“Rufus” was a 6 month old, male Labrador retriever who had fallen down a flight of stairs 24 hours earlier and was non-weight bearing on the left pelvic limb - palpation of the limb did not elicit pain and no evidence of soft tissue swelling was noted - lateral and caudocranial views of the affected stifle joint were made plus a ventrodorsal view of the pelvis. Radiographic diagnosis - a type 1 Salter-Harris fracture was evident in the proximal tibia with only minimal displacement of the fragments - the widening of the physeal growth plate suggests fragment displacement - the metaphysis was shifted slightly in a medial direction (white arrow) creating a small stair-step displacement - note that the apophyseal growth center of the tibia crest is attached to the proximal tibial epiphysis and the two move together - an incomplete fracture of the proximal fibula was noted supporting a diagnosis of trauma (black arrow) - the usually evident fascial planes just caudal to the stifle joint are not identified suggesting periarticular hemorrhage/edema - the infrapatellar fat pad could be readily identified on the original film using a bright light suggesting that joint effusion and capsular distention was not present suggesting an intra-articular injury was not present - the pelvic radiograph was normal without hip joint laxity or secondary joint disease that would have suggested hip dysplasia and thus ruled out this likely diagnosis in a dog of this age.Comparison of the lateral view with a radiograph made of another 6-8 month old puppy permits determination of how the growth areas in the proximal tibia should appear at this age and shows the minimal separation of the proximal epiphysis in the trauma patient - the radiologist was confident of the diagnosis in this patient and did not radiograph the opposite limb - I believe it should be a rule to always make the comparison radiograph of the opposite limb in a patient this age - the opposite limb is the best comparison study to use. In another patient, a type II Salter-Harris physeal fracture shows the separation of the proximal epiphysis with the adjoined ossification center of the tibial crest but with the fracture line extending into the metaphysis. In another 6 month old dog, the injury was of a different type with the patellar ligament causing avulsion of the tibial crest but leaving the proximal tibial epiphysis in position - this injury can occur at a stage prior to the tibia crest fusing with the proximal tibia epiphysis - the comparison with the normal joint in this patient clearly demonstrates the nature of the injury.
