Magnetic Nail Research Articles

Clinical compatibility of magnetic resonance imaging with magnetic intramedullary nails: a feasibility study.

The use of magnetic resonance imaging (MRI) with a magnetic intramedullary lengthening nail in place is contraindicated per the manufacturer due to the concern of implant activation and migration. A prior in vitro study did not confirm these complications only noting that a 3.0T MRI weakened the internal magnet. Therefore, a retrospective analysis of patients who underwent an MRI with a magnetic nail in place was performed to determine if any adverse effects occurred in the clinical setting. A retrospective review of all patients who underwent an MRI with a magnetic lengthening nail in place was performed. The time spent being imaged in the MRI, number of times the patient entered the MRI suite, and the images obtained were recorded. Radiographs were performed before and after the MRI to determine if any hardware complications occurred. The patients were monitored for any adverse symptoms while they were in the suite. A total of 12 patients with 13 nails were identified. Two patients underwent imaging with a 3.0T MRI while the remaining 10 underwent imaging with a 1.5T MRI. Each patient entered the MRI suite 2.1 times and spent an average of 84.7min being imaged in the MRI (range 21-494). No patients noted any adverse symptoms related to the nail while in the suite and no hardware complications were identified. MRI appears to be safe with a magnetic nail in place and did not result in any complications. Given the manufacturer's recommendations, informed consent should be obtained prior to an MRI being performed and a 3.0T MRI should be avoided when possible if further activation of the nail is required.

Lengthening Patients Previously Treated for Massive Lower Limb Reconstruction for Bone Tumors with the PRECICE 2 Nail.

The objective of this study was to determine the efficacy of the PRECICE 2® nail in the treatment of lower limb length discrepancy in patients with a history of bone tumors. This study reports on outcomes, complications, and the safety of the PRECICE 2 limb lengthening nail in a cohort of pediatric patients with limb length discrepancy after surgery for bone tumors. Seventeen patients were treated with intramedullary magnetic nails. The average patient age at the time of surgery was 19 (range 11-32). The PRECICE 2 nail was used on 14 femurs (6 retrograde and 8 anterograde) and 3 tibias. The average consolidation time was 141 days (range 50-360) with a mean CI of 31 ± 12 days/cm. The ASAMI bone score showed 14 (82%) excellent results, 1 (6%) good result, and 2 (12%) poor results. The ASAMI functional score showed 13 (84.6%) excellent results, 3 (11.5%) good results, and 1 (3.8%) fair result. Patients treated with chemotherapy for bone cancer did not show any increase in distraction time or consolidation time. A total of 3 (17%) problems, 1 obstacle (5.5%), and 1 complication (5.5%) were encountered in our case series. The PRECICE 2 nail allows for effective and accurate lengthening preserving the range of motion in patients treated for bone tumors.

Anti-conflict AGV path planning in automated container terminals based on multi-agent reinforcement learning

AGV conflict prevention path planning is a key factor to improve transportation cost and operation efficiency of the container terminal. This paper studies the anti-conflict path planning problem of Automated Guided Vehicle (AGV) in the horizontal transportation area of the Automated Container Terminals (ACTs). According to the characteristics of magnetic nail guided AGVs, a node network is constructed. Through the analysis of two conflict situations, namely the opposite conflict situation and same point occupation conflict situation, an integer programming model is established to obtain the shortest path. The Multi-Agent Deep Deterministic Policy Gradient (MADDPG) method is proposed to solve the problem, and the Gumbel-Softmax strategy is applied to discretize the scenario created by the node network. A series of numerical experiments are conducted to verify the effectiveness and the efficiency of the model and the algorithm.

A Simplified Magnetic Positioning Approach Based on Analytical Method and Data Fusion for Automated Guided Vehicles

