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The strong genetic and clinical overlaps between spondyloarthritis (SpA) and inflammatory bowel disease (IBD) have placed much needed focus on the gut-joint axis of inflammation in SpA, leading to three key hypotheses that attempt to unravel this complex relationship. The arthritogenic peptide hypothesis and the aberrant cellular trafficking hypothesis have been put forth to rationalize the manner by which the innate and adaptive immune systems cooperate and converge during SpA pathogenesis. The bacterial dysbiosis hypothesis discusses how changes in the microbiome lead to architectural and immunological consequences in SpA. These theories are not mutually exclusive, but can provide an explanation as to why subclinical gut inflammation may sometimes precede joint inflammation in SpA patients, thereby implying a causal relationship. Such investigations will be important in informing therapeutic decisions which may be common to both SpA and IBD. However, these hypotheses can also offer insights for a coincident inflammatory relationship between the gut and the joint, particularly when assessing the immunological players involved. Insights from understanding how these systems might affect the gut and joint differently will be equally imperative to address where the therapeutic differences lie between the two diseases. Collectively, this knowledge has practical implications in predicting the likelihood of IBD development in SpA or presence of coincident SpA-IBD, uncovering novel therapeutic targets, and redesigning currently approved treatments. It is evident that a multidisciplinary approach between the rheumatology and gastroenterology fields cannot be ignored, when it comes to the care of SpA patients at risk of IBD or vice versa.

This study aims to solve problems caused by misalignments between exoskeleton systems and the human body. Misalignments interfere with the achievement of the wearer’s motion intention by generating unintended interaction forces between the wearer and the exoskeleton system. Therefore, this study attempts to overcome this problem by applying an additional degree of freedom (DOF) to the fixation of the human body. First, we analyzed a system of a human body and exoskeleton connected by serial chains. Second, we derived all possible DOF sets for a 7-DOF exoskeleton system and determined the final DOF set based on practical applicability. Finally, we measured the interaction forces generated during the operation of the exoskeleton system to verify the effects of the fixation mechanism. The significance of the results was confirmed by a t test with a significance level of p ≤ 0.05.

In this paper, a 7R spatial linkage for ankle rehabilitation was proposed. Thanks to its kinematic geometry, the output joint, which is accommodated by the patient’s ankle, of the linkage can possess an arbitrary joint axis at any configuration. This advantage allows the patient achieving a flexible ankle motion in 3-D space while performing the rehabilitation exercise. The design concept of the 7R linkage is explained, and the displacement and force relationships between the input and output joints (i.e., the motor and patient’s ankle) are analyzed through an equivalent RSSR linkage. A prototype is built to validate the proposed design concept.

The forefoot functions as the base of support during late stance, rotating about the dual-axis of the metatarsophalangeal joints. Previous research has shown that joint axis definition affects estimated joint moments about the forefoot. However, little is known about how metatarsophalangeal joint center definition affects estimated joint kinetics. This study compared moments about the metatarsophalangeal joint using four different defined joint centers. There was a significant difference (p .001) in peak moments between joint center definitions, differing by up to 0.488 N-m/kg for the slow and 0.878 N-m/kg for the fast running speeds tested. Additionally, there was a significant difference (p .001) for when peak plantar flexor moment occurred during the slower running condition. The more posteriorly oriented joint centers resulted in higher moments and earlier onset of the plantar flexor moment. In addition to careful modeling of the metatarsophalangeal joint axis, it is recommended that joint center definition should be considered as well.

