Structure of the Femoral Neck in Hip Fracture: Cortical Bone Loss in the Inferoanterior to Superoposterior Axis

Abstract

Although bone mass is a contributory risk factor for hip fracture, its distribution about the femoral neck is also important. Femoral neck biopsies were obtained from 13 females with intracapsular hip fracture (fracture: mean age 74.3 ± 2.3 years [SEM]) and 19 cadaveric samples (control: 9 males and 10 females 79.4 ± 1.7 years) and the areas of cortical and cancellous bone were quantitated in octants. In the control group, although males had larger bones than females, the proportions of cortical and cancellous bone were not different (p > 0.05) between the genders. The total amount of bone, as a proportion of bone + marrow, was significantly reduced in the fractures compared with the female controls (%Tt.Ar: fracture 27.83 ± 1.18, female control 33.62 ± 1.47; p = 0.0054). Reductions in cortical bone area occurred in all regions but particularly in the inferior, inferoanterior, and anterior octants (p < 0.05). There were no differences between cases and controls in the regional amount of cancellous bone (all regions, p > 0.178). Marked reductions in mean cortical bone width between the fracture and female control group occurred in the anterior, inferoanterior (31%), and superoposterior (25%) regions. Representing cortical widths as simple Fourier functions of the angle about the center of area (R 2 adj = 0.79) showed in the cases that there was preservation of the cortical bone in the inferior region, with the proportional loss of cortical bone being greatest in the inferoanterior and superoposterior regions. It is concluded that loss of cortical, rather than cancellous, bone predominates in cases of femoral neck fracture. This loss occurs primarily along the inferoanterior to superoposterior axis. As this axis bears the greatest strain during a fall, it is hypothesized that specific thinning of the cortex in these regions leads to an exaggerated propensity to fracture in those so affected, above that resulting from an equivalent general decrease in bone mass. (J Bone Miner Res 1999;14:111-119)

Bone Microarchitecture of the Talus Changes With Aging

“…At first glance, the nearly unimpaired bone structure of the talar neck seemed contradictory given that the femoral neck has a similar weight-transmitting function and an age-related degradation of the femoral neck was reported [10,12]. Age-related cortical trabecularization and thinning were attributed to a higher risk of hip fracture in the elderly [9,10]. However, talar neck fractures have a low incidence at older age and are primarily seen in patients with a highimpact trauma [25,36].…”

Microvascularization of the hypermineralized calcified fibrocartilage and cortical bone in the sheep proximal femur

“…Since blood vessels appear to be a significant contributor to the health and remodeling of cortical bone, it is hypothesized that the large areas of avascular calcified fibrocartilage present in the elderly femoral neck may predispose these regions to damage accumulation. The morphological properties of the cortical shell have recently been more thoroughly investigated, because of the suspected importance of the cortical shell in the susceptibility of the hip to fracture (Bell et al, 1999(Bell et al, , 2000Vajda and Bloebaum, 1999;Shea et al, 2001). Investigations into the failure mechanisms of hip fractures have observed that a localized loss of cortical bone was the dominant morphological difference between intracapsular hip fracture cases and age-matched post-mortem controls, and that the loss of cancellous bone appeared to be less significant (Bell et al, 1999(Bell et al, , 2000Crabtree et al, 2001).…”

“…The morphological properties of the cortical shell have recently been more thoroughly investigated, because of the suspected importance of the cortical shell in the susceptibility of the hip to fracture (Bell et al, 1999(Bell et al, , 2000Vajda and Bloebaum, 1999;Shea et al, 2001). Investigations into the failure mechanisms of hip fractures have observed that a localized loss of cortical bone was the dominant morphological difference between intracapsular hip fracture cases and age-matched post-mortem controls, and that the loss of cancellous bone appeared to be less significant (Bell et al, 1999(Bell et al, , 2000Crabtree et al, 2001). Regions of generalized cortical bone loss in the femoral neck (the superior-posterior and inferior-anterior regions) in hip fracture cases also correspond to the regions where the fractional area of calcified fibrocartilage is highest (Bell et al, 1999(Bell et al, , 2000Vajda and Bloebaum, 1999).…”

“…Investigations into the failure mechanisms of hip fractures have observed that a localized loss of cortical bone was the dominant morphological difference between intracapsular hip fracture cases and age-matched post-mortem controls, and that the loss of cancellous bone appeared to be less significant (Bell et al, 1999(Bell et al, , 2000Crabtree et al, 2001). Regions of generalized cortical bone loss in the femoral neck (the superior-posterior and inferior-anterior regions) in hip fracture cases also correspond to the regions where the fractional area of calcified fibrocartilage is highest (Bell et al, 1999(Bell et al, , 2000Vajda and Bloebaum, 1999). Further research needs to be conducted comparing patients with hip fractures to gender-and age-matched controls to better elucidate the possible role of calcified fibrocartilage in the dramatic increase in hip fractures with age.…”

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

“…(23) However, there is still controversy about the respective contributions of trabecular and cortical bone compartments to hip fracture risk. Some authors have attributed the exponential increase in hip fracture risk with aging to thinning of the cortex of the neck, (24,25) whereas others suggest a synergistic action and a decline in both cortical and trabecular bone. (26)(27)(28) Mechanical testing of excised femoral necks also has given variable results, ranging from cortical contributions of 40% to 60% (14,26) to almost 100% (29) for overall femoral strength.…”