Fixation Of Periprosthetic Femoral Fractures Research Articles

Is suture-based cerclage biomechanically superior to traditional metallic cerclage for fixation of periprosthetic femoral fractures: A matched pair cadaveric study

BackgroundWhile traditional metallic cerclage remains the primary method in clinical application, non-metallic cerclage systems have recently gained popularity due to low risks of soft tissue irritation and bone intrusion. The objective of this study was to assess the performance of a novel non-metallic suture-based cerclage in comparison to traditional metallic cerclage cables for fixation of periprosthetic femoral fractures. MethodsAn extended trochanteric osteotomy was performed on eight pairs of cadaveric femora, followed by reduction using either metallic cerclages (Group I) or the suture-based cerclage (Group II). A modular tapered fluted stem was then implanted in each specimen. The fragment translation during canal preparation and stem implantation was quantified using laser-scanning. Subsequently, each specimen underwent 500 cycles of multiaxial loading, with fragment translation and stem subsidence measured using a motion capture system. FindingsFollowing stem implantation, specimens in Group II exhibited a significantly greater lateral fragment translation (466 μm vs 754 μm, p = 0.017). However, there were no significant differences in anterior and distal translation between groups (p > 0.05). During multiaxial loading, the average stem subsidence in Group I was 0.36 mm (range, 0.04–1.42 mm), compared to 0.41 mm (range, 0.03–1.29) in Group II (p > 0.05). No significant difference was found in fragment translations between the two groups (p > 0.05). InterpretationThe suture-based cerclage system exhibited comparable biomechanical performance in fixation stability to conventional metallic cerclage cables. Yet, it was associated with a larger residual lateral gap between the fragments following stem implantation. Ultimately, the choice of fixation method should account for multiple factors, including patient characteristics, surgeon preference, and bone quality.

Unstable Vancouver B1 periprosthetic femoral fracture fixation: A biomechanical comparison between a novel C-shaped memory alloy implant and cerclage wiring.

To compare the biomechanical stability of a novel, C-shaped nickel-titanium shape memory alloy (SMA) implant (C-clip) with traditional cerclage wiring in the fixation of a Vancouver B1 (VB1) periprosthetic femoral fracture (PFF). In total, 18 synthetic femoral fracture models were constructed to obtain unstable VB1 fracture with an oblique fracture line 8 cm below the lesser trochanter. For each model, the distal portion was repaired using a 10-hole locking plate and four distal bi-cortical screws. The proximal portion was repaired using either three, threaded cerclage wirings or three, novel C-shaped implants. Specimens underwent biomechanical testing using axial compression, torsional and four-point bending tests. Each test was performed on three specimens. The C-clip was statistically significantly stronger (i.e., stiffer) than cerclage wiring in the three biomechanical tests. For axial compression, medians (ranges) were 39 (39-41) and 35 (35-35) N/mm, for the C-clip and cerclage wiring, respectively. For torsion, medians (ranges) were, 0.44 (0.44-0.45) and 0.30 (0.30-0.33) N/mm for the C-clip and cerclage wiring, respectively. For the four-point bending test, medians (ranges) were 39 (39-41) and 28 (28-31) N/mm; for the C-clip and cerclage wiring, respectively. Results from this small study show that the novel, C-shaped SMA appears to be biomechanically superior to traditional cerclage wiring in terms of stiffness, axial compression, torsion and four-point bending, and may be a valuable alternative in the repair of VB1 PFF. Further research is necessary to support these results.

Impact of periprosthetic femoral fracture fixation plating constructs on local stiffness, load transfer, and bone strains

