Impact of tip-apex distance and femoral head lag screw position on treatment outcomes of unstable intertrochanteric fractures using cephalomedullary nails

Proximal Femur Fractures - How Decisive are Reduction and the Chosen Implant?

Proximal femoral fractures are frequent and complex injuries requiring prompt and targeted care. Numerous treatment strategies have been described, some of which have been assessed and clinically implemented clinically. The aim of surgical is always the restoration of a pain-free and stable extremity. Mostly elderly patients are affected and treatment is associated with high postoperative complications and mortality rates. With increasing numbers of patients, the topic is of great medical and economic relevance. In this work, the choice of implants for the osteosynthesis of proximal femoral fractures - as depending on the fracture type - will be examined, as based on a review of current literature. Standard care includes cannulated screws, sliding hips screws and cephalomedullary nails. In addition, the influence of implant positioning, fracture reduction and additional measures such as cement augmentation are evaluated and discussed. Careful fracture reduction and the quality of implant positioning are paramount in order to avoid complications.

How much of the superolateral femoral neck should be removed in intramedullary nail fixation for intertrochanteric fracture?

The objective of this study was to measure how much of the superolateral femoral neck should be removed to reduce the incidence of wedge effect. Simulating surgery: Computed Tomography images of 131 intertrochanteric fracture patients were included, three-dimensionally reconstructed, virtually reduced and implanted with Proximal Femoral Nail Antirotation blade-Ⅱ(PFNA-Ⅱ) nail. The antero-posterior length and media-lateral width of the intersection between superolateral femoral neck and PFNA-Ⅱ nail were measured. Retrospective study: The pre- and postoperative CT of 30 patients were collected. The average varus angle of the neck-shaft angle and the correlation between the angles and the difference in the actual and estimated width of the fragments removed were measured. Models of 108 patient were selected for analysis. The average antero-posterior length and media-lateral width were 14.46 mm (14.00-14.93 mm) and 9.33 mm (8.79-9.87 mm), respectively. The AO/OTA classification was not significantly associated with the outcome, but the gender was. In the retrospective study, the mean value of the varus angles was -4.58° (SE = 6.85°), and the difference of width was strongly positively correlated with the varus angle with a correlation coefficient of 0.698. Results obtained in this study can improve the understanding of this region and help surgeons to make appropriate preoperative planning to reduce the incidence of wedge effect. Retrospective study provided effective proof of the reliability of this study.

Intraoperative fluoroscopic safety assessment of femoral head implants with 3-dimensional risk parameters to minimize cut-out

OBJECTIVE

This study aimed to introduce a method to extract the 3-dimensional spatial position of the femoral head implant from 2-dimensional fluoroscopic projections, allowing surgeons to assess fixation much more accurately and prevent cut-out complications in proximal femoral nailing.

METHODS

To define a safety region for the tip in the femoral head, a novel 3-dimensional distance-based risk parameter called TSD3D was introduced. An intersection algorithm was developed that solely takes the fluoroscopic anteroposterior and lateral distances to reveal the 3-dimensional location of the screw or Kirschner wire tip, enabling the utilization of the 3-dimensional parameter. Orthogonal per- spectives of 6 femur proximal bone substitutes with randomly inserted Kirschner wires were imaged under fluoroscopy. The developed algorithm was used to calculate the implant tip location in 3-dimensional from 2-dimensional images for each case. Algorithm accuracy was validated with the computed tomography-obtained 3-dimensional models of the same femur substitutes.

RESULTS

The newly introduced risk parameter successfully visualizes 3-dimensional safety regions. Utilizing the 2-dimensional fluoro- scopic distances as inputs to the algorithm, the 3-dimensional position of the implanted Kirschner wire tip is calculated with a maximum of 9.8% error for a single Cartesian-coordinate measurement comparison.

CONCLUSION

By incorporating the newly introduced 3-dimensional risk parameter, surgeons can more precisely evaluate the position of the implant and avoid cut-out complications, instead of relying solely on misleading 2-dimensional fluoroscopic projections of the femoral head.

Trochanteric Nails for the Reduction of Intertrochanteric Fractures: A Biomechanical Analysis Based on Finite Element Analysis and DIC System

Purpose

Intertrochanteric fractures are common among femoral fractures in the elderly population. The trochanteric nail is a standard internal fixator used in treating femoral intertrochanteric fractures. The technique of femoral fracture reduction affects the postoperative outcome. Here, we applied finite element analysis (FEA) to study mechanical effects of different reduction approaches using the trochanteric nail in treating both stable and unstable intertrochanteric fractures.

