Biomechanical Evaluation of Extramedullary Versus Intramedullary Reduction in Unstable Femoral Trochanteric Fractures

Initial construct stability of long cephalomedullary nails with superior locking for a complex trochanteric fracture model AO31A2.2- a biomechanical study

BACKGROUND

Complex fractures of the trochanteric region, as well as fractures located in the directly subtrochanteric region, are controversially discussed around the world regarding the nail type to be used. A long nail is recommended by manufacturers but requires longer surgical and fluoroscopy times. A possible solution could be a nail with an appropriate length which can be locked in a minimally invasive manner by the main aiming device. We aimed to determine if such a nail model (DCN SL nail, SWEMAC, Linköping, Sweden) offers similar structural stability on biomechanical testing on artificial bone as a standard long nail when used to treat complex trochanteric fractures and compared it to long nails usually used in this setting.

METHODS

An osteoporotic bone model was chosen. The Swemac Hansson DCN Nail System was used as osteosynthesis material. Two types of nails were chosen: a superior lock nail which can be implanted with a singular targeting device, and a long nail with distal locking using free-hand technique. AO31A2.2 fractures were simulated in a standardised manner. Axial height of the construct, varus collapse, and rotational deformity directly after nail insertion were simulated. A Universal Testing Machine was used. Measurements were made with a stereo-optic tracking system.

FINDINGS

There was a detectable difference in the axial fracture movement resulting in narrowing of the fracture gap. There was no difference in varus collapse or rotational deformity between the nail variants CONCLUSION: We conclude that there are small differences which are clinically insignificant and that a superior locking nail can safely be used to manage complex trochanteric fractures.

Five states of reduction in OTA/AO A1.3 intertrochanteric fractures of the femur a biomechanical study

OBJECTIVE

This study aims to analyze the differences in mechanical stability of OTA/AO 31A1.3 intertrochanteric fractures under various reduction conditions.

METHODS

Twenty standard synbone artificial femur test bones were selected for the OTA/AO 31A1.3 intertrochanteric fracture model. The models were divided into five groups according to their reduction state: positive support, neutral support, negative support, varus fixation, and valgus fixation, with four specimens in each group. All models were fixed using PFNA intramedullary fixation and subjected to static axial compression tests. The subsidence displacement of the proximal femur under different loads and the axial stiffness of the model were measured to verify the mechanical stability of the OTA/AO 31A1.3 intertrochanteric fracture under different reduction conditions.

RESULTS

After the static axial compression test, the proximal femoral subsidence displacement in the positive support and neutral support groups was lower than that in the negative support, valgus fixation, and varus fixation groups (p < 0.001). The axial stiffness of the model was highest in the positive support group. Significant differences in subsidence displacement and axial stiffness were found between the groups (p < 0.001). The positive support group demonstrated the best mechanical stability, while the varus fixation group showed the poorest performance.

CONCLUSION

Positive support of the medial cortex can be regarded as the best reduction state for OTA/AO 31A1.3 intertrochanteric fractures, suggesting that this approach should be preferred during surgery to enhance mechanical stability and improve clinical outcomes. Conversely, varus fixation should be avoided due to its inferior stability.

Anteromedial cortical support reduction of intertrochanteric fractures-A review

The intertrochanteric fracture is a common fragility fracture typically resulting from low-energy falls. The functional outcome of intertrochanteric fractures is closely linked to the patient's underlying physical condition, intraoperative procedures, and postoperative complications. In terms of surgery, while timely surgery and appropriate internal fixation have demonstrated favorable outcomes, attention to intraoperative reduction is crucial. In recent years, there have been further developments in the evaluation of reduction of intertrochanteric fractures, particularly in the anteromedial cortical reduction, and these advances have been further scientifically elucidated in terms of their ability to provide stable fracture reduction and resist loss of reduction. In order to gain a comprehensive understanding of the anteromedial cortex theory, this article reviewed the anatomy, related theoretical progress, and controversies in recent years.

