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At least 271 records · Page 15Linked to original sources

PubMed2002

Functional and morphological evaluation of a low-weight, monofilament polypropylene mesh for hernia repair.

With more than 1 million implantations per year worldwide, mesh repair has become a standard procedure for the treatment of hernias. Apart from various technical problems, the type of material has been proven to be of considerable importance for the functional and histological outcome, particularly for long-term implantation. Whereas the advantageous application of low-weight, large-pore meshes based on multifilaments can be stated without doubt, it is still open whether similar results can be achieved on the basis of pure monofilaments. In the present study, a low-weight polypropylene mesh (LW) made purely of monofilaments was compared to a common heavy-weight polypropylene mesh (HW) in regard to the functional consequences and the tissue response. After implantation in rats as an inlay for 3--90 days, the abdominal-wall mobility of the implant region was recorded by 3D stereography, and the tensile strength of both the suture zone and the mesh was measured. The morphometry of the histological reaction in regard to the inflammatory infiltrate, the connective tissue, the number of granulocytes, macrophages, and fibroblasts served to reflect the tissue response. As parameters for the remodeling process at the interface the cellular activation was evaluated by TUNEL (DNA-strand breaks or apoptosis, respectively), Ki 67 (cell proliferation), and HSP 70 (cell stress). The measured tensile strength of the LW mesh confirmed a sufficient strength of the material-reduced mesh modification. After implantation the consecutive impairment of the abdominal-wall mobility was reduced compared to the HW mesh, concomitant to the reduced fibrotic level at the interface. At the end of the observation period the foreign-body reaction was significantly lowered for the LW mesh, almost reaching physiological values. In conclusion, these data confirm the improved biocompatibility of material-reduced mesh implants.

Abdominal Wall↗

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↗

PubMed1987

Three-dimensional spinal curvature in idiopathic scoliosis.

Scoliosis is usually considered as a deformity of the spine in the frontal plane, without reference to curvatures in other planes. In this study, the three-dimensional shape of the spine of 104 patients with untreated idiopathic scoliosis (5-55 degrees Cobb) was studied by means of stereo radiographs to determine relationships between curvature of the spine in the frontal plane view, in the lateral view, and in the intermediate views. There was a weak but statistically significant correlation (r = 0.2) relating greater scoliosis with lesser kyphosis or greater lordosis. In the thoracic region, the sagittal plane spinal curvature was less than that measured in a population without scoliosis (mean difference, 7.72 +/- 9.9 degrees). Seventy-four of 76 scolioses in the upper region of the spine with lateral curvature greater than 5 degrees Cobb were kyphotic. Sixty-four of 84 curves greater than 5 degrees Cobb in the lower region were lordotic. Measuring curvatures in the plane of symmetry of the rotated apical vertebra altered these ratios to 69 of 76 kyphotic in the upper region and 68 of 84 lordotic in the lower region. The plane of maximum curvature of sections of the spine with scoliosis was not related to the plane of symmetry of the rotated apical vertebra, for in kyphotic regions of the spine the rotations of these two planes were in opposite directions. In all cases, the magnitudes of the rotations were quite different, i.e., by a factor of -0.22 for curves in thoracic region and by a factor of 0.24 for curves in the lumbar region. This implies that mechanical measures to correct this spinal deformity or to prevent progression should apply different rotations to the apex from those applied to the curve as a whole and, in opposite senses, in curves in kyphotic regions. There was no evidence of an abnormality of sagittal curvature of a magnitude to implicate it in the etiology or in the treatment.

Adolescent↗

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↗

PubMed1988

Spinal deformity and back surface asymmetry in idiopathic scoliosis.

