Circular External Fixator Research Articles

Biomechanical Optimization of a Novel Circular External Fixator (Optimization of Circular External Fixator)

The purpose of this study was to investigate biomechanical optimization of the newly designed circular external fixator (CEF) system, used in the orthopaedics surgery, that is capable of continuous compression at the fracture line. External fixators are devices applied from outside the body to treat bone and joint injuries as well as to correct skeletal deformities. In this study, the effects of parametric changes on CEF mounted for the fracture were investigated with using response surface optimization (RSO) module in ANSYS software using the finite element method. The pressure acting on fracture line is an essential factor on fracture healing. The RSO module showed that the contribution of the parameters on this essential factor was as follows in the descending order; pre-load, spring coefficient, wire diameter and angle between the wires. According to the results of the numerical study; (a) there was a positive correlation between the wire diameter and the normal stress at the fracture line. The increase in wire diameter and pre-loading caused an increase in the normal stress at the fracture line. (b) The angle between the wires has a relatively little effect on the whole system. (c) The most effective parameters on the system were determined as the pre-loading and spring coefficient.

Indications and postoperative complications of tibial Illizarov’s technique in a tertiary care center, Saudi Arabia

Background: Circular external fixation including Ilizarov method is a well-established technique often practiced in orthopedic surgery. The goal of this procedures is to lengthen extremity bones, reconstruct severely injured or fractured bone trauma, correct congenital bone deformities, treat infected bones and to treat pseudarthrosis. The importance of this study is that it will highlight the most common complications for this procedure in order to reverse them and have a better clinical outcome. The aim of this study is to assess the indications and postoperative complication rates following tibial circular external by Illizarov's method. Methods: We performed a consecutive case series, chart review study of 33 patients who were treated with the Ilizarov method, between 2010 and 2016. All patients who underwent tibial circular external fixators using Ilizarov method were selected for this study. There were 25 males and 8 females, mean age was 31.06 (range 14 -71). All data collected was coded in Excel sheet. SPSS package version 20 was used for data analysis. Results: The total number of subjects involved in this study was 33 subjects (Male: 25[75%]-Female: 8[25%]). The average age of the subjects was 31.06 (range 14 -71) with a standard deviation of +/-13.8. Overall, 63.6% of patients reported post-op complications. Whereas 36.3% of patients were free of complications. The main complication was pain which was reported in 15% of the subjects. Conclusion: There was a minimal complication rate associated with this technique in our institution compared to published studies. Several medical conditions were the indication for this procedure, primarily motor vehicle accidents deformities.

Does the Surgical Correction of Tibial Torsion with Genu Varum Produce Outcomes Similar to Those in Varus Correction Alone?

The aim of this article is to study the relationship between tibia vara and external tibial torsion in adults. The following questions were asked: (1) what is the incidence of rotational deformity in patients with genu varum and (2) do patients who undergo correction of tibial torsion with genu varum have similar outcomes to those who undergo simple tibia vara correction? In this study, 69 patients (138 limbs) underwent bilateral proximal tibial osteotomy for the correction of genu varum. Patients with simple coronal plane deformity (varus alone) were treated with either a monolateral external fixator or a hexapod frame. Those with concomitant external tibial torsion were treated with circular external fixation. The primary outcome was the ability to achieve the desired correction of alignment in the coronal, sagittal, and axial planes. Secondary outcomes included a postoperative Knee Injury and Osteoarthritis Outcome Score (KOOS) and a routine patient satisfaction questionnaire. The incidence of tibial torsion among the entire group of patients with bilateral tibia vara was 46% and overwhelmingly external in direction. The two groups had some significant differences in demographics with torsion patients tending to be younger and thinner. The final mechanical axis deviation and medial proximal tibial angle values for both groups did not differ significantly (p = 0.956). The postcorrection thigh-foot axis was not significantly different between the two groups (p = 0.666). Time to union was not significant (p > 0.999). KOOS was not different between the two groups in symptoms, pain, activities of daily living, and return to sport. There was a difference in the quality of life score between the two groups (p = 0.044). There was no difference between the two groups regarding the patient questionnaire. Based on the finding of this analysis, the incidence of rotational malalignment with genu varum is close to 50%. The recognition of this close association with external tibial torsion deformity may allow for further insights into the role of rotation in varus deformity-related knee pathology and treatment. Patients can expect nearly identical outcomes from this surgery.

