Predictors of failure following fixation of intertrochanteric fractures with proximal femoral nail antirotation

Impact of the nail insertion angle on the wedge effect in intramedullary nail fixation of intertrochanteric hip fractures

BACKGROUND

The wedge effect is known to be influenced by the insertion of the proximal femoral intramedullary nail through the fracture line and the large proximal diameter of the nail. However, the impact of the nail insertion angle (NIA) on the wedge effect remains unclear. This study aimed to investigate: (1) how to evaluate the NIA intraoperatively, (2) whether the NIA is associated with the wedge effect, (3) whether the NIA can serve as a reliable predictor of the wedge effect, (4) which factors affect the NIA, and (5) which surgical techniques can prevent the occurrence of the wedge effect associated with the NIA.

HYPOTHESIS

We hypothesized that an excessive NIA is related to the wedge effect and that lateral deviation of the entry point is associated with an excessive NIA.

PATIENTS AND METHODS

Intraoperative fluoroscopy images of patients who underwent intramedullary nail fixation for intertrochanteric hip fractures between 2013 and 2023 were analyzed. NIA and insertion point distance (IPD) were measured on hip anteroposterior radiographs with the guidewire inserted. Femoral shaft lateralization (FSL) and neck-shaft angle (NSA) were measured on hip anteroposterior radiographs before and after nail insertion; differences in FSL and NSA were calculated. A negative difference in FSL combined with a positive difference in NSA indicated the occurrence of the wedge effect. Pearson's correlation test was used to determine relationships between continuous variables (NIA, FSL, NSA, and IPD). Binary logistic regression analyzed the association between NIA and the wedge effect. Receiver operating characteristic (ROC) curve analysis was used to determine the threshold value of NIA, with predictive performance assessed using the area under the ROC curve (AUC). Other potential factors influencing the wedge effect were also examined.

RESULTS

A total of 408 patients were included. The mean NIA was 15.61 ± 4.49 °. Post-nail insertion, the average increase in FSL was 3.20 mm, and the average decrease in NSA was 1.90 °. Pearson's correlation test revealed that NIA was negatively correlated with the difference in FSL (R = 0.565, P < 0.001) and positively correlated with the difference in NSA (R = 0.509, P < 0.001). Binary logistic regression showed a significant correlation between NIA and the wedge effect (P < 0.001). ROC analysis indicated that the AUC for NIA was 0.813, with an optimal cutoff point of 14.85 °. IPD was positively correlated with NIA (R = 0.519, P < 0.001). Unstable fractures were associated with increased lateralization of the femoral shaft after nail insertion (P = 0.003).

DISCUSSION

The NIA is positively correlated with the wedge effect in intramedullary nail fixation of intertrochanteric hip fractures. The wedge effect tends to occur when the NIA is >14.85 °, particularly in unstable fractures. Lateral deviation of the entry point is associated with an excessive NIA. Adducting the affected limb, moving the entry point slightly medial and using a medial pusher may help control the NIA to less than 14.85 ° to reduce the wedge effect.

LEVEL OF EVIDENCE

III.

Application of deep learning algorithms in classification and localization of implant cutout for the postoperative hip

OBJECTIVE

This study aims to explore the feasibility of employing convolutional neural networks for detecting and localizing implant cutouts on anteroposterior pelvic radiographs.

MATERIALS AND METHODS

The research involves the development of two Deep Learning models. Initially, a model was created for image-level classification of implant cutouts using 40191 pelvic radiographs obtained from a single institution. The radiographs were partitioned into training, validation, and hold-out test datasets in a 6/2/2 ratio. Performance metrics including the area under the receiver operator characteristics curve (AUROC), sensitivity, and specificity were calculated using the test dataset. Additionally, a second object detection model was trained to localize implant cutouts within the same dataset. Bounding box visualizations were generated on images predicted as cutout-positive by the classification model in the test dataset, serving as an adjunct for assessing algorithm validity.

RESULTS

The classification model had an accuracy of 99.7%, sensitivity of 84.6%, specificity of 99.8%, AUROC of 0.998 (95% CI: 0.996, 0.999) and AUPRC of 0.774 (95% CI: 0.646, 0.880). From the pelvic radiographs predicted as cutout-positive, the object detection model could achieve 95.5% localization accuracy on true positive images, but falsely generated 14 results from the 15 false-positive predictions.

