A prediction model for osteonecrosis of femoral head after internal fixation with multiple cannulated compression screws for adult femoral neck fractures

A Criterion of Reduction Quality of Femoral Neck Fractures Based on Spatial Residual Displacements of Femoral Head

OBJECTIVE

Currently, quality criteria for reduction after femoral neck fractures such as the Garden index are mainly based on two-dimensional x-rays. Research shows that current reduction quality criteria are no longer sufficient to meet the needs to reduce the incidence of osteonecrosis of the femoral head (ONFH). The purpose of this study is to construct a reduction quality criterion based on spatial residual displacements of 3D reconstruction and to predict the occurrence of ONFH.

METHODS

The subjects were from the Tianjin Hospital Hip Fracture cohort, all of whom experienced femoral neck fractures and underwent reduction and internal fixation at Tianjin Hospital and received 12 months of follow-up minimally postoperatively. CT scans were used for 3D reconstruction, and six spatial displacement indicators were measured. Risk factors of ONFH were identified using logistic regression, and a reduction quality criterion based on spatial residual displacements was constructed. Multivariate logistic regression models were performed to estimate the effect of reduction quality by the new criterion on ONFH.

RESULTS

Data from 391 patients were included in the final analysis. Preoperative displacement of the center of the femoral head (CFH), postoperative residual displacement of the CFH, and residual rotational displacement were proved to be independent risk factors for ONFH, with OR values of 3.83 (95% CI: 1.98, 7.48), 2.62 (95% CI: 1.05, 6.49), and 5.36 (95% CI: 2.46, 11.64), respectively. The new criterion was composed of two indicators and had three grades: when residual displacement of CFH is ≤ 4.075 mm, and residual rotational displacement of femoral head is ≤ 18.595°, the quality is excellent; when residual displacement of CFH is ≤ 4.075 mm and residual rotational displacement of femoral head is > 18.595° or when residual displacement of CFH is > 4.075 mm and residual rotational displacement of femoral head is ≤ 18.595°, the quality is moderate; when residual displacement of CFH is > 4.075 mm and residual rotational displacement is > 18.595°, the quality is poor. The risk of ONFH would increase 3.99 times (95% CI: 2.35, 6.78) for each lower grade in reduction quality. The logistic regression model was well discriminated with an AUC area of 0.802 and had good calibration with a p-value of > 0.05 by the Hosmer-Lemeshow test.

CONCLUSION

A new reduction quality criterion for femoral neck fracture based on CT was constructed, and reduction quality before fixation by the new criterion was proved to be an independent predictive factor for ONFH. The logistic regression model had quite good discrimination and calibration for postoperative ONFH.

The effects of systemic ozone application and hyperbaric oxygen therapy on avascular necrosis of the femoral head: An experimental study in the vascular deprivation of the rat femoral head model

OBJECTIVES

This study aims to assess the effects of systemic medical ozone (O3) application and to compare its effects with hyperbaric oxygen (HBO) therapy for preventing avascular necrosis of the femoral head in a rat model.

MATERIALS AND METHODS

A total of 50 male Wistar albino rats were divided into six groups including five rats in each control and sham-operated control group and 10 rats in the remaining four groups: (i) control group, (ii) sham-operated control group, (iii) avascular necrosis group, (iv) intraperitoneal ozone given avascular necrosis group, (v) HBO therapy given avascular necrosis group, and (vi) intraperitoneal ozone and HBO given avascular necrosis group. We surgically induced osteonecrosis by cutting the ligamentum teres and placing a tight ligature around the femoral neck. At Week 11, we harvested femoral heads bilaterally from each animal and performed a macroscopic, histological evaluation and histomorphometric, immunohistochemical analysis.

RESULTS

The intertrabecular mesenchymal cell ratio was substantially higher in the O3 group than that of all other groups in the histological evaluation (p<0.05). Group O3 had also significantly more CD31-positive stained new vasculature than other groups, with the exception of the HBO therapy group, according to the immunohistochemical analysis (p<0.05).

CONCLUSION

The results of this experimental study suggest that the application of medical ozone alone may have a positive effect on new vessel formation and the repair process and may be more beneficial than HBO therapy and HBO+O3 therapy in the vascular deprivation of the rat femoral head model.

Treatment of Femoral Neck Fractures in Adults With Improved Biplane Double-Supported Screw Fixation and Femoral Neck System: Complications and Surgical Techniques

OBJECTIVES

Treating femoral neck fractures remains a significant challenge for orthopedic surgeons and imposes a substantial economic burden on developing regions. Current novel internal fixation methods demonstrate excellent biomechanical performance. However, these new internal fixation methods are still associated with various complications. This study aimed to report the clinical complications of femoral neck system (FNS) and biplane double-supported screw fixation (BDSF) treatments for femoral neck fractures at our institution and provide directions for selecting cost-effective internal fixation methods.