Stereo radiography and stereotopography were used to record simultaneously the three-dimensional spinal and back surface shape of 141 patients with a clinical diagnosis of adolescent onset idiopathic scoliosis. Radiography confirmed 80 patients with single lateral curves (Cobb angle 5-87 degrees); 59 with double curves (Cobb angle 5-61 degrees), and two patients with triple curves. Orientation of each vertebra was measured by the lateral deviation from the spinal axis and the axial rotation. For each curve detected, the Cobb angle, the maximum deviation, the maximum axial rotation, and the sagittal plane curvature was measured. Topographic data were used to generate a profile of a cross-section through the back of each vertebral level. This section was characterized by its axial rotation, deviation of its midpoint from the spinal axis, and area symmetry about the midpoint. Maximum values of these measurements in the region of each radiographic scoliosis curve were noted. Regression and correlation analysis showed (for each curve) a high correlation of apical vertebral lateral deviation with back surface axial rotation (r = 0.79) and with vertebral axial rotation (r = 0.79). The back surface rotation was less than vertebral rotation in magnitude, however, by a mean factor of 0.55. The measurement of the back surface asymmetry that gave the highest correlation with the skeletal deformity was the axial rotation. Relationships between skeletal and surface measures were similar for curves in thoracic and lumbar regions and for patients with single and double curves. There is potential for clinical application of surface measurement techniques to prescription of orthoses and monitoring of changes due to progression or treatment.

Adolescent↗

PubMed1988

Kinematics of the cervical spine: effects of multiple total laminectomy and facet wiring.

The effect of multiple-level total laminectomies followed by stabilization on the load-deformation behavior of the cervical spine is described. Fresh human ligamentous cervical spines (C2-T2) were potted and clinically relevant load types applied via a loading frame attached to the C-2 vertebra of the specimen. A set of three infrared light-emitting diodes (LEDs) were attached rigidly to each of five vertebrae (C3-7) to record their spatial locations after each load step application, using a Selspot II system. The specimen was tested again after total laminectomy performed on C5. The supraspinous, interspinous, and flavum ligaments between the C4-5 and C5-6 motion segments were cut; thereafter, the vertebral arch was removed. The specimen testing was resumed after inducing injury at C-6 in a similar fashion. The specimen was stabilized, using a facet wiring construct, across the C4-7 segment before testing for the final time. The load-deformation data of the injured and stabilized tests were normalized with regard to the corresponding results of the intact test. In flexion-extension mode, an increase in motion of about 10% after laminectomies was observed. Facet wiring was found to be an effective technique to stabilize injured cervical spines (approximately equal to 80% reduction in motion, compared with intact spines, was observed.

Biomechanical Phenomena↗

PubMed1990

The three-dimensional tracking pattern of the human patella.

A study was undertaken to provide data on the three-dimensional tracking pattern of the patella, relative to the femur, in human knee-joint specimens. For this purpose, a highly accurate roentgen stereophotogrammetric analysis (RSA) method was applied. The three-dimensional motion patterns of the tibia and the patella were measured and represented in terms of three translations and three rotations each, during knee flexion in neutral (unloaded), endorotated, and exorotated pathways. We found that the patella displays complex but consistent three-dimensional motion patterns during flexion, which include flexion rotation, medial rotation, wavering tilt, and a lateral shift relative to the femur. The motion patterns are very much affected by tibial rotations accompanying flexion.

Humans↗

PubMed1991

Human carpal ligament recruitment and three-dimensional carpal motion.

In five fresh human cadaver wrist joints six carpal ligaments and seven carpal bones were marked with small, radio-opaque pellets. Using a roentgenstereophotogrammetric measuring system, the ligamentous length changes and the kinematics of carpal bones were determined in different flexion and deviation positions of the hand. The data generated by this method differ significantly from lengthening data predicted by current concepts on carpal ligament functioning. The motions of carpal bones and the lengthening of the carpal ligaments were related to each other. It appeared that most carpal ligaments lengthen only during one half of a full movement cycle. Hence, ligaments seem to constrain either a dorsal- or a palmar-directed motion of the hand, or an ulnar- or a radial-directed motion of the hand. When the hand is in maximal radial deviation or maximal palmar flexion, none of the ligaments has a greater length than in the neutral situation. The tested parts of the lunatotriquetrum palmar ligament do not lengthen during any movement of the hand. Significant lengthening relative to the neutral situation was found for the radiocapitate palmar ligament (6.5% in maximal ulnar deviation and 11.7% in maximal dorsal flexion of the hand), and for the distal string of the radiolunate palmar ligament (6.4% in maximal ulnar deviation). It was confirmed that the carpals, apart from moving in the plane in which the hand motion takes place, also execute considerable out-of-plane motions during hand motions. The combination of these experimentally and simultaneously determined data on length change and on the movements of carpal bones are found to be necessary in order to give suitable explanations for the observed separate kinematical phenomena.

