Hip Joint Centre Location Research Articles

Propagation of the hip joint centre location error to the estimate of femur vs pelvis orientation using a constrained or an unconstrained approach

To estimate hip joint angles during selected motor tasks using stereophotogrammetric data, it is necessary to determine the hip joint centre position. The question is whether the errors affecting that determination propagate less to the angles estimates when a three degrees of freedom (DOFs) constraint (spherical hinge) is used between femur and pelvis, rather than when the two bones are assumed to be unconstrained (six DOFs). An analytical relationship between the hip joint centre location error and the joint angle error was obtained limited to the planar case. In the 3-D case, a similar relationship was obtained using a simulation approach based on experimental data. The joint angle patterns resulted in a larger distortion using a constrained approach, especially when wider rotations occur. The range of motion of the hip flexion–extension, obtained simulating different location errors and without taking into account soft tissue artefacts, varied approximately 7 deg using a constrained approach and up to 1 deg when calculated with an unconstrained approach. Thus, the unconstrained approach should be preferred even though its estimated three linear DOFs most unlikely carry meaningful information.

Prediction of the hip joint centre in adults, children, and patients with cerebral palsy based on magnetic resonance imaging

The location of the hip joint centre (HJC) is required for calculations of hip moments, the location and orientation of the femur, and muscle lengths and lever arms. In clinical gait analysis, the HJC is normally estimated using regression equations based on normative data obtained from adult populations. There is limited relevant anthropometric data available for children, despite the fact that clinical gait analysis is predominantly used for the assessment of children with cerebral palsy. In this study, pelvic MRI scans were taken of eight adults (ages 23–40), 14 healthy children (ages 5–13) and 10 children with spastic diplegic cerebral palsy (ages 6–13). Relevant anatomical landmarks were located in the scans, and the HJC location in pelvic coordinates was found by fitting a sphere to points identified on the femoral head. The predictions of three common regression equations for HJC location were compared to those found directly from MRI. Maximum absolute errors of 31 mm were found in adults, 26 mm in children, and 31 mm in the cerebral palsy group. Results from regression analysis and leave-one-out cross-validation techniques on the MRI data suggested that the best predictors of HJC location were: pelvic depth for the antero-posterior direction; pelvic width and leg length for the supero-inferior direction; and pelvic depth and pelvic width for the medio-lateral direction. For single-variable regression, the exclusion of leg length and pelvic depth from the latter two regression equations is proposed. Regression equations could be generalised across adults, children and the cerebral palsy group.

Common Misconceptions of Normal Hip Joint Relations on Pelvic Radiographs

This study defines normal bilateral variations in offset and hip center location on pelvic radiographs. The relationship of the femoral head center to the tip of the greater trochanter and that of offset to medullary canal diameter are also defined. Measurements of the offset, hip center location, height of the tip of the greater trochanter from the femoral head center, and medullary canal diameter were carried out on 100 normal pelvic radiographs. The offset of one hip was found to predict that of the contralateral hip to within 4.62 mm with 95% confidence. Their hip center locations differed by 6.3 mm. The tip of the greater trochanter was, on average, 8 mm higher than the femoral head center. Although offset generally increased with an increase in medullary canal diameter, frequent discrepancies occurred in their relationship.

3D in vivo arthrokinematics of the ulnohumeral joint with active pronation-supination

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 1 mm.

Pelvic Width Predicts Hip Joint Center Location In Children

A precise estimate of the locations of the hip joint centers (HJC) is necessary when estimating in-vivo joint reaction forces and moments. Errors in timing and magnitude of hip joint moments have been reported to be up to 25% due to a HJC mislocation error of 30mm (Stagni,2000). While methods exist to predict HJC's based on pelvic width in adults, their applicability to children has not been reported. PURPOSE To determine how accurately MRI measures of pelvic width predict HJC locations in children. METHODS MRI's of the pelvic region were acquired from 10 healthy normal girls (9.6±0.9yrs; 141.0±9.4cm; 37.0±7.1kg; mean ± SD). The T1-weighted images were sampled from the coronal plane at 4mm intervals. Two slices were identified and exported into an imaging program for measurement: 1) the slice through the centers of the femoral heads and 2) the most anterior slice in which the left ASIS was visible. The reference frame was defined as: × = positive anterior, Y = positive left, and Z = positive superior. Fiduciary marks on the MRI's were used to calculate a scaling factor from pixels to SI units (1px = 0.5mm). Pelvic width was defined as the distance between the left and right ASIS. Because the MRI's only contained the two HJC's and the left ASIS, bilateral symmetry about the midpoint between HJC's was assumed in calculating the pelvic width. The displacement from the left ASIS to the left HJC was expressed in each direction as a percentage of the calculated pelvic width. The mean percentages in each direction were then used to predict the left HJC location of each subject. T-tests were used to determine if there were differences between the measured and predicted HJC locations in each direction (p<0.05). RESULTS The location of the left HJC relative to the left ASIS was −21.5±2.9%, −14.5±2.6%, and −32.8±4.9% of the pelvic width (18.1±1.4cm) in the X, Y, and Z directions, respectively. The magnitudes of the errors in predicted HJC location based on these percentages were 4.3±2.4mm (p<0.89), 3.5±2.7mm (p<0.89) & 6.8±5.1mm (p<0.91) in the X, Y, and Z directions, respectively for a total error of 9.8±4.3mm. CONCLUSION The location of the HJC relative to the ASIS as a percentage of pelvic width in these children was similar to that determined previously for adults. Our results also agree with Bell (1990) and Seidel (1995) in that the pelvic width best predicted the HJC along the axis it is parallel to. While the HJC prediction error was greater in the × and Z directions, the overall magnitude of the errors was quite small. Prediction of HJC location based on pelvic width is thus appropriate in computing the joint kinetics of children. International Society of Biomechanics Dissertation Grant.

