When fabricating a Rancho-style hand orthosis, where should the thumb post be terminated?

The termination of the thumb post at the mid-finger nail bed is an important design consideration for a Rancho-style hand orthosis because it allows for optimal functional positioning of the thumb. This placement ensures that the thumb can achieve a pinch grip, which is essential for proper hand function and dexterity.

By terminating the thumb post at the mid-finger nail bed, the orthosis provides a mechanical advantage, facilitating active and passive movements of the thumb and allowing for a more natural alignment during grasping and pinching tasks. Additionally, this design can help to stabilize the thumb while permitting movement at the metacarpophalangeal and interphalangeal joints, which is critical for a wide range of activities that require fine motor skills.

In contrast, terminating the thumb post at the wrist joint would limit thumb mobility and not support pinch or grasp function effectively. Stopping at the metacarpophalangeal joint might provide some movement but could restrict the range necessary for optimal grasp. Likewise, terminating the post at the interphalangeal joint could interfere with extension and flexion, further limiting the thumb's functional use. Thus, the mid-finger nail bed is the ideal location for balance between support and mobility in a Rancho-style hand orth