Background Revision rates after total ankle replacements (TARs) are higher compared with other total joint replacements. The present study aimed to establish a new patient-specific implantation (PSI) technique for TAR. Material and methods A total of 10 complete Caucasian cadaver legs had whole leg computed tomography scans. The individual geometrical ankle joint axis was determined, and based on this axis, the position of the prosthesis was planned. We assessed prosthesis placement, guiding block position, and preoperative and postoperative ankle rotational axes. Results The guiding block position interobserver reliability was 0.37 mm 0.45 (mean ± SD) for the tibial guiding block. The value for the first talar guiding block was 1.72 ± 1.3 mm and for the second talar guiding block, 0.61 ± 0.39 mm. The tibial slope as well as the frontal angles of the anatomical tibial axis compared to the tibial and talar articular surfaces showed no statistically relevant differences with numbers available. The deviation of the assessed preoperative joint axis to the postoperative joint axis was 14.6° ± 7.8. Conclusion The present study describes the results of an establishing process of a new PSI technique for TAR. The reliability of guiding block positioning and, thereby, prosthesis placement is sufficient. Level of Evidence: Biomechanical study

Estimating the functional knee axis (FKA) is crucial to correctly implanting a prosthesis and accessing joint kinematics. The correct estimation of the patient-specific joint axis of the knee is crucial for achieving a reliable assessment of musculoskeletal kinematics and dynamics Researchers have reported on the KFA mainly with regard to manual management of flexion-extension movements performed passively without any voluntary actions. Active touch and movement refer to what is ordinarily called touching—variations in skin stimulation caused by surfaces are altered together by motor activity variations. This fact is worth noting because it is often neglected that locomotion and its surfaces form an inseparable pair. The objective of this study was to confirm the distinction between touching and being touched. We were particularly interested in measuring the instantaneous axes of the knee (IAK) during locomotion. We propose the invariant structure of the knee as an attempt to distill a kind of higher-order simplification of a knee model relative to the enormous complexities of the biological systems of a human joint. This principle attempted to distill a kind of higher-order simplification relative to the enormous complexities of analytical anatomical objects and the practice of biomechanical engineering, which are sometimes confused.

The Salto Talaris Total Ankle System prosthesis is an anatomically designed fixed-bearing prosthesis available in the United States based on the successful design of the Salto Mobile Version prosthesis available outside the United States. The Salto Talaris XT Primary and Revision Total Ankle System prosthesis is a flat-top version of the Salto Talaris Total Ankle System talar component and also includes thicker ultra-high molecular weight polyethylene insert options to allow for complicated primary and revision total ankle replacements to be performed. For each system, the original mobile-bearing morphology has been redesigned and mobile-bearing concept was transferred to the precision instrumentation at the trial phase evaluation for the fixed-bearing version. Instrumentation and technique allow the surgeon to determine the functional joint axis prior to final implantation. Both systems have updated instrumentation to reduce operating room time, an extended XL tibial tray to provide complete tibial plafond coverage, and a size 0 talar component for smaller individuals. The Salto Talaris Total Ankle System and Salto Talaris XT Primary and Revision Total Ankle System designs blend minimal bone resection and optimize surface area, cortical contact, and ultra-high molecular weight polyethylene conformity. In this chapter, the surgical techniques for both systems are reviewed step-by-step and pearls for successful application of both systems are provided.

Through the realization of complex trajectory motions and multi-layer material shooting, camera robot can be an important tool for film and television shooting. At present, the trajectory planning of camera robot needs to be plotted in advance by professions, and it has not been easy to adjust on site. In addition, on the actual shooting scene, it’s required to adjust running speed of the robot to meet the performance and rhythm of the actors. This paper presents a robot control schema using real-time tracking for unknown trajectories, and real-time stepless speed regulation for existing trajectories. It mainly includes data reading strategies and motion parameter protection algorithms. The response time is within 25 ms. When the real-time target position exceeds the limit of the joint axis servo capability, the robot approaches the target at the maximum speed that can be realized on its own. Furthermore, the schema for tracking functions and speed regulated reproduction have been already realized on the camera robot physical prototype.

