Joint Rotation Center Research Articles

Application of metal cushion block combined with Jumbo cup in reconstruction of acetabular bone defect in revision of artificial hip joint

To investigate the application effect and imaging changes of metal cushion block combined with Jumbo cup in the reconstruction of acetabular bone defect after revision of artificial hip joint. Retrospective analysis was made on the clinical data of 83 patients who underwent revision acetabular bone defect reconstruction of the artificial hip joint in our hospital from September 2019 to October 2021. They were divided into group A and group B according to different surgical methods. There were 42 patients in group A, including 26 males and 16 females, aged from 44 to 72 years old with an average of (60.57±4.62) years, who underwent revision with metal cushion block and Jumbo cup. There were 41 patients in group B, including 22 males and 19 females, aged from 42 to 71 years old with an average of (58.74±4.25) years, who underwent revision with metal cushion block and bone cement mortar cup. The operation related indexes, Harris hip function score and visual analogue scale (VAS) of pain before operation, 1 month and 12 month after operation were compared between two groups. The results of X-ray imaging examination (hip rotation center height, acetabular abduction angle, femoral eccentricity and imaging standard qualification rate) before and 12 month after operation were evaluated, and the incidence of complications was compared between two groups. There was no significant difference in operation time, intraoperative bleeding volume and postoperative drainage volume between two groups (P>0.05). Both groups were followed up for 12 to 36 months with an average of (25.36±3.59) months. The scores of pain, function, deformity and Harris' total score in the two groups at 1 month after operation were higher than those before operation (P<0.05), and the scores of pain, function, deformity, joint activity and Harris' total score in two groups at 1 year after operation were higher than those before operation and 1 month after operation (P<0.05), and the above scores in group A were higher than those in group B at 1 year after operation (P<0.05). The VAS of two groups decreased successively at 1 month and 1 year after operation (P<0.05), but there was no significant difference in both groups at each time point (P>0.05). The femoral eccentricity increased in both groups at 1 year after operation (P<0.05), and group A was higher than group B (P<0.05). The height of rotation center and acetabular abduction angle decreased in both groups at 1 year after operation (P<0.05), and the height of rotation center in group A was lower than that in group B (P<0.05), but there was no significant difference in acetabular abduction angle between two groups (P>0.05). The imaging qualification rate of group A was higher than that of group B (P<0.05). There was no significant difference in the incidence of adverse reactions between two groups (P>0.05). Metal cushion block combined with Jumbo cup in the treatment of acetabular bone defects can provide the hip joint function, and restore the hip joint rotation center, femoral eccentricity and acetabular abduction angle, with obvious clinical effect.

Biomechanical and clinical outcomes of 3D-printed versus modular hemipelvic prostheses for limb-salvage reconstruction following periacetabular tumor resection: a mid-term retrospective cohort study

BackgroundDebates persist over optimal pelvic girdle reconstruction after acetabular tumor resection, with surgeons grappling between modular and 3D-printed hemipelvic endoprostheses. We hypothesize superior outcomes with 3D-printed versions, yet scarce comparative research exists. This study fills the gap, examining biomechanics and clinical results retrospectively.MethodsFrom February 2017 to June 2021, we retrospectively assessed 32 patients undergoing en bloc resection for malignant periacetabular tumors at a single institution. Primary outcome: limb function. Secondary outcomes: implant precision, hip joint rotation center restoration, prosthesis-bone osteointegration, and complications. Biomechanical characteristics were evaluated through finite element analysis on pelvic defect models.ResultsIn the 3D-printed group, stress distribution mirrored a normal pelvis, contrasting the modular group with elevated overall stress, unstable transitions, and higher stress peaks. The 3D-printed group exhibited superior functional scores (MSTS: 24.3 ± 1.8 vs. 21.8 ± 2.0, p < 0.05; HHS: 79.8 ± 5.2 vs. 75.3 ± 3.5, p < 0.05). Prosthetic-bone interface osteointegration, measured by T-SMART, favored 3D-printed prostheses, but surgery time (426.2 ± 67.0 vs. 301.7 ± 48.6 min, p < 0.05) and blood loss (2121.1 ± 686.8 vs. 1600.0 ± 505.0 ml, p < 0.05) were higher.ConclusionsThe 3D-printed hemipelvic endoprosthesis offers precise pelvic ring defect matching, superior stress transmission, and function compared to modular endoprostheses. However, complexity, fabrication expertise, and challenging surgical implantation result in prolonged operation times and increased blood loss. A nuanced consideration of functional outcomes, complexity, and patient conditions is crucial for informed treatment decisions.Level of evidenceLevel III, therapeutic study (Retrospective comparative study).