Finite element analysis of fixation stability according to reduction position for internal fixation of intertrochanteric fractures

In recent years, finite element analysis (FEA) has been instrumental in comparing the biomechanical stability of various implants for femur fracture treatment and in studying the advantages and disadvantages of different surgical techniques. This analysis has proven helpful for enhancing clinical treatment outcomes. Therefore, this study aimed to numerically analyze fixed stability according to location using FEA. In this study, a virtual finite element model was created based on a clinically anatomically reduced patient. It incorporated positive and negative support derived from intramedullary and extramedullary reduction from the anteroposterior (AP) view and neutral support from the lateral view. The generated model was analyzed to understand the biomechanical behavior occurring in each region under applied physiological loads. The simulation results of this study showed that the average von Mises stress (AVMS) of the nail when performing intramedullary reduction for femoral fixation was 187% of the anatomical reduction and 171% of the extramedullary reduction, and individually up to 2.5 times higher. In other words, intramedullary reduction had a very high possibility of fixation failure compared to other reduction methods. This risk is amplified significantly, especially in situations where bone strength is compromised due to factors such as old age or osteoporosis, which substantially affects the stability of fixation. Extramedullary reduction, when appropriately positioned, demonstrates greater stability than anatomical reduction. It exhibits stable fixation even in scenarios with diminished bone strength. In instances in which the bone density was low in the support position, as observed in the lateral view, the AVMS on the nail appeared to be relatively low, particularly in cases of positive support. Additionally, the femur experienced lower equivalent stress only in the extramedullary reduction-negative position. Moreover, by comparing different reduction methods and bone stiffness values using the same femoral shape, this study offers insights into the selection of appropriate reduction methods. These insights could significantly inform decision making regarding surgical strategies for intertrochanteric fractures.

Anteromedial Cortical Support in Reduction of Trochanteric Hip Fractures: From Definition to Application

➤ The concept of anteromedial cortical support (AMCS) serves as valuable guidance for the intraoperative reduction of trochanteric hip fractures.➤ Positive medial cortical support (MCS) and positive or neutral anterior cortical support (ACS) are desirable. Some evidence has suggested that positive MCS is potentially superior to neutral MCS.➤ Experimental studies underscore the vital importance of the anteromedial wall and reveal why positive MCS potentially outperforms neutral MCS.➤ Incorporating the AMCS concept, the Chang reduction quality criteria (CRQC) are a reliable alternative approach to evaluate the reduction quality of trochanteric hip fractures.

Anterior Malreduction is Associated With Lag Screw Cutout After Internal Fixation of Intertrochanteric Fractures

BACKGROUND

Lag screw cutout is a devastating complication after internal fixation of an intertrochanteric fracture. Although the tip-apex distance (TAD) is known to be associated with this complication, another factor we thought was potentially important-fracture reduction on an oblique lateral view-has not, to our knowledge, been explored.

QUESTIONS/PURPOSES

(1) Is a well-reduced fracture position on an oblique lateral view after internal fixation of intertrochanteric fracture associated with a lower odds of postoperative cutout, independently of the TAD? (2) Is postoperative sliding of the lag screw after fixation associated with postoperative cutout?

METHODS

Patients with intertrochanteric fractures who were at least 65 years old and who had been treated with internal fixation in one of six facilities between July 2011 and December 2017 were included. All patients in the study group had lag screw cutout, and controls were selected by risk-set sampling of age-matched and sex-matched patients using a ratio of 4:1 for patients from each hospital. Of the 2327 intertrochanteric fractures, there were 36 patients (0.02 per person-year), with a mean age of 85 years; 89% (32) were women. In the control group, there were 135 controls. There was no difference in age or sex between the two groups. Sagittal reduction was evaluated using an immediate postoperative oblique lateral radiograph (anterior malreduction versus anatomic reduction or posterior malreduction). The association between anterior malreduction and the odds of cutout was estimated by conditional logistic regression analysis with the TAD and interaction between the TAD and the reduced position as covariates. As a sensitivity analysis, we estimated whether sliding within 2 weeks postoperatively was associated with cutout.

