National Physical Therapy Examination (NPTE) Practice Exam

What is the typical consequence of a ruptured central slip in the finger extensors?

1. Flexion at the distal interphalangeal joint

2. Hyperextension at the proximal interphalangeal joint

3. Full extension at the metacarpophalangeal joint

4. Loss of ability to flex the digits

The correct answer is: Hyperextension at the proximal interphalangeal joint

When there is a rupture of the central slip, which is part of the extensor mechanism in the finger, the typical consequence is hyperextension at the proximal interphalangeal joint (PIP joint). The central slip functions to extend the middle phalanx at the PIP joint. When it is ruptured, there is an inability to effectively extend this joint. Consequently, the extensor muscles can no longer maintain proper alignment, leading to a situation where the PIP joint tends to hyperextend due to the unopposed action of the flexor tendons, particularly in the context of a finger that is not properly extended. In this scenario, while the distal interphalangeal joint might be flexed, the characteristic deformity presented is the hyperextension at the PIP joint, which can ultimately result in a condition referred to as "boutonnière deformity." This condition underscores the importance of the central slip in maintaining normal finger extension and stability, especially during functional activities.