IrisVSA: Infinite-rotation infinite-stiffness Variable Stiffness Actuator towards physical human–robot-interaction

In Human–Robot-Collaboration applications, variable stiffness actuators provide an attractive actuation solution due to their well-established capabilities in ensuring accuracy and safety. Although, several existing VSAs have achieved an infinite-range of stiffness, those are generally relatively bulky, incapable of attaining an infinite-range of rotation, and their stiffness adjustment rate is rather slow. In this paper, we introduce a new infinite-rotation infinite-stiffness Variable Stiffness Actuator (irisVSA). The novelty of this actuator lies in its design topology, where two long-armed torsional springs are mounted on the output link and connected to the input link via a Force Contact Point (FCP). The variation in stiffness is realized by altering the relative distance from the FCP to the joint rotation center (effective arm). This unique topology offers a wide range of stiffness ranging from transparency (0 stiffness) to physically rigid. Moreover, the rate of stiffness adjustment is considerably fast (0.7 sec) through the utilization of a hypocycloid gear train. The working principle, design, prototyping, and characterization process for the irisVSA are detailed here. A Nonlinear Proportional–Integral–Derivative Controller is proposed to ensure the system’s accuracy. The safety of the actuator was evaluated by subjecting it to both impact force criterion experiments as well as Head Injury Criterion.

Hip arthroplasty in patients with rheumatoid arthritis

Introduction. The literature review deals with the current state of the problem of the hip replacement (HR), in patients with rheumatoid arthritis (RA) are considered in order to systematize the accumulated experience. Materials and methods. A search was conducted for relevant scientific publications over the past ten years in the databases of evidence-based medicine Cochrane Lirary, PubMed and the electronic scientific library e-library. According to the selected keywords, 100 publications were selected and analyzed. Results and discussion. RA is a systemic autoimmune disease characterized by synovial inflammation, symmetrical erosive-destructive polyarthritis, progressive destruction of the joints with the development of severe deformities, as well as a wide range of extra-articular somatic and hematological manifestations. It was revealed that HR allows you to restore musculoskeletal function and significantly reduce pain, but in patients with RA it has a large percentage of local and general complications. As a result of severe connective tissue lesions, long-term hormonal and immunosuppressive therapy, the structure of bone tissue and the anatomy of articulated bones change significantly. The protrusio acetabula with significant medialization of the center of rotation of the hip joint require a special reconstructive hip replacement. The minimizing surgical trauma, the osteoplasty protrusion defect of acetabula, stability fixation of the prosthesis, specialized preoperative preparation, reducing the activity of the inflammatory process, the prevention of periprosthetic infection and the prevention of venous thromboembolism, the correction of anemia are becoming increasingly relevant. Conclusion. It has been established that the normalization of the joint rotation center, the restoration of the offset with bone grafting of the protrusion defect, reliable primary fixation of the cementless acetabular component of the prosthesis, provide biomechanical conditions for long-term and painless functioning of the implant. Perioperative management of such patients should include a multidisciplinary approach.

Bionic design and analysis of a multi-posture wheelchair

Abstract. Posture transformation is an essential function for multi-posture wheelchairs. To improve the natural motion in posture transformation that is a popular problem in the design of multi-posture wheelchairs because the current wheelchair's posture transformation mechanism cannot remain consistent between the rotation center of the wheelchair and the rotation center of the human body joints. This paper proposes a sitting–standing–lying three-posture bionic transformation mechanism for a smart wheelchair. A human–wheelchair coupling model is described and analyzed according to the biomechanical characteristics of the posture transformation of human beings and their functional requirements. The configuration of the transformation mechanism is chosen by comparing the trails of the wheelchair rotation centers and the corresponding human joint rotation centers. The kinematics of the optimized configuration are discussed in detail to obtain the most bionic motion performance using the multivariable nonlinear constraint optimization algorithm. Finally, the mechanism is designed, and its posture transformation performance is simulated and verified using Adams (Automatic Dynamic Analysis of Mechanical Systems) software.

