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Biomedical subjects

R Huiskes

Publications and source records attributed to R Huiskes.

At least 163 records · Page 9Linked to original sources
PubMed1989

Plain radiographs inadequate for evaluation of the cement-bone interface in the hip prosthesis. A cadaver study of femoral stems.

To determine whether plain radiographs accurately represent the true cement-bone interlock, a comparison was made between radiographs and macroscopic morphology on cross sections of 11 human femora into which a cemented endoprosthesis had been inserted. Four femora had been retrieved postmortem from patients with a hip arthroplasty, and seven cadaver femora were cemented under varying conditions. All the femora were radiographed and then cut for macroscopic inspection of the cement-bone interface with respect to gross interposition, depth of cement penetration, integrity of the bone bed, and lamellation of the cement.

Bone Cements↗
PubMed1989

Adaptive bone remodeling and biomechanical design considerations for noncemented total hip arthroplasty.

Clinical problems with noncemented total hip arthroplasty (THA) stems, directly or indirectly related to load transfer, include mid-thigh pain due to relative (micro) motions or excessive endosteal interface stresses, subsidence and loosening due to inadequate primary stability and fit, and proximal femoral bone atrophy due to stress shielding. In this article, the load-transfer mechanisms associated with noncemented THA stems and their resulting stress patterns are discussed in relation to design features, bonding characteristics, and materials choice. Nonlinear finite-element models and computer simulation programs for strain-adaptive bone remodeling have been used for this study. Canal-filling, fully bonded metal stems have been found likely to cause proximal bone atrophy, possibly leading to long-term failure of the implant/bone composite. The use of flexible (isoelastic) materials and/or press-fit fixation reduces stress shielding, but also reduces the potential for interface stability. The stem material, the stem shape, and the coating geometry interact in relation to the load-transfer mechanism, and it is suggested that optimal combinations of these characteristics can be determined through the computer simulation methods presented.

Adaptation, Physiological↗
PubMed1989

Anteroposterior drawer measurements in the knee using an instrumented test device.

A newly developed instrumented knee laxity tester was used to measure anteroposterior (AP) drawer parameters (Lachmann test) in populations of normal subjects and patients with anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) insufficiencies. The AP drawer tester features a differential electronic measuring procedure of displacements between patella and tuberosity over a continuous range between 180 and -180 N of AP forces. In the statistical evaluation, shift and compliance (or stiffness) parameters at various forces are considered. In a representative normal population, all relevant parameters were established, thus creating a normal data base for future reference. The average normal AP drawer shift between maximal anterior and posterior forces (180 N) was 6.4 +/- 1.7 mm. Right-left differences and male-female differences were found not to be statistically significant in any of the parameters. The validity of the instrumented drawer tester was confirmed relative to a group of patients with acute documented ligament insufficiencies. Measurements in two groups of patients with chronic postoperative knee instabilities revealed that although the diagnosis of instability could be confirmed, the results could hardly discriminate between ACL and PCL insufficiencies, probably due to unrecognized associated lesions at the time of operation and/or gradual postoperative developments of insufficiencies and deformities. An unexpected finding was that the mean laxities of the uninjured contralateral knees were significantly extended relative to the normal reference group, suggesting that these patients could have been classified as a high-risk group even before the time of injury.

Biomechanical Phenomena↗
PubMed1988

The envelope of passive knee joint motion.

The purpose of this study is to create an accurate experimental database for the passive (in vitro) freedom-of-motion characteristics of the human knee joint on a subject to subject basis, suitable for the verification and enhancement of mathematical knee-joint models. Knee-joint specimens in a six degree-of-freedom motion rig are moved through flexion under several combinations of external loads, including tibial torques, axial forces and AP-forces. Euler rotation angles and translation vectors, describing the relative, spatial motions of the joint are measured using an accurate Roentgen Stereo Photogrammetric system. Conceptually the joint is considered as a two degrees-of-freedom of motion mechanism (flexion-tibial rotation), whereby the limits of internal and external tibial rotation are defined at torques of +/- 3 Nm. The motion pathways along these limits are defined as the envelopes of passive knee joint motion. It is found that these envelope pathways are consistent and hardly influenced by additional axial forces up to 300 N and AP-forces of 30 N. Within the envelope of motion, however, the motion patterns are highly susceptible to small changes in the external load configuration. It is shown that the external tibial rotation during extension ('screw-home mechanism') is not an obligatory effect of the passive joint characteristics, but a direct result of the external loads. Anatomical differences notwithstanding, the inter-individual discrepancies in the motion patterns of the four specimens tested, showed to be relatively small in a qualitative sense. Quantitative differences can be explained by small differences in the alignment of the coordinate systems relative to the joint anatomy and by differences in rotatory laxity.

