The mechanics of external fixation

Analysis of K-Wire and Olive Wire in Ilizarov Apparatus: A Comparative Study

Background

Orthopedic fixators depend on mechanical characteristics like stiffness and firmness. The Ilizarov Apparatus (IA) is a common surgical management approach to restructure the bone fractures. IA includes two wires, specifically K-wire and olive wire, to treat the fractures.

Methods

The functions of IA using K-wire and olive wire have been explored with experimental and finite element approach. To describe the stability of fixation and stiffness of olive wire and K-wire, the mechanical performance of the wires was evaluated experimentally as well as numerically by ANSYS software.

Results

The results obtained from the olive wire experimental setup with applied loads of 50 to 100 N, showed stiffnesses ranging from 13.85 to 14.58 N/mm and displacements ranging from 3.61 to 6.86 mm. Also, in analytical evaluation, the obtained stiffness ranges from 14.36 to 14.34 N/mm for loads of 50-100 N with a displacement of 3.48-6.97 mm.

Conclusions

A two-ring olive wire was found to be stiffer than a two-ring K-wire fixator under the same loading conditions. The goal of this study is to help orthopedic specialists assess the stiffness and stability of IA setups with olive and K-wires.

3D printing feasibility of a controlled dynamization device for external circular fixation

AIM

to assess the small-scale 3D printing feasibility and cost estimation of a device for controlled dynamization.

MATERIALS AND METHOD

The two-part device previously developed by our research group was printed with a carbon fiber-reinforced nylon filament (Gen3 CarbonX™ PA6+CF, 3DXTECH Additive Manufacturing) by a professional 3D printer (FUNMAT HT, Intamsys). Electricity, material, and labor costs for production in a Brazilian city in the Santa Catarina state were calculated.

RESULTS

The devices for controlled dynamization were successfully printed in accordance with the planned design and dimensions. Six out of 38 printed devices presented defects in the bolt hole and were discarded. The average printing time per device was 1.9 h. The average electricity, material, and labor costs per printed device were respectively US$0.71, US$13.55, and US$3.04. The total production cost per device reaches approximately US$20 by adding the average cost of defective devices (15 %).

CONCLUSION

3D printing of the controlled dynamization device is feasible and its cost seems affordable to most healthcare services, which could optimize the consolidation of diaphyseal fractures and reduce treatment time for patients.

In-vitro external fixation pin-site model proof of concept: A novel approach to studying wound healing in transcutaneous implants

External fixation is an essential surgical technique for treating trauma, limb lengthening and deformity correction, however infection is common, with infection rates ranging from 4.5 to 100% of cases. Throughout the literature researchers and clinicians have highlighted a relationship between excessive movement of the pin and skin and an increase in the patient's risk of infection, however, currently no studies have addressed this role of pin-movement on pin-site wounds. This preliminary study describes a novel in vitro pin-site model, developed using a full-thickness human skin equivalent (HSE) model in conjunction with a bespoke mechanical system which simulates pin-movement. The effect of pin-movement on the wound healing response of the skin equivalents was assessed by measuring the expression of pro-inflammatory cytokines. Six human skin equivalent models were divided into three test groups: no pin as the control, static pin-site wound and dynamic pin-site wound (n = 3). On day 3 concentrations of IL-1α and IL-8 showed a significant increase compared to the control when a static fixation pin was implanted into the skin equivalent (p < 0.05) and (p < 0.005) respectively. Levels of IL-1α and IL-8 increased further in the dynamic sample compared to the static sample (p < 0.05) and (p < 0.0005). This study demonstrates for the first time the application of HSE model to study external-fixation pin-movement in vitro. The results of this study demonstrated pin-movement has a negative effect on soft-tissue wound-healing, supporting the anecdotal evidence reported in the literature, however further analysis of wound heading would be required to verify this hypothesis.

Developments in circular external fixators: A review

Circular external fixators (CEFs) are successfully used in orthopedics owing to their highly favorable stiffness characteristics which promote distraction osteogenesis. Although there are different designs of external fixators, how these features produce optimal biomechanics through structural and component designs is not well known. Therefore, the aim of this study was to conduct a review on CEFs following the PRISMA statement. A search for relevant research articles was performed on Scopus and PubMed databases providing the related keywords. Furthermore, a patent search was conducted on the Google Patent database. 126 records were found to be eligible for the review. Different designs of CEFs were summarized and tabulated based on their specific features. A bibliometric analysis was also performed on the eligible research papers. Based on the findings, the developments of CEFs in terms of materials, automation, adjustment methods, component designs, wire-clamping, and performance evaluation have been extensively discussed. The trends of the CEF design and future directions are also discussed in this review. Significant research gaps include a lack of consideration towards ease of assembly, effective wire-clamping methods, and CEFs embedded with online patient-monitoring systems, among others. An apparent lack of research interest from low-middle and low-income countries was also identified.

Mechanical evaluation of the effect of the rod to rod distance on the stiffness of uniplanar external fixator frames

PURPOSE

To investigate the effect of the rod-to-rod distance on the mechanical stability of single-rod and double-rod external fixator frames.

METHODS

 Four different constructs, one single-rod and three double-rod constructs with different rod-rod distances, were subjected to the axial, bending, and torsional forces. The stiffness of different configurations was calculated.

RESULTS

 Single-rod configuration had statistically the lowest stiffness when subjected to the axial, bending, and torsional forces. Maximum stiffness against the axial and anterior-posterior bending forces was achieved when the rod-rod distance was adjusted to 50 mm (halfway between the first rod and the end of the Schanz pins). There was no statistically significant difference in lateral bending stiffness among different double-rod configurations (p value: 0.435). The maximum stiffness against torsional forces was achieved when the rod-rod distance was adjusted to 100 mm (the second rod at the end of the Schanz pins).

CONCLUSION

 Double-rod uniplanar external fixator frames are significantly stiffer than the single-rod constructs, and however, the rod-rod distance can significantly affect the construct stiffness. We found that a frame with 50 mm rod-rod distance was the optimum fixator among tested configurations that allowed a balance between axial, bending, and torsional stiffness of the construct.

The Influence of Sagittal Pin Angulation on the Stiffness and Pull-Out Strength of a Monolateral Fixator Construct

Monolateral pin-to-bar-clamp fixators are commonly used to stabilize acute extremity injuries. Certain rules regarding frame geometry have been established that affect construct stability. The influence of sagittal pin angulation on construct stiffness and strength has not been investigated. The purpose of this biomechanical study was to demonstrate the effect of a pin angulation in the monolateral fixator using a composite cylinder model. Three groups of composite cylinder models with a fracture gap were loaded with different mounting variants of monolateral pin-to-bar-clamp fixators. In the first group, the pins were set parallel to each other and perpendicular to the specimen. In the second group, both pins were set convergent each in an angle of 15° to the specimen. In the third group, the pins were set each 15° divergent. The strength of the constructions was tested using a mechanical testing machine. This was followed by a cyclic loading test to produce pin loosening. A pull-out test was then performed to evaluate the strength of each construct at the pin-bone interface. Initial stiffness analyses showed that the converging configuration was the stiffest, while the diverging configuration was the least stiff. The parallel mounting showed an intermediate stiffness. There was a significantly higher resistance to pull-out force in the diverging pin configuration compared to the converging pin configuration. There was no significant difference in the pull-out strength of the parallel pins compared to the angled pin pairs. Convergent mounting of pin pairs increases the stiffness of a monolateral fixator, whereas a divergent mounting weakens it. Regarding the strength of the pin-bone interface, the divergent pin configuration appears to provide greater resistance to pull-out force than the convergent one. The results of this pilot study should be important for the doctrine of fixator mounting as well as for fixator component design.

A Case of Closed Pilon Fracture Resulting in Soft-Tissue Necrosis and Treated with Reverse Sural Artery Flap and Circular External Fixation

Tibial pilon fractures are difficult to treat due to articular comminution and soft-tissue injuries caused by high-energy trauma. Open reduction and internal fixation is a commonly used method of treatment. However, it has a high risk of infection and soft-tissue complications due to the extensive detachment of soft tissue. We report on a case with a tibial pilon fracture and soft-tissue necrosis that we treated using limited internal fixation combined with a circular external fixator (LIFCEF) and reverse sural artery flap (RSAF) as part of an orthoplastic approach within the orthopedic surgery department alone, which obtained good results. A 51-year-old man was injured in a motorcycle accident and transported to a nearby hospital. X-rays at the time of injury showed tibial pilon fractures (AO Foundation/Orthopedic Trauma Association 43c3.3, Ruedi-Allgower: Type III). Soft-tissue necrosis with blisters on the medial side of the lower leg (AO soft-tissue classification: IC3-MT1-NV1) was observed. In addition, the patient was referred to our hospital on day 10 of the injury. LIFCEF was chosen for treating the fracture because plate fixation was accompanied by the risk of plate exposure, soft-tissue complications, and an increased skin defect area, and RSAF was chosen to reconstruct the soft tissue defect. Four years after the surgery, the American Orthopedic Foot and Ankle Score was 92 points. X-ray alignment evaluation showed mLDTA 93° and aADTA 91°. Stage 2 arthrosis was present according to the Takakura ankle osteoarthritis classification, but the patient was able to walk without pain. Tibial pilon fractures are difficult to treat due to articular comminution and soft-tissue injuries caused by high-energy trauma. The timing and choice of treatment are crucial concerning the soft tissue.