Magnetic positioning approach (MPA) is a reliable solution for automated guided vehicles (AGVs) under relatively fixed route conditions. Ferrite magnets are usually buried in the ground and employed as magnetic nails (MNs) for the parking and steering of AGVs. Our previous studies implemented a novel MPA based on super-strong NdFeB magnets and the minimize iterations between magnetometer data and predicted values via the magnetic dipole model, with the advantage of more exceptional positioning performance than traditional MPAs. Nevertheless, the iterative optimization algorithms depend on the initial guess setting; besides, the complicated calculation based on multiple magnetometer data makes it difficult to be executed on a microcontroller in real-time. In this article, we propose a simplified MPA based on the analytical method. The analytical expression for calculating the two-dimensional position of an MN is derived from the magnetic dipole model. Even a single tri-axis magnetometer can localize the MN, whereas multiple magnetometers tend to achieve higher positioning performance. Thus, positioning results of multiple magnetometers are fused based on the confidence criterion. Comparing with the MPA based on the Levenberg–Marquardt algorithm, the proposed MPA could achieve comparable positioning accuracy but with far lower computational complexity and greater robustness. Thereby, this article introduces a new concept of high-precision MPA for AGV applications without the complicated visual perception.

Neurosurgical developments of Thierry de Martel (1875-1940), French neurosurgery pioneer, during World Wars I and II.

Following France's entry into World War I on August 3, 1914, Thierry de Martel (1875-1940), the French neurosurgery pioneer, served on the front line and was wounded on October 3, 1914. He was then assigned as a surgeon in temporary hospitals in Paris, where he published his first observations of cranioencephalic war wounds. In 1915, de Martel met Harvey Cushing at the American Hospital in Neuilly, where de Martel was appointed chief surgeon in 1916. In 1917, he published with the French neurologist Charles Chatelin a book (Blessures du crâne et du cerveau. Clinique et traitement) with the aim to optimize the practice of wartime brain surgery. This book, which included the results of more than 5000 soldiers with head injuries, was considered the most important ever written on war neurology at that time and was translated into English in 1918 (Wounds of the Skull and Brain; Their Clinical Forms and Medical and Surgical Treatment). In this book, de Martel detailed the fundamentals of skull injuries, classified the various craniocerebral lesions, recommended exploratory craniectomy for cranioencephalic injuries, recommended the removal of metal projectiles from the brain using a magnetic nail, and advocated for the prevention of infectious complications. Between the World Wars, de Martel undertook several developments for neurosurgery in France alongside neurologists Joseph Babinski and Clovis Vincent. Following France's entry into World War II on September 3, 1939, de Martel took over as head of the services of the American Hospital of Paris in Neuilly. He updated his work on war surgery with the new cases he personally treated. Together with Vincent, de Martel presented his new approach in "Le traitement des blessures du crâne pendant les opérations militaires" ("The treatment of skull injuries during military operations") on January 30, 1940, and published his own surgical results in April 1940 in "Plan d'un travail sur le traitement des plaies cranio-cérébrales de guerre" ("Work Plan on the Treatment of Cranio-Cerebral Wounds of War"), intended for battlefield surgeons. On June 14, 1940, the day German troops entered Paris, de Martel injected himself with a lethal dose of phenobarbital. Thierry de Martel played a central role in establishing modern neurosurgery in France. His patriotism led him to improve the management of wartime cranioencephalic injuries using his own experience acquired during World Wars I and II.

Translated article] Bone lengthening with magnetic nails. Experience in patients younger than 18

Background and goalBone elongation with magnetic endomedullary nails (MEN) has been proposed as an advantageous alternative to other techniques, by eliminating the drawbacks of external fixation. The aim of this work is to analyse the results and assess the complications in a series of patients under the age of 18. Material and methodsFrom 2014 to 2019, 31 elongations (23 femurs, 8 tibias) using MEN (Precice2®) have been performed in 28 patients younger than 18 (15 males and 13 females). In this observational retrospective study, only patients with follow-up longer than 18 months have been included. The average age has been 14.4 years (8–18). The most relevant aspects analysed have been: previous shortening/deformity, elongation/correction achieved and time to full weight bearing. Complications and re-interventions have also been assessed. ResultsThe elongation achieved has been 5.5cm on average (3–8). In 28 elongations (90.3%) the planned goal of lengthening was achieved. The mean healing index (HI) was 1.1months/cm. More than half of elongations (55%) presented complications. Although they produced permanent sequelae in only two patients (7.1%), a total of 9 patients required re-intervention (13 operations). No infections were detected. ConclusionsBone lengthening with MEN in individuals younger than 18 has achieved its goal in more than 90% of patients in an effective, accurate and safe manner. The use of MEN in this series has eliminated the need for external fixators and has successfully tutorized the operated segment. The high number of complications detected in this study remains a concern.

