A long opponens splint, also known as a forearm-based thumb orthosis, is a device providing support to the forearm, wrist, and thumb. It can be custom-molded by a therapist or come prefabricated. The design immobilizes the wrist and specific thumb joints to hold the hand in a functional position, while permitting the other fingers to move freely.
The Connection to C5 Spinal Cord Injury
A spinal cord injury at the C5 level impacts nerves controlling the shoulder and bicep muscles, leaving wrist and hand muscles without nerve input. This allows for bending the elbows and raising the arms, but not actively extending the wrist. Consequently, the wrist falls into a flexed position called “wrist drop,” making it difficult to use the hand for grasping.
The muscles that move the thumb away from the palm, a motion called opposition, are also paralyzed. The thumb then rests against the side of the index finger, closing the web space between them. This posture severely limits the ability to hold onto objects.
The long opponens splint addresses these functional losses by providing external support for the wrist and thumb. This creates a stable foundation for the hand, allowing the individual to use their active shoulder and elbow movements more effectively for tasks.
Primary Functions of the Splint
The “long” component extends from the forearm to the hand to immobilize the wrist. It is set in a position of slight extension, with the wrist bent slightly backward. This positioning prevents the non-functional “wrist drop” posture. Maintaining this angle also helps prevent contractures, which are permanent shortenings of muscles or tendons.
The “opponens” part of the splint addresses the thumb. It is molded to hold the thumb in abduction, meaning it is out and away from the palm. This keeps the web space open, which is needed to grasp objects like a cup or utensil. The splint positions the thumb to act as a passive stabilizer for the fingers to press against.
This wrist and thumb positioning facilitates a tenodesis grasp. Tenodesis is a biomechanical property where finger tendons naturally flex when the wrist is extended. A person with a C5 injury can use their shoulder and bicep muscles to lift their arm, allowing gravity to extend the wrist. The splint holds the wrist in this position, creating tension on the finger flexor tendons and causing the fingers to curl into a light, passive grip for holding items.
Wearing Schedule and Care
A therapist determines the wearing schedule based on the individual’s needs. The splint is often worn during daytime hours to assist with functional activities like eating or writing. It may also be prescribed for nighttime wear to maintain a gentle stretch on the wrist and finger muscles, helping to prevent contractures during sleep.
Proper maintenance is for hygiene and comfort. Most thermoplastic splints can be cleaned with mild soap and lukewarm water. Rinse the splint thoroughly and allow it to air dry completely before wearing it again to prevent skin irritation from trapped moisture.
Regular skin checks are part of the daily routine. Before and after use, inspect the skin for redness, pressure sores, or irritation. The splint should fit securely without digging into the skin or cutting off circulation. If persistent red marks or skin breakdown are noticed, contact the healthcare provider or therapist.