Human Distal Femur Research Articles

Dual-frequency ultrasound technique minimizes errors induced by soft tissue in ultrasound bone densitometry

Most bone ultrasound devices are designed for through-transmission measurements of the calcaneus. In principle, ultrasound backscattering measurements are possible at more typical fracture sites of the central skeleton. Unfortunately, soft tissue overlying the bones diminishes reliability of these measurements. To apply the single-transducer dual-frequency ultrasound (DFUS) technique to eliminate the errors induced by soft tissue on the measurements of integrated reflection coefficient (IRC) in human distal femur in vivo. Ultrasound and dual-energy X-ray absorptiometry (DXA) examinations were conducted on a bodybuilder during a 21-week training and dieting period. Significant changes in quantity and composition of soft tissue took place during the diet. However, DXA measurements showed no significant effects on bone density measurements. The single transducer DFUS technique enabled the determination of local soft-tissue composition, as verified by comparison with the DXA (r=0.91, n=8, p<0.01). Further, the technique eliminated the soft-tissue-induced error from IRC measured for the bone. The uncorrected IRC associated significantly with the change in local soft-tissue composition (r=-0.83, n=8, p<0.05), whereas the corrected IRC values showed no significant dependence (r=-0.30, n=8, p=0.46) on local soft-tissue composition. The DFUS technique may significantly enhance the accuracy of clinical ultrasound measurements of bone.

Dual frequency ultrasound technique enables determination of soft tissue composition and improves reliability of in vivo ultrasound bone densitometry

Soft tissues diminish reliability of the bone ultrasound backscatter measurements. In this study, the ability of a single broadband transducer dual frequency ultrasound (DFUS) technique to monitor the changes in soft tissue was investigated in a body builder during a 21 week training and dieting period, inducing a weight loss of 16.5 kg (18%). Then, DFUS was applied to correct the errors induced by soft tissues on the measurements of integrated reflection coefficient (IRC) in human distal femur. In DFUS, US reflection from soft tissue‐bone interface is determined with two different US frequencies and, by knowing the frequency specific US attenuation and speed in adipose and lean tissues, their content can be determined. The dual energy X‐ray absorptiometry (DXA) indicated that significant changes in quantity and composition of soft tissue, but not in bone density, took place during the diet. As compared with DXA, the single transducer DFUS could determine local soft tissue composition (r2 = 0.88, n=8, p <...

Compressive properties of trabecular bone in the distal femur

Early loosening and implant migration are two problems that lead to failures in cementless (press-fit) femoral knee components of total knee replacements. To begin to address these early failures, this study determined the anterior–posterior mechanical properties from four locations in the human distal femur. Thirty-three cylindrical specimens were removed perpendicular to the press-fit surface after the surgical cuts on 10 human cadaveric femurs (age 71.5±14.2 years) had been made. Compression testing was performed that utilized methods to reduce the effects of end-artifacts. The bone mineral apparent density (BMAD), apparent modulus of elasticity, yield and ultimate stress, and yield and ultimate strain were measured for 28 cylindrical specimens. The apparent modulus, yield and ultimate stress, and yield and ultimate strain each significantly differed ( p<0.05) in the superior and inferior locations. Linear and power law relationships between superior and inferior mechanical properties and BMAD were determined. The inferior apparent modulus and stresses were higher than those in the superior locations. These results show that the press-fit fixation characteristics of the femoral knee component differ on the anterior shield and posterior condyles. This information will be useful in the assignment of mechanical properties in finite element models for further investigations of femoral knee components. The property–density relations also have applications for implant design and preoperative assessment of bone strength using clinically available tools.

909 1方向X線画像を用いた骨のイメージレジストレーションの精度検証(J04-2 臨床医歯学における非・低侵襲計測技術の展開(2) MRIおよびX線応用計測,ジョイントセッション,21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

The purpose of present study is to examine the accuracy of 2D-3D image registration technique for measuring natural knee kinematics. A human cadaver distal femur was secured to a 6 degree-of-freedom (DOF) mechanical stage that is controllable within ±5 ° and ±5 mm. The stage with the femur was fixed to a camera calibration frame so that the 3D position of the femur can be determined in terms of the camera coordinate system. Single-plane x-ray photographs of the femur were taken using fluoroscopy and plane radiography. Each of 3 rotation parameters was changed from -2° to 2° by 1°, and for each of 3 translation parameters -2 mm to 2 mm by 1 mm. The 3D position of the femur was recovered by matching the digitally reconstructed radiographs generated from its 3D volume model derived from CT scan data. Average errors ± standard deviation and root mean square errors in two out-of-plane rotations were 0.4°±1.6° [1.1° and 0.1°±1.2° [1.2°], and one out-of-plane translation was 0.4 mm±4.3 mm [4.3 mm] by fluoroscopy, and those by plane radiography were 0.8°±0.4° [0.9°], -0.7°±1.4° [1.5°] and 0.6 mm±5.2 mm [5.1 mm].

