Lever Arm Research Articles

Does upper body static stretching in warm up effect repeated sprint ability in boxers?

Boxing is a high intensity intermittent sport consisting of multiple 2 or 3 minute rounds. For a boxer to win, they must perform a higher quantity of strikes on their opponent. The mechanics of a punch draws power from the feet and lower body via rotation and ground force generation, however, the action still utilises the upper body predominantly (Beattie & Ruddock. 2022, J Strength Cond Res, 36, 2957-2969). The ability to perform repeated bouts of maximal effort with limited recovery may be indicative of success. Static ‘developmental’ stretches are suggested by England Boxing for use in post-exercise cool-down, although without detailed justification (England Boxing. 2023, Level 1 coaching handbook). Static stretching in warm-up has also been explored in other practices with mixed results (Haddad et al; 2014, J Strength Cond Res, 28, 140-146) and is yet to be researched for boxing. Arm-cranking has previously been used as a sport-specific measurement for upper body power output in amateur boxers. (Venckunas et al; 2022, J Strength Cond Res, 36, 717-722). The aim of this study is to investigate the effects of static stretching in warm-up on upper-body repeated maximal effort arm crank ability in boxers. It is hypothesised that a static stretching intervention in warm-up will improve boxers' repeated maximal effort ability. For this repeated-measures design, a sample of male “development” level boxers (England Boxing. 2023, England Boxing Development Championship) will be recruited. Following institutional ethical approval, participants will partake in 2 sessions where they will perform 7 repetitions of 6s arm-crank maximal-effort sprints separated by 13 s recovery. This time duration simulates the activity:recovery ratio and intensity of a boxing bout (Davis et al., 2017, J Strength Cond Res). Peak power (W) will be measured in each sprint, with fatigue index (FI%) and decrement score calculated to assess participant fatigue over the 7 maximal efforts. There will be a light 1-minute sport-specific warm-up (Shadowboxing) before the first session, then a week later the participants repeat the warm up but with an additional stretching intervention. The static stretches include 2 repetitions of 30 s upper-body focussed static stretches until mild discomfort (upper limbs and shoulders, back and chest) (Liguori et al., 2021, ACSM’s guidelines for exercise testing and prescription). Peak power, FI% and decrement score will be compared Pre-Post stretching intervention using paired samples t-test and Cohen’s d effect size using SPSS.

Corrective Open-wedge Valgus Proximal Humerus Lengthening Osteotomy. Technique and Case Series.

Symptomatic varus malunion after proximal humeral fractures is associated with weakness and painful limitation of shoulder range of motion. When there is conformity of the articular surface and no avascular necrosis, a head-preserving procedure is best indicated. Arthroscopic arthrolysis, subacromial decompression, and tuberoplasty have been described for the treatment of mild deformity. In cases with more severe deformity, corrective extracapsular lateral closing wedge valgus osteotomy has been reported as a reliable treatment option, in terms of both pain relief and improved function. While this procedure adequately restores rotator cuff tensioning, it is associated with a shortening of the lever arm to the deltoid muscle, secondary to a loss of humeral length. We describe our technique and results with a vascular-sparing, medial open-wedge osteotomy, using a structural allograft and lateral locking plate. In our opinion, this procedure is safe and effective, with the potential to improve functional outcomes in young and active patients.

ALMA view of the L1448-mm protostellar system on disk scales: CH3OH and H13CN as new disk wind tracers

Protostellar disks are known to accrete; however, the exact mechanism that extracts the angular momentum and drives accretion in the low-ionization “dead” region of the disk is under debate. In recent years, magnetohydrodynamic (MHD) disk winds have become a popular solution. Even so, observations of these winds require both high spatial resolution (~10 s au) and high sensitivity, which has resulted in only a handful of MHD disk wind candidates to date. In this work we present high angular resolution (~30 au) ALMA observations of the emblematic L1448-mm protostellar system and find suggestive evidence for an MHD disk wind. The disk seen in dust continuum (~0.9 mm) has a radius of ~23 au. Rotating infall signatures in H13CO+ indicate a central mass of 0.4 ± 0.1 M⊙ and a centrifugal radius similar to the dust disk radius. Above the disk, we identify rotation signatures in the outflow traced by H13CN, CH3OH, and SO lines and find a kinematical structure consistent with theoretical predictions for MHD disk winds. This is the first detection of an MHD disk wind candidate in H13CN and CH3OH. The wind launching region estimated from cold MHD wind theory extends out to the disk edge. The magnetic lever arm parameter would be λϕ ≃ 1.7, in line with recent non-ideal MHD disk models. The estimated mass-loss rate is approximately four times the protostellar accretion rate (Ṁacc ≃ 2 × 10−6M⊙ yr−1) and suggests that the rotating wind could carry enough angular momentum to drive disk accretion.