RESULTS

After controlling for the potentially confounding variables of age and sex, we found that anterior malreduction was independently associated with a higher odds of cutout compared with anatomic reduction or posterior malreduction (adjusted OR 4.2 [95% CI 1.5 to 12]; p = 0.006). There was also an independent association between cutout and larger TAD (≥ 20 mm) (adjusted OR 4.4 [95% CI 1.4 to 14]; p = 0.01). However, the association between cutout and reduction was not modified by the TAD (adjusted OR of interaction term 0.6 [95% CI 0.08 to 4]; p = 0.54). Postoperative sliding ≥ 6 mm within 2 weeks was associated with higher odds of cutout after adjusting for age and sex (adjusted OR 11 [95% CI 3 to 40]; p < 0.001).

CONCLUSION

In patients older than 65 years with intertrochanteric fractures, anterior malreduction on a lateral oblique view was associated with much greater odds of postoperative cutout than anatomic reduction or posterior malreduction. Because anterior malreduction is within the surgeon's control, our findings may help surgeons focus on intraoperative reduction on an oblique lateral view to prevent cutouts. Although this factor is a reliable indicator, the results should be applied to cephalomedullary nails, because there was only one patient with cutout among those with sliding hip screws. Because this study was conducted in a homogenous Japanese population, future studies should focus on the association between anterior malreduction and cutout in people of different ethnicities, adjusting for confounding factors such as implant type and surgeon level.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Failure after intramedullary nailing for geriatric trochanteric fracture: does quality of fracture reduction on the AP and lateral planes show the same results?

PURPOSE

This study aimed to investigate the failure of trochanteric fracture fixation according to the quality of fracture reduction on the anteroposterior (AP) and lateral views.

METHODS

Data from 340 female and 152 male patients ≥ 60 years of age who underwent intramedullary nailing for a trochanteric fracture between 2016 and 2020 were analysed retrospectively. The quality of fracture reduction was classified as type A, type E, and type I on the AP view and type N, type A, and type P on the lateral view according to the relative position of the proximal and distal fragments. The failure rate was evaluated and compared according to the quality of fracture reduction. The risk factors of the fixation failure were investigated by comparison of variables between patients with and without failure and by regression analysis.

RESULTS

Patients with poor reduction, type I and type P had higher failure rates. However, a statistically significant difference was found only for patients with poor reduction (type P) on the lateral view (p < 0.001). Patients with failure showed significantly higher rates of poor reduction on the lateral view and AO/OTA type A3 fractures. The regression analysis also showed that poor reduction on the lateral view (odds ratio [OR] 12.70; 95% confidence interval [CI] 4.0-40.6; p < 0.001) and AO/OTA type A3 fractures (OR 5.40; 95% CI 1.24-23.49, p = 0.025) were risk factors for failure.

CONCLUSION

Poor reduction such as type P reduction was associated with failure after intramedullary nailing for trochanteric fractures. Surgeons should check the quality of fracture reduction carefully with the proper fluoroscopic view to prevent failure in geriatric patients with trochanteric fractures.

Risk Factors Associated with Fixation Failure in Intertrochanteric Fracture Treated with Cephalomedullary Nail

Purpose

Cephalomedullary (CM) nailing is widely performed in treatment of elderly patients with femoral intertrochanteric fractures. However, in cases of fixation failure, re-operation is usually necessary, thus determining factors that may contribute to fixation failure is important. In this study, we examined factors affecting the occurrence of fixation failure, such as age or fracture stability, after CM nailing in elderly patients.

Materials and Methods

This study was conducted retrospectively using registered data. From April 2011 to December 2018, CM nailing was performed in 378 cases diagnosed with femoral intertrochanteric fractures, and 201 cases were finally registered. Cases involving patients who were bed-ridden before injury, who died from causes unrelated to surgery, and those with a follow-up period less than six months were excluded.

Results

Fixation failure occurred in eight cases. Comparison of the surgical success and fixation failure group showed that the mean age was significantly higher in the fixation failure group compared with the control group (81.3±6.4 vs. 86.4±6.8; P=0.034). A significantly high proportion of unstable fractures was also observed (139/54 vs. 3/5; P=0.040), with a significantly high ratio of intramedullary reduction (176/17 vs. 5/3; P=0.034). A significantly higher ratio of unstable fractures compared with that of stable fractures was observed in the intramedullary reduction group (132/49 vs. 10/10; P=0.033).