Methods

We combined FEA and in vitro experiments using a digital imaging correlation (DIC) technique to study effects of different alignment conditions after treating 4 cases of intertrochanteric fractures using the trochanteric nail system. A downward force of 2250 N was applied to the femoral head, and the distal end of the femur was fixed. The observed indicators were the femur displacement, together with the stress on the femur and trochanteric nail system. In addition, the displacement distribution was analyzed using DIC.

Results

In the case of space reduction, the force was transmitted by the trochanteric nail system, resulting in greater stress imposed on the femur or the trochanteric nail system. In the case of closed reduction, the stress was much smaller. In the case of unstable fracture reduction, closed reduction was associated with a smaller contact area at the fracture site, resulting in greater stress on both trochanter and the trochanteric nail system.

Conclusion

When the trochanteric nail system was used for fixation, the fracture site was well aligned, reducing the stress on the femur or the trochanteric nail.

Integrated dual lag screws versus single lag screw cephalomedullary nail constructs: a meta-analysis and systematic review

BACKGROUND/AIM

This study aims to determine the safety and efficacy of integrated dual lag screw (IDL) cephalomedullary nails (CMN) when compared with single lag screw (SL) constructs, in the internal fixation of intertrochanteric femoral fractures.

METHODS

The Smith & Nephew InterTan IDL was compared with SL CMN group consisting of the Stryker Gamma-3 (G3) and Synthes Proximal Femoral Nail Antirotation (PFNA) CMN. A multi-database search was performed according to PRISMA guidelines. Data from studies assessing the clinical and radiological outcomes, complications and perioperative parameters of InterTan versus G3 or PFNA CMN in patients with intertrochanteric femoral fractures were extracted and analysed.

RESULTS

15 studies were included in this meta-analysis, consisting of 2643 patients. InterTan was associated with lower complication rates in terms of all-cause revisions (OR 0.34; 95% CI, 0.22-0.51; p < 0.001), cut-outs (OR 0.30; 95% CI, 0.17-0.51; p < 0.001), medial or lateral screw migration (OR 0.19; 95% CI, 0.06-0.65; p = 0.008) as well as persistent hip and thigh pain (OR 0.65; 95% CI, 0.47-0.90; p = 0.008). In terms of perioperative parameters, InterTan is associated with longer operative times (MD 5.57 minutes; 95% CI, 0.37-10.78 minutes, p = 0.04) and fluoroscopy times (MD 38.89 seconds, 95% CI, 15.88-61.91 seconds; p < 0.001). There was no statistically significant difference in terms of clinical Harris Hip Score and radiological outcomes, non-union, haematoma, femoral fractures, varus collapse, length of stay and mean intraoperative blood loss between the 2 groups.

CONCLUSIONS

Integrated dual lag screw cephalomedullary nails are associated with fewer revisions and complications. However, there is insufficient data to suggest that either nail construct is associated with better functional outcomes.

A finite element analysis and cyclic load experiment on an additional transcortical-type hole formed around the proximal femoral nail system's distal locking screw

BACKGROUND

A complication associated with the distal locking screw used in the proximal femoral nail (PFN) system is the formation of accidental additional holes. We hypothesized that an increase in stress around additional holes is a relevant factor contributing to fractures. This study aimed to evaluate stress changes in the cortical bone around additional screw holes using finite element analysis.

METHODS

Proximal femoral nail antirotation (PFNA)-II (Synthes, Solothurn, Switzerland) was inserted into a femur model. An additional 4.9-mm transcortical hole was made either anteriorly (anterior hole model) or posteriorly (posterior hole model) to the distal locking screw. Finite element analysis was used to calculate compression, tension, and load limits to investigate stress around additional holes with respect to the direction of screw penetration and degree of osteoporosis. The results were then compared with those of mechanical testing. A 31A-21 type intertrochanteric fracture was applied. As a control group, a model without additional holes (no-hole model) was developed. Repeated load-loading tests were performed on 10 model bones per model group.

RESULTS

Tensile stress was significantly greater in the no-hole model when additional screw holes were present, and the anterior hole showed a higher maximum stress value than the posterior hole, suggesting that the anterior hole was more susceptible to fracture. The change in tensile stress first appeared in the hole around the lateral cortical bone and proceeded to the medial side. Biomechanical testing showed that fractures around the distal locking screw occurred in 0 cases of the no-hole, 10 of the anterior hole, and 9 of the posterior hole models.