Pelvic Width Predicts Hip Joint Center Location In Children

A precise estimate of the locations of the hip joint centers (HJC) is necessary when estimating in-vivo joint reaction forces and moments. Errors in timing and magnitude of hip joint moments have been reported to be up to 25% due to a HJC mislocation error of 30mm (Stagni,2000). While methods exist to predict HJC's based on pelvic width in adults, their applicability to children has not been reported. PURPOSE To determine how accurately MRI measures of pelvic width predict HJC locations in children. METHODS MRI's of the pelvic region were acquired from 10 healthy normal girls (9.6±0.9yrs; 141.0±9.4cm; 37.0±7.1kg; mean ± SD). The T1-weighted images were sampled from the coronal plane at 4mm intervals. Two slices were identified and exported into an imaging program for measurement: 1) the slice through the centers of the femoral heads and 2) the most anterior slice in which the left ASIS was visible. The reference frame was defined as: × = positive anterior, Y = positive left, and Z = positive superior. Fiduciary marks on the MRI's were used to calculate a scaling factor from pixels to SI units (1px = 0.5mm). Pelvic width was defined as the distance between the left and right ASIS. Because the MRI's only contained the two HJC's and the left ASIS, bilateral symmetry about the midpoint between HJC's was assumed in calculating the pelvic width. The displacement from the left ASIS to the left HJC was expressed in each direction as a percentage of the calculated pelvic width. The mean percentages in each direction were then used to predict the left HJC location of each subject. T-tests were used to determine if there were differences between the measured and predicted HJC locations in each direction (p<0.05). RESULTS The location of the left HJC relative to the left ASIS was −21.5±2.9%, −14.5±2.6%, and −32.8±4.9% of the pelvic width (18.1±1.4cm) in the X, Y, and Z directions, respectively. The magnitudes of the errors in predicted HJC location based on these percentages were 4.3±2.4mm (p<0.89), 3.5±2.7mm (p<0.89) & 6.8±5.1mm (p<0.91) in the X, Y, and Z directions, respectively for a total error of 9.8±4.3mm. CONCLUSION The location of the HJC relative to the ASIS as a percentage of pelvic width in these children was similar to that determined previously for adults. Our results also agree with Bell (1990) and Seidel (1995) in that the pelvic width best predicted the HJC along the axis it is parallel to. While the HJC prediction error was greater in the × and Z directions, the overall magnitude of the errors was quite small. Prediction of HJC location based on pelvic width is thus appropriate in computing the joint kinetics of children. International Society of Biomechanics Dissertation Grant.

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 1 mm.

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 26 mm (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 (∼70 mm 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.

Hip joint modeling for the control of the joint center and the range of motions

This paper presents a medical visualization tool implementing a hip joint modeling method that offers the control of the hip joint center and the assessment of the hip range of motions. As the shape of the femoral head is not a perfect sphere, it is in fact close to a 3D conchoid shape, the resulting articulation center cannot be modeled as the center of the sphere that best approximates the femoral head. In order to correctly assess the range of motion of a patient's hip, the medical doctor cannot proceed with such an approximation method. An automatic computation methodology of the hip joint center location is being designed and implemented based on the shape of the acetabular rim. And more, the extreme ranges of motions are calculated on the bony hip model.