Modelling and simulation of a novel secretary bird-inspired vibration isolator

Abstract In this article, a novel secretary bird-inspired vibration isolator (SBIVI) is presented and investigated. The vibration isolator consists of an X-shaped stiffness adjustment mechanism and a lever arm structure that mimics the leg and wing of the secretary bird respectively. The biodynamics of the secretary bird is briefly introduced. The structure mapping from the body of the secretary bird to the scheme of the proposed SBIVI is analyzed. For the purpose of confirming the isolation performance of the SBIVI, the theoretical dynamics model is built while the virtual prototype simulation is carried out. By adjusting the values of the inertial mass and spring stiffness, the SBIVI can be easily installed with optimal operating conditions. From the simulation results, it is concluded that the vibration suppression ability of the SBIVI surpasses the traditional X-shaped structure within the interest of the frequency bandwidth.

Primary Stability and Fracture Resistance of Zirconia and Titanium Implants: A Paired Comparative In Vitro Study.

Compare Neodent Zi® zirconia implants' insertion torque (IT) and removal torque (RT) with Neodent Alvim® titanium. Measure the maximum torque supported by the zirconia implant until its fracture (MT) and the maximum torque sustained by the assembler of this implant (MTA) until its fracture. In this in-vitro study twenty four implants were used. Two groups of implants with the same macrogeometry and from the same manufacturer were compared, Zirconia (n=12) and Titanium (n=12). Implant bed preparations were completed in bovine ribs following a standardized drilling protocol. Then, the insertion torque (IT), removal torque (RT), maximum torque to fracture (MT) and maximum torque to fracture of the assembler (MTA) were completed using a calibrated torque meter. Data was presented using descriptive statistics including means, standard deviations (SD), medians, and quartiles. The Shapiro-Wilk test was used to verify data normality and the Wilcoxon test was used to evaluate differences between groups. Statistical significance was established as p < 0.05. Zirconia implants showed: IT 89.33 ± 31.18 Ncm and RT 84.89 ± 32.92 Ncm. Titanium implants showed: IT 77.58 ± 28.96 Ncm and RT 76.75 ± 31.29 Ncm without significant differences (p>0.05). In relation to fracture under rotational force, the zirconia implants fractured at 106.17 ± 22.54 Ncm, and the implant assembly fractured at 84.00 ±13.14 Ncm. Neodent Zi® implants showed stability but lower fracture torque than Alvim® titanium. As the fracture values of the assembler were significantly lower than the fracture values of the zirconia implants, it can be stated that, as recommended by the manufacturer, they act as a safety measure during installation.

Relative contribution of the nail and plate to a nail-plate construct for comminuted distal femoral fractures.

The purpose of this study was to assess the biomechanical contributions of the nail and the plate individually to a complete nail-plate construct in the setting of comminuted distal femur fractures. For this biomechanical study, comminuted extra-articular distal femur fractures were created in 24 synthetic osteoporotic femur models. These were then split into three groups: the nail-only group, the plate-only group, and the nail-plate group. After fixation, each specimen underwent sequential axial and torsional loading, and axial and torsional stiffness were calculated and compared. The addition of a nail to a plate-only construct increased axial stiffness by 19.7% and torsional stiffness by 59.4%. The plate-only group and nail-plate group both demonstrated significantly greater axial and torsional stiffness than the nail-only group at all levels of axial and torsional load. (p < 0.001) At 1000 and 2000 N of cyclic loading, the nail-plate group demonstrated significantly greater axial stiffness than the plate-only group (p ≤ 0.018). The nail-plate group demonstrated greater torsional stiffness than the plate-only groups at all levels of torsional loading (p < 0.001). In osteoporotic comminuted distal femur fracture models, most of the axial stiffness in a nail-plate construct comes from the plate. While the combination of the two constructs is not fully additive, the plate contributes the majority of the axial and torsional stiffness in a nail-plate construct. The supplementation of the plate with a nail primarily helps to increase resistance to rotational forces. Level of Evidence: III.