CONCLUSIONS

During PFN surgery for intertrochanteric fracture, holes with distal locking screws fixed and removed at the anterior and posterior of the nail can be a risk factor for fractures in the surrounding area.

Assessment of the Bone Mineral Density and Microstructure of the Human Femoral Head according to Different Tip-apex Distances Can Guide the Treatment of Intertrochanteric Hip Fractures

Purpose

We analyzed the microstructure and bone mineral density (BMD) of the trabecular bone in the femoral head of patients with osteoporosis.

Materials and Methods

Sixteen femoral heads with osteoporotic femoral neck fractures underwent micro-computed tomography scanning. In each tip-apex distance (TAD) of 15, 20, and 25 mm, five regions of interest (ROIs) were extracted from the central, anterior, posterior, superior, and inferior sections. A total of 15 ROIs were extracted from TADs of 15, 20, and 25 mm. The measurement parameters included BMD, percent bone volume: bone volume/total volume (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), structural model index (SMI), and degree of anisotropy (DOA).

Results

The lowest BMD and BV/TV values were observed in the inferior region and differed significantly from those in other regions (P<0.05). Lower Tb.Th and Tb.N values were observed in the inferior region compared with those in the central region (P<0.05). The highest SMI value was observed in the inferior region (P<0.05). With TAD of 15 and 20 mm, the DOA values in the inferior region were lower than those in the anterior region (P<0.05). Lower BMD and BV/TV values were observed in the anterior, central, and inferior regions of TAD of 15 mm compared with those in the corresponding regions of TAD of 25 mm (P<0.05).

Conclusion

Positioning the lag screw between TAD of 20 to 25 mm and in the inferior region is recommended, and TAD of less than 15 mm is not recommended.

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.

Trochanteric fractures treated by internal fixation using short intramedullary nails: Does the visual intraoperative estimation of the Tip-Apex Distance (TAD) concur with its digital postoperative measurement?

INTRODUCTION

The tip-apex distance (TAD) is the only predictor for mechanical failure after internal fixation of trochanteric fractures. The main objective of our study was to assess whether the intraoperative visual estimation of the TAD concurred with the measurement taken on postoperative digital X-rays. We hypothesized that there was a good concordance between these 2 different methods of measurement.

MATERIALS AND METHODS

Patients with an isolated trochanteric fracture were included in our study. A hardcopy of the intraoperative X-rays were printed, and the TAD was calculated manually. Radiological and clinical follow-ups were scheduled at 6 weeks, 3 months and 6 months during which numerical measurements of the TAD were taken. We also recorded the fracture type (AO/OTA classification), degree of osteoporosis (Singh index), surgeon experience, age and ASA score.

RESULTS

A total of 98 patients were included in our study. Of these, 70 had a 6-month follow-up and interpretable postoperative X-rays. The mean age was 87 years, with 77.14% women and a mean ASA score of 3. The coefficient of concordance between the intra and postoperative TAD was 0.7202 (95% CI=0.4905-0.9499). The secondary displacement rate was 3.28%. The univariate analysis showed no statistically significant association between an intraoperative TAD>25mm and fracture type (p=0.7290), degree of osteoporosis (p=0.5701) and surgeon experience (p=1).

DISCUSSION/CONCLUSIONS

There was a high degree of concordance between intraoperative visual estimation of the TAD and its measurement on postoperative digital X-rays. The treatment of unstable fractures in osteoporotic bone by junior surgeons was not a risk factor for intraoperative TAD>25mm. It is therefore important to educate young surgeons on the concept of TAD and its intraoperative visual estimation technique as it ensures that the cephalic screw is positioned properly during the fixation of trochanteric fractures.

LEVEL OF EVIDENCE

II.

Biomechanical analysis of the treatment of intertrochanteric hip fracture with different lengths of dynamic hip screw side plates

BACKGROUND

Dynamic hip screw (DHS) is a common implant used to treat stable-type intertrochanteric hip fractures. There are many factors that can affect the success rate of the surgery, including the length of side plates. It is therefore important to investigate the biomechanical effect of different DHS side plates on bones.

OBJECTIVE

In order to reduce the likelihood of an implant failure, the aim of this study was to use finite element analysis (FEA) to investigate and understand the effect of side plates with different lengths in DHS.