Lateralization in Reverse Shoulder Arthroplasty.

Indications for Reverse Shoulder Arthroplasty (RSA) have been extended over the last 25 years, and RSA has become the most frequently implanted shoulder arthroplasty worldwide. The initial Grammont design with medialization of the joint center of rotation (JCOR), placement of the JCOR at the bone–implant interface, distalization and semi-constrained configuration has been associated with drawbacks such as reduced rotation and range of motion (ROM), notching, instability and loss of shoulder contour. This review summarizes new strategies to overcome these drawbacks and analyzes the use of glenoid-sided, humeral-sided or global bipolar lateralization, which are applied differently by surgeons and current implant manufacturers. Advantages and drawbacks are discussed. There is evidence that lateralization addresses the initial drawbacks of the Grammont design, improving stability, rates of notching, ROM and shoulder contour, but the ideal extent of lateralization of the glenoid and humerus remains unclear, as well as the maximal acceptable joint reaction force after reduction. Overstuffing and spine of scapula fractures are potential risks. CT-based 3D planning as well as artificial intelligence will help surgeons with planning and execution of appropriate lateralization in RSA. Long-term follow-up of lateralization with new implant designs and implantation strategies is needed.

Development of a hip joint mathematical model to assess implanted and non-implanted hips under various conditions

While total hip arthroplasty does generally improve patient quality of life, current systems can still yield atypical forces, premature component wear, and abnormal kinematics compared to native joints. Specifically, common complications include instability, separation, sliding, and edge loading within the hip joint. Unfortunately, evaluating potential solutions to these issues can be costly and time-consuming. Fortunately, mathematical modeling is an accurate and efficient tool that can be used to evaluate potential solutions. A forward dynamics mathematical model of the hip allows users to virtually insert a hip implant into a theoretical patient and observe the predicted postoperative mechanics. The objective of this study is therefore to develop, validate, and use a fully functional forward solution mathematical model that allows for a comparison between various hip implant designs and a determination of factors leading to in vivo hip separation, instability, and edge loading. The model presented herein has been validated kinetically against telemetric data and kinematically against fluoroscopic data. It was determined through this research that shifting of the joint rotation center during total hip arthroplasty has the potential to yield postoperative instability, and surgical errors can exacerbate these outcomes. However, the relationships between subject-specific joint shifting and hip instability are extremely complex, and therefore it becomes essential for surgeons to focus on implanting components as accurately as possible to minimize these risks.

Dispersion of knee helical axes during walking in young and elderly healthy subjects

Knee joint rotation center displacement can be estimated in vivo through the analysis of helical axis (HAs) dispersion. HAs can be analyzed during walking, providing information on joint stability. The study aim was to describe knee HAs dispersion during walking in dominant and non-dominant legs of young and elderly healthy subjects.Twenty young (YG: age 23.3 ± 2.4 years) and twenty elderly (EG: age 69.3 ± 4.6 years) healthy subjects were asked to walk on a treadmill at a self-selected speed with reflective markers placed bilaterally on thighs and shanks to detect HAs dispersion and knee kinematics with an optoelectronic system. HAs dispersion was described during the following four phases of gait cycle: (1) flexion from 95% of the previous gait cycle to 10% of the subsequent gait cycle, (2) extension from 10% to 40%, (3) flexion from 40% to 75% and (4) extension from 75% to 95% of the gait cycle. Mean Distance (MD) and Mean Angle (MA) were used as HAs dispersion indexes during each gait phase.Participants showed greater MD and MA in sagittal and frontal planes during the first and second phases. EG revealed higher MD (p = 0.001) and MA (p < 0.001) during the first phase and higher MA (p = 0.001) during the fourth phase in both dominant and non-dominant legs on the sagittal plane.HAs dispersion could be related to the amount of forces acting on knee (first two phases) and knee degeneration (elderly). These results may be used as reference data in further studies on HAs dispersion in presence of knee pathologies or after knee surgery or rehabilitation.

