Antirotation Blade Research Articles

Technical Note in Case Series a Novel Recent Technique for the Removal of Broken PFNA-II Blade in Intertrochanteric Fractures is a Technical Challenge.

Proximal femoral nail antirotation - II (PFNA- II) is a common treatment for intertrochanteric fractures in the elderly. Removing PFNA is difficult in rare circumstances due to blade head stripping or breaking. In this article, we endeavored to explain an easy methodology that can be utilized to remove stripped, damaged anti-rotation blades for which few had been formulated but other procedures have failed. In four cases, one case is discussed 15 months following the prior fixation; the individual underwent PFNA removal surgery for a broken implant causing pain. We had trouble removing the anti-rotation blade with the standard equipment. The procedure assisted us in removing the anti-rotation blade and provided a favorable outcome for the patient. The insertion of a DHS guide wire with a coupling screw for inserting DHS screw in conjunction with a proximal femoral anti-rotation blade may be a cost-effective and simple approach to dealing with extraction failure.

Changes in nail position and antirotation blade angles on the risk of femoral head varus in PFNA fixed patients: a clinical review and comprehensive biomechanical research

BackgroundFemoral head varus triggers poor clinical prognosis in intertrochanteric fracture patients with proximal femoral nail antirotation (PFNA) fixation. Studies present that changes in nail position and screw insertion angles will affect fixation stability, but the biomechanical significance of these factors on the risk of femoral head varus has yet to be identified in PFNA fixed patients.MethodsClinical data in PFNA fixed intertrochanteric fracture patients have been reviewed, the relative position of intermedullary nail has been judged in the instant postoperative lateral radiography. Regression analyses have been performed to identify the effect of this factor on femoral head varus. Corresponding biomechanical mechanism has been identified by numerical mechanical simulations.ResultsA clinical review revealed that ventral side nail insertion can trigger higher risk of femoral head varus, corresponding numerical mechanical simulations also recorded poor fixation stability in models with ventral side nail insertion, and changes in the trajectory of anti-rotation blade will not obviously affect this tendency.ConclusionsVentral side insertion of intramedullary nail can trigger higher risk of femoral head varus in PFNA fixed patients by deteriorating the instant postoperative biomechanical environment, and changes in blade trajectory cannot change this tendency biomechanically. Therefore, this nail position should be adjusted to optimize patients’ prognosis.

Impact of blade direction on postoperative femoral head varus in PFNA fixed patients: a clinical review and biomechanical research.

Intertrochanteric femur fracture is a common type of osteoporotic fracture in elderly patients, and postoperative femoral head varus following proximal femoral nail anti-rotation (PFNA) fixation is a crucial factor contributing to the deterioration of clinical outcomes. The cross-angle between the implant and bone might influence fixation stability. Although there is a wide range of adjustment in the direction of anti-rotation blades within the femoral neck, the impact of this direct variation on the risk of femoral head varus and its biomechanical mechanisms remain unexplored. In this study, we conducted a retrospective analysis of clinical data from 69 patients with PFNA fixation in our institution. We judge the direction of blade on the femoral neck in on the immediate postoperative lateral X-rays or intraoperative C-arm fluoroscopy, investigating its influence on the early postoperative risk of femoral head varus. p < 0.05 indicates significant results in both correlation and regression analyses. Simultaneously, a three-dimensional finite element model was constructed based on the Syn-Bone standard proximal femur outline, exploring the biomechanical mechanisms of the femoral neck-anti-rotation blade direction variation on the risk of this complication. The results indicated that ventral direction insertion of the anti-rotation blade is an independent risk factor for increased femoral head varus. Complementary biomechanical studies further confirmed that ventral angulation leads to loss of fixation stability and a decrease in fixation failure strength. Therefore, based on this study, it is recommended to avoid ventral directional insertion of the anti-rotation blade in PFNA operation or to adjust it in order to reduce the risk of femoral head varus biomechanically, especially in unstable fractures. This adjustment will help enhance clinical outcomes for patients.

