Age-related dynamic deformation of the femoral shaft and associated osteoporotic factors: a retrospective study in Chinese adults

Associations between femoral 3D curvature and sagittal imbalance of spine

Background

The sagittal imbalance (SI) of spine triggers compensatory mechanisms (CMs) of lower extremity (LE) to restore trunk balance. These CMs can cause long-period stress on the femur and may possibly alter the femoral morphology. This cross-sectional observational study aimed to answer the following questions: (a) Do SI subjects exhibit greater femoral bowing compared to subjects with sagittal balance? (b) Are there associations between femoral bowing and CMs of LE in SI subjects?

Methods

Subjects who underwent biplanar full body radiographs with the EOS imaging system between January 2016 and September 2021 were recruited. Sagittal parameters included T1-pelvic angle (TPA), pelvic incidence (PI), pelvic tilt (PT), sacral slope, lumbar lordosis (LL), PI-LL, and PT/PI ratio. LE parameters were femoral obliquity angle (FOA), knee flexion angle (KA), and ankle dorsiflexion angle. Femoral bowing was quantified as 3D radius of femoral curvature (RFC). Associations between 3D RFC and the radiographic parameters were analyzed.

Results

A total of 105 subjects were included, classified into balance group (TPA < 14°, n = 40), SI group (TPA ≥ 14° and KA <5°, n = 30), and SI with knee flexion group (TPA ≥ 14° and KA ≥ 5°, n = 35). 3D RFC was significantly lower in SI with knee flexion group compared to the other two groups (both p < 0.001). Stepwise linear regression showed that age, SI and knee flexion, femoral length (FL), FOA, and KA were independent predictors for 3D RFC.

Conclusion

Greater femoral bowing is observed in subjects with SI and knee flexion compared to the balanced population. CM parameters, including KA and FOA, are associated with 3D RFC. Further longitudinal study is needed to investigate the cause-and-effect relationship between SI, CMs of LE, and femoral bowing.

Chronological Changes in Sagittal Femoral Bowing after Primary Cementless Total Hip Arthroplasty: A Comparative 3D CT Study

Little is known about dynamic changes of femoral anatomy after total hip arthroplasty (THA), in particular about sagittal femoral bowing (SFB). A 3D CT study was designed to evaluate the chronological changes of SFB after cementless femoral stem implantation for primary THA. Ten patients who underwent unilateral primary THA with a cementless femoral stem, with 2 consecutive CT scans (extending from the fourth lumbar vertebra to the tibial plateaus), performed before THA and at least 3 years after THA, were enrolled. The 3D models of femurs were created using image segmentation software. Using the two CT scans, SFB values of the proximal and middle thirds were calculated on the replaced and untreated sides by two different observers. Eight anatomical stems and two conical stems were involved. The post-operative CT was performed at an average follow-up of 6.5 years after THA (range: 3-12.5). The measurements performed by the two observers did not differ in the proximal and middle regions. A significant difference between the pre-operative and post-operative SFB compared to the untreated side was found in the proximal femur segment (p = 0.004). Use of a cementless stem in THA induced chronological changes in SFB of the proximal femur, after a minimum timespan of 3 years.

The effect of patient positioning on measurements of bone mineral density of the proximal femur: a simulation study using computed tomographic images

The patient's position may affect the bone mineral density (BMD) measurements; however, the extent of this effect is undefined. This CT image-based simulation study quantified changes in BMD induced by hip flexion, adduction, and rotations to recommend appropriate patient positioning when acquiring dual-energy x-ray absorptiometry images.

PURPOSE

Several studies have analyzed the effect of hip rotation on the measurement of bone mineral density (BMD) of the proximal femur by dual-energy x-ray absorptiometry (DXA). However, as the effects of hip flexion and abduction on BMD measurements remain uncertain, a computational simulation study using CT images was performed in this study.

METHODS

Hip CT images of 120 patients (33 men and 87 women; mean age, 82.1 ± 9.4 years) were used for analysis. Digitally reconstructed radiographs of the proximal femur region were generated from CT images to calculate the BMD of the proximal femur region. BMD at the neutral position was quantified, and the percent changes in BMD when hip internal rotation was altered from -30° to 15°, when hip flexion was altered from 0° to 30°, and when hip abduction was altered from -15° to 30° were quantified. Analyses were automatically performed with a 1° increment in each direction using computer programming.

RESULTS

The alteration of hip angles in each direction affected BMD measurements, with the largest changes found for hip flexion (maximum change of 17.7% at 30° flexion) and the smallest changes found for hip rotation (maximum change of 2.2% at 15° internal rotation). The BMD measurements increased by 0.34% for each 1° of hip abduction, and the maximum change was 12.3% at 30° abduction.

CONCLUSION

This simulation study quantified the amount of BMD change induced by altering the hip position. Based on these results, we recommend that patients be positioned carefully when acquiring DXA images.

Study on geometry and morphology of proximal humerus in Northern Chinese population based on 3-D CT

BACKGROUND

This study investigated the characteristics of humeral geometric and morphological parameters in northern Chinese population by three-dimensional measurements, and compared whether there were differences in humeral morphology among populations from different geographical regions.

METHODS

Computed tomography scans of 80 humerus were obtained, reconstructed and measured. Differences in humeral morphological parameters between genders and sides were compared. Correlation analysis was used to explore possible correlations among the parameters. The differences in humeral geometric morphometric parameters between Western and East Asian populations were compared according to pool results of present and previous studies.

