Comparison of femoral neck system and three cannulated cancellous screws in the treatment of vertical femoral neck fractures: clinical observation and finite element analysis

Biomechanical characteristic differences of two new types of intramedullary nail devices in the treatment of comminuted intertrochanteric fractures of femur: a comparative study based on finite element analysis

OBJECTIVE

Given the recent application of two new types of intramedullary nail devices in the treatment of comminuted femoral intertrochanteric fractures (CFIFs), there is still a lack of deep understanding and comparative evaluation of their biomechanical properties. Therefore, this study aims to systematically compare the advantages and disadvantages of these two new devices with traditional proximal femoral nail antirotation (PFNA) and InterTan nails in the fixation of CFIFs through finite element analysis.

METHODS

Based on the validated finite element model, this study constructed an accurate CFIFs model. In this model, PFNA, InterTan nails, proximal femoral bionic nails (PFBN), and new intramedullary systems (NIS) were implanted, totaling four groups of finite element models. Each group of models was subjected to simulation tests under a vertical load of 2100 N to evaluate the displacement and Von Mises stress (VMS) distribution of the femur and intramedullary nail devices.

RESULTS

Under a vertical load of 2100 N, a comparative analysis of the four finite element models showed that the NIS device exhibited the most superior performance in terms of peak displacement, while the PFNA device performed relatively poorly. Although the NIS device had the highest peak stress in the femur, it had the smallest peak displacement of both the femur and intramedullary nail devices, and the peak stress was mainly concentrated on the lateral side of the femur, with significantly lower stress in the proximal femur compared to the other three intramedullary nail devices. In contrast, the PFBN device had the lowest peak stress in the femur, and its peak displacement of both the femur and intramedullary nail devices was also less than that of PFNA and InterTan nails.

CONCLUSION

This study demonstrates that in the treatment of CFIFs, PFBN and NIS devices exhibit superior biomechanical performance compared to traditional PFNA and InterTan nail devices. Especially the NIS device, which can achieve good biomechanical results when fixing femoral intertrochanteric fractures with missing medial wall. Therefore, both PFBN and NIS devices can be considered reliable closed reduction and internal fixation techniques for the treatment of CFIFs, with potential clinical application value.

Comparative analysis of the femoral neck system (FNS) vs. cannulated cancellous screws (CCS) in the treatment of Middle-aged and elderly patients with femoral neck fractures: clinical outcomes and biomechanical insights

PURPOSE

This study aimed to compare the clinical outcomes and differences in biomechanical characteristics between the femoral neck system (FNS) and cannulated cancellous screws (CCSs) in the treatment of femoral neck fractures.

METHODS

This study retrospectively analysed a cohort of 38 registered cases of femoral neck fractures treated surgically with either the FNS (n = 17) or CCSs (n = 21) between January 2020 and December 2023. Indicators such as fluoroscopy frequency, length of hospital stay, and fracture healing time were compared between the two groups. Functional status was evaluated via the Harris hip score (HHS) and visual analogue scale (VAS), whereas prognosis was assessed based on changes in the neck shaft angle and femoral neck shortening. Additionally, six sets of femoral neck fracture models were developed based on Pauwels angles of 30°, 40°, 50°, 60°, 70°, and 80°. Two experimental groups, FNS and CCS, were established, and a joint reaction force of 1800 N was applied to the proximal femur. The displacement, stress, and stiffness of the components of interest in the different models were tested and compared.

RESULTS

The distributions of all the baseline characteristics were similar between the two groups (p > 0.05). The FNS group presented significantly shorter fluoroscopy frequency, length of hospital stay, and fracture healing time (p < 0.05). Harris and VAS scores were higher in the FNS group than in the CCS group (p < 0.05). Postoperative changes in the neck shaft angle and femoral neck shortening were significantly lower in the FNS group than in the CCS group (p < 0.05). The results of the finite element analysis indicated that the maximum stress on the femoral head and varus angle were generally lower in the FNS group than in the CCS group and that the maximum displacement of the femoral head and FNS was generally lower in the FNS group than in the CCS group. However, the superiority of FNS over CCS decreased with increasing Pauwels angle. Additionally, the effectiveness of FNS in limiting displacement of the femoral neck upper wall was not as favourable as that of CCS.

CONCLUSIONS

The treatment of femoral neck fractures with FNS is superior and contributes to improved hip joint function. Biomechanical research has confirmed its structural stability and advantages in resisting femoral head varus. However, challenges to its fixation efficacy persist, particularly at higher Pauwels angles.

A finite element analysis of a low-profile femoral neck system of screws in sleeves in a vertical femoral neck fracture model

BACKGROUND

Femoral neck system (FNS) has exhibited some drawbacks, such as non-fit of the plate with the lateral femoral cortex, postoperative pain, and the potential risk of subtrochanteric fractures. We have developed a low-profile FNS system that addresses some compatibility issues in FNS. In this study, we conducted finite element analysis on the 1-hole FNS (1 H-FNS), 2-holes FNS (2 H-FNS), and low-profile FNS (LP-FNS) and compared their biomechanical performance.

METHODS

After the mesh convergence analysis, we established three groups of 1 H-FNS, 2 H-FNS, and LP-FNS. The interfragmentary gap, sliding distance, shear stress, and compressive stress and the bone-implant interface compression stress, stiffness, and displacement were determined under the neutral, flexion, or extension conditions of the hip joint, respectively. The stress and displacement of the femur after the implant removal were also investigated.

