Biomechanical Comparison of Locking Plate and Cancellous Screw Techniques in Medial Malleolar Fractures: A Finite Element Analysis

Biomechanical study of different fixation methods for posterior malleolus fracture

In this study, the biomechanical effect of six fixation methods for the treatment of posterior malleolus fracture (PMF) were analyzed by finite element method. Fixation models include five different cannulated screw fixation models (0°, 5°, 10°, 15°, 20°) and a posterior plate fixation model. The von Mises stress (VMS) and displacement were used as criteria to evaluate the biomechanical efficiency of the different fixation models. The results demonstrated that the VMS and displacement will increase as the load increases. The buttress plate has better fixed strength and biomechanics results than screws. When the screw fixation angle is 15°, the model has better fixed strength and biomechanical stability than other screws fixation models. Therefore, we recommend the screws fixation with angle of 15° for posterior malleolus fracture, which can be used to guide clinical operation.

Dedicated locking plate reduces non-union risk in open ankle fusion in obese patients

INTRODUCTION

Obesity is a growing public health concern. In ankle osteoarthritis, non-conservative treatment in advanced stages consists in ankle fusion, or else total ankle replacement, for which obesity is a relative contraindication. One of main complications of ankle fusion is non-union. Devascularization, obesity and fixation material are all factors involved in postoperative non-union, and have to be taken into account in surgical strategy for reliable results. The objective of this study was to compare the rate of ankle non-union in obese patients using quadruple screwing or a dedicated locking plate. The hypothesis was that the locking plate limits the risk of non-union in this population.

METHODS

All patients were obese (BMI>30kg/m2) and presented ankle osteoarthritis with>10° intra-articular deformity. The approach and joint preparation were performed via an anteromedial approach. Group S was composed of 32 patients, operated on by quadruple screwing; group P comprised 10 patients operated on using a dedicated locking plate. The main endpoint was a significant difference in the rate of non-union between the 2 groups. The secondary endpoint was improvement in pre- and 6-month postoperative AOFAS score.

RESULTS

Group S presented 31% non-union (10/32) and group P 0% (0/10) (p<0.05). Postoperative AOFAS score was significantly higher in group P: 67.8±10.4 [range, 40-92] vs. 83.1±8.0 [range, 64-92] (p<0.05).

CONCLUSION

The dedicated anterior locking plate is a technique of choice for ankle fusion in obese patients with intra-articular deformity>10°, to limit the risk of non-union.

LEVEL OF EVIDENCE

IV; retrospective study.

Finite element method analysis of bone stress for variants of locking plate placement

This study investigates the optimal placement of locking plate screws for bone fracture stabilization in the humerus, a crucial factor for enhancing healing outcomes and patient comfort. Utilizing Finite Element Method (FEM) modeling, the research aimed to determine the most effective screw configuration for achieving optimal stress distribution in the humerus bone. A computer tomography (CT) scan of the humerus was performed, and the resulting images were used to create a detailed model in SOLIDWORKS 2012. This model was then analyzed using ANSYS Workbench V13 to develop a finite element model of the bone. Four different screw configurations were examined: 4 × 0°, 4 × 10°, 4 × 20°, 2 × 20°; 2 × 0°. These configurations were subjected to bending in the XZ and YZ planes, as well as tension and compression along the Z axis. The research identified the 2 × 20°+2 × 0° configuration as the most beneficial, with average stress values below 30 MPa and peak stress values below 50 MPa in 3-point bending at the first screw. This configuration consistently showed the lowest stress values across all loading scenarios. Specifically, stress levels ranged from 20 MPa to 50 MPa for bending in the XZ plane, 20 MPa-35 MPa for bending in the YZ plane, 20 MPa-30 MPa for extension in the Z-axis, and 18 MPa-25 MPa for compression in the Z-axis. The 4 × 10° and 4 × 20° configurations also produced satisfactory results, with stress levels not exceeding 70 MPa. However, the 4 × 0° configuration presented considerable stress during bending and compression in the Z-axis, with stress values exceeding 100 MPa, potentially leading to mechanical damage. In conclusion, the 2 × 20°; 2 × 0° screw configuration was identified as the most effective in minimizing stress on the treated bone. Future work will involve a more detailed analysis of this methodology and its potential integration into clinical practice, with a focus on enhancing patient outcomes in bone fracture treatment.