Secondary femoral fractures after the successful plate-screw fixation of a primary Vancouver type B1 periprosthetic femoral fracture (PFF) have been associated with the altered state of stress/strain in the femur as the result of plating. The laterally implanted condyle-spanning plate-screw constructs have shown promises clinically in avoiding secondary bone and implant failures as compared with shorter diaphyseal plates. Though the condyle-spanning plating has been hypothesized to avoid stress concentration in the femoral diaphysis through increasing the working length of the plate, biomechanical evidence is lacking on how plate length may impact the stress/strain state of the implanted femur. Through developing and experimentally validating finite element (FE) models of 3 cadaveric femurs, this study investigated the impact of plating on bone strains, load transfer and local stiffness, which were compared between FE models of 2 different plating systems that each had a diaphyseal configuration and a condyle-spanning configuration. Under simulated gait-loading, the condyle-spanning constructs of both plating systems were shown to lower the bone strains around the distal fixation screws (up to 24.8% reduction in maximum principal strain and 26.6% reduction in minimum principal strain) and in the distal metaphyseal shaft of the femur (up to 15.9% and 25.7% reductions in maximum and minimum principal strains, respectively), where secondary bone fractures have been typically reported. In the distal diaphyseal and metaphyseal shaft of femur, FE models of the condyle-spanning constructs were shown to increase the local compressive stiffness (up to 152.9% increases under simulated gait-loading) and decrease the transfer of compressive load (37.1% decreases under simulated gait-loading), which may be indicative of the lowered risks of bone damage.

Simplified Mechanical Tests Can Simulate Physiological Mechanics of a Fixation Construct for Periprosthetic Femoral Fractures.

Plate fractures after fixation of a Vancouver Type B1 periprosthetic femoral fracture (PFF) are difficult to treat and could lead to severe disability. However, due to the lack of direct measurement of in vivo performance of the PFF fixation construct, it is unknown whether current standard mechanical tests or previous experimental and computational studies have appropriately reproduced the in vivo mechanics of the plate. To provide a basis for the evaluation and development of appropriate mechanical tests for assessment of plate fracture risk, this study applied loads of common activities of daily living (ADLs) to implanted femur finite element (FE) models with PFF fixation constructs with an existing or a healed PFF. Based on FE simulated plate mechanics, the standard four-point-bend test adequately matched the stress state and the resultant bending moment in the plate as compared with femur models with an existing PFF. In addition, the newly developed constrained three-point-bend tests were able to reproduce plate stresses in models with a healed PFF. Furthermore, a combined bending and compression cadaveric test was appropriate for risk assessment including both plate fracture and screw loosening after the complete healing of PFF. The result of this study provides the means for combined experimental and computational preclinical evaluation of PFF fixation constructs.

Analysis of carbon fibre bone plate for “B1” type periprosthetic femoral fracture

Peri-prosthetic Fractures after Total Hip Arthroplasty (THA) are a dreaded complication which happen frequently due to aging and day to day normal activities of the patient. These fractures happen below the cemented/uncemented stem, either straight/oblique direction concerning the transverse plane. Treatment requires surgical stabilization using metal plates, screws, cables and/or clamps. However, stress shielding in bone due to metal plates can be reduced by designing implants with fibre reinforced polymer composites. The present study aims to study the stress distribution in a composite plate using carbon fibre for a B1 type periprosthetic femoral fracture fixation in immediate postoperative (IPO) condition and compared with metal plate by varying geometrical parameters, laminate stacking sequence and fibre orientation. To evaluate the axial stiffness and surface stress of composite plate fixation finite element (FE) analysis was done. Various parameters like axial movement, shear movement, strain and maximum stress are considered to measure the fracture stability and the healing process through FE method. The results showed that the proposed composite bone plate could be a potential candidate for replacement of metallic bone plates for periprosthetic fracture in the femur.

Application of Far Cortical Locking Technology in Periprosthetic Femoral Fracture Fixation: A Biomechanical Study

BackgroundLack of fracture movement could be a potential cause of periprosthetic femoral fracture (PFF) fixation failures. This study aimed to test whether the use of distal far cortical locking screws reduces the overall stiffness of PFF fixations and allows an increase in fracture movement compared to standard locking screws while retaining the overall strength of the PFF fixations. MethodsTwelve laboratory models of Vancouver type B1 PFFs were developed. In all specimens, the proximal screw fixations were similar, whereas in 6 specimens, distal locking screws were used, and in the other six specimens, far cortical locking screws. The overall stiffness, fracture movement, and pattern of strain distribution on the plate were measured in stable and unstable fractures under anatomic 1-legged stance. Specimens with unstable fracture were loaded to failure. ResultsNo statistical difference was found between the stiffness and fracture movement of the two groups in stable fractures. In the unstable fractures, the overall stiffness and fracture movement of the locking group was significantly higher and lower than the far cortical group, respectively. Maximum principal strain on the plate was consistently lower in the far cortical group, and there was no significant difference between the failure loads of the 2 groups. ConclusionThe results indicate that far cortical locking screws can reduce the overall effective stiffness of the locking plates and increase the fracture movement while maintaining the overall strength of the PFF fixation construct. However, in unstable fractures, alternative fixation methods, for example, long stem revision might be a better option.

