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Biomedical subjects

L Ryd

Publications and source records attributed to L Ryd.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1996

Angular configuration of the knee. Comparison of conventional measurements and the QUESTOR Precision Radiography system.

PURPOSE: The aim of this study was to assess the QUESTOR Precision Radiography system (QPR) and to compare it with the routine hip-knee-ankle (HKA) angle measurements. The aim was also to evaluate the robustness of the QPR system against the osseous changes of arthrotic disease. MATERIAL AND METHODS: Twenty-four patients, operated on with a high tibial osteotomy for medial gonarthrosis, were examined. The alignment of the leg was measured by the conventional technique and by the QPR method. RESULTS AND CONCLUSION: The 2 methods correlated well. The intraobserver variation in the QPR measurements was, with the exception of the capito-midcondylar-femoral shaft angle and the tibial plateau width, not affected by the osseous changes inflicted by the arthrotic process. The patients tolerated both systems well while the staff preferred the QPR system.

Ankle↗
PubMed1996

Knee joint loading and tibial component loosening. RSA and gait analysis in 45 osteoarthritic patients before and after TKA.

We report a prospective study of gait and tibial component migration in 45 patients with osteoarthritis treated by total knee arthroplasty (TKA). Migration was measured over two years using roentgen stereophotogrammetry. We used the previously established threshold of 200 microm migration in the second postoperative year to distinguish two groups: a risk group of 15 patients and a stable group of 28 patients. We performed gait analysis before operation and at six months and at two years after TKA. On all three occasions we found significant differences between the two groups in the mean sagittal plane moments of the knee joint. The risk group walked with higher peak flexion moments than the stable group. The two groups were not discriminated by any clinical or radiological criteria or other gait characteristics. The relationship which we have found between gait with increased flexion moments and risk of tibial component loosening warrants further study as regards the aetiology of prosthetic loosening and possible methods of influencing its incidence.

Aged↗
PubMed1995

Fixation of the tibial component in knee arthroplasty after six weeks.

The fixation of cemented and uncemented PCA modular cruciform-stemmed tibial components was examined 6 weeks after operation using roentgenstereophotogrammetric analysis in 26 randomly selected patients. Physiological external forces were applied in external/internal rotation and eccentric posterior loading generated by squatting. All cases showed inducible displacement, but there were no statistically significant differences between the 2 groups in inducible displacement or in the initial migration, except for subsidence between the lying and standing position. In some, the greatest movement was found when changing from resting to standing, or during rotational stress; in others, the greatest movement was found during squatting. There was a statistical difference in subsidence on squatting which was greater in the uncemented group. The design of the cruciform stem and the use of an internally cooled saw may explain this small differences between the 2 groups.

Aged↗
PubMed1995

Mechanical influences on tissue differentiation at bone-cement interfaces.

Retrieval studies have shown that tissue at the bone-cement or bone-implant interface can develop into fibrous tissue, fibrocartilage, and bone, and that tissue differentiation appears to be mechanically influenced. A prior histologic analysis of retrieved interface tissues supporting cemented Marmor unicondylar knee components found that beneath the central portion of these implants, a thick, mature layer of fibrocartilage consistently developed, whereas fibrous tissue formed beneath the prosthesis periphery and adjacent to the bone beneath the tibial spine. Finite-element analysis was used to model the interface tissue supporting a cemented Marmor tibial component and interpreted patterns of stress and strain generated in the interface according to a mechanically based tissue differentiation theory. Distortional strain and hydrostatic stress, mechanical stimuli that are hypothesized to be associated with fibrous matrix and cartilaginous matrix production, respectively, were found to correlate well with the previous histologic findings. Given the biologic environments in which the retrieved interface tissues developed, frequently applied hydrostatic stress of approximately 0.7 MPa may be sufficient to stimulate cartilaginous extracellular matrix production in the interface tissue, and frequently applied distortional strain of 10% may be sufficient to stimulate fibrous extracellular matrix production.

Biomechanical Phenomena↗
PubMed1995

Subsidence of tibial components in knee arthroplasty. A comparison between conventional radiography and roentgen stereophotogrammetry.

RATIONALE AND OBJECTIVES: To assess the ability of conventional radiography to identify subsidence of tibial components. METHODS: Forty-three cases of knee arthroplasty were followed for 4 years using roentgen stereophotogrammetric analysis as the gold standard. RESULTS: Roentgen stereophotogrammetric analysis showed subsidence in all uncemented prostheses, whereas two thirds of the cemented prostheses subsided. Medially, the sensitivity of conventional radiography was low, 25%, whereas the specificity was 83%. For the other regions, the sensitivity was almost 100%, although the specificity was as low as 66% frontally and dorsally. CONCLUSIONS: Medially, where most prostheses were inserted with a slight overhang, conventional radiography identified subsidence correctly. Laterally, frontally, and dorsally, however, conventional radiography overestimated the subsidence by a factor of 2 to 3. This error was caused by bony protrusions arising in the cranial direction from the uncovered bone surfaces, thus changing the points of reference. This problem arose more commonly in uncemented cases, whereas cement seemed to seal the bone.

