Assessment of the functional method of hip joint center location subject to reduced range of hip motion

Motion analysis of the lower extremities usually requires determination of the location of the hip joint center. The results of several recent studies have suggested that kinematic and kinetic variables calculated from motion analysis data are highly sensitive to errors in hip joint center location. "Functional" methods in which the location of the hip joint center is determined from the relative motion of the thigh and pelvis, rather than from the locations of bony landmarks, are promising but may be ineffective when motion is limited. The aims of the present study were to determine whether the accuracy of the functional method is compromised in young and elderly subjects when limitations on hip motion are imposed and to investigate the possibility of locating the hip joint center using data collected during commonly studied motions (walking, sit-to-stand, stair ascent, stair descent) rather than using data from an ad hoc trial in which varied hip motions are performed. The results of the study suggested that functional methods would result in worst-case hip joint center location errors of 26mm (comparable to the average errors previously reported for joint center location based on bony landmarks) when available hip motion is substantially limited. Much larger errors ( approximately 70mm worst-case), however, resulted when hip joint centers were located from data collected during commonly performed motions, perhaps because these motions are, for the most part, restricted to the sagittal plane. It appears that the functional method can be successfully implemented when range of motion is limited but still requires collection of a special motion trial in which hip motion in both the sagittal and frontal planes is recorded.     

Validation of a functional method for the estimation of hip joint centre location

The present study assesses the accuracy with which the subject specific coordinates of the hip joint centre (HJC) in a pelvic anatomical frame can be estimated using different methods. The functional method was applied by calculating the centre of the best sphere described by the trajectory of markers placed on the thigh during several trials of hip rotations. Different prediction methods, proposed in the literature and in the present investigation, which estimate the HJC of adult subjects using regression equations and anthropometric measurements, were also assessed. The accuracy of each of the above-mentioned methods was investigated by comparing their predictions with measurements obtained on a sample of 11 male adult able-bodied volunteers using roentgen stereophotogrammetric analysis (RSA), assumed to provide the true HJC locations. Prediction methods estimated the HJC location at an average rms distance of 25-30 mm. The functional method performed significantly better and estimated HJCs within a rms distance of 13 mm on average. This result may be confidently generalised if the photogrammetric experiment is carefully conducted and an optimal analytical approach used. The method is therefore suggested for use in motion analysis when the subject's hip range of motion is not limited. In addition, the facts that it is not an invasive technique and that it has relatively small and un-biased errors, make it suitable for regression equations identification with no limit to sample size and population typology.     

Assessment of a greater trochanter-based method of locating the hip joint center

An alternative, yet unverified, predictive method that places the hip joint center (HJC) at one-quarter of the distance from the ipsolateral to the contralateral greater trochanter (GT method) is currently widely used in the biomechanics community. Therefore, the objective of this study was to confirm that this method is a viable option for estimating HJC coordinates. To accomplish this, HJC coordinates in the pelvic anatomical coordinate system were estimated via the GT method, a functional method, and the regression equations proposed by Bell et al. (1990). The HJC coordinated estimated by the functional method served as a baseline measurement. The results of this study demonstrate that all three methods evaluated offer repeatable estimates of HJC location. In comparison to the functional method, the GT method yielded a HJC estimate that was 7.6 mm medial, 12.2 mm posterior, and 4.8 mm proximal. On the other hand, the Bell regression equations estimated the HJC to be 2.6 mm medial, 7.2 mm posterior, and 21.7 mm proximal relative to the functional method. Additionally, the total 3D difference between the GT and functional methods was 23.5 mm compared to the 30.8 mm difference between the Bell and functional methods. These results suggest that the GT method is a viable option for estimating HJC coordinates.     

A framework for the functional identification of joint centers using markerless motion capture, validation for the hip joint

The objective of the study was to develop a framework for the accurate identification of joint centers to be used for the calculation of human body kinematics and kinetics. The present work introduces a method for the functional identification of joint centers using markerless motion capture (MMC). The MMC system used 8 color VGA cameras. An automatic segmentation-registration algorithm was developed to identify the optimal joint center in a least-square sense. The method was applied to the hip joint center with a validation study conducted in a virtual environment. The results had an accuracy (6mm mean absolute error) below the current MMC system resolution (1cm voxel resolution). Direct experimental comparison with marker-based methods was carried out showing mean absolute deviations over the three anatomical directions of 11.9 and 15.3mm if compared with either a full leg or only thigh markers protocol, respectively. Those experimental results were presented only in terms of deviations between the two systems (marker-based and markerless) as no real gold standard was available. The methods presented in this paper provide an important enabling step towards the biomechanical and clinical applications of markerless motion capture.     