A novel patella fracture fixation technique: finite element analysis

INTRODUCTION

Patella fractures account for approximately 1% of all bone fractures. The tension band wiring technique has been used in surgical treatment. However, there is no clear information about the location of the K-wires in sagittal plane. Thus, a transverse fracture line was created in the patella finite element model and fixed with Kirchner (k) wires and cerclage at different angles and compared with two different standard tension band models.

MATERIALS AND METHODS

A total of 10 finite element models were created to study AO/OTA 34-C1 patella fractures. Two models used the classical tension band method with either circumferential or 8-shaped cerclage wire. The other 8 models used K-wires placed at 45° or 60°, either alone or combination with cerclage wire. A force of 200 N, 400 N, and 800 N were applied at 45° knee angle and the resulting data fracture line opening, surface pressure and stress in the implants were analyzed through finite element analysis.

RESULTS

When all the results are considered, it was determined that the K-wires 60° crossing at the fracture line and with cerclage modeling was superior to the other models. The diagonal placement of the K-wires with cerclage (could be 45° or 60° medium) was superior to the reference models.

CONCLUSIONS

This study has shown that the new fixation method we propose could come to the fore as an alternative method to be used successfully in transverse patella fractures and lower complications. In transverse patellar fractures, the use of K-wires crossed at 60° may be a good alternative to the standard method.

Disease-Specific Finite element Analysis of the Foot and Ankle

Finite-element analysis is a computational modeling technique that can be used to quantify parameters that are difficult or impossible to measure externally in a geometrically complex structure such as the foot and ankle. It has been used to improve our understanding of pathomechanics and to evaluate proposed treatments for several disorders, including progressive collapsing foot deformity, ankle arthritis, syndesmotic injury, ankle fracture, plantar fasciitis, diabetic foot ulceration, hallux valgus, and lesser toe deformities. Parameters calculated from finite-element models have been widely used to make predictions about their biomechanical correlates.

Resumption of complete weight bearing after osteosynthesis of bimalleolar fractures using locking plates

INTRODUCTION

Bimalleolar fractures represent 9% of fractures and affect 187/100,000 people per year. The gold standard for osteosynthesis is a one-third tubular or lateral locking plate and compression screwing or use of tension band wiring, with complete weight bearing planned around the 6th week. The development of locking plates seems to allow earlier resumption of weight bearing. The objective of our study was to evaluate the clinical and radiological results after internal fixation of bimalleolar fractures using locking plates with complete weight bearing authorized from the outset. The hypothesis was that this does not predispose to cutaneous or mechanical complications.

HARDWARE AND METHOD

A continuous multi-operator retrospective study was performed. The clinical and radiological data of 55 patients operated on for bimalleolar fractures were collected. All underwent osteosynthesis with medial and lateral locking plates with authorization for weight bearing from the outset.

RESULTS

Complete weight bearing was resumed at 27.4 days 14.7 [7-60] postoperatively. No non-union or malunion was found. Two patients presented with delayed medial healing without the need for hardware removal. Two patients required removal of the lateral Plate 1 month postoperatively due to infection. Seven patients presented with discomfort related to hardware, justifying its removal at 1 year. The Kitaoka score at 1 year was 94.6 7.7 [71-100].

CONCLUSION

The use of medial and lateral locking plates in bimalleolar fractures associated with complete weight bearing authorized from the outset allows complete consolidation. There was no increase in cutaneous or mechanical complications.

LEVEL OF EVIDENCE

IV, retrospective study.

Efficacy of hook-type locking plate and partially threaded cancellous lag screw in the treatment of displaced medial malleolar fractures in elderly patients

INTRODUCTION

Traditionally, partially threaded cancellous lag screws (PTCS) are used for most medial malleolar fractures but are often challenging to execute in elderly patients because of the high risk of postoperative complications. Limited literature explores whether hook-type locking compression plates (LCPs) reliably offer better outcomes than PTCS in elderly patients. We aimed to compare the midterm radiologic and clinical outcomes between hook-type LCP and PTCS for medial malleolar fractures in an elderly population.

METHODS

We included 258 patients, aged 65 years and above, treated with either a hook-type locking plate (hook LCP group: 121 patients) or PTCS (screw group: 137 patients), and with follow-ups of at least 36 months in this retrospective study. Radiographic assessments included the union rate and interval to fracture union. Clinical assessment included the postoperative complications and revision procedures.

