Lateral Gap Research Articles

Modeling multi-class disordered traffic flow subject to varying vehicle composition using the concept of traversable distance

Disordered traffic stream at the microscopic level can be described as a permeable medium. Each vehicle is considered to traverse through a series of lateral gaps created by other vehicles. We develop a multi-class traffic flow model that considers such viable and accessible gaps for individual vehicle classes to traverse downstream. The model accounts for the varying shares of different vehicle classes. The concept of traversable distance and modified equilibrium speed functions are used to model the interplay among multiple vehicle classes. Using a higher order finite volume approximation method, evolution for a two-class traffic stream is shown. This model replicates prominent empirical characteristics exhibited by multi-class disordered traffic such as overtaking and creeping. Varying shares of smaller vehicles affect queue formation and discharge characteristics, and have significant impacts on roadway capacity. The model also could compute dynamic class-specific travel times at different vehicular compositions more realistically.

Predictors of Malreduction in Zone II and III 5th Metatarsal Fractures Fixed with an Intramedullary Screw: A Retrospective Analysis

Category:Midfoot/Forefoot; SportsIntroduction/Purpose:Percutaneous fixation of 5th metatarsal fractures may lead to malreduction due to improper implant selection and placement. Our aim was to test the effects of screw entry, length, and diameter on malreduction, delayed union, non-union, or refracture.Methods:We retrospectively reviewed zone II and proximal zone III 5th metatarsal fractures managed with intramedullary screw fixation. Comparisons were made between plantar cortex distraction/lateral cortex distraction and ratios of screw length, diameter, and entry point using multiple regression analysis. A further analysis was carried out between time to union and distraction in the lateral and plantar cortices.Results:Plantar and lateral gap were both correlated with entry point ratio on lateral and AP view respectively (p<0.001 for both views). We did not see an association between plantar and lateral gap with screw diameter ratio (p=0.393 for AP and p=0.981 for lateral) or screw length ratio (p=0.966 for AP and p=0.740 for Lateral). Ratio of postop/preop apex height on AP and lateral showed correlation to presence of lateral and plantar fracture gap respectively (p<0.0001). Presence of a plantar gap did have a slight influence on time to union (p=0.044). Most fractures showed radiographic union at 12 weeks (38/44 that were followed until union). There were no refractures or nonunions as per available records.Conclusion:Our study shows that screw length and diameter did not lead to significant plantar or lateral fracture site distraction. However, entry point had a significant effect on plantar and lateral gap on post-operative x-ray. Patients with a plantar gap did have an increased risk of delayed union. Entry point should be given more significance rather than screw diameter and length in managing zone 2/3 fifth metatarsal base fractures. This is contradictory to existing radiologic studies.

Dynamic performance of six-axle locomotive subjected to asymmetric brake shoe forces

To research the influence of asymmetric brake shoe forces(ABSF) induced by braking failure on the dynamic performance of six-axle locomotive, the static equilibrium model of three-axle bogie and dynamic model for locomotive are established. The coupling vibration equations of axle hung motor and wheelset are derived. For the air braking, the influence mechanism of ABSF on the wheel-rail asymmetric motion and force characteristics are discussed. It can be found that if the ABSF is applied in the front wheelset, all the wheelsets move laterally in the same direction. Once the ABSF occurs in the middle or rear one, other wheelsets may move laterally towards the opposite direction. The motion amplitude and direction of all wheelsets strictly depend on the resultant moment of suspension yawing moment and brake shoe asymmetric moment. For the asymmetric braking, the free lateral gap of axle-box could increase the wheelset motion amplitude, but could not change the moving direction. In both the straight line and curve, the ABSF may lead to wheelset misaligning motion, intensify the wheel-rail lateral dynamic interaction and deteriorate wheel-rail contact state. Especially for the steering wheelsets, the asymmetric braking increases the wheelset attack angle significantly, which forms the worst braking condition.

