No abstract

In three cases the CT scan performed 10-25 days after onset of symptoms was interpreted as normal. MR examination performed a few days after the CT scan showed in each of these three patients a fracture line with a band of edema. Scintigraphy was very sensitive, but the H-shaped pattern of sacral uptake, specific for an insufficiency fracture, was detected in only three of 16 cases. The earliest MR sign was medullary edema, seen as early as 18 days after the onset of symptoms. On spin echo (SE) T1-weighted images (T1WI), the hypointense signal of edema could mask a fracture line. On SE T2WI the fracture line could be detected within the hyperintense edema (10 of 17 patients with examinations including SE T2WI). However, in four patients a fracture of the sacrum was not seen on T2WI, these having been obtained in the axial plane. For this reason, intravenous gadolinium was injected, revealing a fracture line in 12 of 14 examinations, or fat suppression sequences were performed, revealing a fracture line in five of five cases. The total number of fractures detected was 17 [15 fractures of the sacrum (bilateral in 10 cases) and two of the acetabular roof]. At a later stage, the edema resolved and the fracture was clearly seen. The two cases of fracture of the acetabular roof were easily recognized at MRI, particularly in the sagittal plane.

Level III.

Growth plate fractures of the distal femur are challenging to treat, with complications that require a secondary surgery 40% to 60% of the time. These fractures often necessitate operative intervention, even in the youngest patients and even with minimal apparent displacement. Treatment varies with the Salter-Harris (SH) classification and with the extent of initial displacement, ranging from simple casting for nondisplaced SH I fractures to open reduction and internal fixation for almost all SH III and IV fractures. Poor outcomes have been associated with pediatric fracture care of SH III and IV in 29% to 32% of cases. There are many pitfalls that have to be avoided in the treatment of these fractures to prevent malunion, growth arrest, and posttraumatic arthritis. CLASSIFICATIONThe standard Salter-Harris (SH) classification works well for these fractures, especially with regard to treatment and risk of growth arrest. The risk of growth arrest is reported to be between 40% and 52% for all distal femur growth plate fractures. 1,2 In a meta-analysis of 564 fractures, growth disturbance occurred in 36% of SH 1 fractures, in 58% of SH 2 fractures, in 49% of SH 3, and in 64% of SH 4 fractures. 1 High-energy distal femur growth plate fractures (eg, motor vehicle accident) have a 31% rate of growth disturbance compared with only a 5% rate for low-energy fractures (eg, fall from <10 ft). 2 Displaced fractures have a higher incidence of complications (49%) compared with nondisplaced fractures (27%). 3 In a retrospective review, the authors recommended subdivision of SH II fractures into those with and without metaphyseal comminution and/or initial displacement >3 mm with loss of contact between the 2 fragments. Those with comminution and displacement had a greater risk of growth arrest (75%) compared with those without (38%). 4 SH INondisplaced SH I fractures should be suspected when knee tenderness is localized circumferentially to the distal femur growth plate. With the knee in full extension, the equator of the patella usually overlies the growth plate, which helps to guide the examination. Gentle varus/valgus stress to the knee should elicit pain. Radiographic findings can be subtle in all minimally displaced growth plate fractures of the knee. A slight fleck of bone adjacent to the growth plate, a slight widening of the physis, or other irregularity of the growth plate can give a hint of a fracture. Sometimes, the only indication that a distal femur fracture has occurred may be the appearance of periosteal new bone formation about the metaphysis 3 weeks after injury. Stress views of the knee have fallen out of favor because of the severe pain experienced by the patient and the potential growth plate damage incurred when redisplacing a nondisplaced fracture. 5 Patients who have tenderness over the growth plate and are unable to bear weight should be FIGURE 1. Authors' preferred method of cross pin fixation for displaced Salter I and II fractures with pins exiting the skin proximally. This prevents the pins from passi...

Not applicable.