Short term follow-up of femoral neck dynamic cross screw system and threaded cannulated screw in the treatment of vertically unstable femoral neck fractures

To analyze and compare the clinical effects of femoral neck dynamic cross screw system (FNS) and cannulated screws(CS) in the treatment of vertically unstable femoral neck fractures. The clinical data and short-term follow-up results of 40 patients with vertically unstable femoral neck fractures admitted from July 2020 to August 2021 were retrospectively analyzed. According to different internal fixation methods, 40 patients were divided into two groups, 20 cases in FNS group included 11 males and 9 females with a median of 58.5(50.3, 62.5) years old, and 20 in CS group included 9 males and 11 females with a median of 52.0(40.5, 58.0) years old. The operation time, knife edge length, blood loss and treatment cost of two gruops were observed and compared. The postoperative fracture healing and internal fixation were evaluated with X-ray imaging data, and the femoral neck shortening of the affected side was measured. The incidence of thigh irritation, the time of partial weight bearing and full weight bearing, early necrosis of femoral head, reoperation revision and Harris scores were compared between two groups. FNS group was followed up for 18.0(15.0, 19.0) months, CS group for 17.0(15.0, 18.8) months. There was no significant difference in operation time, incision length and blood loss between two groups(P>0.05). The cost of diagnosis and treatment in FNS group was higher than that in CS group(P<0.001). In FNS group, there was no irritation sign of the affected side thigh, while in CS group, there were 6 cases with discomfort or irritation sign of the lateral thigh(P<0.05). The average time of partial weight bearing activity in CS group was later than that in FNS group(P<0.05); However, there was no significant difference in the activity time of complete weight bearing between two groups(P=0.011>0.05). At the last follow-up, the shortened length of the affected femoral neck in CS group was greater than that in FNS group(P<0.05). There was no early necrosis of femoral head and reoperation in both groups. There was no significant difference in Harris score between two groups 12 months after operation(P>0.05). FNS treatment of vertically unstable femoral neck fractures can significantly reduce the incidence of lateral thigh irritation sign, and effectively reduce the postoperative shortening rate of vertically unstable femoral neck fractures, which can provide a relatively stable anti rotation force and anti cutting force, so that patients can go to the ground relatively early, which is conducive to the recovery of the affected hip joint function after surgery. It is a new option for the surgical treatment of vertically unstable femoral neck fractures. However, due to the high cost of treatment, In clinical practice, appropriate surgical treatment is selected according to the actual situation.

A Systematic Review of Effects on ACL Injury of Soccer Shoe Outsoles, Soccer Playing Field Surfaces, and Outsole–Surface Interface

Soccer is a sport with a high incidence of injuries. The most common injury occurs when the anterior cruciate ligament of the knee has undergone a sprain, strain, or partial or total rupture. Besides fitness factors (e.g., proprioception, balance and strength capabilities), a principal cause of ACL injuries is sport shoes and playing surfaces. Especially with the emergence of artificial surfaces (rubbers, turfs, concrete, asphalt, red turf), the ACL injuries dramatically increase. The cost of ACL injuries is high both in terms of career termination and in social and economic costs. Thus, it is necessary to understand the impact of sport shoes and playing surfaces on the ACL and how it can be mitigated. The present literature review followed the PRISMA methodology to identify the major biomechanical factors influencing the behavior of surfaces and shoes in relation to the ACL damage. Fifty-eight papers were identified. After reviewing the mechanism of injuries, we identified several distinct factors: type of outsole and mechanical arrangement of the outsoles; shear forces; characteristics of artificial turf surfaces; effect of weather on artificial surface aging and change in mechanical characteristics; outsole/ground interface; and the frictional, tractional and rotational forces in the pathogenesis of ACL injuries in soccer.