Greater postoperative relatively medial loose gap at 90° of flexion for varus knees improves patient-reported outcome measurements in anatomical bi-cruciate retaining total knee arthroplasty

BackgroundThe purpose of the present study was to measure the intraoperative joint gap using tensor device and pre- and, postoperative joint stability at 0, 30 and 90° of flexion using stress radiography and to identify whether these factors influence patient-reported outcome measurement (PROM) in anatomical bi-cruciate retaining (BCR) knee arthroplasty (TKA). MethodsFifty-three knees with preoperative varus osteoarthritis of the knee underwent anatomical BCR TKA with oblique three-degree angle femorotibial joint line. The intraoperative medial and lateral joint gap using a tensor device and gap difference (lateral minus medial; varus laxity) were also calculated. Postoperative joint stability was measured using stress radiographs. PROM was also evaluated at 1.5 years postoperatively. The effect of intraoperative and postoperative joint stabilities on PROMs were analyzed using Spearman's rank correlation analysis. ResultsIntraoperative greater difference between medial joint gap at 140° and 0° of flexion showed significant positive correlation with postoperative function of patellofemoral joint. Intraoperative varus laxity at extension improved postoperative symptoms in 2011 Knee Society Score (2011 KSS); greater postoperative lateral stability at 30 and 90° of flexion with the varus stress test was associated with the better patient expectation in 2011 KSS. Postoperative medial laxity at 90° of flexion with the valgus stress test positively correlated with the patient expectation and satisfaction in 2011 KSS. ConclusionsSurgeons should notice that the postoperative lateral stability and medial laxity at 90° of flexion improved PROM in anatomical BCR TKA.

Predictors of Malreduction in Zone II and III Fifth Metatarsal Fractures Fixed With an Intramedullary Screw.

Proper implant selection and placement is crucial during fixation of zone II and III fifth metatarsal fractures to avoid postoperative complications. This study examined the effects of screw parameters and placement on malreduction, delayed union, nonunion, and refracture rate. A retrospective review of zone II and proximal zone III fifth metatarsal fractures managed with intramedullary screw fixation was conducted. Comparisons were made between cortex distraction (gap) and ratios of screw length, diameter, and entry point. Further analysis was carried out between time to union and distraction in the lateral and plantar cortices. The plantar and lateral gaps were both associated with the mean entry point ratio on the lateral and anteroposterior (AP) views (P < .001 for both views). No association between the plantar and lateral gaps and the screw diameter ratio (P = .393 for AP and P = .981 for lateral) or the screw length ratio (P = .966 for AP and P = .740 for lateral) was identified. The ratio of postoperative to preoperative apex height on AP and lateral views was correlated with the presence of lateral and plantar fracture gaps (P < .001). The presence of a plantar gap was associated with increased time to union (P = .022). A majority of fractures showed radiographic union at 12 weeks (38/43). Only 5 of 38 patients had delayed union. There were no refractures or nonunions as per available records. Plantar or lateral fracture site distraction (gap) was not influenced by screw diameter ratio or screw length ratio. The entry point ratio had a significant effect on plantar and lateral gaps on postoperative radiographs, with lateral and inferior placement leading to fracture site distraction. Patients with a plantar gap did have an increased risk of delayed union. The results of this study emphasize the significance of the entry point when managing zone II and III fifth metatarsal base fractures. Level IV, case series.

Nanoindentation of bio-inspired graphene/nickel nanocomposites: A molecular dynamics simulation

In this paper, nanoindentation on graphene/nickel nanocomposites with a three-dimensional “brick-and-mortar” structure is studied by molecular dynamics (MD) simulation method. The effects of various geometrical variations on mechanical properties are investigated, including the length of graphene layer, the interlayer distance of two adjacent graphene layers, and the lateral gap size of adjacent graphene in each layer. The simulation results show that the addition of graphene sheets can effectively block the dislocation propagation. The strength and hardness of the bio-inspired nanocomposites decrease with the increase of the length of graphene layers, while the increase in the length of the graphene layer can avoid dislocations nucleation at the end of the graphene sheet. As the lateral gap of graphene increases, the strength of the material decreases, and dislocations are easier to pass through the gap. In the absence of defects, as the lateral gap increases, the strength becomes larger, and the hardness is not obviously affected. This result is expected to be helpful for the preparation of graphene/metal nanocomposites with extremely enhanced mechanical properties.

Clinical outcomes of using contralateral-side laterally bent intramedullary nails in atypical femur fractures with femoral bowing.