Cartilage-selective genes identified in genome-scale analysis of non-cartilage and cartilage gene expression

BackgroundCartilage plays a fundamental role in the development of the human skeleton. Early in embryogenesis, mesenchymal cells condense and differentiate into chondrocytes to shape the early skeleton. Subsequently, the cartilage anlagen differentiate to form the growth plates, which are responsible for linear bone growth, and the articular chondrocytes, which facilitate joint function. However, despite the multiplicity of roles of cartilage during human fetal life, surprisingly little is known about its transcriptome. To address this, a whole genome microarray expression profile was generated using RNA isolated from 18–22 week human distal femur fetal cartilage and compared with a database of control normal human tissues aggregated at UCLA, termed Celsius.Results161 cartilage-selective genes were identified, defined as genes significantly expressed in cartilage with low expression and little variation across a panel of 34 non-cartilage tissues. Among these 161 genes were cartilage-specific genes such as cartilage collagen genes and 25 genes which have been associated with skeletal phenotypes in humans and/or mice. Many of the other cartilage-selective genes do not have established roles in cartilage or are novel, unannotated genes. Quantitative RT-PCR confirmed the unique pattern of gene expression observed by microarray analysis.ConclusionDefining the gene expression pattern for cartilage has identified new genes that may contribute to human skeletogenesis as well as provided further candidate genes for skeletal dysplasias. The data suggest that fetal cartilage is a complex and transcriptionally active tissue and demonstrate that the set of genes selectively expressed in the tissue has been greatly underestimated.

Upregulation of Apoptotic and Matrix-related Gene Expression during Fresh Osteochondral Allograft Storage

We identified changes in proapoptotic and extracellular matrix-related gene expression with prolonged storage of fresh osteochondral allografts using gene array analysis to better understand the process of graft degradation during storage. Six human distal femurs were obtained according to standard organ harvesting protocol and stored in serum-free allograft media. Each was examined at baseline (within 72 hours postmortem), 21 days (average time of implantation), and 35 days (maximum time to implantation) for proapoptotic and extracellular matrix-related gene expression using two 100-gene microarrays, cell viability using confocal microscopy, and proteoglycan synthesis via SO4 incorporation. We found numerous genes showing upregulation associated with increased storage time, including CD30, CD30 ligand, Fas, Fas ligand, tumor necrosis factor-alpha, and several caspases. Cell viability and proteoglycan synthesis also were significantly decreased with increased storage. Loss of chondrocytes via apoptosis is likely a key determinant of osteochondral allograft viability during storage, whereas extracellular matrix degeneration may occur at a later stage. These findings provide targets for future media modulation. Improved graft viability and the potential for lengthened storage periods through improved storage conditions may improve clinical outcomes and availability of fresh osteochondral allografts.

Resident’s ridge: assessing the cortical thickness of the lateral wall and roof of the intercondylar notch

Purpose: The purpose of this study was to better delineate the anatomy of “resident’s ridge,” a term coined by William Clancy Jr., M.D., to describe the raised bony landmark commonly visualized just anterior to the femoral attachment of the anterior cruciate ligament (ACL). This landmark can mislead the novice surgeon into misplacing the femoral tunnel of ACL reconstructions. Type of Study: Cadaveric anatomic study. Methods: Ten human distal femurs harvested from embalmed specimens were fixed, sectioned, and analyzed for the presence and descriptive characteristics of resident’s ridge. A single, blinded examiner evaluated slope, cortical thickness at 4 sites, and the presence or absence of a distinct ridge relative to the attachment of the ACL. Results: A defined resident’s ridge was present in 9 of 10 specimens. This was directly associated with a change in slope of the intracondylar roof in the same 9 of 10 patients. The mean cortical thickness at the ACL attachment site was 1.6 mm. This was thicker than at resident’s ridge (mean, 0.90 mm), the cartilage-intercondylar notch junction (mean, 0.96 mm), and a point midway between the ACL attachment and the cartilage-intercondylar notch junction (mean, 0.90 mm). Conclusions: The phenomenon of “resident’s ridge” is accounted for by a distinctive change in slope of the femoral notch roof that occurs just anterior to the femoral attachment of the ACL. The density change apparent at the time of notchplasty is probably caused by the transition between normal cortical thickness just anterior to the ACL and the cortical thickness of the ACL attachment. No distinctive increased cortical thickness can be identified as “resident’s ridge.”

Growth plate forces in the adolescent human knee: a radiographic and mechanical study of epiphyseal staples.

The purpose of this study was to quantify the forces produced by the growth plates of the adolescent human proximal tibia and distal femur. The postoperative deformations of staples used to treat genu valgum were correlated with similar staple deformations produced by mechanical testing. Staple deformation was measured in sequential radiographs of 35 knees in 20 patients. Mechanical tests were performed on new staples to determine the force necessary to bend the staples to the observed displacements. Based on deformation at final examination, the static equivalent loads exerted at the joint centerline by the growth plates of the proximal tibia and distal femur were 0.5 kN per physis. The estimated corresponding stress was 1 MPa. These results indicated that successful lower limb hemiepiphysiodesis suppressed a longitudinally directed, centrally applied compressive force on the order of body weight.