Magnetic nails! Introduction of the terrazzo pattern on histopathology, as well as clinical and dermatoscopic features of a trendy nail cosmetic.

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Quality of life of children during distraction osteogenesis: a comparison between intramedullary magnetic lengthening nails and external fixators

BackgroundDistraction osteogenesis is a very demanding process. For decades, external fixation was the only reliable option for gradual deformity correction. Recently, intramedullary magnetic nails have gained popularity. This research aimed to assess the quality of life in children during gradual deformity correction using intramedullary lengthening nails compared to external fixation.MethodProspective analysis included children who had gradual lower limb deformity correction between 2017 and 2019. Group A included children who had magnetic lengthening nails; patients in group B had external fixation devices. Child health utility 9D (CHU- 9D) and EuroQol 5D youth (EQ- 5D-Y) were used to measure the quality of life at fixed points during the distraction osteogenesis process. The results were used to calculate the utility at each milestone and the overall quality of life adjusted years (QALYs).ResultsThirty-four children were recruited, group A had 16 patients, whilst group B had 18 patients. The average ages were 16.0 years and 14.7 years for groups A and B, respectively. Group A patients reported significantly better utility compared to group B. This was observed during all stages of treatment (P = 0.00016). QALYs were better for group A (0.44) compared to group B (0.34) (P < 0.0001).ConclusionThe quality of life was generally better in group A compared to group B. In most patients, the health utility progressively improved throughout treatment. In the same way, QALYs were better with the lengthening nails compared to external fixators. The magnetic lengthening devices (PRECICE nails) which were used in this research were recently relabelled to restrict their applications in children; this study was conducted before these restrictions.

Pseudo-Anchors: Robust Semantic Features for Lidar Mapping in Highly Dynamic Scenarios

Dynamic environments are challenging for anchor-free mapping using lidar in intelligent driving. This study imitates anchor-based approaches such as magnetic nails by applying novel Static Confidence Criteria (SCC) to the point-cloud semantic candidates to ensure their robustness. We name such verified features Pseudo-Anchors (P-A) as they hold similar properties to the anchor nodes: The P-A nodes are improbably formed by dynamic objects, and nodes’ blockage state can be immediately noticed once they are occluded. Another major challenge for mapping is improving large-scale global performance without sacrificing local consistency. Unrecognized GNSS pose drift may deteriorate local trajectory accuracy through post-processing such as graph optimization. In this study, we use the road network to provide the intersection information as a prior so that the GNSS can be better regarded as a reliable anchor factor. Three experiments are designed for this study. The first is ablations to verify the P-A concept; The second proves that the P-A-based lidar odometry outperformed the LOAM-based mainstream methods in highly dynamic scenarios; The third shows that our usage of the GNSS strengthens large-scale maps’ global consistency while causing less deterioration towards the local one. As a knowledge-based method, the P-A concept shows a high deployment efficiency, indicating the potential for migration to other features or even other sensors.

Comparison of Intramedullary Magnetic Nail, Monolateral External Distractor, and Spatial External Fixator in Femur Lengthening in Adolescents with Congenital Diseases.

The aim of this study is to evaluate the course of the treatment and clinical and functional outcomes of femur lengthening in adolescents with congenital disorders by the application of different surgical methods. This retrospective study comprised 35 patients (39 procedures). A total of 11 patients underwent femur lengthening with the use of the intramedullary magnetic nail (IMN) Precise 2 (NuVasive, San Diego, CA, USA), 7 patients (11 procedures) with the use of the monolateral external distractor Modular Rail System (MRS) (Smith and Nephew, Memphis, TN, USA), and 17 with the use of the computer-assisted external fixator Taylor Spatial Frame (TSF) (Smith and Nephew, Memphis, TN, USA). The inclusion criteria were as follows: (1) congenital femoral length deficiency without any axial deformities and (2), independently of the finally applied treatment, the technical possibility of use of each of the analyzed methods. The distraction index did not differ significantly between the groups (p = 0.89). The median lengthening index was the lowest in the IMN group (24.3 d/cm; IQR 21.8–33.1) and statistically different in comparison to the MRS (44.2 d/cm; IQR 42–50.9; p < 0.001) and the TSF groups (48.4 d/cm; IQR 38.6–63.5; p < 0.001). Similarly, the consolidation index in the IMN group (12.9 d/cm; IQR 10.7–21.3) was statistically lower than that in the MRS (32.9 d/cm; IQR 30.2–37.6; p < 0.001) and the TSF (36.9 d/cm; IQR 26.6–51.5; p < 0.001) groups. This study indicates that IMN is a more valuable method of treatment for femoral length discrepancy without axial deformity than MRS and TSF in complication rate and indexes of lengthening and consolidation.

