Comparing Two Different Automatic Methods to Measure Femoral Neck-Shaft Angle Based on PointNet++ Network

Bacnground: Accurate measurement of the femoral neck-shaft angle (NSA) is of great significance for diagnosing hip joint diseases and preoperative planning of total hip arthroplasty. However, the fitting lines of the femoral neck and femoral shaft did not always intersect in 3D space. Thus, it is unclear whether there is a difference between 2D and 3D methods for measuring NSA. Methods: The femoral point cloud datasets from 310 subjects were segmented into three regions, including the femoral head, femoral neck, and femoral shaft using PointNet++. We created a projection plane to simulate the hip anteroposterior radiograph and fitted the femoral neck axis and femoral shaft axis to complete the 2D measurement, while we directly fitted the two axes in space to complete the 3D measurement. Also, we conducted the manual measurement of the NSA. We verified the accuracy of the segmentation and compared the results of the two automatic and manual methods. Results: The Dice coefficient of femoral segmentation reached 0.9746, and MIoU of that was 0.9165. No significant difference was found between any two of the three methods. While comparing the 2D and 3D methods, the average accuracy was 98.00%, and the average error was 2.58°. Conclusion: This paper proposed two accurate and automatic methods to measure the NSA based on a 2D plane and a 3D model respectively. Although the femoral neck and femoral shaft axes did not intersect in 3D space, the NSAs obtained by 2D and 3D methods were basically consistent.

Restoration of Some Anatomical Dimensions By Spiron Short Stem Hip Replacement Applied To Vietnamese People

Background: The process of using proximal bone in hip arthroplasty will allow the remaining bone to be preserved in future surgeries. To take advantage of these advantages, many types of short stem prosthetics have been developed in recent years. The obtained survey parameters combined with the obtained anatomical parameters shown that the Spiron joint is suitable when applied to adult Vietnamese.Research subjects and methods: The anatomical dimensions of the hip joint related to Spiron joint replacement were analyzed by the authors.Results: The anatomical results with Spiron showed that the acetabular average diameter and tilt angle were 49.77 mm and 41.55°. The femoral neck-to-body angle, the femoral upper-neck diameter, the distance from the crest to the hard shell along the femoral neck axis was on average 131.52°, 34, 32mm, and 51.39mm, respectively. The offset distance from the center of the crest to the axis of the femur is 38.33mm. These parameters show the working ability as well as stability when replaced by the Spiron joint.Conclusion: When applied to adult Vietnamese, the femoral neck diameter is consistent with the Spiron diameter. Preoperative planning is needed to check the femoral neck angle and femoral neck length prior to surgery to see if the Spiron joint replacement is eligible. The findings of this study support the assumption that it is feasible to use Spiron prostheses in joint replacement in Vietnamese adults.

Radiographic Assessment of the Proximal Femoral Anatomy in An Indigenous African Adult Population

Background: Hip surgeries such as fracture fixation, corrective osteotomy, hemiarthroplasty, or total hip arthroplasty require accurate preoperative templating for a successful outcome. Such templating is done using the proximal femur and the acetabulum radiographs, depending on the planned surgery. Understanding the normal radiographic anatomy of the proximal femur is crucial to differentiate a normal from pathological anatomy. Proximal femoral anatomic indices include the femoral head diameter, femoral neck diameter, femoral neck length, femoral offset, femoral neck axis length and the femoral neck-shaft angle. Aim: This study assesses and establishes the average values of the proximal femoral anatomy in an indigenous African adult population. Method: This cross-sectional study examined 190 normal anteroposterior (AP) radiographs of the pelvis. The mean age, weight and height of the subjects were obtained. The following proximal femoral anatomic parameters were measured: femoral neck length (FNL), femoral neck diameter (FND), femoral head diameter (FHD), femoral neck-shaft angle (FNSA), femoral offset (FO) and femoral neck axis length (FNAL). The authors compared the mean difference of the parameters between the genders and the age categories and assessed the parameter correlations with the patients’ weight and height. Results: Males constituted 63 (33.2%) of the study population. The mean age of the subjects was 51.46 years (SD = 16.37). The mean weight was 76.13 kg, while the mean height was 1.62 m. The mean values of the proximal femoral parameters were as follows: FNL 4.52cm, FND 3.42cm, FHD 4.76cm, FNSA 132.960, FO 4.09cm, and FNAL 10.34cm. Males have a significantly higher mean value in all the parameters except the FO. None of the parameters showed any significant difference among the age categories except the FNL. A post-hoc analysis showed that the difference in the FNL lies between the young and the elderly age groups. The subjects’ height correlated with all the parameters except FNSA, while the weight correlated with the FND, FNSA and FNAL. Conclusion: The proximal femoral anatomy in Africans differed from those published in foreign literature. This knowledge is crucial for implant manufacturing companies and preoperative templating for hip surgeries. KEY WORDS: Proximal femur, Anatomy, Black population.

