirmed when the thumb joint remains straight even when the hand attempts to form a fist. Consistency is paramount, and the splint should be worn as prescribed for the duration of the conservative treatment period.
The typical treatment timeline is approximately six weeks, though some patients may need to continue splinting for up to ten weeks until all symptoms have resolved. If there is no significant improvement after six weeks of consistent splint use, consult a healthcare provider. Persistent or worsening symptoms may indicate the need for alternative treatments, such as a corticosteroid injection or a surgical release of the A1 pulley.