An anteromedial stabilization procedure has the most protective effect on the anterior cruciate ligament in tibial external rotation. A human knee model study

IntroductionAnterior cruciate ligament (ACL) reconstruction remains associated with the risk of re-rupture and persisting rotational instability. Additional extraarticular anterolateral stabilization procedures stabilize the tibial internal rotation and lead to lower ACL failure rate and improved knee stability. However, data for additional stabilization of tibial external rotation is lacking and the importance of an anteromedial stabilization procedure is less well evaluated. Aim of this study is to investigate the influence of an extraarticular anteromedial stabilization procedure for the stabilization of the tibial external rotation and protection of the ACL from these rotational forces.MethodsInternal and external rotations of the tibia were applied to a finite element (FE) model with anatomical ACL, posterior cruciate ligament (PCL), lateral collateral ligament (LCL), medial collateral ligament (MCL) and intact medial and lateral meniscus. Five additional anatomic structures (Anteromedial stabilization/anteromedial ligament, AML, augmented superficial medial collateral ligament, sMCL, posterior oblique ligament, POL, anterolateral ligament, ALL, and popliteal tendon, PLT) were added to the FE model separately and then combined. The force histories within all structures were measured and determined for each case.ResultsThe anteromedial stabilization or imaginary AML was the main secondary stabilizer of tibial external rotation (90% of overall ACL force reduction). The AML reduced the load on the ACL by 9% in tibial external rotation which could not be achieved by an augmented sMCL (-1%). The AML had no influence in tibial internal rotation (-1%). In the combined measurements with all additional structures (AML, ALL, PLT, POL) the load on the ACL was reduced by 10% in tibial external rotation.ConclusionThis study showed that an additional anteromedial stabilization procedure secures the tibial external rotation and has the most protective effect on the ACL during these external rotational forces.

FLEXURAL RESISTANCE OF COMPOSITE BEAMS, EB AND NSM BONDED PLATES

Existing reinforced concrete elements may need strengthening due to increased applied loads or due to deterioration of the reinforcement bars caused by rust, reducing the cross-sectional area. This study focuses on strengthening reinforced concrete beams by adhesively bonding steel plates to different positions of the tension zone, creating composite beams. Plates were bonded horizontally to the soffit; these are referred to as externally bonded (EB) composite beams. Plates can also be placed into a vertical slot cut into the soffit; these are referred to as near-surface mounted (NSM) composite beams. A comparison was drawn in this research study between the flexural resistance predicted by the mathematical model and the experimentally measured results. The predictions of the mathematical model compared very well to the experimentally measured specimens. The EB composite beams yield mathematical results 0.41% higher than the experimental results and the NSM beams 3.69% higher than the experimental results. The experimentally tested flexural resistance of the EB beams is 11.1% higher than that of the NSM composite beams, which is expected due to the larger lever arm of the internal couple to the bonded plate. An increase of 63% in the flexural capacity of the non-plated reinforced concrete beam over that of the EB composite beams was achieved.

FLEXURAL RESISTANCE OF COMPOSITE BEAMS, EB AND NSM BONDED PLATES

Existing reinforced concrete elements may need strengthening due to increased applied loads or due to deterioration of the reinforcement bars caused by rust, reducing the cross-sectional area. This study focuses on strengthening reinforced concrete beams by adhesively bonding steel plates to different positions of the tension zone, creating composite beams. Plates were bonded horizontally to the soffit; these are referred to as externally bonded (EB) composite beams. Plates can also be placed into a vertical slot cut into the soffit; these are referred to as near-surface mounted (NSM) composite beams. A comparison was drawn in this research study between the flexural resistance predicted by the mathematical model and the experimentally measured results. The predictions of the mathematical model compared very well to the experimentally measured specimens. The EB composite beams yield mathematical results 0.41% higher than the experimental results and the NSM beams 3.69% higher than the experimental results. The experimentally tested flexural resistance of the EB beams is 11.1% higher than that of the NSM composite beams, which is expected due to the larger lever arm of the internal couple to the bonded plate. An increase of 63% in the flexural capacity of the non-plated reinforced concrete beam over that of the EB composite beams was achieved.