Conclusion

Fixation failure of CM nailing is likely to occur in patients who are elderly or have unstable fracture patterns. Thus, care should be taken in order to avoid intramedullary reduction.

Positive medial cortical support versus anatomical reduction for trochanteric hip fractures: Finite element analysis and biomechanical testing

BACKGROUND AND OBJECTIVES

The anatomical reduction (AR) is usually considered the best option for fractures. Nevertheless, in unstable trochanteric hip fractures (UTHF), previous clinical reports found that the positive medial cortical support (PMCS, an over-reduction technique) attained higher mechanical stability, but this challenging clinical finding still needs experimental validation.

METHODS

This study constructed in-silico and biomechanical PMCS and AR models, with the use of the most clinically-representative geometry design of fracture models, the multi-directional design in FE analysis, and the subject-specific (osteoporotic) bone material properties, to make the models better mimic the actual condition in clinical settings. Then multiple performance variables (von-Mises stress, strain, integral axial stiffness, displacement, structural changes, etc.) were assessed to uncover details of integral and regional stability.

RESULTS

Among in-silico comparison, PMCS models showed significantly lower maximum displacement than AR models, and the maximum von Mises stress of implants (MVMS-I) was significantly lower in PMCS models than in AR models (highest MVMS-I in -30°-A3-AR of 1055.80 ± 93.37 MPa). Besides, PMCS models had significantly lower maximum von Mises stress along fracture surfaces (MVMS-F) (highest MVMS-F in 30°-A2-AR of 416.40 ± 38.01 MPa). Among biomechanical testing comparison, PMCS models showed significantly lower axial displacement. Significantly lower change of neck-shaft angle (CNSA) was observed in A2-PMCS models. A fair amount of AR models converted into the obvious negative medial cortical support (NMCS) condition, whereas all PMCS models kept the PMCS condition. The results were also validated through comparison to previous clinical data.

CONCLUSIONS

The PMCS is superior to the AR in the UTHF surgery. The current study opens up the second thought of the role of over-reduction technique in bone surgery.

AP3×ML3 reduction quality classification for femoral trochanteric fractures: validation for reliability focusing on positive medial cortical support

INTRODUCTION

This study evaluated the validity of the AP3 × ML3 reduction quality classification, which applies the concept of positive medial cortical support.

METHODS

A total of 120 trochanteric fractures classified as AO Foundation/Orthopedic Trauma Association 31A1 and A2 were retrospectively analyzed. The validity of the AP3 × ML3 classification was evaluated by comparison with the Baumgaertner reduction quality criteria. When using the AP3 × ML3 classification, reduction quality was divided into three classes based on the degree of anterior cortical contact between the proximal and distal fragments. Reduction quality was also divided into three classes when using the Baumgaertner criteria. The frequency of mechanical complications, including cut-out, delayed union, and excessive migration of the lag screw, was retrospectively assessed. Intra-observer and inter-observer reliability was assessed using the intraclass correlation coefficient (ICC).

RESULTS

Mechanical complications included 4 cases of cutout (3.3%) and 1 of delayed union (0.8%). Mechanical complications occurred for all levels of reduction quality in both classifications, except for the acceptable of the Baumgaertner criteria. When reduction quality was rated as good, acceptable, and poor the incidence of mechanical complications was 2.5%, 5.7%, and 16%, respectively, under the AP3 × ML3 classification and 3.3%, 0%, and 15.0%, respectively, under the Baumgaertner criteria. The ICC was 0.80 for intra-observer reliability and 0.57 for inter-observer reliability when using the AP3 × ML3 classification and 0.85 and 0.34, respectively, when using the Baumgaertner criteria.

CONCLUSION

The AP3 × ML3 classification was reliable and easy to use compared with the widely used Baumgaertner reduction quality criteria. Level of evidence 4.