An approach for hip joint center calculation for use in seated postures

In seated postures, such as those in office or automotive seats, locating the hip joint center (HJC) using three markers on the pelvis has been difficult if not impossible. A two-target approach by Bell et al. (J. Biomech. 23 (1990) 617) has been used, however, this method was shown to have inaccuracies when compared to the three-target method developed by Seidel et al. (J. Biomech. 28 (1995) 995). A new two-target method that is specific to the seated environment, has better accuracy than the Bell et al. approach, and is based on the Seidel et al. approach was developed and tested on 13 seated subjects. This new method used three targets and an initial reference file to estimate the HJC location. Once the HJC was located, assumptions were made that the magnitudes between the HJC and the respective anterior superior iliac spine, and the HJC and the respective lateral epicondyle remained constant. The primary concern when evaluating this new method was the affect of seated posture movement, in particular leg splay and spinal flexion on the assumptions. The results obtained with the new approach were compared to Seidel et al. and provided HJC locations with average differences of 3.8, 1.2 and 2.8 mm for spinal flexion in the anterior/posterior, medial/lateral and superior/inferior directions, respectively, and 2.3, 1.0 and 1.4 mm for knee splay. The proposed method provided better HJC estimation than the Bell et al. approach particularly in the superior/inferior dimensions.

Accuracy of the functional method of hip joint center location: effects of limited motion and varied implementation

Accurate location of the hip joint center is essential for computation of hip kinematics and kinetics as well as for determination of the moment arms of muscles crossing the hip. The functional method of hip joint center location involves fitting a pelvis-fixed sphere to the path traced by a thigh-fixed point while a subject performs hip motions; the center of this sphere is the hip joint center. The aim of the present study was to evaluate the potential accuracy of the functional method and the dependence of its accuracy on variations in its implementation and the amount of available hip motion. The motions of a mechanical linkage were studied to isolate the factors of interest, removing errors due to skin movement and the palpation of bony landmarks that are always present in human studies. It was found that reducing the range of hip motion from 30° to 15° did significantly increase hip joint center location errors, but that restricting motion to a single plane did not. The magnitudes of these errors, however, even in the least accurate cases, were smaller than those previously reported for either the functional method or other methods based on pelvis measurements of living subjects and cadaver specimens. Neither increasing the number of motion data observations nor analyzing the motion of a single thigh marker (rather than the centroid of multiple markers) was found to significantly increase error. The results of this study (1) imply that the limited range of motion that is often evident in subjects with hip pathology does not preclude accurate determination of the hip joint center when the functional method is used; and (2) provide guidelines for the use of the functional method in human subjects.

Effects of hip joint centre mislocation on gait analysis results

Methods to determine the hip joint centre (HJC) location are necessary in gait analysis. It has been demonstrated that the methods proposed in the literature involve large mislocation errors. The choice should be made according to the extent by which HJC location errors distort the estimates of angles and resultant moments at the hip and knee joints. This study aimed at quantifying how mislocation errors propagate to these gait analysis results. Angles and moments at the hip and knee joint were calculated for five able-bodied subjects during level walking. The nominal position of the HJC was determined as the position of the pivot point of a 3D movement of the thigh relative to the pelvis. Angles and moments were then re-calculated after having added to HJC co-ordinates errors in the range of ±30 mm. Angles and moments at both hip and knee joints were affected by HJC mislocation. The hip moments showed the largest propagation error: a 30 mm HJC anterior mislocation resulted in a propagated error into flexion/extension component of about −22%. The hip abduction/adduction moment was found the second largest affected quantity: a 30 mm lateral HJC mislocation produced a propagated error of about −15%. Finally, a 30 mm posterior HJC mislocation produced a delay of the flexion-to-extension timing in the order of 25% of the stride duration. HJC estimation methods with minimum antero-posterior error should therefore be preferred.

Radiographic and non-invasive determination of the hip joint center location: effect on hip joint moments

Objective. To determine which of four non-invasive measures is most accurate in locating the hip joint center. Background. The location of the joint centers must be accurately determined in three dimensions for calculation of the moments of force during gait. It is not known which of the several non-invasive methods available for location of the hip center is most accurate. Design. Hip center location was determined using standardized X-rays and four non-invasive methods which utilized measured distances between bony landmarks in 10 healthy subjects. Hip moments during gait were obtained from optical tracking, force plate and anthropometric data. Results. The most accurate non-invasive method of locating the hip center was by taking the midpoint of a line connecting the antero-superior iliac spine and the symphysis pubis and moving inferiorly 2 cm. Using this approach the hip center was located 0.7 cm medial and 0.8 cm superior to its true location determined using the standardized X-rays. The 95% confidence interval of the maximum error difference in moments measured between this method and the standardized X-rays ranged from −0.15 to 0.4 Nm/kg in the frontal plane, −0.03 to 0.07 Nm/kg in the sagittal plane and −0.05 to −0.03 Nm/kg in the transverse plane. Conclusions. Locating the hip center based on the distance between the antero-superior iliac spine and the symphysis pubis is a valid technique for estimating the hip center in routine gait analysis. Relevance Utilization of a non-invasive method of hip center location eliminates the need for X-rays, lowering costs and time in gait analysis studies as well as unnecessary exposure of subjects to radiation.

