Biphasic plating improves the mechanical performance of locked plating for distal femur fractures

Clinical management and innovation in fracture non-union

INTRODUCTION

With the introduction and continuous improvement in operative fracture fixation, even the most severe bone fractures can be treated with a high rate of successful healing. However, healing complications can occur and when healing fails over prolonged time, the outcome is termed a fracture non-union. Non-union is generally believed to develop due to inadequate fixation, underlying host-related factors, or infection. Despite the advancements in fracture fixation and infection management, there is still a clear need for earlier diagnosis, improved prediction of healing outcomes and innovation in the treatment of non-union.

AREAS COVERED

This review provides a detailed description of non-union from a clinical perspective, including the state of the art in diagnosis, treatment, and currently available biomaterials and orthobiologics.Subsequently, recent translational development from the biological, mechanical, and infection research fields are presented, including the latest in smart implants, osteoinductive materials, and in silico modeling.

EXPERT OPINION

The first challenge for future innovations is to refine and to identify new clinical factors for the proper definition, diagnosis, and treatment of non-union. However, integration of in vitro, in vivo, and in silico research will enable a comprehensive understanding of non-union causes and correlations, leading to the development of more effective treatments.

Advances in Dynamization of Plate Fixation to Promote Natural Bone Healing

The controlled dynamization of fractures can promote natural fracture healing by callus formation, while overly rigid fixation can suppress healing. The advent of locked plating technology enabled new strategies for the controlled dynamization of fractures, such as far cortical locking (FCL) screws or active plates with elastically suspended screw holes. However, these strategies did not allow for the use of non-locking screws, which are typically used to reduce bone fragments to the plate. This study documents the first in vivo study on the healing of ovine tibia osteotomies stabilized with an advanced active plate (AAP). This AAP allowed plate application using any combination of locking and non-locking screws to support a wide range of plate application techniques. At week 9 post-surgery, tibiae were harvested and tested in torsion to failure to assess the healing strength. The five tibiae stabilized with an AAP regained 54% of their native strength and failed by spiral fracture through a screw hole, which did not involve the healed osteotomy. In comparison, tibiae stabilized with a standard locking plate recovered 17% of their strength and sustained failure through the osteotomy. These results further support the stimulatory effect of controlled motion on fracture healing. As such, the controlled dynamization of locked plating constructs may hold the potential to reduce healing complications and may shorten the time to return to function. Integrating controlled dynamization into fracture plates that support a standard fixation technique may facilitate the clinical adoption of dynamic plating.

Promoting bone callus formation by taking advantage of the time-dependent fracture gap strain modulation

Delayed union and non-union of fractures continue to be a major problem in trauma and orthopedic surgery. These cases are challenging for the surgeon. In addition, these patients suffer from multiple surgeries, pain and disability. Furthermore, these cases are a major burden on healthcare systems. The scientific community widely agrees that the stability of fixation plays a crucial role in determining the outcome of osteosynthesis. The extent of stabilization affects factors like fracture gap strain and fluid flow, which, in turn, influence the regenerative processes positively or negatively. Nonetheless, a growing body of literature suggests that during the fracture healing process, there exists a critical time frame where intervention can stimulate the bone's return to its original form and function. This article provides a summary of existing evidence in the literature regarding the impact of different levels of fixation stability on the strain experienced by newly forming tissues. We will also discuss the timing and nature of this "window of opportunity" and explore how current knowledge is driving the development of new technologies with design enhancements rooted in mechanobiological principles.

IFM calculator: An algorithm for interfragmentary motion calculation in finite element analysis

BACKGROUND

Interfragmentary motion (IFM) is a complex state that significantly impacts the healing process of fractures following implant placement. It is crucial to fully consider the IFM state after implantation in the design and biomechanical testing of implants. However, current finite element analysis software lacks direct tools for calculating IFM, and existing IFM tools do not offer a comprehensive solution in terms of accuracy, functionality, and visualization.