RESULTS

Although a significantly higher rate of comminuted fractures was observed in the hook LCP group than in the screw group (p < .001), no significant difference in the union rate was observed between the two groups (hook LCP group: 93.4% vs. screw group: 89.8%, p = .151), and a significantly shorter interval to union was observed in the hook LCP group (10.2 ± 7.0 vs. 12.3 ± 6.7 weeks, p = .015). There was a trend toward a lower rate of complications, including revision procedures, in the hook LCP group than in the screw group (19.9% vs. 28.5%, p = .107 and 6.6% vs. 13.8%, p = .074).

CONCLUSION

Hook-type LCP may be an alternative option for treating medial malleolar fractures with comminution in elderly patients.

Effect of coronal fracture angle on the stability of screw fixation in medial malleolar fractures: A finite element analysis

Malleolar screw fixation is the most widely used treatment method for medial malleolar (MM) fractures. Here, although buttress plate fixation is advocated for vertical MM fractures, the angular discrimination between oblique and vertical MM fractures is still not fully understood. The purpose of this study is to test the adequacy of screw fixation in MM fractures with different angles and determination of a ‘critical fracture angle’ to guide surgeons in the decision-making for screw fixation for MM fractures by utilizing an advanced engineering simulation approach. In addition to loading of the healthy tibia structure, various cases of the MM fracture double screw fixation (14 simulation scenarios in total with fracture angles between 30° and 90°, in 5° increments) were considered in this research and their static loading conditions just after fixation operation were simulated through nonlinear (geometric and contact nonlinearity) finite element analysis (FEA). Patient-specific computed tomography scan data, parametric three-dimensional solid modelling and finite element method (FEM) based engineering codes were employed in order to simulate the fixation scenarios. Visual and numerical outputs for the deformation and stress distributions, separation and sliding behaviours of the MM fracture fragments of various screw fixations were clearly exhibited through FEA results. Minimum and maximum separation distances (gap) of 3.75 and 150.34 µm between fracture fragments at fracture angles of 30° and 90° were calculated respectively against minimum and maximum sliding distances of 25.87 and 41.37 µm between fracture fragments at fracture angles of 90° and 35°, respectively. The FEA results revealed that while the separation distance was increasing, the sliding distance was decreasing and there were no distinct differences in sliding distances in the scenarios from fracture angles of 30°–90°. The limitations and errors in a FEA study are inevitable, however, it was interpreted that the FEA scenarios were setup in this study by utilizing acceptable assumptions providing logical outputs under pre-defined boundary conditions. Finally, the fracture healing threshold for separation and/or sliding distance between fracture fragments was assigned as 100 µm by referring to previous literature and it was concluded that the screws fixed perpendicular to the fracture in a MM fracture with more than 70° angle with the tibial plafond results in a significant articular separation (>100 µm) during single-leg stand. Below this critical angle of 70°, two screws provide sufficient fixation.

Quantitative initial safety range of early passive rehabilitation after ankle fracture surgery

BACKGROUND

Early rehabilitation training after ankle fracture surgery is critical to healing and avoiding complications. Inappropriate or excessive motion may impede healing or even lead to secondary injury. Currently, there is a lack of scientific quantitative postoperative rehabilitation methods after ankle fracture. Our purpose was to develop a universal method of quantifying early passive rehabilitation training after surgery by finite element (FE) analysis.

METHODS

A three-dimensional (3D) FE model of normal ankle was reconstructed from a computed tomography scan of a healthy male adult. Six types of ankle fractures were considered based on AO classification. We exerted joint motion load to explore the effect of movement on ankle joint mechanics after surgery. The corresponding relationship between the Inter-bone displacement and range of motion was measured to quantifying the ankle range of motion. The 44A3.3 fracture was used as an example to describe the implementation process in detail.

RESULTS

During ankle movement, most of the stress was sustained by the internal fixation devices, and the ratio of stress borne by the implants ranged from 67.9 to 94.9%. Flexion/extension exercise did not cause extra stress on the ankle contact surfaces. Ligament traction was the reason for ankle load during flexion/extension motion. The range of early passive postoperative rehabilitation training for six types of ankle fractures (AO classification) were provided.

CONCLUSION

A quantitative method of early passive rehabilitation training after ankle fracture surgery was developed using FE analysis. This modeling method has universality for any fracture that can be reconstructed.

"Fishing net" suture augmenting tension-band wiring fixation in the treatment of inferior pole fracture of the patella

INTRODUCTION

Inferior pole fracture of the patella (IPFP) is difficult to repair and stabilize clinically. Although various fixation techniques have been developed, fixation strength and mobility remain daunting challenges to orthopedic surgeons. The goal of this research is to evaluate the biomechanical strength and clinical outcomes of a novel "fishing net" suture fixation procedure.