Adult↗
PubMed1988

Effects of preparation techniques on the porosity of acrylic cements.

We investigated four acrylic cement preparation techniques for their effects on cement porosity: hand mixing, pressurization in a pneumatic pistol, centrifugation, and vacuum mixing. All the techniques were tested on three types of cement with different viscosity characteristics. The best results were obtained with vacuum mixing using a newly designed experimental system, yielding porosity reductions of 60-80 percent relative to hand mixing. Vacuum mixing with a commercial system was also effective, but to a somewhat lesser extent. Pressurization and centrifugation had no substantial effect on the overall porosity. Centrifugation led to considerable nonuniformity in the distribution of pores and additives.

Bone Cements↗
PubMed1988

Primary fit of the Lord cementless total hip. A geometric study in cadavers.

Two Lord prostheses, bilaterally implanted in cadavers, were sectioned. The contact areas between bone and prosthesis were studied and measured using a specially developed reproducible method. Primary fixation of the femoral components appeared to be based principally on wedging of the prosthetic stem in the femoral shaft with a rather small contact surface. In both acetabuli the screw threads of the rings were only marginally in contact with the acetabular bone.

Acetabulum↗
PubMed1988

Vascular changes following hip arthroplasty. The femur in goats studied with and without cementation.

We studied two groups of 6 adult female African pygmy goats, which received cemented or uncemented femoral endoprostheses in their right hip. One additional goat was used for in vivo angiography preoperatively and postoperatively. The blood supply to the proximal femur at a macroscopic level was not severed by the operation. Until the 6th postoperative week, the animals were killed at weekly intervals. Microangiography and fluorescence microscopy revealed that rapid revascularization of the metaphyseal trabecular bone in the vicinity of the implants occurred as early as the first postoperative week in both groups. However, in general, the revascularization of the bone around the uncemented prostheses occurred more rapidly, resulting in earlier bone remodeling when compared with the cemented group. Surprisingly, the apposition of periosteal bone was longer lasting and more intensive in the uncemented group, particularly at the metaphyseal level. We suggest that this phenomenon may be enhanced by mechanical stimuli; the restoration of function was delayed in the noncemented goats.

Angiography↗
PubMed1987

Accuracy and reproducibility of instrumented knee-drawer tests.

Instrumented devices for knee-drawer tests have become popular in orthopaedics relatively recently. The objective of the present study was to document the effects of several parameters on the accuracy and reproducibility of anterior-posterior (AP) drawer measurements. An instrumented knee-drawer tester for AP laxity evaluations was constructed, based on the differential displacement method, measuring shifts of the tuberosity relative to the patella. The accuracy of the AP-shift was determined with the parallel use of a highly accurate roentgen stereo photogrammetric (RSP) measurement system on two postmortem leg specimens. The effects of relative motion between patella and femur were negligible. In addition to AP shifts, significant knee flexion and tibial rotations occurred, although the foot and the thigh were fixed as well as possible. The differential displacement method was effective in circumventing this problem. The accuracy of the AP shift was greater than 10%. The reproducibility of the AP drawer parameters (shifts and compliances) was determined in normal subjects and patients. Tests were made to evaluate the effects of different observers, time sequences, and different days. In addition, effects of muscle relaxation were studied. Overall, the shift parameters at different forces were found to be reproducible to between 5 and 15%. The slopes (compliances) of the laxity curves, at different forces, were found to be reproducible between 20 and 40%. The reproducibility was principally affected by deviations in the subject positioning procedure.

Biomechanical Phenomena↗
PubMed1987

Adaptive bone-remodeling theory applied to prosthetic-design analysis.