METHODS

In our study, we developed a Python-based algorithm for calculating IFM that addresses limitations. Our algorithm automatically calculated IFM distances, sliding distances, gaps, as well as the angles and rotation of the two fracture surfaces using all nodes on both sides of the fracture ends. Researchers could input data and selected desired parameters in the interface. The algorithm then performed the necessary calculations and presented the results in a clear and concise manner. The algorithm also provided comprehensive data export capabilities, allowing researchers to customize analyses based on specific needs.To provide a more intuitive demonstration of the calculation process and usage of IFM-Cal, we conducted simulations in Ansys using two rectangular blocks to compare the accuracy and function of three different methods (Point based method, contact tool and IFM-Cal).

RESULTS

The point-based method and the contact tool could not accurately calculate IFA, while IFM-Cal could provide a comprehensive evaluation of IFA. In simulation 1, the IFM distances calculated using the point sampling method, contact tool, and IFM-Cal were 2.00 mm, 3.15 mm, and 2.00 mm, respectively. In simulation 2, both the point sampling method and contact tool failed to calculate the interfragmentary angle (IFA), while the IFM-Cal algorithm estimated an angle of -7.87°, which had a small error compared to the ground-truth value of 7.9°.

CONCLUSION

We have developed an algorithm for computing IFM which can be utilized in finite element analysis and biomechanical experiments. By conducting comparative simulations with other existing algorithms, we have demonstrated the superior accuracy and expanded evaluation capabilities of our algorithm.

Effect of knee osteoarthritis on the postoperative outcome of proximal femoral nail anti-rotation in the treatment of intertrochanteric fractures in the elderly: a retrospective analysis

BACKGROUND

The proximal femoral nail anti-rotation (PFNA) is a commonly used internal fixation system for intertrochanteric fractures (IFs) in older adults. Knee osteoarthritis (KOA) is a degenerative lower extremity disease that occurs most frequently in the elderly. Some patients have already had KOA before the IFs. However, whether KOA impacts the postoperative outcome of IFs has not been reported.

OBJECTIVE

This study aimed to investigate the effect of KOA on the fracture side on the outcome after PFNA for IFs in the elderly.

METHODS

Between January 2016 and November 2021, 297 elderly patients treated with PFNA for IFs were enrolled in this study. They were divided into two groups according to the American Rheumatism Association KOA clinical and radiographic criteria: the control group and the KOA group. Intraoperative bleeding, operative time, length of hospital stay, postoperative time out of bed, fracture healing time, postoperative complications, postoperative Harris hip function score, and Barthel ability to daily living Score were compared between the two groups. Follow-up was routinely scheduled at 1, 3, 6, and 12 months postoperatively.

RESULTS

Based on the exclusion criteria, 254 patients who met the requirements were left to be included in this study, including the control group (n = 133) and the KOA group (n = 121). Patients were followed up for a mean of 17.5 months (12-24 months). There was no significant difference between the two groups in preoperative demographic data, intraoperative blood loss, operation time, and length of stay in the hospital. The control group was statistically significant compared to the KOA group in terms of postoperative time out of bed (17.8 ± 4.0 days vs. 19.1 ± 5.8 days), fracture healing time (13.7 ± 2.2 weeks vs. 14.6 ± 3.7 weeks), and postoperative complications (12.8 vs. 23.1%). The Harris hip function score and Barthel ability to daily living score were higher in the control group than in the KOA group at 1, 3, 6, and 12 months postoperatively (the control group: 63.8 ± 10.9, 71.8 ± 10.3, 81.5 ± 8.7, and 91.6 ± 6.3 vs. The KOA group 61.0 ± 10.4, 68.6 ± 9.1, 79.0 ± 9.2, and 88.5 ± 5.9).

CONCLUSIONS

In elderly patients with IFs combined with KOA of the fracture side treated with PFNA internal fixation, KOA increases the incidence of postoperative complications of the fracture, prolongs postoperative time out of bed and fracture healing, and reduces postoperative hip function and ability to daily living. Therefore, treating KOA on the fractured side needs to be considered when treating IFs in the elderly.