An optimized protocol for hip joint centre determination using the functional method

The functional method identifies the hip joint centre (HJC) as the centre of rotation of the femur relative to the pelvis during an ad hoc movement normally recorded using stereophotogrammetry. This method may be used for the direct determination of subject-specific HJC coordinates or for creating a database from which regression equations may be derived that allow for the prediction of those coordinates. In order to contribute to the optimization of the functional method, the effects of the following factors were investigated: the algorithm used to estimate the HJC coordinates from marker coordinates, the type and amplitude of the movement of the femur relative to the pelvis, marker cluster location and dimensions, and the number of data samples. This was done using a simulation approach which, in turn, was validated using experiments made on a physical analogue of the pelvis and femur system. The algorithms used in the present context were classified and, in some instances, modified in order to optimize both accuracy and computation time, and submitted to a comparative evaluation. The type of movement that allowed for the most accurate results consisted of several flexion-extension/abduction-adduction movements performed on vertical planes of different orientations, followed by a circumduction movement. The accuracy of the HJC estimate improved, with an increasing rate, as a function of the amplitude of these movements. A sharp improvement was found as the number of the photogrammetric data samples used to describe the movement increased up to 500. For optimal performance with the recommended algorithms, markers were best located as far as possible from each other and with their centroid as close as possible to the HJC. By optimizing the analytical and experimental protocol, HJC location error not caused by soft tissue artefacts may be reduced by a factor of ten with a maximal expected value for such error of approximately 1mm.     

Subject-specific hip geometry and hip joint centre location affects calculated contact forces at the hip during gait

Hip loading affects the development of hip osteoarthritis, bone remodelling and osseointegration of implants. In this study, we analyzed the effect of subject-specific modelling of hip geometry and hip joint centre (HJC) location on the quantification of hip joint moments, muscle moments and hip contact forces during gait, using musculoskeletal modelling, inverse dynamic analysis and static optimization. For 10 subjects, hip joint moments, muscle moments and hip loading in terms of magnitude and orientation were quantified using three different model types, each including a different amount of subject-specific detail: (1) a generic scaled musculoskeletal model, (2) a generic scaled musculoskeletal model with subject-specific hip geometry (femoral anteversion, neck-length and neck-shaft angle) and (3) a generic scaled musculoskeletal model with subject-specific hip geometry including HJC location. Subject-specific geometry and HJC location were derived from CT. Significant differences were found between the three model types in HJC location, hip flexion–extension moment and inclination angle of the total contact force in the frontal plane. No model agreement was found between the three model types for the calculation of contact forces in terms of magnitude and orientations, and muscle moments. Therefore, we suggest that personalized models with individualized hip joint geometry and HJC location should be used for the quantification of hip loading. For biomechanical analyses aiming to understand modified hip joint loading, and planning hip surgery in patients with osteoarthritis, the amount of subject-specific detail, related to bone geometry and joint centre location in the musculoskeletal models used, needs to be considered.     

Accuracy and precision of a method to study kinematics of the temporomandibular joint: combination of motion data and CT imaging

The purpose of the study was to test the precision and accuracy of a method used to track selected landmarks during motion of the temporomandibular joint (TMJ). A precision phantom device was constructed and relative motions between two rigid bodies on the phantom device were measured using optoelectronic (OE) and electromagnetic (EM) motion tracking devices. The motion recordings were also combined with a 3D CT image for each type of motion tracking system (EM+CT and OE+CT) to mimic methods used in previous studies. In the OE and EM data collections, specific landmarks on the rigid bodies were determined using digitization. In the EM+CT and OE+CT data sets, the landmark locations were obtained from the CT images. 3D linear distances and 3D curvilinear path distances were calculated for the points. The accuracy and precision for all 4 methods were evaluated (EM, OE, EM+CT and OE+CT). In addition, results were compared with and without the CT imaging (EM vs. EM+CT, OE vs. OE+CT). All systems overestimated the actual 3D curvilinear path lengths. All systems also underestimated the actual rotation values. The accuracy of all methods was within 0.5mm for 3D curvilinear path calculations, 0.05mm for 3D linear distance calculations and 0.2 degrees for rotation calculations. In addition, Bland-Altman plots for each configuration of the systems suggest that measurements obtained from either system are repeatable and comparable.     

