Passive Flexion-extension Movement Research Articles

Exploration of the Advanced VIVOTM Joint Simulator: An In-Depth Analysis of Opportunities and Limitations Demonstrated by the Artificial Knee Joint.

In biomechanical research, advanced joint simulators such as VIVOTM offer the ability to test artificial joints under realistic kinematics and load conditions. Furthermore, it promises to simplify testing with advanced control approaches and the ability to include virtual ligaments. However, the overall functionality concerning specific test setup conditions, such as the joint lubrication or control algorithm, has not been investigated in-depth so far. Therefore, the aim of this study was to analyse the basic functionality of the VIVOTM joint simulator with six degrees of freedom in order to highlight its capabilities and limitations when testing a total knee endoprostheses using a passive flexion-extension movement. For this, different test setup conditions were investigated, e.g., the control method, repeatability and kinematic reproducibility, waveform frequency, lubrication, and implant embedding. The features offered by the VIVOTM joint simulator are useful for testing joint endoprostheses under realistic loading scenarios. It was found that the results were highly influenced by the varying test setup conditions, although the same mechanical load case was analysed. This study highlights the difficulties encountered when using six degrees of freedom joint simulators, contributes to their understanding, and supports users of advanced joint simulators through functional and tribological analysis of joint endoprostheses.

A numerical investigation of the infrapatellar fat pad.

The infrapatellar fat pad is an adipose tissue in the knee that facilitates the distribution of synovial fluid and absorbs impulsive actions generated through the joint. The correlation between morphological configuration and mechanical properties is analyzed by a computational approach. The microscopic anatomy of the infrapatellar fat pad is studied aiming to measure the dimension of adipose lobules and the thickness of connective septa. Results from histomorphometric investigations show that the infrapatellar fat pad is an inhomogeneous tissue, constituted by large lobules in the superficial part and smaller lobules in the deepest one. Finite element models of the infrapatellar fat pad are developed. The first model considers the inhomogeneous conformation of the infrapatellar fat pad, composed of micro- and macro-chambers, while the second model considers a homogeneous distribution of adipose lobules with similar dimensions. Computational analyses are performed considering the static standing configuration and the passive flexion-extension movement. The computational results allow us to identify the different stress and strain fields within the tissue and to appreciate the variation of the mechanical performance of the overall system considering the distribution of adipose lobules. Results show that the distribution of adipose lobules in macro- and micro-chambers allows major deformation of the infrapatellar fat pad, decreasing the stress inside the tissues.

No differences in knee kinematics between active and passive flexion-extension movement: an intra-operative kinematic analysis performed during total knee arthroplasty

PurposeThe objective of the present study was to acquire and compare by the use of a navigation system the intra-operative flexion-extension movement of the knee performed actively by the patient and passively by the surgeon before and after a total knee arthroplasty (TKA) implantation.MethodsA cohort of 31 patients with primary knee osteoarthritis (OA), candidate for TKA underwent intra-operative kinematics assessment with a commercial navigation system before and after the definitive implant positioning of a Cruciate Retaining (CR) Mobile Bearing (MB) prostheses. The kinematical data were acquired while surgeon performed the flexion-extension movement (passive ROM - pROM), and while the patient performed it (active ROM - aROM). Differences between pre- and post- implantation and between active and passive motions, were statistically analyzed using paired Student t-tests (p = 0.05).ResultsNo statistically significant difference were found between aROM and pROM with paired Student t-test regarding internal-external rotation and anterior-posterior translation of the femoral component with respect to the tibia during flexion-extension movement before and after TKA implant (p > 0.05).ConclusionsActive muscle contraction seems to not significantly affect TKA kinematics. The ROM performed by the surgeon during operation resemble the movement actively performed by the patient.The clinical relevance of this study further supports the use of CAS system in performing intra-operative analysis concerning knee biomechanics.

Age-based model for metacarpophalangeal joint proprioception in elderly.

Neurological injuries such as stroke can lead to proprioceptive impairment. For an informed diagnosis, prognosis, and treatment planning, it is essential to be able to distinguish between healthy performance and deficits following the neurological injury. Since there is some evidence that proprioception declines with age and stroke occurs predominantly in the elderly population, it is important to create a healthy reference model in this specific age group. However, most studies investigate age effects by comparing young and elderly subjects and do not provide a model within a target age range. Moreover, despite the functional relevance of the hand in activities of daily living, age-based models of distal proprioception are scarce. Here, we present a proprioception model based on the assessment of the metacarpophalangeal joint angle difference threshold in 30 healthy elderly subjects, aged 55–80 years (median: 63, interquartile range: 58–66), using a robotic tool to apply passive flexion–extension movements to the index finger. A two-alternative forced-choice paradigm combined with an adaptive algorithm to define stimulus magnitude was used. The mixed-effects model analysis revealed that aging has a significant, increasing effect on the difference threshold at the metacarpophalangeal joint, whereas other predictors (eg, tested hand or sex) did not show a significant effect. The adaptive algorithm allowed reaching an average assessment duration <15 minutes, making its clinical applicability realistic. This study provides further evidence for an age-related decline in proprioception at the level of the hand. The established age-based model of proprioception in elderly may serve as a reference model for the proprioceptive performance of stroke patients, or of any other patient group with central or peripheral proprioceptive impairments. Furthermore, it demonstrates the potential of such automated robotic tools as a rapid and quantitative assessment to be used in research and clinical settings.