Effect of Physiotherapy on a Rare Case of Malunion of Femur and Patellar Fracture in a 43-Year-Old Male: A Case Report

The hip is a ball-and-socket joint surrounded by strong and well-balanced muscles that allow for a wide range of motion in many physical planes. Iliofemoral, ischiofemoral, and pubofemoral are the three major ligaments of the hip joint that provide stability to the joint. Supracondylar femoral fractures are common in old age and can be caused in young people due to accidents or traumatic causes. These types of fractures are complicated to fix surgically due to different architectural designs. If not treated appropriately, these can cause malunion or non-union of the joint. The knee joint is a synovial joint of the hinge type. It has two major degrees of movement, which are flexion and extension. However, rotation in both the medial and lateral directions is possible to some extent in the joint. Patellar fractures can be transverse, vertical, comminuted, marginal, or osteochondral. In this case report, we present a 43-year-old male patient who had a history of falling from a bike. He was diagnosed with a comminuted supracondylar fracture of the left femur and a comminuted fracture of the patella on the left side on an X-ray. For this, he was managed with open reduction, internal fixation, and vacuum-assisted closure (VAC). Physiotherapy rehabilitation was programmed to attain a good and fast recovery for the patient to make him functionally independent and improve his quality of life.

Influence of knee flexion on early femoral fracture healing: A combined analysis of musculoskeletal dynamics and finite elements

BACKGROUND AND OBJECTIVES

Knee flexion causes a certain amount of misalignment and relative movement of the fractured ends of the femur fracture, and if the flexion angle is too large it will affect the stability of the fracture and the healing process, making it challenging to design a safe range of flexion. However, due to a lack of basic understanding of the effect of knee flexion on the mechanical environment at the fracture site, clinicians are often unable to provide an objective and safe range of motion in flexion based on subjective experience. The aim of this study was to evaluate the effect of knee flexion on plate and fracture healing using finite element analysis (FEA).

METHODS

A human musculoskeletal model was constructed based on CT scan data, and the mechanical properties of the fracture site were changed by adjusting the knee flexion angle. The joint forces, muscle forces and moments acting on the femur were obtained by inverse dynamics analysis, and the biomechanical properties of the fracture-plate system were analyzed using finite elements. A finite element model of the fracture-plate system without muscle loading was also constructed. The effect of knee flexion on the safety of plate fixation and fracture healing was evaluated in terms of the biomechanical properties of the plate and the interfragmentary motion of the fracture.

RESULTS

As the knee flexion angle increases, the von Mises stress of the locked compression plate (LCP) first increases, then decreases, then increases again. The deformation from compression bending to tension twisting occurs simultaneously. At 30° of flexion, shear interfragmentary motion (SIM) was dominant and inhibited fracture healing; at more than 45° of flexion, the plate was twisted and deformed to the lateral side of the body, and the fracture site underwent greater misalignment and relative motion, with destructive effects on bone scabs and healing tissues. If muscle loading is not taken into account, the plate will undergo predominantly bending deformation and will overestimate the interfragmentary strain in the far and near cortex.

CONCLUSIONS

Knee flexion causes the plate to deform from compression bending to extension and torsion, which has an important impact on the safety and healing process of the fracture, and this study provides a biomechanical basis to guide the clinician in the post-operative rehabilitation of femoral fractures in the clinical setting.

Current standard of care for distal femur fractures in Germany and Switzerland

BACKGROUND

Distal femur fractures occur with an incidence of 4.5/100,000 and show a prevalence of 0.4%. Causes include low-impact trauma in older patients and high-impact trauma in younger patients without pre-existing medical conditions. The aim of this study was to perform a comprehensive evaluation of trauma mechanisms, trauma-promoting factors, comorbidities, medication history and type of surgical care to provide an overview of the causes of injury and the most appropriate therapeutic approach.

METHODS

In this multicenter cohort study a retrospective analysis of 229 patients who sustained a distal femur fracture between January 2011 and December 2020 was performed. Individual fracture patterns, fracture predisposing factors, concomitant disease profiles, medication history, treatment strategy and associated complications were analyzed.