Effects of nucleus pulposus location on spinal loads and joint centers of rotation and reaction during forward flexion: A combined finite element and Musculoskeletal study

The mechanical environment of the intervertebral disc and spinal loads are intimately associated with low back pain (LBP) caused by mechanical load. The cause and effect relationship between postures and pain has been therapeutically investigated and widely used to guide patient care. Shift of the nucleus pulposus (NP) inside the intervertebral disc when the spine changes posture in the sagittal plane, known also as NP migration, has been observed and quantified in in-vivo studies. However, the effects of this phenomenon on biomechanics of the disc and the surrounding spinal structures has not been investigated.This study aimed to quantify the effects of the NP location in a moderate flexion posture on spinal load and load-sharing using a Finite Element (FE) model of the L4-L5 functional spinal unit (FSU) driven by muscle forces, reaction forces, ligament forces and disc moment predicted by a Musculoskeletal (MSK) model of the trunk. The results showed that intradiscal pressure (IDP) and compressive force are sensitive to the nucleus location while the effects on the center of rotation (CoR), center of reaction (CTR) and moment rotation curves were negligible. Also, our findings revealed that FE models should consider the effects of NP location during bending to predict more realistic results as the nucleus displacement caused by disc bulge predicted by these models is much smaller than the real shift observed in in-vivo. In addition, this study confirmed that position of the rigid joint in MSK models that fix this latter to the CoR, must be modelled carefully for more accurate muscle forces and spinal loads prediction.

Centre of Rotation of the Human Subtalar Joint Using Weight-Bearing Clinical Computed Tomography

Accurate in vivo quantification of subtalar joint kinematics can provide important information for the clinical evaluation of subtalar joint function; the analysis of outcome of surgical procedures of the hindfoot; and the design of a replacement subtalar joint prosthesis. The objective of the current study was to explore the potential of full weight-bearing clinical computed tomography (CT) to evaluate the helical axis and centre of rotation of the subtalar joint during inversion and eversion motion. A subject specific methodology was proposed for the definition of the subtalar joint motion combining three-dimensional (3D) weight-bearing imaging at different joint positions with digital volume correlation (DVC). The computed subtalar joint helical axis parameters showed consistency across all healthy subjects and in line with previous data under simulated loads. A sphere fitting approach was introduced for the computation of subtalar joint centre of rotation, which allows to demonstrate that this centre of rotation is located in the middle facet of the subtalar joint. Some translation along the helical axis was also observed, reflecting the elasticity of the soft-tissue restraints. This study showed a novel technique for non-invasive quantitative analysis of bone-to-bone motion under full weight-bearing of the hindfoot. Identifying different joint kinematics in patients with ligamentous laxity and instability, or in the presence of stiffness and arthritis, could help clinicians to define optimal patient-specific treatments.

Monitoring System for Circular Deformation in Metro Shield Tunnels in Soft Soils

For in‐service metro shield tunnels in soft soils, large circular deformations are a major concern because they usually lead to various problems, such as water leakage, joint openings, and concrete cracks. However, the monitoring of circular deformation depends mainly on manual surveying, and the automatic monitoring methods developed in recent years generally have low economic applicability and are not widely implemented. In this study, an automatic and cost‐effective system was presented to monitor circular deformation in shield tunnels by using only inclinometers. Experiments were conducted to prove the assumption that each segment can be regarded as a rigid body and to investigate the position of the joint rotation center. Then, a method for monitoring circular deformation based on the rigid body and plane section assumptions was proposed. The joint opening angle, maximum joint opening width, horizontal diameter convergence, and bolt strain were calculated from rotation angles of segments which can be monitored directly by inclinometer. A case study was conducted for a section of a metro shield tunnel with an ongoing pit excavation nearby. The rotation of segments was measured using MEMS inclinometers, and the data were transmitted using ZigBee and general packet radio service (GPRS) wireless communication technology. Results show that the proposed system could be implemented to improve transportation safety in relevant situations and similar conditions.

Estimation of Instantaneous Hand Joint Centers of Rotation Using 3D Reconstructed Hand Skeleton Motion from CT Scans

The present study estimated instantaneous hand joint centers of rotation (CoR) using 3D reconstructed hand skeleton motions captured from CT scan. We proposed a novel method for estimation of instantaneous joint CoR using the same bone surfaces for different hand postures. Each bone in a template hand posture was registered to the corresponding bone of different hand postures. The registered hand postures (having the same bone surfaces as the template hand posture but different postures) with the template hand posture were then used for estimation of instantaneous joint CoR. The proposed method performed better than the existing methods in estimation of instantaneous joint CoR. Consistency of instantaneous joint CoRs determined in the same rotation angle range was improved by 31.7% to 51.0% in the proposed method. The present study focused on distal interphalangeal (DIP) and proximal interphalangeal (PIP) joints of the index finger of a participant. Joints of the whole hands of more participants will be studied for further generalization of the findings.