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.

Hip joint center location from palpable bony landmarks—A cadaver study

An anatomical anthropometric study of adult human cadaveric pelves was performed to investigate the relationship between hip joint center (HJC) and selected aspects of pelvic geometry. Sixty-five pelves (35 female and 30 male) were examined. Measurements of pelvic geometry and HJC (center of bony acetabular rim) were taken from bony landmarks of de-fleshed pelves. Correlation analysis revealed that HJC cannot be accurately located as a function of pelvic width alone, but requires estimation as a function of pelvic height and depth as well. HJC was optimally located relative to the respective ASIS: 14% of pelvic width medial (mean error 0.58 cm), 34% of pelvic depth posterior (mean error 0.30 cm), and 79% of pelvic height inferior (mean error 0.35 cm). No significant differences were found between males and females in HJC estimation.

Effects of hip center location on the moment-generating capacity of the muscles

We have developed a three-dimensional biomechanical model of the human lower extremity to study how the location of the hip center affects the moment-generating capacity of four muscle groups: the hip abductors, adductors, flexors, and extensors. The model computes the maximum isometric force and the resulting joint moments that each of 25 muscle-tendon complexes develops at any body position. Abduction, adduction, flexion, and extension moments calculated with the model correspond closely with isometric joint moments measured during maximum voluntary contractions. We used the model to determine (1) the hip center locations that maximize and minimize the moment-generating capacity of each muscle group and (2) the effects of superior-inferior, anterior-posterior, and medial-lateral displacement of the hip center on the moment arms, maximum isometric muscle forces, and maximum isometric moments generated by each muscle group. We found that superior-inferior displacement of the hip center has the greatest effect on the force- and moment-generating capacity of the muscles. A 2 cm superior displacement decreases abduction force (44%), moment arm (12%), and moment (49%), while a 2 cm inferior displacement increases abduction force (20%), moment arm (7%) and moment (26%). Similarly, a 2 cm superior displacement decreases flexion force (27%), moment arm (6%), and moment (22%), while inferior displacement increases all three variables. Anterior-posterior displacement alters the moment-generating capacity of the flexors and extensors considerably, primarily due to moment arm changes. Medial-lateral displacement has a large effect on the moment-generating capacity of the adductors only. A 2 cm medial displacement decreases adduction moment arm (20%), force (26%) and moment (40%). These results demonstrate that the force- and moment-generating capacities of the muscles are sensitive to the location of the hip center.

Effect of the hip center location on muscle strength

Effect of the hip center location on muscle strength

A comparison of the accuracy of several hip center location prediction methods

The purpose of this study was to estimate the accuracy with which this rotational method could estimate hip center location in a series of live subjects, and compare that to the accurary that could be obtained by the methods of Andriacchi's group and Tylkowski's group in the same subjects

Prediction of hip joint centre location from external landmarks

The approaches to predicting the hip joint centre (HJC) location of Tylkowski's group and Andriacchi's group were evaluated for accuracy and validity in children and adults of both sexes. Using Tylkowski's approach, we found that the three-dimensional (3-D) HJC location in adults (expressed as a percentage of the distance between the anterior superior iliac spines (ASIS)) was 30% distal, 14% medial, and 22% posterior to the ASIS, and predicted the HJC location to within 3.3 cm of the true location with 95% certainty. Using Andriacchi's approach, we found that the HJC was located in the frontal plane distal and lateral to the midpoint of a line between the ASIS and pubic symphysis, and varied from 2.2 cm distal and 0.78 cm lateral in girls to 4.6 cm distal and 1.7 cm lateral in men. A more accurate method of estimating the 3-D HJC location combined a modification of Andriacchi's approach (estimating frontal plane location of HJC) with a modification of Tylkowski's approach (estimating HJC location posterior to a frontal plane), and could predict the HJC location in adults to within 2.6 cm of the true location with 95% certainty.

Total Hip Acetabular Component Position Affects Component Loosening Rates

Loosening is the most common long-term problem following total hip arthroplasty. Many factors, including patient selection, cement technique, femoral component placement, and prosthesis design reportedly affect the incidence of loosening. Theoretically, the location of the hip center of rotation substantially affects the load on the hip, and superior and lateral hip center location will result in higher loads than medial and inferior placement. Long-term follow-up studies (average, 9.1 years after surgery) using logistical regression analysis demonstrate significantly higher rates of femoral loosening with acetabular components placed in a superior and lateral (i.e., nonanatomic) position, compared with acetabular components placed in a nearly anatomic position.