Prediction of damage formation in hip arthroplasties by finite element analysis using computed tomography images

Exploring the displacement characteristics of Garden III femoral neck fractures and the reliability, validity, and value of the anteroposterior Garden Index in assessing displacement severity

BACKGROUND

Femoral neck fractures represent a significant public health concern, particularly in the elderly population. A thorough understanding and assessment of these fractures are deemed essential for optimal treatment and management. Displacement characteristics of Garden III femoral neck fractures were explored in this study, and the reliability, validity, and clinical utility of the anteroposterior Garden Index in evaluating displacement severity were investigated.

METHODS

Patients diagnosed with Garden III femoral neck fractures were included in this study. The anteroposterior Garden Index was computed from X-ray images by three experienced orthopedic doctors. Additionally, the contact area of the fracture endpoint and displacement of the femoral neck were evaluated using 128-slice 3D CT scans. Inter-observer and retest reliability of the Garden Index measurements were assessed, along with its correlation with CT measurements.

RESULTS

In this study, a total of 110 patients with Garden III femoral neck fractures were analyzed, showcasing an almost equal gender distribution and an age range spanning from 20 to 88 years. An average Garden Index of 135° (± 16°) was observed. The intra-observer repeatability of the Garden Index was found to exceed 90%. A significant positive correlation was identified between the Garden Index and the contact surface area of the fracture endpoint (r = 0.82, P < 0.001), while a significant negative correlation was noted with the upward displacement of the femoral neck (r = - 0.79, P < 0.001).

CONCLUSIONS

The anteroposterior Garden Index has been demonstrated to have promising potential as a reliable and valid tool for assessing the displacement severity of Garden III femoral neck fractures. Nonetheless, further research is needed to elucidate its relationship with other fracture characteristics and to enhance its criterion and construct validity.

Changes in hip joint contact stress during a gait cycle based on the individualized modeling method of "gait-musculoskeletal system-finite element"

OBJECTIVE

To construct a comprehensive simulation method of "gait-musculoskeletal system (MS)-finite element (FE)" for analysis of hip joint dynamics characteristics and the changes in the contact stress in the hip throughout a gait cycle.

METHODS

Two healthy volunteers (male and female) were recruited. The 3D gait trajectories during normal walking and the CT images including the hip and femur of the volunteers were obtained. CT imaging data in the DICOM format were extracted for subjected 3D hip joint reconstruction. The reconstructed 3D model files were used to realize the subject-specific registration of the pelvis and thigh segment of general musculoskeletal model. The captured marker trajectory data were used to drive subject-specific musculoskeletal model to complete inverse dynamic analysis. Results of inverse dynamic analysis were exported and applied as boundary and load settings of the hip joint finite element in ABAQUS. Finally, the finite element analysis (FEA) was performed to analyze contact stress of hip joint during a gait cycle of left foot.

RESULTS

In the inverse dynamic analysis, the dynamic changes of the main hip-femoral muscle force with respect to each phase of a single gait cycle were plotted. The hip joint reaction force reached a maximum value of 2.9%BW (body weight) and appeared at the end of the terminal stance phase. Twin peaks appeared at the initial contact phase and the end of the terminal stance phase, respectively. FEA showed the temporal changes in contact stress in the acetabulum. In the visual stress cloud chart, the acetabular contact stress was mainly distributed in the dome of the acetabulum and in the anterolateral area at the top of the femoral head during a single gait cycle. The acetabular contact area was between 293.8 and 998.4 mm², and the maximum contact area appear at the mid-stance phase or the loading response phase of gait. The maximum contact stress of the acetabulum reached 6.91 MPa for the model 1 and 6.92 MPa for the model 2 at the terminal stance phase.

CONCLUSIONS

The "Gait-MS-FE" technology is integrated to construct a comprehensive simulation framework. Based on human gait trajectories and their CT images, individualized simulation modeling can be achieved. Subject-specific gait in combination with an inverse dynamic analysis of the MS provides pre-processing parameters for FE simulation for more accurate biomechanical analysis of hip joint.