Half-pin Breakage in Multiplanar External Fixators Used for Pediatric Deformity Correction

BACKGROUND

Pediatric patients with leg length discrepancies and complex deformities may require multiplanar external fixators for correction. We have encountered 4 cases of half-pin breakage with the Orthex hexapod frame. The purpose of this study is to report factors associated with half-pin breakage and compare various deformity correction characteristics between 2 hexapod frames - Taylor Spatial Frame (TSF) and Orthex.

METHODS

Pediatric patients with lower extremity deformities treated with an Orthex or TSF at a single tertiary children's hospital between 2012 and 2022 were included for retrospective review. Variables compared between frame groups include frame configuration, half-pin/wire fixation, length achieved, angular correction, and frame time.

RESULTS

There were 23 Orthex frames (23 patients) and 36 TSF (33 patients) included. Four Orthex and zero TSF had proximal half-pin breakage. The Orthex group was younger on average (10 vs. 12 y, P=.04*) at the time of frame placement. The majority (52%) of Orthex frames were used for simultaneous lengthening and angular correction, while the majority (61%) of TSF was used for only angular correction. Orthex had more half-pins used for proximal fixation (median 3 vs. 2, P<0.0001*) and more frames with nonstandard configuration (7 (30%) vs. 1 (3%), P=0.004*). Orthex group had a longer total frame time (median 189 vs. 146 days, P=0.012*) and longer time required for regenerate healing (117 vs. 89 d, P=0.02*). There were no significant differences in length gained, angular correction, or healing index between Orthex and TSF. Nonstandard configuration, increased number of proximal half-pins, younger age at index surgery, and increased lengthening were associated with pin breakage.

CONCLUSIONS

This is the first study to report half-pin breakage while using multiplanar frames in pediatric lower extremity deformity correction. The Orthex and TSF groups consisted of significantly different patients and frame configurations, making it difficult to identify any specific cause for pin breakage. This study shows that pin breakage is likely caused by multiple factors and is associated with the increased complexity of deformity correction.

LEVEL OF EVIDENCE

Level III-Retrospective Comparison Study.

3D Printed Orthopaedic External Fixation Devices: A Systematic Review

BACKGROUND

External fixators are complex, expensive orthopaedic devices used to stabilize high-energy and complex fractures of the extremities. Although the technology has advanced dramatically over the last several decades, the mechanical goals for fracture stabilization of these devices have remained unchanged. Three-dimensional (3D) printing technology has the potential to advance the practice and access to external fixation devices in orthopaedics. This publication aims to systematically review and synthesize the current literature on 3D printed external fixation devices for managing orthopaedic trauma fractures.

METHODS

The Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) protocols were followed for this manuscript with minor exceptions. PubMed, Embase, Cochrane Review, Google Scholar, and Scopus online databases were systematically searched. Two independent reviewers screened the search results based on predetermined inclusion and exclusion criteria related to 3D printing and external fixation of fractures.

RESULTS

Nine studies met the inclusion criteria. These included one mechanical testing study, two computational simulation studies, three feasibility studies, and three clinical case studies. Fixator designs and materials varied significantly between authors. Mechanical testing revealed similar strength to traditional metal external fixators. Across all clinical studies, five patients underwent definitive treatment with 3D printed external fixators. They all had satisfactory reduction and healing with no reported complications.

CONCLUSIONS

The current literature on this topic is heterogeneous, with highly variable external fixator designs and testing techniques. A small and limited number of studies in the scientific literature have analyzed the use of 3D printing in this area of orthopaedic surgery. 3D printed external fixation design advancements have yielded promising results in several small clinical case studies. However, additional studies on a larger scale with standardized testing and reporting techniques are needed.

Clinical trial of a low-cost external fixator for global surgery use

PURPOSE

A low-cost modular external fixator for the lower limb has been developed for global surgery use. The purpose of this study is to assess outcome measures in the first clinical use of the device.

METHODS

A prospective cohort study was conducted with patients recruited in two trauma hospitals. Initial clinical procedure data were collected, and patients were followed up every two weeks until 12 weeks or definitive fixation. Follow-up assessed infection, stability, and radiographic outcomes. In addition, patient-reported outcomes and surgeons' feedback on device usability were collected by questionnaires.

RESULTS

The external fixator was used on 17 patients. Ten were mono-lateral, five were joint spanning, and two were delta configuration. One patient had a pin site infection at 12-week follow-up. All were stable when tested mechanically and using radiographic assessment, and 53% were converted to definitive fixation.

CONCLUSION

The low-cost external fixator developed is appropriate for use in global surgery trauma centres with good clinical outcomes.

PROSPECTIVE TRIAL REGISTRATION NUMBER AND DATE

SLCTR/2021/025 (06 Sep 2021).

Trends and Practices in Limb Lengthening: An 11-year US Database Study

Aim

Over the past couple of decades, limb lengthening has evolved to encompass various implants and techniques. The purpose of this study was to (1) determine trends in the utilisation of various limb lengthening techniques for the femur and tibia in the United States, (2) determine trends in 1-year readmission rate following limb lengthening procedures and (3) to study the relationship of limb lengthening implant used and payment method used with the underlying diagnosis associated with limb shortening.

Materials and methods

Inpatient data were acquired using the Healthcare Cost and Utilisation Project (HCUP) database from 2005 to 2015 from seven states in the United States. Patients with an International Classification of Diseases (ICD)-9 code for limb lengthening of the femur or tibia were included. A total of 2,563 patients were included. Data were analysed using descriptive statistics, and chi-square test was used for comparison of subcategories. Linear regression analysis was used to examine trends over time.

Results

There was a strong linear trend towards increasing proportional use of internal lengthening of the femur from 2011 to 2015 (R2 = 0.99) with an increase of 10.2% per year. A similar trend towards increasing proportional use of internal lengthening of the tibia was seen from 2011 to 2015 (R2 = 0.87) with an increase of 4.9% per year. There was a moderate correlation showing a decrease in readmission rate of 1.07% per year from 2005 to 2015 (R2 = 0.55). Patients with short stature had increased use of internal lengthening and self-payment compared to patients with congenital, post-traumatic or other diagnoses.

Conclusion

There was increasing use of internal lengthening techniques from 2011 to 2015. Patients with short stature had higher use of internal lengthening technique and self-pay for payment method.

Clinical significance

Intramedullary devices have seen increasing use for limb lengthening procedures. Lengthening technique and payment method may differ by underlying diagnosis.

How to cite this article

Mittal A, Allahabadi S, Jayaram R, et al. Trends and Practices in Limb Lengthening: An 11-year US Database Study. Strategies Trauma Limb Reconstr 2023;18(1):21-31.

Correction of severe lower extremity deformity with digital hexapod external fixator based on CT data

Purpose

Our goal was to examine the therapeutic effect of a self-designed digital six-axis external fixator technique for the correction of severe lower extremity deformities.

Patients and methods

Between January 2017 and December 2020, our institution employed self-developed digital hexapod external fixator technology (QSF), based on CT data, to gradually correct 28 severe tibial deformities, and 15 femurs underwent osteotomy and internal fixation. The mean patient age was 32.6 ± 14.3 years, and the mean follow-up duration was 27.4 ± 16.1 months. We also recoded and analyzed the values of preoperative and final follow-up MAD, mFTA, MPTA, LLD, mLDFA, LEFS, KSS, and functional score.

Results

The QSF adjustment duration was 21.4 ± 10.8 days, and the healing duration of the tibial osteotomy site was 17.6 ± 7.0 weeks. The preoperative MAD, mFTA, and MPTA were 54.1 ± 26.2 mm, 167.7 ± 15.7°, and 75.2 ± 12.0°, respectively. At the last follow-up, the MAD was 8.2 ± 9.9 mm, mFTA was 177.6 ± 3.4°, and MPTA was 87.6 ± 2.4°. Based on these data, we achieved significant improvement post operation. The preoperative LLD and mLDFA values were 13.8 ± 18 mm and 83.7 ± 10.8°, respectively, and the values were 7.6 ± 7.6 mm and 87.8 ± 2.6°, respectively, at the last follow-up. This indicated no significant difference in these values before and after the operation. Finally, the LEFS, KSS, and functional scores improved from preoperative 51.6 ± 11.2, 68.5 ± 11.7, and 67.8 ± 11.2 to postoperative 72.3 ± 6.1, 92.9 ± 3.4, and 94.2 ± 6.3, respectively.