Creative biomechanics for complex cases

Orthodontic biomechanics play a crucial role in achieving successful outcomes, especially in complex cases requiring precise control of tooth movements. This article explores force system analysis based on the moments and forces around the center of resistance and emphasizes traditional and contemporary approaches in orthodontic biomechanics, focusing on key tooth movements such as bite opening, space closure, retraction, protraction, intrusion, and extrusion.In complex borderline cases involving nonsurgical treatment, this article addresses the significance of total arch distalization for maximum retraction, total arch intrusion for vertical control, total arch extrusion for enhancing maxillary incisor display, lever arm mechanics for achieving incisor torque control, and total arch protraction for improving the maxillary incisor show.Patient-specific factors, efficient biomechanics, and a comprehensive understanding of the limitations of treatment modalities are emphasized in pursuit of optimal orthodontic outcomes.

Clinical application of a lingual retractor with temporary anchorage devices (TADs) for patients with lip protrusion and anterior open bite

Anterior open bite (AOB) is considered one of the most difficult malocclusions to correct and achieve successful and stable results. Various treatment approaches have been proposed for the treatment of AOB in adults. Intrusion of the entire maxillary dentition is necessary for AOB patients with severe incisor exposure. In previous reports, a labial appliance with temporary anchorage devices (TADs) implanted in various positions has been used to achieve total intrusion of the maxillary dentition. This article describes the design and biomechanics of an anteroposterior lingual retractor (APLR) to attempt retraction of anterior teeth and total intrusion of maxillary dentition after premolar extraction in patients with both lip protrusion and AOB and the functions of each component of APLR is considered. When force is applied between the anterior lever arm of the APLR and a TAD in the midpalatal area, the anterior teeth are intruded and retracted with torque control. Because the direction of the APLR force and the guide bar are not parallel, intrusive force is generated in the posterior teeth. Due to this total intrusion of the maxillary dentition, the mandible is rotated counterclockwise, improving AOB with severe incisor exposure. Various cases are presented in which APLR was applied to AOB patients, and the clinical considerations behind the treatment are explained in detail.

Onset of rotating convection of a nanofluid with helical force: Stability analysis

Employing linear stability analysis of nanofluids holds promising advantages across diverse domains. The impact of rotation and helical force on the onset of convection in the nanofluid is investigated using the linear stability analysis. The method of normal modes is used to solve the governing nondimensional equations, which results in an eigenvalue problem for the linear stability analysis. The bvp4c in MATLAB R2021a is employed to solve the eigenvalue problem. Three different lower-upper boundary conditions are considered: free-free, rigid-free, and rigid-rigid. The Rayleigh and wave number are determined for various required values of the other physical parameters and graphically displayed. Specifically, as the Taylor number rises, there is a corresponding grow in the critical Rayleigh number. This indicates that higher values of the Taylor number stabilize the system, making it less prone to convective instabilities. Conversely, the Lewis number and Helical force parameter destabilize the critical Rayleigh number, making the system more prone to convective instabilities across all boundaries. This information provides valuable insights into the system’s dynamics under study and can be crucial for predicting and understanding its behavior under different conditions.

Comparison of De-Torque and Failure Load Evaluation of Selective-Laser-Sintered CoCr, CAD-CAM ZrO, and Machined Implant Abutment/Restoration.

This study aimed to compare the torque loss, fracture load, compressive strength, and failure types of selective-laser-sintered cobalt chromium (SLM-Co-Cr), computer-aided design and computer-aided manufacturing zirconium oxide (CAD-CAM-ZrO), and machined titanium (Ti) implant abutments. Thirty endosseous dental implants were vertically embedded with machined Ti (control group), CAD-CAM-ZrO, and SLM-Co-Cr abutments. Abutment fabrication involved CAD-CAM milling and SLM technology. The de-torque assessment included preload reverse torque values (RTVs), cyclic loading, and post-RTVs using a customized protocol. Fracture load assessment employed ISO-14801 standards, and statistical analysis was conducted using ANOVA and Tukey Post hoc tests (p < 0.05). In pre-load RTVs, SLM-Co-Cr showed the lowest mean torque loss (24.30 ± 2.13), followed by machined Ti (27.33 ± 2.74) and CAD-CAM-ZrO (22.07 ± 2.20). Post-load RTVs decreased for all groups. Fracture load and compressive strength were highest for SLM-Co-Cr, with significant differences among groups (p < 0.001). Fracture types included abutment failures in SLM-Co-Cr and machined Ti, while CAD-CAM-ZrO exhibited crown separation with deformation. SLM-Co-Cr-fabricated implant abutments exhibited superior stability and resistance to rotational forces, higher fracture loads, and greater compressive strength compared to CAD-CAM-ZrO and machined Ti.

