Biomedical subjects

T P Andriacchi

Publications and source records attributed to T P Andriacchi.

At least 19 recordsLinked to original sources

PubMed2006

A markerless motion capture system to study musculoskeletal biomechanics: visual hull and simulated annealing approach.

Human motion capture is frequently used to study musculoskeletal biomechanics and clinical problems, as well as to provide realistic animation for the entertainment industry. The most popular technique for human motion capture uses markers placed on the skin, despite some important drawbacks including the impediment to the motion by the presence of skin markers and relative movement between the skin where the markers are placed and the underlying bone. The latter makes it difficult to estimate the motion of the underlying bone, which is the variable of interest for biomechanical and clinical applications. A model-based markerless motion capture system is presented in this study, which does not require the placement of any markers on the subject's body. The described method is based on visual hull reconstruction and an a priori model of the subject. A custom version of adapted fast simulated annealing has been developed to match the model to the visual hull. The tracking capability and a quantitative validation of the method were evaluated in a virtual environment for a complete gait cycle. The obtained mean errors, for an entire gait cycle, for knee and hip flexion are respectively 1.5 degrees (+/-3.9 degrees ) and 2.0 degrees (+/-3.0 degrees ), while for knee and hip adduction they are respectively 2.0 degrees (+/-2.3 degrees ) and 1.1 degrees (+/-1.7 degrees ). Results for the ankle and shoulder joints are also presented. Experimental results captured in a gait laboratory with a real subject are also shown to demonstrate the effectiveness and potential of the presented method in a clinical environment.

Biomechanical Phenomena↗

PubMed2005

MR imaging of articular cartilage at 1.5T and 3.0T: comparison of SPGR and SSFP sequences.

OBJECTIVE: To compare articular cartilage signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and thickness measurements on a 1.5 T and a 3.0 T magnetic resonance (MR) scanner using three-dimensional spoiled gradient recalled echo (3D-SPGR) and two 3D steady-state free precession (SSFP) sequences. METHODS: Both knees of five volunteers were scanned at 1.5 T and at 3.0 T using a transmit-receive quadrature extremity coil. Each examination consisted of a sagittal 3D-SPGR sequence, a sagittal fat suppressed 3D-SSFP (FS-SSFP) sequence, and a sagittal Dixon 3D-SSFP sequence. For quantitative analysis, we compared cartilage SNR and CNR efficiencies, as well as average cartilage thickness measurements. RESULTS: For 3D-SPGR, cartilage SNR efficiencies at 3.0 T increased compared to those at 1.5 T by a factor of 1.83 (range: 1.40-2.09). In comparison to 3D-SPGR, the SNR efficiency of FS-SSFP increased by a factor of 2.13 (range: 1.81-2.39) and for Dixon SSFP by a factor of 2.39 (range: 1.95-2.99). For 3D-SPGR, CNR efficiencies between cartilage and its surrounding tissue increased compared to those at 1.5 T by a factor of 2.12 (range: 1.75-2.47), for FS-SSFP by a factor 2.11 (range: 1.58-2.80) and for Dixon SSFP by a factor 2.39 (range 2.09-2.83). Average cartilage thicknesses of load bearing regions were not different at both field strengths or between sequences (P>0.05). Mean average cartilage thickness measured in all knees was 2.28 mm. CONCLUSION: Articular cartilage imaging of the knee on a 3.0 T MR scanner shows increased SNR and CNR efficiencies compared to a 1.5 T scanner, where SSFP-based techniques show the highest increase in SNR and CNR efficiency. There was no difference between average cartilage thickness measurements performed at the 1.5 T and 3.0 T scanners or between the three different sequences.

Adult↗

PubMed2005

Considerations in measuring cartilage thickness using MRI: factors influencing reproducibility and accuracy.