This study aimed to evaluate the clinical outcomes of using contralateral-side laterally bent intramedullary nails (IMNs) in bowed atypical femur fractures (AFFs). We retrospectively reviewed bowed AFFs treated with contralateral-side laterally bent IMNs. In total, 20 patients with 25 cases of AFFs were included. Surgical outcomes including bone union time, complications, femoral bowing, and leg length discrepancy (LLD) were evaluated. We evaluated the surgical safety of performing contralateral-side intramedullary nailing with its intraoperative and postoperative complications and compared the LLD. The average age was 76.8years (range 67-86years), and all of patients were female. There were 10 cases of complete AFFs and 15 cases of incomplete AFFs. Fourteen patients (70%) had a history of bisphosphonate (BP) use with an average of 74.5months of its use. In the complete AFF cases, reduction of the fractures was tried to restore the patients' normal anatomical geometry. The average lateral gap was 0.6mm (0-1mm), and the average medial gap was 1.6mm (1-3mm). All cases achieved bone union without secondary intervention. There were no intraoperative fractures or postoperative complications. The average bone union time was 22.0weeks and 9.2weeks in complete and incomplete AFFs, respectively. The average preoperative femoral bowing seen in the coronal and sagittal planes was 10.1° and 16.1°, respectively, while the average postoperative bowing was 6.6° and 11.3°, respectively. The average change of angle was 3.5° in the coronal plane and 4.8° in the sagittal plane. The mean change of LLD was 5.7mm. The use of contralateral-side laterally bent IMNs in treating bowed femurs showed excellent clinical outcomes without complications. In severely bowed femurs, this technique can be safe and useful.

Experimental study on fabricating micro-holes in DD5 single-crystal nickel-based superalloy using electrical discharge drilling

The single-crystal superalloy materials have been rapidly developed and widely used in advanced thermal structural components due to their excellent comprehensive physical and chemical properties under high-temperature service conditions. However, conventional micro-hole making results in defects such as edge breakage and burr. In this study, the electrical discharge drilling (EDD) combined with helical microelectrode is first adopted to fabricate DD5 single-crystal nickel-based superalloy. The effects of tool geometry and machining parameters on subsurface damage layer, micro-hole taper, surface morphology, surface roughness and machining time were investigated in detail. Experimental results indicated that helical microelectrode can obtained smoother surface without debris deposition and thinner subsurface damage layer depth lack of micro-cracks compared with cylindrical microelectrodes. Additionally, the computational fluid dynamics model was developed to analyze working fluid movement and reveal effective debris removal mechanism of helical microelectrode. The vortices will be generated in lateral gap fluid between micro-hole and helical microelectrode and have a certain delay time. The surface roughness and dimensional precision of micro-holes fabricated by helical micro-electrodes are greatly improved and machining efficiency is also improved by 30.94% compared to cylindrical microelectrodes. This work could provide theoretical and process guidance to assist in realizing high surface quality and low subsurface damage of micro-holes obtained with EDD process.

The Influence of Posterior Cruciate Ligament Resection on Tibiofemoral Joint Gap in Varus Osteoarthritic Knees.

Posterior cruciate ligament (PCL) resection during posterior-stabilized total knee arthroplasty (PS-TKA) has been reported to preferentially increase the tibiofemoral joint gap in flexion compared with extension. However, previous assessments of the joint gaps have been performed after bone resection and medial soft tissue release. Thus, these procedural steps may have the potential to influence soft tissue balance. In native knees, soft tissue laxity is generally greater in the lateral compartment than in the medial compartment both with the knee in extension and in flexion. Some surgeons may retain this natural soft tissue balance with less aggressive medial release during TKA. We performed this study to evaluate the impact of the PCL resection on the extension and flexion gaps in the absence of bone resection or medial soft tissue release. Tibiofemoral joint gaps for 41 patients (10 males and 31 females) in full extension and at 90 degrees of flexion both before and after the resections of both the anterior cruciate ligament (ACL) and PCL were assessed using a ligament tensioner device. The statistical analyze was performed using the Mann-Whitney U test. The results showed that medial gap in extension and flexion were 6.7 ± 1.0 and 7.3 ± 0.9 mm, and lateral gap in extension and flexion were 7.6 ± 1.1 and 8.4 ± 1.6 mm, respectively. Thus, physiological tibiofemoral gaps just after knee arthrotomy were trapezoidal and asymmetric shape with the significantly wider gaps in lateral and flexion, compared with the medial and extension, respectively (p < 0.05). However, the increases of the gaps with the ACL and PCL resections were less than 1 mm under the existence of medial soft tissues. As the medial collateral ligament is the primary restraint for the valgus instability, it was also considered to prevent the increase of the flexion gap although the PCL-which is the secondary restraint for the valgus instability-was resected. This finding is critically important for orthopedic surgeons applying PS-TKA implants, particularly for preserving soft tissues to achieve natural knee kinematics postoperatively.