CONCLUSION

The classification model showed fair accuracy for detection of implant cutouts, while the object detection model effectively localized cutout. This serves as proof of concept of using a deep learning-based approach for classification and localization of implant cutouts from pelvic radiographs.

A Good Tip-Apex Distance Does Not Make Up For a Poor Reduction in Intertrochanteric Hip Fractures Treated with an Cephalomedullary Nail: The Utility of the Neck-Shaft Angle in Preventing Fixation Failure

PURPOSE

Determine if any fracture characteristics or radiographic parameters were predictive of fixation failure [FF] within 1 year following cephalomedullary nailing for intertrochanteric fractures.

METHODS

A consecutive series of intertrochanteric hip fracture patients (AO/OTA 31A) treated with a cephalomedullary nail were reviewed. Pre-fixation (neck-shaft angle [NSA], distance from ischial tuberosities to greater and lesser trochanters, integrity of lesser trochanter, and fracture angulation) and post-fixation (post-fixation NSA, posteromedial cortex continuity, lag screw position, tip to apex distance [TAD], and post-fixation angulation and translation) radiographic parameters were measured by blinded independent reviewers. The FF and non-FF groups were statistically compared. Logistic regression was performed to determine radiographic parameter correlates of FF.

RESULTS

Of 1249 patients, 23 (1.8%) developed FF within 1 year. The FF patients were younger than their non-FF counterparts (77.2 years vs 81.0 years, p=0.048), however there were no other demographic differences. The FF cohort did not differ in frequency of TAD over 25 mm (4.3% vs 9.6%, p=0.624) and had decreased mean TAD (13.6mm vs 16.3mm, p=0.021) relative to the non-FF cohort. The FF cohort had a higher rate of a post-fixation coronal plane NSA more than 10° different from the contralateral side (delta NSA>10°, 34.8% vs 13.7%, p=0.011) with the majority fixed in relative varus. For every 1° increase in varus compared to the contralateral side the odds of FF increased 7% (OR=1.065, 95%CI[1.005-1.130], p=0.034) on univariate analysis. On univariate logistic regression, patients with an absolute post-fixation NSA of 10° or more of varus compared to contralateral were significantly more likely to have a FF (OR=3.139, 95%CI[1.067-8.332], p=0.026).

CONCLUSION

Despite an acceptable TAD, post-fixation NSA in relative varus as compared to the contralateral side was significantly associated with failure in intertrochanteric hip fractures fixed with a cephalomedullary nail.

LEVEL OF EVIDENCE

Prognostic Level III.

Finite element analysis of basicervical femoral neck fracture treated with proximal femoral bionic nail

BACKGROUND

Dynamic hip screws (DHS) and proximal femoral nail anti-rotation (PFNA) were recommended for basicervical femoral neck fracture (BFNF), however, with high rate of postoperative femoral neck shortening. The proximal femoral bionic nail (PFBN) was designed to decrease the postoperative complications associated with DHS and PFNA. The aim of this study is to compare the biomechanical characters of DHS, PFNA, and PFBN for fixation of BFNF.

METHODS

Using finite element analysis, we created a three-dimensional model of the BFNF for this investigation. The PFBN group, the PFNA group and the DHS + DS group were our three test groups. For each fracture group, the von Mises stress and displacements of the femur and internal fixation components were measured under 2100 N axial loads.

RESULTS

The PFBN group demonstrated the lowest stress on the implants, significantly lower than the PFNA and DHS + DS groups. In terms of stress on the implants, the PFBN group exhibited the best performance, with the lowest stress concentration at 112.0 MPa, followed by the PFNA group at 124.8 MPa and the DHS + DS group at 149.8 MPa. The PFBA group demonstrated the smallest displacement at the fracture interface, measuring 0.21 mm, coupled with a fracture interface pressure of 17.41 MPa, signifying excellent stability.

CONCLUSIONS

Compared with DHS and PFNA, PFBN has advantages in stress distribution and biological stability. We believe the concept of triangle fixation will be helpful to reduce femoral neck shortening associated with DHS and PFNA and thus improve the prognosis of BFNF.