Carpal Bones↗

PubMed1992

Quantitation of in situ contact areas at the glenohumeral joint: a biomechanical study.

Glenohumeral arthritis may result from abnormal articular mechanics, and shoulder reconstructive procedures often rely implicitly on the belief that the restoration of normal articular mechanics is required to obtain satisfactory clinical results. Despite this, limited knowledge of normal or pathologic glenohumeral joint articular mechanics and contact is available. This study uses a stereophotogrammetry technique to determine contact areas in normal cadaver glenohumeral joints with intact ligaments and capsule through a large range of motion using simulated forces of the four rotator cuff muscles and three deltoid heads. All shoulders were first elevated to their maximum elevation in the scapular plane at an external rotation (starting rotation = 40 +/- 8 degrees), which allowed each shoulder to attain its maximal elevation in the scapular plane, and then repeated at 20 degrees internal to this rotation. Contact areas consistently increased with increasing elevation until 120 degrees to an average of 5.07 cm2 before decreasing with further increased elevation to an average of 2.59 cm2 at 180 degrees of total arm elevation. At 20 degrees internal to the starting rotation, contact areas reached high values 60 degrees earlier (averaged 4.56 cm2 at 60 degrees of total arm elevation) and then remained fairly constant through 120 degrees before decreasing with further increased elevation to 2.51 cm2 at 180 degrees total arm elevation. With increasing elevation in the external starting rotation, humeral head contact dramatically migrates from an inferior region to a superocentral-posterior region while glenoid contact shifts posteriorly. When the humeral shaft is positioned 20 degrees internal to the starting rotation, humeral head contact shifts from inferocentral-anterior to superocentral-posterior regions. Simultaneously, a similar posterior shift in glenoid contact is observed. Furthermore, whereas only a small portion of the humeral head surface area is in contact in any given position, contact on the glenoid surface is much more uniformly distributed over its entire articulating surface.

Aged↗

PubMed1992

Three-dimensional mechanical properties of the thoracolumbar junction.

The thoracolumbar junction region is a frequent site of spinal trauma. Accurate knowledge of the normal mechanical behavior of the intervertebral joints in this region is of importance to the clinician in treating the spinal injuries. The present study documented the complete three-dimensional motions of levels T11-T12 and T12-L1 in the thoracolumbar region. Pure moments of flexion/extension, bilateral axial torque, and bilateral lateral bending were applied to 11 three-vertebrae human cadaveric specimens (T11-L1) to a maximum of 7.5 Nm. Intervertebral motions were calculated using stereophotogrammetry and presented in the form of load-displacement curves, each containing three rotations and three translations at one intervertebral level. Average +/- SD flexion, extension, axial rotation, and lateral bending ranges of motion to one side were 2.7 +/- 1.3 degrees, 2.4 +/- 1.3 degrees, 1.8 +/- 0.7 degrees, and 3.5 +/- 1.1 degrees, respectively, at level T11-T12. The same ranges of motion at T12-L1 were 2.9 +/- 1.4 degrees, 3.9 +/- 1.4 degrees, 1.2 +/- 0.7 degrees, and 3.7 +/- 1.1 degrees, respectively. The extension and axial rotation ranges of motion at level T11-T12 were found to be significantly different than the same motions at T12-L1. The different geometry in the facet joints explains these observed differences in the mechanical behavior of T11-T12 and T12-L1.

Adult↗

PubMed1992

Migration of porous coated acetabular prostheses fixed with screws: roentgen stereophotogrammetric analysis.