Circular hexapod external fixation for periprosthetic tibial fracture.

A poor soft tissue envelope often accompanies periprosthetic tibia fracture around a well-fixed total knee arthroplasty and the tibial stem leaves little room for screw fixation. This article describes the practicability and effectiveness of a novel surgical technique using circular hexapod external fixation, in patients with this clinical scenario. It was applied for fixation of periprosthetic tibia fracture in 2 patients. Contact between the external fixation pins and the prosthesis was avoided. Using a web-based software program, a gradual reduction in all planes was achieved. Adequate fixation, stability, reduction, and quick healing were obtained in the 2 cases, with minimal complications. The patients returned to their activity level a few months after external fixation removal.

In this issue – May 2017

In this issue – May 2017

Radius and ulna fracture repair with the IMEX miniature circular external skeletal fixation system in 37 small and toy breed dogs: A retrospective study.

To determine outcome and prognostic factors after radius and ulna fracture repair with a modified IMEX miniature circular external skeletal fixation (MCESF) in small and toy breed dogs. Retrospective study. Thirty-seven young small and toy breed dogs with 41 radial and ulnar fractures. Records of radial and ulnar fractures repaired with a modified IMEX MCESF were reviewed. Constructs included 3-4 complete rings, 2 threaded rods, 4 mm-diameter nuts and 6-8 transfixation wires. MCESF configuration, type of fracture reduction, dynamization of the apparatus, inclusion of a dowel pin, and implantation of allograft were recorded. Outcome measures included complications, limb alignment, time to clinical union, and functional outcomes, scored as excellent, good, fair, or poor. Radiographic union was achieved in 40/41 fractures. Fractures reached bony union within 33-84 days after repair. Time to union was not influenced by the type of fracture reduction (P = .11), use of a dowel pin (P = .099), or implantation of an allograft (P = .45). Fracture dynamization delayed radiographic union (P = .0005). At implant removal, mean frontal (FPA) and mean sagittal plane alignments (SPA) were 7.9° ± 6.5° and 7.5° ± 5.8°, respectively. Limb alignment did not differ between radiographs obtained immediately after surgery and those obtained at time of radiographic union in the frontal (P = .062) or sagittal (P = .14) planes. Ninety-five percent of cases had good-to-excellent outcomes, based on return to function at final re-evaluations. This modified IMEX MCESF construct provided an effective alternative to treat young small and toy breed dogs with radius and ulna fractures.

The “Road to Union” protocol for the reconstruction of isolated complex high-energy tibial trauma

IntroductionThe purpose of this study was to describe a standardized staged approach, “The Road to Union”, for the reconstruction of isolated complex tibial trauma, both acute and chronic in nature. MethodsThis retrospective study included all patients treated for complex tibial trauma at a specialized limb reconstruction centre, including acute open fracture as well as infected and aseptic non-unions. This standardized approach includes eight specific steps, employed in sequence. The time in external fixation (EFT), the external fixation index (EFI), and the distraction consolidation index (DCI) were the primary outcome measures. The relationship between EFI and DCI was assessed using Pearson’s moment correlations. ResultsThirty-two patients with a mean age of 34.7±14.2years were included; 12 were treated for complex open tibial fractures with bone loss, 13 for infected non-unions, and 6 for aseptic non-union. The mean bone defect was 66±32mm. The total EFT was 42.5±14.8 weeks; the EFI measured 51.9±25.3 days/cm, and the DCI measured 48.3±21.4 days/cm. Union was achieved in 29 out of 32 patients (91%), and there was a strong and significant relationship between EFI and DCI (r=0.92, p=0.0001) measurements. Pin site infections were observed in 11 patients, and 3 patients had persistent non-union. Three patients underwent delayed amputations when reconstructive procedures were unable to achieve union. ConclusionThe findings of this study demonstrate that a standardized staged treatment protocol of debridement, circular external fixation, soft-tissue management, distraction osteogenesis, and functional rehabilitation can result in a high rate of union in cases of complex tibial trauma, both acute and chronic in nature. Level of evidenceLevel IV; case series