Improvement of machining accuracy in EDCM by enhanced electrochemical reaming based on a non-metallic backing layer

Electrochemical Discharge Machining (ECDM) is potentially applicable for the fabrication of film-cooling holes. However, It is extremely difficult for the holes to achieve higher precision and machining quality owing to the working liquid diminish in the lateral machining gap. In this study, a non-metallic backing layer was proposed to overcome the diminish of working liquid, and the electrochemical reaming, as a post-processing method for ECDM, was used to further improve the machining accuracy and quality of the holes. First, the three-dimensional morphology of the melted pit of a paraffin backing layer was scanned to obtain the geometric parameters. Then, simulation analysis and experimental verification of auxiliary flushing by using the non-metallic backing layer were performed. The machining performance of the holes machined with electrochemical reaming based on non-metallic backing layer was confirmed by the observations of the surface topography of the hole wall and orifice, measurement of the orifice precision, and analysis of the element composition on the surface of the orifice wall. Finally, an optimum combination of machining parameters for electrochemical reaming is obtained through a process parameter optimization experiment.

Medial Compartment Gap Is Decreased During Forced Marching And Running Load Carriage Tasks

Medial compartment cartilage thickness can provide an indication of early stage osteoarthritis (OA), so determining tibiofemoral joint space during dynamic loading tasks is an important step in investigating potential long-term joint degeneration. Women experience higher rates of knee OA than men and military personnel are at an even greater risk, so understanding how military-relevant load carriage tasks will affect tibiofemoral arthrokinematics in a female population is of great importance in order to inform training strategies and prevent injury. PURPOSE: The purpose of the study was to determine the effects of load carriage and locomotion pattern on tibiofemoral dynamic joint space. METHODS: Twelve physically active females (age: 24.5±2.4 years) walked (WK), ran (RN), and force marched (FM, or walking at a high velocity) on a treadmill while unloaded (bodyweight, or BW) and while loaded with an additional +25%BW or +45%BW (14.3±2.0 kg, 25.6±3.5 kg). Synchronized biplane radiographs of the right knee were collected at 150 images/second for 1 second during each movement trial. A validated model-based tracking system determined femur and tibia motion (accuracy: 0.9°, 0.7 mm). Subchondral bone distances were calculated. Two-way RMANOVA with post-hoc Bonferroni correction were used to analyze the interactions and within-subjects effect of load (BW, +25BW, +45%BW) and percent of right leg support (0%, 10%, 20%, 30%) on minimum medial and lateral compartment gap during WK, RN, and FM, independently (α=0.05). RESULTS: No significant interactions were observed between load and percent support. Medial and lateral gap was lower at initial contact vs. 10% and 20% support for FM (Medial: 38%, 33% decrease, Lateral: 26%, 23% decrease). Medial gap was 23% lower at 30% vs. 20% support for FM. For RN, medial gap was lower at 30% support vs. 10% and 20% (35%, 19% decrease). No significant changes in joint space were observed for lateral RN or medial/lateral WK. No significant differences due to load were observed. CONCLUSION: Changes in knee dynamic joint space appear to be more sensitive to differences in knee kinematics rather than additional load magnitude and suggest kinematics plays a vital role in knee cartilage loading and potentially the development of OA. Supported by the Freddie Fu Student Research Grant.