Use of a Motorized Intramedullary Bone Transport Nail for Trauma: Tips, Tricks, Corticotomy Techniques, and Rate and Rhythm.

The introduction of internal magnetic nails (IMNs) for bone lengthening and bone transport has given us exciting new tools with which to treat segmental bone loss. Distraction osteogenesis has a long record of success in recreating even large segments of bone, but the availability of IMNs now offers the possibility of performing distraction osteogenesis without the drawbacks of external fixation. However, there are aspects of treatment with IMNs that are critical to understand to achieve success and minimize complications. These include assessment of feasibility in relation to available bone stock and segment configuration, the condition of the soft tissue envelope, and the presence of contamination or infection. They also include execution aspects such as bone end preparation, nail placement, need for and positioning of adjuvant fixation, corticotomy techniques, rate and rhythm of distraction, staged screw exchange, docking site preparation, and nail extraction. We discuss these issues in detail and introduce some novel techniques not previously described including the comminuted wedge osteotomy, testing of the nail with initial compression, and retention plug application for nail extraction to assist in optimizing success in certain clinical situations.

Limb lengthening with PRECICE magnetic nail in pediatric patients: A systematic review

BACKGROUNDLimb lengthening techniques play an increasingly important role in the pediatric orthopedic field. The principles of the osteogenesis distraction bonded traditionally with external fixators; however, the recent deployment of fully implantable systems has been able to overcome severities related to external fixators. The PRECICE® is an implantable limb lengthening intramedullary nail system that is remotely controlled and magnetically driven.AIMTo review the current literature available on this matter in order to assess the PRECICE clinical and radiological outcomes and its possible complications in a population of pediatric patients undergoing limb lengthening.METHODSOnly five studies met the inclusion criteria and were consequently included in the review for a total of 131 patients and 135 femurs. The clinical and radiological outcomes of interest were: the main lengthening obtained, the distraction rate, the period of time to full weight bearing, the consolidation index, and the Association for the Study and Application of Methods of Ilizarov score.RESULTSIn conclusion, data collected from the articles under investigation were comparable with the exception of the consolidation index. Unfortunately, the study population was too small and the patients’ follow-up was too short to make definitive conclusions. CONCLUSIONThis review shows that the PRECICE Nail System is still a therapeutic challenge in limb lengthening for pediatric orthopedic surgeons; however, careful pre-operative planning and an accurate surgical technique could allow the correction of more complex deformities with a low rate of complications.

Cost Comparison of Tibial Distraction Osteogenesis Using External Lengthening and Then Nailing vs Internal Magnetic Lengthening Nails.

Aim and objectiveTibial lengthening can be performed by distraction osteogenesis via lengthening and then nailing (LATN) or by using a magnetic lengthening nail (MLN). MLN avoids the complications of external fixation while providing accurate and easily controlled lengthening. Concerns exist still regarding the high upfront cost of the magnetic nail, which serves to limit its use in resource-poor areas and decrease adoption among cost-conscious surgeons. The purpose of this study was to compare the hospital, surgeon, and total cost between LATN and MLN when used for tibial lengthening.Materials and methodsA retrospective review was performed comparing consecutive tibial lengthening using either LATN (n = 17) or MLN (n = 15). The number of surgical procedures and time to union were compared. Surgeon and hospital payments were used to perform cost analysis after adjusting for inflation using the consumer price index (CPI).ResultsPatients treated with MLN underwent fewer surgeries (3.6 vs 2.8; p < 0.001) but had a longer time to union as compared with patients treated with LATN (19.79 vs 27.84 weeks; p = 0.006). Total costs were similar ($50,345 vs $46,162; p = 0.249) although surgeon fees were lower for MLN as compared with LATN ($6,426 vs $4,428; p < 0.001).ConclusionLATN and MLN had similar overall costs in patients undergoing tibial lengthening. MLN was associated with fewer procedures but a longer time to union as compared with LATN.Clinical significanceDespite an increased upfront cost in MLN, there was no difference in total cost between LATN and MLN when used for tibial lengthening. Thus, in cases where either method is feasible, cost may not be a deciding factor when selecting the appropriate treatment.How to cite this articleDvorzhinskiy A, Zhang DT, Fragomen AT, et al. Cost Comparison of Tibial Distraction Osteogenesis Using External Lengthening and Then Nailing vs Internal Magnetic Lengthening Nails. Strategies Trauma Limb Reconstr 2021;16(1):14–19.