METHODS

A retrospective case-control study of adult patients with femoral neck fractures treated with BDSF or FNS was conducted at Nanfang Hospital from April 2019 to April 2022. General medical records were collected both preoperatively and intraoperatively. Primary complication measures included osteonecrosis of the femoral head, nonunion, screw-out, and subtrochanteric fractures, along with femoral neck shortening. The primary functional measure evaluated was the Harris hip score. This study employed t-test, Wilcoxon rank-sum test, and chi-square test to statistically analyze the data.

RESULTS

Statistically significant differences were observed between the BDSF and FNS groups in terms of surgery duration (60.8 ± 12.6 min vs. 71.0 ± 12.0 min), incision length (5.5 ± 1.2 cm vs. 9.1 ± 1.6 cm) and hospitalization costs (39563.8 ± 9086.4 RMB vs. 24960.4 ± 10154.4 RMB). No statistically significant differences between the BDSF and FNS groups were found in the baseline data, blood loss or hospital stay. Moderate femoral neck shortening was significantly less common in the BDSF group than in the FNS group (27.1% vs. 61.5%, p = 0.016). Postoperatively, no statistically significant differences in complication rates, such as femoral head necrosis, nonunion, subtrochanteric fractures or screw-out, were observed between the BDSF and FNS groups.

CONCLUSIONS

This study revealed no significant difference in the incidence of postoperative complications such as femoral head necrosis, nonunion or screw cut-out between BDSF and FNS. Although BDSF has drawbacks, such as a long learning curve and the potential to cause subtrochanteric fractures, it is cost-effective and better maintains the length of the femoral neck. The modified BDSF technique may be more suitable for developing regions with limited health care budgets.

Effectiveness of the Dorr index in predicting implant failure before proximal femoral nail application

OBJECTIVES

This study aimed to investigate the importance of the Dorr index in the preoperative evaluation of implant failure in patients who underwent proximal femoral nail (PFN).

PATIENTS AND METHODS

This retrospective study examined 312 patients who underwent PFN for intertrochanteric fractures between January 2016 and January 2020. Patients with unstable fractures according to the AO/OTA (AO Foundation/Orthopaedic Trauma Association) classification, those over 65 years of age, with at least one year of regular follow-up, a tip-apex distance <25 mm, and a caput-collum-diaphyseal angle between 125° and 135°, were included. Seventy patients (19 males, 51 females; mean age: 72±3.8 years; range, 65 to 88 years) who met the inclusion criteria were included in the study. According to the Dorr index, patients were type A if the ratio was <0.5, type B if the ratio was between 0.50 and 0.75, and type C if the ratio was >0.75.

RESULTS

The mean follow-up period was 46.2±4.4 months. As indicated by the Dorr index, the failure rates were 0%, 17%, and 63% for Dorr types A, B, and C, respectively. The comparison of failure rates between Dorr types A and B (p=0.02), B and C (p=0.016), and A and C (p=0.001) yielded statistically significant results. Patients with Dorr types B and C exhibited significantly inferior outcomes compared to those with type A. The mean time to failure was 27±3 days after surgery.

CONCLUSION

Dorr index is an important parameter that can be easily checked and used on preoperative radiographs to predict implant failure. The high probability of failure in the early period should be taken into account, particularly if PFN is planned in Dorr type C.

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.

The small screw-apex distance is potentially associated with femoral head osteonecrosis in adults with femoral neck fractures treated by closed reduction and percutaneous 3 parallel cannulated screws

OBJECTIVE

Femoral neck fractures (FNFs) are among the most common fractures in elderly individuals. Surgery is the main treatment for FNFs, and osteonecrosis of the femoral head (ONFH) is one of the unacceptable complications. This study aimed to assess both the clinical and radiological outcomes in patients with FNFs treated with three parallel cannulated screws and to identify relationship between screws position and ONFH.

PATIENTS AND METHODS

A total of 100 patients who were treated with closed reduction and fixed with 3 parallel cannulated screws met the inclusion criteria between January 2014 and December 2020 at authors' institution. The follow-up duration, age, sex, affected side, and injury-to-surgery interval were collected; the neck-shaft angle of both hips, screw-apex distance (SAD) and the tip-apex distance (TAD)were measured; and the Garden classification, quality of reduction and presence of ONFH were evaluated.

RESULTS

The sample consisted of 37 males and 63 females, with 60 left and 40 right hips affected. The mean age of patients was 54.93 ± 12.24 years, and the mean follow-up was 56.3 ± 13.38 months. The overall incidence of ONFH was 13%. No significant difference was observed in the incidence of ONFH by affected side, age, fracture displacement, injury-to-surgery interval, neck-shaft angle deviation, or reduction quality. The SAD was significantly shorter in ONFH patients than in normal patients for all three screws (p = 0.02, 0.02, and 0.01, respectively).

CONCLUSIONS

The short SAD of all screws is associated with femoral head necrosis of FNFs treated with 3 cannulated screws. The short SAD indicated that screws malpositioning in the weight-bearing area of the femoral head, potentially harming the blood supply and compromising the anchorage of the primary compressive trabeculae in this region.