Electrochemical machining of a rhombus hole with synchronization of pulse current and low-frequency oscillations

Abstract Metal gratings with rhombus holes are widely applied in lightweight aircraft components. Electrochemical machining (ECM) is a nontraditional processing technology with no tool loss and no thermal deformation that has unique advantages for the high-quality processing of rhombus holes. However, the flow paths of the electrolyte in the lateral gap are quite different, and stray corrosion easily occurs on the sidewall due to the different diagonal lengths of a rhombus hole. In this paper, a method was proposed to improve the flow field and processing localization by the synchronization of the pulse power supply and low-frequency oscillations. The on and off positions of the pulse power supply are symmetrical with respect to the wave trough of the oscillation waveform. Based on the coupled simulation of the gas-liquid two-phase flow field and electric field, the effects of assisting oscillations and synchronization of the pulses and oscillations on the void fraction, electrical conductivity, current density, dissolution rate and evolution of the anode profile were investigated. Moreover, the effects of assisting oscillations and synchronization of the pulses and oscillations on the lateral gap, sidewall slope, machining fillet and surface quality were experimentally studied. The experimental results of different ECM methods showed that the coupled simulation was effective and feasible. Moreover, the simulation analysis and experimental results both revealed that the processing accuracy and surface quality of a rhombus hole could be improved by using the synchronized ECM method. The lateral gap at the rhombus hole entrance was only 0.13 mm, the sidewall slope was 0.026 and the surface roughness was Ra0.134 μm under the optimized parameters.

A two-sided lateral gap continuum model and its numerical simulation for non-lane based heterogeneous traffic environment

The objective of this study is to model the complex behavior of non-lane based heterogeneous traffic which is predominantly occupied by vehicles with varying physical and dynamical characteristics and their staggered car following behavior. This study proposes a new continuum model by considering the properties of two-sided lateral gap in a non-lane based heterogeneous traffic stream. The model is built on a strong empirical background and modified car following theory. In particular, the model consists of density dependent disturbance propagation speed, viscosity term and a frictional clearance term to describe the complex vehicular interactions in a traffic stream. Viscosity term in the model represents the driver’s reaction to a sudden change in density and further, it helps in smoothening out the shock fronts. Frictional clearance term in the model considers the effect of slow moving vehicles on the dynamics of fast moving vehicles. The results of mathematical and numerical analysis show that the proposed model satisfies all the qualitative and physical properties of the real world system. Moreover, two sided lateral gap in the model improves the stability region of traffic flow and increases the capacity and density of traffic stream. In addition, it is able to dissipate the traffic perturbation rapidly when compared to one-sided lateral gap model. It is anticipated that the new model provides the basis for evaluating alternative transport policy measures and helps in analyzing the system performance in the future.

Can isolated removal of osteophytes achieve correction of varus deformity and gap-balance in computer-assisted total knee arthroplasty?

The aims of this study were to determine the effect of osteophyte excision on deformity correction and soft tissue gap balance in varus knees undergoing computer-assisted total knee arthroplasty (TKA). A total of 492 consecutive, cemented, cruciate-substituting TKAs performed for varus osteoarthritis were studied. After exposure and excision of both cruciates and menisci, it was noted from operative records the corrective interventions performed in each case. Knees in which no releases after the initial exposure, those which had only osteophyte excision, and those in which further interventions were performed were identified. From recorded navigation data, coronal and sagittal limb alignment, knee flexion range, and medial and lateral gap distances in maximum knee extension and 90° knee flexion with maximal varus and valgus stresses, were established, initially after exposure and excision of both cruciate ligaments, and then also at trialling. Knees were defined as 'aligned' if the hip-knee-ankle axis was between 177° and 180°, (0° to 3° varus) and 'balanced' if medial and lateral gaps in extension and at 90° flexion were within 2 mm of each other. Of 50 knees (10%) with no soft tissue releases (other than cruciate ligaments), 90% were aligned, 81% were balanced, and 73% were aligned and balanced. In 288 knees (59%) only osteophyte excision was performed by subperiosteally releasing the deep medial collateral ligament. Of these, 98% were aligned, 80% were balanced, and 79% were aligned and balanced. In 154 knees (31%), additional procedures were performed (reduction osteotomy, posterior capsular release, and semimembranosus release). Of these, 89% were aligned, 68% were balanced, and 66% were aligned and balanced. The superficial medial collateral ligament was not released in any case. Two-thirds of all knees could be aligned and balanced with release of the cruciate ligaments alone and excision of osteophytes. Excision of osteophytes can be a useful step towards achieving deformity correction and gap balance without having to resort to soft tissue release in varus knees while maintaining classical coronal and sagittal alignment of components. Cite this article: Bone Joint J 2020;102-B(6 Supple A):49-58.

