A comparative study of the correction of femoral deformity between the Ilizarov apparatus and Ortho-SUV Frame

A comparative evaluation of the time to frame removal for tibia fractures treated with hexapod and Ilizarov circular frames

INTRODUCTION

Traditional Ilizarov and hexapod frames have different biomechanical properties and there is limited literature regarding their effect on time to fracture union or time to frame removal.

METHODS

Tibial fractures managed with a circular frame at a tertiary limb reconstruction referral centre between 2011 and 2018 were retrospectively identified from a prospectively maintained database. They were classified into three treatment groups; Ilizarov style, Taylor Spatial Frame (TSF) and TrueLok Hex (TL-Hex). Data were extracted from electronic patient records and digital radiographs. The primary outcome was time to frame removal, which was seen as an indicator of clinical and radiological fracture union. Odds ratios were calculated with the clinical significance set at 30 days.

RESULTS

274 patients (median age 49 years, 36% female) were included in the analysis. 8.4% Ilizarov, 10.5% TSF and 13.5% TL-Hex frames required further surgery to aid fracture healing (p = 0.38). 30% of patients had open fractures. Median time to removal for Ilizarov, TSF & TL Hex frames was 167, 198 and 185 days respectively. There was a significant difference between Ilizarov and hexapod frames. Both TSF (OR 2.2, p<0.003) and TL-Hex (OR 1.8, p<0.04) had a significantly increased time to removal of 30 days or more compared with Ilizarov frames.The time to frame removal in metaphyseal fractures was significantly shorter for Ilizarov frame fixation than hexapod frames (p = 0.04). Open fractures were significantly more likely to require at least 30 days extra time to removal than closed fractures (OR 3.3, p<0.001). There was no significant difference in the time to frame removal between fracture location, age or sex.

CONCLUSION

Ilizarov frames have demonstrated a reduced time to frame removal in the management of tibial fractures than hexapod frames. Differences in the time to frame removal, an indicator of time to fracture union, may be due to the different mechanical properties of the frame, or early disruption of the fracture haematoma through secondary frame manipulation and fracture reduction, increased proportion of metaphyseal fractures treated with Ilizarov, or patient selection. The healing time was comparable across the tibia. Pooled meta-analyses may be able to further quantify these associations.

Experimental assessment of changes in bone fragment position using infraread diodes on saw bone models with a hexapod fixator

BACKGROUND

The purpose of this study was an experimental assessment of changes in bone fragment position in patients with non-union of the tibia treated with a hexapod fixator.

HYPOTHESIS

We hypothesized that the use of hexapod fixators leads to differences between the planned and actual position of bone fragments.

METHODS

The study was conducted in physical models of the hexapod fixator-bone fragment system. Bone fragment displacement was measured using the Optotrak Certus Motion Capture System. We assessed differences between the planned and actual position of bone fragments.

RESULTS

Assessment of bone fragment compression demonstrated a difference between the target and actual correction ranging from 1.5% to 13.2% (depending on the force applied to bone fragments) for configuration 1, from17% to 21.3% for configuration 2, and from 13.2% to 17.9% for configuration 3. The achieved varus deformity correction constituted 93.7-98.4% of the target correction for configuration 2 and 98.3-98.9% of the target correction for configuration 3. Torsional deformity correction showed considerable discrepancies between the target and achieved correction, ranging from 65.6% to 83%.

DISCUSSION

The value of the applied compression force had no marked effect on the differences between the target and achieved correction or on the magnitude of unintended rotational and transverse displacement of bone fragments. The use of hexapod fixators helped achieve complete correction of the simulated varus deformity; however, complete correction of torsional deformities was not achieved. Deformity correction in physical models with the use of a hexapod fixator yielded instances of unintended rotational and transverse bone-fragment displacement. The use of hexapod fixators in physical models leads to differences between the planned and actual position of bone fragments.

LEVEL OF EVIDENCE

IV, case series.

