Ex Vivo Evaluation of Hip Fracture Risk by Proximal Femur Geometry and Bone Mineral Density in Elderly Chinese Women

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

OBJECTIVE

This study aims to establish the coronal configuration of the proximal femur as an independent factor for its mechanical properties and provide validation for the theoretical model "fulcrum-balance-reconstruction."

METHODS

The digital 3D femur model constructed with the lower extremity high-resolution computed tomography of a senior subject was applied with the axial compression of 2100N under 5 different α angles of 10°, 5°, 0°, -5°, -10°. The equivalent stress distribution of the femoral geometric model under each angle were calculated. Under the same five α angles, fatigue test was performed on 15 composite artificial left femurs (three specimens in each angle group) to obtain the failure cycle and fracture site. The statistical analysis was accomplished using One-Way ANOVA.

RESULTS

The maximum stress of the entire femur in physiological angle (α = 10°) occurred below femoral neck with a value of 63.91 MPa. When the proximal femur is in extreme abducted angle (α = -10°), the maximum stress shift to the lower medial cortex of femoral shaft with a value of 105.2 MPa. As the α angle changed from 10° to -10°, the greater trochanteric region had the largest increment in maximum stress (2.78 times for cortex and 1.67 times for cancellous bone) locally at the proximal femur. The failure cycles of the artificial femurs with a variety of abduction angle were averagely 9126 ± 2453.87 (α = -10°), 58,112.33 ± 1293.84 (α = -5°), 92,879.67 ± 2398.54 (α = 0°), 172,045.3 ± 11011.11 (α = 5°), and 264,949.3 ± 35,067.26 (α = 10°), and the statistical analysis revealed that the α angle of the group of concern is proportional to the P value of the corresponding group compared to the 10° group(α = 5° & α = 10°, P = 0.01; α = 0 & α = 10°, P = 0.001; α = -5°, -10° & α = 10°, P < 0.001). In fatigue test, the fracture appeared on femoral neck for the α angles of 10° (three subcapital), 5° (two basal; one transcervical), and 0° (one transcervical). Fracture sites located at trochanteric region were observed with the more abducted angles including 0° (two subtrochanteric) and -5° (two intertrochanteric; one subtrochanteric). The fracture line was only found on femoral shaft in the -10° group.

CONCLUSION

With increasing hip abduction, the proximal femur shows declining mechanical properties, which suggests higher risk of hip fracture and increasement in the fraction of trochanteric fracture subtype. Furthermore, the hypothesis of "fulcrum-balance-reconstruction" was validated by our study to a certain extent.

Biomechanical study of extramedullary and intramedullary fixation in the treatment of unstable intertrochanteric reversed-tilt fractures of the femur

Background

To investigate the efficacy of the 135° hip screw, 95° intramedullary hip screw (IMHS) and 95° hip screw in the treatment of intertrochanteric reverse dip fracture of the femur.

Methods

We retrospectively analyzed 125 matched pairs of human femurs (median age 64 years) which were osteotomized at a 33° angle in the left femur and extended downward from the minor trochanter to simulate a reverse oblique intertrochanteric fracture. The right femur served as a control. The left femur (n=4) was implanted with a 135° hip screw, 95° hip screw, or IMHS. A strain detector was placed distal to the fracture site to monitor fragment strain. The lateral displacement of the proximal femur was measured by a linear variable differential transformer. An Instron tester measured stiffness, strain, and lateral displacement at 25° adduction, and 90° adduction with vertical loads on the femoral head. A 2 cm gap was then formed at the fracture site to simulate comminution and the mechanical test was repeated.

Results

Before the formation of the gap, there was no significant difference in stiffness among different bone structures (P>0.05), but after the formation of the gap, the stiffness of all the adduction structures decreased (P=0.03), and the difference in adduction was statistically significant (135° hip screw: 46.6%±3%; 95° hip screw: 22.9%±2%; IMHS: 53.7%±7.8%; P<0.05). Similar results were found for the abduction and buckling positions. There was no significant difference in the lateral displacement of the gap before (P=0.92) and after (P=0.26), but a significant difference in the failure load was found (135° hip screw: 1,222±560 N; 95° hip screw: 2,566±283 N; IMHS: 4,644±518 N; P=0.02).

Conclusions

There was no statistically significant difference in stiffness among different structures (P>0.05). However, in the presence of gaps, IMHS bone implant structures are much stiffer than 135° and 95° structures and have a greater destructive load.

Bone mineral density of proximal femur in adult Chinese females

OBJECTIVE

This study was designed to establish bone mineral density (BMD) reference data of proximal femur, research the effect of age, height and weight on BMD of proximal femur, and estimate the prevalence of osteoporosis in a Chinese female population. In addition we compared the results with Lebanese and USA white women reference data.

METHODS

Our study was conducted at one center, including 1578 Chinese women, aged 20-79years. We measured the BMD for proximal femur using dual-energy X-ray absorptiometry, and then established a reference database of proximal femur and set up regression equations of age, height and weight for BMD at proximal femur to research the effects of age, height and weight on BMD. After that, we calculated the standardized BMD and compared them with Lebanese and USA white women reference data.