Risk assessment of resurfacing implant loosening and femur fracture under low-energy impacts taking into account degenerative changes in bone tissues. Computer simulation

BACKGROUND AND OBJECTIVE

Degenerative diseases of the musculoskeletal system significantly reduce the quality of human life. Hip resurfacing is used to treat degenerative diseases in the later stages. After surgery, there is a risk of endoprosthesis loosening and low-energy fracture during daily physical activity. Computer modeling is a promising way to predict the optimal low-energy loads that do not lead to bone destruction. This paper aims to study numerically the mechanical behavior of the proximal femur, amenable to degenerative changes and subjected to hip resurfacing under low-energy impact equivalent to physiological loads.

METHODS

A numerical model of the mechanical behavior of the femur after hip resurfacing arthroplasty under low-energy impacts equivalent to physiological loads is presented. The model is based on the movable cellular automaton method (discrete elements), where the mechanical behavior of bone tissue is described using the Biot poroelasticity accounting for the presence and transfer of interstitial biological fluid.

RESULTS

For the first time, it is shown that a poroelastic model allows predicting the service life of endoprostheses, taking into account the individual characteristics of the bone tissues amenable to various degenerative diseases. The obtained results indicate that the changes in the bone properties have a significant influence on the critical forces corresponding to the first appearance of microcracks and the fracture formation. At the same time, their effect on the type of fracture is negligible. A much more impact on the type of fracture has the kinematic and dynamic conditions of the exposure.

CONCLUSIONS

The obtained results show the promise of using the proposed model for predicting the operational resource of resurfacing endoprostheses, taking into account the physiological features of the structure of the patient's bone tissues.

Case Report and Literature Review of Periprosthetic Atypical Femoral Fractures After Total Hip Arthroplasty

We describe a case of periprosthetic femoral fracture with 5 major features of an atypical femoral fracture (AFF) and localized cortical thickening at the fracture site, which is characteristic of an AFF. An 81-year-old female patient had undergone cementless total hip arthroplasty for a right femoral neck fracture at the age of 66, and had been taking oral alendronate since then. At the age of 79, she developed spontaneous right thigh pain. Radiographs showed lateral cortical thickening and pedestal formation around the end of the femoral component. She was advised to discontinue oral alendronate and change to eldecalcitol. At the age of 81, she developed sudden severe pain when standing up from a seated position and was not able to walk. Radiographs showed a periprosthetic femoral fracture with 5 major features of AFF at the site of localized cortical thickening. We diagnosed a Vancouver type B1 periprosthetic femoral fracture. She underwent open reduction and internal fixation (ORIF) with an NCB^® Periprosthetic Femur Plate System with cable grips. Daily subcutaneous injection of teriparatide and low intensity pulsed ultrasound therapy were performed to stimulate bone healing. She was able to walk without assistance at 4 months after ORIF. Radiographs showed adequate bridging callus and a disappearing fracture line. This case was diagnosed as a periprosthetic atypical femoral fracture (PAFF), because a periprosthetic fracture is excluded from the definition of AFF. Similar to AFF, PAFF exhibits poor clinical outcomes. The approach to treating PAFF should be decided after considering the pathogenesis.

BUCKLING AND FAILURE ANALYSIS OF BONES IN HIP JOINT

Free body diagram is drawn to compute the various forces and torques acting on hip joint. The FEA models for hip joint and acetabular cup are drawn with the help of CT Scan reports. The stress distribution and deformations are then obtained by using finite element analysis. Contact stresses, contact area radius and maximum pressure are obtained. Modeling of the hip joint and acetabular cup was done and stress distribution was also determined. Since the thigh bone is slender, it was analyzed both manually and through software for buckling. This analysis is performed in order to predict the failure of bones in the hip joint.