Better Axial Stiffness of a Bicortical Screw Construct Compared to a Cable Construct for Comminuted Vancouver B1 Proximal Femoral Fractures

The aim of this study was to biomechanically evaluate the Locking attachment plate (LAP) construct in comparison to a Cable plate construct, for the fixation of periprosthetic femoral fractures after cemented total hip arthroplasty. Each construct incorporated a locking compression plate with bi-cortical locking screws for distal fixation. In the Cable construct, 2 cables and 2 uni-cortical locking screws were used for proximal fixation. In the LAP construct, the cables were replaced by a LAP with 4 bi-cortical locking screws. The LAP construct was significantly stiffer than the cable construct under axial load with a bone gap (P=0.01). The LAP construct offers better axial stiffness compared to the cable construct in the fixation of comminuted Vancouver B1 proximal femoral fractures.

Periprosthetic femoral fracture fixation: A biomechanical comparison between proximal locking screws and cables

BackgroundThe incidence of periprosthetic femoral fractures (PFF) around a stable stem is increasing. The aim of this biomechanical study was to examine how three different methods of fixation, for Vancouver type B1 PFF, alter the stiffness and strain of a construct under various configurations, in order to gain a better insight into the optimal fixation method. MethodsThree different combinations of proximal screws and Dall-Miles cables were used: (A) proximal unicortical locking screws alone; (B) proximal cables and unicortical locking screws; (C) proximal cable alone, each in combination with distal bicortical locking screws, to fix a stainless steel locking compression plate to five synthetic femora with simulated Vancouver type B1 PFFs. In one synthetic femora, there was a 10-mm fracture gap, in order to simulate a comminuted injury. The other four femora had no fracture gap, to simulate a stable injury. An axial load was applied to the constructs at varying degrees of adduction, and the overall construct stiffness and surface strain were measured. ResultsWith regards to stiffness, in both the gap and no gap models, method of fixation A was the stiffest form of fixation. The inclusion of the fracture gap reduced the stiffness of the construct quite considerably for all methods of fixation. The strain across both the femur and the plate was considerably less for method of fixation C, compared to A and B, at the locations considered in this study. ConclusionThis study highlights that the inclusion of cables appears to damage the screw fixations and does not aid in construct stability. Furthermore, the degree of fracture reduction affects the whole construct stability and the bending behaviour of the fixation.ORIGINAL ARTICLE

Reduction and Locked Plate Fixation of Periprosthetic Femoral Fractures Above a Total Knee Arthroplasty

Reduction and Locked Plate Fixation of Periprosthetic Femoral Fractures Above a Total Knee Arthroplasty

The Effect of Fracture Stability on the Performance of Locking Plate Fixation in Periprosthetic Femoral Fractures

Periprosthetic femoral fracture (PFF) fixation failures are still occurring. The effect of fracture stability and loading on PFF fixation has not been investigated and this is crucial for optimum management of PFF. Models of stable and unstable PPFs were developed and used to quantify the effect of fracture stability and loading in a single locking plate fixation. Stress on the plate was higher in the unstable compared to the stable fixation. In the case of unstable fractures, it is possible for a single locking plate fixation to provide the required mechanical environment for callus formation without significant risk of plate fracture, provided partial weight bearing is followed. In cases where partial weight bearing is unlikely, additional biological fixation could be considered.