In vivo tests of an improved method for functional location of the subtalar joint axis

The subtalar joint is important in frontal plane movement and posture of the hindfoot. Abnormal subtalar joint moments caused by muscle forces and the ground reaction force acting on the foot are thought to play a role in various foot deformities. Calculating joint moments typically requires knowledge of the location of the joint axis; however, location of the subtalar axis from measured movement is difficult because the talus cannot be tracked using skin-mounted markers. The accuracy of a novel technique for locating the subtalar axis was assessed in vivo using magnetic resonance imaging. The method was also tested with skin-mounted markers and video motion analysis. The technique involves applying forces to the foot that cause pure subtalar joint motion (with negligible talocrural joint motion), and then using helical axis decomposition of the resulting tibiocalcaneal motion. The resulting subtalar axis estimates differed by 6° on average from the true best-fit subtalar axes in the MRI tests. Motion was found to have been applied primarily about the subtalar joint with an average of only 3° of talocrural joint motion. The proposed method provides a potential means for obtaining subject-specific subtalar axis estimates which can then be used in inverse dynamic analyses and subject-specific musculoskeletal models.     

Evaluation of a new algorithm to determine the hip joint center

Accurately locating the hip joint center is a challenging and important step in many biomechanical investigations. The purpose of this study was to test the accuracy and robustness of a "pivoting" algorithm used to locate the hip center. We tested the performance of this algorithm with data acquired by manipulating a ball and socket model of the hip through several motion patterns. The smallest mean errors of 2.2+/-0.2 mm occurred with a circumduction motion pattern, while the largest errors of 4.2+/-1.3 mm occurred with single-plane motion (e.g., flexion/extension). Introducing random noise with an amplitude of 30 mm increased the errors by only 1.3+/-0.5 mm with a circumduction motion pattern. The pivoting algorithm performs well in the laboratory, and further work is warranted to evaluate its performance in a clinical setting.     

Articular soft tissue anatomy of the archosaur hip joint: Structural homology and functional implications

Archosaurs evolved a wide diversity of locomotor postures, body sizes, and hip joint morphologies. The two extant archosaurs clades (birds and crocodylians) possess highly divergent hip joint morphologies, and the homologies and functions of their articular soft tissues, such as ligaments, cartilage, and tendons, are poorly understood. Reconstructing joint anatomy and function of extinct vertebrates is critical to understanding their posture, locomotor behavior, ecology, and evolution. However, the lack of soft tissues in fossil taxa makes accurate inferences of joint function difficult. Here, we describe the soft tissue anatomies and their osteological correlates in the hip joint of archosaurs and their sauropsid outgroups, and infer structural homology across the extant taxa. A comparative sample of 35 species of birds, crocodylians, lepidosaurs, and turtles ranging from hatchling to skeletally mature adult were studied using dissection, imaging, and histology. Birds and crocodylians possess topologically and histologically consistent articular soft tissues in their hip joints. Epiphyseal cartilages, fibrocartilages, and ligaments leave consistent osteological correlates. The archosaur acetabulum possesses distinct labrum and antitrochanter structures on the supraacetabulum. The ligamentum capitis femoris consists of distinct pubic‐ and ischial attachments, and is homologous with the ventral capsular ligament of lepidosaurs. The proximal femur has a hyaline cartilage core attached to the metaphysis via a fibrocartilaginous sleeve. This study provides new insight into soft tissue structures and their osteological correlates (e.g., the antitrochanter, the fovea capitis, and the metaphyseal collar) in the archosaur hip joint. The topological arrangement of fibro‐ and hyaline cartilage may provide mechanical support for the chondroepiphysis. The osteological correlates identified here will inform systematic and functional analyses of archosaur hindlimb evolution and provide the anatomical foundation for biomechanical investigations of joint tissues. J. Morphol. 276:601–630, 2015. © 2014 Wiley Periodicals, Inc.     