Tibia deformity correction by circular external fixator in multiple enchondromatosis

Objective To discuss the outcomes of tibia varum and shorting deformity correction by circular external fixator in multiple enchondromatosis. Methods Thirty-one tibias treated with varum and shorting deformity correction by circular external fixator in multiple enchondromatosis were statistically analyzed. Of 31 tibias (28 cases), 12 were from boys, and 19 from girls, with an average age of 12.3 years. After open tibia and fibula osteotomy through small incision, all tibia varum and shorting deformity were corrected slowly by circular external fixator. The patients were followed up for 1, 2, 3, 6, 12, 24 and 36 months after the operation. Preoperative and postoperative data at 12th and 36th month about tibia shorting deformity, angle of varus knee, medial proximal tibial angle, lateral distal tibial angle, the maximum length and width of the tumors which had been gone through by stainless steel needles were analyzed. Results As compared with the preoperative group whose tibia shorting deformity was (35.16±8.62) mm, postoperative tibia shorting deformity at 12th and 36th month was (16.04±2.73) mm and (6.99±1.93) mm respectively, the difference between the two groups had statistical significance (t=15.927, P=0.000; t=20.814, P=0.000). As compared with the preoperative group whose angle of varus knee was (25.0±7.9)°, postoperative angle of varus knee at 12th and 36th month was (2.1±0.9)° and (5.0±1.1)° respectively, the difference between the two groups had statistical significance (t=15.955, P=0.000; t=13.843, P=0.000). As compared with the preoperative group whose medial proximal tibial angle was (70.6±3.0)°, postoperative medial proximal tibial angle at 12th and 36 month was (88.7±1.6)° and (87.6±1.4)° respectively, the difference between the two groups had statistical significance (t=-26.806, P=0.000; t=-28.591, P=0.000). As compared with the preoperative group whose lateral distal tibial angle was (131.5±2.9)°, postoperative lateral distal tibial angle at 12th and 36th month was (88.9±1.9)° and (89.3±1.8)° respectively, the difference between the two groups had statistical significance (t=78.459, P=0.000; t=71.467, P=0.000). As compared with the preoperative group whose the maximum length of the tumors was (46.2±23.7) mm, postoperative maximum length of the tumors at 12th and 36th month was (47.2±24.0) mm and (46.6±24.1) mm respectively, the difference between the two groups had no statistical significance (t=-1.808, P=0.081; t=-0.741, P=0.464). As compared with the preoperative group whose maximum width of the tumors was (33.9±5.0) mm, postoperative the maximum width of the tumors at 12th and 36th month was (34.6±6.3) mm and (35.1±5.1) mm respectively, the difference between the two groups had no statistical significance (t=-1.014, P=0.319; t=-1.910, P=0.066). All patients were not diagnosed with osteomyelitis and had no symptoms of nerve and vascular injury. Conclusion It demonstrates that tibia deformity correction by circular external fixator in multiple enchondromatosis is safe and effective. Tumors being gone through by stainless steel needles have no growth rapidly in a short time. But the higher probability of malignant change is necessitating lifelong follow-up. Key words: Multiple enchondromatosis; Tibia; Circular external fixator

Mid-Term Results of Minimally Invasive Plate Osteosynthesis and Circular External Fixation in the Treatment of Complex Distal Tibia Fractures.