Conclusions

Based on our analyses, the QSF technique accurately corrected severe multiplanar tibial deformities in adults. When combined with femoral osteotomy, satisfactory lower extremity alignment was obtained while correcting for femoral deformity. This technology has the advantages of simple operation, reliable fixation, less trauma, and less complications.

SPINE: An Initiative to Reduce Pressure Sore Recurrence

The recurrence rate after pressure sore reconstruction remains high. Primary inciting factors can be organized into efforts aimed at wound prevention: spasticity relief, pressure off-loading, infection and contamination prevention, nutrition optimization, and maximizing extremity function. This article presents our detailed protocol, SPINE, to address each inciting factor with a summary of cases at our facility and review best practices from evidence-based medicine in the literature.

Adjustable bone plate: from bench to operating room

Background/aim

We have designed an adjustable bone plate (ABP) which allows bone shortening and lengthening after fixation, which is a property not present in any of the plate systems available today. The aim of the current study was to examine the new ABP's segmental bone transfer capability for the treatment of a segmental bone defect in an animal model.

Materials and methods

Five sheep had ABPs attached to 10 of their tibias and bone defects of 15 mm in size were created. The pinion mechanism was moved with a manual screwdriver at a rate of 1mm/day for 15 days starting 3 days postoperatively. The animals were euthanized 3 months postoperatively, and the defect site and the transferred segment were evaluated by radiological and histological examination.

Results

The radiological results revealed successful transfers of 14.6 ± 1.2 mm of bone segment on all tibia defects without any complications. The histological evaluation showed new bone formation in both the extension and the docking sites. No rupture or breakage was observed within the plates.

Conclusion

We have presented the potential of a new generation ABP for use in segmental bone transfer in an animal model as well as for future clinical applications.

A Comparative Study of Treatment With External Fixator Versus Antibiotic Coated Intramedullary Nail in Infected Non-union Long Bones

Introduction: Infected non-union of bones shows problems in providing stability and controlling the infection. The treatment comprises debridement with or without the use of antibiotic cement and achieving stability by either external or internal fixation with or without bone grafting. The use of antibiotic-impregnated cement-coated intramedullary nailing gives stability and treats the infection, thereby permitting early mobilization. External fixation is a definitive mode of fracture stabilization indicated in cases of infected non-unions of the humerus, tibia, and juxta-articular bone. The present study was conducted to compare the results of management of infected non-union long bones treated with an external fixator (Ilizarov and Limb Reconstruction System (LRS)) and vancomycin-coated intramedullary nail.

Materials and method: The present prospective study was conducted on 40 study subjects aged >18 years, and were randomly divided using the alternative method into two groups. Group A: 20 Patients were treated with antibiotic-coated intramedullary interlocking nail (ACIIN). Group B: 20 patients were treated with the external fixator (LRS/Ilizarov). All patients were then evaluated post-operatively using laboratory investigations, and for any sign of inflammation or infection. Results were evaluated using association for the study and application of methods of Ilizarov (ASAMI) scoring system. Data were analyzed using the Statistical Package for Social Sciences (SPSS) version 20 (IBM Corp., Armonk, NY, USA).

Results: It was observed that 80.0% of patients in Group A, and 70% of subjects in Group B showed bony union, revealing a statistically significant (p-value<0.05) difference. Infection control, limb length discrepancy, and deformity were also assessed in both groups. Bone and functional outcomes were assessed using the ASAMI score in both groups. In LRS/Ilizarov, it was observed that 55% of subjects had no infection, 15% showed loosening, and 30% had an infection.

Conclusion: The ACIIN should not be used for bone defects more than 4 cm as it does not achieve stability and for these cases, procedures like external fixators (Ilizarov and LRS) should be used. Antibiotic-coated nail eliminated the complications of the external fixators like pin loosening, and pin infections and was technically less demanding. In our study, stiffness of adjacent joints was more in external fixators (LRS/Ilizarov) than ACIIN.

What Factors Correlate With Length of Stay and Readmission After Limb Lengthening Procedures? A Large-database Study

BACKGROUND

Indications and techniques for limb lengthening procedures have evolved over the past two decades. Although there are several case series reporting on the complications and efficacy of these techniques, limited data are available on length of stay and hospital readmission rates after these procedures.

QUESTIONS/PURPOSES

(1) What is the median length of stay after lower limb lengthening procedures, and is variability in patient demographics, preoperative diagnosis, and surgical technique associated with length of stay? (2) What is the 1-year readmission rate after lower limb lengthening procedures? (3) Is variability in patient demographics, preoperative diagnosis, and surgical technique associated with varying rates of hospital readmission?

METHODS

Patients who underwent femoral or tibial lengthening from 2005 to 2015 in seven states were identified using the Healthcare Cost and Utilization Project (HCUP) State Inpatient Databases. These databases include a large, diverse group of patients across a wide range of hospitals and socioeconomic backgrounds with inclusion of patients regardless of payer. Between 2005 and 2015, there were 3979 inpatient admissions that were identified as involving femoral and/or tibial lengthening procedures based on ICD-9 procedure codes; of those, 2% (97 of 3979) of the inpatient admissions were excluded from analysis because they had ICD-9 procedure codes for primary or revision hip or knee arthroplasty, and 10% (394 of 3979) of the inpatient admissions were excluded because they involved repeated admissions of patients with previous hospitalization data within the database. This yielded 3488 patients for analysis. The median (interquartile range) age of patients was 18 years (12 to 41), and 42% (1481 of 3488) of patients were women. A total of 49% (1705 of 3469) of patients were children (younger than 18 years), 19% (675 of 3469) were young adults (18 to 34 years), 24% (817 of 3469) were adults (35 to 59 years), and 8% (272 of 3469) were seniors (60 years and older). Length of stay and rates of readmission at 1 year after the lengthening procedure were calculated. Univariate analysis was performed to examine associations between age, race, payment method, underlying diagnosis, bone lengthened, and lengthening technique with length of stay and readmission rate. Factors found to be significantly associated with the outcome variables (p < 0.05) were further examined with a multivariate analyses.

RESULTS

Included patients had a median (IQR) length of hospital stay of 3 days (2 to 4). Given the poor explanatory power of the multivariate model for length of stay (R 2 = 0.03), no meaningful correlations could be drawn between age, race, underlying diagnosis, lengthening technique, and length of stay. The overall 1-year readmission rate was 35% (1237 of 3488). There were higher readmission rates among adult patients compared with pediatric patients (odds ratio 1.78 [95% confidence interval 1.46 to 2.18]; p < 0.001), patients with government insurance compared with commercial insurance (OR 1.28 [95% CI 1.05 to 1.54]; p = 0.01), and patients undergoing lengthening via external fixation (OR 1.61 [95% CI 1.29 to 2.02]; p < 0.001) or hybrid fixation (OR 1.81 [95% CI 1.38 to 2.37]; p < 0.001) compared with lengthening with internal fixation only.

CONCLUSION

When counseling patients who may be candidates for limb lengthening, providers should inform individual patients and their caretakers on the anticipated length of hospital stay and likelihood of hospital readmission based on our findings. Adult patients, those with government insurance, and patients undergoing hybrid or external fixator limb lengthening procedures should be advised that they are at greater risk for hospital readmission. The relationship of specific patient-related factors (such as severity of deformity or associated comorbidities) and treatment-related variables (such as amount of lengthening, compliance with physical therapy, or surgeon's experience) with clinical outcomes after lower limb lengthening and the burden of care associated with hospital readmission needs further study.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Complex distal tibia fractures treated with multi-planar external fixation - a single center experience

INTRODUCTION

Multi-planar external fixation is used for the management of complex distal tibia fractures. This study aims to describe our experience of treating distal tibia fractures using the Ilizarov, Taylor Spatial Frame and True-Lok Hex external fixation methods.

METHODOLOGY

We conducted a retrospective analysis of clinical and radiological records of all distal tibia fractures that were managed with multi-planar external fixation over a period of 3 years. A total of 13 cases were included, of which most were high-energy injuries.

RESULTS

The average age of the patients was 44 years old. 11 (85%) cases were high-energy trauma due to road traffic accidents. 8 (62%) cases involved the revision of a previous fixation method. Most (77%) cases were AO classification Type 3, and the majority (62%) of cases were open fractures. The average duration in the external fixator frame and time to radiological union was 5 months and 6 months respectively. The average malalignment at union was 1.3 degrees and 0.5 degrees in the coronal plane and sagittal plane respectively. All fractures involving the joint line were adequately restored. There were 2 (16%) case of non-union and 2 (15%) cases of pin site infections. 1 case required a corticotomy and subsequent lengthening.