Damage-Based Assessment of the Risk of Cut-Out in Trochanteric Fractures for Different Proximal Femoral Nail Anti-Rotation (PFNA) Blade Positions

Cut-out of the hip blade of fracture fixation implants, defined as the perforation of the femoral head by the blade due to the collapse of the neck-shaft angle into varus, is the most relevant mechanical complication in the treatment of trochanteric fractures. Among the factors that contribute to cut-out, the blade positioning in the femoral head is reported as one of the most relevant. Since the optimal blade position in the superior–inferior and medial–lateral directions is unknown, the goal of this work was to investigate the impact of blade positioning in these directions, using three-dimensional finite element models of two femora with an unstable trochanteric fracture (31-A2.2 in the Müller AO classification system with an intrusion distance of 95% of the fracture line length). The finite element models developed were coupled with a stiffness-adaptive damage model for the evaluation of the risk of cut-out. The Proximal Femoral Nail Anti-rotation (PFNA) blade was placed in each model at four discrete distances from the femoral head surface in central and inferior positions. The damage distribution in bone resulting from a gait loading condition was visually and quantitatively assessed to compare the performance of the eight positions and predict the relative risk of cut-out for each. The results suggest that the closer the tip of the blade to the femoral head surface, the lower the risk of cut-out. In the superior–inferior direction, contradicting findings were obtained for the modelled femora. The depth of placement of the blade in the medial–lateral direction and its superior–inferior position were shown to have great influence in the risk of cut-out, with the medial–lateral position being the most relevant predictor. The optimal blade positioning may be subject-specific, depending on bone geometry and density distribution.

Is Sliding Compression Necessary for Intramedullary Nailing Fixation of AO/OTA Type A3.3 Intertrochanteric Fracture?

The intramedullary nail is considered the gold standard for treating AO/OTA type A3.3 intertrochanteric fractures. However, it still faces a significant rate of failure, mainly due to the critical factor of comminuted lateral wall defects leading to inadequate proximal sliding compression. The primary objective of this study is to investigate the requirement of sliding compression in the treatment of unstable AO/OTA type A3.3 intertrochanteric fractures. To achieve this, we conduct a comparative analysis between two approaches: InterTAN alone and proximal femoral anti-rotation blade nailing (PFNA) combined with lateral wall reconstruction for treating AO/OTA type A3.3 intertrochanteric fractures with lateral wall damage. A retrospective analysis was conducted on the clinical data of patients who underwent intramedullary nailing fixation for AO/OTA type A3.3 intertrochanteric fractures at our hospital from January 2012 to January 2022. Patient characteristics as well as treatment details, including operative time, intraoperative blood loss, weight-bearing time, fracture healing time, tip apex distance (TAD) loss, Harris hip scores (HHS), Parker-Palmer mobility score (PPMS), and postoperative complications, were collected and analyzed. Continuous variables were analyzed using independent sample t-tests, while categorical variables were examined using the chi-square test. For group comparisons, variance analysis was applied, and pairwise comparisons were conducted using the LSD-t test. These patients were divided into PFNA combined with lateral wall reconstruction group (sliding compression group) and InterTAN fixation group (static fixation group) based on surgical methods. The operation time, intraoperative bleeding loss, HHS at 12 months and PPMS at 12 months in the sliding compression group were significantly higher than those in the static fixation group, and time to weight-bearing and fracture healing time were significantly lower than those in the static fixation group (p < 0.05). There were no significant differences between two groups in terms of the TAD at 2 days, 2, and 12 months postoperatively, the incidence of complications (p > 0.05). At 6 months postoperatively, femoral neck length was shortened compared to 2 days postoperatively in both groups, and the sliding compression group had a significantly greater degree of femoral neck shortening than the static fixation group (p < 0.05). The use of PFNA with lateral wall reconstruction for A3.3 intertrochanteric fractures demonstrated superior mobility, efficiency, and reduced internal fixation failure rates compared to InterTAN. These findings suggest that sliding compression may be required for intramedullary nailing treatment.

Biomechanical effects of internal fixation with self-lock compression anti-rotation blade for Pauwels type III femoral neck fractures: a comparative finite element analysis

BackgroundSelf-lock compression anti-rotation blade (SCAB) is a novel internal fixation implant for femoral neck fractures (FNF). We conducted this finite element analysis study to evaluate the biomechanical performances of SCAB combined with a cannulated screw for fixation of Pauwels type III FNF.MethodsThree finite element models of Pauwels type III FNF treated with various internal fixations were established: a: the inverted triangular parallel cannulated screw (3CS) model, b: the biplane double-supported screw fixation (BDSF) model, c: the SCAB combined with a cannulated screw model. Displacement and Von Mises stress of femurs and internal fixations under increasing loads as well as the average stress on fracture surfaces and maximum displacements on the X and Z axis of proximal fracture fragments at maximum load were measured and compared.ResultThe SCAB-based internal fixation exhibited superior biomechanical performances compared with 3CS and BDSF configurations, as the former resulted in lower parameters including displacement of the femur, Von Mises stress of internal fixation, stress on fracture surfaces as well as X and Z axis displacement of fracture fragments.ConclusionInternal fixation using SCAB combined with a cannulated screw for Pauwels type III FNFs shows enough stability, with satisfied resistance to varus and shearing forces, which may provide a new option for the treatment of FNFs.