An Interference Inspection Algorithm of Limb and Hexapod Frame in the Treatment of Lower Limb Deformity

The Ortho-SUV frame is an innovative hexapod widely used in orthopedics for managing fractures and deformities. Avoidance of limb-frame interference is essential to verify the implementability of the pre-planned correction trajectory, as well as to maintain the continuity and security of the correction strategy. In this study, a novel interference inspection algorithm is developed to investigate the interaction of the limb and hexapod frame in the treatment of lower limb deformities. The algorithm is built on a minimum distance model of the cone frustum busbar and cylindrical axis using vector analysis. A pre-defined trajectory is generated by Cartesian coordinate path control. Subsequently, an interference case is performed through numerical simulation and motion simulation. The results show that the conclusion of numerical simulation and motion simulation are consistent, which prove the feasibility of the algorithm. The results also show that it is possible to identify the riskiest struts, which are prone to interfere with the limb, and the riskiest positions. The proposed algorithm can support the clinician in selecting the suitable frame configuration to avoid interference. The algorithm solves the problem that the interference can only be judged by clinical observation in the clinic.

Wedge-less oblique supracondylar femoral osteotomy and casting for genu valgum in older children and young adults

BACKGROUND

Genu valgum is one of the commonest deformities seen by the orthopaedicians. The most common cause is idiopathic but genu valgum secondary to nutritional deficiency is also fairly common in developing and third world countries. Supracondylar osteotomy and internal fixation with plate and screws, is the treatment of choice in older children and young adults, which is costly, requires a wide exposure, a second surgery for implant removal and risk of infection is more. This study was undertaken to measure the outcome of simple oblique percutaneous wedge-less metaphyseal supracondylar osteotomy of the distal femur and casting in older children and adolescents with Genu Valgum in a small centre catering mostly to patients from middle and low income households.

PATIENTS AND METHODS

Patients aged between 12 and 22 years with genu valgum deformity with a tibiofemoral angle ≥15°, and an intermalleolar distance of more than 7 cm in unilateral and more than 10 cm in bilateral cases, who are not amenable to be treated with guided growth techniques, were included. Patients having knee instability, restriction of knee range of motion, genu recurvatum, tibial deformity component, open physis, were excluded from the study. The correction was undertaken by a simple supracondylar wedge-less metaphyseal short oblique osteotomy of the distal femur followed by immobilization with a long leg plaster of Paris cast. Functional outcome was assessed using Böstman et al. score.

RESULTS

46 limbs in 29 patients with a mean age of 14.5 years were operated. The mean follow-up of patients was 6 months. The preoperative radiological tibiofemoral angle (TFA) had a mean value of 19.89° which improved to a mean of 5.31° postoperatively. Intermalleolar distance (IMD) improved from a mean of 13.81 cm to 3.15 cm post-correction. Mean Lateral distal femoral angle (LDFA) improved from 77.11° to 87.20°. Knee score was excellent in all patients at 3 months and 6 months post intervention. There were no serious complications except superficial plaster sores in 4 patients, which healed uneventfully and temporary restriction of knee range of motion in 5 patients. All patients achieved a full range of knee motion after physical therapy.

CONCLUSION

Supracondylar wedge-less short oblique metaphyseal distal femoral osteotomy and immobilization with plaster of Paris cast is a simple, cheap, safe & viable option for the correction of genu valgum deformity originating from distal femur, with minimal complications in older children and adolescents with limited growth potential, especially in low income countries and small centres.

Accuracy and Efficacy of Software-guided Bony Realignment in Periarticular Deformities of the Lower Limb

Aim and objective

Software-guided realignment is proposed as an easy and accurate method of achieving simultaneous multiaxial correction. The accuracy and efficacy in periarticular problems have not been investigated fully. This study investigates the results and possible clinical benefits.

Materials and methods

A retrospective review was performed in 24 patients with 27 periarticular deformities of the lower limb treated by the Ilizarov technique. Bony realignment was achieved by a software-guided hexapod realignment device. The deformity category, deformity severity score (DSS) and individual deformity component scores were measured for objective quantification of each deformity. The periarticular level, number of manoeuvres, correction period and any difficulties in the execution of the correction manoeuvre were noted. Pre-procedure and post-procedure values of deformity parameters were analysed to estimate the accuracy and efficacy of the realignment device.

Results

The correction manoeuvre was accomplished successfully in all patients except two. The mean correction period was 14.9 days (range, 5–38 days). The mean pre-procedure DSS was 18.7 (range 6.3–27.3), which reduced to a mean post-procedure value of 1.5 (range, 0–7.9) with a 92.0% deformity correction (p-value < 0.001)). There was a significant reversal of individual deformity components. DSS values were achieved to an excellent level (< 3.5) in 25 deformities and to good and poor levels in one deformity, respectively.