RESULTS

The peak BMD occurred in the age range 30-39 years for femoral neck and Ward's triangle, and 40-49 years for trochanter in Chinese women, which were later than in Lebanese and USA white women. The BMD of proximal femur in Chinese women were lower than Lebanese and USA white women in most age ranges. Weight profoundly influenced BMD in all age groups, and age and height mainly effected BMD in older age groups. The standardized prevalence of osteoporosis among Chinese women of 50-79 years old was 9.6% in femoral neck, which was higher than Lebanese but lower than USA white women.

CONCLUSION

The BMD database of proximal femur in Chinese women we established is normative and different from Lebanese and USA white women reference data, which provides more reliable information on the prevalence of osteoporosis in China.

The Evaluation of Bone Mineral Density based on Age and Anthropometric Parameters in Southeast Chinese Adults: A Cross-Sectional Study

BACKGROUND Osteoporosis is a chronic skeletal disease characterized by a reduction in bone density, resulting in high death rates and high costs among patients worldwide. This study investigated the associations among age, anthropometric parameters and bone mineral density (BMD) in southeast Chinese adults and evaluated the characteristics of southeast Chinese adults at high risk of osteoporosis. MATERIAL AND METHODS This study enrolled 424 female and 265 male volunteers. Height, weight and BMD were measured, and body mass index (BMI) was calculated. Based on their BMD T-scores, female and male participants were divided into groups with osteoporosis (OG1) and osteopenia (OG2) and a normal group (NG). RESULTS The findings revealed no significant correlations between BMD and anthropometric parameters in either gender. However, a significant negative correlation was noted between BMD and age in the female participants, and a significant positive correlation was observed between BMD and age in the male participants. Multiple comparisons between groups revealed that women in the OG1 and OG2 groups were significantly older than those in the NG group. CONCLUSIONS Age, anthropometric parameters and BMD correlate differently between groups and genders in southeast Chinese adults.

Comparison of hip subregion bone mineral density to the type of proximal femur fracture

Beta values of the intertrochanteric fracture group were about twice as high as those of the femoral neck fracture group. These results can be used to increase the awareness of proximal hip fracture among physicians and improve treatments and outcomes.

PURPOSE

To compare the BMD of the femoral neck region and the intertrochanteric region between the femoral neck fracture group and the intertrochanteric fracture group.

METHODS

We did a retrospective review of radiographs of the proximal femoral fractures in patients registered from 2010 to 2017. A total of 329 patients were classified into the femoral neck fracture group (group A, n = 162) and the femur intertrochanteric fracture group (group B, n = 167). We did intergroup comparisons of age, sex, BMI (body mass index), and bone mineral density (BMD) of the neck and intertrochanteric region, adjusting for age. We did multiple logistic regression analysis among these parameters.

RESULTS

The BMD of the femoral neck and intertrochanteric was statistically significantly different between the two groups (p < 0.001), and the BMD of the femur intertrochanteric was also significantly different between the two groups (p < 0.001). BMD of both regions in the intertrochanteric fracture group was lower than that of the femoral neck fracture group. In linear regression analysis, the beta values of the intertrochanteric fracture group were about twice as high as those of the femoral neck fracture group.

CONCLUSION

In linear regression analysis, the beta values of the intertrochanteric fracture group were about twice as high as those of the femoral neck fracture group.

Vitamin D Deficiency/Insufficiency Is Associated with Risk of Osteoporotic Thoracolumbar Junction Vertebral Fractures

Background

The association between serum vitamin D level and vertebral fracture (VFx) remains controversial. The purpose of this study was to determine whether serum 25-hydroxy vitamin D (25(OH)D) level is associated with osteoporotic thoracolumbar junction VFx in elderly patients.

Material/Methods

From Jan 2013 to Dec 2017, this retrospective case-control study included 534 patients with primary osteoporotic thoracolumbar junction VFx (T10–L2) and 569 elderly orthopedic patients with back pain (without osteoporotic VFx) as controls. Serum 25(OH)D levels were measured and the association with osteoporotic VFx was analyzed. Other clinical data, including BMI, comorbidities, and bone mineral density (BMD), were also collected and compared between these 2 groups.

Results

It was shown that 25(OH)D levels were significantly lower in patients with T10–L2 VFx than in control patients. Among 534 VFx patients, 417 (78.1%) patients showed grade 2–3 fracture. Serum 25(OH)D levels were significantly related to affected vertebral numbers and VFx severities. The VFx risk was 28% lower (OR=0.72, 95% CI 0.62–0.83) per increased SD in serum 25(OH)D. Compared with the 1^st quartile (mean 25(OH)D: 29.67±6.18 nmol/L), the VFx risk was significantly lower in the 3^rd (mean 25(OH)D: 60.91±5.12nmol/L) and 4^th quartiles (mean 25(OH)D: 103.3±44.21nmol/L), but not in the 2^nd quartile (mean 25(OH)D: 45.40±3.95 nmol/L). In contrast, the VFx risk was significantly increased in the 1^st quartile (OR=1.87, 95% CI 1.42–2.45) compared with the 2^nd–4^th quartiles.

Conclusions

Vitamin D deficiency/insufficiency was associated with risk of osteoporotic thoracolumbar junction vertebral fractures in elderly patients.