What Causes Scabs At The Point Of Screws In Ankle?

10 weeks following surgery to fix a broken right ankle spiral fracture, there are scabs directly above where 3 of her 10 screws were installed. Could her walking boot be too tight, or what might cause this?

Wife is a 50 yr old woman in good health, 5'4" height and 138lbs bodyweight. Never any prior orthopedic surgeries; she only had 1 surgery for appendicitis when she was 13 years old.