A new autocentering hinged external fixator of the elbow: a device that stabilizes the elbow axis without use of the articular pin

Hinged external fixation of the elbow is an important tool for the orthopedic surgeon. It enables early postoperative mobilization that may result in better outcomes. All models require correct alignment with the elbow axis of rotation. There is a long learning curve to this procedure, it may be time-consuming, and it can be associated with a high dose of x-ray exposure. An axial pin can interfere with bone-ligament suture anchors and bone reconstruction plates. A new external fixator has been designed and mechanically tested. The hinge has a special gear able to freely align itself with the center of elbow rotation during passive flexion-extension movements. It has been clinically tested on 7 patients affected by traumatic and post-traumatic elbow disorders. The maintenance of the correct position has been tested clinically with computed tomography scans and radiographs. All patients had correct alignment of the axis of rotation of the external fixator with the axis of elbow rotation. No cases of misalignment, loss of fixation, pin loosening, or instability were found. A new self-centering hinged external fixator correctly aligns itself with the axis of elbow rotation. It does not interfere with ligamentous reconstruction anchors, distal plates, or screw fixation. The surgical technique is easy to learn and relatively quick. It can also be positioned without performing an arthrotomy to maintain reduction of simple dislocations of the elbow.

Dynamic in vitro analysis of tractile forces of the anterior cruciate ligament (ACL) transplant using patellar and semitendinosus muscle tendon: a cadaver study.

The presented biomechanical study focused on the in vitro analysis of tractile forces working on the anterior cruciate ligament (ACL) and the ACL transplants, respectively, using a semitendinosus and/or patellar tendon during a passive flexion-extension movement (150-0°). Overall, 15 fresh frozen human knee joint pairs were examined. At first during arthroscopy, the tibial insertion of the ACL was drilled using a special hollow drill. Thereby, a bone cylinder was exposed at which a dynamometer was attached to enable for direct registration of tractile forces on the ACL via the connection between ACL-dynamometer and computer. The ACL transplant was fixed at the femur using a so-called endo-button, whereas the dynamometer was attached to the tibial end of the ACL transplant. The dynamic part of the examination was performed using the knee kinemator device developed by Plitz and Wirth et al. using different preload. The curves of the tractile forces of the ACL were qualitatively homogeneous with only low force values in the middle flexion position, whereas during maximum flexion and extension the forces increased reaching a maximum in the 0° position. Also, in testing the ACL transplants a force decrease between 0 and 50° flexion was recognized with even greater forces resulting at the 150° position depending on the anterior position of the femoral drill channel for implanting the ACL transplant. The amount of pre-loading showed no influence on the form of the tractile force curve. However, by enhancing the preload to 70 N, the maximal force in the ACL transplant increased significantly. The tractile forces assessed within the ACL during passive flexion movements between 10 and 90° were not greater than the forces measured in the ACL transplants. Thus, the clinical consequence is that in the early postoperative phase passive mobilization might be performed in this motion range without putting the ACL transplant at risk for damage.

Spinal and Pontine Relay Pathways Mediating Respiratory Rhythm Entrainment by Limb Proprioceptive Inputs in the Neonatal Rat

The coordination of locomotion and respiration is widespread among mammals, although the underlying neural mechanisms are still only partially understood. It was previously found in neonatal rat that cyclic electrical stimulation of spinal cervical and lumbar dorsal roots (DRs) can fully entrain (1:1 coupling) spontaneous respiratory activity expressed by the isolated brainstem/spinal cord. Here, we used a variety of preparations to determine the type of spinal sensory inputs responsible for this respiratory rhythm entrainment, and to establish the extent to which limb movement-activated feedback influences the medullary respiratory networks via direct or relayed ascending pathways. During in vivo overground locomotion, respiratory rhythm slowed and became coupled 1:1 with locomotion. In hindlimb-attached semi-isolated preparations, passive flexion-extension movements applied to a single hindlimb led to entrainment of fictive respiratory rhythmicity recorded in phrenic motoneurons, indicating that the recruitment of limb proprioceptive afferents could participate in the locomotor-respiratory coupling. Furthermore, in correspondence with the regionalization of spinal locomotor rhythm-generating circuitry, the stimulation of DRs at different segmental levels in isolated preparations revealed that cervical and lumbosacral proprioceptive inputs are more effective in this entraining influence than thoracic afferent pathways. Finally, blocking spinal synaptic transmission and using a combination of electrophysiology, calcium imaging and specific brainstem lesioning indicated that the ascending entraining signals from the cervical or lumbar limb afferents are transmitted across first-order synapses, probably monosynaptic, in the spinal cord. They are then conveyed to the brainstem respiratory centers via a brainstem pontine relay located in the parabrachial/Kölliker-Fuse nuclear complex.