A geometric ratio to predict the flexion gap in total knee arthroplasty.

Measured resection is a common technique for obtaining symmetric flexion and extension gaps in posterior-stabilized (PS) total knee arthroplasty (TKA). A known limitation of measured resection, however, is its reliance on osseous landmarks to guide bone resection and component alignment while ignoring the geometry of the surrounding soft tissues such as the medial collateral ligament (MCL), a possible reason for knee instability. To address this clinical concern, we introduce a new geometric proportion, the MCL ratio, which incorporates features of condylar geometry and MCL anterior fibers. The goal of this study was to determine whether the MCL ratio can predict the flexion gaps and to determine whether a range of MCL ratio corresponds to balanced gaps. Six computational knee models each implanted with PS TKA were utilized. Medial and lateral gaps were measured in response to varus and valgus loads at extension and flexion. The MCL ratio was related to the measured gaps for each knee. We found that the MCL ratio was associated with the flexion gaps and had a stronger association with the medial gap (β = -7.2 ± 3.05, P < .001) than with the lateral gap (β = 3.9 ± 7.26, P = .04). In addition, an MCL ratio ranging between 1.1 and 1.25 corresponded to balanced flexion gaps in the six knee models. Future studies will focus on defining MCL ratio targets after accounting for variations in ligament properties in TKA patients. Our results suggest that the MCL ratio could help guide femoral bone resections in measured resection TKA, but further clinical validation is required.

Navigated, soft tissue-guided total knee arthroplasty restores the distal femoral joint line orientation in a modified mechanically aligned technique.

To investigate the femoral component alignment in patients undergoing soft tissue-guided, navigated total knee arthroplasty (TKA). It was hypothesized that with a mechanically aligned tibial component, the soft tissues tensioned and symmetric medial and lateral gaps in flexion/extension, the femoral component would be aligned to the preoperative distal femoral joint line, as measured on knee radiographs. Between 2015 and 2017, 77 patients (78 knees) underwent navigated soft tissue-guided TKA at a single centre. Pre and postoperative radiographs were collected and varus knees were taken into account. The tibial cut was performed with navigation in neutral alignment. The femoral cuts were adjusted based on tensioned soft tissues, aiming for equal medial and lateral gaps in flexion and extension. The Knee Injury and Osteoarthritis Outcome Score (KOOS) and Knee Society Score (KSS) were collected pre and postoperatively as a secondary outcome measure. A total of 58 TKAs on varus knees were assessed. On average, the femoral component was placed at 1.7° (SD 1.7) varus in the coronal plane. The comparison between the radiographic native distal femoral alignment and the orientation of the femoral component coronal cut demonstrated a statistically significant (p < 0.0001), linear inverse relationship (r = 0.5). Satisfactory knee function and excellent pain remission were demonstrated by KOOS and KSS scores at a mean of 2.8years (SD 0.5) follow-up. One TKA was revised, resulting in a 98.3% survivorship at three years. The proposed soft tissue-guided, navigated technique, aiming to preserve the integrity of the ligaments and a neutrally aligned tibial cut, provided a joint line respecting femoral coronal cut and encouraging short-term clinical results. III.

Gap balancing versus measured resection for primary total knee arthroplasty: a meta-analysis study.

To achieve the most desirable post-operative results, operation techniques and procedures for total knee arthroplasty (TKA) are highly standardized. However, debates persist whether patients having undergone a gap balancing technique (GB) perform better than those having undergone measured resection (MR) technique. Therefore, a meta-analysis study was conducted to investigate advantages of GB compared to the MR. The focus of the present study was on clinical and functional scores, radiological measurements and further complications. The present meta-analysis was conducted according to the PRISMA checklist. In November 2019, literature search was performed. All clinical studies comparing measured resection technique versus gap balancing technique for primary total knee arthroplasty were considered for inclusion. Only articles reporting quantitative data under the outcomes of interest were eligible for inclusion. The methodological quality assessment and statistical analyses were performed through the Review Manager Software version 5.3 (The Cochrane Collaboration, Copenhagen). Data from 25 clinical trials (2971 procedures) were collected. Patient baseline demonstrated a good comparability. No difference among the two cohorts was found in terms of SF-12 Mental and Physical, ROM, KSS, KSS Function, OKS, WOMAC. No difference was found in the alignment of mechanical axis and femoral rotation. During the knee motion, no difference was found between the medial and lateral gaps among the two techniques. The GB showed a significant elevated joint line (P < 0.0001), along with a longer duration of the operating time (P = 0.001). No differences were found in terms of revision surgery, aseptic loosening or prosthetic infections. GB and MR achieve similar outcomes for TKA. In the GB group, a proximalisation of the joint line and extended operating time was detected. Regarding the additional outcomes of interest, the present analysis showed comparability between both groups, MR and GB.

