Final answer:
A patient needs further instruction post-hip arthroplasty if he believes he should maintain the hip in adduction and internal rotation, as this can lead to dislocation of the new prosthesis.
Step-by-step explanation:
When completing discharge teaching with an 80-year-old male patient who underwent a posterior right total hip arthroplasty, a need for further instruction is identified when the patient incorrectly states that they should maintain the hip in adduction and internal rotation. Post-surgical protocols typically include avoiding adduction (crossing the leg over the midline of the body) and internal rotation to prevent dislocation of the new hip prosthesis. In contrast, the patient should avoid crossing his legs, use a toilet elevator to prevent excessive flexing of the hip, and should indeed notify future caregivers about the prosthesis.