Osteoporotic hip fractures include FNFs and ITFs, and these fractures are extremely common in the elderly population [10]. However, many differences have been reported between FNFs and ITFs, such as etiology, risk factors, and patient characteristics [1]. Pulkkinen et al. [17] reported that FNFs predominate at the lowest structural mechanical strength levels, whereas ITFs are more common at high failure loads, and females are more prone to FNFs than males. Recent studies revealed that the PFG parameters can show the susceptibility to hip fractures independent of BMD [5]. But, here, there were no statistically significant differences in age and gender between the FNF and ITF groups (p=0.40 and p=0.59, respectively).
Lee et al. [5] analyzed the PFG parameters among 16 premenopausal women with minimal-trauma hip fractures and 80 age- and body mass index-adjusted controls. They revealed that a long hip axis and narrow NSA significantly increased fracture risk in a multiple logistic regression analysis using only the PFG parameters. They revealed that the HAL and NSA were BMD-independent predictors of hip fracture and hip geometry might be clinically useful for the identification of patients for whom active fracture prevention should be considered [5]. Han et al. [10] evaluated 197 women aged 65 years or older who had an osteoporotic hip fracture (FNF, 84 patients; ITF, 113 patients). A total of 551 women who visited the hospital to be tested for osteoporosis were included in the control group. The researchers measured the femur BMD and PFG parameters for all subjects and compared them between the control and fracture groups. They reported that there were no significant differences in the HAL and NSA between the control group and the fracture group. In our study, there were no significant differences between the FNF and ITF groups according to the HAL and NSA in the multivariate analysis, so our study revealed no significant relationship between the HAL or NSA and hip fracture type.
Hu et al. [4] reported that the mean HAL of 101 patients with FNFs was 118.23 ± 8.73 mm, and the HAL of 97 patients with ITFs was 119.97± 10.29 mm. In our study, the mean HAL of 33 patients with FNFs was 123.5 ± 14.9 mm, and the HAL of 81 patients with ITFs was 119.3 ± 12.3 mm, but there were no statistically significant differences. We found that the hip axis was longer in the FNF group than in the ITF group, which contrasts the results from the study by Hu et al [4].
Hu et al. [4] found that the mean NSA of the 101 patients with FNFs was 137.63 ± 4.56°, and the mean NSA of the 97 patients with ITFs of the femur was 132.07 ± 4.17°, which was significantly different. They suggested that a greater NSA was a risk factor for FNF [4]. In our study, the mean NSA of 33 patients with FNFs was 140.12 ± 7.83°, and the NSA of 81 patients with ITFs of the femur was 139.55 ± 9.17°, but there were no statistically significant differences between fracture type.
Han et al. [10] showed that femoral neck length (FNL) was significantly greater in the control group than in the FNF group (P<0.001). However, there were no statistically significant differences in the FNL between the control group and the ITF group (P=0.722). In addition, they reported that the FNL between both fracture groups was significantly shorter in the FNF group than in the ITF and control groups [10]. Lu et al. [18] reported that the FNAL of patients with ITFs of the femur was 90.68 mm, which was greater than that of the FNF group (88.64 mm). From the biomechanical point of view, the longer axis of the femoral neck causes the greater trochanter of the femur to protrude more, and thus, the possibility of ITF increases when an external force impacts the femoral trochanter. The long axis of the femoral neck and the high risk of proximal femoral fractures have been defined by most scholars [18]. The FNAL has an important role in internal fixation of the proximal femoral fracture and hip arthroplasty. Therefore, restoration of the normal FNAL prior to fracture has important clinical significance for accurate restoration of the normal hip geometric parameters and can improve hip function. In our study, the FNAL was longer in patients with femoral neck fractures (104.1 ± 11.1 mm) than in patients with ITFs (102 ± 9.9), but there were no statistically significant differences between fracture type.
Han et al. [10] revealed that the femoral neck width (FNW) in the control group was significantly smaller than that in the FNF and ITF groups. However, we found no significant differences in the FNAL and FND between the two groups in our study. They reported that after adjusting for age, weight, and height, the odds ratio (OR) for fractures in the FNF group increased depending on a decrease in the FNAL, cross-sectional area (CSA), and femur BMD and an increase in the FNW. Furthermore, they revealed that the OR for fractures increased depending on a decrease in the CSA in the femoral neck and femur BMD and an increase in the FNW in the ITF group [10]. They suggested that an increase in the FNW might be a PFG parameter that plays a significant role as a risk factor for fracture independent of BMD.
Hu et al. [4] evaluated 198 elderly patients over 65 years of age with hip fractures (FNF, 101 patients; ITF, 97 patients). They reported that the CEA were higher in men than in women. Also, they revealed that there was no statistically significant difference in CEA between the gender, but greater CEA was the risk factor for ITFs. In here, CEA was larger in woman than in men and CEA was greater in ITF group than in the FNF group, compatible with the literature.
Hu et al. [4] showed statistically significant differences in the NSA between the FNF group and the ITF group. They revealed that a greater NSA was a risk factor for FNF. In our study, the FNF group had a greater NSA when compared to the ITF group, compatible with the literature. Also, they revelaed that FND is greater in FNF group than the ITF group, with a statistically significant difference [4]. They claimed that greater FND was a protective factor for the ITF group. In our study, FND was greater in the FNF group than the ITF group, without statistically significant difference.
In our study, the FNF group had larger NSAs, smaller CEAs, larger FHDs and FNDs, smaller FSDs, and greater FNALs and HALs compared to the ITF group. The FNF group had smaller NHRs, NHLR, and FSDs compared to the ITF group. There were no statistically significant differences in the PFG parameters between the FNF and ITF groups except in the NHLR (0.86 ± 0.03 vs 0.84 ± 0.03, p=0.05).
The limitation of this retrospective study is because of not having height, weight and BMI of the patients, the measurements could not be normalized.
In conclusion, we evaluated the differences in geometric morphological parameters of the proximal femur in different hip fracture types and gender. Only the NHLR was significantly higher in the ITF group, so this study revealed that a higher NHLR, which is the presence of a longer hip axis combined with a shorter neck axis, is a risk factor for ITF after a minor trauma.