OBJECTIVE: The primary goal of this study was to describe and evaluate conditions that could influence the precision and accuracy of measuring in vivo cartilage thickness in the weight bearing regions of the knee from magnetic resonance imaging (MRI). DESIGN: Three-dimensional (3D) models of the femoral cartilage were created from segmented MR images. The weight bearing regions on femoral cartilage were selected for the portion of the tibiofemoral joint that sustains contact during walking. Six regions of interest (three on each condyle) were located on the femur. Average cartilage thickness was calculated over each region. The sensitivity of the precision of the measurements to observer variability was evaluated using intra- and inter-observer reproducibility tests of cartilage thickness measurements from the MRI-derived 3D models. In addition, the quantitative influence of a rule-based protocol for segmentation was evaluated using the inter-observer reproducibility protocol. Accuracy tests were conducted on porcine knees by comparing 3D models from MR images and laser scans across weight bearing and non-weight bearing regions. RESULTS: The precision was substantially better for the intra-observer tests (Coefficient of variation (CV) = 1-3%) than the inter-observer tests. Adding a rule-based protocol reduced variability in inter-observer tests substantially (CV = 6.6% vs 8.3%). Accuracy tests showed that the central and weight bearing regions on each condyle were more accurate than boundary and non-weight bearing regions. In addition, these results indicate that care should be taken when determining cartilage thickness of weight bearing regions with cartilage degenerations, since the thickness of thinner cartilage can be systematically overestimated in MR images. CONCLUSIONS: A rule-based approach can substantially increase inter-observer reproducibility when measuring cartilage thickness from multiple observers. This improvement in inter-observer reproducibility could be an important consideration for longitudinal studies of disease progression. In quantifying cartilage thickness, central and weight bearing regions on each condyle can provide more accurate measurement than boundary and non-weight bearing regions with average accuracy of +/-0.2-0.3 mm. An important finding of this study was that the weight bearing regions, which are usually of the greatest clinical interest, were measured most accurately by sagittal plane imaging.

Cartilage, Articular↗

PubMed2004

Sensitivity of finite helical axis parameters to temporally varying realistic motion utilizing an idealized knee model.

Various uses of the screw or helical axis have previously been reported in the literature in an attempt to quantify the complex displacements and coupled rotations of in vivo human knee kinematics. Multiple methods have been used by previous authors to calculate the axis parameters, and it has been theorized that the mathematical stability and accuracy of the finite helical axis (FHA) is highly dependent on experimental variability and rotation increment spacing between axis calculations. Previous research has not addressed the sensitivity of the FHA for true in vivo data collection, as required for gait laboratory analysis. This research presents a controlled series of experiments simulating continuous data collection as utilized in gait analysis to investigate the sensitivity of the three-dimensional finite screw axis parameters of rotation, displacement, orientation and location with regard to time step increment spacing, utilizing two different methods for spatial location. Six-degree-of-freedom motion parameters are measured for an idealized rigid body knee model that is constrained to a planar motion profile for the purposes of error analysis. The kinematic data are collected using a multicamera optoelectronic system combined with an error minimization algorithm known as the point cluster method. Rotation about the screw axis is seen to be repeatable, accurate and time step increment insensitive. Displacement along the axis is highly dependent on time step increment sizing, with smaller rotation angles between calculations producing more accuracy. Orientation of the axis in space is accurate with only a slight filtering effect noticed during motion reversal. Locating the screw axis by a projected point onto the screw axis from the mid-point of the finite displacement is found to be less sensitive to motion reversal than finding the intersection of the axis with a reference plane. A filtering effect of the spatial location parameters was noted for larger time step increments during periods of little or no rotation.

Algorithms↗

PubMed2002

The knee adduction moment during gait in subjects with knee osteoarthritis is more closely correlated with static alignment than radiographic disease severity, toe out angle and pain.

