Background: There are no proven radiographic guidelines for
predicting fracture risk in children and young adults with a benign skeletal
lesion. An in vivo diagnostic study was conducted to determine whether a
reduction in the load-carrying capacity of a bone measured with quantitative
computed tomography was more accurate than current radiographic guidelines for
predicting pathologic fracture in patients with a benign skeletal lesion.
Methods: Eighteen patients who presented with a fracture through a
benign skeletal lesion were compared with eighteen patients who had a benign
skeletal lesion that had been thought to be at increased risk for fracture on
the basis of currently used radiographic criteria but had not fractured over a
two-year period. Structural analysis was performed to calculate the resistance
of the affected bones to compressive, bending, and torsional loads with use of
serial transaxial quantitative computed tomography data obtained along the
length of the bone containing the lesion and from homologous cross sections
through the contralateral, normal bone. At each cross section, the ratio of
the structural rigidity of the affected bone divided by that of the normal,
contralateral bone was determined. The cross section with the greatest
reduction in compressive, bending, and torsional rigidity was identified as
that most likely to fracture.
Results: The mean age (and standard deviation) of the thirty-six
patients was 12.5 ± 3.6 years. Twenty lesions were located in the
femur; eleven, in the tibia; three, in the humerus; one, in the ulna; and one,
in the pelvis. A combination of the minimum bending and torsional rigidities
calculated from the tomographic data provided optimal performance in
differentiating between the fracture and non-fracture groups (100% sensitivity
and 94% specificity). In contrast, plain radiographic criteria demonstrated
28% to 83% sensitivity and 6% to 78% specificity.
Conclusions: The combination of bending and torsional rigidity
measured noninvasively with quantitative computed tomography was more accurate
(97%) for predicting pathologic fracture through benign bone lesions in
children than were standard radiographic criteria (42% to 61% accuracy). We
believe that this method can provide accurate objective criteria for planning
treatment of benign bone lesions and monitoring treatment response.
Level of Evidence: Therapeutic Level III. See
Instructions to Authors for a complete description of levels of evidence.