Inference on the Joint Center of Rotation by Covariance Pattern Models

Objective: In a statistical linear model estimating the center of rotation of a human hip joint, which is the parameter related to the mean of response vectors, assumptions of homoscedasticity and independence of position vectors measured repeatedly over time in the model result in an inefficient parameter. We, therefore, should take into account the variance-covariance structure of longitudinal responses. The purpose of this study was to estimate the efficient center of rotation vector of the hip joint by using covariance pattern models. Method: The covariance pattern models are used to model various kinds of covariance matrices of error vectors to take into account longitudinal data. The data acquired from functional motions to estimate hip joint center were applied to the models. Results: The results showed that the data were better fitted using various covariance pattern models than the general linear model assuming homoscedasticity and independence. Conclusion: The estimated joint centers of the covariance pattern models showed slight differences from those of the general linear model. The estimated standard errors of the joint center for covariance pattern models showed a large difference with those of the general linear model.

CUSTOM TRIFLANGE ACETABULAR COMPONENTS IN REVISION HIP REPLACEMENT (EXPERIENCE REVIEW)

Extensive defects of acetabulum especially accompanied by pelvis discontinuity at the level of acetabulum pose a serious challenge in revision hip replacement and create additional complexity in fixing the acetabular component. One of the perspective options to solve the above issue is the use of custom triflange acetabular components (CTAC) designed based on preoperative computer tomography given the specifics of bone defects of the patient. Purpose of the study — to evaluate the outcomes of CTAC use in revision hip replacement.Materials and methods. The authors analyzed treatment outcomes of 12 patients after revision hip replacement using additive techniques of computer simulation and 3D printing CTAC. Follow up period after the surgery averaged 7±3 months (from one to ten months). 7 out of 12 patients had acetabular defects of Paprosky 3B type, 4 patients had defects of Paprosky 3A and in one patient — of Paprosky 2C.Results. Two out of twelve patients had prosthesis dislocations that required revision hip surgery, one of those patients underwent open reduction of dislocation with wound debridement, another patient underwent replacement of articulating couple of acetabular component. Total scores under Harris Hip Score and paint VAS score prior to treatment was 28±7 and 7±1 points respectively, postoperative scores were 76±9 and 3±1 respectively.Conclusion. The application of additive techniques for revision hip replacement in patients with extensive acetabular and pelvic defects allows to make a precise preoperative planning, to restore joint rotation center, to reconstruct bone defects and to securely fix triflange acetabular component that altogether significantly improve treatment outcomes and patients satisfaction with the surgery.

Estimation of the wrist joint center of rotation

The human hand is involved in many daily human activities. The hand is connected to the forearm by the wrist joint which contributes to its special orientation facilitating the manipulation of obje...

Shank-to-Vertical Angle in Ankle-Foot Orthoses: A Comparison of Static and Dynamic Assessment in a Series of Cases

ABSTRACT Background Tuning of ankle-foot orthosis footwear combinations (AFO-FC) has been shown to be effective in aligning the ground reaction force (GRF) closer to the joint rotation center of the lower limbs. The notion of “tuning” the AFO-FC is largely dependent on the shank-to-vertical angle (SVA), which is measured while the subject is static but is meant to represent the SVA in mid-stance. Objectives The aim of this study was to compare the SVA measured in standing position with the SVA at temporal mid-stance (TMST) in a series of cases. Study Design This study is a case series. Methods Four participants had their AFO-FC tuned to optimum SVA using video-based gait analysis with GRF overlay. Initially, the SVA was measured with the subject standing in relaxed stance on the force plate with approximately equal weight on both feet. The SVA was then assessed at TMST. Results The measurement of the SVA of the AFO-FC in relaxed stance seems to be the same as the measurement of the SVA in TMST. Conclusions Measuring the SVA of the AFO-FC in relaxed stance is an accurate way of determining the SVA at TMST. Clinical Relevance Ankle-foot orthosis footwear combination tuning is considered an essential aspect of AFO prescriptions. The SVA is a key principle of AFO-FC tuning. The method for determining the SVA has yet to be tested to ensure that the static measurement correlates to the dynamic measurement during gait.