Changes in the femoral osteotomy level coefficient and neck shaft angle during limb lengthening with an intramedullary magnetic nail.

The intramedullary magnetic IM nail enables bone graduated distraction. Proximal femur osteotomies for ante grade IM lengthening nails have a tendency towards varus-procurvatum malalignment. We examined the effect of the level of the osteotomy and of trochanteric versus piriformis entry points on the neck shaft angle (NSA) during lengthening with the PRECICE IM magnetic nail. A novel parameter, the osteotomy level coefficient (OLC), was introduced as a guide to determine the level of an osteotomy at the proximal femur. The OLC was defined as the ratio between the distances from the tip of the greater trochanter to the osteotomy divided by the full length of the femur. A retrospective review of all femoral lengthening procedures with the PRECICE ante grade IM lengthening nail between 2013 and 2018 was carried out. 31 femurs were lengthened in 30 patients (16 males and 14 females, mean age at surgery years 17.1. The average amount of lengthening was 4.4cm. Trochanteric entry points were used in 24 femurs, and piriformis entry points in seven femurs. The OLC values ranged from 0.16 to 0.34 (average 0.25). The average follow-up period was 10.15months. The distraction index average 10.5days/cm (Range 8.6-11.9), Consolidation index 32.1days/cm (14.3-51.9). The average post-operative NSA was significantly reduced from 133.5º to 128.5º [t (31) = 5.57, p = 0.000]. There was no correlation between the OLC and the change in the NSAs. The trochanteric entry point showed a greater tendency to reduce the NSA (Mdif = - 6, SD = 4.8) compared to the piriformis entry point (Mdif = - 0.86, SD = 2.27) [t (31) = -3.96, p = 0.001]. Proximal femur lengthening with the PRECICE IM nail significantly reduced the NSA and might cause Varus deformity. The level of osteotomy by OLC did not influence the amount of NSA reduction. The trochanteric entry points have a greater tendency to reduce the NSA compared to the piriformis entry points.

Combined antegrade femur lengthening and distal deformity correction: a case series

BackgroundLeg length discrepancy is often associated with distal femur angular deformities such as valgus or flexion. This study aims to report a new technique for simultaneous limb lengthening and acute distal femoral angular correction.MethodsA retrospective chart review of patients undergoing a single procedure was conducted. Patients included had a single operation where they underwent distal femur osteotomy stabilized with a plate followed by antegrade nailing with a magnetically controlled intramedullary lengthening nail (PRECICE, Ellipse Technologies, Inc., Irvine, CA, USA) using a trochanteric entry.ResultsSeven femurs from 7 patients were included. The average age at operation was 13.6 years, and the leg length difference was 51 mm (range 30–105 mm). Associated deformities were valgus (4), knee flexion contracture (2), and both valgus and flexion contracture (1). Lengthening achieved was 43 mm (P = 0.0036), with a consolidation index of 27 days/cm and reliability of 0.87 (6/7). The 5 patients with angulation had an improvement of valgus from 12 to 4° (P = 0.006) and of the mechanical axis deviation from 34 to 3 mm (P = 0.0001). The range of motion also improved in the 3 patients with contractures. Preoperative gait disturbance, hip and knee pain, and functional scoliosis resolved after the limb deformities were corrected.ConclusionCombining a magnetic internal lengthening nail with a second distal osteotomy stabilized with a plate can successfully correct limb length and distal femur deformity acutely without altering the expected result of each procedure.