Complication Rates and Survival of Nonagenarians after Hip Hemiarthroplasty versus Proximal Femoral Nail Antirotation for Intertrochanteric Fractures: A 15-Year Retrospective Cohort Study of 113 Cases

OBJECTIVE

Intertrochanteric fracture is a very common but serious type of hip fracture in nonagenarians. The surgical treatment remains a significant challenge for orthopedists. The objective of this study was to investigate postoperative complications and survival outcomes compared between bipolar hemiarthroplasty (HA) and proximal femoral nail anti-rotation (PFNA) in nonagenarians with intertrochanteric fractures, and to evaluate the efficacy and safety of the two surgical procedures in this patient population.

METHODS

A total of 113 consecutive nonagenarians who underwent bipolar HA or PFNA for the treatment of intertrochanteric fractures from January 2006 to August 2021 were retrospectively studied in the current paper. There were 34 males and 79 females, with a mean age of 92.2 years (range 90-101 years) at the time of operation. The average duration of follow-up was 29.7 months (range 1-120 months). The full cohort was divided into bipolar HA (77 cases) and PFNA (36 cases) groups. Damage control orthopedics was used to determine the optimal surgery time and assist in perioperative management. A restrictive blood transfusion strategy was employed, along with appropriate adjustments under multidisciplinary assessment, throughout the perioperative period. Perioperative clinical information and prognostic data were analyzed. Kaplan-Meier survival curves were used for survival analysis, and landmark analysis divided the entire follow-up period into 1-12 months (short-term), 13-42 months (medium-term) and 43-120 months (long-term) according to the configurations of Kaplan-Meier survival curves.

RESULTS

Both groups had similar general variables except for the proportion of high adjusted Charlson comorbidity index (aCCI) (≥6 points) (6.5% in bipolar HA group and 22.2% in PFNA group, p = 0.024). Intraoperative blood loss and transfusion requirements were greater, and the intraoperative transfusion rates were higher in the bipolar HA group compared to the PFNA group (all p < 0.05). The complications rates, 1- to 60-month cumulative all-cause mortality, postoperative optimal Harris hip score (HHS), and Barthel index (BI) presented no significant difference between the two groups (all p > 0.05). Both groups had similar overall survival curves (p = 0.37). However, landmark analysis revealed that bipolar HA group exhibited higher survival rates in medium-term (p = 0.01), while similar survival rates were observed in the short- and long-term post-operation periods (both p > 0.05). Cox regression with survival-time-dependent covariate calculated the hazard ratio (HR) of bipolar HA was 0.41 in medium-term (p = 0.039).

CONCLUSION

Bipolar HA is equally effective and reliable as PFNA for treating intertrochanteric fractures in nonagenarians. Despite resulting in more intraoperative blood loss and transfusions, bipolar HA therapy is associated with a higher medium-term survival rate compared to PFNA treatment. The application of damage control orthopedics and precise perioperative patient blood management could contribute to the positive clinical outcomes observed in this patient population.

[Research progress on evaluation methods for head-neck nail position in femoral intertrochanteric fractures]

Objective

To summarize the research progress on the evaluation methods of head-neck nail positions in femoral intertrochanteric fractures.

Methods

The literature about the evaluation methods of head-neck nail positions for femoral intertrochanteric fractures in recent years was extensively reviewed, and research progress in the aspects of evaluation methods, clinical applications, and limitations were summarized.

Results

The position of head-neck nails in femoral intertrochanteric fractures is closely related to postoperative complications of head-neck nail cutting. Currently, the tip-apex distance (TAD) and femoral head zoning are widely used to evaluate the position of head-neck nails. The main opinion in the literature is that the use of TAD and femoral head zoning can effectively reduce the incidence of head-neck nails cutting. Parker's ratio, as one of the evaluation methods, has been controversial in subsequent studies and has not been widely used in clinical practice. The TAD as referenced to the calcar (CalTAD), which was modified based on TAD, has been gradually accepted by the clinic, but whether it is better than the TAD has not yet been conclusively determined. In recent years, new evaluation methods have been proposed to supplement the previous evaluation methods, such as the tip-neck distance ratio (TNDR) and the standardized TAD (STAD) to avoid the limitations of the TAD and the CalTAD by the volume of the femoral head, and the axis-blade angle (ABA) to supplement the direction of the head-neck nails channel, but at present the clinical application is relatively underutilized, and the validity of the method needs to be further verified.