A gap balancing technique for adjusting the component gap in total knee arthroplasty using a navigation system

IntroductionRecently, some studies showed assessment of the component gap is important for determination of the implant-inserted condition during total knee arthroplasty (TKA). We perform the modified gap technique with adjustment of the virtual gap which estimated by computer-aided design (CAD) using navigation system. The purpose of this study was to compare the virtual gap (CAD-gap) with the actual gap after inserting a femoral trial component (Trial-gap), and examine the usefulness of the surgical technique. Materials and methodsThe subjects were 35 patients who underwent primary TKA using a navigation system and posterior-stabilized type TKA. The surgical procedure was to produce an extension gap, confirm the flexed CAD-gap on the navigation screen based on CAD data, and plan osteotomy of the femur. After osteotomy, the femoral component was inserted and the gap balance was measured. A tensor was used to adjust and measure the gap balance. Initial alignment, rotation of the femoral component, soft tissue balance in extension, final alignment after fixing all components, and the CAD- and Trial-gaps in both extension and flexion were evaluated. ResultsThe mean initial alignment angle, rotation angle of the femoral component, soft tissue balance angle and final alignment angle were 8.1 ± 4.2° varus, 3.5 ± 1.3°external rotation, 2.7 ± 2.5° varus and 0.4 ± 1.4° varus respectively. The mean medial and lateral CAD-gaps in extension were 10.8 ± 2.5 and 13.7 ± 2.5 mm, and the mean medial and lateral CAD-gaps in flexion were 12.2 ± 2.2 and 13.9 ± 2.7 mm. The equivalent Trial-gaps in extension and flexion were 10.5 ± 2.6 and 11.4 ± 3.1 mm, and 12.2 ± 2.5 and 14.4 ± 2.8 mm. The CAD- and Trial-gaps differed significantly only for lateral gaps in extension. ConclusionIn comparing the CAD-gap and the Trial-gap, only small difference was found in the lateral gap of extension. The other gaps in both extension and flexion were well maintained. We concluded adjustment of the CAD-gap during surgery using a navigation system can be used to adjust the actual component gap especially in the medial side.

Comparative Biomechanical Study Between Minimally Invasive Popliteus and LCL Reconstruction Versus LaPrade Technique

Background:Many aspects of the posterolateral corner (PLC) of the knee have been extensively studied within the past 20 years. Quantitative anatomic and biomechanical studies have demonstrated the importance of the 3 static stabilizers of the lateral side of the knee: the fibular collateral ligament, the popliteus tendon, and the popliteofibular ligament. There are various methods of reconstruction. However, currently, there is no consensus on the preferred reconstruction technique for treating patients with chronic PLC injuries. We have developed a new reconstructive technique for PLC based on tibiofibular-based technique, similar to LaPrade, and this technique is less invasive than the previous techniques.Hypothesis:There is no difference between minimally invasive popliteus and LCL reconstruction and LaPrade’s method in restoring the posterolateral stability of kneesMethods:Six paired fresh-frozen cadaveric knees were assessed in the intact state and then dissected to simulate a grade III posterolateral knee injury. By using a “Blocked randomization”, each paired knee was randomized into 2 groups (1) reconstruction via LaPrade’s method, (2) minimally invasive popliteus and LCL reconstruction. Biomechanical testing using varus stress radiographs was performed to compare knee stability between 2 groups.Results:This study included six paired knees, three males and three females. The mean age of the cadaver was 70.8 years (range 57-85 years). No difference was found in the demographic data (sex distribution, lateral opening gap of intact knee and side-to-side difference of lateral opening gap of sectioned knee) between the 2 groups. The side-to-side difference in lateral joint opening on the varus stress radiographs significantly improved after PLC reconstruction in both groups (p <0.001, p <0.001), However, there were no differences between the 2 groups in side-to-side difference of lateral opening gap after reconstruction (Mean difference=-0.05 (95%CI, -0.46 to 0.36); p- value=0.039).Conclusion:Biomechanically, minimally invasive popliteus and LCL reconstruction is equivalent to LaPrade’s technique in restoring the stability of knees in case of grade III PLC injury. Additionally, this technique is less invasive than all traditional open technique of PLC reconstruction. The minimally invasive popliteus and LCL reconstruction technique may be a treatment option for grade III PLC injury. Keywords: posterolateral corner; ligament reconstruction; popliteus tendon; lateral collateral ligament; popliteofibular ligament; knee biomechanics; minimally invasive surgery