Improved Magnetic Guidance Approach for Automated Guided Vehicles by Error Analysis and Prior Knowledge

Navigation accuracy and robustness are key performance indexes of automated guided vehicles (AGVs). In our previous study, the magnetic guidance approach based on magnetic dipole model and non-linear optimization algorithm was proposed, which has high positioning accuracy and could estimate the yaw angle of AGV directly. However, the localization accuracy of the magnetic guidance approach will deteriorate if the magnetic nails (MNs) buried in the ground have installation errors or the magnetic moments between the MNs are inconsistent. To overcome this problem, we propose an improved method based on error analysis and prior knowledge for the magnetic guidance approach. Firstly, the factors that affect the localization accuracy are analyzed, and the parameters ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B_{\mathrm {T}}$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$p$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$c$ </tex-math></inline-formula> ), whose errors will deteriorate the localization accuracy, are combined with MN pose ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$a$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$b$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$m$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> ) as optimization variables. Then, the prior knowledge regarding ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$B_{\mathbf {T}}$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$p$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$c$ </tex-math></inline-formula> ) is employed to construct the constraint conditions for the magnetic guidance approach. Finally, the global convergence probability and convergence speed of the improved magnetic guidance approach are analyzed. Experimental results demonstrate the adaptability and robustness of the improved magnetic tracking approach, which diminishes the impact of MN installation errors and magnetic moment deviation. The parking accuracy of AGV is improved to 1.42±0.85 mm and 1.10±0.38°.

Clinical results and complication rates of lower limb lengthening in paediatric patients using the PRECICE 2 intramedullary magnetic nail: a multicentre study.

Implantable intramedullary nail lengthening devices (e.g., PRECICE 2 system) have been proposed as alternative method to external fixation for lower limb lengthening surgery. The aim of this study was to analyse our outcomes and complications using the PRECICE 2 (P2) nail system and review them in light of the existing literature. A retrospective multicentre study was conducted on patients <18 years, who were treated for limb lengthening using the P2 system. The inclusion criteria were a limb length discrepancy ≥ 30 mm and a follow-up ≥6 months after the end of treatment. A total of 26 (15 males) patients were included, average age was 14.7 ± 2.3 years; 26 nails (21 femur, 5 tibia) were implanted. The average goal lengthening was 49.4 ± 12.4 mm, while average achieved lengthening was 44.4 ± 11.6 mm. Average distraction and consolidation indexes were 11.9 ± 2.1 days/cm and 25.1 ± 8.1 days/cm, respectively. Nail accuracy and reliability were 91.1% and 88.5%, respectively. A total of five problems (joint contractures), one obstacle (femur fracture) and three complications (hip joint subluxation, deep infection and nail running back) were encountered. The P2 nail system is a valid alternative to external fixator for limb lengthening in young patients with no significant angular or rotation deformities. Our study confirms a favourable complication rate and available evidence from literature suggests a lower complication rate than external fixator systems. Nevertheless, surgeons should keep a watchful eye on risk of joint subluxation and mechanical complications with intramedullary lengthening.

Positioning Accuracy Improvement of Automated Guided Vehicles Based on a Novel Magnetic Tracking Approach

Automated guided vehicles (AGVs) have been widely adopted in the logistic delivering of modern manufacturing. As a key performance index for an AGV, the positioning accuracy of commercial AGVs based on the traditional magnetic tracking approach is bigger than ?5mm, which cannot meet the requirement of many industrial applications. Thus, we proposed a novel magnetic tracking approach to improve the positioning accuracy of AGVs. A super strong magnetic nail, instead of the low-remanence magnetic nail, can be more easily tracked by a two-dimensional (2D) rather than 1 D sensor array. The magnetic flux intensity around the magnetic nail can be expressed as a dipole model. Hence, the location and orientation of the nail can be computed via the sensor array data and a hybrid optimization algorithm, which is combined by the particle swarm optimization (PSO) algorithm and Levenberg-Marquardt (LM) algorithm performed on a microcontroller. We carried out experiments to verify the performance of the proposed positioning system in a series of initial driving speeds and target distances, where an N35 neodymium magnetic nail functioned as the designated AGV positioning point. Results show that the average positioning accuracy is improved to ±1.69mm, and the positioning accuracy can be further improved by a better motion control strategy. In addition, our proposed magnetic tracking approach can be easily fused with other navigation approaches such as laser and inertial sensing.

Pelvic Support Hip Reconstruction with Internal Devices: An Alternative to Ilizarov Hip Reconstruction.