The treatment of pilon tibia fractures is challenging. Anatomical reduction of the joint surface is essential. Excessive soft-tissue dissection may interfere with the blood supply and can result in nonunion. We sought to compare the outcomes of distal tibia fractures treated with medial locking plates versus circular external fixators. We retrospectively evaluated 41 consecutive patients with closed pilon tibia fractures treated with either minimally invasive locking plate osteosynthesis (n = 21) or external fixation (EF) (n = 20). According to the Ruedi and Allgower classification, 23 fractures were type B and 18 were type C. Soft-tissue injury was evaluated according to the Oestern and Tscherne classification. Time to fracture union, complications, and functional outcomes were assessed annually for 3 years with the American Orthopaedic Foot and Ankle Society (AOFAS) ankle score. Mean ± SD values in the plate group were as follows: age, 42.4 ± 14 years; union time, 19.4 ± 2.89 weeks (range, 12-26 weeks); and AOFAS ankle scores, 86.4 ± 2.06, 79.5 ± 1.03, and 77.9 ± 0.80 at 1, 2, and 3 years, respectively. Four patients in the plate group needed secondary bone grafting during follow-up. In the EF group (mean ± SD age, 40.7 ± 12.3 years), all of the patients achieved union without secondary bone grafting at a mean ± SD of 22.1 ± 1.7 weeks (range, 18-24 weeks). In the EF group, mean ± SD AOFAS ankle scores were 86.6 ± 1.69, 82.1 ± 0.77, and 79.7 ± 1.06 at 1, 2, and 3 years, respectively. There were no major complications. However, there were soft-tissue infections over the medial malleolus in five patients in the plate group and grade 1-2 pin-tract infections in 13 patients and grade 3 pin-tract infections in one patient in the EF group. Post-traumatic arthritis was detected in eight plate group patients and seven EF group patients. Minimally invasive plating and circular EF methods have favorable union rates with fewer complications.

Correction of tibial malunion in a patient with ipsilateral total knee and ankle prostheses using external ring fixation and the ilizarov method

Total ankle replacement (TAR) aims at reestablishing a functional and painless ankle joint while maintaining motion and preventing adjacent joint arthritis. TAR can be complicated by comorbidities such as ipsilateral knee arthritis and deformity with subsequent arthroplasty and/or other lower extremity malalignment issues. We present a case of a 67-year-old female with severe right ankle pain and a history of ipsilateral subtalar and calcaneocuboid fusion, bilateral total knee arthroplasty, and a malunion of a conservatively treated ipsilateral segmental tibial fracture. Following TAR, there was recurrent lateral hindfoot pain due to subtle malalignment from the tibial malunion which resulted in persistent hindfoot valgus. This caused symptomatic subfibular impingement in addition to limb length discrepancy. To address that, a circular external fixator was applied to realign the ankle and lengthen the tibia, eliminating pain and avoiding complications with either implant.

Factors associated with treatment failure of aseptic tibial nonunions managed by circular external fixation

Background: Tibial nonunions pose significant treatment challenges despite the regularity with which they are encountered. While several studies have reported the outcome of treating different nonunion subtypes with various strategies, few have investigated the factors that influence treatment and outcome. Aims: This study aims to identify factors that complicate the management of uninfected tibial nonunions and are associated with failure of treatment. Materials and Methods: We retrospectively reviewed all patients with uninfected tibial nonunions who were treated according to a standardized treatment algorithm over a 5-year period. Results: The final cohort consisted of 84 patients with a mean age of 36.5 years (range 5–68 years). Bony union was achieved in 79 out of 84 (94%) tibias. Malalignment (P < 0.001), smoking (P = 0.008), alcohol use (P = 0.039), and time from injury to nonunion management (P = 0.003) were found to be associated with treatment failure. The factors found to be associated with increased treatment complexity were smoking (P = 0.035), alcohol use (P = 0.011), and time from injury to nonunion management (P < 0.001). Conclusion: General orthopedic surgeons should, therefore, refer these patients to reconstructive surgeons as soon as the diagnosis of a tibial nonunion is made while reconstructive surgeons should note the importance of host optimization and mechanical alignment during the management of these conditions.