RESULTS

(1) There were no obvious differences among the three FNS groups in terms of the IFM distance. However, the LP-FNS group showed less rotational angle compared with conventional FNS (neutral: 1 H-FNS, -61.64%; 2 H-FNS, -45.40%). Also, the maximum bone-implant interface compression stress was obviously decreased under the neutral, flexion, or extension conditions of the hip joint (1 H-FNS: -6.47%, -20.59%, or -4.49%; 2 H-FNS: -3.11%, 16.70%, or -7.03%; respectively). (2) After the implant removal, there was no notable difference in the maximum displacement between the three groups, but the maximum von Mises stress displayed a notable difference between LP-FNS and 1 H-FNS groups (-15.27%) except for the difference between LP-FNS and 2 H-FNS groups (-4.57%).

CONCLUSIONS

The LP-FNS may not only provide the same biomechanical stabilities as the 1 H-FNS and 2 H-FNS, but also have more advantages in rotational resistance especially under the neutral condition of the hip joint, in the bone-implant interface compression stress, and after the implant removal. In addition, the 1 H-FNS and 2 H-FNS have similar biomechanical stabilities except for the maximum von Mises stress after the implant removal. The femur after the LP-FNS removal not only is subjected to relatively little stress but also minimizes stress concentration areas.

Biomechanical changes in the proximal femur before and after removal of femoral neck system

BACKGROUND

As an innovative internal fixation system, FNS (femoral neck system) is increasingly being utilized by surgeons for the treatment of femoral neck fractures. At present, there have been numerous finite element analysis experiments studying the immediate stability of FNS and CSS in treating femoral neck fractures. However, there is scarce mechanical analysis available regarding the effects post internal fixation removal. This study aimed to investigate the alterations in mechanical parameters of the proximal femur before and after the removal of FNS (femoral neck system), and to assess potential distinctions in indicators following the extraction of CSS (Cannulated Screws).

METHODS

A proximal femur model was reconstructed using finite element numerical techniques. The models for CSS and FNS were formulated utilizing characteristics and parametric definitions. The internal fixation was combined with a normal proximal femur model to simulate the healing state after fracture surgery. Within the framework of static analysis, consistent stress burdens were applied across the entirety of the models. The total deformation and equivalent stress of the proximal femur were recorded before and after the removal of internal fixation.

RESULTS

Under the standing condition, the total deformation of the model before and after removing CSS was 0.99 mm and 1.10 mm, respectively, indicating an increase of 12%. The total deformation of the model before and after removing FNS was 0.65 mm and 0.76 mm, respectively, indicating an increase of 17%. The equivalent stress for CSS and FNS were 55.21 MPa and 250.67 MPa, respectively. The average equivalent stress on the cross-section of the femoral neck before and after removal of CSS was 7.76 MPa and 6.11 MPa, respectively. The average equivalent stress on the cross-section of the femoral neck before and after removal of FNS was 9.89 MPa and 8.79 MPa, respectively.

CONCLUSIONS

The retention of internal fixation may contribute to improved stability of the proximal femur. However, there still existed risks of stress concentration in internal fixation and stress shielding in the proximal femur. Compared to CSS, the removal of FNS results in larger bone tunnels and insufficient model stability. Further clinical interventions are recommended to address this issue.

Femoral Neck Fractures Treated by Closed Reduction and Internal Fixation with the Double Fluoroscope Technique: A Preliminary Study

Background: Fractures of the femur require significant radiation exposure during operations using fluoroscopy (C-arm), posing a high risk of radiation exposure to the medical staff and patients. To address this concern, in this study, we investigated the efficacy of using two fluoroscopy machines simultaneously. Methods: We categorized 30 patients with femoral neck fracture (FNF) into single and double C-arm groups. The operation and radiation exposure times during a closed reduction and internal fixation operation were investigated to evaluate whether the operation and radiation exposure times were effectively audited when the operation was performed using a double C-arm. Results: The total operation times were 93.21 ± 20.70 min and 66.69 ± 13.97 min for the single and double C-arm groups, respectively. Additionally, the total radiation times were 100.43 ± 24.59 s and 83.06 ± 19.53 s for the single and double C-arm groups, respectively. Operation and radiation exposure times in the two groups showed statistically significant differences (p < 0.05). Conclusion: The use of double C-arm in FNF can reduce operation and radiation exposure times. Hence, using the double C-arm in surgical treatment could reduce the risk of radiation exposure to medical staff and patients.

Femoral neck system versus multiple cannulated screws for the fixation of Pauwels classification type II femoral neck fractures in older female patients with low bone mass

BACKGROUND

Femoral neck fractures in older adult patients are a major concern and often necessitate surgical intervention. This study compared the clinical outcomes of 2 surgical techniques: the femoral neck system (FNS) and cannulated compression screws (CCSs).

METHODS

A total of 40 female patients (mean age 73.50 ± 11.55 years) with femoral neck fractures of Pauwels classification type II and receiving surgical fixation between 2020 and 2022 were enrolled. The patients were categorized into an FNS group (n = 12) or a CCS group (n = 28), and surgical duration, intraoperative blood loss, length of hospital stay, and incidence of postoperative adverse events were analyzed.

RESULTS

No significant intergroup differences in demographic characteristics were discovered. The mean surgical duration for all patients was 52.88 ± 22.19 min, with no significant difference between the groups. However, the FNS group experienced significantly higher intraoperative blood loss (P = 0.002) and longer hospital stay (P = 0.023) than did the CCS group. The incidence of osteonecrosis was higher in the CCS group, whereas the incidence of nonunion or malunion was higher in the FNS group. The surgical method did not appear to be a significant risk factor. The main risk factor for revision surgery was longer duration until the first adverse event (P = 0.015).

CONCLUSION

The FNS does not appear to provide superior surgical outcomes compared with CCSs in older adult women with Pauwels classification type II femoral neck fractures. A longer duration between surgical fixation and the first adverse event before stabilization of the fracture site may be a risk factor for revision surgery.