In vivo estimation of the glenohumeral joint centre by functional methods: Accuracy and repeatability assessment

Several algorithms have been proposed for determining the centre of rotation of ball joints. These algorithms are used rather to locate the hip joint centre. Few studies have focused on the determination of the glenohumeral joint centre. However, no studies have assessed the accuracy and repeatability of functional methods for glenohumeral joint centre.This paper aims at evaluating the accuracy and the repeatability with which the glenohumeral joint rotation centre (GHRC) can be estimated in vivo by functional methods. The reference joint centre is the glenohumeral anatomical centre obtained by medical imaging. Five functional methods were tested: the algorithm of Gamage and Lasenby (2002), bias compensated (Halvorsen, 2003), symmetrical centre of rotation estimation (Ehrig et al., 2006), normalization method (Chang and Pollard, 2007), helical axis (Woltring et al., 1985). The glenohumeral anatomical centre (GHAC) was deduced from the fitting of the humeral head.Four subjects performed three cycles of three different movements (flexion/extension, abduction/adduction and circumduction). For each test, the location of the glenohumeral joint centre was estimated by the five methods. Analyses focused on the 3D location, on the repeatability of location and on the accuracy by computing the Euclidian distance between the estimated GHRC and the GHAC. For all the methods, the error repeatability was inferior to 8.25 mm. This study showed that there are significant differences between the five functional methods. The smallest distance between the estimated joint centre and the centre of the humeral head was obtained with the method of Gamage and Lasenby (2002).     

Prediction of joint center location by customizable multiple regressions: Application to clavicle,scapula and humerus

Accurate spatial location of joint center (JC) is a key issue in motion analysis since JC locations are used to define standardized anatomical frames, in which results are represented. Accurate and reproducible JC location is important for data comparison and data exchange. This paper presents a method for JC locations based on the multiple regression algorithms without preliminary assumption on the behavior of the joint-of-interest. Regression equations were obtained from manually palpable ALs on each bone-of-interest. Results are presented for all joint surfaces found on the clavicle, scapula and humeral bone. Mean accuracy errors on the JC locations obtained on dry bones were 5.2±2.5 mm for the humeral head, 2.5±1.1 mm for the humeral trochlea, 2.3±0.9 mm for the humeral capitulum, 8.2±3.9 mm for the scapula glenoid cavity, 7.2±3.2 mm for the scapular aspect of the acromio-clavicular joint, 3.5±1.8 mm for the clavicular aspect of the sternoclavicular joint and 3.2±1.4 mm for the clavicular aspect of the acromio-clavicular joint. In-vitro and in-vivo validation accuracy was 5.3 and 8.5 mm, respectively, for the humeral head center location. Regression coefficients for joint radius dimension and joint surface orientation were also processed and reported in this paper.     

Accuracy and repeatability of joint angles measured using a single camera markerless motion capture system

Markerless motion capture systems have developed in an effort to evaluate human movement in a natural setting. However, the accuracy and reliability of these systems remain understudied. Therefore, the goals of this study were to quantify the accuracy and repeatability of joint angles using a single camera markerless motion capture system and to compare the markerless system performance with that of a marker-based system. A jig was placed in multiple static postures with marker trajectories collected using a ten camera motion analysis system. Depth and color image data were simultaneously collected from a single Microsoft Kinect camera, which was subsequently used to calculate virtual marker trajectories. A digital inclinometer provided a measure of ground-truth for sagittal and frontal plane joint angles. Joint angles were calculated with marker data from both motion capture systems using successive body-fixed rotations. The sagittal and frontal plane joint angles calculated from the marker-based and markerless system agreed with inclinometer measurements by <0.5°. The systems agreed with each other by <0.5° for sagittal and frontal plane joint angles and <2° for transverse plane rotation. Both systems showed a coefficient of reliability <0.5° for all angles. These results illustrate the feasibility of a single camera markerless motion capture system to accurately measure lower extremity kinematics and provide a first step in using this technology to discern clinically relevant differences in the joint kinematics of patient populations.     

