Final answer:
Advanced Orthogonal is the chiropractic technique that uses a percussive stylus instrument for upper-cervical adjustments.
Step-by-step explanation:
The technique that uses a percussive stylus instrument to deliver an upper-cervical adjustment is known as Advanced Orthogonal. This technique is distinct from other methods such as Flexion Distraction, Toggle-recoil, and NUCCA, which utilize different mechanisms to achieve spinal adjustments. The cervical vertebral column allows for extensive ranges of motion due to the orientation of the articular processes in the neck. However, in techniques like Advanced Orthogonal, precise instruments are utilized to ensure proper alignment without excessive force.