This study tested whether the peak external knee adduction moments during walking in subjects with knee osteoarthritis (OA) were correlated with the mechanical axis of the leg, radiographic measures of OA severity, toe out angle or clinical assessments of pain, stiffness or function. Gait analysis was performed on 62 subjects with knee OA and 49 asymptomatic control subjects (normal subjects). The subjects with OA walked with a greater than normal peak adduction moment during early stance (p = 0.027). In the OA group, the mechanical axis was the best single predictor of the peak adduction moment during both early and late stance (R = 0.74, p < 0.001). The radiographic measures of OA severity in the medial compartment were also predictive of both peak adduction moments (R = 0.43 to 0.48, p < 0.001) along with the sum of the WOMAC subscales (R = -0.33 to -0.31, p < 0.017). The toe out angle was predictive of the peak adduction moment only during late stance (R = -0.45, p < 0.001). Once mechanical axis was accounted for, other factors only increased the ability to predict the peak knee adduction moments by 10 18%. While the mechanical axis was indicative of the peak adduction moments, it only accounted for about 50% of its variation, emphasizing the need for a dynamic evaluation of the knee joint loading environment. Understanding which clinical measures of OA are most closely associated with the dynamic knee joint loads may ultimately result in a better understanding of the disease process and the development of therapeutic interventions.

Aged↗

PubMed2002

Increased knee joint loads during walking are present in subjects with knee osteoarthritis.

OBJECTIVE: This study tests the hypothesis that the peak external knee adduction moment during gait is increased in a group of ambulatory subjects with knee osteoarthritis (OA) of varying radiographic severity who are being managed with medical therapy. Tibiofemoral knee OA more commonly affects the medial compartment. The external knee adduction moment can be used to assess the load distribution between the medial and lateral compartments of the knee joint. Additionally, this study tests if changes in the knee angles, such as a reduced midstance knee flexion angle, or reduced sagittal plane moments previously identified by others as load reducing mechanisms are present in this OA group. DESIGN: Thirty-one subjects with radiographic evidence of knee OA and medial compartment cartilage damage were gait tested after a 2-week drug washout period. Thirty-one normal subjects (asymptomatic control subjects) with a comparable age, weight and height distribution were also tested. Significant differences in the sagittal plane knee motion and peak external moments between the normal and knee OA groups were identified using t tests. RESULTS: Subjects with knee OA walked with a greater than normal peak external knee adduction moment (P=0.003). The midstance knee flexion angle was not significantly different between the two groups (P=0.625) nor were the peak flexion and extension moments (P> 0.037). CONCLUSIONS: Load reducing mechanisms, such as a decreased midstance knee flexion angle, identified by others in subjects with endstage knee OA or reduced external flexion or extension moments were not present in this group of subjects with knee OA who were being managed by conservative treatment. The finding of a significantly greater than normal external knee adduction moment in the knee OA group lends support to the hypothesis that an increased knee adduction moment during gait is associated with knee OA.

Aged↗

PubMed2001

Correcting for deformation in skin-based marker systems.

A new technique is described that reduces error due to skin movement artifact in the opto-electronic measurement of in vivo skeletal motion. This work builds on a previously described point cluster technique marker set and estimation algorithm by extending the transformation equations to the general deformation case using a set of activity-dependent deformation models. Skin deformation during activities of daily living are modeled as consisting of a functional form defined over the observation interval (the deformation model) plus additive noise (modeling error). The method is described as an interval deformation technique. The method was tested using simulation trials with systematic and random components of deformation error introduced into marker position vectors. The technique was found to substantially outperform methods that require rigid-body assumptions. The method was tested in vivo on a patient fitted with an external fixation device (Ilizarov). Simultaneous measurements from markers placed on the Ilizarov device (fixed to bone) were compared to measurements derived from skin-based markers. The interval deformation technique reduced the errors in limb segment pose estimate by 33 and 25% compared to the classic rigid-body technique for position and orientation, respectively. This newly developed method has demonstrated that by accounting for the changing shape of the limb segment, a substantial improvement in the estimates of in vivo skeletal movement can be achieved.

Biomechanical Phenomena↗

PubMed2000

Abnormalities in muscle function during gait in relation to the level of lumbar disc herniation.

