A novel angle on helical blade placement in trochanteric fractures - The axis-blade angle

Proposal of a modified tip apex distance for prediction of lag screw cut-out in trochanteric hip fractures

INTRODUCTION

Lag screw cut-out is a serious complication of dynamic hip screw fixation of trochanteric hip fractures. The lag screw position has been acknowledged as one of the important factors affecting the lag screw cut-out. We propose a modification of the Tip Apex Distance (TAD) and hypothesise that it could improve the reliability of predicting lag screws cut-out in these injuries.

MATERIALS AND METHODS

A retrospective study was conducted for hip fracture entries in the period from Jan 2018 to July 2022. A hundred and nine patients were suitable for the final analysis. The modified TAD was measured in millimetres based on the sum of the traditional TAD in the lateral view and the net value of two distances in the AP view, the first distance is from the tip of the lag screw to the opposite point on the femoral head along the axis of the lag screw while the second distance is from that point to the femoral head apex. The first distance is a positive value, whereas the second distance is positive if the lag screw is superior and negative if inferior. A receiver operating characteristic curve was used to evaluate the reliability of the different parameters assessing the lag screw position within the femoral head.

RESULTS

Reduction quality, fracture pattern as per the AO/OTA classification, TAD, Calcar Referenced TAD, Axis Blade Angle, Parker's ration in the AP view, Cleveland Zone 1, and modified TAD were statistically associated with lag screw cut-out. Among the tested parameters, the modified TAD had 90.1% sensitivity and 90.9% specificity for lag screw cut-out at a cut-off value of 25 mm with a P-value < 0.001.

CONCLUSION

The modified TAD had the highest reliability in the prediction of lag screw cut-out. A value ≤ 25 mm could potentially protect against lag screw cut-out in trochanteric hip fractures.

The Impact of Banana-Shaped Fragments on Trochanteric Hip Fractures Treated by PFNA

Background

Regarding trochanteric hip fractures, one type of posterior coronal fragments was described as the "banana-shaped fragment", while the impact of the banana-shaped fragment on mechanical stability has not been further studied. The current study investigated the association between the banana-shaped fragment and mechanical complications after surgery.

Methods

This retrospective cohort study included 273 patients treated by proximal femoral nail antirotation (PFNA) in the full analysis. The age, the sex, the fracture side, the follow-up time, the American Society of Anesthesiologists classification, the operators, the fracture classification, the tip-apex distance, the blade positions, the reduction quality and the bone mineral density were analyzed in relation to mechanical complications, through univariate and multivariate approaches.

Results

Mechanical complications happened in 33 patients. The banana-shaped fragment (adjusted odds ratio 5.240, 95% CI 2.172 to 12.641; p < 0.001), the tip-apex distance and the reduction quality showed significant association with mechanical complications in both univariate and multivariate analysis. Moreover, for 118 patients with the banana-shaped fragment, we found that the use of wire cerclage couldn't significantly lower the rates of mechanical complications (p = 0.648).

Conclusions

The banana-shaped fragment had a negative impact on mechanical stability of trochanteric hip fractures treated by PFNA. In the perioperative period, the BSF should be carefully evaluated, and its specific handling deserves further study.

Computational evaluation of the axis-blade angle for measurements of implant positions in trochanteric hip fractures: A finite element analysis

BACKGROUND

Recently, a novel approach axis-blade angle (ABA) was developed to measure implant positions during trochanteric hip fracture surgery. It was defined as the sum of two angles α and β measured between the femoral neck axis and helical blade axis in anteroposterior and lateral X-ray films, respectively. Although its clinical practicability has been confirmed, the mechanism is yet to be investigated by means of finite element (FE) analysis.

METHODS

Computed tomography images of four femurs and dimensions of one implant at three angles were obtained to construct FE models. For each femur, 15 FE models in an arrangement (intramedullary nails at three angles multiplying five blade positions) were established. Under the simulation of normal walking loads, the ABA, von Mises stress (VMS), maximum/minimum principal strain and displacement were analyzed.

RESULTS

When the ABA increased, all outcome indicators initially decreased till reaching inferior-middle site and then increased while the blade positions within the femoral head shifted from the superior-anterior quadrant toward the inferior-posterior quadrant, where the ABA were higher. Only the peak VMS of implant models in the inferior-posterior quadrant (particularly the inferior-middle site within) with blades in did not reach the yielding (risky) cut-off.

CONCLUSIONS

From the perspective of angles, ABA, this study demonstrated the inferior-posterior quadrant as the relatively stable and safe regions, especially the inferior-middle site within. This was similar but more elaborate compared with previous studies and clinical practice. Therefore, ABA could be employed as a promising approach to anchor the implants into the optimal region.

Comparison of Baumgaertner and Chang reduction quality criteria for the assessment of trochanteric fractures

Objectives

Different criteria for assessing the reduction quality of trochanteric fractures have been reported. The Baumgaertner reduction quality criteria (BRQC) are relatively common and the Chang reduction quality criteria (CRQC) are relatively new. The objectives of the current study were to compare the reliability of the BRQC and CRQC in predicting mechanical complications and to investigate the clinical implications of the CRQC.

Methods

A total of 168 patients were assessed in a retrospective observational study. Clinical information including age, sex, fracture side, American Society of Anesthesiologists (ASA) classification, tip-apex distance (TAD), fracture classification, reduction quality, blade position, BRQC, CRQC, bone quality, and the occurrence of mechanical complications were used in the statistical analysis.

Results

A total of 127 patients were included in the full analysis, and mechanical complications were observed in 26 patients. The TAD, blade position, BRQC and CRQC were significantly associated with mechanical complications in the univariate analysis. Only the TAD (p = 0.025) and the CRQC (p < 0.001) showed significant results in the multivariate analysis. In the comparison of the receiver operating characteristic curves, the CRQC also performed better than the BRQC.

Conclusion

The CRQC are reliable in predicting mechanical complications and are more reliable than the BRQC. Future studies could use the CRQC to assess fracture reduction quality. Intraoperatively, the surgeon should refer to the CRQC to achieve good reduction in trochanteric fractures.

Cite this article: Bone Joint Res 2019;8:502–508.