Impact of Bone Cement Augmentation on the Fixation Strength of TFNA Blades and Screws.

Background and Objectives: Hip fractures constitute the most debilitating complication of osteoporosis with steadily increasing incidences in the aging population. Their intramedullary nailing can be challenging because of poor anchorage in the osteoporotic femoral head. Cement augmentation of Proximal Femoral Nail Antirotation (PFNA) blades demonstrated promising results by enhancing cut-out resistance in proximal femoral fractures. The aim of this study was to assess the impact of augmentation on the fixation strength of TFN-ADVANCEDTM Proximal Femoral Nailing System (TFNA) blades and screws within the femoral head and compare its effect when they are implanted in centre or anteroposterior off-centre position. Materials and Methods: Eight groups were formed out of 96 polyurethane low-density foam specimens simulating isolated femoral heads with poor bone quality. The specimens in each group were implanted with either non-augmented or cement-augmented TFNA blades or screws in centre or anteroposterior off-centre positions, 7 mm anterior or posterior. Mechanical testing was performed under progressively increasing cyclic loading until failure, in setup simulating an unstable pertrochanteric fracture with a lack of posteromedial support and load sharing at the fracture gap. Varus-valgus and head rotation angles were monitored. A varus collapse of 5° or 10° head rotation was defined as a clinically relevant failure. Results: Failure load (N) for specimens with augmented TFNA head elements (screw/blade centre: 3799 ± 326/3228 ± 478; screw/blade off-centre: 2680 ± 182/2591 ± 244) was significantly higher compared with respective non-augmented specimens (screw/blade centre: 1593 ± 120/1489 ± 41; screw/blade off-centre: 515 ± 73/1018 ± 48), p < 0.001. For both non-augmented and augmented specimens failure load in the centre position was significantly higher compared with the respective off-centre positions, regardless of the head element type, p < 0.001. Augmented off-centre TFNA head elements had significantly higher failure load compared with non-augmented centrally placed implants, p < 0.001. Conclusions: Cement augmentation clearly enhances the fixation stability of TFNA blades and screws. Non-augmented blades outperformed screws in the anteroposterior off-centre position. Positioning of TFNA blades in the femoral head is more forgiving than TFNA screws in terms of failure load.

The effect on outcomes of the application of circumferential cerclage cable following intramedullary nailing in reverse intertrochanteric femoral fractures.

The aim of this study was to evaluate the effect on union results of the application of cerclage cable around the lateral femoral wall (LFW) in postoperative fracture displacement. A retrospective evaluation was made of all the cases of reverse intertrochanteric fractures over a 7-year period in a trauma center. The study included 69 fractures treated with intramedullary nailing. The age of the patients, postoperative reduction quality and complications such as mechanical failure and non-union (1.4%) were obtained from the medical records. Changes in the neck-shaft angle, the amount of LFW displacement and telescoping of proximal femoral nail antirotation blades and lag screws were measured on anteroposterior and lateral radiographs. The functional evaluation of the Harris Hip Score was recorded at the final follow-up examination. The mean age of the patients was 56.31years (range 18-93years). Closed reduction was applied in 37 (53.7%) cases, open reduction in 10 (14.5%) and with cerclage cable in 22 (31.8%). Mechanical failure developed in 8 (11.5%) cases where cerclage cable was not used. In 2 of these 8 cases, open reduction was successful. In the patients where cerclage cable was applied, no mechanical failure developed and no case underwent revision surgery. In the cases where cerclage cable was not used, a significantly higher rate of telescoping was found. (p = 0.001). The application of cerclage cable was seen to significantly reduce the amount of LFW displacement (2.23mm vs 8.86mm) and shorten the time to partial weight bearing (p = 0.000). In reverse intertrochanteric fractures, the application of circumferential cerclage cable with cephalomedullary nailing contributes to primary stability and accelerates mobilization. Therefore, it can be considered a good option. It reduces the risk of failure internal fixation for intertrochanteric fracture.