Joint replacement in patients with consequence of non-reduced hip joint fracture-dislocations

Joint replacement with the consequences of non-reduced hip fracture-dislocation is complex surgical intervention. Objec­tive: to develop a technique for hip arthroplasty and to evalu­ate its results in patients with consequences of hip fracture-dislocation. Methods: from 2004 to 2016 10 patients (10 joints) with the consequences of hip fracture-dislocation underwent total hip arthroplasty. The average age of the patients was 41.3 years (from 22 to 59), 5 men and 5 women. The shortening of the affected limb was on average 4.7 cm (2 to 8). In 5 patients, a reduction of the proximal femur with the external fixation de­vice in the «pelvic floor» system was performed before joint re­placement. The time of distraction and fixation in external fixa­tion device was on the average 55 days (from 21 to 98). The acetabular component of the endoprosthesis was set in the anatomi­cal position. Plastic defects in the acetabulum were carried out in 8 cases. Patients follow-up was from 6 month to 12 years. Results: the functional state of hip joint by the Harris score in­creased from 30 to 82 points. Patients with X-ray signs of in­stability of the endoprosthesis components were not identified. Complete restructuring of autograft was carried out in 100 % of cases. Complications related to external fixation device: 1 case — superficial soft tissue infection around the pin, 1 — fracture of the pin, 1 — early periprosthetic infection, 1 — re­current dislocation. Conclusions: the restoration of the hip joint rotation center and the length of the affected limb due to the use of the «pelvis – femur» external fixation device before joint repllacement, the reconstruction of the acetabular wall, taking into account the type of defect and the anatomical position of the endoprosthesis cup, allowed to minimize complications and obtain positive results in patients with consequences of hip fracture-dislocation.

In vivo identification of the shoulder joint centre of rotation using a magneto-inertial sensor

In vivo identification of the shoulder joint centre of rotation using a magneto-inertial sensor

An elastokinematic solution to the inverse kinematics of microhexapod manipulator with flexure joints of varying rotation center

In parallel manipulators with flexural joints, the position of the joint's rotation center continuously changes with the variation of the end effector's pose. The change occurring in the joints' rotation center is commonly ignored in the available solutions, which can lead to considerable error. In order to overcome this shortcoming, a new method has been developed by the present authors on the basis of elastokinematic analysis in which the elastic deformation of the flexure joints is taken into account for the kinematic analysis. The results have been verified by several cases of the moving platform's displacement and by finite element method.

The Shank-to-Vertical-Angle as a parameter to evaluate tuning of Ankle-Foot Orthoses

The effectiveness of an Ankle-Foot Orthosis footwear combination (AFO-FC) may be partly dependent on the alignment of the ground reaction force with respect to lower limb joint rotation centers, reflected by joint angles and moments. Adjusting (i.e. tuning) the AFO-FC's properties could affect this alignment, which may be guided by monitoring the Shank-to-Vertical-Angle. This study aimed to investigate whether the Shank-to-Vertical-Angle during walking responds to variations in heel height and footplate stiffness, and if this would reflect changes in joint angles and net moments in healthy adults. Ten subjects walked on an instrumented treadmill and performed six trials while walking with bilateral rigid Ankle-Foot Orthoses. The AFO-FC heel height was increased, aiming to impose a Shank-to-Vertical-Angle of 5°, 11° and 20°, and combined with a flexible or stiff footplate. For each trial, the Shank-to-Vertical-Angle, joint flexion–extension angles and net joint moments of the right leg at midstance were averaged over 25 gait cycles. The Shank-to-Vertical-Angle significantly increased with increasing heel height (p<0.001), resulting in an increase in knee flexion angle and internal knee extensor moment (p<0.001). The stiff footplate reduced the effect of heel height on the internal knee extensor moment (p=0.030), while the internal ankle plantar flexion moment increased (p=0.035). Effects of heel height and footplate stiffness on the hip joint were limited. Our results support the potential to use the Shank-to-Vertical-Angle as a parameter to evaluate AFO-FC tuning, as it is responsive to changes in heel height and reflects concomitant changes in the lower limb angles and moments.