The fixation of screw-fixed, porous-coated acetabular prostheses was studied during 2 years in 21 patients (22 hips) using repeated roentgen stereophotogrammetric measurements. Migration of the center of the prostheses and/or tilting were recorded in five cups after 6 months. Two years after operation, migration was recorded in three, migration and rotation in six, and only rotation in three cups. Bone quality, prosthetic position, and immediate postoperative radiographic appearance of the prosthesis-bone interface did not correlate with the occurrence of migration. Narrow radiolucent zones had developed in half of the patients after 2 years and was associated with proximal migration. Micromovements of screw-fixed, press-fit cups seem to start later compared with previously presented results from cemented acetabular prosthesis.

Acetabulum↗

PubMed1992

Strains and forces in selected carpal ligaments during in vitro flexion and deviation movements of the hand.

The forces induced in tiny wrist joint ligaments must be estimated in order to understand their role in the mechanism of the joint. We estimated forces in a number of selected ligaments in seven human wrist joint specimens, using a noninvasive method. The method is based on the rationale that the force generated in a ligament depends on its change of length with the joint under load. In vitro length changes of the ligaments were determined during flexion and deviation movements of the hand, using a roentgenstereophotogrammetric analysis technique. Subsequently, bone-ligament-bone (BLB) preparations were dissected from the specimens. From these BLB preparations the zero-force length and the force-elongation relationship were determined in a material testing machine. The forces generated in the ligaments during flexion and deviation were calculated by combining results on the in vitro ligament length changes, the zero-force length, and the force-elongation relationship. Large interspecimen variations of the force patterns were found. Due to this variability, it is not possible to obtain quantitative models for the kinetic behavior of the ligaments. However, qualitative trends could be distilled from the strain and force patterns. It is clear that for most ligaments, the zero-force lengths were not equal to the lengths they possessed in the neutral position of the hand. Furthermore, it could be shown which motions of the hand would most likely strain a particular ligament. It could be shown that the variations in the force patterns originate mainly from variations in the zero-force lengths, and from variations in the force-strain relationship between specimens.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1993

Early postoperative fixation of tibial components: an in vivo roentgen stereophotogrammetric analysis.

The fixation of cemented and noncemented tibial components in 19 total knee arthroplasties was examined 3 to 10 weeks postoperatively with roentgen stereophotogrammetric analysis. Physiologic external forces were applied either in outward-inward rotation or as eccentric posterior loading generated by squatting. In one case there was no motion, while in the remaining 18 cases relative interface motion of up to 1.3 mm was found. In some cases, the largest motion was found during inward-outward rotatory stress, while in others, the largest motion was found during squatting. Posterior tilt was weakly correlated with posterior displacement of the femoral component on the tibia during squatting (r2 = 0.323, p < 0.05). For the noncemented cases, the initial fixation to bone was probably insufficient, and ingrowth of bone would not have been achieved. For the cemented cases, motion of the implant was reduced. Given the short postoperative time and the probable absence of any substantial fibrous tissue membrane, we suggest that the observed motion represented elastic deformation of the bone.

Aged↗

PubMed1997

Roentgen stereophotogrammetric analysis of metal-backed hemispherical cups without attached markers.

A method for the detection of micromotion of a metal-backed hemispherical acetabular cup is presented and tested. Unlike in conventional roentgen stereophotogrammetric analysis, the cup does not have to be marked with tantalum markers; the micromotion is calculated from the contours of the hemispherical part and the base circle of the cup. In this way, two rotations (tilt and anteversion) and the translations along the three cardinal axes are obtained. In a phantom study, the maximum error in the position of the cup's centre was 0.04 mm. The mean error in the orientation of the cup was 0.41 degree, with a 95% confidence interval of 0.28-0.54 degree. The in vivo accuracy was tested by repeated measurement of 21 radiographs from seven patients. The upper bound of the 95% tolerance interval for the translations along the transversal, longitudinal, and sagittal axes was 0.09, 0.07, and 0.34 mm, respectively: for the rotation, this upper bound was 0.39 degree. These results show that the new method, in which the position and orientation of metal-backed hemispherical cup is calculated from its projected contours, is a simple and accurate alternative to attaching markers to the cup.