Rigid versus flexible plate fixation for periprosthetic femoral fracture—Computer modelling of a clinical case

A variety of plate designs have been implemented for treatment of periprosthetic femoral fracture (PFF) fixation. Controversy, however, exists with regard to optimum fixation methods using these plates. A clinical case of a PFF fixation (Vancouver type C) was studied where a rigid locking plate fixation was compared with a more flexible non-locking approach. A parametric computational model was developed in order to understand the underlying biomechanics between these two fixations. The model was used to estimate the overall stiffness and fracture movement of the two implemented methods. Further, the differing aspects of plate design and application were incrementally changed in four different models. The clinical case showed that a rigid fixation using a 4.5mm titanium locking plate with a short bridging length did not promote healing and ultimately failed. In contrast, a flexible fixation using 5.6mm stainless steel non-locking plate with a larger bridging length promoted healing. The computational results highlighted that changing the bridging length made a more substantial difference to the stiffness and fracture movement than varying other parameters. Further the computational model predicted the failure zone on the locking plate. In summary, rigid fracture fixation in the case of PFF can suppress the fracture movement to a degree that prevents healing and may ultimately fail. The computational approach demonstrated the potential of this technique to compare the stiffness and fracture movement of different fixation constructs in order to determine the optimum fixation method for PFF.

A Biomechanical Comparison of Periprosthetic Femoral Fracture Fixation in Normal and Osteoporotic Cadaveric Bone

Several techniques are described for fixation of Vancouver B1 femoral shaft fractures after total hip arthroplasty. Twenty-four femurs were scanned by dual x-ray absorptiometry scanned and matched for bone mineral density. Femurs were implanted with a cemented simulated total hip prosthesis with a simulated periprosthetic femur fracture distal to the stem. Fractures were fixed with Synthes (Paoli, Pa) 12-hole curved plates and 4 different constructs proximally. Each construct was loaded to failure in axial compression. Constructs with locking and nonlocking screws demonstrated equivalent loads at failure and were superior in load at failure compared with cables. Cable constructs failed proximally. No proximal failures occurred in specimens fixed with screws and cables. A combination of locked or nonlocked screws and supplemental cable fixation is recommended for the treatment of Vancouver B1 periprosthetic femur fractures.

The biomechanics of plate fixation of periprosthetic femoral fractures near the tip of a total hip implant: cables, screws, or both?

Femoral shaft fractures after total hip arthroplasty (THA) remain a serious problem, since there is no optimal surgical repair method. Virtually all studies that examined surgical repair methods have done so clinically or experimentally. The present study assessed injury patterns computationally by developing three-dimensional (3D) finite element (FE) models that were validated experimentally. The investigation evaluated three different constructs for the fixation of Vancouver B1 periprosthetic femoral shaft fractures following THA. Experimentally, three bone plate repair methods were applied to a synthetic femur with a 5 mm fracture gap near the tip of a total hip implant. Repair methods were identical distal to the fracture gap, but used cables only (construct A), screws only (construct B), or cables plus screws (construct C) proximal to the fracture gap. Specimens were oriented in 15 degrees adduction to simulate the single-legged stance phase of walking, subjected to 1000 N of axial force, and instrumented with strain gauges. Computationally, a linearly elastic and isotropic 3D FE model was developed to mimic experiments. Results showed excellent agreement between experimental and FE strains, yielding a Pearson linearity coefficient, R2, of 0.92 and a slope for the line of best data fit of 1.06. FE-computed axial stiffnesses were 768 N/mm (construct A), 1023 N/mm (construct B), and 1102 N/mm (construct C). FE surfaces stress maps for cortical bone showed Von Mises stresses, excluding peaks, of 0-8 MPa (construct A), 0-15 MPa (construct B), and 0-20 MPa (construct C). Cables absorbed the majority of load, followed by the plates and then the screws. Construct A yielded peak stress at one of the empty holes in the plate. Constructs B and C had similar bone stress patterns, and can achieve optimal fixation.