A morphological and functional analysis of the extent of cartilage coverage in the human hip joint

The extension and the shape of the cartilage surface of 30 human femora and acetabula were measured. The results were considered and discussed as the response of the articular cartilage to the specific stress on this joint. 3 kinds of cartilage distribution were found on the femoral head; these shapes were understood as the consequence of the position and the dwelling time of the actual cartilage stimulating area. The largest extention of the cartilage was found in the ventrolateral direction and the smallest in medial direction. The cartilage margin of the "A" type was regulary curved. The "B" type has an inlet towards the fovea capitis. This inlet reaches in the "C" type to the fovea as an area free of cartilage. The acetabula could not be divided into types with different cartilage distribution because of the great similarity in shape. Therefore we computed an average acetabulum. The largest extension of the facies lunata was found 15 degrees in front of the roof of the acetabulas as seen in x-ray pictures. The cornu anterius is always narrower than the cornu posterius. The outer margin of the osseous acetabulum does not reach the equator, it lies on a latitude of 11.5 degrees. The incisura acetabuli is inclined against the vertical line with 18.3 degrees. The width of the facies lunata can be considered as a result of mechanical stress. The different extensions of the cartilage of both joint components in ventro-lateral direction seems to be the consequence of different extensions of movement. The area of movement of the caput femoris is larger than the area of the acetabulum.     

In vivo baseline measurements of hip joint range of motion in suspensory and nonsuspensory anthropoids

Hominoids and atelines are known to use suspensory behaviors and are assumed to possess greater hip joint mobility than nonsuspensory monkeys, particularly for range of abduction. This assumption has greatly influenced how extant and fossil primate hip joint morphology has been interpreted, despite the fact that there are no data available on hip mobility in hominoids or Ateles. This study uses in vivo measurements to test the hypothesis that suspensory anthropoids have significantly greater ranges of hip joint mobility than nonsuspensory anthropoids. Passive hip joint mobility was measured on a large sample of anesthetized captive anthropoids (nonhuman hominids = 43, hylobatids = 6, cercopithecids = 43, Ateles = 6, and Cebus = 6). Angular and linear data were collected using goniometers and tape measures. Range of motion (ROM) data were analyzed for significant differences by locomotor group using ANOVA and phylogenetic regression. The data demonstrate that suspensory anthropoids are capable of significantly greater hip abduction and external rotation. Degree of flexion and internal rotation were not larger in the suspensory primates, indicating that suspension is not associated with a global increase in hip mobility. Future work should consider the role of external rotation in abduction ability, how the physical position of the distal limb segments are influenced by differences in ROM proximally, as well as focus on bony and soft tissue differences that enable or restrict abduction and external rotation at the anthropoid hip joint. Am J Phys Anthropol 153:417–434, 2014. © 2013 Wiley Periodicals, Inc.     

Statistical shape modelling versus linear scaling: Effects on predictions of hip joint centre location and muscle moment arms in people with hip osteoarthritis

Marker-based dynamic functional or regression methods are used to compute joint centre locations that can be used to improve linear scaling of the pelvis in musculoskeletal models, although large errors have been reported using these methods. This study aimed to investigate if statistical shape models could improve prediction of the hip joint centre (HJC) location. The inclusion of complete pelvis imaging data from computed tomography (CT) was also explored to determine if free-form deformation techniques could further improve HJC estimates. Mean Euclidean distance errors were calculated between HJC from CT and estimates from shape modelling methods, and functional- and regression-based linear scaling approaches. The HJC of a generic musculoskeletal model was also perturbed to compute the root-mean squared error (RMSE) of the hip muscle moment arms between the reference HJC obtained from CT and the different scaling methods. Shape modelling without medical imaging data significantly reduced HJC location error estimates (11.4 ± 3.3 mm) compared to functional (36.9 ± 17.5 mm, p = <0.001) and regression (31.2 ± 15 mm, p = <0.001) methods. The addition of complete pelvis imaging data to the shape modelling workflow further reduced HJC error estimates compared to no imaging (6.6 ± 3.1 mm, p = 0.002). Average RMSE were greatest for the hip flexor and extensor muscle groups using the functional (16.71 mm and 8.87 mm respectively) and regression methods (16.15 mm and 9.97 mm respectively). The effects on moment-arms were less substantial for the shape modelling methods, ranging from 0.05 to 3.2 mm. Shape modelling methods improved HJC location and muscle moment-arm estimates compared to linear scaling of musculoskeletal models in patients with hip osteoarthritis.