Biomechanical Phenomena↗
PubMed1995

Measuring hallux valgus: a comparison of conventional radiography and clinical parameters with regard to measurement accuracy.

To assess the repeatability and error of conventional x-ray measurements, intra- and interobserver evaluations of measurement accuracy were done on 20 preoperative and 40 postoperative (20 chevron and 20 proximal osteotomy) x-rays of hallux valgus patients. Standard x-rays showed an average interobserver error of measurement of 6.4 degrees for the hallux valgus angle, 5.4 degrees for the intermetatarsal angle, and 2.0 mm for the intermetatarsal distance. The intraobserver error did not differ greatly. The repeatability and error of two clinical measurements, ball circumference, and dorsal to plantar range of motion of the first metatarsophalangeal joint were evaluated for 20 healthy volunteers. The ball circumference had an average measurement error of 1.1 cm, whereas the dorsal and plantar range of motion of the great toe had an average measurement error of 12 degrees in dorsiflexion and 16 degrees in plantarflexion. In both clinical and radiographic parameters, linear measurements were more accurate than angular measurements. Although x-rays are of value in hallux valgus surgery, standard x-rays are less accurate than previously assumed. Small changes produced by osteotomies may be hidden by the postoperative measurement error. The results of hallux valgus surgery should primarily be evaluated clinically. When clinical and radiological evaluations are made, linear measurements may be preferable.

Female↗
PubMed1995

Measurement of the forefoot with roentgen stereophotogrammetry in hallux valgus surgery.

Eight hallux valgus patients were marked with tantalum markers in conjunction with hallux valgus surgery (seven proximal osteotomies and one chevron osteotomy). Changes on weightbearing before surgery as well as corrective changes after surgery were analyzed with roentgen stereophotogrammetry (RSA) and with standard x-rays. RSA is accurate to 0.6 degrees in rotational changes and 0.3 mm in translation. Weightbearing changes were inconsistent, and minimal with both standard x-rays and RSA. It was possible to analyze the correction at the osteotomy site with RSA. In half the cases, the correction measured by RSA corresponded with that measured with standard x-rays, within measurement error; in the other cases, RSA showed that the correction was of a different size or direction than that measured on standard x-rays. Corrective changes in hallux valgus surgery are complex, including angular and translational changes at several levels and in several joints in order to produce a clinical resultant. Rotational changes can be evaluated with RSA. Although RSA in an optimal situation is very accurate, it is still limited to a laboratory setting.

Female↗
PubMed1995

The stability of three different cementless tibial components. A randomized radiostereometric study in 45 knee arthroplasty patients.

We conducted a prospective, randomized study of 45 patients to evaluate 3 different uncemented tibial component designs in total knee arthroplasty. The stability of the components was assessed by radiostereometry (RSA), both as migration during 2 years and as inducible displacement at 2 years. The PCA resurfacing, the Tricon stem and the Tricon-M prosthesis groups showed a similar level of migration at 2 years, about 1.4 mm. In response to externally applied rotatory forces, the Tricon groups rotated more than the PCA group, interpreted as a consequence of the more conforming articular surface in the Tricon design. The series was divided into one group of continuously migrating prostheses with a poor prognosis (unstable, one third) and another group of prostheses in which migration stopped after 1 year (stable, two thirds). With this classification, no differences between the prostheses design groups were revealed. However, the unstable group showed a larger inducible displacement by provocation, an association hitherto not established.

Aged↗
PubMed1995

Circulating blood diminishes cement penetration into cancellous bone. In vivo studies of 21 arthrotic femoral heads.

We compared the penetration depth into cancellous bone when pressurizing cement at predetermined pressure levels, and at different times after cement mixing, in 21 arthrotic femoral heads during total hip replacement. To determine the influence of circulating blood on cement penetration, cement was injected into holes drilled into the femoral head before and after osteotomy of the femoral neck. The penetration of cement increased on the average 100 percent in the absence of circulation.

Aged↗
PubMed1995

A relationship between dynamic and static assessments of knee joint load. Gait analysis and radiography before and after knee replacement in 45 patients.

In a prospective study of 45 gonarthrosis patients treated with total knee arthroplasty, we performed gait analysis with the Vifor system preoperatively and 6 months and 2 years postoperatively. An evaluation was made of the relationship between dynamic measurements of knee joint load and static, radiographic measurements of alignment. Correlations were found between the knee joint moments in the frontal plane and the Hip-Knee-Ankle (HKA) angles on all measurement occasions, likewise between changes of moments and changes in HKA by the operation. Thus, static alignment reflects the loading conditions during gait.

Aged↗