Conclusion

Software-guided realignments are effective for accurate realignment of periarticular deformities using Ilizarov fixators. These devices offer simultaneous multidimensional corrections even in complex multiplanar deformities and simplify the task of deformity correction.

Clinical significance

The present study assesses the accuracy and efficacy of software-guided realignments using novel concepts of deformity category, DSS and individual deformity component scores, which may overcome some of the shortcomings of conventional assessment methods.

How to cite this article

Singh P, Sabat D, Dutt S, et al. Accuracy and Efficacy of Software-guided Bony Realignment in Periarticular Deformities of the Lower Limb. Strategies Trauma Limb Reconstr 2021;16(2):65–70.

Influence of parameter deviation on the closeness of the tibial limb and external fixator based on a novel collision detection algorithm

The Ortho-SUV frame (OSF) is a hexapod external fixator widely applied in orthopedics deformity correction. The possibility of collision between OSF's struts and the soft tissue is an essential but overlooked issue. To avoid the issue, a novel collision detection algorithm is established based on a cone-cylinder model of the tibial limb-strut interaction for detecting the closeness of the tibial limb and external fixator. The algorithm is constructed using the vector analysis based on the model of the minimum distance between the truncated cone generatrix and the cylinder axis. The motion simulation is performed on the overall alignment through the Solidworks-motion module to verify the feasibility of the algorithm. Subsequently, the installation parameter deviations of the bone-fixator system are described to investigate the influence of orientation and position deviation on the closeness of the tibial limb and external fixator through the numerical method. The investigation results show that the orientation deviation γ (around the z-axis), the position deviation τ₁ and τ₂ (along the x and y-axes, respectively) have greater sensitivity to closeness and the influence of multiple deviations on the closeness has the property of superposition. The proposed algorithm can assist clinicians to strictly design and appraise frame configurations prior to their application to avoid the collision between the external fixator and the limbs during the correction. It has great application significance in the development of computer-aided correction software.

Comparison of three different correction trajectories for foot and ankle deformity treated by supramalleolar osteotomy using a novel external fixator

Based on the principle of distraction osteogenesis, external fixators are widely used in deformity correction of the foot and ankle. In this study, a novel ankle external fixator is proposed to correct complex multiplane deformities, especially for supramalleolar osteotomy to correct distal tibia deformities. The relatively simple structure and fewer struts in the proposed fixator reduce the complexity of adjusting the external fixator. Based on two existing adjustment strategies, a new strategy taking into account the orientation and shortest path of the ankle joint center is proposed, which is named joint adjustment for equal bone distraction. By proposing the inverse kinematic solutions of the novel external fixator, mathematical derivations of the bone trajectory and modelling of the bone shape for the three distraction strategies are performed. The results obtained by comparative analysis indicate that a uniformly spaced path of the ankle joint center can be acquired, and a smooth and uniform correction trajectory of the distal tibia end can be obtained using the new adjustment strategy. It can avoid bone end interference and only generates a maximum deviation 0.66% greater than the currently optimal 1 mm/day. The new strategy can perform multiplane corrections simultaneously, which shortens the correction time and reduces the patient's pain.

External fixation of the lower extremities: Biomechanical perspective and recent innovations

The concept of supporting fractured long bones externally with mechanical fixation has been evidentially applied for over 2000 years, and since been expanded on in the mid-19th century by percutaneous bone fixation. Surgical techniques, external fixator systems, and materials have made continued progress since. The benefits of traditional external fixation have been enhanced in recent years with the introduction of hexapod-style fixators, innovative configurations, and pin modifications, among other things. It is generally agreed upon that biomechanical testing of advancements in external fixation must be inclusive of transverse or torsional loading to simulate construct behaviour in realistic scenarios. Biomechanical studies indicate that hexapod-style fixators show comparable axial stiffness to Ilizarov-style systems and improved performance under torsional and transverse forces. The addition of configuration elements to fixators, inclusion of certain carbon fibre chemical compositions, and techniques intended to augment ring thickness have also been investigated, in hopes of increasing construct stiffness under loading. Novel external fixators attempt to broaden their applications by rethinking bone mounting mechanisms and either expanding on or simplifying the implementation of 3D bone segment transport for corrective osteotomy. Older and seemingly unconventional fixation techniques are being rediscovered and evolved further in order to increase patient comfort by improving everyday usability. The development of new pin coatings can potentially enhance the pin-bone interface while lowering infection rates typically expected at thicker soft tissue envelopes. Although complication, malunion, and nonunion rates have decreased over the past 50 years, the clinical results of external fixation today can still be optimized. Unsatisfactory healing in the lower extremities has especially been reported at locations such as the distal tibia; however, advancements such as osteoinductive growth hormone treatment may provide improved results. With the current progression of technology and digitization, it is only a matter of time before 'smart', partly-autonomous external fixation systems enter the market. This review article will provide a versatile overview of biomechanically proven fixator configurations and some carefully selected innovative systems and techniques that have emerged or been established in the past two decades.