RESULTS

229 patients were included in the retrospective analysis. A total of 113-type 33 A, 50-type 33 B and 66-type 33 C fractures were diagnosed, of whom 92% received a lateral locking plate osteosynthesis. There was a complication in 14.4% of all cases, of which 6.1% were attributable to infection. Significant risk factors for developing a complication were an increased BMI (29.9 ± 8.5 kg/m2; p = 0.04), fracture displacement of over half a shaft width (p < 0.001) and AOC fractures (p < 0,016), specifically C2 fractures (p < 0,008).

CONCLUSION

In this multicenter retrospective cohort study, lateral locking plate osteosynthesis was the method of choice and was selected in over 90% of cases, regardless of the fracture classification and risk factors. A complication rate of 14.4% emphasizes the necessary analysis of patient- and care-specific risk factors and a resulting adjustment of the therapy strategy. An increased BMI (29.9 ± 8.5 kg/m2; p = 0.04), fracture displacement of over half a shaft width (p < 0.001) and AOC fractures (p < 0,016), specifically C2 fractures (p < 0,008) increase the risk of developing a complication and should prompt an early switch to a treatment strategy that provides more stability.

The absence of immediate stimulation delays bone healing

AIM

Secondary bone healing requires an adequate level of mechanical stimulation expressed by the extent of interfragmentary motion in the fracture. However, there is no consensus about when the mechanical stimulation should be initiated to ensure a timely healing response. Therefore, this study aims to compare the effect of the immediate and delayed application of mechanical stimulation in a large animal model.

METHODS

Twelve Swiss White Alpine sheep underwent partial osteotomy of a tibia that was stabilised with an active fixator inducing well-controlled mechanical stimulation. Animals were randomly assigned into two groups with different stimulation protocols. The immediate group received daily stimulation (1000 cycles/day) from the first day post-operation, while in the delayed group, stimulation began only on the 22nd day post-operation. Healing progression was evaluated daily by measuring the in vivo stiffness of the repair tissue and by quantifying callus area on weekly radiographs. All animals were euthanised five weeks post-op. Post-mortem callus volume was determined from high-resolution computer tomography (HRCT).

RESULTS

Fracture stiffness (p < 0.05) and callus area (p < 0.01) were significantly larger for the immediate group compared to the delayed stimulation group. In addition, the callus volume measured on the post-mortem HRCT showed 319 % greater callus volume for the immediate stimulation group (p < 0.01).

CONCLUSIONS

This study demonstrates that a delay in the onset of mechanical stimulation retards fracture callus development and that mechanical stimulation already applied in the early post-op phase promotes bone healing.

Influence of muscle loading on early-stage bone fracture healing

Designing weight-bearing exercises for patients with lower-limb bone fractures is challenging and requires a systematic approach that accounts for patient-specific loading conditions. However, 'trial-and-error' approaches are commonplace in clinical settings due to the lack of a fundamental understanding of the effect of weight-bearing exercises on the bone healing process. Whilst computational modelling has the potential to assist clinicians in designing effective patient-specific weight-bearing exercises, current models do not explicitly account for the effects of muscle loading, which could play an important role in mediating the mechanical microenvironment of a fracture site. We combined a fracture healing model involving a tibial fracture stabilised with a locking compression plate (LCP) with a detailed musculoskeletal model of the lower limb to determine interfragmentary strains in the vicinity of the fracture site during both full weight-bearing (100% body weight) and partial weight-bearing (50% body weight) standing. We found that muscle loading significantly altered model predictions of interfragmentary strains. For a fractured bone with a standard LCP configuration (bone-plate distance = 2 mm, working length = 30 mm) subject to full weight-bearing, the predicted strains at the near and far cortices were 23% and 11% higher when muscle loading was included compared to the case when muscle loading was omitted. The knee and ankle muscles accounted for 38% of the contact force exerted at the knee joint during quiet standing and contributed significantly to the strains calculated at the fracture site. Thus, models of bone fracture healing ought to account explicitly for the effects of muscle loading. Furthermore, the study indicated that LCP configuration parameters play a crucial role in influencing the fracture site microenvironment. The results highlighted the dominance of working length over bone-plate distance in controlling the flexibility of fracture sites stabilised with LCP devices.

