Finite Helical Axis Parameters Research Articles

Methodological analysis of finite helical axis behavior in cervical kinematics

Although a far more stable approach compared to the six degrees of freedom analysis, the finite helical axis (FHA) struggles with interpretational difficulties among health professionals. The analysis of the 3D-motion axis has been used in clinical studies, but mostly limited to qualitative analysis. The aim of this study is to introduce a novel approach for the quantification of the FHA behavior and to investigate the effect of noise and angle intervals on the estimation of FHA parameters. A simulation of body movement has been performed introducing Gaussian noise on position and orientation of a virtual sensor showing linear relation between the simulated noise and the error in the corresponding parameter.FHA axis behavior was determined by calculating the intersection points of the FHA with a number of planes perpendicular to the FHA using the Convex Hull (CH) technique. The angle between the FHA and each of the IHA was also computed and its distribution was also analyzed.Input noise has an inversely proportional relationship with the angle steps of FHA estimation. The proposed FHA quantification approach can be useful to provide new approaches to researchers and to improve insight for the clinician in order to better understand joint kinematics.

Quantifying differences in passive knee laxity and finite helical axis measures between healthy and anterior cruciate ligament deficient individuals

Quantifying differences in passive knee laxity and finite helical axis measures between healthy and anterior cruciate ligament deficient individuals

Midtarsal joint locking: New perspectives on an old paradigm

We investigated the existence of a midtarsal joint locking mechanism using cadaveric simulations of normal gait. Previous descriptions of this phenomenon led us to hypothesize that non-coupled rotations of the calcaneocuboid and talonavicular (i.e., midtarsal) joints and cubonavicular and talocalcaneal joints occur at heel strike and during weight acceptance, after which joint rotations cease with all bone-to-bone orientations remaining constant during the latter portions of stance phase. Three-dimensional kinematics of the talus, calcaneus, cuboid, and navicular were recorded along with muscle and ground reaction forces. Finite helical axis parameters and joint angles of directly articulating bones were subsequently derived and examined. During weight acceptance, the midtarsal joints everted with obvious changes in the relative orientation of their helical axes. The relative non-parallel orientation of these axes then remained constant until late in stance when these joints inverted and dorsiflexed toward their original pre-stance orientation. The cubonavicular and talocalcaneal joints demonstrated complimentary behavior. Contrary to our hypothesis, the midtarsal joints remained compliant during foot flat and even more so during push-off, despite divergent joint axes. Joint rotations were present after weight acceptance, thereby challenging the concept that midtarsal joint locking produces a rigid lever during push-off. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:110-115, 2014.

The finite helical axis of the knee joint (a non-invasive in vivo study using fast-PC MRI)

An understanding of the in vivo knee joint kinematics is critical for the further improvement and validation of knee joint models and for the development of better surgical and rehabilitative protocols. Unfortunately, most studies exploring the finite helical axis (FHA) tend to produce excellent qualitative results, but quantitative results are often lacking. Thus, the purpose of this study was to non-invasively and in vivo quantify the tibiofemoral FHA in a relatively large normal population during volitional knee extension using fast-PC MRI, to report the data relative to consistent coordinate systems (making it available for modeling input, experimental comparison and for device design), to determine the variability of the FHA, to investigate the screw home mechanism and to test the hypothesis that knee joint kinematics are independent of gender. Intra- and inter-subject repeatability was excellent. The intra- (inter-) subject repeatability of the FHA orientation in the frontal and axial planes was 1.8% (3.3%) and 3.7% (6.0%) of the average value, respectively. At the beginning of extension, the FHA was directed laterally and slightly superiorly and at the end of extension, it was directed in the lateral–inferior direction, indicative of the screw-home mechanism. The FHA location was not fixed during extension. There was small, but significant differences in all FHA parameters between genders and normalizing positional data relative to epicondylar width helped to reduce this difference. The data obtained in the current study forms an excellent base for future knee joint modeling and clinical studies.

