Session VIII - Pediatrics/Spine

Histopathology of Growth Plate Fractures

John A. Ogden, MD; Timothy M. Ganey, PhD, Atlanta Medical Center, Atlanta, GA

Purpose: Detailed analysis of the actual patterns of histologic failure in spontaneous physeal fractures.

Methods: Skeletal components were obtained from children who were either fatally injured or had sustained traumatic amputations. Skeletal material from immature large zoo animals with spontaneous fractures was also obtained. A total of 53 human and 71 animal physeal fractures involving extremities and vertebrae were available for detailed study by morphology, radiography and histology.

Results: All patterns of Salter-Harris fractures as well as the additional types 6 through 9 patterns described by Ogden were evident in the specimens. The majority of the specimens fit the classic description of a fracture at the interface of hypertrophic physis and the metaphysis. However, the fracture often undulated into different layers of the hypertrophic zone. Propagation of the fracture transversely under the Thurston Holland fragment caused potential instability to this fragment ischemic. Some fractures separated the germinal side of the physis from the ossification center. These "wrong side" fractures rendered the physis ischemic. This latter pattern may be a factor in Type5 injuries. Incomplete Type 1 fractures were found with intact periosteum. These were often associated with more obvious metaphyseal fractures. Type 3 and 4 fractures often had more extensive comminution than suspected radiographically. Epiphyseal cartilage and intraosseous hemorrhage compatible with bone bruising were found. These specimens strongly supported the concept of occult trauma, in that many instances of bone bruising are indeed condyle-osseous separations that are not going to be obvious radiographically.

Discussion: This detailed study corroborates the classic concepts of physeal metaphyseal separation in growth plate fractures but also demonstrates additional fracture patterns that are not part of the normal concept of injury. These latter patterns are extremely helpful in understanding the patients who undergo complications of growth plate fractures. This study is the first large-volume study of actual spontaneously occurring physeal fractures and supports the previous radiologically based Salter-Harris System.

The histopathologic variations help to explain children who have significant skeletal injury without obvious radiographic abnormality.