A Bioinspired Orthopedic Biomaterial with Tunable Mechanical Properties Based on Sintered Titanium Fibers

Inadequate mechanical compliance of orthopedic implants can result in excessive strain of the bone interface, and ultimately, aseptic loosening. It is hypothesized that a fiber-based biometal with adjustable anisotropic mechanical properties can reduce interface strain, facilitate continuous remodeling, and improve implant survival under complex loads. The biometal is based on strategically layered sintered titanium fibers. Six different topologies are manufactured. Specimens are tested under compression in three orthogonal axes under 3-point bending and torsion until failure. Biocompatibility testing involves murine osteoblasts. Osseointegration is investigated by micro-computed tomography and histomorphometry after implantation in a metaphyseal trepanation model in sheep. The material demonstrates compressive yield strengths of up to 50 MPa and anisotropy correlating closely with fiber layout. Samples with 75% porosity are both stronger and stiffer than those with 85% porosity. The highest bending modulus is found in samples with parallel fiber orientation, while the highest shear modulus is found in cross-ply layouts. Cell metabolism and morphology indicate uncompromised biocompatibility. Implants demonstrate robust circumferential osseointegration in vivo after 8 weeks. The biometal introduced in this study demonstrates anisotropic mechanical properties similar to bone, and excellent osteoconductivity and feasibility as an orthopedic implant material.

Comparative evaluation of a patient-specific customised plate designs and screws for partial mandibular reconstruction

Mandibles with odontogenic tumors are often partially reconstructed with a metallic bone graft analogue with dental roots, crowns, along with a customized plate fixed with monocortical or bicortical screws, following resection of the tumor. In this study, two different designs of patient specific customized Ti reconstruction plates, solid and plate with holes, were considered. Fixation through both bicortical and monocortical screw types were investigated. FE models of the reconstructed mandibles were developed to analyse the influence of the plate-screw type combination on the load transfer across the mandibles under a mastication cycle. The effective homogenized orthotropic material properties of the lattice structures with 0.6 mm fibre diameter with 0.5 mm inter-fibre space were assigned to material properties for the bone graft analogue. The study shows that the combination of plate and screw types influences the state of stresses in the reconstructed mandible. Based on the results of this patient specific study, following resection of the tumor, either solid Ti plate with bicortical screws or Ti plate with holes along with monocortical screws may be used for partial mandibulectomy. It should also be noted that stresses in none of the plates or screws exceeded the yield limit for Ti under the mastication cycle indicating that the components are safe for mandibular reconstruction. However, the choice of this combination of reconstruction plates and screws is dependant on the condition and severity of the tumor in the diseased mandible.

Concepts and clinical aspects of active implants for the treatment of bone fractures

Nonunion is a complication of long bone fractures that leads to disability, morbidity and high costs. Early detection is difficult and treatment through external stimulation and revision surgery is often a lengthy process. Therefore, alternative diagnostic and therapeutic options are currently being explored, including the use of external and internal sensors. Apart from monitoring fracture stiffness and displacement directly at the fracture site, it would be desirable if an implant could also vary its stiffness and apply an intervention to promote healing, if needed. This could be achieved either by a predetermined protocol, by remote control, or even by processing data and triggering the intervention itself (self-regulated 'intelligent' or 'smart' implant). So-called active or smart materials like shape memory alloys (SMA) have opened up opportunities to build active implants. For example, implants could stimulate fracture healing by active shortening and lengthening via SMA actuator wires; by emitting pulses, waves, or electromagnetic fields. However, it remains undefined which modes of application, forces, frequencies, force directions, time durations and periods, or other stimuli such implants should ideally deliver for the best result. The present paper reviews the literature on active implants and interventions for nonunion, discusses possible mechanisms of active implants and points out where further research and development are needed to build an active implant that applies the most ideal intervention. STATEMENT OF SIGNIFICANCE: Early detection of delays during fracture healing and timely intervention are difficult due to limitations of the current diagnostic strategies. New diagnostic options are under evaluation, including the use of external and internal sensors. In addition, it would be desirable if an implant could actively facilitate healing ('Intelligent' or 'smart' implant). Implants could stimulate fracture healing via active shortening and lengthening; by emitting pulses, waves, or electromagnetic fields. No such implants exist to date, but new composite materials and alloys have opened up opportunities to build such active implants, and several groups across the globe are currently working on their development. The present paper is the first review on this topic to date.