RESULTS

The average (and standard deviation) of humeral head radius curvature, arc angle, diameter, and thickness was 151.79 ± 6.69°, 23.36 ± 2.08 mm, 44.83 ± 3.92 mm and 17.55 ± 1.84 mm in coronal humeral head plane, and 152.05 ± 8.82°, 21.81 ± 1.88 mm, 41.77 ± 3.44 mm and 16.52 ± 1.92 mm in transversal humeral head plane. The average of the humeral head medial offset and posterior offset was 7.34 ± 2.47 mm and 0.08 ± 1.72 mm. Humeral head inclination angle, arc angle and radius curvature of humeral neck-shaft averaged 137.69 ± 4.92°, 34.7 ± 5.29° and 55.76 ± 13.43 mm. Superior, inferior, anterior, posterior concave angle of humeral anatomical neck averaged 150.41 ± 10.91°, 146.55 ± 10.12°, 146.43 ± 13.53° and 149.33 ± 14.07°. The average of height of the greater tuberosity, height of the lesser tuberosity, depth, concave angle and volume of the intertubercular groove was 14.19 ± 1.7 mm, 8.9 ± 1.54 mm, 0.92 ± 0.31 mm3, 31.28 ± 9.61 mm, 4.98 ± 1.19 mm and 89.35 ± 17.62°. The upper angle of the greater tuberosity averaged 161.04 ± 7.84°, the upper angle of the greater tuberosity was 165.94 ± 3.6°. Differences in parameters of proximal humerus between genders and sides were found. There was no correlation between parameters of proximal humerus and age. Correlations were found among humeral morphological parameters. East Asian populations differed in proximal humeral morphology from Western populations.

CONCLUSIONS

This study will provide references for diagnosing and classifying shoulder disease, designing prosthesis and instrument, enhancing surgical precision and guiding patient recovery.

The characteristics and influence of iatrogenic fracture comminution following antegrade interlocking nailing for simple femoral shaft fractures, a retrospective cohort study

AIM

The incidence and characteristics of iatrogenic comminution (IC) are unknown, and the influence of IC on fracture union is unclear. This study was aimed to investigate the (1) incidence and characteristics of IC and (2) the outcomes of IC following antegrade interlocking nailing of simple femoral shaft fractures.

METHODS

We retrospectively collected data on patients who experienced simple femoral shaft fractures and underwent antegrade interlocking nailing between February 2009 and December 2016. The incidence and characteristics of IC were examined. According to the presence of IC, patients were divided into two groups: an IC group and a non-IC (NIC) group. Demographic information and nonunion rates were compared between the two groups. Potential risk factors for IC (age, gender, body mass index (BMI), nail fit ratio, reduction technique, and greater trochanter nail entry) were analyzed using univariate and multivariate logistic regression. The aforementioned variables, along with IC occurrence, were also assessed as potential risk factors for nonunion at 12 and 24 months after operation using multivariate logistic regression.

RESULTS

Of the 211 total patients, IC occurred in 20.9% (n = 44) of patients. Most ICs were found at the level of the isthmus, and involved the medial cortex. Compared with the NIC group, higher nonunion rates were observed in the IC group at 12 months (31.8% vs. 12.5%, p = 0.002) and 24 months (18% vs. 6.5%, p = 0.017) after surgery. Age older than 35 years old was related with the occurrence of IC in univariate analysis. Multivariate analysis found no risk factor associated with IC. Open reduction technique, IC occurrence and higher BMI were identified as the risk factors of nonunion at 12 months and 24 months after surgery in multivariate analysis.

CONCLUSION

IC is a non-rare complication in antegrade interlocking nailing of simple femoral shaft fractures and was associated with higher nonunion rate. Age older than 35 years old showed a trend toward increasing risk of iatrogenic fracture comminution. In multivariate analysis, open reduction technique, IC occurrence and higher BMI significantly correlated with fracture nonunion.

LEVEL OF EVIDENCE

Level IV.

Lateral Bowing of Femur Associated With Older Age, Shorter Stature, and Lower Bone Mineral Density

We often encounter elderly patients with femur bowing. According to literature, femoral bowing is correlated with patient characteristics such as aging, race, atypical femoral fracture (AFF), and osteoporosis. However, the clear relationships between these factors and femoral bowing are still unknown. In addition, most previous reports have been based only on X-rays and may not provide accurate information due to femur rotation and inter-operator reliability when compared to the information obtained using computed tomography (CT) scans. The purpose of this study was to examine the factors associated with anterior and lateral bowing in detail, by using three-dimensional preoperative measurement software Zed Hip®︎ (LEXI Co. Ltd., Tokyo, Japan). A total of 364 patients with trochanteric hip or femoral neck fractures, or osteoarthritis, treated in our hospital were included in this study. Of these, 61 patients older than 50 years, who had complete CT volume data for the entire length of the femur on the healthy side and bone mineral density (BMD) measured by trunk dual-energy X-ray absorptiometry (DXA), were investigated. There were 13 males and 48 females, aged 53-97 years (mean 78.7±10.8 years). We defined the starting and ending points of the femoral diaphysis to measure anterior bowing (AB) and lateral bowing (LB) of the femoral diaphysis. The correlation between AB or LB with each patient's characteristics (age, height, weight, lumbar BMD, and femoral BMD) was examined retrospectively. AB did not correlate with any of the patient parameters. LB weakly positively correlated with age and was negatively correlated with height and femoral (greater trochanter) bone density. Weight was in no correlation with either AB or LB. A novel three-dimensional approach was used for measurements that may be more accurate than plain two-dimensional radiographs.