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Biomedical subjects

L Ryd

Publications and source records attributed to L Ryd.

At least 19 recordsLinked to original sources
PubMed1999

Major bone transplantation in total knee arthroplasty: a 2- to 9-year radiostereometric analysis of tibial implant stability.

Eight total knee arthroplasties involving major bone grafting to repair noncontained defects of the proximal tibia were studied. In all knees, autologous bone was used. Cement was used for implant fixation. At follow-up evaluation 5 years after surgery, 7 knees had excellent results, and 1 had fair results; the mean Hospital for Special Surgery score was 84. Radiostereometric analysis showed a mean migration of 0.5 mm (range, 0.2-1.5 mm). None of the knees in which major structural autologous bone grafting was used showed increased micromotion of the adjacent tibial implant.

Aged↗
PubMed1998

The use of isolated patellar prostheses in Sweden 1977-1986.

During 1977 to 1986, 106 patients had isolated patellar prostheses, with both patellar and femoral components, inserted in 20 different hospitals in Sweden. At follow up, 7 years (range 3 to 14 years) after operation, 9 patients had died so that 97 patients with operations on 113 knees were included in this study. Thirty-three (38 knees) had been operated on before or after a prosthesis had been inserted. At follow-up, 75% were satisfied with the operation; 83% had improved, 59% could walk without an aid and 44% had no, or only occasional, pain in the knee. These results encourage the use of an isolated patellar prosthesis in cases of advanced and disabling localised patellar arthrosis. There is no place for this operation in the treatment of chondromalacia.

Adolescent↗
PubMed1998

Longitudinal and cross-sectional variability in markers of joint metabolism in patients with knee pain and articular cartilage abnormalities.

OBJECTIVE: To determine the within- and between-patient variability in the concentrations of synovial fluid, serum and urine markers of joint tissue metabolism in a cohort of patients with knee pain and cartilage changes consistent with early-stage knee osteoarthritis. DESIGN: Samples of synovial fluid, serum, and urine were obtained from 52 patients on eight different occasions during 1 year, as part of a clinical trial in patients with cartilage abnormalities and knee pain. In joint fluid, aggrecan fragments were quantified by dye precipitation and enzyme-linked immunosorbent assay (ELISA), and matrix metalloproteinases-1 and -3, and tissue inhibitor of metalloproteinases-1 by sandwich ELISAs. In serum, keratan sulfate was quantified by ELISA. Type I collagen N-telopeptide cross-links in urine were determined by ELISA. RESULTS: The degree of cross-sectional variability in marker concentrations did not vary between the different sampling occasions, and did not differ between the periods of weeks 0 (baseline), 1-4 (treatment) and 13-26 (follow-up). Both between-patient and within-patient coefficients of variation varied for markers in different body fluid compartments, with the lowest variability for serum keratan sulfate, followed by urine type I collagen N-telopeptide crosslinks, and the highest for synovial fluid markers. For synovial fluid, aggrecan fragments showed the least variability, and matrix metalloproteinases the highest. One patient with septic arthritis showed a fivefold peak increase in joint fluid aggrecan fragment concentrations, while the concentration of matrix metalloproteinase-3 increased 100-fold. CONCLUSIONS: Molecular markers of joint tissue metabolism have been suggested as, for example, outcome measures for clinical trials of disease-modifying drugs in osteoarthritis. This report is the first to present data on between- and within-patient variability for such molecular markers in three different body fluid compartments in stable cohort of patients. The availability of such data enables calculations to determine the number of patients needed in prospective studies using these markers as outcome measures.

Adult↗
PubMed1998

Simultaneous measurements of sagittal knee laxity with an external device and radiostereometric analysis.

We obtained simultaneous measurements of sagittal knee laxity in 12 consecutive patients after reconstruction of the anterior cruciate ligament (ACL), using the Stryker laxity tester and radiostereometric analysis (RSA). The mean anteroposterior (AP) displacement when a 90 N load was applied in both directions was 5.3 +/- 2.7 mm with RSA and 9.8 +/- 1.6 mm with the external device (p < 0.001). The corresponding measurements at a load of 180 N were 5.7 +/- 2.4 mm and 13.8 +/- 3.7 mm, respectively (p < 0.001). More than 50% of the sagittal knee movement, as measured by the external device at a load of 180 N, was not true femorotibial displacement of the joint but was due to soft-tissue deformation.