Minimally invasive plate osteosynthesis for complex comminuted bone fractures in the Fraser's type II floating knee: a case report

Objective

Floating knee type IIC, according to Fraser’s classification, is an uncommon severe injury that typically occurs in polytrauma. In such cases, intra-articular fracture and the high degree of comminution and deformity of the mid-distal femur make fixation challenging. The purpose of this study was to demonstrate that minimally invasive plate osteosynthesis (MIPO) technology can simplify these complex problems and improve patient prognosis.

Case presentation

A 38-year-old man injured his left leg in a car accident, causing pain, swelling, deformity, and limited mobility on his left knee and thigh, and two small open wounds were noted mainly of the anterior aspect of the mid-distal thigh. Physical examination and computed tomography angiography of the lower limb confirmed that there was no damage to the neurovascular system. The clinical diagnosis was closed intra-articular fracture of the proximal tibia, open intra-articular fracture of the distal femur with extension to the diaphysis, and a patellar fracture on the ipsilateral knee. The treatment strategy involved a locking plate system applying MIPO technology. Postoperative evaluation of the patient was satisfactory, with immediate functional exercise, full weight-bearing after three months, and return to daily activity without pain. Final follow-up taken 3 years after surgery showed good lower limb alignment and complete plasticity of the bone structure, by which time the patient showed good limb function.

Conclusions

Minimally invasive techniques can provide a simple and effective treatment for some complex fractures.

[Current status and progress of locking plate in the treatment of distal femoral comminuted fracture]

OBJECTIVE

To review the current status and progress of locking plate for the treatment of distal femoral comminuted fractures.

METHODS

The related literature was extensively reviewed to summarize the current status and progress in the treatment of distal femoral comminuted fracture with locking plate from four aspects: the current treatment situation, the shortcomings of locking plate and countermeasures, the progress of locking technology, locking plate and digital orthopedic technology.

RESULTS

Treatment of distal femoral comminuted fractures is challenging. Locking plates, the most commonly used fixation for distal femoral comminuted fractures, still face a high rate of treatment failure. Double plates can improve the mechanical stability of comminuted fractures, but specific quantitative criteria are still lacking for when to choose double plates for fixation. The far cortial locking screw has shown good application value in improving the micro-movement and promoting the growth of callus. The biphasic plating is a development of the traditional locking plate, but needs further clinical examination. As an auxiliary means, digital orthopedic technology shows a good application prospect.

CONCLUSION

The inherent defect of locking plate is a factor that affects the prognosis of distal femoral comminuted fracture. The optimization of locking technology combined with digital orthopedic technology is expected to reduce the failure rate of treatment of distal femoral comminuted fracture.

Finite Element Analysis of Fracture Fixation

PURPOSE OF REVIEW

Fracture fixation aims to provide stability and promote healing, but remains challenging in unstable and osteoporotic fractures with increased risk of construct failure and nonunion. The first part of this article reviews the clinical motivation behind finite element analysis of fracture fixation, its strengths and weaknesses, how models are developed and validated, and how outputs are typically interpreted. The second part reviews recent modeling studies of the femur and proximal humerus, areas with particular relevance to fragility fractures.

RECENT FINDINGS

There is some consensus in the literature around how certain modeling aspects are pragmatically formulated, including bone and implant geometries, meshing, material properties, interactions, and loads and boundary conditions. Studies most often focus on predicted implant stress, bone strain surrounding screws, or interfragmentary displacements. However, most models are not rigorously validated. With refined modeling methods, improved validation efforts, and large-scale systematic analyses, finite element analysis is poised to advance the understanding of fracture fixation failure, enable optimization of implant designs, and improve surgical guidance.