1,721,007 research outputs found
In vivo kinematics of knee replacement during daily living activities: Condylar and post-cam contact assessment by three-dimensional fluoroscopy and finite element analyses
Full text linkIn total knee replacement, the investigation on the exact contact patterns at the post-cam in implanted patients from real in vivo data during daily living activities is fundamental for validating implant design concepts and assessing relevant performances. This study is aimed at verifying the restoration of natural tibio-femoral condylar kinematics by investigating the post-cam engagement at different motor tasks. An innovative validated technique, combining three-dimensional fluoroscopic and finite element analyses, was applied to measure joint kinematics during daily living activities in 15 patients implanted with guided motion posterior-stabilized total knee replacement. Motion results showed physiological antero-posterior translations of the tibio-femoral condyles for every motor task. However, high variability was observed in the position of the calculated pivot point among different patients and different motor tasks, as well as in the range of post-cam engagement. Physiological tibio-femoral joint rotations and contacts at the condyles were found restored in the present knee replacement. Articular contact patterns experienced at the post-cam were found compatible with this original prosthesis design. The present study reports replaced knee kinematics also in terms of articular surface contacts, both at the condyles and, for the first time, at the post-cam
The foot and ankle complex as a four degrees‐of‐freedom system: Kinematic coupling among the foot bones
No full textSeventy‐eight parameters are theoretically needed to describe the relative position and
orientation of all the 14 bones in the foot and ankle with respect to a reference bone
(foot posture). However, articular contacts and soft tissues introduce kinematic coupling,
reducing the number of the foot degrees‐of‐freedom (DOF). This study aims at providing
quantification and definition of these couplings. The foot posture was measured in vitro
through a series of computed tomography scans, spanning the whole range of foot dorsi/
plantar flexion and pronation/supination, also considering the effect of weightbearing.
The envelope of foot postures was investigated by means of principal component
analysis. The foot and ankle motion were well described with four principal sets of
kinematic couplings, that is, synergies. One synergy covers the independent motion of
the ankle, while three synergies describe the foot motion. The first foot synergy shows all
the bones rotating approximatively about a common axis, mapping the foot abduction/
adduction about the Chopart joint. The second foot synergy results in a spherical motion,
whose center is located between lateral cuneiform and navicular bone, mapping the foot
pronation/supination. The third foot synergy maps the opening of the foot arches during
the load acceptance. The foot and ankle complex can thus be described as a four DOF
system, whose motion is the result of the linear combination of four synergies. Significance:
Synergies reveal the contribution of each bone to the three‐dimensional foot
posture, providing a compact representation of the motion of the foot and ankle complex,
improving the comprehension of its physiology
Author Correction: 3D measurement techniques for the hindfoot alignment angle from weight-bearing CT in a clinical population
Full text linkCone-beam CT (CBCT) scans now enable accurate measurements on foot skeletal structures with
the advantage of observing these in 3D and in weight-bearing. Among the most common skeletal
deformities, the varus/valgus of the hindfoot is the most complex to be represented, and a number
of measure proposals have been published. This study aims to analyze and to compare these
measurements from CBCT scans in a real clinical population with large such deformity. Ten patients
with severe acquired adult fatfoot and indication for surgery underwent CBCT scans (Carestream,
USA) while standing on that leg, before and after surgical correction. Corresponding 3D shape of each
bone of the distal shank and hindfoot were defned (Materialise, Belgium). Six diferent techniques
from the literature were used to calculate the varus/valgus deformity, i.e. the inclination of the
hindfoot in the frontal plane of the shank. Standard clinical measurements by goniometers were taken
for comparison. According to these techniques, and starting from a careful 3D reconstruction of the
relevant foot skeletal structures, a large spectrum of measurements was found to represent the same
hindfoot alignment angle. Most of them were very diferent from the traditional clinical measures. The
assessment of the pre-operative valgus deformity and of the corresponding post-operative correction
varied considerably. CBCT fnally allows 3D assessment of foot deformities in weight-bearing.