CONCLUSION

Multi-planar circular external fixation is a reliable method to treat complex distal tibia fractures, both in the acute setting and as revision surgery. The rates of fracture union is high, with minimal malalignment. Although pin site infections are relatively common, they are uncomplicated and easily treated.

Biodegradable and Biocompatible Adhesives for the Effective Stabilisation, Repair and Regeneration of Bone

Bone defects and complex fractures present significant challenges for orthopaedic surgeons. Current surgical procedures involve the reconstruction and mechanical stabilisation of complex fractures using metal hardware (i.e., wires, plates and screws). However, these procedures often result in poor healing. An injectable, biocompatible, biodegradable bone adhesive that could glue bone fragments back together would present a highly attractive solution. A bone adhesive that meets the many clinical requirements for such an application has yet to be developed. While synthetic and biological polymer-based adhesives (e.g., cyanoacrylates, PMMA, fibrin, etc.) have been used effectively as bone void fillers, these materials lack biomechanical integrity and demonstrate poor injectability, which limits the clinical effectiveness and potential for minimally invasive delivery. This systematic review summarises conventional approaches and recent developments in the area of bone adhesives for orthopaedic applications. The required properties for successful bone repair adhesives, which include suitable injectability, setting characteristics, mechanical properties, biocompatibility and an ability to promote new bone formation, are highlighted. Finally, the potential to achieve repair of challenging bone voids and fractures as well as the potential of new bioinspired adhesives and the future directions relating to their clinical development are discussed.

A finite element study of a fractured tibia treated with a unilateral external fixator: The effects of the number of pins and cortical thickness

INTRODUCTION

In the early stage of fracture fixation, the aim of a unilateral external fixator (UEF) to stimulate healing and maintain stability may be suppressed by using inadequate number of pins. Cortical thinning due to age or osteoporosis endangers a successful fracture fixation.

MATERIALS AND METHODS

This study evaluates the initial strength and stability of the fracture fixation and tissue differentiation under the influences of variable cortical thickness (5 mm to 1 mm) and variable number of pins (1 to 4 in each bone fragment). A finite element program was utilised to develop 20 three-dimensional models of simplified diaphyseal tibia with fracture callus fixed with UEF. A mechano-regulation code based on the deviatoric strain theory was written and applied to simulate tissue differentiation. The values of von Mises stress, interfragmentary strain (IFS), and fibrocartilage index (FCI) were evaluated.

RESULTS

Cortical thinning from 5 mm to 1 mm increased IFS and FCI by an average of 30.3% and 18.7%, respectively, and resulted in higher stresses in the UEF and bone. Using 1 pin in each bone fragment produced excessive IFS in the models with 1 mm, 2 mm and 3 mm cortical thickness. Inserting the second pin into the bone fragment could considerably reduce the IFS and fibrocartilaginous tissue formation in the fracture site and improve load transmission to the fixator. Whereas inserting the fourth pin could minimally affect the mechano-biological environment of healing.

CONCLUSIONS

This study suggests that initial instability due to cortical thinning can be efficiently alleviated by adding the number of pins up to 3 in a UEF; additionally, it may improve the knowledge about applying UEFs adequately stable, whilst promoting inclination toward endochondral ossification, simultaneously.

Post-Operative Outcomes of Circular External Fixation in the Definitive Treatment of Tibial Plafond Fractures: A Systematic Review

Tibial plafond fractures (TPFs) are uncommon but potentially devastating injuries to the ankle. Operative treatments include internal and external fixation modalities. This article provides a systematic review of the clinical and functional outcomes of TPFs treated specifically with circular external fixation (CEF). A literature search of medical databases from inception to 13th November 2020 was performed. Original studies written in the English language reporting clinical, radiological, and functional outcome data of TPF treated with CEF were included. Patient demographics, fracture classification, open fractures, post-operative complications, clinical outcomes, radiological outcomes, and functional outcomes were collected. Quality and risk of bias were assessed using standardised scoring tools.In total, 16 studies were included. One prospective randomised study was identified. Collated data of 303 patients were analysed. The mean time to union was 21 weeks. Malunion occurred in 12.4%. The rate of deep infection was 4.8%, but no amputations were recorded. The risk of minor soft tissue infection (including pin-site infections) was 54%. Almost two-thirds achieved good-to-anatomic reduction radiologically. Approximately one-third reported excellent functional outcome scores. The quality of the studies was deemed satisfactory. A moderate risk of bias was acknowledged. This systemic review provides a summary of outcome data regarding CEF as a treatment for TPF. It highlights CEF as an acceptable treatment option with comparable results to that of internal fixation. Further higher-quality evidence is advised.

Avoiding iatrogenic vascular injury in tibial external fixation with half pins. An in-vivo study based on CT angiography

BACKGROUND

External fixation is an important tool in the management of variety of tibial fractures. Appropriate half pin insertion is important, to provide stable fixation without compromising the surgical field for definitive surgical procedures, and avoiding further damage to the important structures of the traumatized limb. There is paucity of literature about the optimal trajectories and safe corridors for half pins insertion based on in vivo studies. The available studies are based on anatomic atlases, cadaveric studies or half pin related complications.The aim of the current study is to present the findings of CT angiograms, in patients with external fixation of tibia, to enhance our understanding of optimal trajectories in safe corridors for half pins insertion.

MATERIAL AND METHODS

We performed a retrospective study of patients with external fixators on the tibia, who had undergone CT angiogram as part of pre-operative planning for orthoplastic reconstructive procedures. The relationship between the tips of the fixator half pins and named vessels of the leg were analyzed, pins within 5 mm of a named vessel were considered to be a risk of causing iatrogenic injury.

RESULTS

A total 51 patients, with in situ temporizing external fixators, with 134 half pins in different segments of the tibia were analyzed. More than 5 mm of penetration beyond the far cortex was noted in 47%, while in another 16% of pins penetration was more than 10 mm beyond the cortex. A tip to vessel distance (TVD) of 5 mm or less was noted in 28/134 (21%) of the pins, which highlights potential risk to the neurovascular bundles of the leg.

CONCLUSION

Risk of iatrogenic injury to neurovascular structures from half pin insertion can be reduced by meticulous use of fluoroscopy, by avoiding penetration beyond the far cortex, and avoiding exiting with half pins on the lateral surface in the distal 1/3rd of segment II of tibia. Moreover observing optimal trajectories and safe corridors for pin insertion, and selection of appropriate type of half pin can mitigate the risk to these structures.

An engineering review of external fixators

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Mechanical stability plays a key role in the effectiveness of external fixators.

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Strength and stiffness are the main factors which contributes towards stability.

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Modified configurations of linear, circular and hybrid fixators are investigated.

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Light weight composite materials are gradually replacing traditional metallic alloys.

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Existing research gaps in further optimizing external fixators are identified.

External Fixators are a common technique used to treat a variety of issues related to bones, predominantly due to its non-intrusive nature and versatility in terms of form and materials. While it is mainly used to treat open fractures, its other uses include limb lengthening, deformity correction, bone grafting, compression of non-unions and stabilization of dislocations. Its earliest use dates as far back as 400 BCE and has undergone significant improvements, focusing on both customization and optimization. These two aspects highlight the significance of complementing the orthopaedic requirements with engineering knowledge and its applications. Hence, this review paper aims to conduct an examination of recent developments of external fixators with a special focus on its structure, the usage of materials and biomechanical investigations using experimental and numerical techniques. The paper presents the existing level of engineering knowledge with regards to these aspects and identifies research gaps, which can improve the quality of the commonly used external fixators.

Application of locking compression plates as type 1 external fixators to treat unilateral mandibular fractures in four equids and one dromedary

OBJECTIVES

To describe a novel fixation of open, unstable, unilateral mandibular fractures applying a locking compression plate as an external skeletal fixator (ESF-LCP).

ANIMALS

Four horses and one dromedary.

STUDY DESIGN

Short case series.

METHODS

Animals presented with unstable, open, unilateral fractures of the mandible. Fracture fixation was performed under general anesthesia. A 4.5/5.5 narrow LCP was applied externally above the level of the skin and combined with intraoral tension band wiring.

RESULTS

Fracture fixation was achieved successfully using an ESF-LCP. Minimal tissue manipulation was required during application and removal of the construct. The ESF-LCPs provided adequate access to the wounds at the fracture site, were well tolerated, and did not interfere with any objects in the animals' environment. Mild drainage at the screw-skin interface developed in all cases, requiring early implant removal due to surgical site infection in one case. The use of longer plates was associated with superficial pressure necrosis of the skin in the masseter area in two cases. Implants were removed after 3 to 12 weeks, and the long-term functional outcome after 11 to 41 (median 13) months was good in all cases.