MATERIALS AND METHODS

Four finite element models, modified tension-band wiring fixation, anchor suture fixation, basket plate fixation and "fishing net" suture fixation were built to compare the fixing efficacy of "fishing net" suture fixation with three other fixation methods during IPFP fixation. From January 2018 to February 2019, 17 patients who suffered IPFP and treated by "fishing net" suture (FNS) fixation were compared with 20 patients treated by tension-band wiring (TBW) fixation in database and the two groups were evaluated postoperatively using the modified Cincinnati knee rating system.

RESULTS

Biomechanical evaluation showed that the relative displacement values of proximal patella measured by three pairs of points on both sides of the fracture line were the lowest using the "fishing net" suture fixation, while fixation using tension-band wiring and basket plate showed similar levels of stability that were less desirable than the "fishing net" method. As to clinical outcomes, there were 17 (100%) patients exhibited excellent or good results with no internal fixation failures in the FNS group compared to three internal fixation failures in the TBW group.

CONCLUSION

The biomechanical and clinical results suggest that the "fishing net" suture fixation is a viable candidate for fixation of IPFP.

In Silico Analysis of Bone Tension During Fixation of the Medial Malleolus Fracture After Ankle Joint Endoprosthesis

Total ankle arthroplasty (TAR) is a procedure alternative to arthrodesis which enables the biomechanical stabilization of the ankle joint. The procedure is associated with a high risk of complications, including fractures of the medial malleolus. In this study, the finite element method (FEM), based on CT examinations, was used to model the ankle fracture fixation after TAR. Three types of fracture stabilization were considered: screw, Blount staple, and both screw and Blount staple. In the in silico model, the maximum stress tension was found at prosthetic junctions with the base, cone, and talar components of the tibial prosthesis. When the fracture was stabilized with the Blount staple, tension along the cone of the tibial component was about 12% of the maximum tension. Stabilizations with the screw alone or Blount staple combined with a screw on the medial side of the cone induced tension in the immediate vicinity twice as high. In the area of the medial malleolus, the tension was alike for both types of stabilization. The tension was lowest when using the Blount staple alone. We conclude that, contrary to the hitherto clinical routine of using screws, fracture fixation using the Blount staple leads to the lowest bone tension around the fixation of the medial malleolus fracture after ankle joint endoprosthesis.

Comprehensive biomechanical analysis of three clinically used fixation constructs for posterior malleolar fractures using cadaveric and finite element analysis

Different fixation modalities are available for fixation of posterior malleolar fractures (PMFs), but the best method is still unclear. The purpose of this study was to carry out a comparative biomechanical analysis of three commonly used fixation constructs for PMFs using experimental and finite element analysis (FEA). 15 human cadaveric ankle specimens were randomly divided into three groups. Specimens in group-A were fixed with two anteroposterior (AP) lag screws, group-B with two posteroanterior (PA) lag screws, and for group-C, a posterior plate was used. Each model was subjected to axial load. Outcomes included loads for 0.5 mm, 1 mm, 1.5 mm, and 2 mm vertical displacements of posterior fragments were noted. 3D FE models were reconstructed from computed tomography (CT) images and subjected to vertical loads. The model’s stress, fracture step-off, and resultant strains in implants were also studied in 3D FE models. Significantly higher amounts of mean compressive loads were observed to cause the same amount of vertical displacements in plate group (265 ± 60.21 N, 796 ± 57.27 N, 901.18 ± 8.88 N, 977.26 ± 13.04 N) than AP (102.7 ± 16.78 N, 169.5 ± 19.91 N, 225.32 ± 15.92 N, 269.32 ± 17.29 N) and PA (199.88 ± 31.43 N, 362.80 ± 28.46 N, 431.3 ± 28.12 N, 541.86 ± 36.05 N) lag screws respectively (P < 0.05). Simulated micro-motion analysis demonstrated that fracture step-off values in plate group (0.03 ± 0.001 mm, 0.06 ± 0.003 mm and 0.13 ± 0.010 mm) were the lowest among the three groups (P < 0.001). The cancellous bone showed the highest amount of stress in AP and PA lag groups respectively, whereas the lowest stress was noted in the plate-group. This biomechanical study concluded that posterior plating is biomechanically the most stable fixation construct for PMFs fixation. AP and PA lag screws with higher bone stress and fracture step-off values have a high tendency of bone cut-through and loss of fixation respectively.