Atraumatic femoral head necrosis: a biomechanical, histological and radiological examination compared to primary hip osteoarthritis

Introduction Atraumatic necrosis of the femoral head (AFHN) is a common disease with an incidence of 5000–7000 middle-aged adults in Germany. There is no uniform consensus in the literature regarding the configuration of the bone in AFHN. The clinical picture of our patients varies from very hard bone, especially in idiopathic findings, and rather soft bone in cortisone-induced necrosis. A better understanding of the underlying process could be decisive for establishing a morphology-dependent approach. The aim of this study is the closer examination of the condition of the bone in the AFHN compared to the primary hip osteo arthritis (PHOA). Materials and methods The preparations were obtained as part of elective endoprosthetic treatment of the hip joint. Immediately after sample collection, thin-slice CT of the preserved femoral heads was performed to determine the exact density of the bone in the necrosis zone. Reconstruction was done in 0.8–1 mm layers in two directions, coronary and axial, starting from the femoral neck axis. Density of the femoral heads was determined by grey value analysis. The value in Hounsfield units per sample head was averaged from three individual measurements to minimize fluctuations. For biomechanical and histomorphological evaluation, the samples were extracted in the load bearing zone perpendicular to the surface of the femoral head. Group-dependent statistical evaluation was performed using single factor variance analysis (ANOVA). Results A total of 41 patients with a mean age of 64.44 years were included. The mean bone density of the AFHN samples, at 1.432 g/cm3, was about 7% higher than in the PHOA group with a mean value of 1.350 g/cm3 (p = 0.040). The biomechanical testing in the AFHN group showed a 22% higher—but not significant—mean compressive strength (20.397 MPa) than in the PHOA group (16.733 MPa). On the basis of histological analysis, no differentiation between AFHN and PHOA samples was possible. Conclusions The present study (NCT, evidence level II) shows that AFHN has a very well detectable higher bone density compared to PHOA. However, neither biomechanical stress tests nor histomorphological evaluation did show any significant difference between the groups. The results allow the conclusion that there is no “soft” necrosis at all in the AFHN group.

The hip asphericity angle: a novel angle for measurement of Cam-FAI correction

The alpha angle is routinely used for the diagnosis and quantitative description of the Cam deformity of the hip. However, a reliable identification of the femoral neck axis as its reference line can be difficult. Moreover, most cam resections include a reduction of the femoral neck diameter with an automatic posteromedial angulation of the femoral neck axis. In consequence, the reference axes for the pre- and postoperative alpha angles are different, and a comparison of both angles underlies a systematic error to relatively higher postoperative alpha angles. In order to avoid this systemic error, we propose the hip asphericity (HA) angle with a reference axis independent of the amount of bony resection. Two retrospective groups were formed, a ‘femoroacetabular impingement (FAI) group’ that had hip arthroscopy for cam resection and a ‘Control group’ without cam deformity. The alpha and HA angles were measured by three examiners. The measurements were repeated 1 month later. In the FAI group, offset correction was calculated using both angles. Statistically significant differences for both the alpha and the HA angles were found between the control and the preoperative FAI group as well as between the preoperative and postoperative FAI groups. The HA angle-correction by a mean of 27.5° was significantly higher in comparison to the alpha angle correction by a mean of 25.4°. The intertester and intratester reliability of both angles were not significantly different. The HA angle is a new and reliable radiographic parameter for measuring cam deformity and proves superior in measuring cam correction.