CONCLUSION

Stabilization of mandibular fractures with ESF-LCP led to good outcomes in this case series. The use of longer plates positioned more caudally and in a ventrolateral position seemed associated with surgical site infection and pressure necrosis of the skin.

CLINICAL SIGNIFICANCE

Use of a locking compression plate as an external skeletal fixator seems to offer a viable alternative to treat unilateral mandibular fractures, especially when these are open and/or infected.

Trifocal Tibial Bone Transport Using a Magnetic Intramedullary Nail: A Case Report

CASE

The patient sustained a pathologic fracture through chronic osteomyelitis of the tibia. Treatment involved resection of bone and soft tissue, leaving a 15-cm diaphyseal tibial defect. We designed a construct to allow for trifocal bone transport using a magnetic intramedullary lengthening nail connected to cables. This technique uses cables secured to the proximal tibia, the nail, and the transport segments.

CONCLUSION

This case details the successful use of trifocal cable-assisted bone transport through a magnetic lengthening intramedullary nail. This technique can successfully be used to reconstruct diaphyseal bone defects that are longer than the stroke length of the magnetic nail.

Surgical Management of Patients with Snakebite-Related Musculoskeletal Complication-A Single Institution Experience in Cambodia

BACKGROUND

Snakebite-related injury is a serious public health issue. In Cambodia, it is estimated that up to 21,500 cases of envenoming occurs from snakebites annually. Musculoskeletal disability is a major long-term complication associated with the injury. In this study, we aim to describe surgical management and rehabilitation in snakebite-related musculoskeletal injuries at Children's Surgical Centre, Phnom Penh, Cambodia.

METHODS

We conducted a retrospective case series analysis of patients with snakebite-related injury who were treated between January 1, 2002 and December 31, 2018. Surgical patients were divided into the early and late presenting groups (= < one year vs. > one year, respectively) based on their time interval from snake bite to time of presentation.

RESULTS

There were 88 patients who presented with snakebite-related musculoskeletal injury during the cohort study period. Majority of them were male (n = 62, 71%) and had a median age of 24 years old (IQR 17-44). The injuries were all in the upper and lower limbs though lower limb injury was more common in female patients (81% vs. 48%, Fisher's test p = 0.005). The median time interval from snakebite to time of treatment was 3 years (IQR 3 months-11 years). In this study, 65 patients received surgical interventions. An ulcerated wound was the most common symptom among the early presenting group (78% vs. 24%), while scar contracture was most common among the late group (76% vs. 22%) (Fisher's test p < 0.0001). For management, surgical debridement was the most common primary intervention for the early group (52% vs. 19%), and contracture release was the most common for patients in the late group (62% vs. 15%) (Fisher's test p = 0.0004). Overall, the postoperative complication rate was highest in the late presenting group (34% vs. 3%, Fisher's test p = 0.005).

CONCLUSION

More than half of the patients presented with musculoskeletal injury require surgical correction. Our study demonstrated that scar contracture is the most common complaint among the late presenting group and is associated with high postoperative complication rate.

Application of unilateral external fixation by the "joystick technique" in the treatment of pediatric tibia shaft fractures: technical note

Background

The aims of current study were to present the clinical outcomes in patients with pediatric tibia shaft fractures who were treated with unilateral external fixation combined with joystick for fracture reduction and describe the details of our technique.

Methods

We retrospectively analyzed the patients with pediatric tibia shaft fractures who were treated with unilateral external fixation combined with joystick for fracture reduction between July 2018 and March 2020. The clinical outcomes were evaluated.

Results

A total of 23 patients were included in the current study with the average age of 8.0 years (ranged 4–14 years). The average duration of hospital and follow-up were 5.9 days (ranged 4–8 days) and 17.4 months (ranged 8–27 months), respectively. At postoperative 3 days, the visual analog scale (VAS) score was 3.1 ± 1.43, which was significantly lower than the preoperative score of 7.3 ± 1.5. Of these, 2 cases showed redness and swelling of pin-tract and exudation at postoperative 1 month, who improved after oral antibiotics without causing fixation failure. The average time to full weight-bearing without crutches was 5.1 weeks (ranged 3–8 weeks). All patients achieved fracture healing and good functional recovery. No complications including fixation failure, reoperation, epiphyseal injury occurred, infection around implants, vessel damage, nerve damage, and limitation of joint movement were observed. The Johner-Wruh scores showed that 21 cases (91.3%) were “excellent” and 2 cases (8.7%) were “good.”

Conclusions

This procedure had advantages of simple operation, minimum trauma, early recovery of lower limb function, and no risk of complications. It may provide a new choice for children with tibia shaft fractures who require surgical treatment.

The efficacy of ilizarov method for management of long tibial bone and soft tissue defect

INTRODUCTION

Patients with open fracture Gustillo-Anderson grade 3 had undergone several surgical procedures, but still ended up with expose long dead bone or infected. Illizarov method was used to address long bone and soft tissue defect after re-debridement with radical resection of long dead bone or infected segment.

METHODS

We included 14 patients (mean age: 30.86 ± 11.49) with non-union tibial fracture with long dead and infected bone segment who had undergone several debridement, bone grafting or spacer and soft tissue closure procedure due to open fracture of tibia grade 3. The subjects underwent re-debridement with radical resection of dead or infected bone segment followed by Illizarov method to perform bone transport procedure for bone defect filling and simultaneously restore severe soft tissue loss and bone lengthening procedure.

RESULTS

All subjects had achieved satisfactory results with mean docking period of bone transport 3.78 ± 0.54 months, union time at the docking side 7 (5.5-9) months. Soft tissue was covered and no recurrence of infection. Three subjects had Leg Length Discrepancy (LLD) of 1 cm, whereas the remaining had zero discrepancy. No significant pain was observed at final follow-up and 4 patients had ankle joint stiffness.

CONCLUSION

The Illizarov method can effectively address long bone and soft tissue defects by distraction osteogenesis through bone transport procedure that filling the defect gradually without bone graft and simultaneously enhancing soft tissue closure without tertiary soft tissue procedure subsequently followed with bone lengthening procedure to correct the limb length discrepancy.

Evaluation of the Structural Behaviour of a Unilateral External Fixator for Osteosynthesis

Background:

External fixation is an osteosynthesis technique particularly useful in trauma surgery and Damage Control Orthopedics (DCO). However, complications, such as pin loosening and pin tract infections, are fairly common. For reducing thermal damage and infection rates, monocortical pins have been proposed as an alternative to the most used bicortical pins. However, there is a lack of studies regarding their mechanical properties.

Objective:

The aim of the study is to assess the static and dynamic stability of a unilateral external fixator experimentally when applied through monocortical pins for the reduction of femur and tibia fractures.

Methods:

A modular unilateral external fixator was used and a total number of 6 pins were used per test. The static tests were performed in displacement control by applying a vertical displacement to the upper fixture at 1 mm/min until a tension load of 380 N was reached. The dynamic tests were performed by applying a sinusoidal displacement. During each test, forces and crosshead displacements were acquired. Two different stiffness indexes were assessed.

Results:

By comparing the two anatomic regions, it was found that the fixator behaves stiffer when mounted on the femur, regardless of the pins used, while stiffnesses comparable to the femur ones are reached by the tibia when 4 mm diameter pins are used. Static analysis revealed excellent fixator stability when implanted with 4 mm diameter monocortical pins on both anatomic regions. On the contrary, two tibia and one femur samples showed failures at the bone-pin interface when 3 mm diameter pins were used.

Conclusion:

Dynamic analysis showed no substantial difference between the tested configurations and confirmed the fixator's ability to sustain cyclic loading without further damage to the sample.

A probabilistic approach for modelling bone fracture healing under Ilizarov circular fixator

Bone fracture treatments using Ilizarov circular fixator (ICF) involve dealing with uncertainties about a range of critical factors that control the mechanical microenvironment of the fracture site such as ICF configuration, fracture gap size, physiological loading etc. To date, the effects of the uncertainties about these critical factors on the mechanical microenvironment of the fracture site have not been fully understood. The purpose of this study is to tackle this challenge by using computational modelling in conjunction with engineering reliability analysis. Particularly, the effects of uncertainties in fracture gap size (GS), level of weight-bearing (P), ICF wire pretension (T) and wire diameter (WD) on the fracture site mechanical microenvironment at the beginning of the reparative phase of healing was investigated in this study. The results show that the mechanical microenvironment of fracture site stabilised with ICF is very sensitive to the uncertainties in P and GS. For example, an increase in the coefficient of variation of P (COV_P ) from 0.1 to 0.9 (i.e., an increase in the uncertainty in P) could reduce the probability of achieving a favourable mechanical microenvironment within the fracture site (i.e., Probability of Success, PoS) by more than 50%, while an increase in the coefficient of variation of GS (COV_GS ) from 0.1 to 0.9 could decrease PoS by around 30%. In contrast, an increase in the uncertainties in T and WD (COV increase from 0.1 to 0.9) has little influence on the fracture site mechanical microenvironment (PoS changes <5%).