A NEW TECHNIQUE ESTIMATING LOCATION OF MEAN JOINT CENTERS OF ROTATION WITH ASSOCIATED DISPERSIONS AND ASSESSING TO FUNCTIONAL COORDINATE SYSTEM OF MOVING LIMB SEGMENTS

Joint centers are obtained from data treatment of a set of markers placed on the skin of moving limb segments. Finite helical axis (FHA) parameters are calculated between time step increments. Artifacts associated with nonrigid body movements of markers entail ill-determination of FHA parameters. Mean centers of rotation may be calculated over the whole movement, when human articulations are likened to spherical joints. They are obtained using numerical technique, defining point with minimal amplitude, during joint movement. A new technique is presented. Hip, knee, and ankle mean centers of rotation are calculated. Their locations depend on the application of two constraints. The joint center must be located next to the estimated geometric joint center. The geometric joint center may migrate inside a cube of possible location. This cube of error is located with respect to the marker coordinate systems of the two limb segments adjacent to the joint. Its position depends on the joint and the patient height, and is obtained from a stereoradiographic study with specimen. The mean position of joint center and corresponding dispersion are obtained through a minimization procedure. The location of mean joint center is compared with the position of FHA calculated between different sequential steps: time sequential step, and rotation sequential step where a minimal rotation amplitude is imposed between two joint positions. Sticks are drawn connecting adjacent mean centers. The animation of stick diagrams allows clinical users to estimate the displacements of long bones (femur and tibia) from the whole data set.

Basic behavior of the finite helical axis in a simple tooth movement simulation

A finite helical axis (FHA) analysis can provide precise three-dimensional information on orthodontic tooth movement compared to an analysis based on a rectangular coordinate system. The FHA has already been applied in an analysis of orthodontic tooth movement. Interestingly, the position of the FHA changes dramatically in different stages of treatment; however, no previous report has provided detailed information of its basic behavior for clinicians. The purpose of this study was to clarify the basic behavior of the FHA in simple tooth movement, which could promote a better understanding of the 3-D orientation of and rotation about the FHA during tooth movement. Parameters of the FHA were calculated from a simulation of canine retraction. As the tipping angle of the canine was increased from 5° to 30°, the orientation vector of the FHA approached the most affected axis of rotation (on a rectangular coordinate system) in a non-linear manner. The angle of rotation about the FHA also increased in a non-linear manner. This non-linear problem was solved analytically. The basic behavior of the orientation vector of the FHA and the non-linear characteristics of the FHA parameters clarified in this study should be important for the future analysis of actual tooth movement based on the FHA. However, we must be aware that the non-linearity of the FHA itself may affect the analysis of the mechanical properties of the periodontal tissue.

Intra-articular kinematics of the normal glenohumeral joint in the late preparatory phase of throwing: Kaltenborn's rule revisited

A new method to quantify intra-articular relationships between articular surfaces of the glenohumeral joint during discrete poses representing the late preparatory phase of throwing is presented. This method is based on 3D bone reconstructions from medical imaging data processed into finite helical axis parameters. With the shoulder moving in the anatomical planes from 90° abduction and 90° external rotation into the apprehension test pose, the centre of the humeral head posteriorly translated on the glenoid and rotated about a finite helical axis, which was positioned at the joint contact. The data are contrasted with Kaltenborn's convex-concave rule explaining intra-articular kinematics of the glenohumeral joint as a ball-and-socket joint. The data show at all conditions that the glenohumeral joint does not act as a ball-and-socket joint. Consequently, the mobilization techniques used in manual therapy, which are based on this convexconcave rule, should be adapted.

Effects of Data Smoothing on the Reconstruction of Helical Axis Parameters in Human Joint Kinematics

In biomechanical joint-motion analyses, the continuous motion to be studied is often approximated by a sequence of finite displacements, and the Finite Helical Axis (FHA) or "screw axis" for each displacement is estimated from position measurements on a number of anatomical or artificial landmarks. When FHA parameters are directly determined from raw (noisy) displacement data, both the position and the direction of the FHA are ill-determined, in particular when the sequential displacement steps are small. This implies, that under certain conditions, the continuous pathways of joint motions cannot be adequately described. The purpose of the present experimental study is to investigate the applicability of smoothing (or filtering) techniques, in those cases where FHA parameters are ill-determined. Two different quintic-spline smoothing methods were used to analyze the motion data obtained with Roentgenstereophotogrammetry in two experiments. One concerning carpal motions in a wrist-joint specimen, and one relative to a kinematic laboratory model, in which the axis positions are a priori known. The smoothed and non-smoothed FHA parameter errors were compared. The influences of the number of samples and the size of the sampling interval (displacement step) were investigated, as were the effects of equidistant and nonequidistant sampling conditions and noise invariance.