This is called a hematoma. Autopsies of children who have died from multiple injuries, including being beaten on the buttocks, show old, deep scarring of the muscles along with the fresh bleeding from the most recent beating. Medical reports document well the injuries that occur to the lower spine of adults from forces applied there by accidental direct blows, falls and blows sustained in car accidents. Bruising of the tailbone the coccyx, causes coccydynia, a persistent pain in the tailbone. Direct blows to the buttocks can fracture the sacrum, the large bone at the lowermost part of the spine.
Many nerves pass through the sacrum to innervate the pelvic area.
So profuse are the nerves at the end of the spinal cord that they are called the cauda equina , or the horse's tail. These nerves supply motor function and sensation to the bladder, the rectum, the genitals and the legs. Tearing of these nerves by a fracture of the sacrum causes problems with bladder and bowel function, such as an inability to empty the bladder and lax rectal tone, which causes soiling. Such fractures of the sacrum are often not suspected because proper x-rays are not taken. Thus far, doctors have paid little attention to the injuries to the spines of children that might occur from paddlings.