At what angle should the patient's arm be bent for a posteroanterior hand radiograph?

For a posteroanterior (PA) hand radiograph, the patient's arm should be bent at a 90-degree angle. This positioning allows the hand to be properly aligned for capturing the necessary anatomical details. When the arm is at this angle, it helps to position the wrist and hand flat on the imaging receptor without distortion, ensuring that the radiographic view includes the carpal bones, metacarpals, and phalanges in optimal alignment.

At 90 degrees, the forearm is perpendicular to the imaging plate, which enhances the clarity of the resultant image and reduces the likelihood of superimposition from adjacent anatomical structures. This angle is a standard practice to ensure consistency and accuracy when obtaining diagnostic images of the hand.

Other angles would not provide the same level of clarity or might introduce distortion into the image, making it difficult to assess the bony or soft tissue structures accurately.