A weak coupling mechanism for the early steps of the recovery stroke of myosin VI: A free energy simulation and string method analysis.

Myosin motors use the energy of ATP to produce force and directed movement on actin by a swing of the lever-arm. ATP is hydrolysed during the off-actin re-priming transition termed recovery stroke. To provide an understanding of chemo-mechanical transduction by myosin, it is critical to determine how the reverse swing of the lever-arm and ATP hydrolysis are coupled. Previous studies concluded that the recovery stroke of myosin II is initiated by closure of the Switch II loop in the nucleotide-binding site. Recently, we proposed that the recovery stroke of myosin VI starts with the spontaneous re-priming of the converter domain to a putative pre-transition state (PTS) intermediate that precedes Switch II closing and ATPase activation. Here, we investigate the transition from the pre-recovery, post-rigor (PR) state to PTS in myosin VI using geometric free energy simulations and the string method. First, our calculations rediscover the PTS state agnostically and show that it is accessible from PR via a low free energy transition path. Second, separate path calculations using the string method illuminate the mechanism of the PR to PTS transition with atomic resolution. In this mechanism, the initiating event is a large movement of the converter/lever-arm region that triggers rearrangements in the Relay-SH1 region and the formation of the kink in the Relay helix with no coupling to the active site. Analysis of the free-energy barriers along the path suggests that the converter-initiated mechanism is much faster than the one initiated by Switch II closure, which supports the biological relevance of PTS as a major on-pathway intermediate of the recovery stroke in myosin VI. Our analysis suggests that lever-arm re-priming and ATP hydrolysis are only weakly coupled, so that the myosin recovery stroke is initiated by thermal fluctuations and stabilised by nucleotide consumption via a ratchet-like mechanism.

Percutaneous intravascular micro-axial blood pump: current state and perspective from engineering view.

The utilization of a minimally invasively placed catheter-mounted intravascular micro-axial flow blood pump (IMFBP) is increasing in the population with advanced heart failure. The current development of IMFBPs dates back around the 1990s, namely the Hemopump with a wire-drive system and the Valvopump with a direct-drive system. The wire-drive IMFBPs can use a brushless motor in an external console unit to transmit rotational force through the drive wire rotating the impeller inside the body. The direct-drive IMFBPs require an ultra-miniature and high-power brushless motor. Additionally, the direct-drive system necessitates a mechanism to protect against blood immersion into the motor. Therefore, the direct-drive IMFBPs can be categorized into two types of devices: those with seal mechanisms or those with sealless mechanisms using magnetically coupling. The IMFBPs can be classified into two groups depending on their purpose. One group is for cardiogenic shock following a heart attack or for use in high-risk percutaneous coronary intervention (PCI), and the other group serves the purpose of acute decompensated heart failure. Both direct-drive IMFBPs and wire-drive IMFBPs have their own advantages and disadvantages, and efforts are being made to develop and improve, and clinically implement them, leveraging their own strengths. In addition, there is a possibility that innovative new devices may be invented. For researchers in the field of artificial heart development, IMFBPs offer a new area of research and development, providing a novel treatment option for severe heart failure.

Study on the method of transfer alignment based on the distributed inertial network of guided submunition

Aiming at the problem of poor transfer alignment accuracy between missiles with a high length-to-diameter ratio as a carrier missile and the internally carried guided submunition, this study proposes a transfer alignment method based on the distributed inertial network of the guided submunition. Initially, considering the influence of the deflection deformation of the carrier missile body and the dynamic nonlinear deformation of the lever arm on the transfer alignment accuracy, the corresponding error model is established and compensated for the sub-inertial guide velocity to improve the accuracy of the observed quantities. Additionally, in response to the high failure rate of low-cost inertial guidance systems equipped with guided submunition, we used an inertial network data fusion architecture based on the isolation of device failure monitoring, which effectively isolates the faulty data through the fusion of inertial measurements at the sensor level and optimal fusion of filtering to further improve the reliability of transmission alignment. The effectiveness of the method proposed in this paper is verified through a large number of simulation experiments. Compared with the traditional transfer alignment method between a single master inertial guide and a sub inertial guide, the method in the paper has obvious improvement in the transfer alignment accuracy. In addition, this method is not affected by the failure of inertial devices in the distributed inertial network, and can continuously maintain a high transfer alignment accuracy. For this kind of missile-borne distributed inertial network with a sub-node sets layer, it is found after comparison that: the transmission alignment error is basically the same for different slave nodes in the same sub-node sets; between different sub-node sets, the closer to the master inertial guide the transmission alignment error is smaller. This study provides a new solution idea and certain reference value for solving the problem of poor transfer alignment accuracy between missiles with a high length-to-diameter ratio as a carrier missile and the internally carried guided submunition.