Adolescent↗
PubMed1998

Fixation of the tibial component of total knee arthroplasty after high tibial osteotomy: a matched radiostereometric study.

To assess migration of the tibial component we used roentgen stereophotogrammetric analysis in 40 patients who had had a total knee arthroplasty after failure of a closing wedge osteotomy and compared them with 40 matched patients after primary total knee arthroplasty. We found no difference in migration over time or in the tendency for continuous migration between the two groups. There were no differences in alignment or position of the knee prosthesis or in the clinical outcome. Our findings show that revision of a failed high tibial osteotomy to a total knee arthroplasty is effective.

Aged↗
PubMed1998

Assessment of image post-processing and of measuring assistance tools in computed radiography. Evaluation of the weight-bearing knee.

PURPOSE: A system for the examination and measurement of the weight-bearing knee was adapted to computed radiography (CR) and to a picture archiving and communication system (PACS). The examination and measurement system was developed on examination equipment used for QUESTOR precision radiography (QPR). For an easier and more standardised localisation of bony landmarks on the screen, 4 measuring assistance tools (MATs) were developed. The aim of this study was to evaluate the usefulness of the tools developed and of image post-processing, specifically as magnification (zoom) and filtering (edge enhancement), by determining intra-observer variation in the measurement of angles and distances. MATERIAL AND METHODS: The original QPR measurement program, generating 19 angles and distances corrected for parallax and magnification, was converted and installed on a multi-modality workstation (Imtec Image 1200). A CR system (Fuji AC-2) was used for the generation of the related images and the measurements were made on the workstation. Four unilateral examinations of weight-bearing knees were undertaken. These examinations were measured twice under 5 different measurement conditions by 4 viewers. RESULTS AND CONCLUSIONS: The most important factor in reducing intra-observer variation was the ability to magnify (zoom) the images. The MATs also reduced variation. Filtering (edge enhancement), however, did not affect precision.

Biomechanical Phenomena↗
PubMed1998

Early inducible displacement of tibial components in total knee prostheses inserted with and without cement: a randomized study with roentgen stereophotogrammetric analysis.

The fixation of tibial components randomized to insertion with or without cement in twenty-six knees was examined for inducible displacement at six weeks and one year postoperatively with use of roentgen stereophotogrammetric analysis. Furthermore, migration was studied during the first two postoperative years. Inducible displacement was found in all knees at both the six-week and the one-year follow-up examination, but no differences were detected with respect to the type of fixation (p > 0.05). All tibial components migrated for as long as one year postoperatively, after which most stabilized. No difference was found between the groups with respect to migration during the first two years postoperatively (p > 0.05), with the exception of subsidence of the component, which was found to be 0.0+/-0.1 millimeter (mean and standard error of the mean) for the components inserted with cement and 0.5+/-0.1 millimeter for the components inserted without cement (p < 0.01). Migration after one year was the same for both groups. We found a relationship between inducible displacement at six weeks and at one year as well as one between inducible displacement and migration at one year. To our knowledge, the present study is the first in which the micromotion of an interference-fit prosthesis was found to be similar to that of a device inserted with cement. The results of the present study emphasize the importance of the initial prosthetic fixation.

Aged↗
PubMed1997

Error propagation for relative motion determined from marker positions.

In this paper, the error propagation for relative motion reconstructed from noisy marker position data was investigated, particularly the influence of the distance between two rigid bodies was explored. Based on a mathematical derivation, an error propagation model for relative motion was proposed and computer simulations were used to validate the proposed model. The results indicated that the error in the translation components for relative motion between two rigid bodies are proportional to the distance between the rigid bodies. The maximum absolute difference between the model and the simulation is 0.58% which strongly validated the accuracy of the error propagation model.

Computer Simulation↗
PubMed1997

Wear in retrieved condylar knee arthroplasties. A comparison of wear in different designs of 280 retrieved condylar knee prostheses.