Transfemoral prosthetic users have motor functional impairments during running. A major impairment is unintended prosthetic knee flexion during weight bearing on the prosthetic side. Therefore, the present study aims to develop a passive mechanism for a transfemoral prosthetic knee to prevent flexion during the prosthetic stance phase. The proposed mechanism has a single axis for prosthetic knee flexion–extension. The shaft that functions as the prosthetic knee joint axis can move 3 mm along the long axis of the shank part to change functions between the stance and the swing phase. The prosthetic knee joint limits only flexion and allows extension possible during the stance phase. However, it rotates freely (flexion–extension) during the prosthetic swing phase. These functions of the proposed mechanism were verified using a rough prototype. The he participant with the attached prosthetic limb prototype performed level walking with habitual gait velocity on a 10 m straight walkway. The result shows that the kinematic data of the hip, knee, and ankle were similar to able-bodied gait. Moreover, the mechanism was able to mechanically limit only the flexion with compression force acting along the shank part. These proposed mechanisms and results of the preliminary trial suggest that transfemoral amputees can run safely.

Monteggia and Monteggia variant injuries are a rare entity in the adolescent trauma patient. They are still a challenge for the orthopedic surgeon because of the combination of fracture and joint dislocation in the complex anatomical and biomechanical area of the elbow. The elbow function as well as forearm rotation is dependent on anatomic fracture fixation, restoration of the bone and joint axis, and stable humeroulnar, humeroradial, and ulnoradial joints.

Objective. To analyze the results of application of modified procedure in the correction osteotomy of the shin lateral small bone in a falsely consolidated its fractures without significant destructive-dystrophic changes in tramatized ankle joint. Materials and methods. The investigation was conducted in 37 patients, 16 - men and 21 - women, with average age (38 ± 7) yrs. From the trauma moment 6-15 mo passed, (7.8 ± 1.9) mo at average. During roentgenological examination in patients with posttraumatic osteoarthrosis of ankle joint the Stages I-II in accordance to Kellgren and Lawrence were established. Correctional osteotomy have included a transverse osteotomy of lateral small bone of the shin on the level of the joint fissure, what made possible to perform a three-dimensional correction of the bone localization and to restore the interrelationship in ankle joint. Functional results were estimated in accordance to the AOFAS (American Orthopaedic Foot and Ankle Society Score) scale for ankle joint and posterior part of foot before and after surgical treatment. The progression degree of osteoarthrosis were determined in accordance to result of roentgenography with loading in accordance to classification of Kellgren-Lawrence. Average term of observation with the results analysis have constituted (1.9 ± 0.6) yrs. Results. Estimation of functional results in accordance to the AOFAS scale in borders of the follow-up term have increased from (58.7 ± 2.4) to (86.2 ± 1.8) points. During roentgenological examination in all the patients a restoration of the ankle joint axis was observed, but in 8 (21%) patients the osteoporosis Stage III was revealed, what have witnessed its progress. Conclusion. Modified procedure of the correction osteotomy of the shin lateral small bone in a its falsely consolidated fractures gives possibility to restore a congruence and biomechanical axis of the joint injured, to improve significantly its functional capacity and to slow down a progress of posttraumatic osteoarthrosis.

In this paper, we present a hybrid exoskeletal-soft glove for the application of on-axis angle sensors that can be placed close to the center of rotation of the digit joints. 3D printed exoskeletal digit segments that run medially on most digits connect to low friction bearings. Exoskeletal segments and bearings provide rigid fixation points for a variety of traditional angle sensors, while a combination of textile and rigid structure fixate exoskeletal digits to the digits and hand. Exoskeletal digits are designed modularly so that only required digits are used and to reduce difficulty in donning and doffing. On-axis measurement may prove useful in control or assessment tasks in rehabilitation. The articulation of the digits while wearing the glove is demonstrated, albeit without sensors, showing little restriction at an early stage of the design process. Exoskeletal metacarpophalangeal joints of the 3rd and 4th digits require more work as the flexion/extension joint axis is inaccessible and moves when he digits are articulated. The proposed device must be customized for an individual and will facilitate an alternative approach to existing hand posture monitoring techniques.