The subject of this article is the development and application of computer-simulation methods to predict stress-related adaptive bone remodeling, in accordance with 'Wolff's Law'. These models are based on the Finite Element Method (FEM) in combination with numerical formulations of adaptive bone-remodeling theories. In the adaptive remodeling models presented, the Strain Energy Density (SED) is used as a feed-back control variable to determine shape or bone density adaptations to alternative functional requirements, whereby homeostatic SED distribution is assumed as the remodeling objective. These models are applied to investigate the relation between 'stress shielding' and bone resorption in the femoral cortex around intramedullary prostheses, such as used in Total Hip Arthroplasty (THA). It is shown that the amount of bone resorption depends mainly on the rigidity and the bonding characteristics of the implant. Homeostatic SED can be obtained when the resorption process occurs at the periosteal surface, rather than inside the cortex, provided that the stem is adequately flexible.

Adaptation, Physiological↗
PubMed1987

Finite element analysis of acetabular reconstruction. Noncemented threaded cups.

The load-transfer mechanism and stress patterns in the acetabulum reconstructed with a threaded cup were investigated relative to the normal hip using the Finite Element Method (FEM). Several models were applied in the analysis to investigate the effects of axisymmetric 3-D versus 2-D approaches, inclusion of the femoral head, and local stress patterns around the threads in three types of implant/bone bonding modes. It was found that the threaded ring behaves as a relatively rigid implant shielding the trabecular bone and enhancing load transfer through the cortical shells. Load transfer from ring to bone is concentrated at the first and last threads where the subchondral bone layer is penetrated. Stress peaks of up to 24 MPa occur in these regions.

Acetabulum↗
PubMed1986

Guidelines for external fixation frame rigidity and stresses.

Using results from FEM analyses and experiments as references, analytical methods are applied to develop simple approximate formulas to relate frame rigidity, maximal pin stresses, and peak pin-bone stresses in external fracture fixation (EFF) configurations in axial loading to the most important frame, pin, and bone parameters. It is found that, in a realistic range, the parameters can be adapted to vary the frame rigidity from about 13 N/mm to 17,000 N/mm, thereby reducing the maximal stresses in the pins and at the pin-bone interface by a factor of 140. In particular, when compromises have to be established in the frame characteristics in order to ensure a flexible configuration and limit the stress values at the same time, the formulas presented can provide useful guidelines. The side-bar separation and the pin modulus, in particular, can be adapted to decrease the rigidity, while only moderately increasing the stresses, thereby reducing changes for pin failure, pin-bone loosening, and pin-tract infection. A nomogram is presented for a quick reference to estimated relations between frame characteristics, rigidity, and stresses. It is believed that this material may be of use in EFF design and applications in clinical and animal experimental trials.

Biomechanical Phenomena↗
PubMed1986

Substitution of the anterior cruciate ligament: a long-term histologic and biomechanical study with autogenous pedicled grafts of the iliotibial band in dogs.

This paper reports the experience with anterior cruciate ligament (ACL) substitution by standardized pedicled strips of the iliotibial band, fixed to the tibia and femur with a bone-peg fixation technique. Thirty-two young adult (+/- one year old) Labrador dogs were used for the experiments (58 transplant knees and six controls). The posttransplantation period ranged from day zero to three years postoperatively. Of the transplants, there were five failures. Forty-seven knees served for gross, photographic, and histologic examination. In 17 knees, the transplants were submitted to tensile testing in an Instron testing machine. The behavior of the ACL transplants was as follows: the transplants became necrotic in a short period of time, but after day four, a process of creeping substitution took place. At 12-16 weeks, a newly formed ligament was seen with a striking macroscopic resemblance to the normal ACL. However, its collagen fibers were coarser and more undulant, and they were fixed to the bony interfaces with Sharpey-like fibers. When these rather good-looking ACLs were subjected to mechanical testing and compared with normal ACLs, the results were less satisfactory. Mechanically, the substituted ACLs were 45% less stiff than normal ligaments, the yield point was at one-third, and the ultimate load was 40% of that of a normal ACL (deformation rate, 5 mm/min). Normal ACLs rupture at their tibial insertion. The transplants ruptured intraligamentarily. A striking finding was that the substituted ligament did not derotate when all the other ligamentous and capsular structures were cut. There was no torsional arrangement of their component bundles. Although the substituted ACL has an excellent histological and macroscopic appearance, its mechanical properties are inferior.