STUDY DESIGN: A comparison between gait in patients undergoing surgery for L4 and L5 lumbar disc herniations and that in an age- and weight-matched control group. OBJECTIVES: To study whether changes in the moments produced at the ankle and knee joints during walking reflect the neurologic level of a herniated nucleus pulposus. SUMMARY OF BACKGROUND DATA: Lumbar herniated discs often cause muscle weakness, reduced motor function, and change in walking capacity. The specific effects of a disc herniation on muscle function during gait is poorly documented. METHODS: Conventional physical examination and kinetic analysis of gait were performed on 16 patients who subsequently underwent surgery for herniated discs (eight with L4-L5 and eight with L5-S1 disc herniations) and 16 healthy control subjects. The three components of the external moment at the ankle and knee were computed. The peak magnitudes of specific components of the external moments were compared with those of the control group. RESULTS: Reduced external ankle plantar flexion moment, indicating a decreased function of the ankle dorsiflexors, was found in patients with herniated nucleus pulposus of both L4-L5 and L5-S1. Reduced external ankle dorsiflexion moment, indicating a decreased function of the ankle plantar flexors, was found only in patients with a lesion to the L5-S1 disc, but not in those with herniations at L4-L5. CONCLUSIONS: Preoperative gait analysis identified functional deficits of the muscles about the ankle and foot that relate to the level of the herniation. Kinetic measurements can assist in understanding the functional limitations associated with specific levels of a herniation.

Adult↗

PubMed2000

Knee pain and joint loading in subjects with osteoarthritis of the knee.

Although treatments for osteoarthritis of the knee are often directed at relieving pain, pain may cause patients to alter how they perform activities to decrease the loads on the joints. The knee-adduction moment is a major determinant of the load distribution between the medial and lateral plateaus. Therefore, the interrelationship between pain and the external knee-adduction moment during walking may be especially important for understanding mechanical factors related to the progression of medial tibiofemoral osteoarthritis. Fifty-three subjects with symptomatic radiographic evidence of osteoarthritis of the knee were studied. These subjects were a subset of those enrolled in a double-blind study in which gait analysis and radiographic and clinical evaluations were performed after a 2-week washout of anti-inflammatory and analgesic treatment. The subjects then took a nonsteroidal anti-inflammatory drug, acetaminophen, or placebo for 2 weeks, and the gait and clinical evaluations were repeated. The change in the peak external adduction moment between the two evaluations was inversely correlated with the change in pain (R = 0.48, p < 0.001) and was significantly different between those whose pain increased (n = 7), decreased (n = 18), or remained unchanged (n = 28) (p = 0.009). Those with increased pain had a significant decrease in the peak external adduction (p = 0.005) and flexion moments (p = 0.023). In contrast, the subjects with decreased pain tended to have an increase in the peak external adduction moment (p = 0.095) and had a significant increase in the peak external extension moment (p = 0.017). The subjects whose pain was unchanged had no significant change in the peak external adduction (p = 0.757), flexion (p = 0.234), or extension (p = 0.465) moments. Thus, decreases in pain among patients with medial tibiofemoral osteoarthritis were related to increased loading of the degenerative portion of the joints. Additional long-term prospective studies are needed to determine whether increased loading during walking actually results in accelerated progression of the disease.

Aged↗

PubMed2000

Studies of human locomotion: past, present and future.

The study of human locomotion and its applications are examined from a historical viewpoint. Several critical steps in the advancement of the discipline are considered in the context of addressing a particular need to answer fundamental questions regarding the process of human locomotion. In addition, changes in the methods of observation are discussed in terms of the advancement of the field. As an example, the application of a newly developed point cluster technique to reduce the artifact due to skin movement is described. The method was applied to a study of patients with anterior cruciate ligament (ACL) deficient knees. The results demonstrate that patients with ACL-deficient knees have significantly greater than normal anterior-posterior displacement of the femur relative to the tibia during walking. Many of the advancements in the tools for observation and interpretation have been driven by new demands on our fundamental knowledge. Future advancements in the study of human locomotion will likely be motivated by new treatment modalities that require an in depth understanding of the subtle complexities of human locomotion. Future directions are discussed in the context of new methods for reducing errors associated with skin movement combined with information obtained from other imaging methods, such as magnetic resonance imaging.