Background: Misalignment of an articulated ankle-foot orthosis joint axis with the anatomic joint axis may lead to discomfort, alterations in gait, and tissue damage. Theoretical, two-dimensional models describe the consequences of misalignments, but cannot capture the three-dimensional behavior of ankle-foot orthosis use. Objectives: The purpose of this project was to develop a model to describe the effects of ankle-foot orthosis ankle joint misalignment in three dimensions. Study design: Computational simulation. Methods: Three-dimensional scans of a leg and ankle-foot orthosis were incorporated into a link segment model where the ankle-foot orthosis joint axis could be misaligned with the anatomic ankle joint axis. The leg/ankle-foot orthosis interface was modeled as a network of nodes connected by springs to estimate interface pressure. Motion between the leg and ankle-foot orthosis was calculated as the ankle joint moved through a gait cycle. Results: While the three-dimensional model corroborated predictions of the previously published two-dimensional model that misalignments in the anterior -posterior direction would result in greater relative motion compared to misalignments in the proximal -distal direction, it provided greater insight showing that misalignments have asymmetrical effects. Conclusions: The three-dimensional model has been incorporated into a freely available computer program to assist others in understanding the consequences of joint misalignments. Clinical relevance Models and simulations can be used to gain insight into functioning of systems of interest. We have developed a three- dimensional model to assess the effect of ankle joint axis misalignments in ankle-foot orthoses. The model has been incorporated into a freely available computer program to assist understanding of trainees and others interested in orthotics.

Ankle joint kinematics is mainly stabilized by the morphology of the talar dome and the articular surface of tibiofibular mortise as well as the medial and lateral ligament complexes. Because of this the bicondylar geometry of talus dome is believed to be crucial for ankle implant design. However, little data exist describing the precise anatomy of the talar dome and the talocrural joint axis. The aim of this study is to document the anatomy of the talar dome and the axis of the talocrural joint using three-dimensional (3D) computed tomographic (CT) modeling. Seventy-one participants enrolled for CT scanning and 3D talar model reconstruction. All the ankles were held in a neutral position during the CT scanning. Six points on the lateral and medial crest of the talar dome were defined. The coordinate of the six points; radii of lateral-anterior (R-LA), lateral-posterior (R-LP), medial-anterior (R-MA), and medial-posterior (R-MP) sections; and inclination angle of the talar dome were measured, and the inclination and deviation angles of the talocrural joint axis were determined. The mean values of R-LA, R-LP, R-MA, and R-MP were 19.23 ± 2.47 mm, 18.76 ± 2.90 mm, 17.02 ± 3.49 mm, and 22.75 ± 3.04 mm. The mean inclination angle of the talar dome was 9.86 ± 3.30 degrees. Gender variation was found in this parameter. The mean inclination and deviation angles were 8.60 ± 0.07 and 0.76 ± 0.69 degrees for the dorsiflexion axis and −7.34 ± 0.07 and 0.09 ± 0.18 degrees for the plantarflexion axis. Bilateral asymmetries between the medial and lateral crest of the talar dome were found, which resulted in different dorsiflexion and plantarflexion axes of the talocrural joint. Currently, no ankle implants replicate this talar anatomy, and these findings should be considered in future implant designs.

The aim was to clarify the effect of differences in the number of fiber bundles of the anterior tibial ligament (ATFL) on ankle braking function. The study sample included 81Japanese cadavers. ATFLs were categorized as: Type I with one fiber bundle; Type II with two fiber bundles that were completely separated; and Type III with three fiber bundles. Three-dimensional reconstructions of a single specimen from each category were then created. These were used to simulate and calculate ATFL strain during dorsiflexion (20°) and plantarflexion (30°) on the talocrural joint axis and inversion (20°) on the subtalar joint axis. Almost all types of superior fiber lines were stretched with dorsiflexion and plantarflexion. Regardless of Type, the inferior fiber line was shortened with plantarflexion and stretched with dorsiflexion. The inferior fiber bundle of Type III was shortened only at plantarflexion 30° and inversion 20°, but in all others it was stretched. The results suggest that Type III was weaker than Type I and Type II in terms of ankle plantarflexion and inversion braking function.