The biomechanical analysis of three plating fixation systems for periprosthetic femoral fracture near the tip of a total hip arthroplasty

BackgroundA variety of techniques are available for fixation of femoral shaft fractures following total hip arthroplasty. The optimal surgical repair method still remains a point of controversy in the literature. However, few studies have quantified the performance of such repair constructs. This study biomechanically examined 3 different screw-plate and cable-plate systems for fixation of periprosthetic femoral fractures near the tip of a total hip arthroplasty.MethodsTwelve pairs of human cadaveric femurs were utilized. Each left femur was prepared for the cemented insertion of the femoral component of a total hip implant. Femoral fractures were created in the femurs and subsequently repaired with Construct A (Zimmer Cable Ready System), Construct B (AO Cable-Plate System), or Construct C (Dall-Miles Cable Grip System). Right femora served as matched intact controls. Axial, torsional, and four-point bending tests were performed to obtain stiffness values.ResultsAll repair systems showed 3.08 to 5.33 times greater axial stiffness over intact control specimens. Four-point normalized bending (0.69 to 0.85) and normalized torsional (0.55 to 0.69) stiffnesses were lower than intact controls for most comparisons. Screw-plates provided either greater or equal stiffness compared to cable-plates in almost all cases. There were no statistical differences between plating systems A, B, or C when compared to each other (p > 0.05).ConclusionsScrew-plate systems provide more optimal mechanical stability than cable-plate systems for periprosthetic femur fractures near the tip of a total hip arthroplasty.

A biomechanical evaluation of cortical onlay allograft struts in the treatment of periprosthetic femoral fractures

Periprosthetic femoral fractures are increasingly addressed through the use of cortical onlay allografting. This study was designed to determine the effect of allograft cortical strut length, configuration, cable number, cable tension and the use of wire or cable on the fixation of periprosthetic femoral fractures. Ten cadaveric femora-strut constructs were tested using anteroposterior and axial loads to simulate the forces at the hip during gait. A transverse fracture at the level of the tip of the femoral stem was simulated. A biaxial servohydraulic testing machine was used to apply one hundred cycles of craniocau-dal load of 1.53 × bodyweight at a frequency of one Hz, along with an anteroposterior load of 0.15 × bodyweight at one half Hz. Variables for different constructs included the strut length (twelve cm, sixteen cm, or twenty cm), the number of cables (two, three, or four above and below the fracture site), cable tension, strut configurations and orientation (single strut or two struts, adjacent or opposite), and the use of wires instead of cables. Cable tension was measured using a calibrated tensioner. Movement at the fracture site was measured using a precision optoelectronic camera system. There was significantly less motion when cables were used rather than wires (p<0.05). Increasing the number of cables decreased fracture motion in some directions (p<0.05) and increasing cable tension showed a trend towards decreased fracture motion. We observed strut fractures in four cases when a single strut alone was used to stabilise the fracture. There was a significant decrease in fracture motion if two struts were used rather than one (p<0.01), but there was no significant difference between the anterior and lateral, and the medial and lateral strut configurations. Decreasing the strut length from twenty cm to twelve cm led to a significant decrease in axial rotation (p<0.05). Our data strongly favour the use of two struts, rather than a single strut alone. Cables enhance fracture stability compared to wires, presumably due to increased tension and to different surface characteristics. Increasing the cable tension gave greater stability although this may not fully translate to the clinical situation because the cable may garrotte or fracture the strut. Increased cable number and decreased strut length also enhanced fracture stability. The cortical struts essentially represent biological bone plates. If appropriately selected and prepared they can be customised to fit any femur. Our improved understanding of this technique should contribute to high rates of fracture union with an increase in bone stock and overall bone strength.

The Mennen femoral plate for fixation of periprosthetic femoral fractures following hip arthroplasty

Periprosthetic fractures can be treated by various methods. The Mennen femoral plate used to be a common implant in our region to stabilise periprosthetic femoral fractures following hip arthroplasty. This device has been used in 16 patients in our region from three different centres. The periprosthetic femoral fractures occurred approximately 7 years after the hip arthroplasty procedure. After stabilisation of the fracture, patients were kept non-weight bearing. Weight bearing was commenced once there was clinical and radiological evidence of fracture union. About 75% of our patients had a complication following fixation of the fracture. In all of these patients the main complication was varus mal-union of the fracture. As per our study the Mennen femoral plate seems to be a weak fixation device. The plate is unable to counter the medial compressive forces on the femur leading to a varus collapse of the fracture.