Outcome of bilateral circular fixators in complex lower limb fractures

Circular external fixators are increasingly being used for complex lower limb trauma. When these injuries are sustained to both lower limbs, the ideal management is unclear. We present the results of 25 consecutive patients who were treated with bilateral circular external fixators for complex tibial trauma. The final cohort consisted of 23 men and two women with a mean age of 31.8 years (range 21-62 years) and a median follow-up was 16.4 months (range 6-37 months). Bony union was achieved in 96% (48 out of 50) of the tibia fractures. The mean time to union was 26 weeks (range 13-71 weeks). Serious complications included chronic osteomyelitis that developed in one patient following a high-grade open fracture and unilateral non-unions in two patients. Bilateral circular external fixators are a viable treatment option for patients who sustain bilateral complex lower limb trauma.

Monofocal distraction treatment of stiff aseptic tibial nonunions with hexapod circular external fixation

Background: Tibial nonunions remain a significant and challenging clinical problem. Nonunions occur due to a failure of biology, a failure of biomechanics, or both. The cells in and around the nonunion site have an osteogenic potential that can be activated when torsional, axial, and shearing instabilities are eliminated by establishment of an appropriate biomechanical milieu. Hexapod external fixators may be able to provide this milieu. Materials and Methods: In this retrospective study, consecutive patients with tibial nonunions treated in a single center were analyzed. They were all treated by the application of a hexapod circular fixator before deformity correction and distraction. This was followed by functional rehabilitation. We determined general health status with the use of the Short Form 12 measurement tool. Results: A total of 32 patients with 33 stiff hypertrophic nonunions were treated with circular fixators. The average age was 44 years, there were 24 males and 8 females. Out of the 33 nonunion cases, 29 united with closed distraction only; 3 required bone graft and 1 underwent amputation. The average time to union was 170 days. Overall on the final examination, all patients had a health status that was similar to the general population norm. Conclusion: A success rate in excess of 80% can be achieved with mechano-biological manipulation using hexapod external fixation in tibial nonunions without bone grafting.

Partial calcanectomy and Ilizarov external fixation may reduce amputation need in severe diabetic calcaneal ulcers.

ABSTRACT Objective: The treatment of diabetic hindfoot ulcers is a challenging problem. In addition to serial surgical debridements, hyperbaric oxygen therapy and local wound care play important roles in the surgeon’s armamentarium, for both superficial infection and gangrene of the soft tissue, often complicated by osteomyelitis of the calcaneus. The purpose of this study was to evaluate the results of an aggressive approach from diagnosis to treatment of calcaneal osteomyelitis in foot-threatening diabetic calcaneal ulcers. Methods: The study included 23 patients with diabetic hindfoot ulcers who were treated with radical excision of the necrotic tissue and application of circular external fixation. The treatment protocol was a combination of magnetic resonance imaging (MRI)-guided debridement of the necrotic tissues and application of an Ilizarov external fixator in plantarflexion to decrease the soft-tissue defect. Primary outcome measures were total cure of infection and obvious healing of the osteomyelitis at 12 weeks determined by MRI, and clinical cure through objective assessment of the appearance of the wound. Results: The wounds healed in 18 of the 23 patients (78%), partial recovery occurred and subsequent flap operation was performed in three patients (13%), and below-the-knee amputation was performed in two patients (9%). Conclusions: This surgical protocol is effective in ameliorating diabetic hindfoot ulcers with concomitant calcaneal osteomyelitis, and satisfactorily reduces the need for amputation.