Animals↗
PubMed1985

Kinematic behavior of the human wrist joint: a roentgen-stereophotogrammetric analysis.

Using a roentgen-stereophotogrammetric measurement system, the three-dimensional kinematic characteristics of each carpal bone in two human wrist joints were obtained as the hands were moved in vitro through dorsopalmar flexion and through radioulnar deviation, both in the supinated and pronated positions of the hand. The results were described in terms of Euler rotation angles and showed that in flexion, the distal carpal bones may be considered as one fixed group while the proximal carpals may not. For the deviation motion, quite different rotational excursions for the carpal bones were observed, therefore, none of the two rows may be assumed acting as rigid groups. In both of the hand motions performed, all carpal bones moved synchronously and uniformly. These results demonstrate that accurate measurements of three-dimensional carpal-bone motions are feasible by using an adequately refined roentgen-stereophotogrammetric system. The detailed and precise kinematic information obtained can serve as a database for future developments of functional wrist-joint models, and will provide more insight into carpal-bone behavior, useful in clinical diagnosis and surgical reconstruction procedures.

Adult↗
PubMed1985

Parametric analyses of pin-bone stresses in external fracture fixation devices.

Problems occurring in the use of external fixators for bone fractures include pin-bone interface necrosis, infection, and loosening. These may be initiated and enhanced by pin-bone interface stress levels. Based on stress data from finite element method (FEM) models, an analytical "closed-form" model of the local pin-bone configuration in long-bone fracture fixation is developed. This model is relatively simple and useful for routine applications in combination with clinical studies and animal experiments. Although approximate, the most significant stress predictions in the pin-bone structure compare well with more sophisticated FEM analysis results. The analytical model is used for extensive parametric analyses, investigating the effects on the pin-bone interface stress distribution of frame configuration parameters, pin diameter and modulus, bone dimensions, and elastic characteristics. The results indicate that these stresses may reach very high levels under unfavorable circumstances but can be drastically reduced by increasing the bending rigidity of the pin, reducing the side-bar separation and applying full-pin configuration in favor of half-pins.

Bone and Bones↗
PubMed1985

Analytical stereophotogrammetric determination of three-dimensional knee-joint geometry.

An analytical stereophotogrammetric method is introduced to measure the three-dimensional geometry of articular surfaces in vitro. Information of this kind is particularly useful for mathematical joint models and anthropological studies. The method requires no specific equipment, such as a stereocomparator, contrarily to other techniques reported (e.g. Ghosh, 1983) and is relatively simple and inexpensive. The background of the method is outlined in the present paper, and results of accuracy and precision tests are presented. It is shown that an accuracy on the order of 0.2 mm (95% confidence interval) is well feasible in actual knee-joint evaluations, if the measuring procedure is conducted carefully. The method is illustrated by measuring and comparing the articular surface geometries of a bilateral pair of knee joints.

Biomechanical Phenomena↗
PubMed1985

Finite centroid and helical axis estimation from noisy landmark measurements in the study of human joint kinematics.

Recent work on joint kinematics indicates that the finite centroid (centre of rotation) and the finite helical axis (axis of rotation, screw axis, twist axis) are highly susceptible to measurement errors when they are experimentally determined from landmark position data. This paper presents an analytical model to describe these effects, under isotropic conditions for the measurement errors and for the spatial landmark distribution. It appears that the position and direction errors are inversely proportional to the rotation magnitude, and that they are much more error-prone than the relatively well-determined rotation and translation magnitudes. Furthermore, the direction and rotation magnitude errors are inversely proportional to the landmark distribution radius, and the position and translation magnitude errors are minimal if the mean position of the landmarks coincides with the centroid or helical axis. For the planar centroid, the use of rigid-body constraints results in considerable precision improvement relative to the classical, finite Reuleaux method for centroid reconstruction. These analytical results can be used to define suitable measurement configurations, and they are used in this paper to explain experimental results on Röntgenphotogrammetrically acquired in vitro wrist joint movement.

Biomechanical Phenomena↗