The unstable knee in congenital limb deficiency

PURPOSE

Instability of the knee is a common finding in patients with congenital limb deficiency. The instability can be attributed to soft tissue abnormalities, frontal, sagittal or rotational deformity of the lower limb and bony dysplasia of the patella or of the femoral condyles. In most of the cases, these pathomorphologic changes stay asymptomatic in daily activity. However, instability can appear during deformity correction and bone-lengthening procedures, leading to flexion contracture or subluxation of the knee.

METHODS

A review of pediatric orthopaedic literature on different factors of knee instability, state-of-the-art treatment options in congenital limb deficiency and in cases of lengthening-related knee subluxation is presented and the authors' preferred treatment methods are described.

RESULTS

Leg lengthening and deformity correction in patients with congenital limb deficiencies can be achieved with various techniques, such as guided growth, monolateral or circular external fixation and intramedullary lengthening nails. Radiographic assessment and clinical examination of the knee stability are obligatory to estimate the grade of instability prior to surgical procedures. Preparatory surgery, as well as preventive measures such as bracing, bridging of the knee and intensive physical therapy, can help to avoid subluxation during lengthening in unstable knees.

CONCLUSIONS

Adequate surgical techniques, preventive measures and early detection of signs of subluxation can lead to good functional results in patients with congenital limb deficiency.

Definitive management of significant soft tissue loss associated with open diaphyseal fractures utilising circular external fixation without free tissue transfer, a comprehensive review of the literature and illustrative case

Accepted management of diaphyseal fractures associated with significant tissue loss is rigid intramedullary stabilisation with free or rotational musculocutaneous flap coverage. Circular external fixation is a powerful tool in the management of limb trauma and with recent advances has been developed to provide multiple techniques for which even massive tissue loss can be addressed without the need for free tissue transfer. Gradual and acute shortening, acute fracture deformation and gradual lengthening with restoration of deformity combined with distraction tissue histiogenesis can provide the surgeon with an array of options which can be precisely tailored to the particular personality of a severe open diaphyseal fracture.

[Treatment strategy for posttraumatic complex deformity. After bilateral femoral shaft fractures]

A case of complex posttraumatic deformity after bilateral femoral shaft fractures is reported. Different possibilities for correction in cases of valgus malalignment combined with internal rotation deformity as well as shortening combined with external rotation deformity are presented. Oblique osteotomy and a motorized femoral extension nail were used.

Determination of the Maximal Corrective Ability and Optimal Placement of the Ortho-SUV Frame for Femoral Deformity with respect to the Soft Tissue Envelope, a Biomechanical Modelling Study

Circular fixation according to the Ilizarov method is a well-recognised modality of treatment for trauma and deformity. One shortcoming of the traditional fixator is its limited ability to correct more than one plane of deformity simultaneously, leading to lengthy frame-time indices. Hexapod circular fixation utilising computer guidance is commonplace for complex multidimensional deformity but difficulties often arise with correction of femoral deformity due to bulkiness of the frame construct, particularly in proximal deformity and in patients of increased size. The Ortho-SUV frame is an innovative hexapod which permits unique customisation to individual patient anatomy to maximise tolerance and optimal range of deformity correction. We hypothesised that the optimal configuration and maximal degree of correction achievable by the Ortho-SUV frame can be biomechanically modelled and applied clinically. A study was constructed using Ortho-SUV and femoral limb models to measure deformity correction via differing frame constructs and determine optimal frame configuration to achieve correction in proximal, middle, and distal third deformities with respect to the soft tissue envelope. The ideal frame configuration is determined for correction of deformity in all locations of the femur with the maximal parameters of correction calculated whilst avoiding and mitigating soft tissue irritation from bulky frame construction.