Percutaneous osteoperiosteal decortication combined with distraction osteogenesis for treatment of nonunion of lower-extremity bones

Objective To evaluate the curative effects of percutaneous osteoperiosteal decortication combined with distraction osteogenesis for treatment of nonunion of lower-extremity bones. Methods A retrospective analysis was performed of the 32 patients who had been treated using osteoperiosteal decortication combined with distraction osteogenesis from September 2011 to December 2014 for nonunion of lower-extremity fractures. They were 23 males and 9 females, with a mean age of 33.4 years (range, from 15 to 62 years). After their former internal or external fixators were removed, the 2 fracture ends were fixated by a retractile monolateral or circular external fixator. Under radiographic monitoring, a percutaneous incision was made with a 5 mm sharp chisel, down to the bone. Scar and ossified tissue between the fracture ends were debrided and cut along the fracture line. After the marrow cavity was reamed, a new irregular wound was created at sclerotic fracture ends. Scale-shaped chips (1 mm thin and 5 mm in diameter) were elevated using a chisel on surface of the cortical bone within 2 cm from the fracture ends. The external fixators were adjusted to compress the fracture sites. On the 8th day after operation, the eternal fixators were applied to distract and compress at nonunion sites to stimulate the osteogenesis. Results All the patients were followed up for an average of 12.5 months (range, from 8 to 42 months). Primary union was successfully achieved in 28 patients while delayed union occurred in 3 patients who finally achieved union after adjuvant therapies like shock wave and or local injection of bone marrow blood. The average time for union was 4.6 months(range, from 4 to 7 months). The mean time for external fixation was 6.2 months (range, from 5 to 8 months). One patient encountered nonunion of lateral tibial cortical bone 6 months after surgery but eventually achieved union by au-tologous ilium grafting. Joint functions in all postoperative patients were similar to those before operation. Conclusion Percutaneous osteoperiosteal decortication combined with distraction osteogenesis is a simple, minimally invasive and effective treatment for nonunion of lower-extremity bones, avoiding disadvan-tages brought by traditional surgery, like massive trauma and excessive bleeding. Key words: Bone lengthening; Fractures, ununited; Surgical procedures, minimally invasive; Percutaneous decortication

Smoking cessation advice in limb reconstruction: An opportunity not to be missed

The adverse health effects of smoking are well known, including its effects on the musculoskeletal system. Limb reconstruction using external fixators is a high intensity process with high levels of patient contact time, complications and cost. The aim of this study was to examine smoking patterns in this group and in particular to assess trends in smoking cession.Data was collected from 41 patients all undergoing treatment using circular frame external fixation, for a variety of pathologies, most commonly acute tibial trauma. A patient reported questionnaire was used. Data was collected over a six-month period.In our population 56.1% of patients were smokers. During the study 47.8% patients stopped smoking and a further 39.1% decreased their smoking behaviour. 78.3% of patients could recall being given smoking cessation advice. In our group, 87% of patients were unaware of the effects of smoking on bone healing. Once made aware during discussion of proposed treatment, 73.9% stated that it was, in part, this knowledge that prompted them to positively change their smoking habits.The results of this study show that advice regarding smoking cessation during limb reconstruction treatment can potentially have a positive impact on patients smoking habits. The effect of smoking should be linked to the patient pathology and discussed during the consent process.Taking the time with the patient for this simple free intervention can have a positive impact on patient health, and potentially on the outcome of their current treatment, and is an opportunity not to be missed.

Cosmetic lengthening: what are the limits?

ObjectivesIn the last decades, limb lengthening has not been limited to the treatment of patients with dwarfism and deformities resulting from congenital anomalies, trauma, tumor and infections, but, has also been used for aesthetic reasons. Cosmetic lengthening by the Ilizarov method with circular external fixation has been applied to individuals with constitutional short stature who wish to be taller.Materials and methodsFrom January 1985 to December 2010, the medical records of 63 patients with constitutional short stature (36 M, 27F; 126 legs) who underwent cosmetic bilateral leg lengthening using a hybrid advanced fixator according to the Ilizarov method, were reviewed, retrospectively. The mean age was 24.8 years, while the mean preoperative height was 152.6 cm. Paley’s criteria were used to evaluate problems, obstacles, and complications from the time of surgery until 1 year after frame’s removal.ResultThe mean lengthening achieved in all patients was 7.2 cm (range: 5–11 cm), with a mean duration of treatment of 9 months and 15 days (range: 7–18 months). The mean follow-up time was 6.14 years (range 1–10).ConclusionThe cosmetic leg lengthening was helpful to all patients, improving their social capabilities and self-confidence. All patients considered their stature as normal and they reported satisfaction and gratification with important changes in their professional and personal life. Cosmetic leg lengthening may raise some ethical objections and for that reason patients should be well informed about all the risks and complications related to this type of surgery.