Aim and objectiveIlizarov hip reconstruction (IHR) is a traditional method of salvaging chronic adolescent problem hips but faces practical issues from external fixators leading to reduced compliance. We present the same reconstruction procedure using only internal devices with a modification in the technique and review early results.Materials and methodsWe retrospectively evaluated eight patients between 2014 and 2017 with chronic painful hips treated by two-stage reconstruction; stage I included femoral head resection and pelvic support osteotomy using double plating, whereas stage II comprised distal femoral osteotomy avoiding varus followed by the insertion of a retrograde magnetic nail for postoperative lengthening. Patients continued physiotherapy postoperatively while protecting from early weight-bearing.ResultsAt a mean follow-up of 19 months (range, 6–36), all osteotomies healed with a bone healing index of 47 days/cm (range, 30–72). Pain improved from 8.3 (range, 7–9) to 2 (range, 0–6) while the limb length discrepancy got corrected from 4.3 cm (range, 3–5) to 1.4 cm (range, 0–2.5) at the final follow-up. Trendelenburg sign was eliminated in three patients and delayed in five patients. No examples of infection or permanent knee stiffness were noted. One patient had plate breakage due to mechanical fall, and another patient had 35 mm of lateral mechanical axis deviation (MAD) requiring corrective osteotomy.ConclusionPelvic support hip reconstruction with exclusive internal devices is a technique in evolution with encouraging early results. It avoids common complications of external fixators and facilitates quick rehabilitation of joints. Refraining from distal varus can effectively eliminate Trendelenburg gait, although with some degree of lateral MAD. Unlike external fixation where there is a possibility of gradual correction, this staged procedure of internal fixation is technically demanding with a learning curve.Clinical significancePelvic support hip reconstruction performed by internal implants is a viable alternative to Ilizarov hip reconstruction with potential benefits.How to cite this articleMetikala S, Kurian BT, Madan SS, et al. Pelvic Support Hip Reconstruction with Internal Devices: An Alternative to Ilizarov Hip Reconstruction. Strategies Trauma Limb Reconstr 2020;15(1):34–40.

Pelvic Support Hip Reconstruction with Internal Devices: An Alternative to Ilizarov Hip Reconstruction.

Aim and objectiveIlizarov hip reconstruction (IHR) is a traditional method of salvaging chronic adolescent problem hips but faces practical problems from external fixators leading to reduced compliance. We present the same reconstruction utilising only internal devices with a modification in technique and aim to review early results.Materials and methodsWe retrospectively evaluated eight patients between 2014 and 2017 with chronic painful hips treated by a two-stage reconstruction; stage 1 included femoral head resection and pelvic support osteotomy using double plating, while stage 2 comprised distal femoral osteotomy avoiding varus followed by insertion of retrograde magnetic nail for postoperative lengthening. Patients continued physiotherapy postoperatively while protecting from early weight-bearing.ResultsAt mean follow-up of 19 months (range 6–36), all osteotomies healed with bone healing index of 47 days/cm (range 30–72). Pain improved from 8.3 (range 7–9) to 2 (range 0–6), while limb length discrepancy got corrected from 4.3 cm (range 3–5) to 1.4 cm (range 0–2.5) at final follow-up. Trendelenburg sign was eliminated in three and delayed in five. No examples of infection or permanent knee stiffness were noted. One patient had plates breakage due to mechanical fall and one had 35 mm of lateral mechanical axis deviation requiring corrective osteotomy.ConclusionPelvic support hip reconstruction with exclusive internal devices is a technique in evolution with encouraging early results. It avoids common complications of external fixators and facilitates quick rehabilitation of joints. Refraining from distal varus can effectively eliminate Trendelenburg gait, albeit with some degree of lateral mechanical axis deviation. Unlike external fixation where there is a possibility of gradual correction, this staged procedure of internal fixation is technically demanding with a learning curve.Clinical significancePelvic support hip reconstruction performed by internal implants is a viable alternative to IHR with potential benefits.How to cite this articleMetikala S, Kurian BT, Madan SS, et al. Pelvic Support Hip Reconstruction with Internal Devices: An Alternative to Ilizarov Hip Reconstruction. Strategies Trauma Limb Reconstr 2020;15(2):91–97.