Assessment of Intraosseous Femoral Head Pressures During Cement Augmentation of the Perforated Proximal Femur Nail Antirotation Blade

The benefits of cement augmentation with fixation of osteoporotic pertrochanteric fractures have been previously demonstrated. The objective of this study was 3-fold: (1) To quantify the intraosseous pressure produced during cement augmentation of the perforated proximal femoral nail antirotation (PFNA) blades; (2) To assess whether the pressure generated is influenced by the injection rate; and (3) To assess the amount of force applied during the injection. Six pairs of human cadaveric femurs were used in the study. A basicervical osteotomy was performed, and the heads were instrumented with the PFNA blade. Each pair was randomly assigned into 1 of 2 groups: slow versus rapid injection with polymethylmethacrylate (PMMA) cement. In the slow group, the augmentation was performed using 6 consecutive 1 mL injections, each over 10 seconds. In the rapid group, each 1 mL injection was performed over 5 seconds. For intraosseous pressure measurements, transmitters were inserted to a depth of 5 mm at both the superior and inferior apices of the head. The reaction forces on the syringe were measured as well. There were no significant differences between the slow and rapid injection rates with respect to the peak pressures measured at the 6 time points immediately after cement injection. In both groups, elevations in pressure were transient and returned to baseline values within 30 seconds. The highest pressure recorded in the slow group was 37.3 and 30.7 mm Hg in the rapid group. The force required after each sequential injection increased in both groups; however, significantly higher forces were required to inject cement over 5 than 10 seconds (P = 0.036). This in vitro model is the first one to demonstrate that femoral head cement augmentation is associated with a small transient increase in intraosseous pressure with sequential fast and slow 1 mL injections of up to 6 mL PMMA. We conclude that cement augmentation of the perforated PFNA blade carries a low risk of pressure-induced avascular necrosis.

Cement augmentation of hip implants in osteoporotic bone: How much cement is needed and where should it go?

Several studies proved the beneficial effect of cement augmentation of proximal femoral nail antirotation (PFNA) blades on implant purchase in osteoporotic bone. We investigated the effect of different localizations and amounts of bone cement. Polyurethane foam specimens were instrumented with a PFNA blade and subsequently augmented with PMMA bone cement. Eight study groups were formed based on localization and amount of cement volume related to the blade. All specimens underwent cyclic loading with physiological orientation of the force vector until construct failure. Foam groups were compared between each other and to a cadaveric control group. The experiments revealed a significant dependency of implant purchase on localization and amount of cement. Biomechanically favorable cement positions were found at the implant tip and at the cranial side. However, none of the tested augmentation patterns performed significantly inferior to the cadaveric benchmark. These findings will allow surgeons to further reduce the amount of injected PMMA, decreasing the risk of cement leakage or cartilage damage.

Ex vivo evaluation of the polymerization temperatures during cement augmentation of proximal femoral nail antirotation blades

Previous studies have clearly demonstrated superior biomechanical behavior of augmented proximal femoral nail antirotation (PFNA) blades compared with nonaugmented ones with respect to implant cutout. Nevertheless, there is concern about thermal bone necrosis due to exothermic curing of polymethylmethacrylate (PMMA)-based bone cements. The objective of this study was to quantify the temperatures arising around perforated titanium PFNA blades when augmenting with PMMA. Cylindrical samples from six pairs of fresh frozen human cadaveric femoral heads implanted with a PFNA blade were placed in a 37°C water bath and augmented with 3 mL and 6 mL PMMA. During augmentation, temperatures were measured using six K-type thermocouples that were placed at controlled distances around the implant. With the help of high-resolution quantitative computed tomography images, the locations of all thermocouples with respect to the cement-bone interface were reconstructed. No temperatures higher than 45°C were measured in the interface region and the surrounding cement-free cancellous bone. In the same regions, the longest exposure time above 41°C was 8.5 minutes and was measured in a 6-mL sample. Average maximum temperature was significantly lower for the 3-mL group compared with the 6-mL group (p = 0.017). The results of this study suggest that augmentation of titanium PFNA blades is not associated with a risk of thermal bone necrosis when using up to 6 mL of PMMA. However, larger amounts of cement lead to higher temperatures. PMMA application should therefore be kept low to minimally alter the biological system.