Knee arthrodesis by the Ilizarov method in the treatment of total knee arthroplasty failure

BackgroundCurrently, the main indication for knee arthrodesis is septic failure of a total knee arthroplasty (TKA). The purpose of this study was to evaluate the results of knee arthrodesis by circular external fixation performed in the treatment of TKA failure in which revision arthroplasty was not indicated. MethodsThe study involved 19 patients who underwent knee arthrodesis by the Ilizarov method. Clinical and functional assessments were performed, including Knee Society Score (KSS). A postoperative clinical and radiographic evaluation was conducted every three months until the end of the treatment. Postoperative complications and eventual leg shortening were recorded. ResultsKSS results showed a significant improvement with respect to the preoperative condition. Of the 16 patients in the final follow-up, 15 patients (93.7%) achieved complete bone fusion. Major complications occurred in patients treated for septic failure of TKA and most occurred in patients over 75years of age; the mean final leg shortening was four centimeters. ConclusionIn our experience, the Ilizarov method is effective for performing a knee arthrodesis in the case of extensive bone loss. At the same time, it is possible to correct the associated leg deformities or limb length difference. In addition, only the Ilizarov method provides a mechanical stimulus for bone formation and improves the quality of the bone and of the microcirculation, which enhances the host response against infection. Despite these attributes, knee arthrodesis by the Ilizarov method must be considered a ‘salvage procedure’ in cases of severe outcomes from knee surgery in which revision arthroplasty is not indicated.

Definitive Management of Distal Tibia and Simple Plafond Fractures With Circular External Fixation.

Obtaining optimal results in the treatment of extraarticular distal tibia fractures can be challenging. Plate and screw and intramedullary fixation have proven to be effective treatments, but are associated with significant complication rates when used for open fractures and patient with severe medical comorbidities. External fixation is a third alternative that is less often employed, but provides a very effective means of treatment. Circular external fixation offers great flexibility in obtaining anatomic alignment and stable fixation for even the most challenging distal tibia fractures. In addition, it provides advantages in limiting the risk of deep infection, dealing with bone loss, and obtaining soft tissue coverage. The greater ease of treatment and potential economic advantage in patient cohorts with low complication rates, such as closed fractures, supports the preferential use of internal fixation. However, circular external fixation may be the preferred treatment for patients with higher-grade open fractures, a poor soft tissue envelope with limited fixation options distally, and major comorbidities (diabetes, immune deficiency) with an associated high risk of complications.

Clamping of fine Kirschner wires in external fixators

In Ilizarov circular (ring) external fixators, fine Kirschner wires are used to fix the bone to the fixator. Clamping of the wires to the rings with different bolt torques has been studied. However, the relation between the bolt torque and the fixation load applied to the wire was not investigated. In this work, finite element method is used to address this problem. Here, a fully three-dimensional model of the wire fixation assembly was built, with geometric details like threads on the bolt to produce a realistic simulation of the clamping of the wire. Both cannulated and slotted bolt types were studied and values of 0.2, 0.25, 0.3 and 0.45 were used for coefficient of friction. A torque was applied to the nut while the ring section and bolt kept in place. The results for bolt load, nut rotation as well as axial and radial wire deformations were obtained. The results demonstrated a linear relation between the bolt load and the bolt torque. The coefficient of this relationship was shown to be inversely proportional to the coefficient of friction. For all results, the bolt load (N) was approximately 124 times the bolt torque (N m) divided by the friction coefficient. The results highlighted the difference between the cannulated and the slotted bolts in terms of their grip on the wire.