Effect of bone quality on the forces generated by compression screws

Internal fixation of the fractured scaphoid bone is used to promote union between bone fragments and to decrease wrist immobilization. Headless screws are commonly used because they minimize interference with articular surfaces and reduce tissue irritation and immobilization. In the present experiment, compressive force was measured as a function of bone quality for two headless screw types, the Herbert and the Acutrak. Forty-seven cylindrical samples of cancellous bone were prepared from fresh, previously frozen human cadaveric distal femora. The compressive forces generated as the screws were advanced into the specimens were measured and correlated to the specimens’ bone mineral density (BMD) and density. Over the range tested, the average compressive force for the Acutrack screw was approximately 42% higher than that of the Herbert. Statistical significance, however, could not established because of the low statistical power of the test due to the inherent spread in the data. For the Acutrak screw, force was best fit to BMD and to density by second-order polynomials. Regression analysis indicated that similar correlations did not exist between force and BMD or between force and density for the Herbert screw. The correlation shown by the Acutrak screw indicates that it may be a more predictable as well as more effective system and therefore there may be some advantage in selecting this system. Furthermore, results suggest that the Acutrak screw generates greater forces with increasing bone density and could be more effective for a younger population.

Morsellized bone grafting compensates for femoral bone loss in revision total knee arthroplasty. An experimental study

This study was undertaken to examine the contribution of uncontained morsellized bone graft to the structural properties of a femoral reconstruction in total knee arthroplasty and to serve as a basis for an in vivo animal study. Ten human distal femora with a standard unicondylar uncontained medial bone defect were prepared to fit a femoral component of a cruciate sacrificing TKA. A cyclic axial load of 750 N was applied to the medial part of the femoral component in the presence of impacted morsellized bone graft. After removal of the bone graft, the cyclic loading was repeated for the unsupported situation. None of the grafts collapsed and all cement mantles stayed intact during the experiments. Elastic deformation during cyclic loading was significantly less when graft was added while time-dependent deformation was not affected. We conclude that impacted morsellized bone graft, used for reconstruction of uncontained femoral bone loss in revision knee arthroplasty, may improve the structural resistence against loading. Further animal experimentation for in vivo application is warranted.

Mathematical representation of articular surfaces using influence surface theory

Many mathematical techniques have been developed to determine the geometry of articular joint surfaces, because of its so importance to the study of human joint biomechanics. However, a three-dimensional geometric model of the articular joint, which is essential to solid modelling, contact area measurement, and load bearing analyses, has not been well developed. This study proposes to define the articular geometry of the distal femoral joint of the human knee. A mathematical method based on the influence surface theory of plates is established to generate representations of three-dimensional articular surfaces. A mathematical cone and the surface of the human distal femur are accurately recreated, allowing their geometric properties to be determined. Results suggest that this method can be an effective tool for representing articular surfaces.

Sample size estimates for the use of human bone in the experimental study of cancellous screw extraction mechanics

Cancellous bone screw extraction strengths are determined in four matched anatomical locations in five pairs of unembalmed human distal femora. The results are used to calculate sample size estimates for the experimental detection of differences in screw extraction mechanics. While unmatched designs require prohibitively large numbers of bone specimens, matched designs require between 71.6 and 88.5% fewer, depending on the correlation between matched observations and the homogeneity of sample variances.

A B-Spline Least-Squares Surface-Fitting Method for Articular Surfaces of Diarthrodial Joints

The B-spline least-squares surface-fitting method is employed to create geometric models of diarthrodial joint articular surfaces. This method provides a smooth higher-order surface approximation from experimental three-dimensional surface data that have been obtained with any suitable measurement technique. Akima's method for surface interpolation is used to provide complete support to the B-spline surface. The surface-fitting method is successfully tested on a known analytical surface, and is applied to the human distal femur. Applications to other articular surfaces are also shown. Results show that this method is precise, highly flexible, and can be successfully applied to a large variety of articular surface shapes.

The limitations of canine trabecular bone as a model for human: A biomechanical study

Distal canine femurs were sectioned into 8mm cubic specimens. Orthogonal compression tests were performed to preyield in two or three directions and to failure in a third. Apparent density and ash weight density were measured for a subset of specimens. The results were compared to the human distal femur results of Ciarelli et al. (Transactions of the 32nd Annual Meeting of the Orthopaedic Research Society, Vol. 11, p. 42, 1986). Quantitative similarities existed in the fraction of components comprising the trabecular tissue of the two species. Qualitative similarities were seen in the positional and anisotropic variation of the mechanical properties, and also in the form and strength of the relationships between the mean modulus and bone density, ultimate stress and density, and ultimate stress and modulus. However, significantly different regression equations resulted for the mean modulus-density, and ultimate stress-modulus relationships, indicating that for the same density, canine trabecular bone displays a lower modulus than human, and may achieve greater compressive strains before failure.