Measurements from the diferent available techniques do not compare well, as they are based on
very diferent approaches. It is recommended to be aware of the anatomical and functional concepts
behind these techniques before clinical and surgical conclusions
Fluoroscopic and Gait Analyses for the Functional Performance of a Custom-Made Total Talonavicular Replacement
No full textThe present study evaluated the restoration of joint function in a special clinical case: a professional rock climber who underwent an original total talonavicular replacement with a custom-made prosthesis after a complex articular fracture. Full body gait analysis and 3-dimensional joint kinematics using single-plane fluoroscopy were performed on the same day at the 30-month follow-up examination. Gait analysis was performed using stereophotogrammetric, dynamometric, electromyographic, and baropodometric systems. Gait analysis showed good restoration of rotation, as well as moment patterns in the main lower limb and foot joints in the operated leg. At the artificial tibiotalar joint, videofluoroscopic analysis revealed a flexion capability of about 20°, together with a few degrees of motion in the frontal and transverse planes. The neighboring joints of the foot did not present with severe kinematic abnormalities. A full talonavicular replacement can be a viable and effective solution for complex ankle injury sequelae, even in patients with highly demanding functionality
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Custom-Made Total Talonavicular Replacement in a Professional Rock Climber
No full textProfessional athletes are often eager to resume sporting activities at preinjury levels. When facing the challenge of restoring joint function after a complex articular fracture, innovative solutions must be explored. We describe the results of what we believe to be the first custom-made talonavicular prosthesis implanted in a professional rock climber who had developed post-traumatic ankle and talonavicular arthritis as sequelae of a complex talar and navicular fracture. Using computed tomography scan reconstruction of the contralateral healthy ankle and direct metal laser sintering, a custom-made talonavicular prosthesis was obtained and implanted using an anteromedial approach. The patient was clinically and radiographically evaluated every 6 months after surgery for 30months. A 3-dimensional videofluoroscopic analysis was performed to assess the range of motion about the prosthesis. At the last follow-up visit, the functional scores were excellent (Tegner activity scale score of 9 of 10), and he had completely resumed his sporting activity. The American Orthopaedic Foot and Ankle Society score had increased from 36 to 81 points, and no signs of radiolucency were observed on the radiographs. The 3-dimensional videofluoroscopic analysis showed 15° of dorsiflexion and 4° of plantar flexion at the ankle. A customized solution is an option when the patient's expectations are not likely to be met by standard treatment, such as arthrodesis. A custom-made talonavicular prosthesis can be an effective solution for complex ankle injury sequelae in patients demanding high functionality
Better joint motion and muscle activity are achieved using kinematic alignment than neutral mechanical alignment in total knee replacement
No full textIntroduction: In total knee replacement (TKR), neutral mechanical
alignment (NMA) is generally targeted during prosthetic
component implantation. An original implantation approach has
been recently proposed, referred to as kinematic alignment (KA).
This is based on the alignment of the pre-arthritic lower limb undergoing
TKR, which is reconstructed using suitable image-based
techniques during the surgical planning phase. Particularly, KA is
thought to allow better soft-tissue balance [1] and restoration of
knee physiological function than NMA.
Patient-specific instrumentation (PSI), recently introduced in
TKR to execute more accurate and personalized prosthesis component
implantation, can be used in the achievement of KA. In detail,
KA approach via PSI has the potential to result in more physiological
knee motion, including relevant muscle activity, but this has not
been demonstrated yet. The aim of this study was to report knee
kinematics and electromyography (EMG) for a number lower limb
muscles from two TKR patient groups, i.e. operated according to
NMA via conventional instrumentation, or according to KA via PSI.
Methods: A four-centre randomized study of 144 patients
was designed; in each centre, 36 patients affected by primary
gonarthrosis were recruited for TKR and implanted with a
cruciate-retaining fixed-bearing prosthesis with patella resurfacing
(Triathlon® by Stryker®, Kalamazoo, MI-USA). In our centre 20
patients were implanted so far. 17 of these patients, i.e. 11 operated
targeting NMA (group A) via convention instrumentation and
6 targetingKA(group B) via PSI (ShapeMatch® by Stryker®, Kalamazoo,
MI-USA), were assessed clinically using the International Knee
Society Scoring (IKSS) System and biomechanically at 6-month
follow-up. Knee kinematics during stair-climbing, chair-rising and
extension-against-gravity was evaluated by 3D video-fluoroscopy
(CAT® Medical System, Monterotondo, Italy) synchronized with
4-channel EMG analysis (EMG Mate, Cometa®, Milan, Italy) of
the main knee ad/abductor and flexor/extensor muscles. Knee
motion data were reconstructed to calculate flex/extension (FE),
ad/abduction (AA), and internal/external rotation (IE), together
with the rotation of tibial base-plate contact-line (CLR), this being
the line connecting the medial (MCP) and lateral (LCP) condyle contact
points. MCP and LCP antero-posterior translations were also
calculated and reported in % of tibial base-plate length.
