Regaining thumb tip motion after a crush injury requires the middle part of the thumb to be blocked, transferring forces into the tip of thumb. This forces the tip to work, instead of moving the middle of the thumb. In this splinting, the rubber band tension allows the patient to straighten his thumb, but returns the thumb to a bent resting position – this encourages tissue growth.
Ligaments in the wrist are positioned in a specific amount of tension, minimizing lateral motion and controlling how much it can bend or flex to create an optimum balance during healing.
A crushed finger can result in stiffness: after the swelling is mostly gone, the tissue contracts and shortens. In this example, the line of pull is helping to provide a low tension comfortable stress – this sets up the environment so a longer chain of tissue can grow, leading to increased flexibility so the patient can get back to gripping.
This dynamic extensor tendon orthotic splint supports a finger whose tendon has been lacerated and sewn back together. To prevent the sewn ends from pulling apart during healing, an external elastic line of pull is made that unloads the action of the healing tendon, allowing the finger to actively bend in a controlled short arc with the elastic line straightening the finger.
This low-profile static orthotic helps to prevent stiffness in a healed fracture. Such fingers are usually quite stiff. Control of swelling prior to splint application allows the tissue over the joint to get lengthened proportionately. Tissue changes often require this type of assistive device; just trying to make a fist or simply pushing the finger into a fist pattern does not allow the tissue to grow.