Animals↗

PubMed2000

Methodology for long-term wear testing of total knee replacements.

This article begins to address the validation requirements of wear testing on total knee replacements in a knee simulator. The knee simulator has four stations. The axial force is variable but reaches a maximum of 2.3 kN. Physiologic anteroposterior shear force and rotational torques are supplied to the knee. The forces and displacements are timed to coincide with those of a typical gait cycle. Kinematics of the simulator are dependent on the type of knee being tested. Tests of designs with well known clinical histories were done to 10 million cycles. The relative amounts and types of wear shown by the designs were similar to that found in their clinical histories. Wear tracks on more conforming designs were larger, and the penetration into the plastic appeared to be less. This did not necessarily mean that wear, as measured by loss of material, was reduced on conforming designs. Delamination of the plastic was achieved only after aging the tibial components. Wear particles isolated from the lubricating fluid were similar in size and shape to those isolated from in vivo specimens. However, the relative amounts of wear particle shapes were different depending on the design. At the start of the tests, all of the flexibly mounted tibial components showed more motion than after 5 million cycles, indicating that the surface of the plastic became more conforming. This study showed that knee wear similar to wear observed in vivo can be reproduced in the laboratory. The parameters and methods elucidated in this introductory study should form the basis for use in preclinical wear tests of total knee replacements.

Biomechanical Phenomena↗

PubMed2000

Characterization of gait parameters in patients with Charcot-Marie-Tooth disease.

The gait of five patients with Charcot-Marie-Tooth(CMT) disease was analyzed using light-emitting diodes and a force plate. The flexion-extension motions of the hips, knees, and ankles, as well as their moments (vector sums of forces acting at the joints) in the flexion-extension and abduction-adduction planes, were quantified. The gait of the CMT patients showed abnormalities consistent with both distal weakness (ankle dorsi- and plantar-flexors) and weakness of the hip abductor muscles. The latter weakness appeared to produce asymmetric hip moments and truncal instability in the mediolateral plane during ambulation. However, the extent to which the gait was abnormal appeared not to be exclusively related to the severity of the sensorimotor conduction deficits in the peripheral nerves. In the four patients for whom nerve conduction velocity studies were available, decrease in the lower-extremity distal conduction velocities and evoked motor amplitude potentials did not correlate with the severity and extent of the gait abnormalities.

Biomechanical Phenomena↗

PubMed2000

[Functional gait adaptations in patients with painful hip].

PURPOSE OF THE STUDY: This prospective study was conducted to analyze the mechanisms of gait compensation in patients with painful hip and to search for correlations with preoperative clinical and radiographic findings. MATERIAL AND METHODS: Optoelectronic and multicomponent force-plate datas were used to calculate joint motion, moments and intersegmental forces for 26 patients with unilateral hip pain and 20 normal age and sex-matched patients. Height was similar in the two groups but mean weight in the study group (83 kg) was greater than in the controls (68 kg). The preoperative Harris score was 53 in the study group and 16 patients had a permanent flexion contracture of the knee (mean 15 degrees, range 5-30 degrees). Radiographically, there were 22 cases of osteo-arthritis hip disease and 4 cases of necrosis. RESULTS: Gait analysis showed a significant 0.66 +/- 0.06 m (12 p. 100) reduction in step length. Patients who had severe hip pain walked with a decreased dynamic range of motion (18 +/- 5 degrees, p<0.0001) with a curve reversal as they extended the hip. They also reduced dynamic range of motion of the knee and ankle. Patients who presented a reversal in their dynamic hip range of motion had a greater passive flexion contracture and a greater loss in range of motion during gait than those with a smooth regular pattern (p<0.0001). Patients with hip pain walked with significantly decreased external extension, adduction, and internal and external rotation moments (p<0.0001). They also unloaded the ipsilateral knee and ankle. The decreased hip extension moment was significantly correlated with an increased level of pain (p<0.0001). There was no correlation with radiological findings. DISCUSSION: Reversal of dynamic hip range of motion was interpreted as a mechanism to increase effective hip extension during stance phase through increased anterior pelvic tilt and lumbar lordosis. CONCLUSION: Patients with painful hip walked with a manner that was asymmetric. These gait modifications were related to hip limitation in passive motion and pain. Patients with flexion contracture adopted a compensatory gait mechanism. This study confirms relation between hip pain and forces across the hip joint.