The plastic components of 280 retrieved unicondylar and total knee arthroplasties were studied. Wear was visually scored using a relative ranked data method. Although wear on the components was highly variable, several conclusions could be drawn regarding the nature and causes. Wear was associated more with the medial than the lateral condyle. Delamination was the most severe type of wear and occurred in short (< 5 year)-, medium (5-10 years)-, and long (> 10 years)-term retrievals. In the short term, delamination wear was associated with hot pressing of the tibial plastic or with fracture of the tibial baseplate. For a single design, a significant difference in the amount of delamination on hot-pressed and non-hot-pressed tibial components was observed. In medium- and long-term retrieved specimens of the designs with moderately high conformity, delamination wear was associated with restriction of rotational movement of the femoral component or with abrupt changes in the radius of the tibial component. In flatter, less conforming designs, wear was associated with laxity, such that the polyethylene delaminated toward the edges of the tibial component. Wear attributed to cement abrasion or entrapment occurred on the more conforming designs. Delamination was associated with the presence of fusion defects in the polyethylene but could also occur in the absence of such defects. That delamination was the principal were type and that this is caused by a fatigue mechanism mean that the incidence of failure could accelerate considerably over follow-up periods beyond 10 years. Designs of moderate conformity without abrupt changes in radii may prolong the duration of plastic tibial components before serious delamination occurs.

Cementation↗
PubMed1997

Computed radiography for characterisation of the weight-bearing knee.

PURPOSE: A new method for examining and measuring the weight-bearing knee in computed radiography (CR) and picture archiving and communication systems (PACS) has recently been developed on examination equipment used in QUESTOR Precision Radiography (QPR). QPR is a method for the standardised examination of the knee, and generates 9 angles (e.g. hip-knee-ankle (HKA) angle) and 10 distances, corrected for parallax and magnification. The aim of this present study was to evaluate the reproducibility of this newly developed method and to determine intra- and interobserver variation in its measurements. MATERIAL AND METHODS: The images were generated on a CR system, archived, and transferred to a multimodality work-station that had a monitor with a resolution of 1280x1024 (1kx1k). Photostimulable phosphor plates were used to generate images with a matrix of 1760x2140 pixels (pixel size 0.2 mm, corresponding resolution 2.5 1p/mm). Ten volunteers without knee problems were examined twice, bilaterally, by 2 different radiology technologists. RESULTS: The total reproducibility of the method was good, offering an HKA reproducibility of +/-2.64 degrees in slight flexion and +/-1.62 degrees in extension, at 95% confidence. The intra- and inter-observer variations were low with a reduction of the intra-observer variations in all measurements (except one) by a factor of 2.8 on average compared with the original QPR method for conventional film-screen radiography. CONCLUSION: When QPR is modified for CR, it fulfils the requirement of reproducibility in measurements of the weight-bearing knee.

Adult↗
PubMed1997

Persistent stability 3 years after reconstruction of the anterior cruciate ligament. A radiostereometric analysis (RSA) of 20 patients.

We measured, by radiostereometric analysis (RSA), the sagittal knee laxity in 20 consecutive patients with chronic anterior cruciate ligament injuries before, 1 year and 3 years after reconstruction with a free bone-patellar tendon-bone graft. The grafts had been perioperatively tensioned, using a 10-15 N load. An increased displacement with increasing load was present before reconstruction, but we found no differences between 100 and 150 N stress load 1 and 3 years after the operation. The total anteroposterior displacement decreased from 12.7 mm before the reconstruction to 5.1 mm 1 year and 5.6 mm 3 years postoperatively, using a stress load of 150 N. Thus, we found both a definite end-point of joint displacement and persistent stability without elongation of the graft with time, when care was taken not to over-constrain the knee by a high initial graft tension.

Adult↗
PubMed1997

Knee scoring systems in gonarthrosis. Evaluation of interobserver variability and the envelope of bias. Score Assessment Group.

10 experienced orthopedic surgeons assessed 15 patients using 3 commonly used composite scoring systems and by some simple variables to evaluate knee replacements. Statistical evaluation showed that the scores were valid and reflected the disease process with a reasonable reproducibility. In the individual case, however, considerable changes of the total scores and the simple variables are needed to represent a true difference at the 95% confidence limit. The coefficient of repeatability varied from 45 to 72 for the scores. Our study, which is suggested to represent any clinical investigation, showed that clinical measurements are not robust and meticulous efforts in terms of study design must be made to protect an investigation against the action of bias. Knee scores are exceedingly unreliable.

Aged↗
PubMed1997

Effects of lamination on the strength of bone cement.

