In Neer's classification for impingement syndrome, Type I acromion corresponds to which shape?

In Neer's classification for impingement syndrome, Type I acromion corresponds to which shape?

• A. Hooked acromion
• B. Irregular acromion
• C. Curved acromion
• D. Flat-shaped acromion

Answer: (D)

Neer's impingement classification uses how the acromion sits over the rotator cuff to describe instability and irritation during arm elevation. The flat acromion, with a straight undersurface, maintains the widest subacromial space and is less likely to pinch the rotator cuff compared with the other shapes. In contrast, a curved acromion narrows the space somewhat, and a hooked acromion narrows it the most, increasing impingement risk. So, Type I corresponds to a flat-shaped acromion.

Neer's impingement classification uses how the acromion sits over the rotator cuff to describe instability and irritation during arm elevation. The flat acromion, with a straight undersurface, maintains the widest subacromial space and is less likely to pinch the rotator cuff compared with the other shapes. In contrast, a curved acromion narrows the space somewhat, and a hooked acromion narrows it the most, increasing impingement risk. So, Type I corresponds to a flat-shaped acromion.