Anatomic evaluation of the insertional footprints of the iliofemoral and ischiofemoral ligaments: a cadaveric study

Background An understanding of the insertional footprints of the capsular ligaments of the hip is important for preserving hip function and stability given the increasing number of minimally invasive hip surgeries being performed under a limited surgical view. However, it is difficult to detect these ligaments intraoperatively and many surgeons may not fully appreciate their complex anatomy. The aims of this study were to quantify the proximal and distal footprints of the iliofemoral ligament (ILFL) and ischiofemoral ligament (ISFL) and to estimate the location of the corresponding osseous landmarks on the proximal femur, which can be detected easily during surgery. Methods Twelve hip joints from Japanese fresh frozen cadavers were used. All muscle, fascia, nerve tissue, and vessels were removed to expose the intact capsular ligaments of the hip. The length and width of the proximal and distal footprints of the ILFL and ISFL were measured and their relationship to osseous structures was evaluated, including the intertrochanteric line, femoral neck, and lesser trochanter. Results The mean length of the distal medial arm of the ILFL footprint was 17.9 mm and the mean width was 9.0 mm. The mean length of the distal lateral arm of the ILFL footprint was 23.0 mm and the mean width was 9.7 mm. For the footprint of the medial arm, the insertion was in the distal third of the intertrochanteric line and that of the lateral arm was in the proximal 42% of this line. The mean distance from the lesser trochanter to the footprint of the medial arm was 24.6 mm. The mean length of the distal ISFL footprint was 11.3 mm and the mean width was 6.9 mm. The footprint of the distal ISFL was located forward of the femoral neck axis in all specimens. Conclusions Understanding the size and location of each capsular ligament footprint in relation to an osseous landmark may help surgeons to manage the hip capsule intraoperatively even under a narrow surgical view. The findings of this study underscore the importance of recognizing that the distal ISFL footprint is located relatively forward and very close to the distal lateral arm footprint.

Effect of Loading Direction and Bone Density Distribution in Assessing Hip Fracture via Finite Element Analysis

An accurate assessment of hip fracture risk requires a proper consideration of parameters affecting the fracture. In general, hip fracture is affected by bone morphology, bone mineral Density (BMD), and load amount. Hip fracture is an outcome of the interaction of all those parameters including loading directions. Assessing the effect of the parameters individually may not correctly reflect the root cause of the hip fracture. Hence, this research aims at analyzing the significance of parameters and their interaction. A multivariate regression model was used considering bone density (ρash), different loading directions during sideways fall, represented by load angle (α) on the coronal plane and angle (β) on the transverse plane as independent parameters and Fracture Risk Index (FRI) as a dependent parameter. The statistical results showing the significant value of 0.7321 for α, and 0.0001 for β and ρash indicates that the effect of loading direction about femoral shaft on the coronal plane (α) does not have impact on fracture risk while loading direction about femoral neck axis on the transverse plane (β) and ρash have the significant impact. Furthermore, the analysis of the interaction of parameters shows that the impact of β on fracture risk may depends more on bone density as the significance of interaction of β and ρash is 0.0001.

