Correlation of 99mTc-MDP scintimetry and histology in cervical hip fracture

The Role of Bone Scintigraphy in Predicting Femoral Head Collapse following Cervical Fractures in Children

Bone scintigraphy was performed before or after osteosynthesis or both in 11 children aged 9 to 14 years with femoral neck fractures. The role of bone scintigraphy in predicting development of femoral head necrosis with subsequent collapse was studied. Scintigraphy was not a useful study for this purpose. The explanation of this may be that reposition and osteosynthesis jeopardize the blood supply to the femoral head and invalidates the findings at the pre-operative scan. The childhood femoral head also has a strong potential for revascularization and complete reconstruction of the necrotic bone.

Low Field Magnetic Resonance Imaging of Femoral Neck Fractures

Fourteen patients with cervical hip fractures were treated with internal fixation using titanium screws. The femoral head vitality was evaluated with 99Tcm-MDP scintigraphy and scintimetry within 2 weeks postoperatively and by serial low field magnetic resonance imaging (MR). Two patients with reduced radionuclide uptake (femoral head ratio <1.0) developed radiographic signs of femoral head necrosis. MR disclosed the definite area of the necrosis at 2 and 12 months after fracture, respectively. In three of the patients with a high scintimetric uptake (femoral head ratio ≥1.0), MR revealed a focal decrease of the signal intensity in the femoral head or neck at 2, 3 and 7 months after fracture, respectively. The radiographs in one of these patients were normal at 7 months after fracture. The second one showed signs of necrosis at 16 months and the last one developed delayed/non-union. With a non-ferromagnetic osteosynthesis the healing course after femoral neck fracture can be studied with low field MR equipment without disturbing artifacts. The time period between ischaemia and definite abnormalities on MR may embrace several months.

Intracapsular hip pressure after femoral neck fracture

A consecutive series of 34 patients with femoral neck fractures was included in a prospective study aimed at evaluating preoperative variations in intracapsular pressure after changes in hip position, hip traction, and aspiration of hemarthrosis and their influence on the development of femoral head necrosis. Patients were observed for 7 years after surgery. Before aspiration, the mean intracapsular pressure in the antalgic physiologic position was 44.4 mm Hg. There were no differences between displaced and undisplaced fractures. The pressure was a maximum (mean value, 124.8 mm Hg) with the hip in extension and inward rotation, this pressure being greater than the blood systolic pressure in most cases. Hip traction of 3 kg in the antalgic physiologic position was found to be highly effective in preventing any bone flow tamponade effect in displaced and undisplaced femoral neck fractures: the mean intracapsular pressure decreased to 28.5 mm Hg. Aspiration of the hemarthrosis induced a significant decrease in intracapsular pressure only in cases with impaired vascularity of the femoral head as measured by scintigraphy using 99mTc labeled methyldiphosphonate. Aspiration of the hemarthrosis therefore is indicated only in the above cases, although it is less effective than hip traction in the antalgic position. There was no significant correlation between intracapsular pressure and the scintigraphy ratio. Avascular necrosis of the femoral head was detected in six cases. Among these, five patients had an intracapsular pressure below their diastolic blood pressure. This could indicate that vascular damage related to the fracture could be an important cause of bone necrosis despite that blood supply can be decreased by a tamponade effect.

Distribution of 99mTc-phosphate compounds in osteonecrotic femoral heads

We examined the distribution of 99mTc-MDP in 12 late-stage nontraumatic necrotic femoral heads by autoradiography and compared this to the histology of adjacent sections. A widespread fibrocartilaginous metaplasia, and enchondral ossification was observed in the demarcation zone. The highest uptake of the isotope was seen at the provisional calcification in areas with enchondral ossification in the demarcation zone. We concluded that the uneven distribution of 99mTc-MDP was mainly due to the remodeling processes.