Association of Geometric Factors and Failure Load Level With the Distribution of Cervical vs. Trochanteric Hip Fractures

Abstract

We experimentally studied the distribution of hip fracture types at different structural mechanical strength. Femoral neck fractures were dominant at the lowest structural strength levels, whereas trochanteric fractures were more common at high failure loads. The best predictor of fracture type across all failure loads and in both sexes was the neck-shaft angle.Introduction: Bone geometry has been shown to be a potential risk factor for osteoporotic fractures. Risk factors have been shown to differ between cervical and trochanteric hip fractures. However, the determinants of cervical and trochanteric fractures at different levels of structural mechanical strength are currently unknown. In addition, it is not known if the distribution of fracture types differs between sexes. The aim of this experimental study on excised femora was to investigate whether there exist differences in the distribution of cervical and trochanteric fractures between different structural mechanical strength levels and different sexes and to identify the geometric determinants that predict a fracture type. Materials and Methods:The sample was comprised of 140 cadavers (77 females: mean age, 81.7 years; 63 males: mean age, 79.1 years) from whom the left femora were excised for analysis. The bones were radiographed, and geometrical parameters were determined from the digitized X-rays. The femora were mechanically tested in a side impact configuration, simulating a sideways fall. After the mechanical test, the fracture patterns were classified into cervical and trochanteric. Results: The overall proportion of cervical fractures was higher in females (74%) than in males (49%) (p ‫ס‬ 0.002). The fracture type distribution differed significantly across load quartiles in females (p ‫ס‬ 0.025), but not in males (p ‫ס‬ 0.205). At the lowest load quartiles, 94.7% of fractures in female and 62.5% in males were femoral neck fractures. At the highest quartiles, in contrast, only 52.6% of fractures in females and 33.3% in males were cervical fractures. Among geometric variables, the neck-shaft angle was the best predictor of fracture type, with higher values in subjects with cervical fractures. This finding was made in females (p < 0.001) and males (p ‫ס‬ 0.02) and was consistent across all failure load quartiles. Conclusions: Femoral neck fractures predominate at the lowest structural mechanical strength levels, whereas trochanteric fractures are more common at high failure loads. Females are more susceptible to femoral neck fractures than males. The best predictor of fracture type across all structural strength levels and both sexes was the neck-shaft angle.

Femoral neck shaft angle width is associated with hip-fracture risk in males but not independently of femoral neck bone density

“…This follows the biomechanical concept that the wider the femoral NSA the higher the bending moment at the FN and the higher the impact force imposed on the FN, which results in a greater probability of fracture. 19,21,27,28 Therefore, the ability of NSA to predict hip fracture in males independent of BMD was examined. It was found not only that FN-BMD was the best hip fracture predictor in males but also that NSA does not predict hip fracture independent of FN-BMD.…”

“…7,8 This evidence, however, mainly derives from studies carried out in females, 9-13 whereas contradictory results characterize studies carried out in males. [14][15][16][17][18][19][20] Authors' opinions seem to vary widely about the ability of the neck shaft angle (NSA), one of the PFG factors, to predict osteoporotic hip fractures in males, [14][15][16]21 whereas its association with the risk of hip fracture in females 10,11,14,22 is generally accepted. Gender differences in the hip anatomy 23 have been put forward as a possible explanation for the different relationship of NSA with the hip-fracture risk between genders, whereas geographic and racial differences 24 among the examined male populations have been advocated as a possible cause of authors' discrepancies on the relationship between NSA and the hip-fracture risk in males.…”

In vivo discrimination of hip fracture with quantitative computed tomography: Results from the prospective European Femur Fracture Study (EFFECT)

“…(49) Trochanteric fractures also have been shown to be associated with increased mortality when compared with cervical fractures, and this could not be explained by differences in age or comorbidity. (4) Since there is evidence in both in vitro (14,15,42,47,50) and in vivo (3,30) studies that cervical and trochanteric fractures have different risk factors, we compared densitometric and geometric variables between the two subgroups and analyzed hip fracture discrimination separately for each subgroup. Compared with cervical fracture cases, we found lower DXA aBMD and QCT BMD values in trochanteric fracture cases, but differences were not statistically significant.…”

“…These results are in agreement with current knowledge that women with trochanteric fractures have a more severe and generalized low bone density involving particularly the trabecular component, with lower aBMD in the trochanteric region and lumbar spine. (51) Cervical fractures seem to depend more on proximal femur or pelvic geometry (such as a larger femoral neck shaft angle or a longer hip axis length in cervical fractures (2,3,30,50) ) combined with focal bone loss. (51) In the EPIDOS study, aBMD values of novel upper and lower femoral neck subregions were lower in trochanteric fractures than in controls, but prediction of cervical fractures was improved by measuring aBMD only in the upper subregion of the femoral neck.…”

Vitamin D Levels, Physical and Biochemical Characteristicsof South East Asian Patients with Osteoporotic Hip Fractures

“…Previous studies have shown that the structural and material properties of the proximal femur determine the type of hip fracture. 1,2 Patients with trochanteric hip fractures have been found to have lower serum vitamin D levels compared to patients with femoral neck fractures. 3 Apart from studies done involving Caucasians, there is a paucity of information on other populations about the relationship of vitamin D levels and hip fracture subtypes; the interplay between 25(OH)D, intact PTH (iPTH), calcium and phosphorus; the impact of renal insufficiency; and the effect of premorbid ambulatory status on hip fracture type.…”