Potential of polymethylmethacrylate cement-augmented helical proximal femoral nail antirotation blades to improve implant stability—A biomechanical investigation in human cadaveric femoral heads

Cement augmentation may improve fixation stability and reduce cut-out rate in the treatment of intertrochanteric hip fractures. The aim of this study was to compare the number of cycles to failure of polymethylmethacrylate (PMMA)-augmented helical blades with nonaugmented ones in human cadaveric femoral heads. Six pairs of cadaveric femoral heads were instrumented with a perforated proximal femoral nail antirotation blade. Within each pair, one blade was augmented using 3 mL of PMMA. All specimens underwent cyclic axial loading under physiologic conditions.Starting at 1,000 N, the load was monotonically increased by 0.1 N/cycle until construct failure occurred. To monitor the migration of the blade, anteroposterior radiographs were taken at 250 cycle increments. Nonparametric test statistics were done to calculate correlations and identify differences between study groups. Inducing failure required a significantly higher number of cycles in the augmented group (p = 0.028). Bone mineral density was significantly related with the number of cycles to failure in nonaugmented specimens (p 0.001, R2 = 0.97), but not in the augmented group (p = 0.91, R2 = 0.34). Implant augmentation with small amounts of PMMA enhances the cut-out resistance in proximal femoral fractures. Especially in osteoporotic bone, the procedure may improve patient care.

Biomechanical evaluation of bone-cement augmented Proximal Femoral Nail Antirotation blades in a polyurethane foam model with low density

BackgroundHelically shaped cephalic implants have proven their benefit to provide an improved stabilization of unstable hip fractures. However, cut out ratios up to 3.6% still occur. This in vitro study evaluated the biomechanical performance of a novel cement augmentation technique of the Proximal Femoral Nail Antirotation in surrogate femora. MethodsFour study groups were formed out of 24 polyurethane foam specimens with low density. Proximal Femoral Nail Antirotation blades were implanted, either non-augmented, or augmented using 3ml of injectable Polymethylmethacrylate bone-cement. The influence of implant mal-positioning was investigated by placing the blade either centered in the femoral head or off-centric in an anteroposterior direction. All specimens underwent cyclic loading under physiological conditions. Starting at 1000N, the load was monotonically increased by 0.1N/cycle until construct failure. Movement of the head was identified by means of optical motion tracking. Non-parametric test statistics were carried out on the cycles to failure, to compare between study groups. FindingsCompared to control samples; augmented samples showed a significantly increased number of cycles to failure (P=0.012). In the groups with centric position of the Proximal Femoral Nail Antirotation blade, cement augmentation led to an increase in loading cycles of 225%. In the groups with off-centric positioning of the blade, this difference was even more accentuated (933%). InterpretationCement augmentation of the Proximal Femoral Nail Antirotation blade with small amounts of bone-cement for treatment of osteoporotic hip fractures clearly enhances fixation stability and carries high potential for clinical application.

Comparison of proximal femoral nail antirotation blade and reverse less invasive stabilization system‐distal femur systems in the treatment of proximal femoral fractures

To compare the effects of proximal femoral nail antirotation blade (PFNA) and reverse less invasive stabilization system-distal femur (Liss-DF) systems in the treatment of proximal femoral fractures. Between June 2007 and October 2009, 41 proximal femoral fractures were treated, 22 with PFNA (group A) and 19 with reverse LISS-DF plates (group B). The time to starting full weight-bearing, fracture healing time, functional recovery (Parker and Palmer mobility score), neck-shaft angle discrepancies with the intact contralateral hip, preoperative American Society of Anesthesiologists (ASA) scores, the operation durations and amount of intraoperative bleeding were recorded and compared. The mean follow-up period was 11.2 months (range, 10-12 months). Compared with Group A, Group B showed a statistically longer mean time to bear full body weight and heal their fractures, but a smaller neck-shaft angle discrepancy (all P < 0.05). The groups were similar in ASA score, operation duration, amount of intraoperative bleeding and Parker and Palmer mobility score. Both PFNA and reverse Liss-DF were satisfactory for the treatment of proximal femoral fractures, but had different advantages. PFNA allowed earlier weight-bearing and accelerated fracture healing. Reverse Liss-DF more effectively avoided coxa vara and may be indicated for patients with very severe osteoporosis.

Development of self-locking cannulated compression anti-rotation blade for treatment of femoral neck fractures

Objective To develop self-locking cannulated compression anti-rotation blade and investigate its design characteristic and manipulation techniques. Methods Femoral neck fracture model was made by osteotomy on seven cadaver femurs and then fixed by self-locking cannulated compres-sion anti-rotation blade under fluoroscopic guidance according to designed procedures. After fixation, bio-mechanic test was performed to evaluate fixation stability. Results Cannulated self-locking compres-sion anti-rotation blade was tightly impacted in proximal femur and compression detected during the process of locking, with successful manipulation and stable fixation. Conclusion Because of advanced design characteristic and simple manipulation, self-locking cannulated compression anti-rotation blade can be a substitute for cannulated cancellous lag screw in treatment of femoral neck fractures. Key words: Femoral neck fractures: Fracture fixation, internal; Biomechanies