Optimal time-dependent levels of weight-bearing for bone fracture healing under Ilizarov circular fixators

It is known that weight-bearing exercises under Ilizarov circular fixators (ICF) could enhance bone fracture healing by mechano-regulation. However, interfragmentary movements at the fracture site induced by weight-bearing may inhibit angiogenesis and ultimately delay the healing process. To tackle this challenge, a computational model is presented in this study which considers the spatial and temporal changes in mechanical properties of fracture callus to predict optimal levels of weight-bearing during fracture healing under ICF. The study takes sheep fractures as example and shows that the developed model has the capability of predicting patient specific, time-dependent optimal levels of weight-bearing which enhances mechano-regulation mediated healing without hindering the angiogenesis process. The results demonstrate that allowable level of weight-bearing and timings depend on fracture gap size. For normal body weights (BW) and moderate fracture gap sizes (e.g. 3 mm), weight-bearing with 30% BW could start by week 4 post-operation and gradually increase to 100% BW by week 11. In contrast, for relatively large fracture gap sizes (i.e. 6 mm), weight-bearing is recommended to commence in later stages of healing (e.g. week 11 post-operation). Furthermore, increasing ICF stiffness (e.g. using half pins instead of pretension wires) can increase the level of weight-bearing significantly in the early stages up to a certain time point (e.g. week 8 post-operation) beyond which no noticeable benefits could be achieved. The findings of this study have potential applications in designing post-operative weight bearing exercises.

Surgical treatment for patients with hemophilic pseudotumor-related femoral fracture: a retrospective study

BACKGROUND

Hemophilic pseudotumor (HPT)-related fracture is a rare but severe complication in patients with HPTs. These fractures often occur in femurs. There is no consensus on the standard surgical protocol for HPT-related femoral fracture. The present retrospective study evaluated the outcomes of these patients treated with surgical interventions.

METHODS

Ten patients with HPT-related femoral fractures who were treated with 14 surgical procedures due to 11 fractures in our hospital from January 2014 to April 2020 were evaluated retrospectively. Demographic data, fracture location, complications after surgery, and follow-up outcomes were recorded and analyzed. The mean follow-up period was 39.7 months.

RESULTS

The mean age at surgery was 31 years. Closed reduction external fixation (CREF) was originally performed in 2 patients, open reduction internal fixation (ORIF) was performed in 4 patients, screw fixation alone was performed in 1 patient, brace immobilization was performed in 1 patient, and amputation was performed in 3 patients. Bone union was observed in 5 patients, and an adequate callus was visible in 2 patients. Both patients with CREF had pin infections. Nonunion combined with external fixation (EF) failure occurred in 1 patient, and the plate was broken after ORIF. Three patients underwent autogenous or allogeneic cortical strut grafting. Three patients had HPT recurrence.

CONCLUSIONS

It is necessary to perform surgery in patients with HPT-related femoral fractures. Surgical treatments must consider fracture stabilization and HPT resection. Internal fixation is preferable, and EF should only be used for temporary fixation. If the HPT erodes more than one third of the bone diameter, strut grafts are necessary for mechanical stability. Amputation is an appropriate curative method in certain situations.

Finite Element Analysis of a Controlled Dynamization Device for External Circular Fixation

Objective  To virtually prototype a device for external circular fixation of long bone fractures with controlled dynamization made of two different materials and predict their mechanical behavior by using the finite element analysis (FEA) method. Method  A software was used for 3D modeling two metal parts closely attached by a sliding dovetail joint and a high-density silicone damper. Distinctive FEAs were simulated by considering two different materials (stainless steel or titanium), modes (locked or dynamized) and loading conditions (static/point or dynamic/0.5 sec) with uniform 150 kg axial load on top of the device. Results  The finite elements (FEs) model presented 81,872 nodes and 45,922 elements. Considering stainless steel, the maximum stress peak (140.98 MPa) was reached with the device locked under static loading, while the greatest displacement (2.415 × 10 ^-3 mm) was observed with the device locked and under dynamic loading. Regarding titanium, the device presented the maximum stress peak (141.45 MPa) under static loading and with the device locked, while the greatest displacement (3.975 × 10 ^-3 mm) was found with the device locked and under dynamic loading. Conclusion  The prototyped device played the role of stress support with acceptable deformation in both locked and dynamized modes and may be fabricated with both stainless steel and titanium.

Management of Failed External Fixation by Two-Staged Internal Osteosynthesis in the Lower Limb

Objective

This study aims to evaluate the result of a two‐stage (delayed conversion) management of nonunion after failed external fixation of the lower limb.

Methods

A case series of 25 patients (19 males and six females) enrolled in this study between February 2008 and October 2016, mean age 33.4 years (range, 22–65 years). Eight had femoral fractures, and 17 had tibial fractures. All were due to high‐energy trauma and were open fractures. All cases were presented by non‐union after external fixation in the lower limb long bones. All patients were managed by two stages (delayed conversion) osteosynthesis. The patients have been assessed for rate and time for union, range of motion of adjacent joints, the Modified functional outcome score of Karlstrom‐Olerud, and Trauma outcomes measure score.

Results

The mean follow‐up was 36.5 months (range 24–54 months). Twenty‐two cases (88%) were fully united on an average of 5.3 months. According to the Karlstrom‐Olerud scores, the final functional outcome score was excellent 12 cases, good 9 cases, accepted 2 cases, and poor in two cases. As regards the trauma outcome measure score, the mean TOM after 3 months was 26.1 (25.3–27.3), 30.4 (29.3–32.1) after 12 months, and 33.4 (32.3–40) after 24 months.

Conclusions

The technique of two‐stage treatment of nonunions of long bone after external fixation is a successful tool to achieve bony union. It could be a favorable option with a low risk of complications and a high level of functional outcomes.

Is Definitive Plate Fixation Overlap With External Fixator Pin Sites a Risk Factor for Infection in Pilon Fractures?

OBJECTIVES

To determine if overlap of definitive plate fixation with external fixator pin sites is a risk factor for infection in pilon fractures.

DESIGN

Retrospective cohort.

SETTING

Level 1 trauma center.

PATIENTS

One hundred forty-six patients with pilon fractures treated between 2012 and 2018.

INTERVENTION

Staged treatment with ankle-spanning external fixation, followed by delayed open reduction and internal fixation.

MAIN OUTCOME MEASURES

Demographic, radiographic, and operative data were reviewed, and the distance between the temporary external fixator pin sites and the definitive plate was measured. The primary outcome measure was the development of a deep postoperative infection.

RESULTS

Overall, 22 (15%) patients developed deep wound infections. Overlap of definitive plate and external fixation pin site occurred in 58 (40%) of ankles. Of these, 7 (12%) developed deep wound infection compared with 15 (17%) patients without overlap (P = 0.484). There was no significant difference in amount of overlap (P = 0.636) or distance from plate to pin site (P = 0.607) in patients with and without deep infection. Of the patients with deep infection, 11 (50%) occurred in patients with open fractures.

CONCLUSIONS

Overlap of definitive plate fixation with primary spanning external fixator pin sites is not a risk factor for development of deep infection in a staged treatment of high-energy pilon fractures.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Influence of Different Connecting Rod Configurations on the Stability of the Ilizarov/TSF Frame: A Biomechanical Study

Aim

The Ilizarov external fixator (IEF) is frequently used in trauma and elective orthopaedics. Many of its biomechanical variables (ring size, wire diameter, wire number, half pins vs wires, etc.) and their influence on stability and stiffness have been investigated. There is, however, a paucity in the literature regarding the influence of the connecting rod numbers and configurations between the rings on IEF stability. The primary aim of this biomechanical study was to compare the stability between four- and three-rod IEF configurations. Secondarily to assess the difference in stability between symmetrical and asymmetrical spacing of the IEF rods.

Materials and methods

A custom jig was designed to facilitate mounting of a basic two-ring IEF in a hydraulic press. Controlled centre and off-centre (thus simulated bending) axial loading was then applied across the frame. The configurations were loaded up to 4,000 N. The frame deformation was plotted and the data were then analysed and interpreted.

Results

Negligible differences were observed between different four- and three-rod configurations as long as the applied force at the loading point (LP) was within the area of support (AOS) created by the rods. The different four-rod constructs were always more stable than the three-rod constructs during bending.