Acetabulum↗

PubMed1999

Three-dimensional knee kinematics and stability in patients with a posterior cruciate ligament tear.

The three-dimensional kinematics of the knee were studied from 5 months to 15 years after unilateral posterior cruciate ligament tears occurred in eight patients. All but two patients had signs of additional ligament injuries. Repeated radiostereometric examinations were conducted when the patients ascended a platform (step-up test) and during an instrumented anterior-posterior drawer test with the knee at 30 degrees of flexion. No changes in knee kinematics were observed during the step-up test, whereas increased anterior-posterior laxity (3.8-11.3 mm) was recorded for all patients. Four of the patients had an increased side-to-side difference (more than 2 mm) in anterior as well as posterior laxity. A rupture of the posterior cruciate ligament can be diagnosed at 30 degrees of knee flexion, but an increase in anterior laxity can erroneously be interpreted as an injury of the anterior cruciate ligament. The unaffected kinematics of the knee suggest that factors such as joint load and congruity and muscle activity can compensate for the absent posterior cruciate ligament during static examinations.

Adolescent↗

PubMed1999

Failure of partial cementation to achieve implant stability and bone ingrowth: a long-term roentgen stereophotogrammetric study of tibial components.

Thirty patients with gonarthrosis were operated on with the PCA primary total knee prosthesis and had the tibial component fixed to the bone by partial cementation. In the first two groups of patients, cementation was by a peripheral rim of high and low-viscosity cement, respectively. In the third group, the pegs were cemented with the low-viscosity cement. Follow-up was performed with use of clinical parameters and roentgen stereophotogrammetric analysis. Clinically, the series was successful apart from a problem with tibial component wear, necessitating revision in five patients. At 8 years, the mean Hospital for Special Surgery score was 81 points. Venn-diagram scores revealed four failures and three acceptable cases; the remaining cases were satisfactory. Apart from one loose patellar component, there was no mechanical loosening. Roentgen stereophotogrammetric analysis showed that the tibial components moved relative to the bone; this indicated fibrous tissue fixation, which was corroborated histologically in two patients. The objective, to achieve bone ingrowth, was thus not successfully met. Radiolucent lines were consistently seen, and their size correlated with the migration as measured by roentgen stereophotogrammetric analysis. Furthermore, five continuously migrating prostheses showed significantly larger radiolucent zones than the prostheses that migrated only initially, and they were less well bonded to the bone at 1 year. In conclusion, partial cementation does not appear to be a way to achieve bone ingrowth in porous-coated implants under load.

Aged↗

PubMed1980

The operating microscope. IV. Documentation.

The methods of documenting microsurgical procedures with 35-mm photography, Super 8 (8-mm) and 16-mm motion pictures, and television are discussed for the Zeiss OPMI 1, OPMI-6-S, and OPMI 7 P/H.

Evaluation Studies as Topic↗

PubMed1977

Vascular and glomerular changes in the ageing kidney.

Glomerular size, shape and number were examined in 44 human kidneys obtained at necropsy. Intrarenal vascular appearances were assessed histologically and by post-mortem angiography. The mean cross-sectional area of glomeruli varied nearly three-fold and glomerular number varied more than three-fold when kidneys from different adult subjects were compared but kidneys from the same subject resembled one another in glomerular size and number. A significant negative correlation existed in the adult between glomerular number and dimensions. Glomerular numbers in the few immature kidneys studied were similar to those in adult kidneys but glomeruli were smaller. Glomerular numbers tended to decline as age and severity of age-related vascular changes increased but correlation was poor. The possibility remains that glomerular involution in the senescent kidney occurs independently of events in the vessels. In men, but not in women, totally hyalinised glomeruli were observed more frequently with increasing age but their presence did not appear to be related to the degree of vascular change. In the senescent kidney, glomerular lobulations tended to disappear. This, together with glomerular loss, must result in a reduction in the area available for filtration. Assessments of total glomerular surface area should take account of glomerular shape and dimensions as well as numbers.

Adult↗