Adaptation, Physiological↗

PubMed1999

Effect of knee pain on joint loading in patients with osteoarthritis.

Treatment of patients with osteoarthritis is often directed at relieving pain and restoring function. Pain, however, may serve as a protective mechanism in that patients may decrease their levels of activity or alter the manner in which they perform activities in response to pain. Pain reduction may result in increased loads on the joints during dynamic activities, which may result in more rapid disease progression. Therefore, treatment methods that relieve pain but result in a loss of the protective mechanisms associated with pain may not be beneficial in the long term. This mechanism of decreased pain associated with an overuse of the degenerated joint has been referred to as an "analgesic arthropathy." This article discusses common treatments or interventions used for patients with knee osteoarthritis and their potential effects on pain levels and loads at the knee joint during walking. Understanding the relationship between treatment methods, pain, and the knee joint loads during walking is important because walking is the most frequently performed activity, and the cyclic loads at the knee joint during walking are high.

Animals↗

PubMed1999

Study on effect of graded facetectomy on change in lumbar motion segment torsional flexibility using three-dimensional continuum contact representation for facet joints.

Facet joints provide rigidity to the lumbar motion segment and thus protect the disk, particularly against torsional injury. A surgical procedure that fully or partially removes the facet joints (facetectomy) will decrease the mechanical stiffness of the motion segment, and potentially place the disk at risk of injury. Analytical models can be used to understand the effect of facet joints on motion segment stability. Using a facet joint model that represents the contact area as contact between two surfaces rather than as point contact, it was concluded that a substantial sudden change in rotational motion, due to applied torsion moment, was observed after 75 percent of any one of the facet joints was removed. Applied torsional moment loading produced coupled extension motion in the intact motion segment. This coupled motion also experienced a large change following complete unilateral facetectomy. Clinically, the present study showed that surgical intervention in the form of unilateral or bilateral total facetectomy might require fusion to reduce the primary torsion motion.

Finite Element Analysis↗

PubMed1998

Knee adduction moment, serum hyaluronan level, and disease severity in medial tibiofemoral osteoarthritis.

OBJECTIVE: The adduction moment at the knee during gait is the primary determinant of medial-to-lateral load distribution. If the adduction moment contributes to progression of osteoarthritis (OA), then patients with advanced medial tibiofemoral OA should have higher adduction moments. The present study was undertaken to investigate the hypothesis that the adduction moment normalized for weight and height is associated with medial tibiofemoral OA disease severity after controlling for age, sex, and pain level, and to examine the correlation of serum hyaluronan (HA) level with disease severity and with the adduction moment in a subset of patients. METHODS: Fifty-four patients with medial tibiofemoral OA underwent gait analysis and radiographic evaluation. Disease severity was assessed using the Kellgren-Lawrence (K-L) grade and medial joint space width. In a subset of 23 patients with available sera, HA was quantified by sandwich enzyme-linked immunosorbent assay. Pearson correlations, a random effects model, and multivariate regression models were used. RESULTS: The adduction moment correlated with the K-L grade in the left and right knees (r = 0.68 and r = 0.60, respectively), and with joint space width in the left and right knees (r = -0.45 and r = -0.47, respectively). The relationship persisted after controlling for age, sex, and severity of pain. The partial correlation between K-L grade and adduction moment was 0.71 in the left knees and 0.61 in the right knees. For every 1.0-unit increase in adduction moment, there was a 0.63-mm decrease in joint space width. In the subset of patients in whom serum HA levels were measured, HA levels correlated with medial joint space width (r = -0.55), but not with the adduction moment. CONCLUSION: There is a significant relationship between the adduction moment and OA disease severity. Serum HA levels correlate with joint space width but not with the adduction moment. Longitudinal studies will be necessary to determine the contribution of the adduction moment, and its contribution in conjunction with metabolic markers, to progression of medial tibiofemoral OA.