Conclusion

Currently, there are many methods for evaluating the position of head-neck nails in femoral intertrochanteric fractures, TAD<25 mm combined with head-neck nails placed in the middle-middle quadrant or lower-middle quadrant of the femoral head division is currently a highly recognized assessment in the literature, but the optimal assessment is still controversial, and further research needs to be studied.

Biomechanical analysis analyzing association between bone mineral density and lag screw migration

A proximal femoral nail using a helical blade (HB) is commonly utilized to treat proximal femoral fracture but cut through failure of the lag screws is one of the devastating complications following the surgery. While controversial, one of the potential risk factors for cut through failure is poor bone strength which can be predicted by measuring bone mineral density (BMD). In this study, we performed a biomechanical test on the fractured femoral head to validate whether the indirectly measured BMD from the contralateral hip or that measured directly from the retrieved femoral head can elucidate the structural strength of the fractured femoral head and thereby can be used to predict migration of lag screws. Our result showed that directly measured BMD has a significant correlation with the HB migration on the osteoporotic femoral head. However, while the BMDs measured from the contralateral femoral neck or total hip is the most widely used parameter to predict the bone strength of the fractured femur, this may have limited usability to predict HB migration.

Predictors of and predictive nomogram for cut-out of proximal femur nail anti-rotation device in intertrochanteric fractures

PURPOSE

This study determined independent predictors and developed a predictive nomogram for failed correction of intertrochanteric fractures due to cut-out of the proximal femur nail anti-rotation (PFNA) device.

METHODS

Demographic and radiological data of 592 adult patients with intertrochanteric fractures (AO 31A) treated by PFNA were collected retrospectively. Independent predictors of cut-out were obtained through univariate and multivariate analyses, and a predictive nomogram was established. The discrimination, calibration, and clinical utility of the nomogram were based on receiver operating characteristic curve (AUC), concordance index (C-index), calibration curve, and decision curve analysis, respectively.

RESULTS

Overall, 18 (3.04%) cases of cut-out occurred. Independent predictors according to the multivariate analysis were body mass index (BMI), poor-to-acceptable quality of reduction, PFNA blade position, and tip-apex distance (TAD). AUC of the nomogram was 0.849, and C-index was 0.849 (95% CI [0.844-0.854]). Bootstrapping yielded a corrected C-index of 0.849. The calibration and decision curves indicated good agreement and clinical benefit of the nomogram.

CONCLUSION

A reliable predictive nomogram was developed for cut-out of the PFNA in intertrochanteric fractures, based on BMI, quality of reduction, blade position, and TAD.

The predictive value of the Singh index for the risk of InterTAN intramedullary fixation failure in elderly patients with intertrochanteric fractures

Background

To investigate the predictive value of the Singh index for the risk of InterTAN intramedullary fixation failure in elderly patients with intertrochanteric fracture to guide clinical treatment.

Methods

A total of 360 patients were divided into the Singh (I ~ II) (n = 120), Singh (III ~ IV) (n = 120) and Singh (V ~ VI) (n = 120) groups. Visual analog scale (VAS) and Harris scores were recorded at 1, 6, 12, 18 and 24 months after the operation. The correlation between the Singh index and the T-score of the total hip and femoral neck was analyzed. Logistic regression was used to analyze the relationship between the Singh index and internal fixation failure; the types of internal fixation failure were also analyzed.

Results

The Harris scores of the Singh (I ~ II) group were lower than those of the Singh (III ~ IV) and Singh (V ~ VI) groups 12, 18 and 24 months after surgery (P < 0.05). The Singh index was significantly correlated with the T-score of the total hip and femoral neck (P = 0.00, r = 0.89; P = 0.00, r = 0.83). The Singh (I ~ II) group had the lowest internal fixation survival rate within 24 months (P = 0.01). The Singh index was an independent predictor of internal fixation failure (P < 0.05). Lag screw cutting-out was the main type of internal fixation failure in the three groups (P = 0.00).

Conclusion

The Singh index is significantly correlated with the bone mineral density of the femoral neck and total hip. The Singh (I ~ II) group had lower Harris scores and a lower internal fixation survival rate than the other two groups. The Singh index is an independent predictor of internal fixation failure, especially lag screw cutting-out, after InterTAN fixation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05741-8.

