predicting pathological fracture in femoral metastases using a clinical ct scan based algorithm a casecontrol study background we assessed whether there was a difference in attenuation measurements in hounsfield units hu and geometric distribution of hu between femora with metastatic lesions that fracture and metastatic lesions that did not fracture nor underwent prophylactic fixationmethods nine patients with femoral metastases who underwent ct and developed a pathological fracture were matched to controls all femora were delineated in axial ct slices using a region of interest roi tool the hu within these rois were used to calculate 1 the cumulative hu of the affected over the nonaffected side per slice and presented as a percentage and 2 the cumulative hu accounting for geometric distribution polar moment of hu we repeated the analyses including cortical bone only hu of 600 and aboveresults ctbased calculations did not differ between patients with a lesion that fractured and those that did not fracture nor underwent prophylactic fixation when analyzing all tissue however when including cortical bone only the pathological fracture group had a lower cumulative hu value compared to the no fracture and no fixation group for the weakest crosssectional ct image pathological fracture group mean 71 sd 23 and no fracture and no prophylactic fixation group mean 85 sd 18 p 0042 and the complete lesion analysis pathological fracture group mean 78 sd 21 and no fracture and no prophylactic fixation group mean 92 sd 15 p 0032conclusion the demonstrated ctbased algorithms can be useful for predicting pathological fractures in metastatic lesions