Final answer:
The incorrect technique when fitting and using a walker is having the patient's feet 12 to 18 inches behind the back legs of the walker.
Step-by-step explanation:
The incorrect technique when fitting and using a walker is D. When fitting the walker, the patient's feet should be 12 to 18 inches behind the back legs of the walker. This is not a recommended practice as it can lead to an improper stance and potentially decrease the stability of the walker. Instead, the patient should stand within the walker with their hands on the grips. The top of the walker grip should line up with the crease in the wrist when the arms are at the side, which is correct technique A. Additionally, the elbows should have a 15-degree bend when the hands are on the grips as stated in B, to provide effective support without straining the joints. Wearing shoes during fitting as mentioned in C, is also correct to ensure an accurate height adjustment and comfort while walking with the walker.