Conclusion

There is comparable stiffness between a four-rod and a three-rod IEF construct as long as the LP is within the AOS created by the rods. A four-rod IEF is stiffer than a three-rod IEF in bending.

Clinical significance

This study will possibly change some paradigms regarding the planning and application of IEFs by Orthopaedics Traumatologists and Reconstruction Surgeons.

How to cite this article

Thiart G, Herbert C, Sivarasu S, et al. Influence of Different Connecting Rod Configurations on the Stability of the Ilizarov/TSF Frame: A Biomechanical Study. Strategies Trauma Limb Reconstr 2020;15(1):23–27.

Adjustable bone plate: state of art

Background/aim

The success of treatment of bone fracture and defects are based on a proper contact and compression between the bone fracture fragments. Intraoperative manipulations such as bone compression or distractions are generally done in order to achieve this. However, none of the bone plates currently in routine use allow these manipulations after fixation to the bone, requiring refixation and repeated drilling, and screwing operations. Based on this shortcoming, we designed a novel adjustable bone plate (ABP) system which allows bone shortening and lengthening even after fixation to the bone surface. The aim of the paper is to clarify the unique properties of the novel bone plate.

Materials and methods

In this paper, the new generation adjustable bone plate applicability, design, indication, and new characteristics in addition to conventional bone plates with review of the literature were discussed and surgical technique was demonstrated in a saw bone model.

Results

This novel design allows for compression and distraction at the fracture ends post fixation as well as bone segment transfers.

Conclusions

The potential of the new generation ABP plate for use in bone compression, distraction, and the segmental bone transfer is a promising invention for clinical applications in the future.

A finite element study: Finding the best configuration between unilateral, hybrid, and ilizarov in terms of biomechanical point of view

In an open fracture, the external fixator is one of the definitive treatment options as it could provide the initial stabilisation of the fractured bone. Limited literature discussing on the biomechanical stability between unilateral, hybrid and Ilizarov configurations, principally in treating a femoral fracture. Thus, this study aims to analyse the biomechanical stability of different external fixators via the finite element method (FEM). The present study portrays that different configurations of fixators possess different biomechanical stability, hence leading to different healing rates and complication risks. For the methodology, three-dimensional models of three different external fixators were reconstructed where axial loads were applied on the proximal end of the femur, simulating the stance phase. From the results, the unilateral configuration provides better stability compared to the hybrid and Ilizarov, where it displaced the least with an average percentage difference of 50% for the fixator's frame and 23% for the bone. The unilateral configuration also produced the least interfragmentary movement (0.48 mm) as compared to hybrid (0.62 mm) and Ilizarov (0.61 mm) configurations. Besides, the strain and stress of the unilateral configuration were superior in terms of stability compared to the other two configurations. As a conclusion, the unilateral configuration had the best biomechanical stability as it was able to assist the bone healing process as well as minimising the risk of pin tract infection while treating a femoral fracture.

Low cost 3D printed clamps for external fixator for developing countries: a biomechanical study

BACKGROUND

External fixation is a mainstream limb reconstruction technique, most often used after a traumatic injury. Due to the high rates of trauma in developing countries, external fixation devices are often utilized for immediate fracture stabilization and soft tissue repair. Proper external fixation treatment too often still fails to be adopted in these regions due to the high cost and trauma complexity. A novel, inexpensive, unilateral fixator was constructed using 3D printed clamps and other readily available supporting components. ASTM standard F1541 tests were used to assess the biomechanical properties of this novel external fixator.

METHODS

Applicable sections of ASTM standard F1541 were used to determine the biomechanical properties of the novel external fixator. 3D printed clamps modeled using SolidWorks and printed with chopped carbon fibers using a fuse deposition modeling (FDM) based 3D printer by Markforged (Boston, MA) were used. This study included 3 different testing configurations: axial compression, anterior-posterior (AP) bending, and medial-lateral (ML) bending. Using the novel unilateral fixator with 3D printed clamps previously sterilized by autoclave, an input load was applied at a rate of 20 N/s, starting at 0 N via a hydraulic MTS tester Model 359. Force and deformation data were collected at a sampling rate of 30 Hz. There was a load limit of 750 N, or until there was a maximum vertical deformation of 6 mm. Also, 4 key dimensions of the 3D printed clamps were measured pre and post autoclave: diameter, width, height and length.

RESULTS

The novel external fixator had axial compression, AP and ML bending rigidities of 246.12 N/mm (σ = 8.87 N/mm), 35.98 N/mm (σ = 2.11 N/mm) and 39.60 N/mm (σ =2.60 N/mm), respectively. The 3D printed clamps shrunk unproportionally due to the autoclaving process, with the diameter, width, height and length dimensions shrinking by 2.6%, 0.2%, 1.7% and 0.3%, respectively.

CONCLUSION

Overall, the biomechanical properties of the novel fixator with 3D printed clamps assessed in this study were comparable to external fixators that are currently being used in clinical settings. While the biomechanics were comparable, the low cost and readily available components of this design meets the need for low cost external fixators in developing countries that current clinical options could not satisfy. However, further verification and validation routines to determine efficacy and safety must be conducted before this novel fixator can be clinically deployed. Also, the material composition allowed for the clamps to maintain the appropriate shape with minimal dimensional shrinkage that can be accounted for in clamp design.

A case report of early unilateral external fixation by 3D printing and computer-assisted and secondary bone graft internal fixation in pseudarthrosis of the tibia surgery

Congenital pseudarthrosis of the tibia (CPT) is a rare congenital malformation. It is characterized by a tibial anterior bowing deformity or specific types of non-union, which typically result from abnormal development of the tibia, leading to the formation of local pseudarthrosis. The treatment of CPT is very challenging. The advent of 3D printing and computer-assisted techniques in recent years has provided a new ancillary technique for treatment planning and implementation. This case report describes the successful surgical treatment of a 14-year-old male that presented with a shortened limb deformity. Ahead of elective surgery, 3D printing and computer-assisted techniques were used to provide a 1:1 model of his left tibia, fibula and ankle joint to precisely determine the surgical procedure. The first surgery did not result in complete calcification of the tibial extension area, so a second proximal tibia iliac bone graft and internal fixation surgery was undertaken. Following regular follow-up and rehabilitation, by the 18-month follow-up, the proximal tibial bone graft had healed and the patient had resumed walking with a normal gait. This case report describes in detail the successful use of unilateral external fixation using the Ilizarov technique, 3D printing and computer-assisted orthopaedic surgery in the planning of treatment for CPT.

Clinical outcomes of revision with retrograde intermedullary nailing for failed plating of distal femoral fractures: a retrospective study

PURPOSE

To assess the feasibility and effectiveness of retrograde intramedullary nail (RIN) revision surgeries for locking compression plate (LCP) failure in distal femoral fractures.

METHODS

This retrospective study included 13 patients who suffered from metalwork failures after they initially underwent open reduction and LCP fixation. In patients who eventually underwent RIN revision from January 2014 to December 2016, range of motion (ROM) and Hospital for Special Surgery (HSS) scores obtained before surgery and at the final follow-up time were analysed.

RESULTS

The average operative time was 155 minutes (range, 120-210 minutes), and the average blood loss volume was 650 ml (range, 200-1350 ml). There were two cases of complications (15.38%): one was calf muscle vein thrombosis, and the other was a superficial infection. No deep tissue infection or deep vein thrombosis was observed post-operatively. The average follow-up time was 16 months (range, 12-24 months). All fractures healed in a mean of 6.5 months (range, 4-12 months), and one patient underwent an additional bone graft surgery that did not involve a bone graft during the RIN revision operation (this eventually healed at 12 months post-operatively). The mean ROM before the operation was 86.92 ± 12.34°. At the final follow-up, the mean ROM was 112.69 ± 9.27°. There was a significant difference between pre-operative and post-operative ROM (P < 0.01). The mean HSS score improved significantly from 38.85 ± 9.62 points pre-operatively to 79.62 ± 5.42 points post-operatively. There was a significant difference between pre-operative and post-operative HSS scores (P < 0.01).

CONCLUSIONS

RIN revision surgery achieved excellent clinical results in patients with LCP failure.

Post-operative outcomes of open reduction and internal fixation versus circular external fixation in treatment of tibial plafond fractures: A systematic review and meta-analysis

INTRODUCTION

Tibial plafond fractures (TPF) are complex injuries often resulting in poor outcomes. Combination of articular impaction, metaphysealcomminution and soft-tissue injury results in a significant treatment challenge. The aim of this study was to conduct a systematic review and meta-analysis to compare post-operative complications and functional outcomes of open reduction and internal fixation (ORIF) versus circular external fixation (CEF) for treatment of TPF.

