DXA and pQCT predict pertrochanteric and not femoral neck fracture load in a human side‐impact fracture model

Abstract

The validity of dual energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT) measurements as predictors of pertrochanteric and femoral neck fracture loads was compared in an experimental simulation of a fall on the greater trochanter. 65 proximal femora were harvested from patients at autopsy. All specimens were scanned with use of DXA for areal bone mineral density and pQCT for volumetric densities at selected sites of the proximal femur. A three-point bending test simulating a side-impact was performed to determine fracture load and resulted in 16 femoral neck and 49 pertrochanteric fractures. Regression analysis revealed that DXA BMD trochanter was the best variable at predicting fracture load of pertrochanteric fractures with an adjusted R 2 of 0.824 (p < 0.0001). There was no correlation between densitometric parameters and the fracture load of femoral neck fractures. A significant correlation further was found between body weight, height, femoral head diameter, and neck length on the one side and fracture load on the other side, irrespective of the fracture type. Clinically, the DXA BMD trochanter should be favored and integrated routinely as well as biometric and geometric parameters, particularly in elderly people with known osteoporosis at risk for falls. Keywords: osteoporosis; femur fracture; BMD; pQCT; DXA Hip fractures are a cause of significant morbidity and mortality worldwide and are a substantial economic burden.1,2 About 54% of women aged 50 years or older will have an osteoporotic fracture during their lifetime. Furthermore, approximately 4% of the patients older than 50 years with a hip fracture die in the hospital and 24% die within 1-year after the hip fracture. 4 Thus, the prevention of osteoporotic femur fractures is of increased significance to reduce morbidity and mortality on the one hand and socio-economic burden on the other hand.At present, areal bone mineral density (aBMD) as obtained from dual energy X-ray absorptiometry (DXA) is the best established clinical parameter for diagnosis and follow-up of osteoporosis. 5,6 It is widely used as a predictor of fracture risk of the hip although there is considerable overlap in the densitometry measurements of individuals who have fractured and those who have not. 7 In addition, over the past years the measurement of volumetric bone mineral density (vBMD) by peripheral quantitative computed tomography (pQCT) gained more and more interest in the field of basic research. Several ex vivo studies indicate that vBMD measured by pQCT has the highest predictive value for mechanical strength of cancellous bone of the proximal and diaphyseal femur. [8][9][10] In this context, there is little data available comparing the predictive value of areal and volumetric BMD measuring techniques on the mechanical strength of the proximal human femur. Moreover, recent publications comparing the predictive value of different bone density measuring techniques on the femoral fracture strength significantly vary for the me...

The role of entry point and correct reduction in post-operative outcome of intertrochanteric femur fractures treated by short and long proximal femoral nails

“…That may be the reason, there were no cases of lag screw cut out and 2 cases of z-effect (figure 7) due to varus reduction which was determined in follow up by analysing post-op x-ray showing neck shaft angle <150 degree and severe osteoporotic bone but there was no case of reverse z-effect in our follow up patients. Bone mineral density (BMD) of the trochanteric region obtained in DEXA scan is the best indicator for predicting pertrochanteric fractures [28] . The highest concentration of stress is usually at the lag screw hole of the intramedullary implant [28] .…”

“…Bone mineral density (BMD) of the trochanteric region obtained in DEXA scan is the best indicator for predicting pertrochanteric fractures [28] . The highest concentration of stress is usually at the lag screw hole of the intramedullary implant [28] . The angle of insertion of a nail during surgery is a very important factor because stress on nail and bone distal to tip of nail depends on the angle of insertion [29] .…”

Comparison of Short vs Long Anti-rotation in Treating Trochanteric Fractures

“…It would be wonderful if one could identify a particular group of elderly patients who were vulnerable to sustain fragility fractures around the hip. It has been shown that bone mineral densitometry (BMD) of the trochanteric region of femur, obtained using a dual energy X-ray absorptiometry (DXA), is the best indicator for predicting pertrochanteric fractures 11 . The mean force required to cause a pertrochanteric fracture is 3107+/−1066 N, however this value was arrived at, without considering other factors such as fall biomechanics and concomitantly acting muscular forces around the hip joint 11 .…”

The Impact of Coronal Configuration of the Proximal Femur on its Mechanical Properties and the Validation of a New Theoretical Model: Finite Element Analysis and Biomechanical Examination

“… 4 Many anatomical indications have been identified as the factors affecting the strength of the proximal femur, in which the bone mineral density of femoral neck is found to be significantly related to the strength of the proximal femur, 5 , 6 , 7 , 8 including the BMD measured by DXA and the densitometric variables measured by QCT. 9 In addition, the geometric variables measured by QCT, 9 the volumetric BMD (vBMD), cross‐sectional area, cortical thickness and large cortical bone hole of tibia, 10 the femoral neck cortical thickness and trabecular bone volume fraction, 11 the total cortical porosity, 12 the diameter of femoral neck, 13 the trochanteric cortical area, femoral neck width, 14 the femoral neck length, femoral head diameter, 15 and the cortical thickness , 16 etc., are also considered as the influencing factors of the strength of the proximal femur. Besides BMD, the other factors mentioned above are very difficult to be altered via clinical intervention.…”