Result of posteromedial capsule and superficial medial collateral ligament release on gap and alignment in total knee arthroplasty in varusknee deformity by computer assisted surgery measurement: a retrospective stud

Soft tissue release and gap balancing in total knee arthroplasty (TKA) are important issue and lack of conclusive result. We performed posteromedial capsule (PMC) and superficial medial collateral ligament (sMCL) release by preservation of anterior attachment of pes anserine. Gaps and alignment were recorded by computer assisted surgery measurement.Results:T: The mean correction of varus deformity after PMC release and sMCL release were 4.88 ± 2.82° and 3.39 ± 1.7 respectively with the mean FC after PMC and sMCL release correction of 5.57 ± 3.5 and 1.34 ± 2.9° respectively. The mean medial gap changes on full extension after PMC and sMCL release was 1.83 ± 1.39 and 1.67 ± 1.04 mm. respectively with the mean medial gaps at 90 degree flexion after PMC and sMCL release changes of 0.73 ± 0.9 and 5.14 ± 2.11 mm. respectively. The mean lateral gap changes on extension after PMC and sMCL release were -1.3 ± 1.83 and -1.1 ± 1.6 mm. respectively with the mean lateral gaps at 90 degree flexion after PMC and sMCL release changes of -0.19 ± 1.03 and 0.06 ± 1.75 mm. here were 21 patients (16 female and 5 male) with mean age of 68 (48-78) years. The mean body mass index was 28.49 (20.70 – 39.95) kg/m2. The mean preoperative hip-knee-ankle angle was varus 8.12 (3.5-16.0) degrees with mean flexion contracture of 11.3 (3.5-16.0) degrees. Sixteen knees were implanted with Fixed bearing knee prosthesis and five knees were implanted with Mobile bearing knee prosthesis (Table.1). We performed PMC release in all patients, and combined PMC and sMCL release in fourteen patients. The mean correction of varus deformity after PM release and sMCL release were 4.88 ± 2.82 and 3.39 ± 1.7 degrees respectively. While the mean correction of flexion contracture after PMC release and sMCL release were 5.57 ± 3.5 and 1.34 ± 2.9 degrees respectively (Fig.8). The mean medial gaps change on extension after PMC and sMCL release were 1.83 ± 1.39 and 1.67 ± 1.04 mm. respectively. The mean medial gaps change at 90 degree flexion after PMC and sMCL release were 0.73 ± 0.9 and 5.14 ± 2.11 mm. respectively (Fig.9). The mean lateral gaps change on extension after PMC and sMCL release were 1.3 ± 1.83 and -1.1 ± 1.6 mm. respectively. The mean lateral gaps change at 90 degree flexion after PMC and sMCL release were -0.19 ± 1.03 and 0.06 ± 1.75 mm. (Fig.9). There is no instability of knee after PMC and sMCL release.Materials and Methods:Twenty one patient had been operated on. TKA with computer assisted surgery was performed using PMC and sMCL release by preservation of anterior attachment of pes anserine. Alignment, medial and lateral gaps were measured by computer assisted surgery. The mean age was 68 (48-78) years with the mean preoperative hip-kneeankle angle of 8.12 (3.5-16.0) degrees and the mean flexion contracture (FC) of 11.3 (3.516.0) degrees.Conclusion:We believe that sMCL release with preservation of anterior attachment of pes anserinus in total knee arthroplasty has additional effect on varus knee correction after PMC release without creation of knee instability.