The paper presents research on one DOF (Degree of Freedom) hip joint of an exoskeleton regarding the possibilities and effects of rotation axis misalignment in the hip joint. By rotation axis misalignment, we understand the difference of alignment between the hip joint axis of rotation in human and exoskeleton; we also consider only parallel, not angular axis misalignments in our model. The proposed approach for the development of exoskeletons is to take into consideration inherent axis misalignments and analyze the possibilities to reduce their effects on the ergonomics of the device. The first step in this approach is the quantification of effects of rotation axis misalignments in exoskeletons and to achieve this, we developed the kinematic model which is presented in this paper. Most approaches focus on perfectly aligned axis of rotation, while this is not the case in our study, we focus on an acceptable misalignment for the user.

Background Despite intensive research there is no consensus about the talocrural joint axis. The aim of the present study is a new method to determinate the geometric rotational axis of the talocrural joint. Methods We analyzed 98 CT-scans of full cadaver Caucasian legs. We generated three-dimensional reconstruction models of the talus. A best fitting cone was orientated to the talar articular surface. The geometric rotational axis was defined to be the axis of this cone. Results The geometric rotational axis of the talocrural joint is orientated from lateral–distal to medial–proximal (85.6°±10 compared to anatomical tibial axis in torsional plane), from posterior–distal to anterior–proximal (81.43°±44.35 compared to anatomical tibial axis in sagittal plane) and from posterior–medial to anterior–lateral (169.2°±5.91 compared to intermalleolar axis in axial plane). Conclusions The consideration of our results might be helpful for better understanding of ankle biomechanics.

Background In the present study, CFLs harvested from cadavers were categorized according to the differences in the angle of the CFL with respect to the long axis of the fibula and their shape, and then three-dimensional reconstructions of the CFLs were used to simulate and examine the differences in the angles of the CFLs with respect to the long axis of the fibula and how they affect CFL function. Methods The study sample included 81 ft from 43 Japanese cadavers. CFLs were categorized according to their angle with respect to the long axis of the fibula and the number of fiber bundles. Five categories were subsequently established: CFL20° (angle of the CFL with respect to the long axis of the fibula from 20° to 29°); CFL30° (range 30–39°); CFL40° (range 40–49°); CFL50° (range 50–59°); and CFL2 (CLFs with two crossing fiber bundles). Three-dimensional reconstructions of a single specimen from each category were then created. These were used to simulate and calculate CFL strain during dorsiflexion (20°) and plantarflexion (30°) on the talocrural joint axis and inversion (20°) and eversion (20°) on the subtalar joint axis. Results In terms of proportions for each category, CFL20° was observed in 14 ft (17.3%), with CFL30° in 22 ft (27.2%), CFL40° in 29 ft (35.8%), CFL50° in 15 ft (18.5%), and CFL2 in one foot (1.2%). Specimens in the CFL20° and CFL30° groups contracted with plantarflexion and stretched with dorsiflexion. In comparison, specimens in the CFL40°, CFL50°, and CFL2 groups stretched with plantarflexion and contracted with dorsiflexion. Specimens in the CFL20° and CFL2 groups stretched with inversion and contracted with eversion. Conclusions CFL function changed according to the difference in the angles of the CFLs with respect to the long axis of the fibula.

The direct problem of researching the load capacity of segment gas-static bearing is being discussed. In calculation the movement of the shaft in the bearing is considered slow comparing than the rotational velocity. Vibrations and the influence of non-stationarity are neglected. The given geometry of the bearing and the pressure of lubrication supply in the gap between the bearing and the shaft are considered initial data. The result of the calculation is the value of the resultant pressure force, applied to the bearing segments. Summing the forces the value of the static load capacity can be found. For segments that may spontaneously rotate about the joint axis, described a method of calculating the rotation angle, at which the main moment of pressure forces applied to the segment is equal to zero and the segment’s position is stable.