The study included 51 young people, ranging in age from 10 to 17 years old. Triplane fractures, (fracture lines occur in three planes of the ankle) account for about 6%-10% of ankle fractures in young people, says Stephen D. Brown, MD, instructor in radiology at Harvard Medical School in Boston. They are generally sports-related injuries, he added.
All 51 cases showed bone separation along the front part of the growth plate of the tibia. There were 33 "classic" two-fragment fractures as seen in medical textbooks, but the "classic" three fragment fracture (which involves a separation at Kump's bump) "was not seen in this series," said Dr. Brown, lead author of the study. Three fragment fractures were seen, but they involved different fracture patterns than what has been previously described as most common, said Dr. Brown. In fact, the study found that fully half of the triplane fracture patterns described in the literature - some of which have been described as quite common - likely occur only very rarely or never at all. This is explained by the characteristic pattern of closure of the growth plate. In addition, "the medial malleolar variety of triplane fracture previously considered rare, was very common," he said. "In one-fourth of the patients in our cohort, fractures involved the medial malleolus, but spared the plafond," he said.
This new information clarifies the anatomy of these complex multidimensional fractures allows physicians to describe these fractures more uniformly, and will help facilitate the partnership between radiologists who diagnose these fractures and the orthopedic surgeons who treat them, Dr. Brown said. The study proposes using a common classification scheme - the Salter-Harris system - to help describe the appearance of these fractures in each different dimension as depicted by CT with multiplanar reconstruction.
"This is the largest published series on these types of fractures to date, and is the first one in which all fractures were imaged and analyzed using multiplanar CT," said Dr. Brown. The study is published in the November issue of the American Journal of Roentgenology.
A PDF of the full study is available upon request to reporters.