METHODS

In this FEA study, a 3D model with cortical bone, cancellous bone, side plate, lag screw, and cortical screws to simulate the implantation of DHS with different lengths of side plate (2-hole, 4-hole, and 6-hole) for intertrochanteric hip fractures was constructed. The loading condition was used to simulate the force (400 N) on the femoral head and the stress distribution on the lag screw, side plate, cortical screws, and femur was measured.

RESULTS

The highest stress points occured around the region of contact between the screw and the cortical bones. The stress on the femur at the most distal cortical screw was the greatest. The shorter the length of the side plate, the greater the stress on the cortical screws, resulting in an increased stress on the femur surrounding the cortical screws.

CONCLUSIONS

The use of DHS with 2-hole side plate may increase the risk of side plate pull-out. The results of this study provide a biomechanical analysis for selection of DHS implant lengths that can be useful for orthopaedic surgeons.

[Reasons of the guide pin eccentricity of helical blade during proximal femoral nail anti-rotation internal fixation for femoral intertrochanteric fractures]

Objective

To analyze the reasons and the influence of internal fixation about the guide pin eccentricity of helical blade during proximal femoral nail anti-rotation (PFNA) internal fixation for femoral intertrochanteric fractures.

Methods

A retrospective analysis of the intraoperative imaging data of 175 patients with femoral intertrochanteric fractures, who underwent closed reduction and PFNA internal fixation between January 2018 and January 2020, was performed. There were 76 males and 99 females with an average age of 79.8 years (mean, 61-103 years). The internal between admission and operation was 12-141 hours (median, 32 hours). According to AO/Orthopaedic Trauma Association (AO/OTA) classification, the fractures were rated as type 31-A1 in 64 cases and type 31-A2 in 111 cases. In the intraoperative fluoroscopy image by C-arm X-ray machine, the caputcollum-diaphysis (CCD) was measured after closed reduction and internal fixation, respectively; the angles between the center line of the head nail hole and the axis of proximal nail and between the axis of guide pin and proximal nail were measured, and the difference between the two angles was evaluated; the quality of fracture reduction was evaluated according to the alignment of the medial cortex, anterior cortex of the head and neck bone block, and femoral shaft cortex; the position of the helical blade in the femoral head was evaluated according to the Cleveland method.

Results

The CCDs of proximal femur were (134.6±6.8)° after closed reduction and (134.9±4.3)° after internal fixation. There was no significant difference between pre- and post-internal fixation ( t=0.432, P=0.766). The angles between the center line of the head nail hole and the axis of proximal nail and between the axis of guide pin and proximal nail were (125.4±2.44)° and (126.3±2.3)°, respectively, showing significant difference ( t=2.809, P=0.044). The difference between the two angles was (0.8±2.2)°. The guide pin eccentricity of helical blade occurred in 47 cases. After tapping the helical blade along the eccentric guide pin, 10 cases had fracture reduction loss, and 5 cases had a poor position of the helical blade in the femoral head.

Conclusion

During PFNA internal fixation, a variety of reasons can lead to the eccentric position of the guide pin of helical blade, including unstable fracture, soft tissue inserted, severe osteoporosis, mismatched tool, and fluoroscopic imaging factors. It is possible that the fracture end would be displaced again and the helical blade position may be poor when knocking into the helical blade along the eccentric guide pin. During operation, it should be judged whether the direction of the guide pin needs to be adjusted according to the eccentric angle.

Biomechanical comparison of medial sustainable nail and proximal femoral nail antirotation in the treatment of an unstable intertrochanteric fracture

AIMS

Restoration of proximal medial femoral support is the keystone in the treatment of intertrochanteric fractures. None of the available implants are effective in constructing the medial femoral support. Medial sustainable nail (MSN-II) is a novel cephalomedullary nail designed for this. In this study, biomechanical difference between MSN-II and proximal femoral nail anti-rotation (PFNA-II) was compared to determine whether or not MSN-II can effectively reconstruct the medial femoral support.

METHODS

A total of 36 synthetic femur models with simulated intertrochanteric fractures without medial support (AO/OTA 31-A2.3) were assigned to two groups with 18 specimens each for stabilization with MSN-II or PFNA-II. Each group was further divided into three subgroups of six specimens according to different experimental conditions respectively as follows: axial loading test; static torsional test; and cyclic loading test.