A functional magnetic resonance imaging study of brain functional reorganization in patients with cerebral infarction

Objective To investigate activation patterns in the motor cortex of patients with cerebral infarction by blood oxygen level dependent-functional magnetic resonance imaging ( BOLD-fMRI) , and to explore the brain's functional reorganization mechanism. Methods Sixteen patients ( 12 men and 4 women, age 37 to 80, mean 61.0±11.3) who had suffered a subcortical infarction within the previous 3 months were studied. All the patients received fMRI scanning during passive flexion-extension movement of both the affected and unaffected wrist separately.Brain functional mapping was acquired with SPM2 software. Activation patterns in the brain were compared between the affected and unaffected hands. Results The volume and intensity of the activated areas were diverse, but showed some order. When the affected hand moved, the fMRI map showed general hyperactivation. When the unaffected hand moved, the contralateral M1 and S1 were activated. Conclusions After cerebral infarction, the brain cortex showed compensatory changes. As the main motor cortex (M1) was deactivated, the subsidiary motor areas such as the PMC, SMA, CMA, IPL, PFC and CRB were activated. The activated motor areas could shift to the area around the lesion, and the non-motor area was activated also. Key words: Cerebral infarction; Functional reorganization; Blood oxygen level dependent functional magnetic resonance imaging

Optimization of Graft Fixation at the Time of Anterior Cruciate Ligament Reconstruction

Background Although anterior cruciate ligament (ACL) reconstructions are frequently performed, little is known about the effect of initial tension on an ACL graft at the time of its fixation. Purpose The objective of this study was to evaluate the effects of initial tension on the relative position and the load between femur and tibia during passive motion. Study Design Controlled laboratory study. Methods Seven cadaveric knees underwent a passive flexion-extension movement from 0° to 90° with a robotic system developed in the authors’ laboratory under 6 degrees of freedom, while their 3-dimensional paths were recorded. A single-socket ACL reconstruction was performed with an autogenous quadrupled hamstring tendon graft, while the knees underwent the same movement as before with the initial graft tension of 22 N (group A), 44 N (group B), or 88 N (group C) at 20°. The relative position between the femur and the tibia was recorded, and the load in the femorotibial joint was calculated using the principle of superposition. Results The tibia in group C was most posteriorly positioned among the 3 groups (an average posterior translation of 0.6, 1.3, and 2.6 mm in groups A, B, and C, respectively). The tibia also moved proximally and laterally with external and valgus rotation with an increase in initial tension, and consequently the load in the femorotibial joint increased at ail flexion angles. Conclusion With an increase in initial tension, the tibia moved posterolaterally with external and valgus rotation, and consequently the contact force in the femorotibial joint increased. Clinical Relevance Excessive initial tension at the time of ACL reconstruction may potentially bring deleterious effects to the articular surface, leading to cartilage degeneration.

Phasic modulation of corticomotor excitability during passive movement of the upper limb: effects of movement frequency and muscle specificity

Modulations in the excitability of spinal reflex pathways during passive rhythmic movements of the lower limb have been demonstrated by a number of previous studies [4]. Less emphasis has been placed on the role of supraspinal pathways during passive movement, and on tasks involving the upper limb. In the present study, transcranial magnetic stimulation (TMS) was delivered to subjects while undergoing passive flexion–extension movements of the contralateral wrist. Motor evoked potentials (MEPs) of flexor carpi radialis (FCR) and abductor pollicus brevis (APB) muscles were recorded. Stimuli were delivered in eight phases of the movement cycle during three different frequencies of movement. Evidence of marked modulations in pathway excitability was found in the MEP amplitudes of the FCR muscle, with responses inhibited and facilitated from static values in the extension and flexion phases, respectively. The results indicated that at higher frequencies of movement there was greater modulation in pathway excitability. Paired-pulse TMS (sub-threshold conditioning) at short interstimulus intervals revealed modulations in the extent of inhibition in MEP amplitude at high movement frequencies. In the APB muscle, there was some evidence of phasic modulations of response amplitude, although the effects were less marked than those observed in FCR. It is speculated that these modulatory effects are mediated via Ia afferent pathways and arise as a consequence of the induced forearm muscle shortening and lengthening. Although the level at which this input influences the corticomotoneuronal pathway is difficult to discern, a contribution from cortical regions is suggested.