METHODS

A comprehensive search of PubMed/MEDLINE, Embase, Scopus and Cochrane library was undertaken. All studies published in English language comparing ORIF with CEF for treatment of TPF were included.

RESULTS

5 comparative studies with 239 fractures met the inclusion criteria. Meta-analysis showed no significant difference in rates of non-union, malunion, superficial infection, deep infection, and secondary arthrodesis between the two treatment groups. Significantly higher rate of unplanned metalwork removal (RR 5.68, 95% CI 1.13 to 28.55, p = 0.04) and lower rate of post-traumatic arthritis (RR 0.48, 95% CI 0.30 to 0.78, p = 0.003) were found in patients that underwent ORIF. 1 study showed significantly lower functional outcomes scores with CEF (p< 0.05), whereas 3 studies found comparable functional outcomes between the two treatment groups. Overall, there was a preference in treating more severe injuries with CEF.

CONCLUSION

CEF and ORIF are both acceptable treatment options for surgical management of TPF, with comparable post-operative complication rates and functional outcomes. This study highlights paucity of high-quality evidence regarding the optimal fixation method for TPF.

The Anatomy of the Tibial Nutrient Artery Canal-An Investigation of 106 Patients Using Multi-Detector Computed Tomography

Radiologic evaluation of the tibial nutrient artery is clinically important as disruption of tibial blood supply is a risk factor for delayed or non-union of tibial fractures. Damage to the tibial nutrient artery canal (TNAC) may occur by a traversing fracture or iatrogenic cause in the context of pin/screw placement. Furthermore, TNAC could be misdiagnosed as a stress fracture. The aim of this study was to characterize the normal anatomy of TNAC and to delineate its gender and side-specific differences. Patients who underwent contrast-enhanced computed-tomography encompassing the pelvis and lower extremities were included. TNAC was identified with an external and internal foramen and a traversing intercortical canal. Various anatomical morphometrics were evaluated: total number of nutrient canals, angular position of the outer and inner nutrient foramina, absolute and relative position of the nutrient foramina, as well as the intercortical canal length with respect to tibial length. The majority of patients of both genders had only one tibial nutrient canal, multiple canals or complete absence were rare. In most cases, the outer nutrient foramen was found on the posterolateral aspect of the upper-third of tibia at about 32% of tibial length; the inner foramen was found at the middle third of the tibia (41% of tibial length). The course of nutrient canal was mostly cranio-caudal with a small, but significant difference in relative canal length: 8.5% vs. 10% of tibial length for females and males, respectively. The angular location of the outer and inner foramen was between 20–30° and did not reveal a statistically significant difference between genders. No statistically significant side specific differences were found for all analyzed parameters and both genders. The clinical relevance of this anatomical study pertains to establishing “safe corridors” of pin/screw insertion in the context of surgical management of tibial fractures in order to avoid iatrogenic disruption of tibial blood supply.

External fixators: looking beyond the hardware maze

External fixation has a wide variety of orthopedic applications. Although external fixator frames may have a complex appearance, these constructs are formed from several basic components and can be broadly categorized into unilateral, circular, or hybrid designs. The introduction of computer-aided circular external fixation devices (hexapod frames) has simplified the treatment of multiaxial and especially rotational deformities. Serial radiography plays a central role in the evaluation of callus formation (at the level of treated fracture or nonunion as well as the regenerate and docking site with distraction osteogenesis), tailoring the rate and rhythm of distraction during distraction osteogenesis, evaluation of frame complications, and determination of the timing of frame removal. The goals of this article are to review: the components, types, and relevant terminology of external fixator constructs with special emphasis on the Taylor spatial frame, the principles and techniques of distraction osteogenesis, and complications of external fixation.

Reducing the Risk of Ring Breakage in Taylor Spatial Frames: The Effect of Frame Configuration on Strain at the Half-ring Junction

Aim

We have encountered four cases with Taylor spatial frames (TSF) (Smith & Nephew, Memphis, TN, USA) with breakage at the half-ring junction of the distal ring. This study examines the strain produced on different locations of the distal ring during loading and the effects on the strain of altering the frame construct.

Materials and methods

We mounted two ring TSF constructs on tibia saw bone models. The proximal ring was the same in all constructs and consisted of a 2/3 180 mm ring attached with three wires. Construct 1 is reproducing the configuration of cases where failure was seen. The distal 155 mm ring is attached with three half pins. The half-ring junction is located in the midline. Construct 2 has a different half pin placement and an additional wire on the distal ring. Constructs 3 and 4 have the same half pin configuration to construct 1 but the distal ring is rotated 60° internally and externally, respectively. Strain gauges were attached to different locations and measurements recorded during loading. Statistical analysis was performed.

Results

Highest strain values were recorded at the half-ring junction of constructs 1 and 2 (>600 microstrains (με) in tension). Rotating the ring 60° internally significantly reduces the strain at the half-ring junction (<300 με) whilst external rotation by 60° further reduces the strain (<180 με). Ring strain is higher in areas close to half pin attachments.

Conclusion

The highest strain is in the half-ring junction as the half rings are subjected to different loading modes. The thickness of the half-ring is halved and the second moment of area reduced further increasing breakage risk. Placing this junction close to the half pin–frame interface, as dictated by the anatomical safe zone further increases the strain. Rotating the distal ring 60° significantly reduces the strain at the half-ring junction.

Clinical significance

Ring breakage is a rare but significant complication. This is the first study to address this potential mode of TSF failure. Insights and technical tips from this study can help reduce this.

How to cite this article

Iliadis AD, Bebja R, Wang K, et al. Reducing the Risk of Ring Breakage in Taylor Spatial Frames: The Effect of Frame Configuration on Strain at the Half-ring Junction. Strategies Trauma Limb Reconstr 2020;15(3):146–150.

The Effect of External Fixator Configurations on the Dynamic Compression Load: An Experimental and Numerical Study

(1) Objective: External fixation systems are commonly used by surgeons to ensure stabilization and consolidation of bone fractures, especially in patients who are at high risk for systematic complications. Both rigid and elastic external fixations are important in the fracture healing process. This study aims to evaluate the behavior of the Orthofix Limb Reconstruction System (LRS)® in the dynamic compression mode. (2) Methods: Experimental and numerical setups were developed using a simplified model of a human tibia which consisted of a nylon bar with a diameter of 30 mm. The bone callus was included in both setups by means of a load cell-based system, which consisted of two carbon epoxy laminated composite plates with a final stiffness of 220 N/mm. The system was evaluated experimentally and numerically, considering different numbers of pins and comparing distances between the external fixator frame and the bone, achieving a good correlation between experimental and numerical results. (3) Results: The results identified and quantified the percental load transferred to the fracture and its sensibility to the distance between the external fixator and bone. Additionally, LRS locking stiffness was evaluated which resulted from the clamp-rail clearances. The results show that the blocking effects of the free clamp movement are directly related to the fixator configuration and are responsible for changes in the amount of load that crosses the bone callus. (4) Conclusions: From the biomechanical point of view, the results suggest that the average bending span of Schanz pins and the weights of the patients should be included into clinical studies of external fixators comparisons purpose.

Leeds-Genoa Non-Union Index: a clinical tool for asessing the need for early intervention after long bone fracture fixation

AIM OF THE STUDY

The aim of this case-control study was to develop a clinical decision rule to support assessment of the risk of long-bone non-union and plan for appropriate early intervention.

METHODS

Two hundred patients (100 cases and 100 controls) were recruited. Risk factors identified to contribute to the development of non-union were recorded and analysed with a multivariable logistic regression model. Tabulation of the outcome (non-union/union) against each risk factor in turn (univariable analysis) was carried out. Odds ratios and confidence intervals were derived using Wald's method. A receiver-operator curve was calculated and the area under the curve was computed. Having established the eight most important risk factors, a non-union risk index was developed as the count of the risk factors present in each patient.

RESULTS

The five risk factors for non-union with greater effect size were post-surgical fracture gap > 4 mm (odds ratio (OR) = 11.97 95% CI (4.27, 33.53)), infection superficial/deep (OR 10.16 (2.44, 42.36)), not optimum mechanical stability (OR 10.06 (3.75, 26.97)), displacement > 75% of shaft width (OR 6.81 (2.21, 20.95)), and site of fracture-tibia (OR 4.33 (1.32, 14.14)). The ROC curve for the non-union index was 0.924, sensitivity 91%, specificity 77%.

CONCLUSIONS

The non-union index derived from counting risk factors predicts union for 0-4 risk factors and non-union for 5-8 risk factors. It can be readily applied and can guide clinicians about the risk of development of long-bone non-union. It can become a powerful aid for assessing fracture fixation outcome and to support early intervention.