Aged↗

PubMed1998

Dynamic knee loads during gait predict proximal tibial bone distribution.

This study tested the validity of the prediction of dynamic knee loads based on gait measurements. The relationship between the predicted loads at the knee and the distribution of bone between the medial and lateral sides of the tibia was examined. The motion and external forces and moments at the knee were measured during gait and a statically determinate muscle model was used to predict the corresponding forces on the medial and lateral tibial plateaus. In particular, the relationship between the knee adduction moment during gait and the ratio or distribution of medial to lateral tibial bone mineral content was studied. Bone mineral content was measured with dual energy X-ray absorptiometry in four regions, two proximal regions 20 mm in height, one medial and one lateral and two distal regions 20 mm in height, one medial and one lateral. The best single predictor of the medial lateral ratio of proximal bone mineral content (bone distribution) was the adduction moment (R2=0.31, p=0.003). Adding weight (negative coefficient. p=0.0004) and the ratio of the average predicted peak force on the medial plateau to the predicted peak force on the lateral plateau (positive coefficient, p=0.0033) to the regression model significantly increased the ability to predict the proximal medial lateral bone distribution (R2=0.72, p=0.0001). Distally neither the subject characteristics nor the gait moments and predicted forces were significant predictors of the bone distribution. The lack of a correlation distally may be reflective of the forces being more evenly distributed further from the tibial plateau. While it has long been suggested that the adduction moment is the primary determinate of the distribution of load between the medial and lateral plateaus, this is the first evidence of its relationship to the underlying bone distribution.

Absorptiometry, Photon↗

PubMed1998

Hip motion and moments during gait relate directly to proximal femoral bone mineral density in patients with hip osteoarthritis.

The present study examined the loads at the hip joint during gait and the bone mineral density of the proximal femur in 25 patients with end-stage hip osteoarthritis. Dual energy X-ray absorptiometry was used to determine the bone mineral density of the greater trochanter, femoral neck and Ward's triangle of the osteoarthritic group. The bone mineral density was normalized for the patient's age, gender, weight and ethnic origin (Z score). Gait analysis was used to determine the external hip joint moments and motion during walking for the osteoarthritic group and a control group of 21 normal subjects. The gait parameters of the osteoarthritic group which were significantly diminished compared to the normal group (p < 0.001) accounted for as much as 42% (p < 0.001) of the variation in the normalized bone mineral density. Specifically, the dynamic sagittal plane hip motion during gait (maximum flexion minus maximum extension) and peak external rotation and adduction moments were significantly correlated with greater trochanter (R = 0.429-0.648, p = 0.032-0.0001) and Ward's triangle (R = 0.418-0.532, p = 0.038-0.006) normalized bone mineral density while the adduction moment was also significantly correlated with the femoral neck normalized bone mineral density (R = 0.5394, p = 0.005). The normalized bone mineral density of the femoral neck and Ward's triangle was elevated while that of the greater trochanter was decreased as compared to normal reference values. The significant correlation between the hip joint moments during gait and femoral bone mineral density indicate that hip joint loads need to be included when explaining local variation in bone mineral density in hip osteoarthritis.

Absorptiometry, Photon↗