RESULTS

The mean axial stiffness, vertical displacement, and maximum failure load of MSN-II were 258.47 N/mm (SD 42.27), 2.99 mm (SD 0.56), and 4,886 N (SD 525.31), respectively, while those of PFNA-II were 170.28 N/mm (SD 64.63), 4.86 mm (SD 1.66), and 3,870.87 N (SD 552.21), respectively. The mean torsional stiffness and failure torque of MSN-II were 1.72 N m/° (SD 0.61) and 16.54 N m (SD 7.06), respectively, while those of PFNA-II were 0.61 N m/° (SD 0.39) and 6.6 N m (SD 6.65), respectively. The displacement of MSN-II in each cycle point was less than that of PFNA-II in cyclic loading test. Significantly higher stiffness and less displacement were detected in the MSN-II group (p < 0.05).

CONCLUSION

The biomechanical performance of MSN-II was better than that of PFNA-II, suggesting that MSN-II may provide more effective mechanical support in the treatment of unstable intertrochanteric fractures. Cite this article: Bone Joint Res 2020;9(12):840-847.

Comparing the usefulness of a fluoroscopic navigation system in femoral trochanteric fracture for orthopaedic residents with the conventional method

INTRODUCTION

Lag screw insertion into the ideal position is essential to obtain good results in open reduction and internal fixation for femoral trochanteric fracture. Tip-apex distance (TAD) is a widely adopted method for evaluating the risk of lag screw cut-out. Adaptive positioning technology (ADAPT) is a fluoroscopic computer-assisted surgery system that enables orthopaedic surgeons to guide the screw into a proper position intraoperatively. A randomized control study concluded that ADAPT resulted in excellent TAD. However, it was not significantly better than conventional methods when performed by fellowship-trained traumatologists. Therefore, we hypothesised that ADAPT would be useful to orthopaedic residents and evaluated this usefulness.

METHODS

We reviewed 102 patients who underwent open reduction and internal fixation for femoral trochanteric fracture from May 2017 to March 2019 using Gamma-3 intertrochanteric nails. Two residents performed all procedures; 51 patients underwent surgery using ADAPT and the others underwent surgery without navigation. The number of attempts to drill guide-wire, operation time, lag screw insertion time, radiation exposure time, TAD, and lag screw position were evaluated for each surgeon.

RESULTS

In one resident, when using the ADAPT system, the number of attempts to drill guide-wire (p=0.001), lag screw insertion time (p=0.000), radiational exposure time (p=0.009) and TAD (p=0.007) were lower, and the percentage of ideal lag screw position (p=0.035) were better than that in the conventional method. However, there was no significant difference in the performance of another resident with respect to the aforementioned factors, whether using ADAPT or not.

CONCLUSION

One resident showed better results with the ADAPT system than with conventional osteosynthesis. However, another resident received no benefit from ADAPT. The efficiency may not apply to everyone as individual competence can influence efficiency when using ADAPT system. Therefore, as a new device, it must be used cautiously because skill or experience may influence its use, especially by orthopaedic residents.

Finite element analysis of two cephalomedullary nails in treatment of elderly reverse obliquity intertrochanteric fractures: zimmer natural nail and proximal femoral nail antirotation-ΙΙ

Background

More elderly patients are suffering from intertrochanteric fractures. However, the choice of internal fixation is still controversial, especially in the treatment of unstable intertrochanteric fracture; thus, previous implants continue to be improved, and new ones are being developed. The purpose of our study was to compare the biomechanical advantages between the zimmer natural nail (ZNN) and proximal femoral nail antirotation-II (PFNA-II) in the treatment of elderly reverse obliquity intertrochanteric fractures.

Methods

A three-dimensional finite element was applied for reverse obliquity intertrochanteric fracture models (AO31-A3.1) fixed with the ZNN or PFNA-II. The distribution, peak value and position of the von Mises stress and the displacement were the criteria for comparison between the two groups.

Results

The stresses of the internal fixation and femur in the ZNN model were smaller than those in the PFNA-II model, and the peak values of the two groups were 364.8 MPa and 171.8 MPa (ZNN) and 832.3 MPa and 1795.0 MPa (PFNA-II). The maximum amount of displacement of the two groups was similar, and their locations were the same, i.e., in the femoral head vertex (3.768 mm in the ZNN model and 3.713 mm in the PFNA-II model).

Conclusions

The displacement in the two models was similar, but the stresses in the implant and bone were reduced with the ZNN. Therefore, the ZNN implant may provide biomechanical advantages over PFNA-II in reverse obliquity intertrochanteric fractures, as shown through the finite element analysis. These findings from our study may provide a reference for the perioperative selection of internal fixations.