Influence of the PFNA screw position on the risk of cut-out in an unstable intertrochanteric fracture: a computational analysis

The position of the lag screw in the femoral head is a key factor to cut-out, the most reported complication in the internal fixation of intertrochanteric fractures. Considering that the best position for the lag screw remains controversial, the aim of this study was to evaluate the influence of different lag screw positions on the risk of cut-out of an unstable intertrochanteric fracture fixed with a Proximal Femoral Nail Anti-Rotation (PFNA) implant. The relationship between cut-out and the tip-apex distance (TAD) or the calcar referenced tip-apex distance (CalTAD) was also investigated. Finite element models of one male and one female femur treated with a PFNA implant were developed considering the lag screw positioned centrally and inferiorly on the anteroposterior view, and for each of these, the screw tip at 4 discrete positions along its longitudinal axis. All 8 positions simulated for each femur considered the lag screw in a centre position on the lateral view. The risk of cut-out was evaluated for two loading conditions assuming it is related with high compressive strains. The bone region at the fracture line, near the tip of the missing medial fragment, was always the most concerning regarding high compressive strains. The inferior positioning of the lag screw reduced the volume of bone susceptible to yielding compared to the centre positioning. The deep placement of the screw tip improved the outcome for both centre and inferior positions. The results suggested the inferior and deep placement of the screw to be the best position to reduce the risk of cut-out. The volume of bone susceptible to yielding was found not to be correlated to TAD or CalTAD, suggesting that further investigation is necessary to identify other, more reliable, predictors of cut-out.

Is the fracture morphology in the sagittal plane important in determining the ideal placement of the lag screw in intertrochanteric femoral fractures?: Ideal lag screw placement in intertrochanteric fractures in the sagittal plane

OBJECTIVE

The aim of this study was to determine the ideal placement of the lag screw taking into account the fracture morphology in the sagittal plane.

MATERIALS AND METHODS

Three different morphology of fractures were created on the sagittal plane in femur models obtained in 3D CT scanning: posteriorly angled (Type A), transverse (Type B) and anteriorly angled (Type C). The lag screw was applied in each of the three fracture morphology as neutral, anteverted and retroverted in the sagittal plane. The nine models created were transferred to the Ansys Workbench program and analyzes were performed.

RESULTS

In Type A fracture, the stress value at the lag screw apex increase as the lag screw placement changes from the anteverted position to the retroverted position. It decreases in the Type B and Type C fractures. As the lag screw placement is changed towards the anteverted position, the stress at the lag screw-nail junction decreases in the Type A fracture and increases in the Type C fracture . There is no significant change in the Type B fracture. As the lag screw placement is changed towards the anteverted position, the stress in the calcar region increases in Type A fractures and decreases in Type C fractures. There is no significant change in type B fractures.

CONCLUSION

While the ideal lag screw placement in a type A fracture in the sagittal plane is the retroverted placement, the anteverted placement is ideal placement in type C fractures. Fracture morphology in the sagittal plane should be taken into account in the lag screw placement.

The suitable fixation for unstable intertrochanteric fractures: A protocol of comparative clinical study

BACKGROUND

Normally taking the surgery is the standard treatment, between sliding hip screw (SHS) and utilizing proximal femoral nail antirotation (PFNA) for intramedullary fixation, it is still not certain which one work better for this type of fracture. Our purpose for this study was to determine the optimum choice of implant for a patient with an unstable intertrochanteric fracture.

METHODS

In our hospital, a reflective analysis was conducted of all unstable intertrochanteric fractures treated with either a SHS or PFNA fixation between February 2015 and February 2018. The rules of choosing patients were the following: older age of more than 60, unstable intertrochanteric fractures, and willingness to take clinical and radiographic follow-up researches for over 12 months. In this case, patients bearing former hip surgery at any side were removed from the candidates. Demographic characteristics collected effective information including gender, date of operation, and other relevant information. Postoperative outcome measures included operation time, total blood loss amount, validated mobility score, surgery-related syndrome, and tip-apex length. The patients were re-examined at three time periods: 3 weeks, 3 months, and 1 year. The result of P < .05 was considered to be statistically significant.

RESULTS

We were able to directly compare the outcomes of PFNA vs SHS techniques and might reveal a better technique in treatment of an unstable intertrochanteric fracture.

TRIAL REGISTRATION

This study protocol has been registered in Research Registry (researchregistry6057).