Results: Postoperative knee and functional IKSS scores in group
A were 78±20 and 80±23, worst than in group B, respectively
91±12 and 90±15. Knee motion patterns were much more consistent
over patients in group B than A. In both groups, normal
ranges were found for FE, IE and AA, the latter being generally
smaller than 3◦. Average IE ranges in the three motor tasks were
respectively 8.2±3.2◦, 10.1±3.9◦ and 7.9±4.0◦ in group A, and
6.6±4.0◦, 10.5±2.5◦ and 11.0±3.9◦ in group B. Corresponding
MCP translations were 13.8±5.6% anterior, 17.0±6.6% posterior
and 15.4±6.9% posterior in group A, and 13.0±3.4%, 16.6±5.3%
and 16.6±5.6% all posterior in group B; LCP values were all posterior,
i.e. 9.5±3.6%, 11.1±4.3% and 8.7±2.6% in group A, and
10.2±2.1%, 13.7±8.6% and 14.6±9.8% in group B. Relevant CLRs were 8.2±3.2◦, 10.2±3.7◦ and 8.8±5.3◦ in group A, and 7.3±3.5◦,
12.6±2.6◦ and 12.5±4.2◦ in group B. EMG analysis revealed prolonged
activation of the medial/lateral vasti muscles in group
A. Such muscle co-contraction was not generally observed in all
patients in group B, this being proving more stability in the knee
joint after TKA according KA.
Discussion: These results reveal that better function occurs
usingKAthanNMAin TKR. Though small differences were observed
between TKR groups in terms of motion data, the higher data
consistency and the less prolonged muscle activations identified
using KA support the claim of a more natural soft tissue balance
in corresponding knees. More patients are needed to establish the
superiority of KA.
Reference
[1] Eckhoff DG, et al. J Bone Joint Surg Am 2005;87(Suppl. 2):71–80
Variation of the ankle motion with the pivot-point position as predicted by a spherical model of the joint
No full textRecent studies proved that the ankle unloaded motion is nearly spherical and can be accurately
modeled by one degree-of-freedom spatial spherical mechanisms. Starting from relevant experimental
data measured on nine specimens, the global optimal pivot-point (PP) position,
i.e., the center of this spherical motion, is obtained in this study and the effect on ankle motion
of the changing position of this PP is analyzed
Location-Dependent Human Osteoarthritis Cartilage Response to Realistic Cyclic Loading: Ex-Vivo Analysis on Different Knee Compartments
Full text linkObjective: Osteoarthritis (OA) is a multifactorial musculoskeletal disorder affecting mostly weight-bearing joints. Chondrocyte response to load is modulated by inflammatory mediators and factors involved in extracellular cartilage matrix (ECM) maintenance, but regulatory mechanisms are not fully clarified yet. By using a recently proposed experimental model combining biomechanical data with cartilage molecular information, basally and following ex-vivo load application, we aimed at improving the understanding of human cartilage response to cyclic mechanical compressive stimuli by including cartilage original anatomical position and OA degree as independent factors. Methods: 19 mono-compartmental Knee OA patients undergoing total knee replacement were recruited. Cartilage explants from four different femoral condyles zones and with different degeneration levels were collected. The response of cartilage samples, pooled according to OA score and anatomical position was tested ex-vivo in a bioreactor. Mechanical stimulation was obtained via a 3-MPa 1-Hz sinusoidal compressive load for 45-min to replicate average knee loading during normal walking. Samples were analysed for chondrocyte gene expression and ECM factor release. Results: Non parametric univariate and multivariate (generalized linear mixed model) analysis was performed to evaluate the effect of compression and IL-1β stimulation in relationship to the anatomical position, local disease severity and clinical parameters with a level of significance set at 0.05. We observed an anti-inflammatory effect of compression inducing a significant downmodulation of IL-6 and IL-8 levels correlated to the anatomical regions, but not to OA score. Moreover, ADAMTS5, PIICP, COMP and CS were upregulated by compression, whereas COL-2CAV was downmodulated, all in relationship to the anatomical position and to the OA degree. Conclusion: While unconfined compression testing may not be fully representative of the in-vivo biomechanical situation, this study demonstrates the importance to consider the original cartilage anatomical position for a reliable biomolecular analysis of knee OA metabolism following mechanical stimulation
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