Discrimination of Low-Energy Acetabular Fractures from Controls Using Computed Tomography-Based Bone Characteristics

The incidence of low-energy acetabular fractures has increased. However, the structural factors for these fractures remain unclear. The objective of this study was to extract trabecular bone architecture and proximal femur geometry (PFG) measures from clinical computed tomography (CT) images to (1) identify possible structural risk factors of acetabular fractures, and (2) to discriminate fracture cases from controls using machine learning methods. CT images of 107 acetabular fracture subjects (25 females, 82 males) and 107 age-gender matched controls were examined. Three volumes of interest, one at the acetabulum and two at the femoral head, were extracted to calculate bone volume fraction (BV/TV), gray-level co-occurrence matrix and histogram of the gray values (GV). The PFG was defined by neck shaft angle and femoral neck axis length. Relationships between the variables were assessed by statistical mean comparisons and correlation analyses. Bayesian logistic regression and Elastic net machine learning models were implemented for classification. We found lower BV/TV at the femoral head (0.51 vs. 0.55, p = 0.012) and lower mean GV at both the acetabulum (98.81 vs. 115.33, p < 0.001) and femoral head (150.63 vs. 163.47, p = 0.005) of fracture subjects when compared to their matched controls. The trabeculae within the femoral heads of the acetabular fracture sides differed in structure, density and texture from the corresponding control sides of the fracture subjects. Moreover, the PFG and trabecular architectural variables, alone and in combination, were able to discriminate fracture cases from controls (area under the receiver operating characteristics curve 0.70 to 0.79). In conclusion, lower density in the acetabulum and femoral head with abnormal trabecular structure and texture at the femoral head, appear to be risk factors for low-energy acetabular fractures.

Three-Dimensional Morphological Analysis of the Femoral Neck Torsion Angle - An Anatomical Study

Background: The femoral neck torsion angle (FNTA) is an important but often neglected parameter in assessments of the anatomical morphology of the femoral neck, which is often confused with the femoral neck anteversion angle (FNAA) in the current literature. Currently, the measurement methods reported in the literature all adopt the naked eye or two-dimensional (2D) visualization method, and the measurement parameters and details are not clearly defined. The objection of this research was to provide a reliable 3D method for determining the femoral neck axis, to improve the measurement method of the FNTA, and to analyze the anatomical and clinical significance of the results.Methods: Computed tomography (CT) data of 200 patients who received a lower extremity CT angiography examination were selected, and the bilateral femurs were reconstructed with three dimensional CT (3D CT). First, the 3D axis of the femoral neck was built. Second, the long axis of the cross section the femoral neck isthmus (FNI) and femoral neck basilar part (FNB) were confirmed by the “inertia axes” method, and the plane consisting of the long axis of the cross-section and the center of the femoral head was defined as the long axial plane. Third, the coronal plane of the proximal femur was determined through the long axis of the proximal femur and the femoral coronal. Finally, the FNTAs (the angles between the long axial planes and the coronal plane of the proximal femur) of FNI and FNB were measured. The size of FNTA was compared between the sexes and sides and different locations, the correlation between the parameters and age, height and weight were evaluated.Results: The difference in FNTA was statistically significant between the isthmus and the basilar part (isthmus 30.58 ± 8.90° vs. basilar part 23.79 ± 3.98°; p < 0.01). Significant difference in the FNTA was observed between the sexes (males 31.99 ± 9.25° vs. females 27.49 ± 7.19°; p < 0.01). The increase in FNTA from the basilar part to the isthmus was 6.79 ± 8.06°, and the male (7.87 ± 8.57°) was greater than the female (4.44 ± 6.23°, p < 0.01). However, no significant difference in the values was observed between sides. Height exerted the greatest effect on the FNTA according to the correlation analysis (r = 0.255, p＜0.001). Conclusions: This study found a reliable 3D method for the determination of the femoral neck axis improved the measurement method of the FNTA and made it more accurate and repeatable. The results provided a methodological basis and theoretical support for the research and development of internal fixation device for femoral neck fracture and the spatial configuration of implants in treatment. And, the optimal opening point of the femoral medullary cavity was recommended to locate at the posterior position of the top of the femoral neck cross-section during hip replacement.