Ankle Muscle Strength and Gait Function After Dorsal Closing Wedge Calcaneal Osteotomy for Haglund Exostosis-Related Heel Pain.

Haglund exostosis-related heel pain may be surgically treated with dorsal closing wedge calcaneal osteotomy (DCWCO). Recent reports on this technique show good clinical and self-reported outcomes. However, uncertainty about functional consequences related to ankle muscle strength and gait function due to a shortened Achilles tendon lever arm exists. Fifteen patients (15 feet) with Haglund exostosis-related heel pain were surgically treated with DCWCO and evaluated before and 1 year after surgery. Isometric plantar flexion and dorsiflexion strength was quantified for both the involved and the uninvolved limb. Gait analysis was performed at a self-selected walking speed using a 3D motion capture system including force plates. Self-reported outcomes (Foot Function Index and Global Treatment Outcome) were also assessed. Before surgery, as well as after surgery, plantar flexion strength of the involved limb was significantly lower compared to the uninvolved limb while dorsiflexion strength did not differ between limbs at both time points. Step length and time, ankle flexion angles, power generation, and propulsive impulses during gait did not differ between limbs both before and after surgery. Propulsive impulse and step length of the involved limb increased from pre- to postsurgery with an effect size of 1.04 and 0.48, respectively, revealing a general improvement in gait dynamics. Total Foot Function Index improved by 48% after surgery, and 80% of patients rated their surgery as "helped" or "helped a lot" (Global Treatment Outcome). In this relatively small cohort, we found that patients treated for Haglund exostosis-related heel pain with DCWCO surgery had minor interlimb differences in gait kinematics and kinetics and generally improved gait dynamics and self-reported function at 1-year follow-up. Level II, observational prospective cohort study.

Do all short stem types restore biomechanical parameters of the hip? Comparison according to femoral neck osteotomy levels.

There is no consensus on ideal short femoral stem design. A classification system proposed by Feyen and Shimmin divides short stems in two types according to femoral neck osteotomy levels: subcapital (IIIA) and standard (IIIB). The study aims to determine which design type is more successful in restoring native biomechanical parameters and whether stem type has an impact on clinical results. In this retrospective comparative study, patients that have undergone short stem hip arthroplasty were evaluated according to stem types: type IIIA (n = 52, 66.7%) (Mathys Optimys) and IIIB (n = 26, 33.3%) (Implantcast Aida and Smith & Nephew SMF). Pelvis X-rays were assessed in terms of femoral neck length, horizontal and vertical hip centres of rotation, horizontal and vertical femoral offsets, abductor lever arm lengths, leg lengths, and stem-shaft angles. Improvement in Harris hip scores, differences between post-operative and pre-operative measurements, and stem-shaft angles were evaluated and compared between two groups. Mean femoral neck resection (8.27 ± 6.68mm in IIIA and 15 ± 6.33mm in IIIB) was significantly different between both groups (p < 0.001). Harris hip scores were increased at post-operative six months in both groups with no difference (84.4 ± 6.4 and 84.6 ± 5.5, p = 0.4). The absolute values of differences between pre-operative and post-operative horizontal centres of rotation (p = 0.63), vertical centers of rotation (p = 0.75), horizontal femoral offsets (p = 0.78), vertical femoral offsets (p = 0.83), abductor lever arm distances (p = 0.63), and leg length (p = 0.21) measurements were not different between both groups. Stem positions were both varus with no statistically significant difference between groups (p = 0.14). We found no difference regarding restoration of biomechanical parameters between short stem designs with different levels of neck osteotomy. Additionally, short stem can mostly result in varus component positioning regardless of the level of neck osteotomy.