To improve cement penetration into the cancellous bone of the acetabulum in hip arthroplasty, sequential cementation of each anchoring hole may be feasible. Since this procedure creates laminations in the cement, we have determined the conditions under which such laminations affect the strength of the cement. Cement bars made at 2, 3 or 4 minutes after the start of cement mixing and with either dry laminations or laminations including blood or saline were tested for tensile strength. Solid unlaminated bars were used as references. Dry and saline laminations made up to 4 minutes after the start of cement mixing did not reduce the strength of the cement. However, there was a time-dependent decrease in cement strength if blood was entrapped in the interface. In such cases, there was a decrease in strength for laminations made at 4 minutes, at 3 minutes this was less pronounced and at 2 minutes no weakening at all was noted. Our findings indicate that a sequential cementation procedure is permissible as regards cement strength, provided it is performed with 2-3 minutes after the start of cement mixing. If the cement area is kept free from blood, the time may be prolonged up to 4 minutes, without the risk of weakening the cement strength.

Biomechanical Phenomena↗
PubMed1997

Quality of life after knee arthroplasty. A randomized study of 3 designs in 42 patients, compared after 4 years.

We assessed different yardsticks for outcome 4 (3-5) years after surgery in a prospective, randomized study of 42 patients, where 3 designs of cemmentless knee prostheses were used. The prognosis with regard to loosening, previously obtained by radiostereometry after 2 years of follow-up, was utilized. Patients with a prognosis of stable implant fixation (two thirds) were compared with those where loosening was predicted (one third). Hospital for Special Surgery score and Visual Analogue Scales regarding pain at rest, "first step" pain, pain during activity and global function, showed consistent postoperative improvements, but no differences between the design and prognosis groups were found. Radiolucent lines were registered both as yes/no and number of zones. Lines and prognosis were associated, but not lines and design groups. Quality of life assessment by the Nottingham Health Profile questionnaire showed that the poor prognosis group had increased pain and significant disturbances of sleep and emotions, as well as difficulty in enjoying hobbies and holiday activities. No differences were found between the design groups. Altogether, the patients showed profiles comparable to a healthy reference group. We conclude that the Nottingham Health Profile is a sensitive, relevant and simple measure of outcome after knee arthroplasty.

Activities of Daily Living↗
PubMed1996

The Porous-Coated Anatomic total knee experience. Special emphasis on complications and wear.

One hundred sixty knees in 141 patients with the Primary Porous-Coated Anatomic prosthesis (Howmedica, Rutherford, NJ) were evaluated after a follow-up period of 5.6 years (range, 1-10 years). One hundred six knees were in the latest follow-up evaluation, including clinical examination and a defined standing radiograph with a follow-up period of 6.3 years (range, 3-10 years). Survivorship analysis regarding the cumulative revision rate (including completion with a patellar component) was 0.88 at the 8-year and 0.84 at the 10-year follow-up examination. The clinical result was satisfying/good, with a mean Hospital for Special Surgery score of 83 (range, 39-97). Five percent had thinning greater than 30% of the tibial component. The wear was calculated to be 1.0 mm (range, 0-9 mm), including three revised tibial components with heavy wear. Excluding the revised cases, the wear was 0.7 mm.

Aged↗
PubMed1996

Intra-articular hyaluronan injections in the treatment of osteoarthritis of the knee: a randomised, double blind, placebo controlled multicentre trial. Hyaluronan Multicentre Trial Group.

OBJECTIVE: To assess the effects of intra-articular injections of hyaluronan on symptoms of knee osteoarthritis (OA). METHODS: Two hundred and forty patients with symptomatic, radiological knee OA were randomly assigned to treatment with weekly injections for five weeks with either 25 mg of high molecular weight hyaluronan or vehicle. Results were evaluated at weeks 1, 2, 3, 4, 5, 13, and 20 by visual analogue scales (pain, function, motion, activity), algofunctional index, and global evaluation by patient and investigator. Analysis was by "intention to treat', "per protocol', and area under the curve principles on unstratified patient groups and for patients stratified into four groups of equal size by age and baseline algofunctional index. RESULTS: No serious side effects were reported. At 20 weeks both treatment groups were improved compared with baseline, with no difference between unstratified groups treated with placebo or hyaluronan. Comparison of treatment groups stratified by age and baseline algofunctional index revealed a significant difference in favour of hyaluronan over placebo (pain, activity, algofunctional index, global evaluations by patient and investigator) for patients older than 60 years and with a baseline algofunctional index greater than 10. There was no clinically relevant difference between the two treatments for the other three stratified subgroups of younger age or fewer symptoms. Similar results were obtained by area under the curve, intention to treat, and per protocol analysis. CONCLUSIONS: Patients older than 60 years with knee osteoarthritis and with significant symptoms corresponding to an index of severity of knee disease of 10 or more, comprise the group most likely to benefit from treatment with intra-articular hyaluronan injections.

Adult↗